xnu-2422.115.4.tar.gz

[apple/xnu.git] / bsd / netinet / tcp_output.c

diff --git a/bsd/netinet/tcp_output.c b/bsd/netinet/tcp_output.c
index c648029c645b6c1f936d7070faabb8a69f114ec3..fa6e5348c0337aeb7847d37e17a534a230bba4c5 100644 (file)
--- a/bsd/netinet/tcp_output.c
+++ b/bsd/netinet/tcp_output.c
@@ -1,23 +1,29 @@
 /*
 /*

- * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
+ * Copyright (c) 2000-2014 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,
  * 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, 1995
  */
 /*
  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995


@@ -52,17 +58,22 @@
  * SUCH DAMAGE.
  *
  *     @(#)tcp_output.c        8.4 (Berkeley) 5/24/95
  * SUCH DAMAGE.
  *
  *     @(#)tcp_output.c        8.4 (Berkeley) 5/24/95

+ * $FreeBSD: src/sys/netinet/tcp_output.c,v 1.39.2.10 2001/07/07 04:30:38 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.

  */
 
  */
 

-#if ISFB31
-#include "opt_tcpdebug.h"
-#endif

 #define        _IP_VHL
 
 #define        _IP_VHL
 

-#include <stddef.h>

 
 #include <sys/param.h>
 #include <sys/systm.h>
 
 #include <sys/param.h>
 #include <sys/systm.h>

+#include <sys/kernel.h>
+#include <sys/sysctl.h>

 #include <sys/mbuf.h>
 #include <sys/domain.h>
 #include <sys/protosw.h>
 #include <sys/mbuf.h>
 #include <sys/domain.h>
 #include <sys/protosw.h>


@@ -70,17 +81,24 @@
 #include <sys/socketvar.h>
 
 #include <net/route.h>
 #include <sys/socketvar.h>
 
 #include <net/route.h>

+#include <net/ntstat.h>
+#include <net/if_var.h>
+#include <net/if.h>
+#include <net/if_types.h>
+#include <net/dlil.h>

 
 #include <netinet/in.h>
 #include <netinet/in_systm.h>
 
 #include <netinet/in.h>
 #include <netinet/in_systm.h>

+#include <netinet/in_var.h>

 #include <netinet/ip.h>
 #include <netinet/ip.h>

+#include <netinet/in_pcb.h>

 #include <netinet/ip_var.h>
 #include <netinet/ip_var.h>

+#include <mach/sdt.h>

 #if INET6
 #if INET6

+#include <netinet6/in6_pcb.h>

 #include <netinet/ip6.h>
 #include <netinet/ip6.h>

-#include <netinet/ip_var.h>

 #include <netinet6/ip6_var.h>
 #endif
 #include <netinet6/ip6_var.h>
 #endif

-#include <netinet/in_pcb.h>

 #include <netinet/tcp.h>
 #define        TCPOUTFLAGS
 #include <netinet/tcp_fsm.h>
 #include <netinet/tcp.h>
 #define        TCPOUTFLAGS
 #include <netinet/tcp_fsm.h>


@@ -88,53 +106,207 @@
 #include <netinet/tcp_timer.h>
 #include <netinet/tcp_var.h>
 #include <netinet/tcpip.h>
 #include <netinet/tcp_timer.h>
 #include <netinet/tcp_var.h>
 #include <netinet/tcpip.h>

+#include <netinet/tcp_cc.h>

 #if TCPDEBUG
 #include <netinet/tcp_debug.h>
 #endif
 #include <sys/kdebug.h>
 #if TCPDEBUG
 #include <netinet/tcp_debug.h>
 #endif
 #include <sys/kdebug.h>

+#include <mach/sdt.h>
+
+#if IPSEC
+#include <netinet6/ipsec.h>
+#endif /*IPSEC*/
+
+#if CONFIG_MACF_NET
+#include <security/mac_framework.h>
+#endif /* MAC_SOCKET */
+
+#include <netinet/lro_ext.h>
+#if MPTCP
+#include <netinet/mptcp_var.h>
+#include <netinet/mptcp.h>
+#include <netinet/mptcp_opt.h>
+#endif

 
 #define DBG_LAYER_BEG          NETDBG_CODE(DBG_NETTCP, 1)
 #define DBG_LAYER_END          NETDBG_CODE(DBG_NETTCP, 3)
 #define DBG_FNC_TCP_OUTPUT     NETDBG_CODE(DBG_NETTCP, (4 << 8) | 1)
 
 
 #define DBG_LAYER_BEG          NETDBG_CODE(DBG_NETTCP, 1)
 #define DBG_LAYER_END          NETDBG_CODE(DBG_NETTCP, 3)
 #define DBG_FNC_TCP_OUTPUT     NETDBG_CODE(DBG_NETTCP, (4 << 8) | 1)
 

+int path_mtu_discovery = 1;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW | CTLFLAG_LOCKED,
+       &path_mtu_discovery, 1, "Enable Path MTU Discovery");
+
+int ss_fltsz = 1;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW | CTLFLAG_LOCKED,
+       &ss_fltsz, 1, "Slow start flight size");
+
+int ss_fltsz_local = 8; /* starts with eight segments max */
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW | CTLFLAG_LOCKED,
+       &ss_fltsz_local, 1, "Slow start flight size for local networks");
+
+int    tcp_do_tso = 1;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW | CTLFLAG_LOCKED,
+       &tcp_do_tso, 0, "Enable TCP Segmentation Offload");
+
+
+int     tcp_ecn_outbound = 0;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, ecn_initiate_out, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_ecn_outbound,
+        0, "Initiate ECN for outbound connections");
+
+int     tcp_ecn_inbound = 0;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, ecn_negotiate_in, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_ecn_inbound,
+        0, "Allow ECN negotiation for inbound connections");
+
+int    tcp_packet_chaining = 50;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, packetchain, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_packet_chaining,
+        0, "Enable TCP output packet chaining");
+
+int    tcp_output_unlocked = 1;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, socket_unlocked_on_output, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_output_unlocked,
+        0, "Unlock TCP when sending packets down to IP");
+
+int tcp_do_rfc3390 = 1;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW | CTLFLAG_LOCKED,
+       &tcp_do_rfc3390, 1, "Calculate intial slowstart cwnd depending on MSS");
+
+int tcp_min_iaj_win = MIN_IAJ_WIN;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, min_iaj_win, CTLFLAG_RW | CTLFLAG_LOCKED,
+       &tcp_min_iaj_win, 1, "Minimum recv win based on inter-packet arrival jitter");
+
+int tcp_acc_iaj_react_limit = ACC_IAJ_REACT_LIMIT;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, acc_iaj_react_limit, CTLFLAG_RW | CTLFLAG_LOCKED,
+        &tcp_acc_iaj_react_limit, 1, "Accumulated IAJ when receiver starts to react");
+
+uint32_t tcp_do_autosendbuf = 1;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, doautosndbuf, CTLFLAG_RW | CTLFLAG_LOCKED,
+        &tcp_do_autosendbuf, 1, "Enable send socket buffer auto-tuning");
+
+uint32_t tcp_autosndbuf_inc = 8 * 1024;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, autosndbufinc, CTLFLAG_RW | CTLFLAG_LOCKED,
+        &tcp_autosndbuf_inc, 1, "Increment in send socket bufffer size");
+
+uint32_t tcp_autosndbuf_max = 512 * 1024;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, autosndbufmax, CTLFLAG_RW | CTLFLAG_LOCKED,
+        &tcp_autosndbuf_max, 1, "Maximum send socket buffer size");
+
+uint32_t tcp_prioritize_acks = 1;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, ack_prioritize, CTLFLAG_RW | CTLFLAG_LOCKED,
+        &tcp_prioritize_acks, 1, "Prioritize pure acks");
+
+uint32_t tcp_use_rtt_recvbg = 1;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, rtt_recvbg, 
+       CTLFLAG_RW | CTLFLAG_LOCKED,
+        &tcp_use_rtt_recvbg, 1, "Use RTT for bg recv algorithm");
+
+uint32_t tcp_recv_throttle_minwin = 16 * 1024;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, recv_throttle_minwin, 
+       CTLFLAG_RW | CTLFLAG_LOCKED,
+        &tcp_recv_throttle_minwin, 1, "Minimum recv win for throttling");
+
+
+static int32_t packchain_newlist = 0;
+static int32_t packchain_looped = 0;
+static int32_t packchain_sent = 0;

 
 

-#ifdef notyet
-extern struct mbuf *m_copypack();
+/* temporary: for testing */
+#if IPSEC
+extern int ipsec_bypass;

 #endif
 
 #endif
 

+extern int slowlink_wsize;     /* window correction for slow links */
+#if IPFIREWALL
+extern int fw_enable;          /* firewall check for packet chaining */
+extern int fw_bypass;          /* firewall check: disable packet chaining if there is rules */
+#endif /* IPFIREWALL */
+
+extern u_int32_t dlil_filter_disable_tso_count;
+extern u_int32_t kipf_count;
+extern int tcp_recv_bg;
+extern int maxseg_unacked;
+
+static int tcp_ip_output(struct socket *, struct tcpcb *, struct mbuf *, int,
+    struct mbuf *, int, int, int32_t, boolean_t);
+
+extern uint32_t get_base_rtt(struct tcpcb *tp);
+static struct mbuf* tcp_send_lroacks(struct tcpcb *tp, struct mbuf *m, struct tcphdr *th);
+static int tcp_recv_throttle(struct tcpcb *tp);

 
 /*
  * Tcp output routine: figure out what should be sent and send it.
 
 /*
  * Tcp output routine: figure out what should be sent and send it.

+ *
+ * Returns:    0                       Success
+ *             EADDRNOTAVAIL
+ *             ENOBUFS
+ *             EMSGSIZE
+ *             EHOSTUNREACH
+ *             ENETDOWN
+ *     ip_output_list:ENOMEM
+ *     ip_output_list:EADDRNOTAVAIL
+ *     ip_output_list:ENETUNREACH
+ *     ip_output_list:EHOSTUNREACH
+ *     ip_output_list:EACCES
+ *     ip_output_list:EMSGSIZE
+ *     ip_output_list:ENOBUFS
+ *     ip_output_list:???              [ignorable: mostly IPSEC/firewall/DLIL]
+ *     ip6_output_list:EINVAL
+ *     ip6_output_list:EOPNOTSUPP
+ *     ip6_output_list:EHOSTUNREACH
+ *     ip6_output_list:EADDRNOTAVAIL
+ *     ip6_output_list:ENETUNREACH
+ *     ip6_output_list:EMSGSIZE
+ *     ip6_output_list:ENOBUFS
+ *     ip6_output_list:???             [ignorable: mostly IPSEC/firewall/DLIL]

  */
 int
  */
 int

-tcp_output(tp)
-       register struct tcpcb *tp;
+tcp_output(struct tcpcb *tp)

 {
 {

-       register struct socket *so = tp->t_inpcb->inp_socket;
-       register long len, win;
-       int off, flags, error;
+       struct inpcb *inp = tp->t_inpcb;
+       struct socket *so = inp->inp_socket;
+       int32_t len, recwin, sendwin, off;
+       int flags, error;

        register struct mbuf *m;
        struct ip *ip = NULL;
        register struct mbuf *m;
        struct ip *ip = NULL;

-       struct ipovly *ipov = NULL;
+       register struct ipovly *ipov = NULL;

 #if INET6
        struct ip6_hdr *ip6 = NULL;
 #endif /* INET6 */
 #if INET6
        struct ip6_hdr *ip6 = NULL;
 #endif /* INET6 */

-       struct tcphdr *th;
+       register struct tcphdr *th;

        u_char opt[TCP_MAXOLEN];
        unsigned ipoptlen, optlen, hdrlen;
        u_char opt[TCP_MAXOLEN];
        unsigned ipoptlen, optlen, hdrlen;

-       int idle, sendalot;
-       struct rmxp_tao *taop;
-       struct rmxp_tao tao_noncached;
+       int idle, sendalot, lost = 0;
+       int i, sack_rxmit;
+       int tso = 0;
+       int sack_bytes_rxmt;
+       struct sackhole *p;
+#if IPSEC
+       unsigned ipsec_optlen = 0;
+#endif /* IPSEC */
+       int    last_off = 0;
+       int    m_off = 0;
+       int    idle_time = 0;
+       struct mbuf *m_lastm = NULL;
+       struct mbuf *m_head = NULL;
+       struct mbuf *packetlist = NULL;
+       struct mbuf *tp_inp_options = inp->inp_depend4.inp4_options;

 #if INET6
 #if INET6

-       int isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV4) == 0;
+       int isipv6 = inp->inp_vflag & INP_IPV6 ;

 #endif
 #endif

-
-       KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_START, 0,0,0,0,0);
-       KERNEL_DEBUG(DBG_LAYER_BEG,
-                    ((tp->t_template->tt_dport << 16) | tp->t_template->tt_sport),
-                    (((tp->t_template->tt_src.s_addr & 0xffff) << 16) |
-                     (tp->t_template->tt_dst.s_addr & 0xffff)),
-                    0,0,0);
+       short packchain_listadd = 0;
+       int so_options = so->so_options;
+       struct rtentry *rt;
+       u_int32_t basertt, svc_flags = 0, allocated_len;
+       u_int32_t lro_ackmore = (tp->t_lropktlen != 0) ? 1 : 0;
+       struct mbuf *mnext = NULL;
+       int sackoptlen = 0;
+#if MPTCP
+       unsigned int *dlenp = NULL;
+       u_int8_t *finp = NULL;
+       u_int32_t *sseqp = NULL;
+       u_int64_t dss_val = 0;
+       int mptcp_acknow = 0;
+#endif /* MPTCP */
+       boolean_t cell = FALSE;
+       boolean_t wifi = FALSE;

 
        /*
         * Determine length of data that should be transmitted,
 
        /*
         * Determine length of data that should be transmitted,


@@ -142,24 +314,245 @@ tcp_output(tp)
         * If there is some data or critical controls (SYN, RST)
         * to send, then transmit; otherwise, investigate further.
         */
         * If there is some data or critical controls (SYN, RST)
         * to send, then transmit; otherwise, investigate further.
         */

-       idle = (tp->snd_max == tp->snd_una);
-       if (idle && tp->t_idle >= tp->t_rxtcur)
-               /*
-                * We have been idle for "a while" and no acks are
-                * expected to clock out any data we send --
-                * slow start to get ack "clock" running again.
+       idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
+
+       /* Since idle_time is signed integer, the following integer subtraction
+        * will take care of wrap around of tcp_now
+        */
+       idle_time = tcp_now - tp->t_rcvtime;
+       if (idle && idle_time >= TCP_IDLETIMEOUT(tp)) {
+               if (CC_ALGO(tp)->after_idle != NULL) 
+                       CC_ALGO(tp)->after_idle(tp);
+               DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp,
+                       struct tcpcb *, tp, struct tcphdr *, NULL,
+                       int32_t, TCP_CC_IDLE_TIMEOUT);
+       }
+       tp->t_flags &= ~TF_LASTIDLE;
+       if (idle) {
+               if (tp->t_flags & TF_MORETOCOME) {
+                       tp->t_flags |= TF_LASTIDLE;
+                       idle = 0;
+               }
+       }
+#if MPTCP 
+       if (tp->t_mpflags & TMPF_RESET) {
+               tcp_check_timer_state(tp);
+               /* 
+                * Once a RST has been sent for an MPTCP subflow, 
+                * the subflow socket stays around until deleted.
+                * No packets such as FINs must be sent after RST.

                 */
                 */

-               tp->snd_cwnd = tp->t_maxseg;
-    
-    /* Never send data that's already been acked */
-    if (SEQ_GT(tp->snd_una, tp->snd_nxt))
-        tp->snd_nxt = tp->snd_una;
+               return (0);
+       }
+#endif /* MPTCP */
+

 again:
 again:

+       KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_START, 0,0,0,0,0);
+
+#if INET6
+       if (isipv6) {
+               KERNEL_DEBUG(DBG_LAYER_BEG,
+                    ((inp->inp_fport << 16) | inp->inp_lport),
+                    (((inp->in6p_laddr.s6_addr16[0] & 0xffff) << 16) |
+                     (inp->in6p_faddr.s6_addr16[0] & 0xffff)),
+                    sendalot,0,0);
+       } else
+#endif
+
+       {
+               KERNEL_DEBUG(DBG_LAYER_BEG,
+                    ((inp->inp_fport << 16) | inp->inp_lport),
+                    (((inp->inp_laddr.s_addr & 0xffff) << 16) |
+                     (inp->inp_faddr.s_addr & 0xffff)),
+                    sendalot,0,0);
+       }
+       /*
+        * If the route generation id changed, we need to check that our
+        * local (source) IP address is still valid. If it isn't either
+        * return error or silently do nothing (assuming the address will
+        * come back before the TCP connection times out).
+        */
+       rt = inp->inp_route.ro_rt;
+       if (rt != NULL && ROUTE_UNUSABLE(&tp->t_inpcb->inp_route)) {
+               struct ifnet *ifp;
+               struct in_ifaddr *ia = NULL;
+               struct in6_ifaddr *ia6 = NULL;
+               int found_srcaddr = 0;
+
+               /* disable multipages at the socket */
+               somultipages(so, FALSE);
+
+               /* Disable TSO for the socket until we know more */
+               tp->t_flags &= ~TF_TSO;
+
+               if (isipv6) {
+                       ia6 = ifa_foraddr6(&inp->in6p_laddr);
+                       if (ia6 != NULL)
+                               found_srcaddr = 1;
+               } else {
+                       ia = ifa_foraddr(inp->inp_laddr.s_addr);
+                       if (ia != NULL)
+                               found_srcaddr = 1;
+               }
+
+               /* check that the source address is still valid */
+               if (found_srcaddr == 0) {
+                       soevent(so,
+                           (SO_FILT_HINT_LOCKED | SO_FILT_HINT_NOSRCADDR));
+
+                       if (tp->t_state >= TCPS_CLOSE_WAIT) {
+                               tcp_drop(tp, EADDRNOTAVAIL);
+                               return(EADDRNOTAVAIL);
+                       }
+
+                       /* set Retransmit  timer if it wasn't set
+                        * reset Persist timer and shift register as the
+                        * advertised peer window may not be valid anymore
+                        */
+
+                       if (!tp->t_timer[TCPT_REXMT]) {
+                               tp->t_timer[TCPT_REXMT] = OFFSET_FROM_START(tp, tp->t_rxtcur);
+                               if (tp->t_timer[TCPT_PERSIST]) {
+                                       tp->t_timer[TCPT_PERSIST] = 0;
+                                       tp->t_rxtshift = 0;
+                                       tp->t_persist_stop = 0;
+                                       tp->t_rxtstart = 0;
+                               }
+                       }
+
+                       if (tp->t_pktlist_head != NULL)
+                               m_freem_list(tp->t_pktlist_head);
+                       TCP_PKTLIST_CLEAR(tp);
+
+                       /* drop connection if source address isn't available */
+                       if (so->so_flags & SOF_NOADDRAVAIL) { 
+                               tcp_drop(tp, EADDRNOTAVAIL);
+                               return(EADDRNOTAVAIL);
+                       }
+                       else {
+                               tcp_check_timer_state(tp);
+                               return(0); /* silently ignore, keep data in socket: address may be back */
+                       }
+               }
+               if (ia != NULL)
+                       IFA_REMREF(&ia->ia_ifa);
+
+               if (ia6 != NULL)
+                       IFA_REMREF(&ia6->ia_ifa);
+
+               /*
+                * Address is still valid; check for multipages capability
+                * again in case the outgoing interface has changed.
+                */
+               RT_LOCK(rt);
+               if ((ifp = rt->rt_ifp) != NULL) {
+                       somultipages(so, (ifp->if_hwassist & IFNET_MULTIPAGES));
+                       tcp_set_tso(tp, ifp);
+               }
+               if (rt->rt_flags & RTF_UP)
+                       RT_GENID_SYNC(rt);
+               /*
+                * See if we should do MTU discovery. Don't do it if:
+                *      1) it is disabled via the sysctl
+                *      2) the route isn't up
+                *      3) the MTU is locked (if it is, then discovery has been
+                *         disabled)
+                */
+
+               if (!path_mtu_discovery || ((rt != NULL) && 
+                   (!(rt->rt_flags & RTF_UP) || (rt->rt_rmx.rmx_locks & RTV_MTU)))) 
+                       tp->t_flags &= ~TF_PMTUD;
+               else
+                       tp->t_flags |= TF_PMTUD;
+
+               RT_UNLOCK(rt);
+       }
+
+       if (rt != NULL) {
+               cell = IFNET_IS_CELLULAR(rt->rt_ifp);
+               wifi = (!cell && IFNET_IS_WIFI(rt->rt_ifp));
+       }
+
+       /*
+        * If we've recently taken a timeout, snd_max will be greater than
+        * snd_nxt.  There may be SACK information that allows us to avoid
+        * resending already delivered data.  Adjust snd_nxt accordingly.
+        */
+       if (SACK_ENABLED(tp) && SEQ_LT(tp->snd_nxt, tp->snd_max))
+               tcp_sack_adjust(tp);

        sendalot = 0;
        off = tp->snd_nxt - tp->snd_una;
        sendalot = 0;
        off = tp->snd_nxt - tp->snd_una;

-       win = min(tp->snd_wnd, tp->snd_cwnd);
+       sendwin = min(tp->snd_wnd, tp->snd_cwnd);
+
+       if (tp->t_flags & TF_SLOWLINK && slowlink_wsize > 0)
+               sendwin = min(sendwin, slowlink_wsize);

 
        flags = tcp_outflags[tp->t_state];
 
        flags = tcp_outflags[tp->t_state];

+       /*
+        * Send any SACK-generated retransmissions.  If we're explicitly trying
+        * to send out new data (when sendalot is 1), bypass this function.
+        * If we retransmit in fast recovery mode, decrement snd_cwnd, since
+        * we're replacing a (future) new transmission with a retransmission
+        * now, and we previously incremented snd_cwnd in tcp_input().
+        */
+       /*
+        * Still in sack recovery , reset rxmit flag to zero.
+        */
+       sack_rxmit = 0;
+       sack_bytes_rxmt = 0;
+       len = 0;
+       p = NULL;
+       if (SACK_ENABLED(tp) && IN_FASTRECOVERY(tp) &&
+           (p = tcp_sack_output(tp, &sack_bytes_rxmt))) {
+               int32_t cwin;
+               
+               cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt;
+               if (cwin < 0)
+                       cwin = 0;
+               /* Do not retransmit SACK segments beyond snd_recover */
+               if (SEQ_GT(p->end, tp->snd_recover)) {
+                       /*
+                        * (At least) part of sack hole extends beyond
+                        * snd_recover. Check to see if we can rexmit data
+                        * for this hole.
+                        */
+                       if (SEQ_GEQ(p->rxmit, tp->snd_recover)) {
+                               /*
+                                * Can't rexmit any more data for this hole.
+                                * That data will be rexmitted in the next
+                                * sack recovery episode, when snd_recover
+                                * moves past p->rxmit.
+                                */
+                               p = NULL;
+                               goto after_sack_rexmit;
+                       } else
+                               /* Can rexmit part of the current hole */
+                               len = ((int32_t)min(cwin,
+                                                  tp->snd_recover - p->rxmit));
+               } else {
+                       len = ((int32_t)min(cwin, p->end - p->rxmit));
+               }
+               if (len > 0) {
+                       off = p->rxmit - tp->snd_una; /* update off only if we really transmit SACK data */
+                       sack_rxmit = 1;
+                       sendalot = 1;
+                       tcpstat.tcps_sack_rexmits++;
+                       tcpstat.tcps_sack_rexmit_bytes +=
+                           min(len, tp->t_maxseg);
+                       if (nstat_collect) {
+                               nstat_route_tx(inp->inp_route.ro_rt, 1,
+                                       min(len, tp->t_maxseg),
+                                       NSTAT_TX_FLAG_RETRANSMIT);
+                               INP_ADD_STAT(inp, cell, wifi, txpackets, 1);
+                               INP_ADD_STAT(inp, cell, wifi, txbytes,
+                                   min(len, tp->t_maxseg));
+                               tp->t_stat.txretransmitbytes += min(len, tp->t_maxseg);
+                       }
+               } else {
+                       len = 0;
+               }
+       }
+after_sack_rexmit:

        /*
         * Get standard flags, and add SYN or FIN if requested by 'hidden'
         * state flags.
        /*
         * Get standard flags, and add SYN or FIN if requested by 'hidden'
         * state flags.


@@ -176,7 +569,7 @@ again:
         * and go to transmit state.
         */
        if (tp->t_force) {
         * and go to transmit state.
         */
        if (tp->t_force) {

-               if (win == 0) {
+               if (sendwin == 0) {

                        /*
                         * If we still have some data to send, then
                         * clear the FIN bit.  Usually this would
                        /*
                         * If we still have some data to send, then
                         * clear the FIN bit.  Usually this would


@@ -195,18 +588,62 @@ again:
                         */
                        if (off < so->so_snd.sb_cc)
                                flags &= ~TH_FIN;
                         */
                        if (off < so->so_snd.sb_cc)
                                flags &= ~TH_FIN;

-                       win = 1;
+                       sendwin = 1;

                } else {
                        tp->t_timer[TCPT_PERSIST] = 0;
                        tp->t_rxtshift = 0;
                } else {
                        tp->t_timer[TCPT_PERSIST] = 0;
                        tp->t_rxtshift = 0;

+                       tp->t_rxtstart = 0;
+                       tp->t_persist_stop = 0;

                }
        }
 
                }
        }
 

-       len = (long)ulmin(so->so_snd.sb_cc, win) - off;
+       /*
+        * If snd_nxt == snd_max and we have transmitted a FIN, the
+        * offset will be > 0 even if so_snd.sb_cc is 0, resulting in
+        * a negative length.  This can also occur when TCP opens up
+        * its congestion window while receiving additional duplicate
+        * acks after fast-retransmit because TCP will reset snd_nxt
+        * to snd_max after the fast-retransmit.
+        *
+        * In the normal retransmit-FIN-only case, however, snd_nxt will
+        * be set to snd_una, the offset will be 0, and the length may
+        * wind up 0.
+        *
+        * If sack_rxmit is true we are retransmitting from the scoreboard
+        * in which case len is already set.
+        */
+       if (sack_rxmit == 0) {
+               if (sack_bytes_rxmt == 0)
+                       len = min(so->so_snd.sb_cc, sendwin) - off;
+               else {
+                       int32_t cwin;

 
 

-       if ((taop = tcp_gettaocache(tp->t_inpcb)) == NULL) {
-               taop = &tao_noncached;
-               bzero(taop, sizeof(*taop));
+                        /*
+                        * We are inside of a SACK recovery episode and are
+                        * sending new data, having retransmitted all the
+                        * data possible in the scoreboard.
+                        */
+                       len = min(so->so_snd.sb_cc, tp->snd_wnd) 
+                              - off;
+                       /*
+                        * Don't remove this (len > 0) check !
+                        * We explicitly check for len > 0 here (although it 
+                        * isn't really necessary), to work around a gcc 
+                        * optimization issue - to force gcc to compute
+                        * len above. Without this check, the computation
+                        * of len is bungled by the optimizer.
+                        */
+                       if (len > 0) {
+                               cwin = tp->snd_cwnd - 
+                                       (tp->snd_nxt - tp->sack_newdata) -
+                                       sack_bytes_rxmt;
+                               if (cwin < 0)
+                                       cwin = 0;
+                               len = imin(len, cwin);
+                       }
+                       else 
+                               len = 0;
+               }

        }
 
        /*
        }
 
        /*


@@ -215,33 +652,66 @@ again:
         * know that foreign host supports TAO, suppress sending segment.
         */
        if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
         * know that foreign host supports TAO, suppress sending segment.
         */
        if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {

-               flags &= ~TH_SYN;
+               if (tp->t_state != TCPS_SYN_RECEIVED)
+                       flags &= ~TH_SYN;

                off--, len++;
                off--, len++;

-               if (len > 0 && tp->t_state == TCPS_SYN_SENT &&
-                   taop->tao_ccsent == 0) {
-                 KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END, 0,0,0,0,0);
-                 return 0;
+               if (len > 0 && tp->t_state == TCPS_SYN_SENT) {
+                       while (inp->inp_sndinprog_cnt == 0 &&
+                               tp->t_pktlist_head != NULL) {
+                               packetlist = tp->t_pktlist_head;
+                               packchain_listadd = tp->t_lastchain;
+                               packchain_sent++;
+                               TCP_PKTLIST_CLEAR(tp);
+
+                               error = tcp_ip_output(so, tp, packetlist,
+                                   packchain_listadd, tp_inp_options,
+                                   (so_options & SO_DONTROUTE),
+                                   (sack_rxmit | (sack_bytes_rxmt != 0)), 0,
+#if INET6
+                                   isipv6);
+#else /* INET6 */
+                                   0);
+#endif /* !INET6 */
+
+
+                       }
+                       /*
+                        * tcp was closed while we were in ip,
+                        * resume close 
+                        */
+                       if (inp->inp_sndinprog_cnt == 0 &&
+                               (tp->t_flags & TF_CLOSING)) {
+                               tp->t_flags &= ~TF_CLOSING;
+                               (void) tcp_close(tp);
+                       } else {
+                               tcp_check_timer_state(tp);
+                       }
+                       KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END,
+                           0,0,0,0,0);
+                       return(0);

                }
        }
 
        /*
                }
        }
 
        /*

-        * Be careful not to send data and/or FIN on SYN segments
-        * in cases when no CC option will be sent.
+        * Be careful not to send data and/or FIN on SYN segments.

         * This measure is needed to prevent interoperability problems
         * with not fully conformant TCP implementations.
         */
         * This measure is needed to prevent interoperability problems
         * with not fully conformant TCP implementations.
         */

-       if ((flags & TH_SYN) &&
-           ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) ||
-            ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) {
+       if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) {

                len = 0;
                flags &= ~TH_FIN;
        }
 
                len = 0;
                flags &= ~TH_FIN;
        }
 

-       if (len < 0) {
+       /* The check here used to be (len < 0). Some times len is zero when
+        * the congestion window is closed and we need to check if persist timer
+        * has to be set in that case. But don't set persist until connection 
+        * is established.
+        */  
+       if (len <= 0 && !(flags & TH_SYN)) {

                /*
                 * If FIN has been sent but not acked,
                 * but we haven't been called to retransmit,
                /*
                 * If FIN has been sent but not acked,
                 * but we haven't been called to retransmit,

-                * len will be -1.  Otherwise, window shrank
+                * len will be < 0.  Otherwise, window shrank

                 * after we sent into it.  If window shrank to 0,
                 * cancel pending retransmit, pull snd_nxt back
                 * to (closed) window, and set the persist timer
                 * after we sent into it.  If window shrank to 0,
                 * cancel pending retransmit, pull snd_nxt back
                 * to (closed) window, and set the persist timer


@@ -249,73 +719,264 @@ again:
                 * close completely, just wait for an ACK.
                 */
                len = 0;
                 * close completely, just wait for an ACK.
                 */
                len = 0;

-               if (win == 0) {
+               if (sendwin == 0) {

                        tp->t_timer[TCPT_REXMT] = 0;
                        tp->t_rxtshift = 0;
                        tp->t_timer[TCPT_REXMT] = 0;
                        tp->t_rxtshift = 0;

+                       tp->t_rxtstart = 0;

                        tp->snd_nxt = tp->snd_una;
                        if (tp->t_timer[TCPT_PERSIST] == 0)
                                tcp_setpersist(tp);
                }
        }
                        tp->snd_nxt = tp->snd_una;
                        if (tp->t_timer[TCPT_PERSIST] == 0)
                                tcp_setpersist(tp);
                }
        }

+
+       /* Automatic sizing of send socket buffer. Increase the send socket buffer
+        * size if all of the following criteria are met
+        *      1. the receiver has enough buffer space for this data
+        *      2. send buffer is filled to 7/8th with data (so we actually
+        *         have data to make use of it);
+        *      3. our send window (slow start and congestion controlled) is
+        *         larger than sent but unacknowledged data in send buffer.
+        */
+       basertt = get_base_rtt(tp);
+       if (tcp_do_autosendbuf == 1 &&
+           !INP_WAIT_FOR_IF_FEEDBACK(inp) && !IN_FASTRECOVERY(tp) &&
+           (so->so_snd.sb_flags & (SB_AUTOSIZE | SB_TRIM)) == SB_AUTOSIZE &&
+           tcp_cansbgrow(&so->so_snd)) {
+               if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat &&
+                       so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) &&
+                       sendwin >= (so->so_snd.sb_cc - 
+                               (tp->snd_nxt - tp->snd_una))) {
+                       /* Also increase the send buffer only if the 
+                        * round-trip time is not increasing because we do
+                        * not want to contribute to latency by filling buffers.
+                        * We also do not want to hold onto application's
+                        * old data for too long. Interactive applications would
+                        * rather discard old data.
+                        */
+                       if (tp->t_rttcur <= 
+                               (basertt + 25)) {
+                               if (sbreserve(&so->so_snd, 
+                                       min(so->so_snd.sb_hiwat + tcp_autosndbuf_inc,
+                                       tcp_autosndbuf_max)) == 1) {
+                                       so->so_snd.sb_idealsize = so->so_snd.sb_hiwat;
+                               }
+                       } else {
+                               so->so_snd.sb_idealsize = 
+                                   max(tcp_sendspace, so->so_snd.sb_hiwat -
+                                       (2 * tcp_autosndbuf_inc));
+                               so->so_snd.sb_flags |= SB_TRIM;
+                       }
+               }
+       }
+
+       /*
+        * Truncate to the maximum segment length or enable TCP Segmentation
+        * Offloading (if supported by hardware) and ensure that FIN is removed
+        * if the length no longer contains the last data byte.
+        *
+        * TSO may only be used if we are in a pure bulk sending state.
+        * The presence of TCP-MD5, SACK retransmits, SACK advertizements,
+        * ipfw rules and IP options, as well as disabling hardware checksum
+        * offload prevent using TSO.  With TSO the TCP header is the same
+        * (except for the sequence number) for all generated packets.  This
+        * makes it impossible to transmit any options which vary per generated
+        * segment or packet.
+        *
+        * The length of TSO bursts is limited to TCP_MAXWIN.  That limit and
+        * removal of FIN (if not already catched here) are handled later after
+        * the exact length of the TCP options are known.
+        */
+#if IPSEC
+       /*
+        * Pre-calculate here as we save another lookup into the darknesses
+        * of IPsec that way and can actually decide if TSO is ok.
+        */
+       if (ipsec_bypass == 0)
+               ipsec_optlen = ipsec_hdrsiz_tcp(tp);
+#endif
+

        if (len > tp->t_maxseg) {
        if (len > tp->t_maxseg) {

-               len = tp->t_maxseg;
-               sendalot = 1;
+               if ((tp->t_flags & TF_TSO) && tcp_do_tso && hwcksum_tx &&
+                   ip_use_randomid && kipf_count == 0 && dlil_filter_disable_tso_count == 0 &&
+                   tp->rcv_numsacks == 0 && sack_rxmit == 0  && sack_bytes_rxmt == 0 &&
+                   inp->inp_options == NULL &&
+                   inp->in6p_options == NULL
+#if IPSEC
+                   && ipsec_optlen == 0
+#endif
+#if IPFIREWALL
+                   && (fw_enable == 0 || fw_bypass)
+#endif
+                   ) {
+                       tso = 1;
+                       sendalot = 0;
+               } else {
+                       len = tp->t_maxseg;
+                       sendalot = 1;
+                       tso = 0;
+               }

        }
        }

-       if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc))
-               flags &= ~TH_FIN;
+#if MPTCP
+       if (so->so_flags & SOF_MP_SUBFLOW) {
+               int newlen = len;
+               if ((tp->t_mpflags & TMPF_SND_MPPRIO) ||
+                   (tp->t_mpflags & TMPF_SND_REM_ADDR) ||
+                   (tp->t_mpflags & TMPF_SND_MPFAIL)) {
+                       if (len > 0) {
+                               len = 0;
+                       }
+                       sendalot = 1;
+                       mptcp_acknow = 1;
+               } else {
+                       mptcp_acknow = 0;
+               }
+               /*
+                * The contiguous bytes in the subflow socket buffer can be
+                * discontiguous at the MPTCP level. Since only one DSS 
+                * option can be sent in one packet, reduce length to match
+                * the contiguous MPTCP level. Set sendalot to send remainder.
+                */
+               if (len > 0)
+                       newlen = mptcp_adj_sendlen(so, off, len);
+               if (newlen < len) {
+                       len = newlen;
+                       sendalot = 1;
+               }
+       }
+#endif /* MPTCP */
+       if (sack_rxmit) {
+               if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc))
+                       flags &= ~TH_FIN;
+       } else {
+               if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc))
+                       flags &= ~TH_FIN;
+       }
+
+       recwin = tcp_sbspace(tp);
+
+
+       /*
+        * If the socket is capable of doing unordered send,
+        * pull the amount of data that can be sent from the
+        * unordered priority queues to the serial queue in
+        * the socket buffer. If bytes are not yet available
+        * in the highest priority message, we may not be able 
+        * to send any new data. 
+        */
+       if (so->so_flags & SOF_ENABLE_MSGS) {
+               if ((off + len) >
+                   so->so_msg_state->msg_serial_bytes) {
+                       sbpull_unordered_data(so, off, len);

 
 

-       win = sbspace(&so->so_rcv);
+                       /* check if len needs to be modified */
+                       if ((off + len) > 
+                           so->so_msg_state->msg_serial_bytes) {
+                               len = so->so_msg_state->msg_serial_bytes - off;
+                               if (len <= 0) {
+                                       len = 0;
+                                       tcpstat.tcps_msg_sndwaithipri++;
+                               }
+                       }
+               }
+       }

 
        /*
 
        /*

-        * Sender silly window avoidance.  If connection is idle
-        * and can send all data, a maximum segment,
-        * at least a maximum default-size segment do it,
-        * or are forced, do it; otherwise don't bother.
-        * If peer's buffer is tiny, then send
-        * when window is at least half open.
-        * If retransmitting (possibly after persist timer forced us
-        * to send into a small window), then must resend.
+        * Sender silly window avoidance.   We transmit under the following
+        * conditions when len is non-zero:
+        *
+        *      - we've timed out (e.g. persist timer)
+        *      - we need to retransmit
+        *      - We have a full segment (or more with TSO)
+        *      - This is the last buffer in a write()/send() and we are
+        *        either idle or running NODELAY
+        *      - we have more then 1/2 the maximum send window's worth of
+        *        data (receiver may be limited the window size)

         */
        if (len) {
         */
        if (len) {

-               if (len == tp->t_maxseg)
-                       goto send;
-               if (!(tp->t_flags & TF_MORETOCOME) &&
-                   (idle || tp->t_flags & TF_NODELAY) &&
-                   (tp->t_flags & TF_NOPUSH) == 0 &&
-                   len + off >= so->so_snd.sb_cc)
-                       goto send;

                if (tp->t_force)
                        goto send;
                if (tp->t_force)
                        goto send;

-               if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
-                       goto send;

                if (SEQ_LT(tp->snd_nxt, tp->snd_max))
                        goto send;
                if (SEQ_LT(tp->snd_nxt, tp->snd_max))
                        goto send;

+               if (sack_rxmit)
+                       goto send;
+
+               /*
+                * Send new data on the connection only if it is
+                * not flow controlled
+                */
+               if (!INP_WAIT_FOR_IF_FEEDBACK(inp) ||
+                   tp->t_state != TCPS_ESTABLISHED) {
+                       if (len >= tp->t_maxseg)
+                               goto send;
+                       if (!(tp->t_flags & TF_MORETOCOME) &&
+                           (idle || tp->t_flags & TF_NODELAY || 
+                           tp->t_flags & TF_MAXSEGSNT ||
+                           ALLOW_LIMITED_TRANSMIT(tp)) &&
+                           (tp->t_flags & TF_NOPUSH) == 0 &&
+                           len + off >= so->so_snd.sb_cc)
+                               goto send;
+                       if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
+                               goto send;
+               } else {
+                       tcpstat.tcps_fcholdpacket++;
+               }

        }
 
        /*
         * Compare available window to amount of window
         * known to peer (as advertised window less
         * next expected input).  If the difference is at least two
        }
 
        /*
         * Compare available window to amount of window
         * known to peer (as advertised window less
         * next expected input).  If the difference is at least two

-        * max size segments, or at least 50% of the maximum possible
+        * max size segments, or at least 25% of the maximum possible

         * window, then want to send a window update to peer.
         * window, then want to send a window update to peer.

+        * Skip this if the connection is in T/TCP half-open state.

         */
         */

-       if (win > 0) {
+       if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN)) {

                /*
                 * "adv" is the amount we can increase the window,
                 * taking into account that we are limited by
                 * TCP_MAXWIN << tp->rcv_scale.
                 */
                /*
                 * "adv" is the amount we can increase the window,
                 * taking into account that we are limited by
                 * TCP_MAXWIN << tp->rcv_scale.
                 */

-               long adv = min(win, (long)TCP_MAXWIN << tp->rcv_scale) -
+               int32_t adv, oldwin = 0;
+               adv = imin(recwin, (int)TCP_MAXWIN << tp->rcv_scale) -

                        (tp->rcv_adv - tp->rcv_nxt);
 
                        (tp->rcv_adv - tp->rcv_nxt);
 

-               if (adv >= (long) (2 * tp->t_maxseg))
-                       goto send;
-               if (2 * adv >= (long) so->so_rcv.sb_hiwat)
-                       goto send;
+               if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt))
+                       oldwin = tp->rcv_adv - tp->rcv_nxt;
+
+               if (adv >= (int32_t) (2 * tp->t_maxseg)) {
+                       /* Update only if the resulting scaled value of the window changed, or
+                        * if there is a change in the sequence since the last ack.
+                        * This avoids what appears as dupe ACKS (see rdar://5640997)
+                        *
+                        * If streaming is detected avoid sending too many window updates.
+                        * We will depend on the delack timer to send a window update
+                        * when needed.
+                        */
+                       if (!(tp->t_flags & TF_STRETCHACK) &&
+                               (tp->last_ack_sent != tp->rcv_nxt || 
+                               ((oldwin + adv) >> tp->rcv_scale) >
+                               (oldwin >> tp->rcv_scale))) {
+                               goto send;
+                       }
+
+                       /* Make sure that the delayed ack timer is set if we
+                        * delayed sending a window update because of streaming
+                        * detection.
+                        */
+                       if ((tp->t_flags & TF_STRETCHACK) &&
+                               !(tp->t_flags & TF_DELACK)) { 
+                               tp->t_flags |= TF_DELACK;
+                               tp->t_timer[TCPT_DELACK] = 
+                                       OFFSET_FROM_START(tp, tcp_delack);
+                       }
+               }
+               if (4 * adv >= (int32_t) so->so_rcv.sb_hiwat) 
+                               goto send;

        }
 
        /*
        }
 
        /*

-        * Send if we owe peer an ACK.
+        * Send if we owe the peer an ACK, RST, SYN, or urgent data.  ACKNOW
+        * is also a catch-all for the retransmit timer timeout case.

         */
        if (tp->t_flags & TF_ACKNOW)
                goto send;
         */
        if (tp->t_flags & TF_ACKNOW)
                goto send;


@@ -324,15 +985,29 @@ again:
                goto send;
        if (SEQ_GT(tp->snd_up, tp->snd_una))
                goto send;
                goto send;
        if (SEQ_GT(tp->snd_up, tp->snd_una))
                goto send;

+#if MPTCP
+       if (mptcp_acknow)
+               goto send;
+#endif /* MPTCP */

        /*
         * If our state indicates that FIN should be sent
        /*
         * If our state indicates that FIN should be sent

-        * and we have not yet done so, or we're retransmitting the FIN,
-        * then we need to send.
+        * and we have not yet done so, then we need to send.

         */
         */

-       if (flags & TH_FIN &&
-           ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
+       if ((flags & TH_FIN) &&
+           (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una))

                goto send;
                goto send;

-
+       /*
+        * In SACK, it is possible for tcp_output to fail to send a segment
+        * after the retransmission timer has been turned off.  Make sure
+        * that the retransmission timer is set.
+        */
+       if (SACK_ENABLED(tp) && (tp->t_state >= TCPS_ESTABLISHED) && 
+           SEQ_GT(tp->snd_max, tp->snd_una) &&
+           tp->t_timer[TCPT_REXMT] == 0 &&
+           tp->t_timer[TCPT_PERSIST] == 0) {
+               tp->t_timer[TCPT_REXMT] = OFFSET_FROM_START(tp, tp->t_rxtcur);
+               goto just_return;
+       } 

        /*
         * TCP window updates are not reliable, rather a polling protocol
         * using ``persist'' packets is used to insure receipt of window
        /*
         * TCP window updates are not reliable, rather a polling protocol
         * using ``persist'' packets is used to insure receipt of window


@@ -358,31 +1033,67 @@ again:
        if (so->so_snd.sb_cc && tp->t_timer[TCPT_REXMT] == 0 &&
            tp->t_timer[TCPT_PERSIST] == 0) {
                tp->t_rxtshift = 0;
        if (so->so_snd.sb_cc && tp->t_timer[TCPT_REXMT] == 0 &&
            tp->t_timer[TCPT_PERSIST] == 0) {
                tp->t_rxtshift = 0;

+               tp->t_rxtstart = 0;

                tcp_setpersist(tp);
        }
                tcp_setpersist(tp);
        }

-
+just_return:

        /*
        /*

-        * No reason to send a segment, just return.
+        * If there is no reason to send a segment, just return.
+        * but if there is some packets left in the packet list, send them now.

         */
         */

+       while (inp->inp_sndinprog_cnt == 0 &&
+               tp->t_pktlist_head != NULL) {
+               packetlist = tp->t_pktlist_head;
+               packchain_listadd = tp->t_lastchain;
+               packchain_sent++;
+               TCP_PKTLIST_CLEAR(tp);
+
+               error = tcp_ip_output(so, tp, packetlist, packchain_listadd,
+                   tp_inp_options, (so_options & SO_DONTROUTE),
+                   (sack_rxmit | (sack_bytes_rxmt != 0)), recwin,
+#if INET6
+                   isipv6);
+#else /* INET6 */
+                   0);
+#endif /* !INET6 */
+       }
+       /* tcp was closed while we were in ip; resume close */
+       if (inp->inp_sndinprog_cnt == 0 &&
+               (tp->t_flags & TF_CLOSING)) {
+               tp->t_flags &= ~TF_CLOSING;
+               (void) tcp_close(tp);
+       } else {
+               tcp_check_timer_state(tp);
+       }

        KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END, 0,0,0,0,0);
        return (0);
 
 send:
        KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END, 0,0,0,0,0);
        return (0);
 
 send:

+       /* 
+        * Set TF_MAXSEGSNT flag if the segment size is greater than
+        * the max segment size.
+        */
+       if (len > 0) {
+               if (len >= tp->t_maxseg)
+                       tp->t_flags |= TF_MAXSEGSNT;
+               else
+                       tp->t_flags &= ~TF_MAXSEGSNT;
+       }

        /*
         * Before ESTABLISHED, force sending of initial options
         * unless TCP set not to do any options.
         * NOTE: we assume that the IP/TCP header plus TCP options
         * always fit in a single mbuf, leaving room for a maximum
         * link header, i.e.
        /*
         * Before ESTABLISHED, force sending of initial options
         * unless TCP set not to do any options.
         * NOTE: we assume that the IP/TCP header plus TCP options
         * always fit in a single mbuf, leaving room for a maximum
         * link header, i.e.

-        *      max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MHLEN
+        *      max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES

         */
        optlen = 0;
 #if INET6
        if (isipv6)
         */
        optlen = 0;
 #if INET6
        if (isipv6)

-               hdrlen = sizeof (struct tcpip6hdr);
+               hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr);

        else
 #endif
        else
 #endif

-       hdrlen = sizeof (struct tcpiphdr);
+               hdrlen = sizeof (struct tcpiphdr);

        if (flags & TH_SYN) {
                tp->snd_nxt = tp->iss;
                if ((tp->t_flags & TF_NOOPT) == 0) {
        if (flags & TH_SYN) {
                tp->snd_nxt = tp->iss;
                if ((tp->t_flags & TF_NOOPT) == 0) {


@@ -390,22 +1101,110 @@ send:
 
                        opt[0] = TCPOPT_MAXSEG;
                        opt[1] = TCPOLEN_MAXSEG;
 
                        opt[0] = TCPOPT_MAXSEG;
                        opt[1] = TCPOLEN_MAXSEG;

-                       mss = htons((u_short) tcp_mssopt(tp, isipv6));
+                       mss = htons((u_short) tcp_mssopt(tp));

                        (void)memcpy(opt + 2, &mss, sizeof(mss));
                        optlen = TCPOLEN_MAXSEG;
 
                        if ((tp->t_flags & TF_REQ_SCALE) &&
                            ((flags & TH_ACK) == 0 ||
                            (tp->t_flags & TF_RCVD_SCALE))) {
                        (void)memcpy(opt + 2, &mss, sizeof(mss));
                        optlen = TCPOLEN_MAXSEG;
 
                        if ((tp->t_flags & TF_REQ_SCALE) &&
                            ((flags & TH_ACK) == 0 ||
                            (tp->t_flags & TF_RCVD_SCALE))) {

-                               *((u_int32_t *)(opt + optlen)) = htonl(
+                               *((u_int32_t *)(void *)(opt + optlen)) = htonl(

                                        TCPOPT_NOP << 24 |
                                        TCPOPT_WINDOW << 16 |
                                        TCPOLEN_WINDOW << 8 |
                                        tp->request_r_scale);
                                optlen += 4;
                        }
                                        TCPOPT_NOP << 24 |
                                        TCPOPT_WINDOW << 16 |
                                        TCPOLEN_WINDOW << 8 |
                                        tp->request_r_scale);
                                optlen += 4;
                        }

+#if MPTCP
+                       if (mptcp_enable) {
+                               optlen = mptcp_setup_syn_opts(so, flags, opt,
+                                   optlen);
+                       }
+#endif /* MPTCP */

                }
        }
                }
        }

+       
+       /*
+         RFC 3168 states that:
+          - If you ever sent an ECN-setup SYN/SYN-ACK you must be prepared
+          to handle the TCP ECE flag, even if you also later send a
+          non-ECN-setup SYN/SYN-ACK.
+          - If you ever send a non-ECN-setup SYN/SYN-ACK, you must not set
+          the ip ECT flag.
+          
+          It is not clear how the ECE flag would ever be set if you never
+          set the IP ECT flag on outbound packets. All the same, we use
+          the TE_SETUPSENT to indicate that we have committed to handling
+          the TCP ECE flag correctly. We use the TE_SENDIPECT to indicate
+          whether or not we should set the IP ECT flag on outbound packets.
+        */
+       /*
+        * For a SYN-ACK, send an ECN setup SYN-ACK
+        */
+       if (tcp_ecn_inbound && (flags & (TH_SYN | TH_ACK)) == (TH_SYN | TH_ACK)) {
+               if ((tp->ecn_flags & TE_SETUPRECEIVED) != 0) {
+                       if ((tp->ecn_flags & TE_SETUPSENT) == 0) {
+                               /* Setting TH_ECE makes this an ECN-setup SYN-ACK */
+                               flags |= TH_ECE;
+                               
+                               /*
+                                * Record that we sent the ECN-setup and default to
+                                * setting IP ECT.
+                                */
+                               tp->ecn_flags |= (TE_SETUPSENT | TE_SENDIPECT);
+                       }
+                       else {
+                               /*
+                                * We sent an ECN-setup SYN-ACK but it was dropped.
+                                * Fallback to non-ECN-setup SYN-ACK and clear flag
+                                * that to indicate we should not send data with IP ECT set.
+                                *
+                                * Pretend we didn't receive an ECN-setup SYN.
+                                */
+                               tp->ecn_flags &= ~TE_SETUPRECEIVED;
+                       }
+               }
+       }
+       else if (tcp_ecn_outbound && (flags & (TH_SYN | TH_ACK)) == TH_SYN) {
+               if ((tp->ecn_flags & TE_SETUPSENT) == 0) {
+                       /* Setting TH_ECE and TH_CWR makes this an ECN-setup SYN */
+                       flags |= (TH_ECE | TH_CWR);
+                       
+                       /*
+                        * Record that we sent the ECN-setup and default to
+                        * setting IP ECT.
+                        */
+                       tp->ecn_flags |= (TE_SETUPSENT | TE_SENDIPECT);
+               }
+               else {
+                       /*
+                        * We sent an ECN-setup SYN but it was dropped.
+                        * Fall back to no ECN and clear flag indicating
+                        * we should send data with IP ECT set.
+                        */
+                       tp->ecn_flags &= ~TE_SENDIPECT;
+               }
+       }
+       
+       /*
+        * Check if we should set the TCP CWR flag.
+        * CWR flag is sent when we reduced the congestion window because
+        * we received a TCP ECE or we performed a fast retransmit. We
+        * never set the CWR flag on retransmitted packets. We only set
+        * the CWR flag on data packets. Pure acks don't have this set.
+        */
+       if ((tp->ecn_flags & TE_SENDCWR) != 0 && len != 0 &&
+               !SEQ_LT(tp->snd_nxt, tp->snd_max) && !sack_rxmit) {
+               flags |= TH_CWR;
+               tp->ecn_flags &= ~TE_SENDCWR;
+       }
+       
+       /*
+        * Check if we should set the TCP ECE flag.
+        */
+       if ((tp->ecn_flags & TE_SENDECE) != 0 && len == 0) {
+               flags |= TH_ECE;
+       }

 
        /*
         * Send a timestamp and echo-reply if this is a SYN and our side
 
        /*
         * Send a timestamp and echo-reply if this is a SYN and our side


@@ -416,7 +1215,7 @@ send:
            (flags & TH_RST) == 0 &&
            ((flags & TH_ACK) == 0 ||
             (tp->t_flags & TF_RCVD_TSTMP))) {
            (flags & TH_RST) == 0 &&
            ((flags & TH_ACK) == 0 ||
             (tp->t_flags & TF_RCVD_TSTMP))) {

-               u_int32_t *lp = (u_int32_t *)(opt + optlen);
+               u_int32_t *lp = (u_int32_t *)(void *)(opt + optlen);

 
                /* Form timestamp option as shown in appendix A of RFC 1323. */
                *lp++ = htonl(TCPOPT_TSTAMP_HDR);
 
                /* Form timestamp option as shown in appendix A of RFC 1323. */
                *lp++ = htonl(TCPOPT_TSTAMP_HDR);


@@ -425,95 +1224,130 @@ send:
                optlen += TCPOLEN_TSTAMP_APPA;
        }
 
                optlen += TCPOLEN_TSTAMP_APPA;
        }
 

-       /*
-        * Send `CC-family' options if our side wants to use them (TF_REQ_CC),
-        * options are allowed (!TF_NOOPT) and it's not a RST.
-        */
-       if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC &&
-            (flags & TH_RST) == 0) {
-               switch (flags & (TH_SYN|TH_ACK)) {
-               /*
-                * This is a normal ACK, send CC if we received CC before
-                * from our peer.
-                */
-               case TH_ACK:
-                       if (!(tp->t_flags & TF_RCVD_CC))
-                               break;
-                       /*FALLTHROUGH*/
+       /* Note the timestamp for receive buffer autosizing */
+       if (tp->rfbuf_ts == 0 && (so->so_rcv.sb_flags & SB_AUTOSIZE))
+               tp->rfbuf_ts = tcp_now;

 
 

+       if (SACK_ENABLED(tp) && ((tp->t_flags & TF_NOOPT) == 0)) {
+               /* 
+                * Tack on the SACK permitted option *last*.
+                * And do padding of options after tacking this on.
+                * This is because of MSS, TS, WinScale and Signatures are
+                * all present, we have just 2 bytes left for the SACK
+                * permitted option, which is just enough.
+                */

                /*
                /*

-                * We can only get here in T/TCP's SYN_SENT* state, when
-                * we're a sending a non-SYN segment without waiting for
-                * the ACK of our SYN.  A check above assures that we only
-                * do this if our peer understands T/TCP.
+                * If this is the first SYN of connection (not a SYN
+                * ACK), include SACK permitted option.  If this is a
+                * SYN ACK, include SACK permitted option if peer has
+                * already done so. This is only for active connect,
+                * since the syncache takes care of the passive connect.

                 */
                 */

-               case 0:
-                       opt[optlen++] = TCPOPT_NOP;
-                       opt[optlen++] = TCPOPT_NOP;
-                       opt[optlen++] = TCPOPT_CC;
-                       opt[optlen++] = TCPOLEN_CC;
-                       *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send);
-
-                       optlen += 4;
-                       break;
+               if ((flags & TH_SYN) &&
+                   (!(flags & TH_ACK) || (tp->t_flags & TF_SACK_PERMIT))) {
+                       u_char *bp;
+                       bp = (u_char *)opt + optlen;

 
 

+                       *bp++ = TCPOPT_SACK_PERMITTED;
+                       *bp++ = TCPOLEN_SACK_PERMITTED;
+                       optlen += TCPOLEN_SACK_PERMITTED;
+               }
+       }
+#if MPTCP
+       if (so->so_flags & SOF_MP_SUBFLOW) {

                /*
                /*

-                * This is our initial SYN, check whether we have to use
-                * CC or CC.new.
+                * Its important to piggyback acks with data as ack only packets
+                * may get lost and data packets that don't send Data ACKs
+                * still advance the subflow level ACK and therefore make it
+                * hard for the remote end to recover in low cwnd situations.

                 */
                 */

-               case TH_SYN:
-                       opt[optlen++] = TCPOPT_NOP;
-                       opt[optlen++] = TCPOPT_NOP;
-                       opt[optlen++] = tp->t_flags & TF_SENDCCNEW ?
-                                               TCPOPT_CCNEW : TCPOPT_CC;
-                       opt[optlen++] = TCPOLEN_CC;
-                       *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send);
-                       optlen += 4;
-                       break;
+               if (len != 0)
+                       tp->t_mpflags |= (TMPF_SEND_DSN |
+                           TMPF_MPTCP_ACKNOW);
+               else
+                       tp->t_mpflags |= TMPF_MPTCP_ACKNOW;
+               optlen = mptcp_setup_opts(tp, off, &opt[0], optlen, flags,
+                   len, &dlenp, &finp, &dss_val, &sseqp);
+               tp->t_mpflags &= ~TMPF_SEND_DSN;
+       }
+#endif /* MPTCP */

 
 

+       if (SACK_ENABLED(tp) && ((tp->t_flags & TF_NOOPT) == 0)) {

                /*
                /*

-                * This is a SYN,ACK; send CC and CC.echo if we received
-                * CC from our peer.
+                * Send SACKs if necessary.  This should be the last
+                * option processed.  Only as many SACKs are sent as
+                * are permitted by the maximum options size.
+                *
+                * In general, SACK blocks consume 8*n+2 bytes.
+                * So a full size SACK blocks option is 34 bytes
+                * (to generate 4 SACK blocks).  At a minimum,
+                * we need 10 bytes (to generate 1 SACK block).
+                * If TCP Timestamps (12 bytes) and TCP Signatures
+                * (18 bytes) are both present, we'll just have
+                * 10 bytes for SACK options 40 - (12 + 18).

                 */
                 */

-               case (TH_SYN|TH_ACK):
-                       if (tp->t_flags & TF_RCVD_CC) {
-                               opt[optlen++] = TCPOPT_NOP;
-                               opt[optlen++] = TCPOPT_NOP;
-                               opt[optlen++] = TCPOPT_CC;
-                               opt[optlen++] = TCPOLEN_CC;
-                               *(u_int32_t *)&opt[optlen] =
-                                       htonl(tp->cc_send);
-                               optlen += 4;
-                               opt[optlen++] = TCPOPT_NOP;
-                               opt[optlen++] = TCPOPT_NOP;
-                               opt[optlen++] = TCPOPT_CCECHO;
-                               opt[optlen++] = TCPOLEN_CC;
-                               *(u_int32_t *)&opt[optlen] =
-                                       htonl(tp->cc_recv);
-                               optlen += 4;
+               if (TCPS_HAVEESTABLISHED(tp->t_state) &&
+                   (tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks > 0 &&
+                   MAX_TCPOPTLEN - optlen - 2 >= TCPOLEN_SACK) {
+                       int nsack, padlen;
+                       u_char *bp = (u_char *)opt + optlen;
+                       u_int32_t *lp;
+
+                       nsack = (MAX_TCPOPTLEN - optlen - 2) / TCPOLEN_SACK;
+                       nsack = min(nsack, tp->rcv_numsacks);
+                       sackoptlen = (2 + nsack * TCPOLEN_SACK);
+
+                       /*
+                        * First we need to pad options so that the
+                        * SACK blocks can start at a 4-byte boundary
+                        * (sack option and length are at a 2 byte offset).
+                        */
+                       padlen = (MAX_TCPOPTLEN - optlen - sackoptlen) % 4;
+                       optlen += padlen;
+                       while (padlen-- > 0)
+                               *bp++ = TCPOPT_NOP;
+
+                       tcpstat.tcps_sack_send_blocks++;
+                       *bp++ = TCPOPT_SACK;
+                       *bp++ = sackoptlen;
+                       lp = (u_int32_t *)(void *)bp;
+                       for (i = 0; i < nsack; i++) {
+                               struct sackblk sack = tp->sackblks[i];
+                               *lp++ = htonl(sack.start);
+                               *lp++ = htonl(sack.end);

                        }
                        }

-                       break;
+                       optlen += sackoptlen;

                }
                }

-       }
+       }
+
+       /* Pad TCP options to a 4 byte boundary */
+       if (optlen < MAX_TCPOPTLEN && (optlen % sizeof(u_int32_t))) {
+               int pad = sizeof(u_int32_t) - (optlen % sizeof(u_int32_t));
+               u_char *bp = (u_char *)opt + optlen;
+
+               optlen += pad;
+               while (pad) {
+                       *bp++ = TCPOPT_EOL;
+                       pad--;
+               }
+       }
+
+       hdrlen += optlen;

 
 

-       hdrlen += optlen;

 #if INET6
        if (isipv6)
 #if INET6
        if (isipv6)

-               ipoptlen = ip6_optlen(tp->t_inpcb);
+               ipoptlen = ip6_optlen(inp);

        else
 #endif
        else
 #endif

-       if (tp->t_inpcb->inp_options) {
-               ipoptlen = tp->t_inpcb->inp_options->m_len -
+       {
+               if (tp_inp_options) {
+                       ipoptlen = tp_inp_options->m_len -

                                offsetof(struct ipoption, ipopt_list);
                                offsetof(struct ipoption, ipopt_list);

-       } else {
-               ipoptlen = 0;
+               } else
+                       ipoptlen = 0;

        }
 #if IPSEC
        }
 #if IPSEC

-#if INET6
-       ipoptlen += ipsec_hdrsiz_tcp(tp, isipv6);
-#else
-       ipoptlen += ipsec_hdrsiz_tcp(tp, 0);
-#endif
+               ipoptlen += ipsec_optlen;

 #endif
 
        /*
 #endif
 
        /*


@@ -521,21 +1355,74 @@ send:
         * bump the packet length beyond the t_maxopd length.
         * Clear the FIN bit because we cut off the tail of
         * the segment.
         * bump the packet length beyond the t_maxopd length.
         * Clear the FIN bit because we cut off the tail of
         * the segment.

+        *
+        * When doing TSO limit a burst to TCP_MAXWIN minus the
+        * IP, TCP and Options length to keep ip->ip_len from
+        * overflowing.  Prevent the last segment from being
+        * fractional thus making them all equal sized and set
+        * the flag to continue sending.  TSO is disabled when
+        * IP options or IPSEC are present.

         */
        if (len + optlen + ipoptlen > tp->t_maxopd) {
                /*
                 * If there is still more to send, don't close the connection.
                 */
                flags &= ~TH_FIN;
         */
        if (len + optlen + ipoptlen > tp->t_maxopd) {
                /*
                 * If there is still more to send, don't close the connection.
                 */
                flags &= ~TH_FIN;

-               len = tp->t_maxopd - optlen - ipoptlen;
-               sendalot = 1;
-       }
+               if (tso) {
+                       int32_t tso_maxlen;

 
 

-/*#ifdef DIAGNOSTIC*/
-       if (max_linkhdr + hdrlen > MHLEN)
+                       tso_maxlen = tp->tso_max_segment_size ? tp->tso_max_segment_size : TCP_MAXWIN;
+
+                       if (len > tso_maxlen - hdrlen - optlen) {
+                               len = tso_maxlen - hdrlen - optlen;
+                               len = len - (len % (tp->t_maxopd - optlen));
+                               sendalot = 1;
+                       } else if (tp->t_flags & TF_NEEDFIN)
+                               sendalot = 1;
+               } else {
+                       len = tp->t_maxopd - optlen - ipoptlen;
+                       sendalot = 1;
+               }
+       }
+#if MPTCP
+       /* Adjust the length in the DSS option, if it is lesser than len */
+       if (dlenp) {
+               /*
+                * To test this path without SACK, artificially
+                * decrement len with something like
+                * if (len > 10)
+                       len -= 10;
+                */
+               if (ntohs(*dlenp) > len) {
+                       *dlenp = htons(len);
+                       /* Unset the FIN flag, if len was adjusted */
+                       if (finp) {
+                               *finp &= ~MDSS_F;
+                       }
+                       sendalot = 1;
+               }
+       }
+#endif /* MPTCP */
+
+       if (max_linkhdr + hdrlen > MCLBYTES)

                panic("tcphdr too big");
                panic("tcphdr too big");

-/*#endif*/

 
 

+       /* Check if there is enough data in the send socket
+        * buffer to start measuring bw 
+        */
+       if ((tp->t_flagsext & TF_MEASURESNDBW) != 0 &&
+               (tp->t_bwmeas != NULL) &&
+               (tp->t_flagsext & TF_BWMEAS_INPROGRESS) == 0 &&
+               (so->so_snd.sb_cc - (tp->snd_max - tp->snd_una)) >= 
+                       tp->t_bwmeas->bw_minsize) {
+               tp->t_bwmeas->bw_size = min((so->so_snd.sb_cc - (tp->snd_max - tp->snd_una)),
+                       tp->t_bwmeas->bw_maxsize);
+               tp->t_flagsext |= TF_BWMEAS_INPROGRESS;
+               tp->t_bwmeas->bw_start = tp->snd_max;
+               tp->t_bwmeas->bw_ts = tcp_now;
+       }
+
+       VERIFY(inp->inp_flowhash != 0);

        /*
         * Grab a header mbuf, attaching a copy of data to
         * be transmitted, and initialize the header from
        /*
         * Grab a header mbuf, attaching a copy of data to
         * be transmitted, and initialize the header from


@@ -544,55 +1431,156 @@ send:
        if (len) {
                if (tp->t_force && len == 1)
                        tcpstat.tcps_sndprobe++;
        if (len) {
                if (tp->t_force && len == 1)
                        tcpstat.tcps_sndprobe++;

-               else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) {
+               else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) {

                        tcpstat.tcps_sndrexmitpack++;
                        tcpstat.tcps_sndrexmitbyte += len;
                        tcpstat.tcps_sndrexmitpack++;
                        tcpstat.tcps_sndrexmitbyte += len;

+                       if (nstat_collect) {
+                               nstat_route_tx(inp->inp_route.ro_rt, 1,
+                                       len, NSTAT_TX_FLAG_RETRANSMIT);
+                               INP_ADD_STAT(inp, cell, wifi, txpackets, 1);
+                               INP_ADD_STAT(inp, cell, wifi, txbytes, len);
+                               tp->t_stat.txretransmitbytes += len;
+                       }

                } else {
                        tcpstat.tcps_sndpack++;
                        tcpstat.tcps_sndbyte += len;
                } else {
                        tcpstat.tcps_sndpack++;
                        tcpstat.tcps_sndbyte += len;

+                       
+                       if (nstat_collect) {
+                               INP_ADD_STAT(inp, cell, wifi, txpackets, 1);
+                               INP_ADD_STAT(inp, cell, wifi, txbytes, len);
+                       }

                }
                }

-#ifdef notyet
-               if ((m = m_copypack(so->so_snd.sb_mb, off,
-                   (int)len, max_linkhdr + hdrlen)) == 0) {
-                       error = ENOBUFS;
-                       goto out;
+#if MPTCP
+               if (tp->t_mpflags & TMPF_MPTCP_TRUE) {
+                       tcpstat.tcps_mp_sndpacks++;
+                       tcpstat.tcps_mp_sndbytes += len;

                }
                }

+#endif /* MPTCP */

                /*
                /*

-                * m_copypack left space for our hdr; use it.
+                * try to use the new interface that allocates all 
+                * the necessary mbuf hdrs under 1 mbuf lock and 
+                * avoids rescanning the socket mbuf list if 
+                * certain conditions are met.  This routine can't
+                * be used in the following cases...
+                * 1) the protocol headers exceed the capacity of
+                * of a single mbuf header's data area (no cluster attached)
+                * 2) the length of the data being transmitted plus
+                * the protocol headers fits into a single mbuf header's
+                * data area (no cluster attached)

                 */
                 */

-               m->m_len += hdrlen;
-               m->m_data -= hdrlen;
-#else
-               MGETHDR(m, M_DONTWAIT, MT_HEADER);
-               if (m == NULL) {
-                       error = ENOBUFS;
-                       goto out;
-               }
-#if INET6
+               m = NULL;
+
+               /* minimum length we are going to allocate */
+               allocated_len = MHLEN;

                if (MHLEN < hdrlen + max_linkhdr) {
                if (MHLEN < hdrlen + max_linkhdr) {

+                       MGETHDR(m, M_DONTWAIT, MT_HEADER);
+                       if (m == NULL) {
+                               error = ENOBUFS;
+                               goto out;
+                       }

                        MCLGET(m, M_DONTWAIT);
                        if ((m->m_flags & M_EXT) == 0) {
                                m_freem(m);
                                error = ENOBUFS;
                                goto out;
                        }
                        MCLGET(m, M_DONTWAIT);
                        if ((m->m_flags & M_EXT) == 0) {
                                m_freem(m);
                                error = ENOBUFS;
                                goto out;
                        }

+                       m->m_data += max_linkhdr;
+                       m->m_len = hdrlen;
+                       allocated_len = MCLBYTES;

                }
                }

-#endif
-               m->m_data += max_linkhdr;
-               m->m_len = hdrlen;
-               if (len <= MHLEN - hdrlen - max_linkhdr) {
+               if (len <= allocated_len - hdrlen - max_linkhdr) {
+                       if (m == NULL) {
+                               VERIFY(allocated_len <= MHLEN);
+                               MGETHDR(m, M_DONTWAIT, MT_HEADER);
+                               if (m == NULL) {
+                                       error = ENOBUFS;
+                                       goto out;
+                               }
+                               m->m_data += max_linkhdr;
+                               m->m_len = hdrlen;
+                       }
+                       /* makes sure we still have data left to be sent at this point */
+                       if (so->so_snd.sb_mb == NULL || off < 0) {
+                               if (m != NULL)  m_freem(m);
+                               error = 0; /* should we return an error? */
+                               goto out;
+                       }

                        m_copydata(so->so_snd.sb_mb, off, (int) len,
                            mtod(m, caddr_t) + hdrlen);
                        m->m_len += len;
                } else {
                        m_copydata(so->so_snd.sb_mb, off, (int) len,
                            mtod(m, caddr_t) + hdrlen);
                        m->m_len += len;
                } else {

-                       m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len);
-                       if (m->m_next == 0) {
-                               (void) m_free(m);
-                               error = ENOBUFS;
-                               goto out;
+                       uint32_t copymode;
+                       /*
+                        * Retain packet header metadata at the socket
+                        * buffer if this is is an MPTCP subflow,
+                        * otherwise move it.
+                        */
+                       copymode = M_COPYM_MOVE_HDR;
+#if MPTCP
+                       if ((tp->t_mpflags & TMPF_MPTCP_TRUE) ||
+                           (tp->t_mpflags & TMPF_TCP_FALLBACK)) {
+                               copymode = M_COPYM_NOOP_HDR;
+                       }
+#endif /* MPTCP */
+                       if (m != NULL) {
+                               m->m_next = m_copym_mode(so->so_snd.sb_mb, off,
+                                   (int) len, M_DONTWAIT, copymode);
+                               if (m->m_next == NULL) {
+                                       (void) m_free(m);
+                                       error = ENOBUFS;
+                                       goto out;
+                               }
+                       } else {
+                               /*
+                                * determine whether the mbuf pointer and
+                                * offset passed back by the 'last' call to
+                                * m_copym_with_hdrs are still valid... if the
+                                * head of the socket chain has changed (due
+                                * to an incoming ACK for instance), or the
+                                * offset into the chain we just computed is
+                                * different from the one last returned by
+                                * m_copym_with_hdrs (perhaps we're re-
+                                * transmitting a packet sent earlier), then
+                                * we can't pass the mbuf pointer and offset
+                                * into it as valid hints for m_copym_with_hdrs
+                                * to use (if valid, these hints allow
+                                * m_copym_with_hdrs to avoid rescanning from
+                                * the beginning of the socket buffer mbuf list.
+                                *
+                                * Setting the mbuf pointer to NULL is
+                                * sufficient to disable the hint mechanism.
+                                */
+                               if (m_head != so->so_snd.sb_mb || sack_rxmit ||
+                                   last_off != off)
+                                       m_lastm = NULL;
+                               last_off = off + len;
+                               m_head = so->so_snd.sb_mb;
+
+                               /*
+                                * make sure we still have data left
+                                * to be sent at this point
+                                */
+                               if (m_head == NULL) {
+                                       error = 0; /* should we return an error? */
+                                       goto out;
+                               }
+
+                               /*
+                                * m_copym_with_hdrs will always return the
+                                * last mbuf pointer and the offset into it that
+                                * it acted on to fullfill the current request,
+                                * whether a valid 'hint' was passed in or not.
+                                */
+                               if ((m = m_copym_with_hdrs(so->so_snd.sb_mb,
+                                   off, len, M_DONTWAIT, &m_lastm, &m_off,
+                                   copymode)) == NULL) {
+                                       error = ENOBUFS;
+                                       goto out;
+                               }
+                               m->m_data += max_linkhdr;
+                               m->m_len = hdrlen;

                        }
                }
                        }
                }

-#endif

                /*
                 * If we're sending everything we've got, set PUSH.
                 * (This will keep happy those implementations which only
                /*
                 * If we're sending everything we've got, set PUSH.
                 * (This will keep happy those implementations which only


@@ -611,48 +1599,60 @@ send:
                else
                        tcpstat.tcps_sndwinup++;
 
                else
                        tcpstat.tcps_sndwinup++;
 

-               MGETHDR(m, M_DONTWAIT, MT_HEADER);
+               MGETHDR(m, M_DONTWAIT, MT_HEADER);      /* MAC-OK */

                if (m == NULL) {
                        error = ENOBUFS;
                        goto out;
                }
                if (m == NULL) {
                        error = ENOBUFS;
                        goto out;
                }

-#if INET6
-               if (isipv6) {
-                       MH_ALIGN(m, hdrlen);
-               } else
-#endif
+               if (MHLEN < (hdrlen + max_linkhdr)) {
+                       MCLGET(m, M_DONTWAIT);
+                       if ((m->m_flags & M_EXT) == 0) {
+                               m_freem(m);
+                               error = ENOBUFS;
+                               goto out;
+                       }
+               }

                m->m_data += max_linkhdr;
                m->m_len = hdrlen;
        }
                m->m_data += max_linkhdr;
                m->m_len = hdrlen;
        }

-       m->m_pkthdr.rcvif = (struct ifnet *)0;
-       if (tp->t_template == 0)
-               panic("tcp_output");
+       m->m_pkthdr.rcvif = 0;
+#if MPTCP
+       /* Before opt is copied to the mbuf, set the csum field */
+       mptcp_output_csum(tp, m, len, hdrlen, dss_val, sseqp);
+#endif /* MPTCP */
+#if CONFIG_MACF_NET
+       mac_mbuf_label_associate_inpcb(inp, m);
+#endif

 #if INET6
        if (isipv6) {
                ip6 = mtod(m, struct ip6_hdr *);
 #if INET6
        if (isipv6) {
                ip6 = mtod(m, struct ip6_hdr *);

-               th = (struct tcphdr *)(ip6 + 1);
-               bcopy((caddr_t)&tp->t_template->tt_i6, (caddr_t)ip6,
-                     sizeof(struct ip6_hdr));
-               bcopy((caddr_t)&tp->t_template->tt_t, (caddr_t)th,
-                     sizeof(struct tcphdr));
-       } else {
+               th = (struct tcphdr *)(void *)(ip6 + 1);
+               tcp_fillheaders(tp, ip6, th);
+               if ((tp->ecn_flags & TE_SENDIPECT) != 0 && len &&
+                       !SEQ_LT(tp->snd_nxt, tp->snd_max) && !sack_rxmit) {
+                       ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20);
+               }
+               svc_flags |= PKT_SCF_IPV6;
+       } else

 #endif /* INET6 */
 #endif /* INET6 */

-       ip = mtod(m, struct ip *);
-       ipov = (struct ipovly *)ip;
-       th = (struct tcphdr *)(ip + 1);
-       bcopy((caddr_t)&tp->t_template->tt_i, (caddr_t)ip, sizeof(struct ip));
-       bcopy((caddr_t)&tp->t_template->tt_t, (caddr_t)th,
-             sizeof(struct tcphdr));
-#if INET6
+       {
+               ip = mtod(m, struct ip *);
+               ipov = (struct ipovly *)ip;
+               th = (struct tcphdr *)(void *)(ip + 1);
+               /* this picks up the pseudo header (w/o the length) */
+               tcp_fillheaders(tp, ip, th);
+               if ((tp->ecn_flags & TE_SENDIPECT) != 0 && len &&
+                       !SEQ_LT(tp->snd_nxt, tp->snd_max) && !sack_rxmit) {
+                       ip->ip_tos = IPTOS_ECN_ECT0;
+               }

        }
        }

-#endif /* INET6 */

 
        /*
         * Fill in fields, remembering maximum advertised
         * window for use in delaying messages about window sizes.
         * If resending a FIN, be sure not to use a new sequence number.
         */
 
        /*
         * Fill in fields, remembering maximum advertised
         * window for use in delaying messages about window sizes.
         * If resending a FIN, be sure not to use a new sequence number.
         */

-       if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
+       if (flags & TH_FIN && (tp->t_flags & TF_SENTFIN) &&

            tp->snd_nxt == tp->snd_max)
                tp->snd_nxt--;
        /*
            tp->snd_nxt == tp->snd_max)
                tp->snd_nxt--;
        /*


@@ -668,11 +1668,19 @@ send:
         * case, since we know we aren't doing a retransmission.
         * (retransmit and persist are mutually exclusive...)
         */
         * case, since we know we aren't doing a retransmission.
         * (retransmit and persist are mutually exclusive...)
         */

-       if (len || (flags & (TH_SYN|TH_FIN)) || tp->t_timer[TCPT_PERSIST])
-               th->th_seq = htonl(tp->snd_nxt);
-       else
-               th->th_seq = htonl(tp->snd_max);
+       if (sack_rxmit == 0) {
+               if (len || (flags & (TH_SYN|TH_FIN)) || tp->t_timer[TCPT_PERSIST])
+                       th->th_seq = htonl(tp->snd_nxt);
+               else
+                       th->th_seq = htonl(tp->snd_max);
+       } else {
+               th->th_seq = htonl(p->rxmit);
+               p->rxmit += len;
+               tp->sackhint.sack_bytes_rexmit += len;
+       }

        th->th_ack = htonl(tp->rcv_nxt);
        th->th_ack = htonl(tp->rcv_nxt);

+       tp->last_ack_sent = tp->rcv_nxt;
+

        if (optlen) {
                bcopy(opt, th + 1, optlen);
                th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
        if (optlen) {
                bcopy(opt, th + 1, optlen);
                th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;


@@ -682,17 +1690,51 @@ send:
         * Calculate receive window.  Don't shrink window,
         * but avoid silly window syndrome.
         */
         * Calculate receive window.  Don't shrink window,
         * but avoid silly window syndrome.
         */

-       if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)tp->t_maxseg)
-               win = 0;
-       if (win < (long)(tp->rcv_adv - tp->rcv_nxt))
-               win = (long)(tp->rcv_adv - tp->rcv_nxt);
-       if (win > (long)TCP_MAXWIN << tp->rcv_scale)
-               win = (long)TCP_MAXWIN << tp->rcv_scale;
-       th->th_win = htons((u_short) (win>>tp->rcv_scale));
+       if (recwin < (int32_t)(so->so_rcv.sb_hiwat / 4) && recwin < (int)tp->t_maxseg)
+               recwin = 0;
+       if (recwin < (int32_t)(tp->rcv_adv - tp->rcv_nxt))
+               recwin = (int32_t)(tp->rcv_adv - tp->rcv_nxt);
+       if (tp->t_flags & TF_SLOWLINK && slowlink_wsize > 0) {
+               if (recwin > (int32_t)slowlink_wsize) 
+                       recwin = slowlink_wsize;
+       }
+
+#if TRAFFIC_MGT
+       if (tcp_recv_bg == 1  || IS_TCP_RECV_BG(so)) {
+               if (tcp_recv_throttle(tp)) {
+                       uint32_t min_iaj_win = 
+                               tcp_min_iaj_win * tp->t_maxseg;
+                       if (tp->iaj_rwintop == 0 ||
+                               SEQ_LT(tp->iaj_rwintop, tp->rcv_adv))
+                               tp->iaj_rwintop = tp->rcv_adv; 
+                       if (SEQ_LT(tp->iaj_rwintop, 
+                               tp->rcv_nxt + min_iaj_win))
+                               tp->iaj_rwintop =  tp->rcv_nxt + min_iaj_win;
+                       recwin = min(tp->iaj_rwintop - tp->rcv_nxt, recwin);
+               }
+       }
+#endif /* TRAFFIC_MGT */
+
+       if (recwin > (int32_t)(TCP_MAXWIN << tp->rcv_scale))
+               recwin = (int32_t)(TCP_MAXWIN << tp->rcv_scale);
+       th->th_win = htons((u_short) (recwin>>tp->rcv_scale));
+
+       /*
+        * Adjust the RXWIN0SENT flag - indicate that we have advertised
+        * a 0 window.  This may cause the remote transmitter to stall.  This
+        * flag tells soreceive() to disable delayed acknowledgements when
+        * draining the buffer.  This can occur if the receiver is attempting
+        * to read more data then can be buffered prior to transmitting on
+        * the connection.
+        */
+       if (th->th_win == 0)
+               tp->t_flags |= TF_RXWIN0SENT;
+       else
+               tp->t_flags &= ~TF_RXWIN0SENT;

        if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
                th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));
                th->th_flags |= TH_URG;
        if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
                th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));
                th->th_flags |= TH_URG;

-       } else
+       } else {

                /*
                 * If no urgent pointer to send, then we pull
                 * the urgent pointer to the left edge of the send window
                /*
                 * If no urgent pointer to send, then we pull
                 * the urgent pointer to the left edge of the send window


@@ -700,35 +1742,50 @@ send:
                 * number wraparound.
                 */
                tp->snd_up = tp->snd_una;               /* drag it along */
                 * number wraparound.
                 */
                tp->snd_up = tp->snd_una;               /* drag it along */

+       }

 
        /*
         * Put TCP length in extended header, and then
         * checksum extended header and data.
         */
 
        /*
         * Put TCP length in extended header, and then
         * checksum extended header and data.
         */

-       m->m_pkthdr.len = hdrlen + len;
+       m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */

 #if INET6
        if (isipv6) {
 #if INET6
        if (isipv6) {

-#if 0          /* ip6_plen will be filled in ip6_output. */
-               ip6->ip6_plen = htons((u_short)(sizeof(struct tcphdr) +
-                                               optlen + len));
-#endif
-
-               th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr),
-                                      sizeof(struct tcphdr) + optlen + len);
-       } else 
+               /*
+                * ip6_plen is not need to be filled now, and will be filled
+                * in ip6_output.
+                */
+               m->m_pkthdr.csum_flags = CSUM_TCPIPV6;
+               m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
+               if (len + optlen)
+                       th->th_sum = in_addword(th->th_sum, 
+                               htons((u_short)(optlen + len)));
+       }
+       else

 #endif /* INET6 */
        {
 #endif /* INET6 */
        {

-
-       if (len + optlen)
-               ipov->ih_len = htons((u_short)(sizeof (struct tcphdr) +
-                                              optlen + len));
-         m->m_pkthdr.csum_flags = CSUM_TCP;
-                m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
-                if (len + optlen) {       
-                        th->th_sum = in_addword(th->th_sum,
-                            htons((u_short)(optlen + len)));
+               m->m_pkthdr.csum_flags = CSUM_TCP;
+               m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
+               if (len + optlen)
+                       th->th_sum = in_addword(th->th_sum, 
+                               htons((u_short)(optlen + len)));

        }
 
        }
 

+       /*
+        * Enable TSO and specify the size of the segments.
+        * The TCP pseudo header checksum is always provided.
+        */
+       if (tso) {
+#if INET6
+               if (isipv6)
+                       m->m_pkthdr.csum_flags |= CSUM_TSO_IPV6;
+               else
+#endif /* INET6 */
+                       m->m_pkthdr.csum_flags |= CSUM_TSO_IPV4;
+
+               m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen;
+       } else {
+               m->m_pkthdr.tso_segsz = 0;

        }
 
        /*
        }
 
        /*


@@ -744,11 +1801,14 @@ send:
                if (flags & (TH_SYN|TH_FIN)) {
                        if (flags & TH_SYN)
                                tp->snd_nxt++;
                if (flags & (TH_SYN|TH_FIN)) {
                        if (flags & TH_SYN)
                                tp->snd_nxt++;

-                       if (flags & TH_FIN) {
+                       if ((flags & TH_FIN) && 
+                               !(tp->t_flags & TF_SENTFIN)) {

                                tp->snd_nxt++;
                                tp->t_flags |= TF_SENTFIN;
                        }
                }
                                tp->snd_nxt++;
                                tp->t_flags |= TF_SENTFIN;
                        }
                }

+               if (sack_rxmit)
+                       goto timer;

                tp->snd_nxt += len;
                if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
                        tp->snd_max = tp->snd_nxt;
                tp->snd_nxt += len;
                if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
                        tp->snd_max = tp->snd_nxt;


@@ -756,8 +1816,8 @@ send:
                         * Time this transmission if not a retransmission and
                         * not currently timing anything.
                         */
                         * Time this transmission if not a retransmission and
                         * not currently timing anything.
                         */

-                       if (tp->t_rtt == 0) {
-                               tp->t_rtt = 1;
+                       if (tp->t_rtttime == 0) {
+                               tp->t_rtttime = tcp_now;

                                tp->t_rtseq = startseq;
                                tcpstat.tcps_segstimed++;
                        }
                                tp->t_rtseq = startseq;
                                tcpstat.tcps_segstimed++;
                        }


@@ -771,39 +1831,43 @@ send:
                 * Initialize shift counter which is used for backoff
                 * of retransmit time.
                 */
                 * Initialize shift counter which is used for backoff
                 * of retransmit time.
                 */

+timer:

                if (tp->t_timer[TCPT_REXMT] == 0 &&
                if (tp->t_timer[TCPT_REXMT] == 0 &&

-                   tp->snd_nxt != tp->snd_una) {
-                       tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
+                   ((sack_rxmit && tp->snd_nxt != tp->snd_max) ||
+                       tp->snd_nxt != tp->snd_una ||
+                       (flags & TH_FIN))) {

                        if (tp->t_timer[TCPT_PERSIST]) {
                                tp->t_timer[TCPT_PERSIST] = 0;
                                tp->t_rxtshift = 0;
                        if (tp->t_timer[TCPT_PERSIST]) {
                                tp->t_timer[TCPT_PERSIST] = 0;
                                tp->t_rxtshift = 0;

+                               tp->t_rxtstart = 0;
+                               tp->t_persist_stop = 0;

                        }
                        }

+                       tp->t_timer[TCPT_REXMT] = OFFSET_FROM_START(tp, tp->t_rxtcur);

                }
                }

-       } else
-               if (SEQ_GT(tp->snd_nxt + len, tp->snd_max))
+       } else {
+               /*
+                * Persist case, update snd_max but since we are in
+                * persist mode (no window) we do not update snd_nxt.
+                */
+               int xlen = len;
+               if (flags & TH_SYN)
+                       ++xlen;
+               if ((flags & TH_FIN) && 
+                       !(tp->t_flags & TF_SENTFIN)) {
+                       ++xlen;
+                       tp->t_flags |= TF_SENTFIN;
+               }
+               if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max))

                        tp->snd_max = tp->snd_nxt + len;
                        tp->snd_max = tp->snd_nxt + len;

+       }

 
 #if TCPDEBUG
        /*
         * Trace.
         */
 
 #if TCPDEBUG
        /*
         * Trace.
         */

-       if (so->so_options & SO_DEBUG) {
-#if INET6
-               if (isipv6)
-                       ip6->ip6_vfc = IPV6_VERSION;
-               else
-                       ip->ip_vhl = IP_MAKE_VHL(IPVERSION,
-                                                IP_VHL_HL(ip->ip_vhl));
-#endif /* INET6 */
-               tcp_trace(TA_OUTPUT, tp->t_state, tp, 
-#if INET6
-                         isipv6 ? (void *)ip6 :
-#endif /* INET6 */
-                         ip,
-                         th, 0);
-
-       }
-#endif /* TCPDEBUG */
+       if (so_options & SO_DEBUG)
+               tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0);
+#endif

 
        /*
         * Fill in IP length and desired time to live and
 
        /*
         * Fill in IP length and desired time to live and


@@ -812,139 +1876,720 @@ send:
         * the template, but need a way to checksum without them.
         */
 #if INET6
         * the template, but need a way to checksum without them.
         */
 #if INET6

+       /*
+        * m->m_pkthdr.len should have been set before cksum calcuration,
+        * because in6_cksum() need it.
+        */

        if (isipv6) {
        if (isipv6) {

-               /* 
+               /*

                 * we separately set hoplimit for every segment, since the
                 * user might want to change the value via setsockopt.
                 * Also, desired default hop limit might be changed via
                 * Neighbor Discovery.
                 */
                 * we separately set hoplimit for every segment, since the
                 * user might want to change the value via setsockopt.
                 * Also, desired default hop limit might be changed via
                 * Neighbor Discovery.
                 */

-               ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb,
-                                              tp->t_inpcb->in6p_route.ro_rt ?
-                                              tp->t_inpcb->in6p_route.ro_rt->rt_ifp
-                                              : NULL);
+               ip6->ip6_hlim = in6_selecthlim(inp, inp->in6p_route.ro_rt ?
+                   inp->in6p_route.ro_rt->rt_ifp : NULL);

 
                /* TODO: IPv6 IP6TOS_ECT bit on */
 
                /* TODO: IPv6 IP6TOS_ECT bit on */

-#if IPSEC
-               ipsec_setsocket(m, so);
-#endif /*IPSEC*/
-               error = ip6_output(m,
-                           tp->t_inpcb->in6p_outputopts,
-                           &tp->t_inpcb->in6p_route,
-                           (so->so_options & SO_DONTROUTE) /* | IP6_DONTFRAG */,
-                           NULL, NULL);
+               KERNEL_DEBUG(DBG_LAYER_BEG,
+                   ((inp->inp_fport << 16) | inp->inp_lport),
+                   (((inp->in6p_laddr.s6_addr16[0] & 0xffff) << 16) |
+                   (inp->in6p_faddr.s6_addr16[0] & 0xffff)),
+                   sendalot,0,0);

        } else
 #endif /* INET6 */
        {
        } else
 #endif /* INET6 */
        {

-#if 1
-       struct rtentry *rt;
-#endif
-       ip->ip_len = m->m_pkthdr.len;
+               ip->ip_len = m->m_pkthdr.len;
+               ip->ip_ttl = inp->inp_ip_ttl;   /* XXX */
+               ip->ip_tos |= (inp->inp_ip_tos & ~IPTOS_ECN_MASK);/* XXX */
+               KERNEL_DEBUG(DBG_LAYER_BEG,
+                   ((inp->inp_fport << 16) | inp->inp_lport),
+                   (((inp->inp_laddr.s_addr & 0xffff) << 16) |
+                   (inp->inp_faddr.s_addr & 0xffff)), 0,0,0);
+       }
+
+       /*
+        * See if we should do MTU discovery.
+        * Look at the flag updated on the following criterias:
+        *      1) Path MTU discovery is authorized by the sysctl
+        *      2) The route isn't set yet (unlikely but could happen)
+        *      3) The route is up
+        *      4) the MTU is not locked (if it is, then discovery has been
+        *         disabled for that route)
+        */

 #if INET6
 #if INET6

-       if (INP_CHECK_SOCKAF(so, AF_INET6))
-               ip->ip_ttl = in6_selecthlim(tp->t_inpcb,
-                                           tp->t_inpcb->in6p_route.ro_rt ?
-                                           tp->t_inpcb->in6p_route.ro_rt->rt_ifp
-                                           : NULL);
-       else
+       if (!isipv6)

 #endif /* INET6 */
 #endif /* INET6 */

-       ip->ip_ttl = tp->t_inpcb->inp_ip_ttl;   /* XXX */
-       ip->ip_tos = tp->t_inpcb->inp_ip_tos;   /* XXX */
+               if (path_mtu_discovery && (tp->t_flags & TF_PMTUD))
+                       ip->ip_off |= IP_DF;

 
 

-#define thtoti(x) \
-       ((struct tcpiphdr *)(((char *)(x)) - (sizeof (struct ip))))
-
-       KERNEL_DEBUG(DBG_LAYER_END, ((th->th_dport << 16) | th->th_sport),
-                  (((thtoti(th)->ti_src.s_addr & 0xffff) << 16) | (thtoti(th)->ti_dst.s_addr & 0xffff)),
-                   th->th_seq, th->th_ack, th->th_win);
+#if IPSEC
+       if (ipsec_bypass == 0)
+               ipsec_setsocket(m, so);
+#endif /*IPSEC*/

 
 

+       /*
+        * The socket is kept locked while sending out packets in ip_output, even if packet chaining is not active.
+        */
+       lost = 0;

 
 

-#if 1

        /*
        /*

-        * See if we should do MTU discovery.  We do it only if the following
-        * are true:
-        *      1) we have a valid route to the destination
-        *      2) the MTU is not locked (if it is, then discovery has been
-        *         disabled)
+        * Embed the flow hash in pkt hdr and mark the packet as
+        * capable of flow controlling

         */
         */

-       if ((rt = tp->t_inpcb->inp_route.ro_rt)
-           && rt->rt_flags & RTF_UP
-           && !(rt->rt_rmx.rmx_locks & RTV_MTU)) {
-               ip->ip_off |= IP_DF;
+       m->m_pkthdr.pkt_flowsrc = FLOWSRC_INPCB;
+       m->m_pkthdr.pkt_flowid = inp->inp_flowhash;
+       m->m_pkthdr.pkt_flags |= PKTF_FLOW_ID | PKTF_FLOW_LOCALSRC;
+#if MPTCP
+       /* Disable flow advisory when using MPTCP. */
+       if (!(tp->t_mpflags & TMPF_MPTCP_TRUE))
+#endif /* MPTCP */
+               m->m_pkthdr.pkt_flags |= PKTF_FLOW_ADV;
+       m->m_pkthdr.pkt_proto = IPPROTO_TCP;
+
+       m->m_nextpkt = NULL;
+
+       if (inp->inp_last_outifp != NULL &&
+           !(inp->inp_last_outifp->if_flags & IFF_LOOPBACK)) {
+               /* Hint to prioritize this packet if
+                * 1. if the packet has no data
+                * 2. the interface supports transmit-start model and did 
+                *    not disable ACK prioritization.
+                * 3. Only ACK flag is set.
+                * 4. there is no outstanding data on this connection.
+                */
+               if (tcp_prioritize_acks != 0 && len == 0 &&
+                   (inp->inp_last_outifp->if_eflags & 
+                       (IFEF_TXSTART | IFEF_NOACKPRI)) == IFEF_TXSTART &&
+                   th->th_flags == TH_ACK && tp->snd_una == tp->snd_max &&
+                   tp->t_timer[TCPT_REXMT] == 0) {
+                       svc_flags |= PKT_SCF_TCP_ACK;
+               }
+               set_packet_service_class(m, so, MBUF_SC_UNSPEC, svc_flags);

        }
        }

-#endif

 
 

-#if IPSEC
-       ipsec_setsocket(m, so);
-#endif /*IPSEC*/
+       tp->t_pktlist_sentlen += len;
+       tp->t_lastchain++;
+
+#if INET6
+       if (isipv6) {
+               DTRACE_TCP5(send, struct mbuf *, m, struct inpcb *, inp,
+                       struct ip6 *, ip6, struct tcpcb *, tp, struct tcphdr *,
+                       th);
+       } else
+#endif /* INET6 */
+       {
+               DTRACE_TCP5(send, struct mbuf *, m, struct inpcb *, inp,
+                       struct ip *, ip, struct tcpcb *, tp, struct tcphdr *, th);
+       }
+
+       if (tp->t_pktlist_head != NULL) {
+               tp->t_pktlist_tail->m_nextpkt = m;
+               tp->t_pktlist_tail = m;
+       } else {
+               packchain_newlist++;
+               tp->t_pktlist_head = tp->t_pktlist_tail = m;
+       }
+
+       if ((lro_ackmore) && (!sackoptlen) && (!tp->t_timer[TCPT_PERSIST]) &&
+                       ((th->th_flags & TH_ACK) == TH_ACK) && (!len) &&
+                       (tp->t_state == TCPS_ESTABLISHED)) {
+               /* For a pure ACK, see if you need to send more of them */      
+               mnext = tcp_send_lroacks(tp, m, th);
+               if (mnext) {
+                       tp->t_pktlist_tail->m_nextpkt = mnext;
+                       if (mnext->m_nextpkt == NULL) {
+                               tp->t_pktlist_tail = mnext;
+                               tp->t_lastchain++;
+                       } else {
+                               struct mbuf *tail, *next;
+                               next = mnext->m_nextpkt;
+                               tail = next->m_nextpkt;
+                               while (tail) {
+                                       next = tail;
+                                       tail = tail->m_nextpkt;
+                                       tp->t_lastchain++;
+                               }
+                               tp->t_pktlist_tail = next;
+                       }
+               }
+       }
+
+       if (sendalot == 0 || (tp->t_state != TCPS_ESTABLISHED) ||
+             (tp->snd_cwnd <= (tp->snd_wnd / 8)) ||
+             (tp->t_flags & (TH_PUSH | TF_ACKNOW)) || tp->t_force != 0 ||
+             tp->t_lastchain >= tcp_packet_chaining) {
+               error = 0;
+
+               /*
+                * Reset the stack memory of offset as the socket 
+                * may get unlocked
+                */
+               m_lastm = NULL;
+               while (inp->inp_sndinprog_cnt == 0 &&
+                       tp->t_pktlist_head != NULL) {
+                       packetlist = tp->t_pktlist_head;
+                       packchain_listadd = tp->t_lastchain;
+                       packchain_sent++;
+                       lost = tp->t_pktlist_sentlen;
+                       TCP_PKTLIST_CLEAR(tp);
+
+                       error = tcp_ip_output(so, tp, packetlist,
+                           packchain_listadd, tp_inp_options,
+                           (so_options & SO_DONTROUTE),
+                           (sack_rxmit | (sack_bytes_rxmt != 0)), recwin,
+#if INET6
+                           isipv6);
+#else /* INET6 */
+                           0);
+#endif /* !INET6 */
+
+                       if (error) {
+                               /*
+                                * Take into account the rest of unsent
+                                * packets in the packet list for this tcp
+                                * into "lost", since we're about to free
+                                * the whole list below.
+                                */
+                               lost += tp->t_pktlist_sentlen;
+                               break;
+                       } else {
+                               lost = 0;
+                       }
+               }
+               /* tcp was closed while we were in ip; resume close */
+               if (inp->inp_sndinprog_cnt == 0 &&
+                       (tp->t_flags & TF_CLOSING)) {
+                       tp->t_flags &= ~TF_CLOSING;
+                       (void) tcp_close(tp);
+                       return (0);
+               }
+       } else {
+               error = 0;
+               packchain_looped++;
+               tcpstat.tcps_sndtotal++;

 
 

-       error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route,
-           so->so_options & SO_DONTROUTE, 0);
-    }
+               goto again;
+       }

        if (error) {
        if (error) {

+               /*
+                * Assume that the packets were lost, so back out the
+                * sequence number advance, if any.  Note that the "lost"
+                * variable represents the amount of user data sent during
+                * the recent call to ip_output_list() plus the amount of
+                * user data in the packet list for this tcp at the moment.
+                */
+               if (tp->t_force == 0 || tp->t_timer[TCPT_PERSIST] == 0) {
+                       /*
+                        * No need to check for TH_FIN here because
+                        * the TF_SENTFIN flag handles that case.
+                        */
+                       if ((flags & TH_SYN) == 0) {
+                               if (sack_rxmit) {
+                                       if (SEQ_GT((p->rxmit - lost),
+                                           tp->snd_una)) {
+                                               p->rxmit -= lost;
+                                       } else {
+                                               lost = p->rxmit - tp->snd_una;
+                                               p->rxmit = tp->snd_una;
+                                       }
+                                       tp->sackhint.sack_bytes_rexmit -= lost;
+                               } else {
+                                       if (SEQ_GT((tp->snd_nxt - lost),
+                                               tp->snd_una))
+                                               tp->snd_nxt -= lost;
+                                       else
+                                               tp->snd_nxt = tp->snd_una;
+                               }
+                       }
+               }

 out:
 out:

+               if (tp->t_pktlist_head != NULL)
+                       m_freem_list(tp->t_pktlist_head);
+               TCP_PKTLIST_CLEAR(tp);
+

                if (error == ENOBUFS) {
                if (error == ENOBUFS) {

-                        if (!tp->t_timer[TCPT_REXMT] &&
-                             !tp->t_timer[TCPT_PERSIST])
-                                tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
-                       tcp_quench(tp->t_inpcb, 0);
+                       if (!tp->t_timer[TCPT_REXMT] &&
+                               !tp->t_timer[TCPT_PERSIST])
+                               tp->t_timer[TCPT_REXMT] = 
+                                       OFFSET_FROM_START(tp, tp->t_rxtcur);
+
+                       tp->snd_cwnd = tp->t_maxseg;
+                       tp->t_bytes_acked = 0;
+
+                       tcp_check_timer_state(tp);

                        KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END, 0,0,0,0,0);
                        KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END, 0,0,0,0,0);

+
+                       DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp,
+                               struct tcpcb *, tp, struct tcphdr *, NULL,
+                               int32_t, TCP_CC_OUTPUT_ERROR);

                        return (0);
                }
                        return (0);
                }

-#if 1

                if (error == EMSGSIZE) {
                        /*
                         * ip_output() will have already fixed the route
                         * for us.  tcp_mtudisc() will, as its last action,
                         * initiate retransmission, so it is important to
                         * not do so here.
                if (error == EMSGSIZE) {
                        /*
                         * ip_output() will have already fixed the route
                         * for us.  tcp_mtudisc() will, as its last action,
                         * initiate retransmission, so it is important to
                         * not do so here.

+                        *
+                        * If TSO was active we either got an interface
+                        * without TSO capabilits or TSO was turned off.
+                        * Disable it for this connection as too and
+                        * immediatly retry with MSS sized segments generated
+                        * by this function.

                         */
                         */

-                       tcp_mtudisc(tp->t_inpcb, 0);
+                       if (tso)
+                               tp->t_flags &= ~TF_TSO;
+
+                       tcp_mtudisc(inp, 0);
+                       tcp_check_timer_state(tp);
+

                        KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END, 0,0,0,0,0);
                        return 0;
                }
                        KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END, 0,0,0,0,0);
                        return 0;
                }

-#endif
-               if ((error == EHOSTUNREACH || error == ENETDOWN)
-                   && TCPS_HAVERCVDSYN(tp->t_state)) {
+               /*
+                * Unless this is due to interface restriction policy,
+                * treat EHOSTUNREACH/ENETDOWN as a soft error.
+                */
+               if ((error == EHOSTUNREACH || error == ENETDOWN) &&
+                   TCPS_HAVERCVDSYN(tp->t_state) &&
+                   !((inp->inp_flags & INP_NO_IFT_CELLULAR) &&
+                   inp->inp_last_outifp != NULL &&
+                   IFNET_IS_CELLULAR(inp->inp_last_outifp))) {

                        tp->t_softerror = error;
                        tp->t_softerror = error;

-                       KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END, 0,0,0,0,0);
+                       tcp_check_timer_state(tp);
+                       KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END,
+                           0, 0, 0, 0, 0);

                        return (0);
                }
                        return (0);
                }

+               tcp_check_timer_state(tp);

                KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END, 0,0,0,0,0);
                return (error);
        }
                KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END, 0,0,0,0,0);
                return (error);
        }

+

        tcpstat.tcps_sndtotal++;
 
        tcpstat.tcps_sndtotal++;
 

+       KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END,0,0,0,0,0);
+       if (sendalot)
+               goto again;
+
+       tcp_check_timer_state(tp);
+       return (0);
+}
+
+static int
+tcp_ip_output(struct socket *so, struct tcpcb *tp, struct mbuf *pkt,
+    int cnt, struct mbuf *opt, int flags, int sack_in_progress, int recwin,
+    boolean_t isipv6)
+{
+       int error = 0;
+       boolean_t chain;
+       boolean_t unlocked = FALSE;
+       boolean_t ifdenied = FALSE;
+       struct inpcb *inp = tp->t_inpcb;
+       struct ip_out_args ipoa =
+           { IFSCOPE_NONE, { 0 }, IPOAF_SELECT_SRCIF|IPOAF_BOUND_SRCADDR, 0 };
+       struct route ro;
+       struct ifnet *outif = NULL;
+#if INET6
+       struct ip6_out_args ip6oa =
+           { IFSCOPE_NONE, { 0 }, IP6OAF_SELECT_SRCIF|IP6OAF_BOUND_SRCADDR, 0 };
+       struct route_in6 ro6;
+       struct flowadv *adv =
+           (isipv6 ? &ip6oa.ip6oa_flowadv : &ipoa.ipoa_flowadv);
+#else /* INET6 */
+       struct flowadv *adv = &ipoa.ipoa_flowadv;
+#endif /* !INET6 */
+
+       /* If socket was bound to an ifindex, tell ip_output about it */
+       if (inp->inp_flags & INP_BOUND_IF) {
+#if INET6
+               if (isipv6) {
+                       ip6oa.ip6oa_boundif = inp->inp_boundifp->if_index;
+                       ip6oa.ip6oa_flags |= IP6OAF_BOUND_IF;
+               } else
+#endif /* INET6 */
+               {
+                       ipoa.ipoa_boundif = inp->inp_boundifp->if_index;
+                       ipoa.ipoa_flags |= IPOAF_BOUND_IF;
+               }
+       }
+
+       if (inp->inp_flags & INP_NO_IFT_CELLULAR) {
+#if INET6
+               if (isipv6)
+                       ip6oa.ip6oa_flags |=  IP6OAF_NO_CELLULAR;
+               else
+#endif /* INET6 */
+                       ipoa.ipoa_flags |=  IPOAF_NO_CELLULAR;
+       }
+#if INET6
+       if (isipv6)
+               flags |= IPV6_OUTARGS;
+       else
+#endif /* INET6 */
+               flags |= IP_OUTARGS;
+
+       /* Copy the cached route and take an extra reference */
+#if INET6
+       if (isipv6)
+               in6p_route_copyout(inp, &ro6);
+       else
+#endif /* INET6 */
+               inp_route_copyout(inp, &ro);
+

        /*
         * Data sent (as far as we can tell).
         * If this advertises a larger window than any other segment,
         * then remember the size of the advertised window.
        /*
         * Data sent (as far as we can tell).
         * If this advertises a larger window than any other segment,
         * then remember the size of the advertised window.

-        * Any pending ACK has now been sent.
+        * Make sure ACK/DELACK conditions are cleared before
+        * we unlock the socket.

         */
         */

-       if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv))
-               tp->rcv_adv = tp->rcv_nxt + win;
+       if (recwin > 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv))
+               tp->rcv_adv = tp->rcv_nxt + recwin;

        tp->last_ack_sent = tp->rcv_nxt;
        tp->last_ack_sent = tp->rcv_nxt;

-       tp->t_flags &= ~(TF_ACKNOW|TF_DELACK);
-       if (sendalot)
-               goto again;
-       KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END, 0,0,0,0,0);
-       return (0);
+       tp->t_flags &= ~(TF_ACKNOW | TF_DELACK);
+       tp->t_timer[TCPT_DELACK] = 0;
+       tp->t_unacksegs = 0;
+
+       /* Increment the count of outstanding send operations */
+       inp->inp_sndinprog_cnt++;
+
+       /*
+        * If allowed, unlock TCP socket while in IP
+        * but only if the connection is established and
+        * in a normal mode where reentrancy on the tcpcb won't be
+        * an issue:
+        * - there is no SACK episode
+        * - we're not in Fast Recovery mode
+        * - if we're not sending from an upcall.
+        */
+       if (tcp_output_unlocked && !so->so_upcallusecount &&
+           (tp->t_state == TCPS_ESTABLISHED) && (sack_in_progress == 0) &&
+           ((tp->t_flags & TF_FASTRECOVERY) == 0)) {
+
+               unlocked = TRUE;
+               socket_unlock(so, 0);
+       }
+       
+       /*
+        * Don't send down a chain of packets when:
+        * - TCP chaining is disabled
+        * - there is an IPsec rule set
+        * - there is a non default rule set for the firewall
+        */
+
+       chain = tcp_packet_chaining > 1
+#if IPSEC
+               && ipsec_bypass
+#endif
+#if IPFIREWALL
+               && (fw_enable == 0 || fw_bypass)
+#endif
+               ; // I'm important, not extraneous
+
+
+       while (pkt != NULL) {
+               struct mbuf *npkt = pkt->m_nextpkt;
+
+               if (!chain) {
+                       pkt->m_nextpkt = NULL;
+                       /*
+                        * If we are not chaining, make sure to set the packet
+                        * list count to 0 so that IP takes the right path;
+                        * this is important for cases such as IPSec where a
+                        * single mbuf might result in multiple mbufs as part
+                        * of the encapsulation.  If a non-zero count is passed
+                        * down to IP, the head of the chain might change and
+                        * we could end up skipping it (thus generating bogus
+                        * packets).  Fixing it in IP would be desirable, but
+                        * for now this would do it.
+                        */
+                       cnt = 0;
+               }
+#if INET6
+               if (isipv6) {
+                       error = ip6_output_list(pkt, cnt,
+                           inp->in6p_outputopts, &ro6, flags, NULL, NULL,
+                           &ip6oa);
+                       ifdenied = (ip6oa.ip6oa_retflags & IP6OARF_IFDENIED);
+               } else {
+#endif /* INET6 */
+                       error = ip_output_list(pkt, cnt, opt, &ro, flags, NULL,
+                           &ipoa);
+                       ifdenied = (ipoa.ipoa_retflags & IPOARF_IFDENIED);
+               }
+
+               if (chain || error) {
+                       /*
+                        * If we sent down a chain then we are done since
+                        * the callee had taken care of everything; else
+                        * we need to free the rest of the chain ourselves.
+                        */
+                       if (!chain)
+                               m_freem_list(npkt);
+                       break;
+               }
+               pkt = npkt;
+       }
+
+       if (unlocked)
+               socket_lock(so, 0);
+
+       /* 
+        * Enter flow controlled state if the connection is established
+        * and is not in recovery.
+        *
+        * A connection will enter suspended state even if it is in 
+        * recovery.
+        */
+       if (((adv->code == FADV_FLOW_CONTROLLED && !IN_FASTRECOVERY(tp)) ||
+           adv->code == FADV_SUSPENDED) && 
+           !(tp->t_flags & TF_CLOSING) &&
+           tp->t_state == TCPS_ESTABLISHED) {
+               int rc;
+               rc = inp_set_fc_state(inp, adv->code);
+
+               if (rc == 1) 
+                       DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp,
+                           struct tcpcb *, tp, struct tcphdr *, NULL,
+                           int32_t, ((adv->code == FADV_FLOW_CONTROLLED) ?
+                           TCP_CC_FLOW_CONTROL : TCP_CC_SUSPEND));
+       }
+
+       /* 
+        * When an interface queue gets suspended, some of the
+        * packets are dropped. Return ENOBUFS, to update the
+        * pcb state.
+        */
+       if (adv->code == FADV_SUSPENDED)
+               error = ENOBUFS;
+
+       VERIFY(inp->inp_sndinprog_cnt > 0);
+       if ( --inp->inp_sndinprog_cnt == 0)
+               inp->inp_flags &= ~(INP_FC_FEEDBACK);
+
+#if INET6
+       if (isipv6) {
+               if (ro6.ro_rt != NULL && (outif = ro6.ro_rt->rt_ifp) !=
+                   inp->in6p_last_outifp)
+                       inp->in6p_last_outifp = outif;
+       } else
+#endif /* INET6 */
+               if (ro.ro_rt != NULL && (outif = ro.ro_rt->rt_ifp) !=
+                   inp->inp_last_outifp)
+                       inp->inp_last_outifp = outif;
+
+       if (error != 0 && ifdenied && (inp->inp_flags & INP_NO_IFT_CELLULAR))
+               soevent(inp->inp_socket,
+                   (SO_FILT_HINT_LOCKED|SO_FILT_HINT_IFDENIED));
+
+       /* Synchronize cached PCB route & options */
+#if INET6
+       if (isipv6)
+               in6p_route_copyin(inp, &ro6);
+       else
+#endif /* INET6 */
+               inp_route_copyin(inp, &ro);
+
+       if (tp->t_state < TCPS_ESTABLISHED && tp->t_rxtshift == 0 && 
+               tp->t_inpcb->inp_route.ro_rt != NULL) {
+               /* If we found the route and there is an rtt on it
+                * reset the retransmit timer
+                */
+               tcp_getrt_rtt(tp, tp->t_inpcb->in6p_route.ro_rt);
+               tp->t_timer[TCPT_REXMT] = OFFSET_FROM_START(tp, tp->t_rxtcur);
+       }
+       return (error);

 }
 
 void
 tcp_setpersist(tp)
        register struct tcpcb *tp;
 {
 }
 
 void
 tcp_setpersist(tp)
        register struct tcpcb *tp;
 {

-       register int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
+       int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
+
+       /* If a PERSIST_TIMER option was set we will limit the
+        * time the persist timer will be active for that connection
+        * in order to avoid DOS by using zero window probes.
+        * see rdar://5805356
+        */
+
+       if ((tp->t_persist_timeout != 0) &&
+                   (tp->t_timer[TCPT_PERSIST] == 0) &&
+                   (tp->t_persist_stop == 0)) {
+               tp->t_persist_stop = tcp_now + tp->t_persist_timeout;
+       }

 
 

-       if (tp->t_timer[TCPT_REXMT])
-               panic("tcp_output REXMT");

        /*
         * Start/restart persistance timer.
         */
        TCPT_RANGESET(tp->t_timer[TCPT_PERSIST],
            t * tcp_backoff[tp->t_rxtshift],
        /*
         * Start/restart persistance timer.
         */
        TCPT_RANGESET(tp->t_timer[TCPT_PERSIST],
            t * tcp_backoff[tp->t_rxtshift],

-           TCPTV_PERSMIN, TCPTV_PERSMAX);
+           TCPTV_PERSMIN, TCPTV_PERSMAX, 0);
+       tp->t_timer[TCPT_PERSIST] = OFFSET_FROM_START(tp, tp->t_timer[TCPT_PERSIST]);
+

        if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
                tp->t_rxtshift++;
 }
        if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
                tp->t_rxtshift++;
 }

+
+/*
+ * Send as many acks as data coalesced. Every other packet when stretch
+ * ACK is not enabled. Every 8 packets, if stretch ACK is enabled.
+ */
+static struct mbuf*
+tcp_send_lroacks(struct tcpcb *tp, struct mbuf *m, struct tcphdr *th)
+{
+       struct mbuf *mnext = NULL, *ack_chain = NULL, *tail = NULL;
+       int count = 0;
+       tcp_seq org_ack = ntohl(th->th_ack);
+       tcp_seq prev_ack = 0;
+       int tack_offset = 28; /* XXX IPv6 and IP options not supported */
+       int twin_offset = 34; /* XXX IPv6 and IP options not supported */
+       int ack_size = (tp->t_flags & TF_STRETCHACK) ?
+                       (maxseg_unacked * tp->t_maxseg) : (tp->t_maxseg << 1);
+       int segs_acked = (tp->t_flags & TF_STRETCHACK) ? maxseg_unacked : 2;
+       struct mbuf *prev_ack_pkt = NULL;
+       struct socket *so = tp->t_inpcb->inp_socket;
+       unsigned short winsz = ntohs(th->th_win);
+       unsigned int scaled_win = winsz<<tp->rcv_scale;
+       tcp_seq win_rtedge = org_ack + scaled_win;
+
+       count = tp->t_lropktlen/tp->t_maxseg;
+
+       prev_ack = (org_ack - tp->t_lropktlen) + ack_size;
+       if (prev_ack < org_ack) {
+               ack_chain = m_dup(m, M_DONTWAIT);
+               if (ack_chain) {
+                       th->th_ack = htonl(prev_ack);
+                       /* Keep adv window constant for duplicated ACK packets */
+                       scaled_win = win_rtedge - prev_ack;
+                       if (scaled_win > (int32_t)(TCP_MAXWIN << tp->rcv_scale))
+                               scaled_win = (int32_t)(TCP_MAXWIN << tp->rcv_scale);
+                       th->th_win = htons(scaled_win>>tp->rcv_scale);
+                       if (lrodebug == 5) {
+                               printf("%s: win = %d winsz = %d sc = %d"
+                                   " lro_len %d %d\n",
+                                   __func__, scaled_win>>tp->rcv_scale, winsz,
+                                   tp->rcv_scale, tp->t_lropktlen, count);
+                       }
+                       tail = ack_chain;
+                       count -= segs_acked; /* accounts for prev_ack packet */
+                       count = (count <= segs_acked) ? 0 : count - segs_acked;
+                       tcpstat.tcps_sndacks++;
+                       so_tc_update_stats(m, so, m_get_service_class(m));
+               } else {
+                       return NULL;
+               }
+       }
+       else {
+               tp->t_lropktlen = 0;
+               return NULL;
+       }
+
+       prev_ack_pkt = ack_chain;
+
+       while (count > 0) {
+               if ((prev_ack + ack_size) < org_ack) {
+                       prev_ack += ack_size;
+               } else {
+                       /*
+                        * The last ACK sent must have the ACK number that TCP
+                        * thinks is the last sent ACK number.
+                        */
+                        prev_ack = org_ack;
+               }
+               mnext = m_dup(prev_ack_pkt, M_DONTWAIT);
+               if (mnext) {
+                       /* Keep adv window constant for duplicated ACK packets */
+                       scaled_win = win_rtedge - prev_ack;
+                       if (scaled_win > (int32_t)(TCP_MAXWIN << tp->rcv_scale))
+                               scaled_win = (int32_t)(TCP_MAXWIN << tp->rcv_scale);
+                       winsz = htons(scaled_win>>tp->rcv_scale);
+                       if (lrodebug == 5) {
+                               printf("%s: winsz = %d ack %x count %d\n",
+                                   __func__, scaled_win>>tp->rcv_scale,
+                                   prev_ack, count);
+                       }
+                       bcopy(&winsz, mtod(prev_ack_pkt, caddr_t) + twin_offset, 2);
+                       HTONL(prev_ack);
+                       bcopy(&prev_ack, mtod(prev_ack_pkt, caddr_t) + tack_offset, 4);
+                       NTOHL(prev_ack);
+                       tail->m_nextpkt = mnext;
+                       tail = mnext;
+                       count -= segs_acked;
+                       tcpstat.tcps_sndacks++;
+                       so_tc_update_stats(m, so, m_get_service_class(m));
+               } else {
+                       if (lrodebug == 5) {
+                               printf("%s: failed to alloc mbuf.\n", __func__);
+                       }
+                       break;
+               }
+               prev_ack_pkt = mnext;
+       }
+       tp->t_lropktlen = 0;
+       return ack_chain;
+}
+
+static int
+tcp_recv_throttle (struct tcpcb *tp)
+{
+       uint32_t base_rtt, newsize;
+       int32_t qdelay;
+       struct sockbuf *sbrcv = &tp->t_inpcb->inp_socket->so_rcv;
+
+       if (tcp_use_rtt_recvbg == 1 &&
+           TSTMP_SUPPORTED(tp)) {
+               /* 
+                * Timestamps are supported on this connection. Use
+                * RTT to look for an increase in latency.
+                */
+
+               /* 
+                * If the connection is already being throttled, leave it
+                * in that state until rtt comes closer to base rtt
+                */
+               if (tp->t_flagsext & TF_RECV_THROTTLE)
+                       return (1);
+
+               base_rtt = get_base_rtt(tp);
+               
+               if (base_rtt != 0 && tp->t_rttcur != 0) {
+                       qdelay = tp->t_rttcur - base_rtt;
+                       /*
+                        * if latency increased on a background flow,
+                        * return 1 to start throttling.
+                        */
+                       if (qdelay > target_qdelay) {
+                               tp->t_flagsext |= TF_RECV_THROTTLE;
+
+                               /*
+                                * Reduce the recv socket buffer size to
+                                * minimize latecy.
+                                */
+                               if (sbrcv->sb_idealsize > 
+                                   tcp_recv_throttle_minwin) {
+                                       newsize = sbrcv->sb_idealsize >> 1;
+                                       /* Set a minimum of 16 K */
+                                       newsize = 
+                                           max(newsize, 
+                                           tcp_recv_throttle_minwin);
+                                       sbrcv->sb_idealsize = newsize;
+                               }
+                               return (1);
+                       } else {
+                               return (0);
+                       }
+               }
+       }
+
+       /*
+        * Timestamps are not supported or there is no good RTT
+        * measurement. Use IPDV in this case.
+        */
+       if (tp->acc_iaj > tcp_acc_iaj_react_limit)
+               return (1);
+       
+       return (0);
+}