]> git.saurik.com Git - apple/xnu.git/blobdiff - bsd/netinet/tcp_input.c
xnu-1699.24.8.tar.gz
[apple/xnu.git] / bsd / netinet / tcp_input.c
index 624b3451fb11a2f2758c826af620cec5680e2a76..6f06b2b1478871a4edecb4c1f92ec1f92b643f7c 100644 (file)
@@ -1,23 +1,29 @@
 /*
- * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
+ * Copyright (c) 2000-2011 Apple Inc. All rights reserved.
  *
- * @APPLE_LICENSE_HEADER_START@
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
  * 
- * The contents of this file constitute Original Code as defined in and
- * are subject to the Apple Public Source License Version 1.1 (the
- * "License").  You may not use this file except in compliance with the
- * License.  Please obtain a copy of the License at
- * http://www.apple.com/publicsource and read it before using this file.
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. The rights granted to you under the License
+ * may not be used to create, or enable the creation or redistribution of,
+ * unlawful or unlicensed copies of an Apple operating system, or to
+ * circumvent, violate, or enable the circumvention or violation of, any
+ * terms of an Apple operating system software license agreement.
  * 
- * This Original Code and all software distributed under the License are
- * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this file.
+ * 
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
- * License for the specific language governing rights and limitations
- * under the License.
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
  * 
- * @APPLE_LICENSE_HEADER_END@
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  */
 /*
  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
  *     @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
  * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.16 2001/08/22 00:59:12 silby Exp $
  */
-
+/*
+ * NOTICE: This file was modified by SPARTA, Inc. in 2005 to introduce
+ * support for mandatory and extensible security protections.  This notice
+ * is included in support of clause 2.2 (b) of the Apple Public License,
+ * Version 2.0.
+ */
 
 #include <sys/param.h>
 #include <sys/systm.h>
 
 #include <kern/cpu_number.h>   /* before tcp_seq.h, for tcp_random18() */
 
+#include <machine/endian.h>
+
 #include <net/if.h>
 #include <net/if_types.h>
 #include <net/route.h>
+#include <net/ntstat.h>
 
 #include <netinet/in.h>
 #include <netinet/in_systm.h>
@@ -82,6 +96,7 @@
 #include <netinet/icmp_var.h>  /* for ICMP_BANDLIM     */
 #include <netinet/in_pcb.h>
 #include <netinet/ip_var.h>
+#include <mach/sdt.h>
 #if INET6
 #include <netinet/ip6.h>
 #include <netinet/icmp6.h>
 #include <netinet/tcp_seq.h>
 #include <netinet/tcp_timer.h>
 #include <netinet/tcp_var.h>
+#include <netinet/tcp_cc.h>
+#include <kern/zalloc.h>
 #if INET6
 #include <netinet6/tcp6_var.h>
 #endif
@@ -112,91 +129,141 @@ struct tcphdr tcp_savetcp;
 #include <netkey/key.h>
 #endif /*IPSEC*/
 
-#include <sys/kdebug.h>
+#if CONFIG_MACF_NET || CONFIG_MACF_SOCKET
+#include <security/mac_framework.h>
+#endif /* CONFIG_MACF_NET || CONFIG_MACF_SOCKET */
 
-#ifndef __APPLE__
-MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry");
-#endif
+#include <sys/kdebug.h>
 
 #define DBG_LAYER_BEG          NETDBG_CODE(DBG_NETTCP, 0)
 #define DBG_LAYER_END          NETDBG_CODE(DBG_NETTCP, 2)
 #define DBG_FNC_TCP_INPUT       NETDBG_CODE(DBG_NETTCP, (3 << 8))
 #define DBG_FNC_TCP_NEWCONN     NETDBG_CODE(DBG_NETTCP, (7 << 8))
 
-static int     tcprexmtthresh = 3;
+static int     tcprexmtthresh = 2;
 tcp_cc tcp_ccgen;
-extern int apple_hwcksum_rx;
 
 #if IPSEC
 extern int ipsec_bypass;
-extern lck_mtx_t *sadb_mutex;
 #endif
 
 struct tcpstat tcpstat;
-SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RD, 
-    &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
 
 static int log_in_vain = 0;
-SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW | CTLFLAG_LOCKED,
     &log_in_vain, 0, "Log all incoming TCP connections");
 
 static int blackhole = 0;
-SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW | CTLFLAG_LOCKED,
        &blackhole, 0, "Do not send RST when dropping refused connections");
 
 int tcp_delack_enabled = 3;
-SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW | CTLFLAG_LOCKED,
     &tcp_delack_enabled, 0, 
     "Delay ACK to try and piggyback it onto a data packet");
 
 int tcp_lq_overflow = 1;
-SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcp_lq_overflow, CTLFLAG_RW,
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcp_lq_overflow, CTLFLAG_RW | CTLFLAG_LOCKED,
     &tcp_lq_overflow, 0, 
     "Listen Queue Overflow");
 
+int tcp_recv_bg = 0;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbg, CTLFLAG_RW | CTLFLAG_LOCKED,
+    &tcp_recv_bg, 0, 
+    "Receive background");
+
 #if TCP_DROP_SYNFIN
 static int drop_synfin = 1;
-SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW | CTLFLAG_LOCKED,
     &drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
 #endif
 
-SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
+SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW|CTLFLAG_LOCKED, 0,
     "TCP Segment Reassembly Queue");
 
 __private_extern__ int tcp_reass_maxseg = 0;
-SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RW,
+SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RW | CTLFLAG_LOCKED,
     &tcp_reass_maxseg, 0,
     "Global maximum number of TCP Segments in Reassembly Queue");
 
 __private_extern__ int tcp_reass_qsize = 0;
-SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
+SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD | CTLFLAG_LOCKED,
     &tcp_reass_qsize, 0,
     "Global number of TCP Segments currently in Reassembly Queue");
 
 static int tcp_reass_overflows = 0;
-SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
+SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD | CTLFLAG_LOCKED,
     &tcp_reass_overflows, 0,
     "Global number of TCP Segment Reassembly Queue Overflows");
 
 
 __private_extern__ int slowlink_wsize = 8192;
-SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowlink_wsize, CTLFLAG_RW,
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowlink_wsize, CTLFLAG_RW | CTLFLAG_LOCKED,
        &slowlink_wsize, 0, "Maximum advertised window size for slowlink");
 
+int maxseg_unacked = 8;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, maxseg_unacked, CTLFLAG_RW | CTLFLAG_LOCKED,
+       &maxseg_unacked, 0, "Maximum number of outstanding segments left unacked");
+
+int    tcp_do_rfc3465 = 1;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_RW | CTLFLAG_LOCKED,
+       &tcp_do_rfc3465, 0, "");
+
+int    tcp_do_rfc3465_lim2 = 1;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465_lim2, CTLFLAG_RW | CTLFLAG_LOCKED,
+       &tcp_do_rfc3465_lim2, 0, "Appropriate bytes counting w/ L=2*SMSS");
+
+int    rtt_samples_per_slot = 20;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, rtt_samples_per_slot, CTLFLAG_RW | CTLFLAG_LOCKED,
+       &rtt_samples_per_slot, 0, "Number of RTT samples stored for rtt history");
+
+int    tcp_allowed_iaj = ALLOWED_IAJ;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, recv_allowed_iaj, CTLFLAG_RW | CTLFLAG_LOCKED,
+        &tcp_allowed_iaj, 0, "Allowed inter-packet arrival jiter");
+
+int    tcp_acc_iaj_high_thresh = ACC_IAJ_HIGH_THRESH;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, acc_iaj_high_thresh, CTLFLAG_RW | CTLFLAG_LOCKED,
+        &tcp_acc_iaj_high_thresh, 0, "Used in calculating maximum accumulated IAJ");
+
+#if CONFIG_IFEF_NOWINDOWSCALE
+int tcp_obey_ifef_nowindowscale = 0;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, obey_ifef_nowindowscale, CTLFLAG_RW | CTLFLAG_LOCKED,
+       &tcp_obey_ifef_nowindowscale, 0, "");
+#endif
+
+extern int tcp_TCPTV_MIN;
+extern int tcp_acc_iaj_high;
+extern int tcp_acc_iaj_react_limit;
+extern struct zone *tcp_reass_zone;
+
+
+u_int32_t tcp_now;
+struct timeval tcp_uptime;     /* uptime when tcp_now was last updated */
+lck_spin_t *tcp_uptime_lock;   /* Used to sychronize updates to tcp_now */
 
-u_long tcp_now;
 struct inpcbhead tcb;
 #define        tcb6    tcb  /* for KAME src sync over BSD*'s */
 struct inpcbinfo tcbinfo;
 
-static void     tcp_dooptions(struct tcpcb *,
-           u_char *, int, struct tcphdr *, struct tcpopt *);
+static void tcp_dooptions(struct tcpcb *, u_char *, int, struct tcphdr *,
+    struct tcpopt *, unsigned int);
 static void     tcp_pulloutofband(struct socket *,
            struct tcphdr *, struct mbuf *, int);
 static int      tcp_reass(struct tcpcb *, struct tcphdr *, int *,
                                struct mbuf *);
 static void    tcp_xmit_timer(struct tcpcb *, int);
-static int     tcp_newreno __P((struct tcpcb *, struct tcphdr *));
+static inline unsigned int tcp_maxmtu(struct rtentry *);
+static inline int tcp_stretch_ack_enable(struct tcpcb *tp);
+
+#if TRAFFIC_MGT
+static inline void update_iaj_state(struct tcpcb *tp, uint32_t tlen, int reset_size);
+void compute_iaj(struct tcpcb *tp);
+static inline void clear_iaj_state(struct tcpcb *tp);
+#endif /* TRAFFIC_MGT */
+
+#if INET6
+static inline unsigned int tcp_maxmtu6(struct rtentry *);
+#endif
 
 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
 #if INET6
@@ -211,46 +278,160 @@ do { \
 #define ND6_HINT(tp)
 #endif
 
-extern u_long  *delack_bitmask;
+extern void    add_to_time_wait(struct tcpcb *, uint32_t delay);
+extern void postevent(struct socket *, struct sockbuf *, int);
 
-extern  void    ipfwsyslog( int level, char *format,...);
+extern  void    ipfwsyslog( int level, const char *format,...);
 extern int ChkAddressOK( __uint32_t dstaddr, __uint32_t srcaddr );
 extern int fw_verbose;
+__private_extern__ int tcp_sockthreshold;
+__private_extern__ int tcp_win_scale;
 
+#if IPFIREWALL
 #define log_in_vain_log( a ) {            \
         if ( (log_in_vain == 3 ) && (fw_verbose == 2)) {        /* Apple logging, log to ipfw.log */ \
                 ipfwsyslog a ;  \
         }                       \
         else log a ;            \
 }
+#else
+#define log_in_vain_log( a ) { log a; }
+#endif
 
-/*
- * Indicate whether this ack should be delayed.  
- * We can delay the ack if:
- *  - delayed acks are enabled (set to 1) and
- *      - our last ack wasn't a 0-sized window.  We never want to delay
- *       the ack that opens up a 0-sized window.
- *  - delayed acks are enabled (set to 2, "more compatible") and
- *      - our last ack wasn't a 0-sized window.
- *      - if the peer hasn't sent us a TH_PUSH data packet (this solves 3649245)
- *      - the peer hasn't sent us a TH_PUSH data packet, if he did, take this as a clue that we
- *        need to ACK with no delay. This helps higher level protocols who won't send
- *        us more data even if the window is open because their last "segment" hasn't been ACKed
- *  - delayed acks are enabled (set to 3, "streaming detection") and
- *     - if we receive more than 4 full packets per second on this socket, we're streaming acts as "1".
- *     - if we don't meet that criteria, acts like "2". Allowing faster acking while browsing for example.
- *
+int tcp_rcvunackwin = TCPTV_UNACKWIN;
+int tcp_maxrcvidle = TCPTV_MAXRCVIDLE;
+int tcp_rcvsspktcnt = TCP_RCV_SS_PKTCOUNT;
+
+#define DELAY_ACK(tp, th) (CC_ALGO(tp)->delay_ack != NULL && CC_ALGO(tp)->delay_ack(tp, th))
+
+static int tcp_dropdropablreq(struct socket *head);
+static void tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th);
+
+static void update_base_rtt(struct tcpcb *tp, uint32_t rtt);
+uint32_t get_base_rtt(struct tcpcb *tp);
+void tcp_set_background_cc(struct socket *so);
+void tcp_set_foreground_cc(struct socket *so);
+static void tcp_set_new_cc(struct socket *so, uint16_t cc_index);
+
+#if TRAFFIC_MGT
+void
+reset_acc_iaj(struct tcpcb *tp)
+{
+       tp->acc_iaj = 0;
+       tp->iaj_rwintop = 0;
+       clear_iaj_state(tp);
+}
+
+static inline void
+update_iaj_state(struct tcpcb *tp, uint32_t size, int rst_size)
+{
+       if (rst_size > 0)
+               tp->iaj_size = 0;
+       if (tp->iaj_size == 0 || size >= tp->iaj_size) {
+               tp->iaj_size = size;
+               tp->iaj_rcv_ts = tcp_now;
+               tp->iaj_small_pkt = 0;
+       }
+}
+
+static inline void
+clear_iaj_state(struct tcpcb *tp)
+{
+       tp->iaj_rcv_ts = 0;
+}
+
+/* For every 32 bit unsigned integer(v), this function will find the 
+ * largest integer n such that (n*n <= v). This takes at most 16 iterations 
+ * irrespective of the value of v and does not involve multiplications. 
  */
-#define DELAY_ACK(tp) \
-       (((tcp_delack_enabled == 1) && ((tp->t_flags & TF_RXWIN0SENT) == 0)) || \
-        (((tcp_delack_enabled == 2) && (tp->t_flags & TF_RXWIN0SENT) == 0) && \
-          ((thflags & TH_PUSH) == 0) && ((tp->t_flags & TF_DELACK) == 0)) || \
-        (((tcp_delack_enabled == 3) && (tp->t_flags & TF_RXWIN0SENT) == 0) && \
-          (((tp->t_rcvtime == 0) && (tp->rcv_byps > (4* tp->t_maxseg)))  || (((thflags & TH_PUSH) == 0) && ((tp->t_flags & TF_DELACK) == 0)))))
+static inline int
+isqrt(unsigned int val) {
+       unsigned int sqrt_cache[11] = {0, 1, 4, 9, 16, 25, 36, 49, 64, 81, 100};
+       unsigned int temp, g=0, b=0x8000, bshft=15;
+       if ( val <= 100) {
+               for (g = 0; g <= 10; ++g) {
+                       if (sqrt_cache[g] > val) {
+                               g--;
+                               break;
+                       } else if (sqrt_cache[g] == val) {
+                               break;
+                       }
+               }
+       } else {
+               do {
+                       temp = (((g << 1) + b) << (bshft--));
+                       if (val >= temp) {
+                               g += b;
+                               val -= temp;
+                       }
+                       b >>= 1;
+               } while ( b > 0 && val > 0);
+       }
+       return(g);
+} 
+
+void
+compute_iaj(struct tcpcb *tp)
+{
+       /* When accumulated IAJ reaches MAX_ACC_IAJ in milliseconds, throttle the
+        * receive window to a minimum of MIN_IAJ_WIN packets
+        */
+#define MAX_ACC_IAJ (tcp_acc_iaj_high_thresh + tcp_acc_iaj_react_limit)
+
+       uint32_t allowed_iaj, acc_iaj = 0;
+       uint32_t cur_iaj = tcp_now - tp->iaj_rcv_ts;
+
+       uint32_t mean, temp;
+       int32_t cur_iaj_dev;
+       cur_iaj_dev = (cur_iaj - tp->avg_iaj);  
+       
+       /* Allow a jitter of "allowed_iaj" milliseconds. Some connections may have a
+        * constant jitter more than that. We detect this by using
+        * standard deviation.
+        */
+       allowed_iaj = tp->avg_iaj + tp->std_dev_iaj;
+       if (allowed_iaj < tcp_allowed_iaj)
+               allowed_iaj = tcp_allowed_iaj;
+
+       /* Initially when the connection starts, the senders congestion window 
+        * is small. During this period we avoid throttling a connection because
+        * we do not have a good starting point for allowed_iaj. IAJ_IGNORE_PKTCNT
+        * is used to quietly gloss over the first few packets.
+        */
+       if (tp->iaj_pktcnt > IAJ_IGNORE_PKTCNT) {
+               if ( cur_iaj <= allowed_iaj ) {
+                       if (tp->acc_iaj >= 2)
+                               acc_iaj = tp->acc_iaj - 2;
+                       else
+                               acc_iaj = 0;
+               } else {
+                       acc_iaj = tp->acc_iaj + (cur_iaj - allowed_iaj);
+               }
+
+               if (acc_iaj > MAX_ACC_IAJ)
+                       acc_iaj = MAX_ACC_IAJ;
+               tp->acc_iaj = acc_iaj;
+       }
+
+       /* Compute weighted average where the history has a weight of
+        * 15 out of 16 and the current value has a weight of 1 out of 16. 
+        * This will make the short-term measurements have more weight.
+        */
+       tp->avg_iaj = (((tp->avg_iaj << 4) - tp->avg_iaj) + cur_iaj) >> 4;
 
+       /* Compute Root-mean-square of deviation where mean is a weighted
+        * average as described above
+        */
+       temp = tp->std_dev_iaj * tp->std_dev_iaj;
+       mean = (((temp << 4) - temp) + (cur_iaj_dev * cur_iaj_dev)) >> 4;
+       
+       tp->std_dev_iaj = isqrt(mean);
 
-static int tcpdropdropablreq(struct socket *head);
+       DTRACE_TCP3(iaj, struct tcpcb *, tp, uint32_t, cur_iaj, uint32_t, allowed_iaj);
 
+       return;
+}
+#endif /* TRAFFIC_MGT */
 
 static int
 tcp_reass(tp, th, tlenp, m)
@@ -262,7 +443,7 @@ tcp_reass(tp, th, tlenp, m)
        struct tseg_qent *q;
        struct tseg_qent *p = NULL;
        struct tseg_qent *nq;
-       struct tseg_qent *te;
+       struct tseg_qent *te = NULL;
        struct socket *so = tp->t_inpcb->inp_socket;
        int flags;
        int dowakeup = 0;
@@ -271,8 +452,29 @@ tcp_reass(tp, th, tlenp, m)
         * Call with th==0 after become established to
         * force pre-ESTABLISHED data up to user socket.
         */
-       if (th == 0)
+       if (th == NULL)
                goto present;
+       
+       /* If the reassembly queue already has entries or if we are going to add 
+        * a new one, then the connection has reached a loss state. 
+        * Reset the stretch-ack algorithm at this point.
+        */
+       if ((tp->t_flags & TF_STRETCHACK) != 0)
+               tcp_reset_stretch_ack(tp);
+
+       /* When the connection reaches a loss state, we need to send more acks
+        * for a period of time so that the sender's congestion window will
+        * open. Wait until we see some packets on the connection before 
+        * stretching acks again.
+        */
+       tp->t_flagsext |= TF_RCVUNACK_WAITSS;
+       tp->rcv_waitforss = 0;
+
+
+#if TRAFFIC_MGT
+       if (tp->acc_iaj > 0)
+               reset_acc_iaj(tp);
+#endif /* TRAFFIC_MGT */       
 
        /*
         * Limit the number of segments in the reassembly queue to prevent
@@ -286,12 +488,12 @@ tcp_reass(tp, th, tlenp, m)
                tcp_reass_overflows++;
                tcpstat.tcps_rcvmemdrop++;
                m_freem(m);
+               *tlenp = 0;
                return (0);
        }
 
        /* Allocate a new queue entry. If we can't, just drop the pkt. XXX */
-       MALLOC(te, struct tseg_qent *, sizeof (struct tseg_qent), M_TSEGQ,
-              M_NOWAIT);
+       te = (struct tseg_qent *) zalloc_noblock(tcp_reass_zone);
        if (te == NULL) {
                tcpstat.tcps_rcvmemdrop++;
                m_freem(m);
@@ -321,8 +523,14 @@ tcp_reass(tp, th, tlenp, m)
                        if (i >= *tlenp) {
                                tcpstat.tcps_rcvduppack++;
                                tcpstat.tcps_rcvdupbyte += *tlenp;
+                               if (nstat_collect) {
+                                       nstat_route_rx(tp->t_inpcb->inp_route.ro_rt, 1, *tlenp, NSTAT_RX_FLAG_DUPLICATE);
+                                       locked_add_64(&tp->t_inpcb->inp_stat->rxpackets, 1);
+                                       locked_add_64(&tp->t_inpcb->inp_stat->rxbytes, *tlenp);
+                                       tp->t_stat.rxduplicatebytes += *tlenp;
+                               }
                                m_freem(m);
-                               FREE(te, M_TSEGQ);
+                               zfree(tcp_reass_zone, te);
                                tcp_reass_qsize--;
                                /*
                                 * Try to present any queued data
@@ -339,6 +547,12 @@ tcp_reass(tp, th, tlenp, m)
        }
        tcpstat.tcps_rcvoopack++;
        tcpstat.tcps_rcvoobyte += *tlenp;
+       if (nstat_collect) {
+               nstat_route_rx(tp->t_inpcb->inp_route.ro_rt, 1, *tlenp, NSTAT_RX_FLAG_OUT_OF_ORDER);
+               locked_add_64(&tp->t_inpcb->inp_stat->rxpackets, 1);
+               locked_add_64(&tp->t_inpcb->inp_stat->rxbytes, *tlenp);
+               tp->t_stat.rxoutoforderbytes += *tlenp;
+       }
 
        /*
         * While we overlap succeeding segments trim them or,
@@ -358,7 +572,7 @@ tcp_reass(tp, th, tlenp, m)
                nq = LIST_NEXT(q, tqe_q);
                LIST_REMOVE(q, tqe_q);
                m_freem(q->tqe_m);
-               FREE(q, M_TSEGQ);
+               zfree(tcp_reass_zone, q);
                tcp_reass_qsize--;
                q = nq;
        }
@@ -392,10 +606,11 @@ present:
                if (so->so_state & SS_CANTRCVMORE)
                        m_freem(q->tqe_m);
                else {
-                       if (sbappend(&so->so_rcv, q->tqe_m))
+                       so_recv_data_stat(so, q->tqe_m, 0); /* XXXX */
+                       if (sbappendstream(&so->so_rcv, q->tqe_m))
                                dowakeup = 1;
                }
-               FREE(q, M_TSEGQ);
+               zfree(tcp_reass_zone, q);
                tcp_reass_qsize--;
                q = nq;
        } while (q && q->tqe_th->th_seq == tp->rcv_nxt);
@@ -425,6 +640,29 @@ present:
 
 }
 
+/*
+ * Reduce congestion window.
+ */
+static void
+tcp_reduce_congestion_window(
+       struct tcpcb    *tp, struct tcphdr *th)
+{
+       /*
+        * If the current tcp cc module has
+        * defined a hook for tasks to run
+        * before entering FR, call it
+        */
+       if (CC_ALGO(tp)->pre_fr != NULL)
+               CC_ALGO(tp)->pre_fr(tp, th);
+       ENTER_FASTRECOVERY(tp);
+       tp->snd_recover = tp->snd_max;
+       tp->t_timer[TCPT_REXMT] = 0;
+       tp->t_rtttime = 0;
+       tp->ecn_flags |= TE_SENDCWR;
+       tp->snd_cwnd = tp->snd_ssthresh +
+                tp->t_maxseg * tcprexmtthresh;
+}
+
 
 /*
  * TCP input routine, follows pages 65-76 of the
@@ -432,10 +670,9 @@ present:
  */
 #if INET6
 int
-tcp6_input(mp, offp)
-       struct mbuf **mp;
-       int *offp;
+tcp6_input(struct mbuf **mp, int *offp, int proto)
 {
+#pragma unused(proto)
        register struct mbuf *m = *mp;
        struct in6_ifaddr *ia6;
 
@@ -446,20 +683,71 @@ tcp6_input(mp, offp)
         * better place to put this in?
         */
        ia6 = ip6_getdstifaddr(m);
-       if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {                
-               struct ip6_hdr *ip6;
+       if (ia6 != NULL) {
+               IFA_LOCK_SPIN(&ia6->ia_ifa);
+               if (ia6->ia6_flags & IN6_IFF_ANYCAST) {
+                       struct ip6_hdr *ip6;
 
-               ip6 = mtod(m, struct ip6_hdr *);
-               icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
+                       IFA_UNLOCK(&ia6->ia_ifa);
+                       IFA_REMREF(&ia6->ia_ifa);
+                       ip6 = mtod(m, struct ip6_hdr *);
+                       icmp6_error(m, ICMP6_DST_UNREACH,
+                           ICMP6_DST_UNREACH_ADDR,
                            (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
-               return IPPROTO_DONE;
+                       return (IPPROTO_DONE);
+               }
+               IFA_UNLOCK(&ia6->ia_ifa);
+               IFA_REMREF(&ia6->ia_ifa);
        }
 
        tcp_input(m, *offp);
-       return IPPROTO_DONE;
+       return (IPPROTO_DONE);
 }
 #endif
 
+/* A receiver will evaluate the flow of packets on a connection 
+ * to see if it can reduce ack traffic. The receiver will start 
+ * stretching acks if all of the following conditions are met:
+ * 1. tcp_delack_enabled is set to 3
+ * 2. If the bytes received in the last 100ms is greater than a threshold
+ *      defined by maxseg_unacked
+ * 3. If the connection has not been idle for tcp_maxrcvidle period.
+ * 4. If the connection has seen enough packets to let the slow-start 
+ *      finish after connection establishment or after some packet loss.
+ *
+ * The receiver will stop stretching acks if there is congestion/reordering
+ * as indicated by packets on reassembly queue or an ECN. If the delayed-ack 
+ * timer fires while stretching acks, it means that the packet flow has gone 
+ * below the threshold defined by maxseg_unacked and the receiver will stop
+ * stretching acks. The receiver gets no indication when slow-start is completed 
+ * or when the connection reaches an idle state. That is why we use 
+ * tcp_rcvsspktcnt to cover slow-start and tcp_maxrcvidle to identify idle 
+ * state.
+ */
+ static inline int
+ tcp_stretch_ack_enable(struct tcpcb *tp) {
+       if (tp->rcv_by_unackwin >= (maxseg_unacked * tp->t_maxseg) &&
+               TSTMP_GT(tp->rcv_unackwin + tcp_maxrcvidle, tcp_now) &&
+               (((tp->t_flagsext & TF_RCVUNACK_WAITSS) == 0) ||
+               (tp->rcv_waitforss >= tcp_rcvsspktcnt))) {
+               return(1);
+       }
+       return(0);
+}
+
+/* Reset the state related to stretch-ack algorithm. This will make
+ * the receiver generate an ack every other packet. The receiver
+ * will start re-evaluating the rate at which packets come to decide 
+ * if it can benefit by lowering the ack traffic.
+ */
+void
+tcp_reset_stretch_ack(struct tcpcb *tp)
+{
+       tp->t_flags &= ~(TF_STRETCHACK);
+       tp->rcv_by_unackwin = 0;
+       tp->rcv_unackwin = tcp_now + tcp_rcvunackwin;
+}
+
 void
 tcp_input(m, off0)
        struct mbuf *m;
@@ -484,18 +772,41 @@ tcp_input(m, off0)
        int dropsocket = 0;
        int iss = 0;
        int nosock = 0;
-       u_long tiwin;
+       u_int32_t tiwin;
        struct tcpopt to;               /* options in this segment */
-       struct rmxp_tao *taop;          /* pointer to our TAO cache entry */
-       struct rmxp_tao tao_noncached;  /* in case there's no cached entry */
        struct sockaddr_in *next_hop = NULL;
 #if TCPDEBUG
        short ostate = 0;
 #endif
        struct m_tag *fwd_tag;
+       u_char ip_ecn = IPTOS_ECN_NOTECT;
+       unsigned int ifscope, nocell = 0;
+       uint8_t isconnected, isdisconnected;
+
+       /*
+        * Record the interface where this segment arrived on; this does not
+        * affect normal data output (for non-detached TCP) as it provides a
+        * hint about which route and interface to use for sending in the
+        * absence of a PCB, when scoped routing (and thus source interface
+        * selection) are enabled.
+        */
+       if ((m->m_flags & M_PKTHDR) && m->m_pkthdr.rcvif != NULL)
+               ifscope = m->m_pkthdr.rcvif->if_index;
+       else
+               ifscope = IFSCOPE_NONE;
+
+        /* Since this is an entry point for input processing of tcp packets, we
+         * can update the tcp clock here.
+         */
+        calculate_tcp_clock();
 
        /* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */
-       fwd_tag = m_tag_locate(m, KERNEL_MODULE_TAG_ID, KERNEL_TAG_TYPE_IPFORWARD, NULL);
+       if (!SLIST_EMPTY(&m->m_pkthdr.tags)) {
+               fwd_tag = m_tag_locate(m, KERNEL_MODULE_TAG_ID,
+                   KERNEL_TAG_TYPE_IPFORWARD, NULL);
+       } else {
+               fwd_tag = NULL;
+       }
        if (fwd_tag != NULL) {
                struct ip_fwd_tag *ipfwd_tag = (struct ip_fwd_tag *)(fwd_tag+1);
                
@@ -526,12 +837,29 @@ tcp_input(m, off0)
                /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
                ip6 = mtod(m, struct ip6_hdr *);
                tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
-               if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
-                       tcpstat.tcps_rcvbadsum++;
-                       goto dropnosock;
-               }
                th = (struct tcphdr *)((caddr_t)ip6 + off0);
 
+               if ((apple_hwcksum_rx != 0) && (m->m_pkthdr.csum_flags & CSUM_DATA_VALID)) {
+                       if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
+                               th->th_sum = m->m_pkthdr.csum_data;
+                       else
+                               th->th_sum = in6_cksum_phdr(&ip6->ip6_src,
+                                       &ip6->ip6_dst, htonl(sizeof(struct tcphdr)),
+                                       htonl(IPPROTO_TCP));
+
+                       th->th_sum ^= 0xffff;
+                       if (th->th_sum) {
+                               tcpstat.tcps_rcvbadsum++;
+                               goto dropnosock;
+                       }
+               }
+               else {
+                       if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
+                               tcpstat.tcps_rcvbadsum++;
+                               goto dropnosock;
+                       }
+               }
+
                KERNEL_DEBUG(DBG_LAYER_BEG, ((th->th_dport << 16) | th->th_sport),
                     (((ip6->ip6_src.s6_addr16[0]) << 16) | (ip6->ip6_dst.s6_addr16[0])),
                     th->th_seq, th->th_ack, th->th_win);
@@ -547,6 +875,11 @@ tcp_input(m, off0)
                        /* XXX stat */
                        goto dropnosock;
                }
+               DTRACE_TCP5(receive, sruct mbuf *, m, struct inpcb *, NULL,
+                       struct ip6_hdr *, ip6, struct tcpcb *, NULL, 
+                       struct tcphdr *, th);
+        
+       ip_ecn = (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
        } else
 #endif /* INET6 */
        {
@@ -572,12 +905,15 @@ tcp_input(m, off0)
        th = (struct tcphdr *)((caddr_t)ip + off0);
        tlen = ip->ip_len;
 
+       DTRACE_TCP5(receive, struct mbuf *, m, struct inpcb *, NULL,
+               struct ip *, ip, struct tcpcb *, NULL, struct tcphdr *, th);
+
        KERNEL_DEBUG(DBG_LAYER_BEG, ((th->th_dport << 16) | th->th_sport),
                     (((ip->ip_src.s_addr & 0xffff) << 16) | (ip->ip_dst.s_addr & 0xffff)),
                     th->th_seq, th->th_ack, th->th_win);
 
        if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
-               if (apple_hwcksum_rx && (m->m_pkthdr.csum_flags & CSUM_TCP_SUM16)) {
+               if (m->m_pkthdr.csum_flags & CSUM_TCP_SUM16) {
                        u_short pseudo;
                        char b[9];
                        *(uint32_t*)&b[0] = *(uint32_t*)&ipov->ih_x1[0];
@@ -586,7 +922,11 @@ tcp_input(m, off0)
                        
                        bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
                        ipov->ih_len = (u_short)tlen;
+
+#if BYTE_ORDER != BIG_ENDIAN
                        HTONS(ipov->ih_len);
+#endif
+
                        pseudo = in_cksum(m, sizeof (struct ip));
                        
                        *(uint32_t*)&ipov->ih_x1[0] = *(uint32_t*)&b[0];
@@ -615,12 +955,18 @@ tcp_input(m, off0)
                len = sizeof (struct ip) + tlen;
                bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
                ipov->ih_len = (u_short)tlen;
+
+#if BYTE_ORDER != BIG_ENDIAN
                HTONS(ipov->ih_len);
+#endif
+
                th->th_sum = in_cksum(m, len);
                
                *(uint32_t*)&ipov->ih_x1[0] = *(uint32_t*)&b[0];
                *(uint32_t*)&ipov->ih_x1[4] = *(uint32_t*)&b[4];
                *(uint8_t*)&ipov->ih_x1[8] = *(uint8_t*)&b[8];
+
+               tcp_in_cksum_stats(len);
        }
        if (th->th_sum) {
                tcpstat.tcps_rcvbadsum++;
@@ -630,6 +976,7 @@ tcp_input(m, off0)
        /* Re-initialization for later version check */
        ip->ip_v = IPVERSION;
 #endif
+       ip_ecn = (ip->ip_tos & IPTOS_ECN_MASK);
        }
 
        /*
@@ -650,17 +997,17 @@ tcp_input(m, off0)
                        th = (struct tcphdr *)((caddr_t)ip6 + off0);
                } else
 #endif /* INET6 */
-             {
-               if (m->m_len < sizeof(struct ip) + off) {
-                       if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) {
-                               tcpstat.tcps_rcvshort++;
-                               return;
+               {
+                       if (m->m_len < sizeof(struct ip) + off) {
+                               if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) {
+                                       tcpstat.tcps_rcvshort++;
+                                       return;
+                               }
+                               ip = mtod(m, struct ip *);
+                               ipov = (struct ipovly *)ip;
+                               th = (struct tcphdr *)((caddr_t)ip + off0);
                        }
-                       ip = mtod(m, struct ip *);
-                       ipov = (struct ipovly *)ip;
-                       th = (struct tcphdr *)((caddr_t)ip + off0);
                }
-             }
                optlen = off - sizeof (struct tcphdr);
                optp = (u_char *)(th + 1);
                /* 
@@ -671,11 +1018,11 @@ tcp_input(m, off0)
                 * tcp_dooptions(), etc.
                 */
                if ((optlen == TCPOLEN_TSTAMP_APPA ||
-                    (optlen > TCPOLEN_TSTAMP_APPA &&
+                       (optlen > TCPOLEN_TSTAMP_APPA &&
                        optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) &&
-                    *(u_int32_t *)optp == htonl(TCPOPT_TSTAMP_HDR) &&
-                    (th->th_flags & TH_SYN) == 0) {
-                       to.to_flag |= TOF_TS;
+                       *(u_int32_t *)optp == htonl(TCPOPT_TSTAMP_HDR) &&
+                       (th->th_flags & TH_SYN) == 0) {
+                       to.to_flags |= TOF_TS;
                        to.to_tsval = ntohl(*(u_int32_t *)(optp + 4));
                        to.to_tsecr = ntohl(*(u_int32_t *)(optp + 8));
                        optp = NULL;    /* we've parsed the options */
@@ -689,7 +1036,7 @@ tcp_input(m, off0)
         * both the SYN and FIN bits set. This prevents e.g. nmap from
         * identifying the TCP/IP stack.
         *
-        * This is incompatible with RFC1644 extensions (T/TCP).
+        * This is a violation of the TCP specification.
         */
        if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN))
                goto dropnosock;
@@ -698,13 +1045,16 @@ tcp_input(m, off0)
        /*
         * Convert TCP protocol specific fields to host format.
         */
+
+#if BYTE_ORDER != BIG_ENDIAN
        NTOHL(th->th_seq);
        NTOHL(th->th_ack);
        NTOHS(th->th_win);
        NTOHS(th->th_urp);
+#endif
 
        /*
-        * Delay droping TCP, IP headers, IPv6 ext headers, and TCP options,
+        * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options,
         * until after ip6_savecontrol() is called and before other functions
         * which don't want those proto headers.
         * Because ip6_savecontrol() is going to parse the mbuf to
@@ -717,10 +1067,14 @@ tcp_input(m, off0)
         * Locate pcb for segment.
         */
 findpcb:
+
+       isconnected = FALSE;
+       isdisconnected = FALSE;
+
 #if IPFIREWALL_FORWARD
        if (next_hop != NULL
 #if INET6
-           && isipv6 == NULL /* IPv6 support is not yet */
+           && isipv6 == 0 /* IPv6 support is not yet */
 #endif /* INET6 */
            ) {
                /*
@@ -759,24 +1113,39 @@ findpcb:
            ip->ip_dst, th->th_dport, 1, m->m_pkthdr.rcvif);
       }
 
+       /*
+        * Use the interface scope information from the PCB for outbound
+        * segments.  If the PCB isn't present and if scoped routing is
+        * enabled, tcp_respond will use the scope of the interface where
+        * the segment arrived on.
+        */
+       if (inp != NULL && (inp->inp_flags & INP_BOUND_IF))
+               ifscope = inp->inp_boundif;
+       /*
+        * If the PCB is present and the socket isn't allowed to use
+        * the cellular interface, indicate it as such for tcp_respond.
+        */
+       if (inp != NULL && (inp->inp_flags & INP_NO_IFT_CELLULAR))
+               nocell = 1;
+
 #if IPSEC
        if (ipsec_bypass == 0)  {
-               lck_mtx_lock(sadb_mutex);
 #if INET6
                if (isipv6) {
                        if (inp != NULL && ipsec6_in_reject_so(m, inp->inp_socket)) {
-                               ipsec6stat.in_polvio++;
-                               lck_mtx_unlock(sadb_mutex);
+                               IPSEC_STAT_INCREMENT(ipsec6stat.in_polvio);
+                               if (in_pcb_checkstate(inp, WNT_RELEASE, 0) == WNT_STOPUSING) 
+                                       inp = NULL;     // pretend we didn't find it 
                                goto dropnosock;
                        }
                } else
 #endif /* INET6 */
                        if (inp != NULL && ipsec4_in_reject_so(m, inp->inp_socket)) {
-                               ipsecstat.in_polvio++;
-                               lck_mtx_unlock(sadb_mutex);
+                               IPSEC_STAT_INCREMENT(ipsecstat.in_polvio);
+                               if (in_pcb_checkstate(inp, WNT_RELEASE, 0) == WNT_STOPUSING) 
+                                       inp = NULL;     // pretend we didn't find it 
                                goto dropnosock;
                        }
-               lck_mtx_unlock(sadb_mutex);
        }
 #endif /*IPSEC*/
 
@@ -857,16 +1226,21 @@ findpcb:
        }
        so = inp->inp_socket;
        if (so == NULL) {
-               if (in_pcb_checkstate(inp, WNT_RELEASE, 1) == WNT_STOPUSING) 
-                       inp = NULL;     // pretend we didn't find it 
+               /* This case shouldn't happen  as the socket shouldn't be null
+                * if inp_state isn't set to INPCB_STATE_DEAD
+                * But just in case, we pretend we didn't find the socket if we hit this case
+                * as this isn't cause for a panic (the socket might be leaked however)...
+                */
+               inp = NULL;
 #if TEMPDEBUG
-               printf("tcp_input: no more socket for inp=%x\n", inp);
+               printf("tcp_input: no more socket for inp=%x. This shouldn't happen\n", inp);
 #endif
                goto dropnosock;
        }
-       tcp_lock(so, 1, 2);
+
+       tcp_lock(so, 1, 0);
        if (in_pcb_checkstate(inp, WNT_RELEASE, 1) == WNT_STOPUSING) {
-               tcp_unlock(so, 1, 2);
+               tcp_unlock(so, 1, (void *)2);
                inp = NULL;     // pretend we didn't find it 
                goto dropnosock;
        }
@@ -879,21 +1253,21 @@ findpcb:
        if (tp->t_state == TCPS_CLOSED)
                goto drop;
 
-#ifdef __APPLE__
-        /* 
-         * Bogus state when listening port owned by SharedIP with loopback as the 
-         * only configured interface: BlueBox does not filters loopback
-         */ 
-       if (tp->t_state == TCP_NSTATES)
-               goto drop;
-#endif
-
        /* Unscale the window into a 32-bit value. */
        if ((thflags & TH_SYN) == 0)
                tiwin = th->th_win << tp->snd_scale;
        else
                tiwin = th->th_win;
 
+#if CONFIG_MACF_NET
+       if (mac_inpcb_check_deliver(inp, m, AF_INET, SOCK_STREAM))
+               goto drop;
+#endif
+
+       /* Radar 7377561: Avoid processing packets while closing a listen socket */
+       if (tp->t_state == TCPS_LISTEN && (so->so_options & SO_ACCEPTCONN) == 0) 
+               goto drop;
+
        if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) {
 #if TCPDEBUG
                if (so->so_options & SO_DEBUG) {
@@ -916,28 +1290,71 @@ findpcb:
 #if INET6
                        struct inpcb *oinp = sotoinpcb(so);
 #endif /* INET6 */
-                       int ogencnt = so->so_gencnt;
+                       unsigned int head_ifscope;
+                       unsigned int head_nocell;
+
+                       /* Get listener's bound-to-interface, if any */
+                       head_ifscope = (inp->inp_flags & INP_BOUND_IF) ?
+                           inp->inp_boundif : IFSCOPE_NONE;
+                       /* Get listener's no-cellular information, if any */
+                       head_nocell = (inp->inp_flags & INP_NO_IFT_CELLULAR) ? 1 : 0;
 
-#if !IPSEC
                        /*
-                        * Current IPsec implementation makes incorrect IPsec
-                        * cache if this check is done here.
-                        * So delay this until duplicated socket is created.
+                        * If the state is LISTEN then ignore segment if it contains an RST.
+                        * If the segment contains an ACK then it is bad and send a RST.
+                        * If it does not contain a SYN then it is not interesting; drop it.
+                        * If it is from this socket, drop it, it must be forged.
                         */
                        if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) {
-                               /*
-                                * Note: dropwithreset makes sure we don't
-                                * send a RST in response to a RST.
-                                */
+                               if (thflags & TH_RST) {
+                                       goto drop;
+                               }
                                if (thflags & TH_ACK) {
+                                       tp = NULL;
                                        tcpstat.tcps_badsyn++;
                                        rstreason = BANDLIM_RST_OPENPORT;
                                        goto dropwithreset;
                                }
+
+                               /* We come here if there is no SYN set */
+                               tcpstat.tcps_badsyn++;
                                goto drop;
                        }
-#endif
                        KERNEL_DEBUG(DBG_FNC_TCP_NEWCONN | DBG_FUNC_START,0,0,0,0,0);
+                       if (th->th_dport == th->th_sport) {
+#if INET6
+                               if (isipv6) {
+                                       if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
+                                                       &ip6->ip6_src))
+                                               goto drop;
+                               } else
+#endif /* INET6 */
+                                       if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
+                                               goto drop;
+                       }
+                       /*
+                        * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
+                        * in_broadcast() should never return true on a received
+                        * packet with M_BCAST not set.
+                        *
+                        * Packets with a multicast source address should also
+                        * be discarded.
+                        */
+                       if (m->m_flags & (M_BCAST|M_MCAST))
+                               goto drop;
+#if INET6
+                       if (isipv6) {
+                               if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
+                                       IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
+                                       goto drop;
+                       } else
+#endif
+                       if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
+                               IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
+                               ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
+                               in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
+                               goto drop;
+
 
 #if INET6
                        /*
@@ -973,15 +1390,23 @@ findpcb:
                        if (isipv6 && !ip6_use_deprecated) {
                                struct in6_ifaddr *ia6;
 
-                               if ((ia6 = ip6_getdstifaddr(m)) &&
-                                   (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
-                                       tp = NULL;
-                                       rstreason = BANDLIM_RST_OPENPORT;
-                                       goto dropwithreset;
+                               ia6 = ip6_getdstifaddr(m);
+                               if (ia6 != NULL) {
+                                       IFA_LOCK_SPIN(&ia6->ia_ifa);
+                                       if (ia6->ia6_flags & IN6_IFF_DEPRECATED) {
+                                               IFA_UNLOCK(&ia6->ia_ifa);
+                                               IFA_REMREF(&ia6->ia_ifa);
+                                               tp = NULL;
+                                               rstreason = BANDLIM_RST_OPENPORT;
+                                               goto dropwithreset;
+                                       }
+                                       IFA_UNLOCK(&ia6->ia_ifa);
+                                       IFA_REMREF(&ia6->ia_ifa);
                                }
                        }
 #endif
                        if (so->so_filt) {
+#if INET6
                                if (isipv6) {
                                        struct sockaddr_in6     *sin6 = (struct sockaddr_in6*)&from;
                                        
@@ -991,7 +1416,10 @@ findpcb:
                                        sin6->sin6_flowinfo = 0;
                                        sin6->sin6_addr = ip6->ip6_src;
                                        sin6->sin6_scope_id = 0;
-                               } else {
+                               }
+                               else
+#endif
+                               {
                                        struct sockaddr_in *sin = (struct sockaddr_in*)&from;
                                        
                                        sin->sin_len = sizeof(*sin);
@@ -1005,7 +1433,7 @@ findpcb:
                        }
                        if (so2 == 0) {
                                tcpstat.tcps_listendrop++;
-                               if (tcpdropdropablreq(so)) {
+                               if (tcp_dropdropablreq(so)) {
                                        if (so->so_filt)
                                                so2 = sonewconn(so, 0, (struct sockaddr*)&from);
                                        else
@@ -1014,12 +1442,10 @@ findpcb:
                                if (!so2) 
                                        goto drop;
                        }
-                       /*
-                        * Make sure listening socket did not get closed during socket allocation,
-                        * not only this is incorrect but it is know to cause panic
-                        */
-                       if (so->so_gencnt != ogencnt)
-                               goto drop;
+
+                       /* Point "inp" and "tp" in tandem to new socket */
+                       inp = (struct inpcb *)so2->so_pcb;
+                       tp = intotcpcb(inp);
 
                        oso = so;
                        tcp_unlock(so, 0, 0); /* Unlock but keep a reference on listener for now */
@@ -1027,8 +1453,6 @@ findpcb:
                        so = so2;
                        tcp_lock(so, 1, 0);
                        /*
-                        * This is ugly, but ....
-                        *
                         * Mark socket as temporary until we're
                         * committed to keeping it.  The code at
                         * ``drop'' and ``dropwithreset'' check the
@@ -1036,9 +1460,26 @@ findpcb:
                         * socket created here should be discarded.
                         * We mark the socket as discardable until
                         * we're committed to it below in TCPS_LISTEN.
+                        * There are some error conditions in which we
+                        * have to drop the temporary socket.
                         */
                        dropsocket++;
-                       inp = (struct inpcb *)so->so_pcb;
+                       /*
+                        * Inherit INP_BOUND_IF from listener; testing if
+                        * head_ifscope is non-zero is sufficient, since it
+                        * can only be set to a non-zero value earlier if
+                        * the listener has such a flag set.
+                        */
+                       if (head_ifscope != IFSCOPE_NONE) {
+                               inp->inp_flags |= INP_BOUND_IF;
+                               inp->inp_boundif = head_ifscope;
+                       }
+                       /*
+                        * Inherit INP_NO_IFT_CELLULAR from listener.
+                        */
+                       if (head_nocell) {
+                               inp->inp_flags |= INP_NO_IFT_CELLULAR;
+                       }
 #if INET6
                        if (isipv6)
                                inp->in6p_laddr = ip6->ip6_dst;
@@ -1046,7 +1487,7 @@ findpcb:
                                inp->inp_vflag &= ~INP_IPV6;
                                inp->inp_vflag |= INP_IPV4;
 #endif /* INET6 */
-                       inp->inp_laddr = ip->ip_dst;
+                               inp->inp_laddr = ip->ip_dst;
 #if INET6
                        }
 #endif /* INET6 */
@@ -1067,30 +1508,6 @@ findpcb:
                                tcp_unlock(oso, 1, 0);
                                goto drop;
                        }
-#if IPSEC
-                       /*
-                        * To avoid creating incorrectly cached IPsec
-                        * association, this is need to be done here.
-                        *
-                        * Subject: (KAME-snap 748)
-                        * From: Wayne Knowles <w.knowles@niwa.cri.nz>
-                        * ftp://ftp.kame.net/pub/mail-list/snap-users/748
-                        */
-                       if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) {
-                               /*
-                                * Note: dropwithreset makes sure we don't
-                                * send a RST in response to a RST.
-                                */
-                               tcp_lock(oso, 0, 0);    /* release ref on parent */
-                               tcp_unlock(oso, 1, 0);
-                               if (thflags & TH_ACK) {
-                                       tcpstat.tcps_badsyn++;
-                                       rstreason = BANDLIM_RST_OPENPORT;
-                                       goto dropwithreset;
-                               }
-                               goto drop;
-                       }
-#endif
 #if INET6
                        if (isipv6) {
                                /*
@@ -1121,33 +1538,42 @@ findpcb:
                        if (sotoinpcb(oso)->inp_sp)
                        {
                                int error = 0;
-                               lck_mtx_lock(sadb_mutex);
                                /* Is it a security hole here to silently fail to copy the policy? */
                                if (inp->inp_sp != NULL)
                                        error = ipsec_init_policy(so, &inp->inp_sp);
                                if (error != 0 || ipsec_copy_policy(sotoinpcb(oso)->inp_sp, inp->inp_sp))
                                        printf("tcp_input: could not copy policy\n");
-                               lck_mtx_unlock(sadb_mutex);
                        }
 #endif
-                       tcp_unlock(oso, 1, 0);  /* now drop the reference on the listener */
-                       tp = intotcpcb(inp);
+                       /* inherit states from the listener */
+                       DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp,
+                               struct tcpcb *, tp, int32_t, TCPS_LISTEN);
                        tp->t_state = TCPS_LISTEN;
                        tp->t_flags |= tp0->t_flags & (TF_NOPUSH|TF_NOOPT|TF_NODELAY);
+                       tp->t_flagsext |= (tp0->t_flagsext & TF_RXTFINDROP);
+                       tp->t_keepinit = tp0->t_keepinit;
                        tp->t_inpcb->inp_ip_ttl = tp0->t_inpcb->inp_ip_ttl;
+
+                       /* now drop the reference on the listener */
+                       tcp_unlock(oso, 1, 0);
+
                        /* Compute proper scaling value from buffer space */
-                       while (tp->request_r_scale < TCP_MAX_WINSHIFT &&
-                          TCP_MAXWIN << tp->request_r_scale <
-                          so->so_rcv.sb_hiwat)
-                               tp->request_r_scale++;
+                       if (inp->inp_pcbinfo->ipi_count < tcp_sockthreshold) {
+                               tp->request_r_scale = max(tcp_win_scale, tp->request_r_scale);
+                               so->so_rcv.sb_hiwat = imin(TCP_MAXWIN << tp->request_r_scale, (sb_max / (MSIZE+MCLBYTES)) * MCLBYTES);  
+                       }
+                       else {
+                               while (tp->request_r_scale < TCP_MAX_WINSHIFT &&
+                               TCP_MAXWIN << tp->request_r_scale <
+                               so->so_rcv.sb_hiwat)
+                                       tp->request_r_scale++;
+                       }
 
                        KERNEL_DEBUG(DBG_FNC_TCP_NEWCONN | DBG_FUNC_END,0,0,0,0,0);
                }
        }
+       lck_mtx_assert(&((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED);
 
-#if 1
-       lck_mtx_assert(((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED);
-#endif
        /*
         * Radar 3529618
         * This is the second part of the MSS DoS prevention code (after
@@ -1170,17 +1596,17 @@ findpcb:
         * example interactive connections with many small packets like
         * telnet or SSH.
         *
+        * Setting either tcp_minmssoverload or tcp_minmss to "0" disables
+        * this check.
         *
         * Account for packet if payload packet, skip over ACK, etc.
-        *
-        * The packet per second count is done all the time and is also used
-        * by "DELAY_ACK" to detect streaming situations.
-        *
         */
        if (tp->t_state == TCPS_ESTABLISHED && tlen > 0) {
-               if (tp->rcv_reset > tcp_now) {
+               if (TSTMP_GT(tp->rcv_reset, tcp_now)) {
                        tp->rcv_pps++;
                        tp->rcv_byps += tlen + off;
+                       if (tp->rcv_byps > tp->rcv_maxbyps)
+                               tp->rcv_maxbyps = tp->rcv_byps;
                /*
                 * Setting either tcp_minmssoverload or tcp_minmss to "0" disables
                 * the check. 
@@ -1189,9 +1615,9 @@ findpcb:
                                if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) {
                                        char    ipstrbuf[MAX_IPv6_STR_LEN];
                                        printf("too many small tcp packets from "
-                                              "%s:%u, av. %lubyte/packet, "
+                                              "%s:%u, av. %ubyte/packet, "
                                               "dropping connection\n",
-#ifdef INET6
+#if INET6
                                                isipv6 ?
                                                inet_ntop(AF_INET6, &inp->in6p_faddr, ipstrbuf,
                                                                  sizeof(ipstrbuf)) :
@@ -1206,56 +1632,185 @@ findpcb:
                                }
                        }
                } else {
-                       tp->rcv_reset = tcp_now + PR_SLOWHZ;
+                       tp->rcv_reset = tcp_now + TCP_RETRANSHZ;
                        tp->rcv_pps = 1;
                        tp->rcv_byps = tlen + off;
                }
+
+               /* Evaluate the rate of arrival of packets to see if the 
+                * receiver can reduce the ack traffic. The algorithm to 
+                * stretch acks will be enabled if the connection meets 
+                * certain criteria defined in tcp_stretch_ack_enable function.
+                */
+               if ((tp->t_flagsext & TF_RCVUNACK_WAITSS) != 0) {
+                       tp->rcv_waitforss++;
+               }
+               if (tcp_stretch_ack_enable(tp)) {
+                       tp->t_flags |= TF_STRETCHACK;
+                       tp->t_flagsext &= ~(TF_RCVUNACK_WAITSS);
+                       tp->rcv_waitforss = 0;
+               } else {
+                       tp->t_flags &= ~(TF_STRETCHACK);
+               }
+               if (TSTMP_GT(tp->rcv_unackwin, tcp_now)) {
+                       tp->rcv_by_unackwin += (tlen + off);
+               } else {
+                       tp->rcv_unackwin = tcp_now + tcp_rcvunackwin;
+                       tp->rcv_by_unackwin = tlen + off;
+               }
+       }
+       
+       /*
+          Explicit Congestion Notification - Flag that we need to send ECT if
+               + The IP Congestion experienced flag was set.
+               + Socket is in established state
+               + We negotiated ECN in the TCP setup
+               + This isn't a pure ack (tlen > 0)
+               + The data is in the valid window
+       
+               TE_SENDECE will be cleared when we receive a packet with TH_CWR set.
+        */
+       if (ip_ecn == IPTOS_ECN_CE && tp->t_state == TCPS_ESTABLISHED &&
+               (tp->ecn_flags & (TE_SETUPSENT | TE_SETUPRECEIVED)) ==
+                (TE_SETUPSENT | TE_SETUPRECEIVED) && tlen > 0 &&
+               SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
+               SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
+               tp->ecn_flags |= TE_SENDECE;
+       }
+       
+       /*
+          Clear TE_SENDECE if TH_CWR is set. This is harmless, so we don't
+          bother doing extensive checks for state and whatnot.
+        */
+       if ((thflags & TH_CWR) == TH_CWR) {
+               tp->ecn_flags &= ~TE_SENDECE;
        }
+
+       /* If we received an  explicit notification of congestion in 
+        * ip tos ecn bits or by the CWR bit in TCP header flags, reset
+        * the ack-strteching state.
+        */
+       if (tp->t_state == TCPS_ESTABLISHED && (tp->t_flags & TF_STRETCHACK) != 0 &&
+               ((ip_ecn == IPTOS_ECN_CE) || ((thflags & TH_CWR) == TH_CWR)))
+               tcp_reset_stretch_ack(tp);
        
        /*
         * Segment received on connection.
         * Reset idle time and keep-alive timer.
         */
-       tp->t_rcvtime = 0;
+       tp->t_rcvtime = tcp_now;
        if (TCPS_HAVEESTABLISHED(tp->t_state))
-               tp->t_timer[TCPT_KEEP] = TCP_KEEPIDLE(tp);
+               tp->t_timer[TCPT_KEEP] = OFFSET_FROM_START(tp, TCP_KEEPIDLE(tp));
 
        /*
         * Process options if not in LISTEN state,
         * else do it below (after getting remote address).
         */
        if (tp->t_state != TCPS_LISTEN && optp)
-               tcp_dooptions(tp, optp, optlen, th, &to);
+               tcp_dooptions(tp, optp, optlen, th, &to, ifscope);
 
-       /*
-        * Header prediction: check for the two common cases
-        * of a uni-directional data xfer.  If the packet has
-        * no control flags, is in-sequence, the window didn't
-        * change and we're not retransmitting, it's a
-        * candidate.  If the length is zero and the ack moved
-        * forward, we're the sender side of the xfer.  Just
-        * free the data acked & wake any higher level process
-        * that was blocked waiting for space.  If the length
-        * is non-zero and the ack didn't move, we're the
-        * receiver side.  If we're getting packets in-order
-        * (the reassembly queue is empty), add the data to
+       if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
+               if (to.to_flags & TOF_SCALE) {
+                       tp->t_flags |= TF_RCVD_SCALE;
+                       tp->requested_s_scale = to.to_requested_s_scale;
+                       tp->snd_wnd = th->th_win << tp->snd_scale;
+                       tiwin = tp->snd_wnd;
+               }
+               if (to.to_flags & TOF_TS) {
+                       tp->t_flags |= TF_RCVD_TSTMP;
+                       tp->ts_recent = to.to_tsval;
+                       tp->ts_recent_age = tcp_now;
+               }
+               if (to.to_flags & TOF_MSS)
+                       tcp_mss(tp, to.to_mss, ifscope);
+               if (tp->sack_enable) {
+                       if (!(to.to_flags & TOF_SACK))
+                               tp->sack_enable = 0;
+                       else
+                               tp->t_flags |= TF_SACK_PERMIT;
+               }
+       }
+
+#if TRAFFIC_MGT
+       /* Compute inter-packet arrival jitter. According to RFC 3550, inter-packet 
+        * arrival jitter is defined as the difference in packet spacing at the 
+        * receiver compared to the sender for a pair of packets. When two packets 
+        * of maximum segment size come one after the other with consecutive 
+        * sequence numbers, we consider them as packets sent together at the 
+        * sender and use them as a pair to compute inter-packet arrival jitter.
+        * This metric indicates the delay induced by the network components due
+        * to queuing in edge/access routers.
+        */
+       if (tp->t_state == TCPS_ESTABLISHED &&
+           (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK|TH_ECE|TH_PUSH)) == TH_ACK &&
+           ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
+           ((to.to_flags & TOF_TS) == 0 ||
+            TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
+           th->th_seq == tp->rcv_nxt &&
+           LIST_EMPTY(&tp->t_segq)) {
+               if (tp->iaj_pktcnt <= IAJ_IGNORE_PKTCNT) {
+                       tp->iaj_pktcnt++;
+               }
+
+               if ( tp->iaj_size == 0 || tlen > tp->iaj_size ||
+                       (tlen == tp->iaj_size && tp->iaj_rcv_ts == 0)) {
+                       /* State related to inter-arrival jitter is uninitialized 
+                        * or we are trying to find a good first packet to start 
+                        * computing the metric
+                        */
+                       update_iaj_state(tp, tlen, 0);
+               } else {
+                       if (tlen == tp->iaj_size) {
+                               /* Compute inter-arrival jitter taking this packet 
+                                * as the second packet
+                                */
+                               compute_iaj(tp);
+                       } 
+                       if (tlen  < tp->iaj_size) {
+                               /* There is a smaller packet in the stream.
+                                * Some times the maximum size supported on a path can 
+                                * change if there is a new link with smaller MTU. 
+                                * The receiver will not know about this change. 
+                                * If there are too many packets smaller than iaj_size, 
+                                * we try to learn the iaj_size again.
+                                */
+                               tp->iaj_small_pkt++;
+                               if (tp->iaj_small_pkt > RESET_IAJ_SIZE_THRESH) {
+                                       update_iaj_state(tp, tlen, 1);
+                               } else {
+                                       clear_iaj_state(tp);
+                               }
+                       } else {
+                               update_iaj_state(tp, tlen, 0);
+                       }
+               }
+       } else {
+               clear_iaj_state(tp);
+       }
+#endif /* TRAFFIC_MGT */
+
+       /*
+        * Header prediction: check for the two common cases
+        * of a uni-directional data xfer.  If the packet has
+        * no control flags, is in-sequence, the window didn't
+        * change and we're not retransmitting, it's a
+        * candidate.  If the length is zero and the ack moved
+        * forward, we're the sender side of the xfer.  Just
+        * free the data acked & wake any higher level process
+        * that was blocked waiting for space.  If the length
+        * is non-zero and the ack didn't move, we're the
+        * receiver side.  If we're getting packets in-order
+        * (the reassembly queue is empty), add the data to
         * the socket buffer and note that we need a delayed ack.
         * Make sure that the hidden state-flags are also off.
         * Since we check for TCPS_ESTABLISHED above, it can only
         * be TH_NEEDSYN.
         */
        if (tp->t_state == TCPS_ESTABLISHED &&
-           (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
+           (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK|TH_ECE)) == TH_ACK &&
            ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
-           ((to.to_flag & TOF_TS) == 0 ||
+           ((to.to_flags & TOF_TS) == 0 ||
             TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
-           /*
-            * Using the CC option is compulsory if once started:
-            *   the segment is OK if no T/TCP was negotiated or
-            *   if the segment has a CC option equal to CCrecv
-            */
-           ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) ||
-            ((to.to_flag & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) &&
            th->th_seq == tp->rcv_nxt &&
            tiwin && tiwin == tp->snd_wnd &&
            tp->snd_nxt == tp->snd_max) {
@@ -1266,17 +1821,25 @@ findpcb:
                 * NOTE that the test is modified according to the latest
                 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
                 */
-               if ((to.to_flag & TOF_TS) != 0 &&
+               if ((to.to_flags & TOF_TS) != 0 &&
                   SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
                        tp->ts_recent_age = tcp_now;
                        tp->ts_recent = to.to_tsval;
                }
 
+               /* Force acknowledgment if we received a FIN */
+
+               if (thflags & TH_FIN)
+                       tp->t_flags |= TF_ACKNOW;
+
                if (tlen == 0) {
                        if (SEQ_GT(th->th_ack, tp->snd_una) &&
                            SEQ_LEQ(th->th_ack, tp->snd_max) &&
-                           tp->snd_cwnd >= tp->snd_wnd &&
-                           tp->t_dupacks < tcprexmtthresh) {
+                           tp->snd_cwnd >= tp->snd_ssthresh &&
+                           (!IN_FASTRECOVERY(tp) && 
+                           ((!tp->sack_enable && tp->t_dupacks < tcprexmtthresh) ||
+                            (tp->sack_enable && to.to_nsacks == 0 &&
+                             TAILQ_EMPTY(&tp->snd_holes))))) {
                                /*
                                 * this is a pure ack for outstanding data.
                                 */
@@ -1285,24 +1848,64 @@ findpcb:
                                 * "bad retransmit" recovery
                                 */
                                if (tp->t_rxtshift == 1 &&
-                                   tcp_now < tp->t_badrxtwin) { 
+                                   TSTMP_LT(tcp_now, tp->t_badrxtwin)) {
+                                       ++tcpstat.tcps_sndrexmitbad;
                                        tp->snd_cwnd = tp->snd_cwnd_prev;
                                        tp->snd_ssthresh =
                                            tp->snd_ssthresh_prev;
+                                       tp->snd_recover = tp->snd_recover_prev;
+                                       if (tp->t_flags & TF_WASFRECOVERY)
+                                           ENTER_FASTRECOVERY(tp);
                                        tp->snd_nxt = tp->snd_max;
                                        tp->t_badrxtwin = 0;
+                                       tp->t_rxtshift = 0;
+                                       tp->rxt_start = 0;
+                                       DTRACE_TCP5(cc, void, NULL, struct inpcb *, tp->t_inpcb,
+                                               struct tcpcb *, tp, struct tcphdr *, th,
+                                               int32_t, TCP_CC_BAD_REXMT_RECOVERY);
                                }
-                               if (((to.to_flag & TOF_TS) != 0) && (to.to_tsecr != 0)) /* Makes sure we already have a TS */
+                               /*
+                                * Recalculate the transmit timer / rtt.
+                                *
+                                * Some boxes send broken timestamp replies
+                                * during the SYN+ACK phase, ignore
+                                * timestamps of 0 or we could calculate a
+                                * huge RTT and blow up the retransmit timer.
+                                */
+                               if (((to.to_flags & TOF_TS) != 0) && (to.to_tsecr != 0) &&
+                                       TSTMP_GEQ(tcp_now, to.to_tsecr)) { 
                                        tcp_xmit_timer(tp,
-                                           tcp_now - to.to_tsecr + 1);
-                               else if (tp->t_rtttime &&
-                                           SEQ_GT(th->th_ack, tp->t_rtseq))
-                                       tcp_xmit_timer(tp, tp->t_rtttime);
+                                           tcp_now - to.to_tsecr);
+                               } else if (tp->t_rtttime &&
+                                           SEQ_GT(th->th_ack, tp->t_rtseq)) {
+                                       tcp_xmit_timer(tp, tcp_now - tp->t_rtttime);
+                               }
                                acked = th->th_ack - tp->snd_una;
                                tcpstat.tcps_rcvackpack++;
                                tcpstat.tcps_rcvackbyte += acked;
+                               
+                               /* Handle an ack that is in sequence during congestion
+                                * avoidance phase. The calculations in this function 
+                                * assume that snd_una is not updated yet. 
+                                */
+                               if (CC_ALGO(tp)->inseq_ack_rcvd != NULL)
+                                       CC_ALGO(tp)->inseq_ack_rcvd(tp, th);
+
+                               DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp,
+                                       struct tcpcb *, tp, struct tcphdr *, th,
+                                       int32_t, TCP_CC_INSEQ_ACK_RCVD);
+
                                sbdrop(&so->so_snd, acked);
+                               if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
+                                   SEQ_LEQ(th->th_ack, tp->snd_recover))
+                                       tp->snd_recover = th->th_ack - 1;
                                tp->snd_una = th->th_ack;
+                               /*
+                                * pull snd_wl2 up to prevent seq wrap relative
+                                * to th_ack.
+                                */
+                               tp->snd_wl2 = th->th_ack;
+                               tp->t_dupacks = 0;
                                m_freem(m);
                                ND6_HINT(tp); /* some progress has been done */
 
@@ -1318,33 +1921,54 @@ findpcb:
                                if (tp->snd_una == tp->snd_max)
                                        tp->t_timer[TCPT_REXMT] = 0;
                                else if (tp->t_timer[TCPT_PERSIST] == 0)
-                                       tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
+                                       tp->t_timer[TCPT_REXMT] = OFFSET_FROM_START(tp, tp->t_rxtcur);
 
                                sowwakeup(so); /* has to be done with socket lock held */
-                               if ((so->so_snd.sb_cc) || (tp->t_flags & TF_ACKNOW))
+                               if ((so->so_snd.sb_cc) || (tp->t_flags & TF_ACKNOW)) {
                                        (void) tcp_output(tp);
+                               }
+
+                               tcp_check_timer_state(tp);
                                tcp_unlock(so, 1, 0);
                                KERNEL_DEBUG(DBG_FNC_TCP_INPUT | DBG_FUNC_END,0,0,0,0,0);
                                return;
                        }
                } else if (th->th_ack == tp->snd_una &&
                    LIST_EMPTY(&tp->t_segq) &&
-                   tlen <= sbspace(&so->so_rcv)) {
+                   tlen <= tcp_sbspace(tp)) {
                        /*
                         * this is a pure, in-sequence data packet
                         * with nothing on the reassembly queue and
                         * we have enough buffer space to take it.
                         */
+                       /* Clean receiver SACK report if present */
+                       if (tp->sack_enable && tp->rcv_numsacks)
+                               tcp_clean_sackreport(tp);
                        ++tcpstat.tcps_preddat;
                        tp->rcv_nxt += tlen;
+                       /*
+                        * Pull snd_wl1 up to prevent seq wrap relative to
+                        * th_seq.
+                        */
+                       tp->snd_wl1 = th->th_seq;
+                       /*
+                        * Pull rcv_up up to prevent seq wrap relative to
+                        * rcv_nxt.
+                        */
+                       tp->rcv_up = tp->rcv_nxt;
                        tcpstat.tcps_rcvpack++;
                        tcpstat.tcps_rcvbyte += tlen;
+                       if (nstat_collect) {
+                               locked_add_64(&inp->inp_stat->rxpackets, 1);
+                               locked_add_64(&inp->inp_stat->rxbytes, tlen);
+                       }
                        ND6_HINT(tp);   /* some progress has been done */
                        /*
                         * Add data to socket buffer.
                         */
+                       so_recv_data_stat(so, m, 0);
                        m_adj(m, drop_hdrlen);  /* delayed header drop */
-                       if (sbappend(&so->so_rcv, m))
+                       if (sbappendstream(&so->so_rcv, m))
                                sorwakeup(so);
 #if INET6
                        if (isipv6) {
@@ -1359,12 +1983,17 @@ findpcb:
                                        (((ip->ip_src.s_addr & 0xffff) << 16) | (ip->ip_dst.s_addr & 0xffff)),
                                        th->th_seq, th->th_ack, th->th_win); 
                        }
-                       if (DELAY_ACK(tp))  {
-                           tp->t_flags |= TF_DELACK;
+                       if (DELAY_ACK(tp, th))  {
+                               if ((tp->t_flags & TF_DELACK) == 0) {
+                                       tp->t_flags |= TF_DELACK;
+                                       tp->t_timer[TCPT_DELACK] = OFFSET_FROM_START(tp, tcp_delack);
+                               }
+                               tp->t_unacksegs++;
                        } else {
                                tp->t_flags |= TF_ACKNOW;
                                tcp_output(tp);
                        }
+                       tcp_check_timer_state(tp);
                        tcp_unlock(so, 1, 0);
                        KERNEL_DEBUG(DBG_FNC_TCP_INPUT | DBG_FUNC_END,0,0,0,0,0);
                        return;
@@ -1377,12 +2006,12 @@ findpcb:
         * Receive window is amount of space in rcv queue,
         * but not less than advertised window.
         */
-#if 1
-       lck_mtx_assert(((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED);
-#endif
+       lck_mtx_assert(&((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED);
+
        { int win;
 
-       win = sbspace(&so->so_rcv);
+       win = tcp_sbspace(tp);
+
        if (win < 0)
                win = 0;
        else {  /* clip rcv window to 4K for modems */
@@ -1395,12 +2024,7 @@ findpcb:
        switch (tp->t_state) {
 
        /*
-        * If the state is LISTEN then ignore segment if it contains an RST.
-        * If the segment contains an ACK then it is bad and send a RST.
-        * If it does not contain a SYN then it is not interesting; drop it.
-        * If it is from this socket, drop it, it must be forged.
-        * Don't bother responding if the destination was a broadcast.
-        * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial
+        * Initialize tp->rcv_nxt, and tp->irs, select an initial
         * tp->iss, and send a segment:
         *     <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
         * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss.
@@ -1414,50 +2038,7 @@ findpcb:
                register struct sockaddr_in6 *sin6;
 #endif
 
-#if 1
-               lck_mtx_assert(((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED);
-#endif
-               if (thflags & TH_RST) 
-                       goto drop;
-               if (thflags & TH_ACK) {
-                       rstreason = BANDLIM_RST_OPENPORT;
-                       goto dropwithreset;
-               }
-               if ((thflags & TH_SYN) == 0)
-                       goto drop;
-               if (th->th_dport == th->th_sport) {
-#if INET6
-                       if (isipv6) {
-                               if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
-                                                      &ip6->ip6_src))
-                                       goto drop;
-                       } else
-#endif /* INET6 */
-                       if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
-                               goto drop;
-               }
-               /*
-                * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
-                * in_broadcast() should never return true on a received
-                * packet with M_BCAST not set.
-                *
-                * Packets with a multicast source address should also
-                * be discarded.
-                */
-               if (m->m_flags & (M_BCAST|M_MCAST))
-                       goto drop;
-#if INET6
-               if (isipv6) {
-                       if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
-                           IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
-                               goto drop;
-               } else
-#endif
-               if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
-                   IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
-                   ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
-                   in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
-                       goto drop;
+               lck_mtx_assert(&((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED);
 #if INET6
                if (isipv6) {
                        MALLOC(sin6, struct sockaddr_in6 *, sizeof *sin6,
@@ -1482,9 +2063,7 @@ findpcb:
                } else
 #endif
            {
-#if 1
-                       lck_mtx_assert(((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED);
-#endif
+                       lck_mtx_assert(&((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED);
                        MALLOC(sin, struct sockaddr_in *, sizeof *sin, M_SONAME,
                       M_NOWAIT);
                        if (sin == NULL)
@@ -1497,18 +2076,23 @@ findpcb:
                        laddr = inp->inp_laddr;
                        if (inp->inp_laddr.s_addr == INADDR_ANY)
                                inp->inp_laddr = ip->ip_dst;
-                       if (in_pcbconnect(inp, (struct sockaddr *)sin, proc0)) {
+                       if (in_pcbconnect(inp, (struct sockaddr *)sin, proc0, NULL)) {
                                inp->inp_laddr = laddr;
                                FREE(sin, M_SONAME);
                                goto drop;
                        }
                        FREE(sin, M_SONAME);
                }
-               if ((taop = tcp_gettaocache(inp)) == NULL) {
-                       taop = &tao_noncached;
-                       bzero(taop, sizeof(*taop));
+
+               tcp_dooptions(tp, optp, optlen, th, &to, ifscope);
+
+               if (tp->sack_enable) {
+                       if (!(to.to_flags & TOF_SACK))
+                               tp->sack_enable = 0;
+                       else
+                               tp->t_flags |= TF_SACK_PERMIT;
                }
-               tcp_dooptions(tp, optp, optlen, th, &to);
+               
                if (iss)
                        tp->iss = iss;
                else {
@@ -1524,87 +2108,29 @@ findpcb:
                 *   initialize CCsend and CCrecv.
                 */
                tp->snd_wnd = tiwin;    /* initial send-window */
-               tp->cc_send = CC_INC(tcp_ccgen);
-               tp->cc_recv = to.to_cc;
-               /*
-                * Perform TAO test on incoming CC (SEG.CC) option, if any.
-                * - compare SEG.CC against cached CC from the same host,
-                *      if any.
-                * - if SEG.CC > chached value, SYN must be new and is accepted
-                *      immediately: save new CC in the cache, mark the socket
-                *      connected, enter ESTABLISHED state, turn on flag to
-                *      send a SYN in the next segment.
-                *      A virtual advertised window is set in rcv_adv to
-                *      initialize SWS prevention.  Then enter normal segment
-                *      processing: drop SYN, process data and FIN.
-                * - otherwise do a normal 3-way handshake.
-                */
-               if ((to.to_flag & TOF_CC) != 0) {
-                   if (((tp->t_flags & TF_NOPUSH) != 0) &&
-                       taop->tao_cc != 0 && CC_GT(to.to_cc, taop->tao_cc)) {
-
-                       taop->tao_cc = to.to_cc;
-
-                       tp->t_state = TCPS_ESTABLISHED;
-
-                       /*
-                        * If there is a FIN, or if there is data and the
-                        * connection is local, then delay SYN,ACK(SYN) in
-                        * the hope of piggy-backing it on a response
-                        * segment.  Otherwise must send ACK now in case
-                        * the other side is slow starting.
-                        */
-                       if (DELAY_ACK(tp) && ((thflags & TH_FIN) ||
-                           (tlen != 0 &&
-#if INET6
-                             (isipv6 && in6_localaddr(&inp->in6p_faddr))
-                             ||
-                             (!isipv6 &&
-#endif /* INET6 */
-                              in_localaddr(inp->inp_faddr)
-#if INET6
-                              )
-#endif /* INET6 */
-                             ))) {
-                               tp->t_flags |= (TF_DELACK | TF_NEEDSYN);
-                       }
-                       else {
-                               tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
-                       }
-
-                       /*
-                        * Limit the `virtual advertised window' to TCP_MAXWIN
-                        * here.  Even if we requested window scaling, it will
-                        * become effective only later when our SYN is acked.
-                        */
-                       if (tp->t_flags & TF_SLOWLINK && slowlink_wsize > 0) /* clip window size for for slow link */
-                               tp->rcv_adv += min(tp->rcv_wnd, slowlink_wsize);
-                       else 
-                               tp->rcv_adv += min(tp->rcv_wnd, TCP_MAXWIN);
-                       tcpstat.tcps_connects++;
-                       soisconnected(so);
-                       tp->t_timer[TCPT_KEEP] = tcp_keepinit;
-                       dropsocket = 0;         /* committed to socket */
-                       tcpstat.tcps_accepts++;
-                       goto trimthenstep6;
-                   }
-               /* else do standard 3-way handshake */
-               } else {
-                   /*
-                    * No CC option, but maybe CC.NEW:
-                    *   invalidate cached value.
-                    */
-                    taop->tao_cc = 0;
-               }
-               /*
-                * TAO test failed or there was no CC option,
-                *    do a standard 3-way handshake.
-                */
                tp->t_flags |= TF_ACKNOW;
+               tp->t_unacksegs = 0;
+               DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp,
+                       struct tcpcb *, tp, int32_t, TCPS_SYN_RECEIVED);
                tp->t_state = TCPS_SYN_RECEIVED;
-               tp->t_timer[TCPT_KEEP] = tcp_keepinit;
+               tp->t_timer[TCPT_KEEP] = OFFSET_FROM_START(tp, 
+                       tp->t_keepinit ? tp->t_keepinit : tcp_keepinit);
                dropsocket = 0;         /* committed to socket */
+
+               /* reset the incomp processing flag */
+               so->so_flags &= ~(SOF_INCOMP_INPROGRESS);
                tcpstat.tcps_accepts++;
+               if ((thflags & (TH_ECE | TH_CWR)) == (TH_ECE | TH_CWR)) {
+                       /* ECN-setup SYN */
+                       tp->ecn_flags |= (TE_SETUPRECEIVED | TE_SENDIPECT);
+               }
+#if CONFIG_IFEF_NOWINDOWSCALE
+               if (tcp_obey_ifef_nowindowscale && m->m_pkthdr.rcvif != NULL &&
+                   (m->m_pkthdr.rcvif->if_eflags & IFEF_NOWINDOWSCALE)) {
+                       /* Window scaling is not enabled on this interface */
+                       tp->t_flags &= ~TF_REQ_SCALE;
+               }
+#endif
                goto trimthenstep6;
                }
 
@@ -1634,83 +2160,60 @@ findpcb:
         *      continue processing rest of data/controls, beginning with URG
         */
        case TCPS_SYN_SENT:
-               if ((taop = tcp_gettaocache(inp)) == NULL) {
-                       taop = &tao_noncached;
-                       bzero(taop, sizeof(*taop));
-               }
-
                if ((thflags & TH_ACK) &&
                    (SEQ_LEQ(th->th_ack, tp->iss) ||
                     SEQ_GT(th->th_ack, tp->snd_max))) {
-                       /*
-                        * If we have a cached CCsent for the remote host,
-                        * hence we haven't just crashed and restarted,
-                        * do not send a RST.  This may be a retransmission
-                        * from the other side after our earlier ACK was lost.
-                        * Our new SYN, when it arrives, will serve as the
-                        * needed ACK.
-                        */
-                       if (taop->tao_ccsent != 0)
-                               goto drop;
-                       else {
-                               rstreason = BANDLIM_UNLIMITED;
-                               goto dropwithreset;
-                       }
+                       rstreason = BANDLIM_UNLIMITED;
+                       goto dropwithreset;
                }
                if (thflags & TH_RST) {
-                       if (thflags & TH_ACK) {
+                       if ((thflags & TH_ACK) != 0) {
                                tp = tcp_drop(tp, ECONNREFUSED);
                                postevent(so, 0, EV_RESET);
-                 }
+                       }
                        goto drop;
                }
                if ((thflags & TH_SYN) == 0)
                        goto drop;
                tp->snd_wnd = th->th_win;       /* initial send window */
-               tp->cc_recv = to.to_cc;         /* foreign CC */
 
                tp->irs = th->th_seq;
                tcp_rcvseqinit(tp);
                if (thflags & TH_ACK) {
-                       /*
-                        * Our SYN was acked.  If segment contains CC.ECHO
-                        * option, check it to make sure this segment really
-                        * matches our SYN.  If not, just drop it as old
-                        * duplicate, but send an RST if we're still playing
-                        * by the old rules.  If no CC.ECHO option, make sure
-                        * we don't get fooled into using T/TCP.
-                        */
-                       if (to.to_flag & TOF_CCECHO) {
-                               if (tp->cc_send != to.to_ccecho) {
-                                       if (taop->tao_ccsent != 0)
-                                               goto drop;
-                                       else {
-                                               rstreason = BANDLIM_UNLIMITED;
-                                               goto dropwithreset;
-                                       }
-                               }
-                       } else
-                               tp->t_flags &= ~TF_RCVD_CC;
                        tcpstat.tcps_connects++;
-                       soisconnected(so);
+                       
+                       if ((thflags & (TH_ECE | TH_CWR)) == (TH_ECE)) {
+                               /* ECN-setup SYN-ACK */
+                               tp->ecn_flags |= TE_SETUPRECEIVED;
+                       }
+                       else {
+                               /* non-ECN-setup SYN-ACK */
+                               tp->ecn_flags &= ~TE_SENDIPECT;
+                       }
+                       
+#if CONFIG_MACF_NET && CONFIG_MACF_SOCKET
+                       /* XXXMAC: recursive lock: SOCK_LOCK(so); */
+                       mac_socketpeer_label_associate_mbuf(m, so);
+                       /* XXXMAC: SOCK_UNLOCK(so); */
+#endif
                        /* Do window scaling on this connection? */
                        if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
                                (TF_RCVD_SCALE|TF_REQ_SCALE)) {
                                tp->snd_scale = tp->requested_s_scale;
                                tp->rcv_scale = tp->request_r_scale;
                        }
-                       /* Segment is acceptable, update cache if undefined. */
-                       if (taop->tao_ccsent == 0)
-                               taop->tao_ccsent = to.to_ccecho;
-
                        tp->rcv_adv += tp->rcv_wnd;
                        tp->snd_una++;          /* SYN is acked */
                        /*
                         * If there's data, delay ACK; if there's also a FIN
                         * ACKNOW will be turned on later.
                         */
-                       if (DELAY_ACK(tp) && tlen != 0) {
-                               tp->t_flags |= TF_DELACK;
+                       if (DELAY_ACK(tp, th) && tlen != 0) {
+                               if ((tp->t_flags & TF_DELACK) == 0) {
+                                       tp->t_flags |= TF_DELACK;
+                                       tp->t_timer[TCPT_DELACK] = OFFSET_FROM_START(tp, tcp_delack);
+                               }
+                               tp->t_unacksegs++;
                        }
                        else {
                                tp->t_flags |= TF_ACKNOW;
@@ -1721,50 +2224,37 @@ findpcb:
                         *      SYN_SENT  --> ESTABLISHED
                         *      SYN_SENT* --> FIN_WAIT_1
                         */
+                       tp->t_starttime = tcp_now;
                        if (tp->t_flags & TF_NEEDFIN) {
+                               DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp,
+                                       struct tcpcb *, tp, int32_t, TCPS_FIN_WAIT_1);
                                tp->t_state = TCPS_FIN_WAIT_1;
                                tp->t_flags &= ~TF_NEEDFIN;
                                thflags &= ~TH_SYN;
                        } else {
+                               DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp,
+                                       struct tcpcb *, tp, int32_t, TCPS_ESTABLISHED);
                                tp->t_state = TCPS_ESTABLISHED;
-                               tp->t_timer[TCPT_KEEP] = TCP_KEEPIDLE(tp);
+                               tp->t_timer[TCPT_KEEP] = OFFSET_FROM_START(tp, TCP_KEEPIDLE(tp));
+                               if (nstat_collect)
+                                       nstat_route_connect_success(tp->t_inpcb->inp_route.ro_rt);
                        }
+                       isconnected = TRUE;
                } else {
-               /*
-                *  Received initial SYN in SYN-SENT[*] state => simul-
-                *  taneous open.  If segment contains CC option and there is
-                *  a cached CC, apply TAO test; if it succeeds, connection is
-                *  half-synchronized.  Otherwise, do 3-way handshake:
-                *        SYN-SENT -> SYN-RECEIVED
-                *        SYN-SENT* -> SYN-RECEIVED*
-                *  If there was no CC option, clear cached CC value.
-                */
+                       /*
+                        *  Received initial SYN in SYN-SENT[*] state => simul-
+                        *  taneous open.  If segment contains CC option and there is
+                        *  a cached CC, apply TAO test; if it succeeds, connection is
+                        *  half-synchronized.  Otherwise, do 3-way handshake:
+                        *        SYN-SENT -> SYN-RECEIVED
+                        *        SYN-SENT* -> SYN-RECEIVED*
+                        */
                        tp->t_flags |= TF_ACKNOW;
                        tp->t_timer[TCPT_REXMT] = 0;
-                       if (to.to_flag & TOF_CC) {
-                               if (taop->tao_cc != 0 &&
-                                   CC_GT(to.to_cc, taop->tao_cc)) {
-                                       /*
-                                        * update cache and make transition:
-                                        *        SYN-SENT -> ESTABLISHED*
-                                        *        SYN-SENT* -> FIN-WAIT-1*
-                                        */
-                                       taop->tao_cc = to.to_cc;
-                                       if (tp->t_flags & TF_NEEDFIN) {
-                                               tp->t_state = TCPS_FIN_WAIT_1;
-                                               tp->t_flags &= ~TF_NEEDFIN;
-                                       } else {
-                                               tp->t_state = TCPS_ESTABLISHED;
-                                               tp->t_timer[TCPT_KEEP] = TCP_KEEPIDLE(tp);
-                                       }
-                                       tp->t_flags |= TF_NEEDSYN;
-                               } else
-                                       tp->t_state = TCPS_SYN_RECEIVED;
-                       } else {
-                               /* CC.NEW or no option => invalidate cache */
-                               taop->tao_cc = 0;
-                               tp->t_state = TCPS_SYN_RECEIVED;
-                       }
+                       DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp,
+                               struct tcpcb *, tp, int32_t, TCPS_SYN_RECEIVED);
+                       tp->t_state = TCPS_SYN_RECEIVED;
+
                }
 
 trimthenstep6:
@@ -1796,36 +2286,13 @@ trimthenstep6:
                goto step6;
        /*
         * If the state is LAST_ACK or CLOSING or TIME_WAIT:
-        *      if segment contains a SYN and CC [not CC.NEW] option:
-        *              if state == TIME_WAIT and connection duration > MSL,
-        *                  drop packet and send RST;
-        *
-        *              if SEG.CC > CCrecv then is new SYN, and can implicitly
-        *                  ack the FIN (and data) in retransmission queue.
-        *                  Complete close and delete TCPCB.  Then reprocess
-        *                  segment, hoping to find new TCPCB in LISTEN state;
+        *      do normal processing.
         *
-        *              else must be old SYN; drop it.
-        *      else do normal processing.
+        * NB: Leftover from RFC1644 T/TCP.  Cases to be reused later.
         */
        case TCPS_LAST_ACK:
        case TCPS_CLOSING:
        case TCPS_TIME_WAIT:
-               if ((thflags & TH_SYN) &&
-                   (to.to_flag & TOF_CC) && tp->cc_recv != 0) {
-                       if (tp->t_state == TCPS_TIME_WAIT &&
-                                       tp->t_starttime > tcp_msl) {
-                               rstreason = BANDLIM_UNLIMITED;
-                               goto dropwithreset;
-                       }
-                       if (CC_GT(to.to_cc, tp->cc_recv)) {
-                               tp = tcp_close(tp);
-                               tcp_unlock(so, 1, 50);
-                               goto findpcb;
-                       }
-                       else
-                               goto drop;
-               }
                break;  /* continue normal processing */
 
        /* Received a SYN while connection is already established.
@@ -1867,6 +2334,12 @@ trimthenstep6:
         *   echo of our outgoing acknowlegement numbers, but some hosts
         *   send a reset with the sequence number at the rightmost edge
         *   of our receive window, and we have to handle this case.
+        * Note 2: Paul Watson's paper "Slipping in the Window" has shown
+        *   that brute force RST attacks are possible.  To combat this,
+        *   we use a much stricter check while in the ESTABLISHED state,
+        *   only accepting RSTs where the sequence number is equal to
+        *   last_ack_sent.  In all other states (the states in which a
+        *   RST is more likely), the more permissive check is used.
         * If we have multiple segments in flight, the intial reset
         * segment sequence numbers will be to the left of last_ack_sent,
         * but they will eventually catch up.
@@ -1887,17 +2360,25 @@ trimthenstep6:
         *    SYN_RECEIVED STATE:
         *      If passive open, return to LISTEN state.
         *      If active open, inform user that connection was refused.
-        *    ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES:
+        *    ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
         *      Inform user that connection was reset, and close tcb.
         *    CLOSING, LAST_ACK STATES:
         *      Close the tcb.
         *    TIME_WAIT STATE:
         *      Drop the segment - see Stevens, vol. 2, p. 964 and
         *      RFC 1337.
+        *
+        *      Radar 4803931: Allows for the case where we ACKed the FIN but
+        *                     there is already a RST in flight from the peer.
+        *                     In that case, accept the RST for non-established
+        *                     state if it's one off from last_ack_sent.
+
         */
        if (thflags & TH_RST) {
-               if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
-                   SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
+               if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
+                   SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) ||
+                   (tp->rcv_wnd == 0 && 
+                       ((tp->last_ack_sent == th->th_seq) || ((tp->last_ack_sent -1) == th->th_seq)))) {
                        switch (tp->t_state) {
 
                        case TCPS_SYN_RECEIVED:
@@ -1905,6 +2386,10 @@ trimthenstep6:
                                goto close;
 
                        case TCPS_ESTABLISHED:
+                               if (tp->last_ack_sent != th->th_seq) {
+                                       tcpstat.tcps_badrst++;
+                                       goto drop;
+                               }
                        case TCPS_FIN_WAIT_1:
                        case TCPS_CLOSE_WAIT:
                                /*
@@ -1914,6 +2399,8 @@ trimthenstep6:
                                so->so_error = ECONNRESET;
                        close:
                                postevent(so, 0, EV_RESET);
+                               DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp,
+                                       struct tcpcb *, tp, int32_t, TCPS_CLOSED);
                                tp->t_state = TCPS_CLOSED;
                                tcpstat.tcps_drops++;
                                tp = tcp_close(tp);
@@ -1931,14 +2418,11 @@ trimthenstep6:
                goto drop;
        }
 
-#if 1
-       lck_mtx_assert(((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED);
-#endif
        /*
         * RFC 1323 PAWS: If we have a timestamp reply on this segment
         * and it's less than ts_recent, drop it.
         */
-       if ((to.to_flag & TOF_TS) != 0 && tp->ts_recent &&
+       if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
            TSTMP_LT(to.to_tsval, tp->ts_recent)) {
 
                /* Check to see if ts_recent is over 24 days old.  */
@@ -1959,20 +2443,18 @@ trimthenstep6:
                        tcpstat.tcps_rcvduppack++;
                        tcpstat.tcps_rcvdupbyte += tlen;
                        tcpstat.tcps_pawsdrop++;
-                       goto dropafterack;
+                       if (nstat_collect) {
+                               nstat_route_rx(tp->t_inpcb->inp_route.ro_rt, 1, tlen, NSTAT_RX_FLAG_DUPLICATE);
+                               locked_add_64(&inp->inp_stat->rxpackets, 1);
+                               locked_add_64(&inp->inp_stat->rxbytes, tlen);
+                               tp->t_stat.rxduplicatebytes += tlen;
+                       }
+                       if (tlen)
+                               goto dropafterack;
+                       goto drop;
                }
        }
 
-       /*
-        * T/TCP mechanism
-        *   If T/TCP was negotiated and the segment doesn't have CC,
-        *   or if its CC is wrong then drop the segment.
-        *   RST segments do not have to comply with this.
-        */
-       if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) &&
-           ((to.to_flag & TOF_CC) == 0 || tp->cc_recv != to.to_cc))
-               goto dropafterack;
-
        /*
         * In the SYN-RECEIVED state, validate that the packet belongs to
         * this connection before trimming the data to fit the receive
@@ -2020,6 +2502,12 @@ trimthenstep6:
                        tcpstat.tcps_rcvpartduppack++;
                        tcpstat.tcps_rcvpartdupbyte += todrop;
                }
+               if (nstat_collect) {
+                       nstat_route_rx(tp->t_inpcb->inp_route.ro_rt, 1, todrop, NSTAT_RX_FLAG_DUPLICATE);
+                       locked_add_64(&inp->inp_stat->rxpackets, 1);
+                       locked_add_64(&inp->inp_stat->rxbytes, todrop);
+                       tp->t_stat.rxduplicatebytes += todrop;
+               }
                drop_hdrlen += todrop;  /* drop from the top afterwards */
                th->th_seq += todrop;
                tlen -= todrop;
@@ -2088,11 +2576,25 @@ trimthenstep6:
        /*
         * If last ACK falls within this segment's sequence numbers,
         * record its timestamp.
-        * NOTE that the test is modified according to the latest
-        * proposal of the tcplw@cray.com list (Braden 1993/04/26).
+        * NOTE: 
+        * 1) That the test incorporates suggestions from the latest
+        *    proposal of the tcplw@cray.com list (Braden 1993/04/26).
+        * 2) That updating only on newer timestamps interferes with
+        *    our earlier PAWS tests, so this check should be solely
+        *    predicated on the sequence space of this segment.
+        * 3) That we modify the segment boundary check to be 
+        *        Last.ACK.Sent <= SEG.SEQ + SEG.Len  
+        *    instead of RFC1323's
+        *        Last.ACK.Sent < SEG.SEQ + SEG.Len,
+        *    This modified check allows us to overcome RFC1323's
+        *    limitations as described in Stevens TCP/IP Illustrated
+        *    Vol. 2 p.869. In such cases, we can still calculate the
+        *    RTT correctly when RCV.NXT == Last.ACK.Sent.
         */
-       if ((to.to_flag & TOF_TS) != 0 &&
-           SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
+       if ((to.to_flags & TOF_TS) != 0 &&
+           SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
+           SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen +
+               ((thflags & (TH_SYN|TH_FIN)) != 0))) {
                tp->ts_recent_age = tcp_now;
                tp->ts_recent = to.to_tsval;
        }
@@ -2117,6 +2619,8 @@ trimthenstep6:
                if (tp->t_state == TCPS_SYN_RECEIVED ||
                    (tp->t_flags & TF_NEEDSYN))
                        goto step6;
+               else if (tp->t_flags & TF_ACKNOW)
+                       goto dropafterack;
                else
                        goto drop;
        }
@@ -2134,44 +2638,46 @@ trimthenstep6:
        case TCPS_SYN_RECEIVED:
 
                tcpstat.tcps_connects++;
-               soisconnected(so);
 
                /* Do window scaling? */
                if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
                        (TF_RCVD_SCALE|TF_REQ_SCALE)) {
                        tp->snd_scale = tp->requested_s_scale;
                        tp->rcv_scale = tp->request_r_scale;
+                       tp->snd_wnd = th->th_win << tp->snd_scale;
+                       tiwin = tp->snd_wnd;
                }
-               /*
-                * Upon successful completion of 3-way handshake,
-                * update cache.CC if it was undefined, pass any queued
-                * data to the user, and advance state appropriately.
-                */
-               if ((taop = tcp_gettaocache(inp)) != NULL &&
-                   taop->tao_cc == 0)
-                       taop->tao_cc = tp->cc_recv;
-
                /*
                 * Make transitions:
                 *      SYN-RECEIVED  -> ESTABLISHED
                 *      SYN-RECEIVED* -> FIN-WAIT-1
                 */
+               tp->t_starttime = tcp_now;
                if (tp->t_flags & TF_NEEDFIN) {
+                       DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp,
+                               struct tcpcb *, tp, int32_t, TCPS_FIN_WAIT_1);
                        tp->t_state = TCPS_FIN_WAIT_1;
                        tp->t_flags &= ~TF_NEEDFIN;
                } else {
+                       DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp,
+                               struct tcpcb *, tp, int32_t, TCPS_ESTABLISHED);
                        tp->t_state = TCPS_ESTABLISHED;
-                       tp->t_timer[TCPT_KEEP] = TCP_KEEPIDLE(tp);
+                       tp->t_timer[TCPT_KEEP] = OFFSET_FROM_START(tp, TCP_KEEPIDLE(tp));
+                       if (nstat_collect)
+                               nstat_route_connect_success(tp->t_inpcb->inp_route.ro_rt);
                }
                /*
                 * If segment contains data or ACK, will call tcp_reass()
                 * later; if not, do so now to pass queued data to user.
                 */
                if (tlen == 0 && (thflags & TH_FIN) == 0)
-                       (void) tcp_reass(tp, (struct tcphdr *)0, 0,
+                       (void) tcp_reass(tp, (struct tcphdr *)0, &tlen,
                            (struct mbuf *)0);
                tp->snd_wl1 = th->th_seq - 1;
-               /* fall into ... */
+
+               /* FALLTHROUGH */
+
+               isconnected = TRUE;
 
        /*
         * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
@@ -2188,7 +2694,13 @@ trimthenstep6:
        case TCPS_CLOSING:
        case TCPS_LAST_ACK:
        case TCPS_TIME_WAIT:
-
+               if (SEQ_GT(th->th_ack, tp->snd_max)) {
+                       tcpstat.tcps_rcvacktoomuch++;
+                       goto dropafterack;
+               }
+               if (tp->sack_enable &&
+                   (to.to_nsacks > 0 || !TAILQ_EMPTY(&tp->snd_holes)))
+                       tcp_sack_doack(tp, &to, th->th_ack);
                if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
                        if (tlen == 0 && tiwin == tp->snd_wnd) {
                                tcpstat.tcps_rcvdupack++;
@@ -2219,38 +2731,90 @@ trimthenstep6:
                                if (tp->t_timer[TCPT_REXMT] == 0 ||
                                    th->th_ack != tp->snd_una)
                                        tp->t_dupacks = 0;
-                               else if (++tp->t_dupacks == tcprexmtthresh) {
-                                       tcp_seq onxt = tp->snd_nxt;
-                                       u_int win =
-                                           min(tp->snd_wnd, tp->snd_cwnd) / 2 /
-                                               tp->t_maxseg;
-                                       if (tcp_do_newreno && SEQ_LT(th->th_ack,
-                                           tp->snd_recover)) {
-                                               /* False retransmit, should not
-                                                * cut window
+                               else if (++tp->t_dupacks > tcprexmtthresh ||
+                                         IN_FASTRECOVERY(tp)) {
+                                       if (tp->sack_enable && IN_FASTRECOVERY(tp)) {
+                                               int awnd;
+                                               
+                                               /*
+                                                * Compute the amount of data in flight first.
+                                                * We can inject new data into the pipe iff 
+                                                * we have less than 1/2 the original window's  
+                                                * worth of data in flight.
                                                 */
+                                               awnd = (tp->snd_nxt - tp->snd_fack) +
+                                                       tp->sackhint.sack_bytes_rexmit;
+                                               if (awnd < tp->snd_ssthresh) {
+                                                       tp->snd_cwnd += tp->t_maxseg;
+                                                       if (tp->snd_cwnd > tp->snd_ssthresh)
+                                                               tp->snd_cwnd = tp->snd_ssthresh;
+                                               }
+                                       } else
                                                tp->snd_cwnd += tp->t_maxseg;
-                                               tp->t_dupacks = 0;
-                                               (void) tcp_output(tp);
-                                               goto drop;
+
+                                       DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp,
+                                               struct tcpcb *, tp, struct tcphdr *, th,
+                                               int32_t, TCP_CC_IN_FASTRECOVERY);
+
+                                       (void) tcp_output(tp);
+                                       goto drop;
+                               } else if (tp->t_dupacks == tcprexmtthresh) {
+                                       tcp_seq onxt = tp->snd_nxt;
+
+                                       /*
+                                        * If we're doing sack, check to
+                                        * see if we're already in sack
+                                        * recovery. If we're not doing sack,
+                                        * check to see if we're in newreno
+                                        * recovery.
+                                        */
+                                       if (tp->sack_enable) {
+                                               if (IN_FASTRECOVERY(tp)) {
+                                                       tp->t_dupacks = 0;
+                                                       break;
+                                               }
+                                       } else {
+                                               if (SEQ_LEQ(th->th_ack,
+                                                   tp->snd_recover)) {
+                                                       tp->t_dupacks = 0;
+                                                       break;
+                                               }
                                        }
-                                       if (win < 2)
-                                               win = 2;
-                                       tp->snd_ssthresh = win * tp->t_maxseg;
+                                       
+                                       /*
+                                        * If the current tcp cc module has 
+                                        * defined a hook for tasks to run
+                                        * before entering FR, call it
+                                        */
+                                       if (CC_ALGO(tp)->pre_fr != NULL)
+                                               CC_ALGO(tp)->pre_fr(tp, th);
+                                       ENTER_FASTRECOVERY(tp);
                                        tp->snd_recover = tp->snd_max;
                                        tp->t_timer[TCPT_REXMT] = 0;
                                        tp->t_rtttime = 0;
+                                       tp->ecn_flags |= TE_SENDCWR;
+                                       if (tp->sack_enable) {
+                                               tcpstat.tcps_sack_recovery_episode++;
+                                               tp->sack_newdata = tp->snd_nxt;
+                                               tp->snd_cwnd = tp->t_maxseg;
+
+                                               DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp,
+                                                       struct tcpcb *, tp, struct tcphdr *, th,
+                                                       int32_t, TCP_CC_ENTER_FASTRECOVERY);
+
+                                               (void) tcp_output(tp);
+                                               goto drop;
+                                       }
                                        tp->snd_nxt = th->th_ack;
                                        tp->snd_cwnd = tp->t_maxseg;
                                        (void) tcp_output(tp);
                                        tp->snd_cwnd = tp->snd_ssthresh +
-                                              tp->t_maxseg * tp->t_dupacks;
+                                            tp->t_maxseg * tp->t_dupacks;
                                        if (SEQ_GT(onxt, tp->snd_nxt))
                                                tp->snd_nxt = onxt;
-                                       goto drop;
-                               } else if (tp->t_dupacks > tcprexmtthresh) {
-                                       tp->snd_cwnd += tp->t_maxseg;
-                                       (void) tcp_output(tp);
+                                       DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp,
+                                               struct tcpcb *, tp, struct tcphdr *, th,
+                                               int32_t, TCP_CC_ENTER_FASTRECOVERY);
                                        goto drop;
                                }
                        } else
@@ -2261,36 +2825,37 @@ trimthenstep6:
                 * If the congestion window was inflated to account
                 * for the other side's cached packets, retract it.
                 */
-               if (tcp_do_newreno == 0) {
-                        if (tp->t_dupacks >= tcprexmtthresh &&
-                                tp->snd_cwnd > tp->snd_ssthresh)
-                                tp->snd_cwnd = tp->snd_ssthresh;
-                        tp->t_dupacks = 0;
-                } else if (tp->t_dupacks >= tcprexmtthresh &&
-                   !tcp_newreno(tp, th)) {
-                        /*
-                         * Window inflation should have left us with approx.
-                         * snd_ssthresh outstanding data.  But in case we
-                         * would be inclined to send a burst, better to do
-                         * it via the slow start mechanism.
-                         */
-                       if (SEQ_GT(th->th_ack + tp->snd_ssthresh, tp->snd_max))
-                                tp->snd_cwnd =
-                                   tp->snd_max - th->th_ack + tp->t_maxseg;
-                       else
-                               tp->snd_cwnd = tp->snd_ssthresh;
-                        tp->t_dupacks = 0;
-                }
+               if (IN_FASTRECOVERY(tp)) {
+                       if (SEQ_LT(th->th_ack, tp->snd_recover)) {
+                               if (tp->sack_enable)
+                                       tcp_sack_partialack(tp, th);
+                               else
+                                       tcp_newreno_partial_ack(tp, th);                        
+                               
+                               DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp,
+                                       struct tcpcb *, tp, struct tcphdr *, th,
+                                       int32_t, TCP_CC_PARTIAL_ACK);
+                       } else {
+                               EXIT_FASTRECOVERY(tp);
+                               if (CC_ALGO(tp)->post_fr != NULL)
+                                       CC_ALGO(tp)->post_fr(tp, th);
+                               tp->t_dupacks = 0;
 
-               if (tp->t_dupacks < tcprexmtthresh)
+                               DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp,
+                                       struct tcpcb *, tp, struct tcphdr *, th,
+                                       int32_t, TCP_CC_EXIT_FASTRECOVERY);
+                       }
+               } else {
+                       /*
+                        * We were not in fast recovery. Reset the duplicate ack
+                        * counter.
+                        */
                        tp->t_dupacks = 0;
-
-               if (SEQ_GT(th->th_ack, tp->snd_max)) {
-                       tcpstat.tcps_rcvacktoomuch++;
-                       goto dropafterack;
                }
+
+
                /*
-                *  If we reach this point, ACK is not a duplicate,
+                * If we reach this point, ACK is not a duplicate,
                 *     i.e., it ACKs something we sent.
                 */
                if (tp->t_flags & TF_NEEDSYN) {
@@ -2323,11 +2888,22 @@ process_ACK:
                 * original cwnd and ssthresh, and proceed to transmit where
                 * we left off.
                 */
-               if (tp->t_rxtshift == 1 && tcp_now < tp->t_badrxtwin) {
+               if (tp->t_rxtshift == 1 && 
+                       TSTMP_LT(tcp_now, tp->t_badrxtwin)) {
+                       ++tcpstat.tcps_sndrexmitbad;
                        tp->snd_cwnd = tp->snd_cwnd_prev;
                        tp->snd_ssthresh = tp->snd_ssthresh_prev;
+                       tp->snd_recover = tp->snd_recover_prev;
+                       if (tp->t_flags & TF_WASFRECOVERY)
+                               ENTER_FASTRECOVERY(tp);
                        tp->snd_nxt = tp->snd_max;
                        tp->t_badrxtwin = 0;    /* XXX probably not required */ 
+                       tp->t_rxtshift = 0;
+                       tp->rxt_start = 0;
+
+                       DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp,
+                               struct tcpcb *, tp, struct tcphdr *, th,
+                               int32_t, TCP_CC_BAD_REXMT_RECOVERY);
                }
 
                /*
@@ -2339,11 +2915,18 @@ process_ACK:
                 * timer backoff (cf., Phil Karn's retransmit alg.).
                 * Recompute the initial retransmit timer.
                 * Also makes sure we have a valid time stamp in hand
+                *
+                * Some boxes send broken timestamp replies
+                * during the SYN+ACK phase, ignore
+                * timestamps of 0 or we could calculate a
+                * huge RTT and blow up the retransmit timer.
                 */
-               if (((to.to_flag & TOF_TS) != 0) && (to.to_tsecr != 0))
-                       tcp_xmit_timer(tp, tcp_now - to.to_tsecr + 1);
-               else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq))
-                       tcp_xmit_timer(tp, tp->t_rtttime);
+               if (((to.to_flags & TOF_TS) != 0) && (to.to_tsecr != 0) &&
+                       TSTMP_GEQ(tcp_now, to.to_tsecr)) {
+                       tcp_xmit_timer(tp, tcp_now - to.to_tsecr);
+               } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
+                       tcp_xmit_timer(tp, tcp_now - tp->t_rtttime);
+               }
 
                /*
                 * If all outstanding data is acked, stop retransmit
@@ -2355,7 +2938,7 @@ process_ACK:
                        tp->t_timer[TCPT_REXMT] = 0;
                        needoutput = 1;
                } else if (tp->t_timer[TCPT_PERSIST] == 0)
-                       tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
+                       tp->t_timer[TCPT_REXMT] = OFFSET_FROM_START(tp, tp->t_rxtcur);
 
                /*
                 * If no data (only SYN) was ACK'd,
@@ -2364,26 +2947,35 @@ process_ACK:
                if (acked == 0)
                        goto step6;
 
-               /*
-                * When new data is acked, open the congestion window.
-                * If the window gives us less than ssthresh packets
-                * in flight, open exponentially (maxseg per packet).
-                * Otherwise open linearly: maxseg per window
-                * (maxseg^2 / cwnd per packet).
-                */
-               {
-               register u_int cw = tp->snd_cwnd;
-               register u_int incr = tp->t_maxseg;
+               if ((thflags & TH_ECE) != 0 &&
+                       (tp->ecn_flags & TE_SETUPSENT) != 0) {
+                       /*
+                        * Reduce the congestion window if we haven't done so.
+                        */
+                       if (!tp->sack_enable && !IN_FASTRECOVERY(tp) &&
+                               SEQ_GEQ(th->th_ack, tp->snd_recover)) {
+                               tcp_reduce_congestion_window(tp, th);
+                               DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp,
+                                       struct tcpcb *, tp, struct tcphdr *, th, 
+                                       int32_t, TCP_CC_ECN_RCVD);
+                       }
+               }
 
-               if (cw > tp->snd_ssthresh)
-                       incr = incr * incr / cw;
                /*
-                * If t_dupacks != 0 here, it indicates that we are still
-                * in NewReno fast recovery mode, so we leave the congestion
-                * window alone.
+                * When new data is acked, open the congestion window.
+                * The specifics of how this is achieved are up to the
+                * congestion control algorithm in use for this connection.
+                *
+                * The calculations in this function assume that snd_una is
+                * not updated yet.
                 */
-               if (tcp_do_newreno == 0 || tp->t_dupacks == 0)
-                       tp->snd_cwnd = min(cw + incr,TCP_MAXWIN<<tp->snd_scale);
+               if (!IN_FASTRECOVERY(tp)) {
+                       if (CC_ALGO(tp)->ack_rcvd != NULL)
+                               CC_ALGO(tp)->ack_rcvd(tp, th);
+                       
+                       DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp,
+                               struct tcpcb *, tp, struct tcphdr *, th,
+                               int32_t, TCP_CC_ACK_RCVD);
                }
                if (acked > so->so_snd.sb_cc) {
                        tp->snd_wnd -= so->so_snd.sb_cc;
@@ -2394,17 +2986,29 @@ process_ACK:
                        tp->snd_wnd -= acked;
                        ourfinisacked = 0;
                }
-               sowwakeup(so);
                /* detect una wraparound */
-               if (SEQ_GEQ(tp->snd_una, tp->snd_recover) &&
-                   SEQ_LT(th->th_ack, tp->snd_recover))
-                       tp->snd_recover = th->th_ack;
-               if (SEQ_GT(tp->snd_una, tp->snd_high) &&
-                   SEQ_LEQ(th->th_ack, tp->snd_high))
-                       tp->snd_high = th->th_ack - 1;
+               if ( !IN_FASTRECOVERY(tp) &&
+                   SEQ_GT(tp->snd_una, tp->snd_recover) &&
+                   SEQ_LEQ(th->th_ack, tp->snd_recover))
+                       tp->snd_recover = th->th_ack - 1;
+
+               if (IN_FASTRECOVERY(tp) &&
+                   SEQ_GEQ(th->th_ack, tp->snd_recover))
+                       EXIT_FASTRECOVERY(tp);
+
                tp->snd_una = th->th_ack;
+               if (tp->sack_enable) {
+                       if (SEQ_GT(tp->snd_una, tp->snd_recover))
+                               tp->snd_recover = tp->snd_una;
+               }
                if (SEQ_LT(tp->snd_nxt, tp->snd_una))
                        tp->snd_nxt = tp->snd_una;
+                       
+               /*
+                * sowwakeup must happen after snd_una, et al. are updated so that
+                * the sequence numbers are in sync with so_snd
+                */
+               sowwakeup(so);
 
                switch (tp->t_state) {
 
@@ -2423,13 +3027,16 @@ process_ACK:
                                 * we'll hang forever.
                                 */
                                if (so->so_state & SS_CANTRCVMORE) {
-                                       soisdisconnected(so);
-                                       tp->t_timer[TCPT_2MSL] = tcp_maxidle;
+                                       add_to_time_wait(tp, tcp_maxidle);
+                                       isconnected = FALSE;
+                                       isdisconnected = TRUE;
                                }
-                               add_to_time_wait(tp);
+                               DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp,
+                                       struct tcpcb *, tp, int32_t, TCPS_FIN_WAIT_2);
                                tp->t_state = TCPS_FIN_WAIT_2;
-                               goto drop;
+                               /* fall through and make sure we also recognize data ACKed with the FIN */
                        }
+                       tp->t_flags |= TF_ACKNOW;
                        break;
 
                /*
@@ -2440,18 +3047,20 @@ process_ACK:
                 */
                case TCPS_CLOSING:
                        if (ourfinisacked) {
+                               DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp,
+                                       struct tcpcb *, tp, int32_t, TCPS_TIME_WAIT);
                                tp->t_state = TCPS_TIME_WAIT;
                                tcp_canceltimers(tp);
                                /* Shorten TIME_WAIT [RFC-1644, p.28] */
                                if (tp->cc_recv != 0 &&
-                                   tp->t_starttime < tcp_msl)
-                                       tp->t_timer[TCPT_2MSL] =
-                                           tp->t_rxtcur * TCPTV_TWTRUNC;
+                                   ((int)(tcp_now - tp->t_starttime)) < tcp_msl)
+                                       add_to_time_wait(tp, tp->t_rxtcur * TCPTV_TWTRUNC);
                                else
-                                       tp->t_timer[TCPT_2MSL] = 2 * tcp_msl;
-                               add_to_time_wait(tp);
-                               soisdisconnected(so);
+                                       add_to_time_wait(tp, 2 * tcp_msl);
+                               isconnected = FALSE;
+                               isdisconnected = TRUE;
                        }
+                       tp->t_flags |= TF_ACKNOW;
                        break;
 
                /*
@@ -2473,8 +3082,7 @@ process_ACK:
                 * it and restart the finack timer.
                 */
                case TCPS_TIME_WAIT:
-                       tp->t_timer[TCPT_2MSL] = 2 * tcp_msl;
-                       add_to_time_wait(tp);
+                       add_to_time_wait(tp, 2 * tcp_msl);
                        goto dropafterack;
                }
        }
@@ -2547,14 +3155,14 @@ step6:
                 * but if two URG's are pending at once, some out-of-band
                 * data may creep in... ick.
                 */
-               if (th->th_urp <= (u_long)tlen
+               if (th->th_urp <= (u_int32_t)tlen
 #if SO_OOBINLINE
                     && (so->so_options & SO_OOBINLINE) == 0
 #endif
                     )
                        tcp_pulloutofband(so, th, m,
                                drop_hdrlen);   /* hdr drop is delayed */
-       } else
+       } else {
                /*
                 * If no out of band data is expected,
                 * pull receive urgent pointer along
@@ -2562,8 +3170,27 @@ step6:
                 */
                if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
                        tp->rcv_up = tp->rcv_nxt;
-dodata:                                                        /* XXX */
+       }
+dodata:
+
+       /* Set socket's connect or disconnect state correcly before doing data.
+        * The following might unlock the socket if there is an upcall or a socket
+        * filter.
+        */
+       if (isconnected) {
+               soisconnected(so);
+       } else if (isdisconnected) {
+               soisdisconnected(so);
+       }
 
+       /* Let's check the state of pcb just to make sure that it did not get closed 
+        * when we unlocked above
+        */
+       if (inp->inp_state == INPCB_STATE_DEAD) {
+               /* Just drop the packet that we are processing and return */
+               goto drop;
+       }
+       
        /*
         * Process the segment text, merging it into the TCP sequencing queue,
         * and arranging for acknowledgment of receipt if necessary.
@@ -2572,24 +3199,32 @@ dodata:                                                 /* XXX */
         * case PRU_RCVD).  If a FIN has already been received on this
         * connection then we just ignore the text.
         */
-       if ((tlen || (thflags&TH_FIN)) &&
+       if ((tlen || (thflags & TH_FIN)) &&
            TCPS_HAVERCVDFIN(tp->t_state) == 0) {
+               tcp_seq save_start = th->th_seq;
+               tcp_seq save_end = th->th_seq + tlen;
                m_adj(m, drop_hdrlen);  /* delayed header drop */
                /*
-                * Insert segment which inludes th into reassembly queue of tcp with
-                * control block tp.  Return TH_FIN if reassembly now includes
-                * a segment with FIN.  This handle the common case inline (segment
-                * is the next to be received on an established connection, and the
-                * queue is empty), avoiding linkage into and removal from the queue
-                * and repetition of various conversions.
-                * Set DELACK for segments received in order, but ack immediately
-                * when segments are out of order (so fast retransmit can work).
+                * Insert segment which includes th into TCP reassembly queue
+                * with control block tp.  Set thflags to whether reassembly now
+                * includes a segment with FIN.  This handles the common case
+                * inline (segment is the next to be received on an established
+                * connection, and the queue is empty), avoiding linkage into
+                * and removal from the queue and repetition of various
+                * conversions.
+                * Set DELACK for segments received in order, but ack
+                * immediately when segments are out of order (so
+                * fast retransmit can work).
                 */
                if (th->th_seq == tp->rcv_nxt &&
                    LIST_EMPTY(&tp->t_segq) &&
                    TCPS_HAVEESTABLISHED(tp->t_state)) {
-                       if (DELAY_ACK(tp) && ((tp->t_flags & TF_ACKNOW) == 0)) {
-                               tp->t_flags |= TF_DELACK;
+                       if (DELAY_ACK(tp, th) && ((tp->t_flags & TF_ACKNOW) == 0)) {
+                               if ((tp->t_flags & TF_DELACK) == 0) {
+                                       tp->t_flags |= TF_DELACK;
+                                       tp->t_timer[TCPT_DELACK] = OFFSET_FROM_START(tp, tcp_delack);
+                               }
+                               tp->t_unacksegs++;
                        }         
                        else {
                                tp->t_flags |= TF_ACKNOW;
@@ -2598,14 +3233,22 @@ dodata:                                                 /* XXX */
                        thflags = th->th_flags & TH_FIN;
                        tcpstat.tcps_rcvpack++;
                        tcpstat.tcps_rcvbyte += tlen;
+                       if (nstat_collect) {
+                               locked_add_64(&inp->inp_stat->rxpackets, 1);
+                               locked_add_64(&inp->inp_stat->rxbytes, tlen);
+                       }
                        ND6_HINT(tp);
-                       if (sbappend(&so->so_rcv, m))
+                       so_recv_data_stat(so, m, drop_hdrlen);
+                       if (sbappendstream(&so->so_rcv, m))
                                sorwakeup(so);
                } else {
                        thflags = tcp_reass(tp, th, &tlen, m);
                        tp->t_flags |= TF_ACKNOW;
                }
 
+               if (tlen > 0 && tp->sack_enable)
+                       tcp_update_sack_list(tp, save_start, save_end);
+
                if (tp->t_flags & TF_DELACK) 
                {
 #if INET6
@@ -2628,7 +3271,9 @@ dodata:                                                   /* XXX */
                 * our window, in order to estimate the sender's
                 * buffer size.
                 */
-               len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
+               len = (u_int)(so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt));
+               if (len > so->so_rcv.sb_maxused)
+                       so->so_rcv.sb_maxused = len;
        } else {
                m_freem(m);
                thflags &= ~TH_FIN;
@@ -2645,12 +3290,18 @@ dodata:                                                 /* XXX */
                        /*
                         *  If connection is half-synchronized
                         *  (ie NEEDSYN flag on) then delay ACK,
-                        *  so it may be piggybacked when SYN is sent.
-                        *  Otherwise, since we received a FIN then no
-                        *  more input can be expected, send ACK now.
+                        * If connection is half-synchronized
+                        * (ie NEEDSYN flag on) then delay ACK,
+                        * so it may be piggybacked when SYN is sent.
+                        * Otherwise, since we received a FIN then no
+                        * more input can be expected, send ACK now.
                         */
-                       if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) {
-                               tp->t_flags |= TF_DELACK;
+                       if (DELAY_ACK(tp, th) && (tp->t_flags & TF_NEEDSYN)) {
+                               if ((tp->t_flags & TF_DELACK) == 0) {
+                                       tp->t_flags |= TF_DELACK;
+                                       tp->t_timer[TCPT_DELACK] = OFFSET_FROM_START(tp, tcp_delack);
+                               }
+                               tp->t_unacksegs++;
                        }
                        else {
                                tp->t_flags |= TF_ACKNOW;
@@ -2664,8 +3315,10 @@ dodata:                                                  /* XXX */
                 * enter the CLOSE_WAIT state.
                 */
                case TCPS_SYN_RECEIVED:
-                       /*FALLTHROUGH*/
+                       tp->t_starttime = tcp_now;
                case TCPS_ESTABLISHED:
+                       DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp,
+                               struct tcpcb *, tp, int32_t, TCPS_CLOSE_WAIT);
                        tp->t_state = TCPS_CLOSE_WAIT;
                        break;
 
@@ -2674,6 +3327,8 @@ dodata:                                                   /* XXX */
                 * enter the CLOSING state.
                 */
                case TCPS_FIN_WAIT_1:
+                       DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp,
+                               struct tcpcb *, tp, int32_t, TCPS_CLOSING);
                        tp->t_state = TCPS_CLOSING;
                        break;
 
@@ -2683,20 +3338,20 @@ dodata:                                                 /* XXX */
                 * standard timers.
                 */
                case TCPS_FIN_WAIT_2:
+                       DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp,
+                               struct tcpcb *, tp, int32_t, TCPS_TIME_WAIT);
                        tp->t_state = TCPS_TIME_WAIT;
                        tcp_canceltimers(tp);
                        /* Shorten TIME_WAIT [RFC-1644, p.28] */
                        if (tp->cc_recv != 0 &&
-                           tp->t_starttime < tcp_msl) {
-                               tp->t_timer[TCPT_2MSL] =
-                                   tp->t_rxtcur * TCPTV_TWTRUNC;
+                               ((int)(tcp_now - tp->t_starttime)) < tcp_msl) {
+                               add_to_time_wait(tp, tp->t_rxtcur * TCPTV_TWTRUNC);
                                /* For transaction client, force ACK now. */
                                tp->t_flags |= TF_ACKNOW;
+                               tp->t_unacksegs = 0;
                        }
                        else
-                               tp->t_timer[TCPT_2MSL] = 2 * tcp_msl;
-
-                       add_to_time_wait(tp);
+                               add_to_time_wait(tp, 2 * tcp_msl);
                        soisdisconnected(so);
                        break;
 
@@ -2704,8 +3359,7 @@ dodata:                                                   /* XXX */
                 * In TIME_WAIT state restart the 2 MSL time_wait timer.
                 */
                case TCPS_TIME_WAIT:
-                       tp->t_timer[TCPT_2MSL] = 2 * tcp_msl;
-                       add_to_time_wait(tp);
+                       add_to_time_wait(tp, 2 * tcp_msl);
                        break;
                }
        }
@@ -2718,8 +3372,13 @@ dodata:                                                  /* XXX */
        /*
         * Return any desired output.
         */
-       if (needoutput || (tp->t_flags & TF_ACKNOW))
+       if (needoutput || (tp->t_flags & TF_ACKNOW)) {
                (void) tcp_output(tp);
+       }
+
+       tcp_check_timer_state(tp);
+
+       
        tcp_unlock(so, 1, 0);
        KERNEL_DEBUG(DBG_FNC_TCP_INPUT | DBG_FUNC_END,0,0,0,0,0);
        return;
@@ -2754,6 +3413,8 @@ dropafterack:
        m_freem(m);
        tp->t_flags |= TF_ACKNOW;
        (void) tcp_output(tp);
+
+       /* Don't need to check timer state as we should have done it during tcp_output */
        tcp_unlock(so, 1, 0);
        KERNEL_DEBUG(DBG_FNC_TCP_INPUT | DBG_FUNC_END,0,0,0,0,0);
        return;
@@ -2797,22 +3458,22 @@ dropwithreset:
        if (thflags & TH_ACK)
                /* mtod() below is safe as long as hdr dropping is delayed */
                tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
-                           TH_RST);
+                   TH_RST, ifscope, nocell);
        else {
                if (thflags & TH_SYN)
                        tlen++;
                /* mtod() below is safe as long as hdr dropping is delayed */
                tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
-                           (tcp_seq)0, TH_RST|TH_ACK);
+                   (tcp_seq)0, TH_RST|TH_ACK, ifscope, nocell);
        }
        /* destroy temporarily created socket */
        if (dropsocket) {
                (void) soabort(so); 
                tcp_unlock(so, 1, 0);
        }
-       else
-               if ((inp != NULL) && (nosock == 0))
-                       tcp_unlock(so, 1, 0);
+       else if ((inp != NULL) && (nosock == 0)) {
+               tcp_unlock(so, 1, 0);
+       }
        KERNEL_DEBUG(DBG_FNC_TCP_INPUT | DBG_FUNC_END,0,0,0,0,0);
        return;
 dropnosock:
@@ -2832,20 +3493,24 @@ drop:
                (void) soabort(so); 
                tcp_unlock(so, 1, 0);
        }
-       else
-               if (nosock == 0)
-                       tcp_unlock(so, 1, 0);
+       else if (nosock == 0) {
+               tcp_unlock(so, 1, 0);
+       }
        KERNEL_DEBUG(DBG_FNC_TCP_INPUT | DBG_FUNC_END,0,0,0,0,0);
        return;
 }
 
 static void
-tcp_dooptions(tp, cp, cnt, th, to)
+tcp_dooptions(tp, cp, cnt, th, to, input_ifscope)
+/*
+ * Parse TCP options and place in tcpopt.
+ */
        struct tcpcb *tp;
        u_char *cp;
        int cnt;
        struct tcphdr *th;
        struct tcpopt *to;
+       unsigned int input_ifscope;
 {
        u_short mss = 0;
        int opt, optlen;
@@ -2874,7 +3539,11 @@ tcp_dooptions(tp, cp, cnt, th, to)
                        if (!(th->th_flags & TH_SYN))
                                continue;
                        bcopy((char *) cp + 2, (char *) &mss, sizeof(mss));
+
+#if BYTE_ORDER != BIG_ENDIAN
                        NTOHS(mss);
+#endif
+
                        break;
 
                case TCPOPT_WINDOW:
@@ -2889,13 +3558,20 @@ tcp_dooptions(tp, cp, cnt, th, to)
                case TCPOPT_TIMESTAMP:
                        if (optlen != TCPOLEN_TIMESTAMP)
                                continue;
-                       to->to_flag |= TOF_TS;
+                       to->to_flags |= TOF_TS;
                        bcopy((char *)cp + 2,
                            (char *)&to->to_tsval, sizeof(to->to_tsval));
+
+#if BYTE_ORDER != BIG_ENDIAN
                        NTOHL(to->to_tsval);
+#endif
+
                        bcopy((char *)cp + 6,
                            (char *)&to->to_tsecr, sizeof(to->to_tsecr));
+
+#if BYTE_ORDER != BIG_ENDIAN
                        NTOHL(to->to_tsecr);
+#endif
 
                        /*
                         * A timestamp received in a SYN makes
@@ -2907,49 +3583,25 @@ tcp_dooptions(tp, cp, cnt, th, to)
                                tp->ts_recent_age = tcp_now;
                        }
                        break;
-               case TCPOPT_CC:
-                       if (optlen != TCPOLEN_CC)
+               case TCPOPT_SACK_PERMITTED:
+                       if (!tcp_do_sack ||
+                           optlen != TCPOLEN_SACK_PERMITTED)
                                continue;
-                       to->to_flag |= TOF_CC;
-                       bcopy((char *)cp + 2,
-                           (char *)&to->to_cc, sizeof(to->to_cc));
-                       NTOHL(to->to_cc);
-                       /*
-                        * A CC or CC.new option received in a SYN makes
-                        * it ok to send CC in subsequent segments.
-                        */
                        if (th->th_flags & TH_SYN)
-                               tp->t_flags |= TF_RCVD_CC;
+                               to->to_flags |= TOF_SACK;
                        break;
-               case TCPOPT_CCNEW:
-                       if (optlen != TCPOLEN_CC)
+               case TCPOPT_SACK:
+                       if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0)
                                continue;
-                       if (!(th->th_flags & TH_SYN))
-                               continue;
-                       to->to_flag |= TOF_CCNEW;
-                       bcopy((char *)cp + 2,
-                           (char *)&to->to_cc, sizeof(to->to_cc));
-                       NTOHL(to->to_cc);
-                       /*
-                        * A CC or CC.new option received in a SYN makes
-                        * it ok to send CC in subsequent segments.
-                        */
-                       tp->t_flags |= TF_RCVD_CC;
-                       break;
-               case TCPOPT_CCECHO:
-                       if (optlen != TCPOLEN_CC)
-                               continue;
-                       if (!(th->th_flags & TH_SYN))
-                               continue;
-                       to->to_flag |= TOF_CCECHO;
-                       bcopy((char *)cp + 2,
-                           (char *)&to->to_ccecho, sizeof(to->to_ccecho));
-                       NTOHL(to->to_ccecho);
+                       to->to_nsacks = (optlen - 2) / TCPOLEN_SACK;
+                       to->to_sacks = cp + 2;
+                       tcpstat.tcps_sack_rcv_blocks++;
+
                        break;
                }
        }
        if (th->th_flags & TH_SYN)
-               tcp_mss(tp, mss);       /* sets t_maxseg */
+               tcp_mss(tp, mss, input_ifscope);        /* sets t_maxseg */
 }
 
 /*
@@ -2988,6 +3640,36 @@ tcp_pulloutofband(so, th, m, off)
        panic("tcp_pulloutofband");
 }
 
+uint32_t
+get_base_rtt(struct tcpcb *tp) 
+{
+       uint32_t base_rtt = 0, i;
+       for (i = 0; i < N_RTT_BASE; ++i) {
+               if (tp->rtt_hist[i] != 0 &&
+                       (base_rtt == 0 || tp->rtt_hist[i] < base_rtt))
+                       base_rtt = tp->rtt_hist[i];
+       }
+       return base_rtt;
+}
+
+/* Each value of RTT base represents the minimum RTT seen in a minute.
+ * We keep upto N_RTT_BASE minutes worth of history.
+ */
+void
+update_base_rtt(struct tcpcb *tp, uint32_t rtt)
+{
+       if (++tp->rtt_count >= rtt_samples_per_slot) {
+               int i=0;
+               for (i = (N_RTT_BASE-1); i > 0; --i) {
+                       tp->rtt_hist[i] = tp->rtt_hist[i-1];
+               }
+               tp->rtt_hist[0] = rtt;
+               tp->rtt_count = 0;
+       } else {
+               tp->rtt_hist[0] = min(tp->rtt_hist[0], rtt);
+       }
+}
+
 /*
  * Collect new round-trip time estimate
  * and update averages and current timeout.
@@ -3001,15 +3683,26 @@ tcp_xmit_timer(tp, rtt)
 
        tcpstat.tcps_rttupdated++;
        tp->t_rttupdated++;
+
+       if (rtt > 0) {
+               tp->t_rttcur = rtt;
+               update_base_rtt(tp, rtt);
+       }
+
        if (tp->t_srtt != 0) {
                /*
                 * srtt is stored as fixed point with 5 bits after the
-                * binary point (i.e., scaled by 8).  The following magic
+                * binary point (i.e., scaled by 32).  The following magic
                 * is equivalent to the smoothing algorithm in rfc793 with
                 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
-                * point).  Adjust rtt to origin 0.
+                * point).
+                *
+                * Freebsd adjusts rtt to origin 0 by subtracting 1 from the provided
+                * rtt value. This was required because of the way t_rtttime was
+                * initiailised to 1 before. Since we changed t_rtttime to be based on
+                * tcp_now, this extra adjustment is not needed.
                 */
-               delta = ((rtt - 1) << TCP_DELTA_SHIFT)
+               delta = (rtt << TCP_DELTA_SHIFT)
                        - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
 
                if ((tp->t_srtt += delta) <= 0)
@@ -3030,6 +3723,8 @@ tcp_xmit_timer(tp, rtt)
                delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
                if ((tp->t_rttvar += delta) <= 0)
                        tp->t_rttvar = 1;
+               if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
+                   tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
        } else {
                /*
                 * No rtt measurement yet - use the unsmoothed rtt.
@@ -3038,9 +3733,12 @@ tcp_xmit_timer(tp, rtt)
                 */
                tp->t_srtt = rtt << TCP_RTT_SHIFT;
                tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
+               tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
        }
+       nstat_route_rtt(tp->t_inpcb->inp_route.ro_rt, tp->t_srtt, tp->t_rttvar);
        tp->t_rtttime = 0;
        tp->t_rxtshift = 0;
+       tp->rxt_start = 0;
 
        /*
         * the retransmit should happen at rtt + 4 * rttvar.
@@ -3054,7 +3752,8 @@ tcp_xmit_timer(tp, rtt)
         * the minimum feasible timer (which is 2 ticks).
         */
        TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
-                     max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
+               max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX, 
+               TCP_ADD_REXMTSLOP(tp));
 
        /*
         * We received an ack for a packet that wasn't retransmitted;
@@ -3066,6 +3765,38 @@ tcp_xmit_timer(tp, rtt)
        tp->t_softerror = 0;
 }
 
+static inline unsigned int
+tcp_maxmtu(struct rtentry *rt)
+{
+       unsigned int maxmtu;
+
+       RT_LOCK_ASSERT_HELD(rt);
+       if (rt->rt_rmx.rmx_mtu == 0)
+               maxmtu = rt->rt_ifp->if_mtu;
+       else
+               maxmtu = MIN(rt->rt_rmx.rmx_mtu, rt->rt_ifp->if_mtu);
+
+       return (maxmtu);
+}
+
+#if INET6
+static inline unsigned int
+tcp_maxmtu6(struct rtentry *rt)
+{
+       unsigned int maxmtu;
+
+       RT_LOCK_ASSERT_HELD(rt);
+       lck_rw_lock_shared(nd_if_rwlock);
+       if (rt->rt_rmx.rmx_mtu == 0)
+               maxmtu = IN6_LINKMTU(rt->rt_ifp);
+       else
+               maxmtu = MIN(rt->rt_rmx.rmx_mtu, IN6_LINKMTU(rt->rt_ifp));
+       lck_rw_done(nd_if_rwlock);
+
+       return (maxmtu);
+}
+#endif
+
 /*
  * Determine a reasonable value for maxseg size.
  * If the route is known, check route for mtu.
@@ -3090,23 +3821,23 @@ tcp_xmit_timer(tp, rtt)
  * NOTE that this routine is only called when we process an incoming
  * segment, for outgoing segments only tcp_mssopt is called.
  *
- * In case of T/TCP, we call this routine during implicit connection
- * setup as well (offer = -1), to initialize maxseg from the cached
- * MSS of our peer.
  */
 void
-tcp_mss(tp, offer)
+tcp_mss(tp, offer, input_ifscope)
        struct tcpcb *tp;
        int offer;
+       unsigned int input_ifscope;
 {
        register struct rtentry *rt;
        struct ifnet *ifp;
        register int rtt, mss;
-       u_long bufsize;
+       u_int32_t bufsize;
        struct inpcb *inp;
        struct socket *so;
        struct rmxp_tao *taop;
        int origoffer = offer;
+       u_int32_t sb_max_corrected;
+       int isnetlocal = 0;
 #if INET6
        int isipv6;
        int min_protoh;
@@ -3120,12 +3851,31 @@ tcp_mss(tp, offer)
 #else
 #define min_protoh  (sizeof (struct tcpiphdr))
 #endif
+
 #if INET6
-       if (isipv6)
-               rt = tcp_rtlookup6(inp);
+       if (isipv6) {
+               rt = tcp_rtlookup6(inp, input_ifscope);
+               if (rt != NULL &&
+                   (IN6_IS_ADDR_LOOPBACK(&inp->in6p_faddr) ||
+                   IN6_IS_ADDR_LINKLOCAL(&inp->in6p_faddr) ||
+                   rt->rt_gateway->sa_family == AF_LINK ||
+                   in6_localaddr(&inp->in6p_faddr))) {
+                       tp->t_flags |= TF_LOCAL;
+               }
+       }
        else
 #endif /* INET6 */
-       rt = tcp_rtlookup(inp);
+       {
+               rt = tcp_rtlookup(inp, input_ifscope);
+               if (rt != NULL &&
+                   (rt->rt_gateway->sa_family == AF_LINK ||
+                   rt->rt_ifp->if_flags & IFF_LOOPBACK ||
+                   in_localaddr(inp->inp_faddr))) {
+                       tp->t_flags |= TF_LOCAL;
+               }
+       }
+       isnetlocal = (tp->t_flags & TF_LOCAL);
+
        if (rt == NULL) {
                tp->t_maxopd = tp->t_maxseg =
 #if INET6
@@ -3191,12 +3941,14 @@ tcp_mss(tp, offer)
                 * is also a minimum value; this is subject to time.
                 */
                if (rt->rt_rmx.rmx_locks & RTV_RTT)
-                       tp->t_rttmin = rtt / (RTM_RTTUNIT / PR_SLOWHZ);
-               tp->t_srtt = rtt / (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE));
+                       tp->t_rttmin = rtt / (RTM_RTTUNIT / TCP_RETRANSHZ);
+               else
+                       tp->t_rttmin = isnetlocal ? tcp_TCPTV_MIN : TCPTV_REXMTMIN;
+               tp->t_srtt = rtt / (RTM_RTTUNIT / (TCP_RETRANSHZ * TCP_RTT_SCALE));
                tcpstat.tcps_usedrtt++;
                if (rt->rt_rmx.rmx_rttvar) {
                        tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
-                           (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTTVAR_SCALE));
+                           (RTM_RTTUNIT / (TCP_RETRANSHZ * TCP_RTTVAR_SCALE));
                        tcpstat.tcps_usedrttvar++;
                } else {
                        /* default variation is +- 1 rtt */
@@ -3205,34 +3957,30 @@ tcp_mss(tp, offer)
                }
                TCPT_RANGESET(tp->t_rxtcur,
                              ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
-                             tp->t_rttmin, TCPTV_REXMTMAX);
+                             tp->t_rttmin, TCPTV_REXMTMAX, 
+                             TCP_ADD_REXMTSLOP(tp));
        }
-       /*
-        * if there's an mtu associated with the route, use it
-        * else, use the link mtu.
-        */
-       if (rt->rt_rmx.rmx_mtu)
-               mss = rt->rt_rmx.rmx_mtu - min_protoh;
        else
-       {
-               mss =
-#if INET6
-                       (isipv6 ? nd_ifinfo[rt->rt_ifp->if_index].linkmtu :
-#endif
-                        ifp->if_mtu
+               tp->t_rttmin = isnetlocal ? tcp_TCPTV_MIN : TCPTV_REXMTMIN;
+
 #if INET6
-                        )
+       mss = (isipv6 ? tcp_maxmtu6(rt) : tcp_maxmtu(rt));
+#else
+       mss = tcp_maxmtu(rt);
 #endif
-                       - min_protoh;
+       mss -= min_protoh;
+
+       if (rt->rt_rmx.rmx_mtu == 0) {
 #if INET6
                if (isipv6) {
-                       if (!in6_localaddr(&inp->in6p_faddr))
+                       if (!isnetlocal)
                                mss = min(mss, tcp_v6mssdflt);
                } else
 #endif /* INET6 */
-               if (!in_localaddr(inp->inp_faddr))
+               if (!isnetlocal)
                        mss = min(mss, tcp_mssdflt);
        }
+
        mss = min(mss, offer);
        /*
         * maxopd stores the maximum length of data AND options
@@ -3244,18 +3992,20 @@ tcp_mss(tp, offer)
        tp->t_maxopd = mss;
 
        /*
-        * In case of T/TCP, origoffer==-1 indicates, that no segments
-        * were received yet.  In this case we just guess, otherwise
-        * we do the same as before T/TCP.
+        * origoffer==-1 indicates, that no segments were received yet.
+        * In this case we just guess.
         */
-       if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
+       if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
            (origoffer == -1 ||
             (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
                mss -= TCPOLEN_TSTAMP_APPA;
-       if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC &&
-           (origoffer == -1 ||
-            (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC))
-               mss -= TCPOLEN_CC_APPA;
+       tp->t_maxseg = mss;
+
+       /*
+        * Calculate corrected value for sb_max; ensure to upgrade the
+        * numerator for large sb_max values else it will overflow.
+        */
+       sb_max_corrected = (sb_max * (u_int64_t)MCLBYTES) / (MSIZE + MCLBYTES);
 
        /*
         * If there's a pipesize (ie loopback), change the socket
@@ -3272,9 +4022,9 @@ tcp_mss(tp, offer)
        if (bufsize < mss)
                mss = bufsize;
        else {
-               bufsize = roundup(bufsize, mss);
-               if (bufsize > sb_max)
-                       bufsize = sb_max;
+               bufsize = (((bufsize + (u_int64_t)mss - 1) / (u_int64_t)mss) * (u_int64_t)mss);
+               if (bufsize > sb_max_corrected)
+                       bufsize = sb_max_corrected;
                (void)sbreserve(&so->so_snd, bufsize);
        }
        tp->t_maxseg = mss;
@@ -3285,29 +4035,13 @@ tcp_mss(tp, offer)
 #endif
                bufsize = so->so_rcv.sb_hiwat;
        if (bufsize > mss) {
-               bufsize = roundup(bufsize, mss);
-               if (bufsize > sb_max)
-                       bufsize = sb_max;
+               bufsize = (((bufsize + (u_int64_t)mss - 1) / (u_int64_t)mss) * (u_int64_t)mss);
+               if (bufsize > sb_max_corrected)
+                       bufsize = sb_max_corrected;
                (void)sbreserve(&so->so_rcv, bufsize);
        }
 
-       /*
-        * Set the slow-start flight size depending on whether this
-        * is a local network or not.
-        */
-       if (
-#if INET6
-           (isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
-           (!isipv6 &&
-#endif
-            in_localaddr(inp->inp_faddr)
-#if INET6
-            )
-#endif
-           )
-               tp->snd_cwnd = mss * ss_fltsz_local;
-       else 
-               tp->snd_cwnd = mss * ss_fltsz;
+       set_tcp_stream_priority(so);
 
        if (rt->rt_rmx.rmx_ssthresh) {
                /*
@@ -3318,7 +4052,23 @@ tcp_mss(tp, offer)
                 */
                tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh);
                tcpstat.tcps_usedssthresh++;
+       } else {
+               tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT;
        }
+
+
+       /*
+        * Set the slow-start flight size depending on whether this
+        * is a local network or not.
+        */
+       if (CC_ALGO(tp)->cwnd_init != NULL)
+               CC_ALGO(tp)->cwnd_init(tp);
+
+       DTRACE_TCP5(cc, void, NULL, struct inpcb *, tp->t_inpcb, struct tcpcb *, tp,
+               struct tcphdr *, NULL, int32_t, TCP_CC_CWND_INIT);
+
+       /* Route locked during lookup above */
+       RT_UNLOCK(rt);
 }
 
 /*
@@ -3329,6 +4079,7 @@ tcp_mssopt(tp)
        struct tcpcb *tp;
 {
        struct rtentry *rt;
+       int mss;
 #if INET6
        int isipv6;
        int min_protoh;
@@ -3341,18 +4092,20 @@ tcp_mssopt(tp)
 #else
 #define min_protoh  (sizeof (struct tcpiphdr))
 #endif
+
 #if INET6
        if (isipv6)
-               rt = tcp_rtlookup6(tp->t_inpcb);
+               rt = tcp_rtlookup6(tp->t_inpcb, IFSCOPE_NONE);
        else
 #endif /* INET6 */
-       rt = tcp_rtlookup(tp->t_inpcb);
-       if (rt == NULL)
-               return
+       rt = tcp_rtlookup(tp->t_inpcb, IFSCOPE_NONE);
+       if (rt == NULL) {
+               return (
 #if INET6
                        isipv6 ? tcp_v6mssdflt :
 #endif /* INET6 */
-                       tcp_mssdflt;
+                       tcp_mssdflt);
+       }
        /*
         * Slower link window correction:
         * If a value is specificied for slowlink_wsize use it for PPP links
@@ -3364,29 +4117,30 @@ tcp_mssopt(tp)
                tp->t_flags |= TF_SLOWLINK;
        }
 
-       return rt->rt_ifp->if_mtu - min_protoh;
+#if INET6
+       mss = (isipv6 ? tcp_maxmtu6(rt) : tcp_maxmtu(rt));
+#else
+       mss = tcp_maxmtu(rt);
+#endif
+       /* Route locked during lookup above */
+       RT_UNLOCK(rt);
+       return (mss - min_protoh);
 }
 
-
 /*
- * Checks for partial ack.  If partial ack arrives, force the retransmission
- * of the next unacknowledged segment, do not clear tp->t_dupacks, and return
- * 1.  By setting snd_nxt to ti_ack, this forces retransmission timer to
- * be started again.  If the ack advances at least to tp->snd_recover, return 0.
+ * On a partial ack arrives, force the retransmission of the
+ * next unacknowledged segment.  Do not clear tp->t_dupacks.
+ * By setting snd_nxt to th_ack, this forces retransmission timer to
+ * be started again.
  */
-static int
-tcp_newreno(tp, th)
+static void
+tcp_newreno_partial_ack(tp, th)
        struct tcpcb *tp;
        struct tcphdr *th;
 {
-       if (SEQ_LT(th->th_ack, tp->snd_recover)) {
                tcp_seq onxt = tp->snd_nxt;
-               u_long  ocwnd = tp->snd_cwnd;
-#ifdef __APPLE__
+               u_int32_t  ocwnd = tp->snd_cwnd;
                tp->t_timer[TCPT_REXMT] = 0;
-#else
-               callout_stop(tp->tt_rexmt);
-#endif
                tp->t_rtttime = 0;
                tp->snd_nxt = th->th_ack;
                /*
@@ -3404,10 +4158,12 @@ tcp_newreno(tp, th)
                 * Partial window deflation.  Relies on fact that tp->snd_una
                 * not updated yet.
                 */
-               tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg);
-               return (1);
-       }
-       return (0);
+               if (tp->snd_cwnd > th->th_ack - tp->snd_una)
+                       tp->snd_cwnd -= th->th_ack - tp->snd_una;
+               else
+                       tp->snd_cwnd = 0;
+               tp->snd_cwnd += tp->t_maxseg;
+
 }
 
 /*
@@ -3420,9 +4176,9 @@ tcp_newreno(tp, th)
  * The listening TCP socket "head" must be locked
  */
 static int
-tcpdropdropablreq(struct socket *head)
+tcp_dropdropablreq(struct socket *head)
 {
-       struct socket *so;
+       struct socket *so, *sonext;
        unsigned int i, j, qlen;
        static int rnd;
        static struct timeval old_runtime;
@@ -3430,7 +4186,14 @@ tcpdropdropablreq(struct socket *head)
        struct timeval tv;
        struct inpcb *inp = NULL;
        struct tcpcb *tp;
-       
+
+       if ((head->so_options & SO_ACCEPTCONN) == 0)
+               return 0;
+
+       so = TAILQ_FIRST(&head->so_incomp);
+       if (!so)
+               return 0;
+
        microtime(&tv);
        if ((i = (tv.tv_sec - old_runtime.tv_sec)) != 0) {
                old_runtime = tv;
@@ -3438,9 +4201,6 @@ tcpdropdropablreq(struct socket *head)
                cur_cnt = 0;
        }
        
-       so = TAILQ_FIRST(&head->so_incomp);
-       if (!so)
-               return 0;
        
        qlen = head->so_incqlen;
        if (++cur_cnt > qlen || old_cnt > qlen) {
@@ -3450,52 +4210,202 @@ tcpdropdropablreq(struct socket *head)
                while (j-- && so)
                        so = TAILQ_NEXT(so, so_list);
        }
-       /* Find a connection that is not already closing */
+       /* Find a connection that is not already closing (or being served) */
        while (so) {
                inp = (struct inpcb *)so->so_pcb;
                
-               if (in_pcb_checkstate(inp, WNT_ACQUIRE, 0) != WNT_STOPUSING)
-                       break;
+               sonext = TAILQ_NEXT(so, so_list);
+
+               if (in_pcb_checkstate(inp, WNT_ACQUIRE, 0) != WNT_STOPUSING) {
+                       /* Avoid the issue of a socket being accepted by one input thread
+                        * and being dropped by another input thread.
+                        * If we can't get a hold on this mutex, then grab the next socket in line.
+                        */
+                       if (lck_mtx_try_lock(&inp->inpcb_mtx)) {
+                               so->so_usecount++;
+                               if ((so->so_usecount == 2) && 
+                                   (so->so_state & SS_INCOMP) != 0 &&
+                                   (so->so_flags & SOF_INCOMP_INPROGRESS) == 0) 
+                                       break;
+                               else {/* don't use if being accepted or used in any other way */
+                                       in_pcb_checkstate(inp, WNT_RELEASE, 1);
+                                       tcp_unlock(so, 1, 0);
+                               }
+                       }
+                       else {
+                               /* do not try to lock the inp in in_pcb_checkstate
+                                * because the lock is already held in some other thread.
+                                * Only drop the inp_wntcnt reference.
+                                */
+                               in_pcb_checkstate(inp, WNT_RELEASE, 1);
+                       }
+               }
+               so = sonext;
                
-               so = TAILQ_NEXT(so, so_list);
        }
        if (!so)
                return 0;
-       
-       head->so_incqlen--;
-       head->so_qlen--;
-       TAILQ_REMOVE(&head->so_incomp, so, so_list);
-       tcp_unlock(head, 0, 0);
 
-       /* Let's remove this connection from the incomplete list */
-       tcp_lock(so, 1, 0);
-       
+       /* Makes sure socket is still in the right state to be discarded */
+
        if (in_pcb_checkstate(inp, WNT_RELEASE, 1) == WNT_STOPUSING) {
                tcp_unlock(so, 1, 0);
                return 0;
        }
-       
-       so->so_head = NULL;
-       so->so_usecount--;      /* No more held by so_head */
 
-       /* 
-        * We do not want to lose track of the PCB right away in case we receive 
-        * more segments from the peer
-        */
+       if (so->so_usecount != 2 || !(so->so_state & SS_INCOMP)) {
+               /* do not discard: that socket is being accepted */
+               tcp_unlock(so, 1, 0);
+               return 0;
+       }
+
+       TAILQ_REMOVE(&head->so_incomp, so, so_list);
+       tcp_unlock(head, 0, 0);
+
+       lck_mtx_assert(&inp->inpcb_mtx, LCK_MTX_ASSERT_OWNED);
        tp = sototcpcb(so);
-       tp->t_flags |= TF_LQ_OVERFLOW;
-       tp->t_state = TCPS_CLOSED;
-       (void) tcp_output(tp);
+       so->so_flags |= SOF_OVERFLOW;
+       so->so_head = NULL;
+
+       tcp_close(tp);
+       tp->t_unacksegs = 0;
+
+       if (inp->inp_wantcnt > 0 && inp->inp_wantcnt != WNT_STOPUSING) {
+               /* Some one has a wantcnt on this pcb. Since WNT_ACQUIRE
+                * doesn't require a lock, it could have happened while
+                * we are holding the lock. This pcb will have to
+                * be garbage collected later.
+                * Release the reference held for so_incomp queue
+                */
+               so->so_usecount--;
+
+               tcp_unlock(so, 1, 0);
+       } else {
+               /* Unlock this socket and leave the reference on. We need to
+                * acquire the pcbinfo lock in order to fully dispose it off 
+                */
+               tcp_unlock(so, 0, 0);
+
+               lck_rw_lock_exclusive(tcbinfo.mtx);
+
+               tcp_lock(so, 0, 0);
+
+               /* Release the reference held for so_incomp queue */
+               so->so_usecount--;
+
+               if (so->so_usecount != 1 || 
+                   (inp->inp_wantcnt > 0 && inp->inp_wantcnt != WNT_STOPUSING)) {
+                       /* There is an extra wantcount or usecount that must
+                        * have been added when the socket was unlocked. This
+                        * socket will have to be garbage collected later
+                        */
+                       tcp_unlock(so, 1, 0);
+               } else {
+
+                       /* Drop the reference held for this function */
+                       so->so_usecount--;
+
+                       in_pcbdispose(inp);
+               }
+               lck_rw_done(tcbinfo.mtx);
+       }
        tcpstat.tcps_drops++;
-       soisdisconnected(so);
-       tcp_canceltimers(tp);
-       add_to_time_wait(tp);
-       
-       tcp_unlock(so, 1, 0);
+
        tcp_lock(head, 0, 0);
-       
-       return 1;
-       
+       head->so_incqlen--;
+       head->so_qlen--;
+       return(1);
+}
+
+/* Set background congestion control on a socket */
+void
+tcp_set_background_cc(struct socket *so)
+{
+       tcp_set_new_cc(so, TCP_CC_ALGO_BACKGROUND_INDEX);
+}
+
+/* Set foreground congestion control on a socket */
+void
+tcp_set_foreground_cc(struct socket *so)
+{
+       tcp_set_new_cc(so, TCP_CC_ALGO_NEWRENO_INDEX);
+}
+
+static void
+tcp_set_new_cc(struct socket *so, uint16_t cc_index)
+{
+       struct inpcb *inp = sotoinpcb(so);
+       struct tcpcb *tp = intotcpcb(inp);
+       uint16_t old_cc_index = 0;
+       if (tp->tcp_cc_index != cc_index) {
+
+               old_cc_index = tp->tcp_cc_index;
+
+               if (CC_ALGO(tp)->cleanup != NULL)
+                       CC_ALGO(tp)->cleanup(tp);
+               tp->tcp_cc_index = cc_index;
+
+               /* Decide if the connection is just starting or if
+                * we have sent some packets on it.
+                */
+               if (tp->snd_nxt > tp->iss) {
+                       /* Already sent some packets */
+                       if (CC_ALGO(tp)->switch_to != NULL)
+                               CC_ALGO(tp)->switch_to(tp, old_cc_index);
+               } else {        
+                       if (CC_ALGO(tp)->init != NULL)
+                               CC_ALGO(tp)->init(tp);
+               }
+               DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp,
+                       struct tcpcb *, tp, struct tcphdr *, NULL,
+                       int32_t, TCP_CC_CHANGE_ALGO);
+       }
 }
 
+static int
+tcp_getstat SYSCTL_HANDLER_ARGS
+{
+#pragma unused(oidp, arg1, arg2)
+
+       int error;
+
+       if (req->oldptr == 0) {
+               req->oldlen= (size_t)sizeof(struct tcpstat);
+       }
+
+       error = SYSCTL_OUT(req, &tcpstat, MIN(sizeof (tcpstat), req->oldlen));
+
+        return (error);
+
+}
+
+SYSCTL_PROC(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RD | CTLFLAG_LOCKED, 0, 0,
+    tcp_getstat, "S,tcpstat", "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
+
+static int
+sysctl_rexmtthresh SYSCTL_HANDLER_ARGS
+{
+#pragma unused(arg1, arg2)
+
+       int error, val = tcprexmtthresh;
+
+       error = sysctl_handle_int(oidp, &val, 0, req);
+       if (error || !req->newptr)
+                return (error);
+
+       /*
+        * Constrain the number of duplicate ACKs
+        * to consider for TCP fast retransmit 
+        * to either 2 or 3
+        */
+
+        if (val < 2 || val > 3)
+               return (EINVAL);
+
+        tcprexmtthresh = val;
+
+       return (0);
+}
 
+SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmt_thresh, CTLTYPE_INT|CTLFLAG_RW | CTLFLAG_LOCKED,
+       &tcprexmtthresh, 0, &sysctl_rexmtthresh, "I", "Duplicate ACK Threshold for Fast Retransmit");