]> git.saurik.com Git - apple/xnu.git/blobdiff - bsd/netinet/tcp_output.c
xnu-4903.221.2.tar.gz
[apple/xnu.git] / bsd / netinet / tcp_output.c
index 4dfd0bc8f68bd40ca3806f4c4b5d8e9dcbd1e20e..75e8634c0bf63d96395584e7f4e4022f0840fe08 100644 (file)
@@ -1,8 +1,8 @@
 /*
- * Copyright (c) 2000-2015 Apple Inc. All rights reserved.
+ * Copyright (c) 2000-2018 Apple Inc. All rights reserved.
  *
  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
- * 
+ *
  * 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
  * 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.
- * 
+ *
  * 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,
@@ -22,7 +22,7 @@
  * 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_OSREFERENCE_LICENSE_HEADER_END@
  */
 /*
@@ -90,6 +90,7 @@
 #include <netinet/in.h>
 #include <netinet/in_systm.h>
 #include <netinet/in_var.h>
+#include <netinet/in_tclass.h>
 #include <netinet/ip.h>
 #include <netinet/in_pcb.h>
 #include <netinet/ip_var.h>
 #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,
+SYSCTL_SKMEM_TCP_INT(OID_AUTO, path_mtu_discovery,
+       CTLFLAG_RW | CTLFLAG_LOCKED, int, 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,
+SYSCTL_SKMEM_TCP_INT(OID_AUTO, slowstart_flightsize,
+       CTLFLAG_RW | CTLFLAG_LOCKED, int, 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,
+SYSCTL_SKMEM_TCP_INT(OID_AUTO, local_slowstart_flightsize,
+       CTLFLAG_RW | CTLFLAG_LOCKED, int, ss_fltsz_local, 8,
        "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");
+                  &tcp_do_tso, 0, "Enable TCP Segmentation Offload");
+
+SYSCTL_SKMEM_TCP_INT(OID_AUTO, ecn_setup_percentage,
+    CTLFLAG_RW | CTLFLAG_LOCKED, int, tcp_ecn_setup_percentage, 100,
+    "Max ECN setup percentage");
 
 static int
 sysctl_change_ecn_setting SYSCTL_HANDLER_ARGS
@@ -170,6 +172,7 @@ sysctl_change_ecn_setting SYSCTL_HANDLER_ARGS
                if ((tcp_ecn_outbound == 0 || tcp_ecn_outbound == 1) &&
                    (i == 0 || i == 1)) {
                        tcp_ecn_outbound = i;
+                       SYSCTL_SKMEM_UPDATE_FIELD(tcp.ecn_initiate_out, tcp_ecn_outbound);
                        return(err);
                }
                if (tcp_ecn_outbound == 2 && (i == 0 || i == 1)) {
@@ -205,10 +208,13 @@ sysctl_change_ecn_setting SYSCTL_HANDLER_ARGS
                        ifnet_head_done();
                }
                tcp_ecn_outbound = i;
+               SYSCTL_SKMEM_UPDATE_FIELD(tcp.ecn_initiate_out, tcp_ecn_outbound);
        }
        /* Change the other one too as the work is done */
-       if (i == 2 || tcp_ecn_inbound == 2)
+       if (i == 2 || tcp_ecn_inbound == 2) {
                tcp_ecn_inbound = i;
+               SYSCTL_SKMEM_UPDATE_FIELD(tcp.ecn_negotiate_in, tcp_ecn_inbound);
+       }
        return (err);
 }
 
@@ -224,65 +230,53 @@ SYSCTL_PROC(_net_inet_tcp, OID_AUTO, ecn_negotiate_in,
     sysctl_change_ecn_setting, "IU",
     "Initiate ECN for inbound connections");
 
-int    tcp_packet_chaining = 50;
-SYSCTL_INT(_net_inet_tcp, OID_AUTO, packetchain,
-       CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_packet_chaining, 0,
+SYSCTL_SKMEM_TCP_INT(OID_AUTO, packetchain,
+       CTLFLAG_RW | CTLFLAG_LOCKED, int, tcp_packet_chaining, 50,
        "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,
+SYSCTL_SKMEM_TCP_INT(OID_AUTO, socket_unlocked_on_output,
+       CTLFLAG_RW | CTLFLAG_LOCKED, int, tcp_output_unlocked, 1,
        "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,
+SYSCTL_SKMEM_TCP_INT(OID_AUTO, rfc3390,
+       CTLFLAG_RW | CTLFLAG_LOCKED, int, 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,
+SYSCTL_SKMEM_TCP_INT(OID_AUTO, min_iaj_win,
+       CTLFLAG_RW | CTLFLAG_LOCKED, int, tcp_min_iaj_win, MIN_IAJ_WIN,
        "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");
+SYSCTL_SKMEM_TCP_INT(OID_AUTO, acc_iaj_react_limit,
+       CTLFLAG_RW | CTLFLAG_LOCKED, int, tcp_acc_iaj_react_limit,
+       ACC_IAJ_REACT_LIMIT, "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,
+SYSCTL_SKMEM_TCP_INT(OID_AUTO, doautosndbuf,
+       CTLFLAG_RW | CTLFLAG_LOCKED, uint32_t, 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");
+SYSCTL_SKMEM_TCP_INT(OID_AUTO, autosndbufinc,
+       CTLFLAG_RW | CTLFLAG_LOCKED, uint32_t, tcp_autosndbuf_inc,
+       8 * 1024, "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,
+SYSCTL_SKMEM_TCP_INT(OID_AUTO, autosndbufmax,
+       CTLFLAG_RW | CTLFLAG_LOCKED, uint32_t, tcp_autosndbuf_max, 512 * 1024,
        "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,
+SYSCTL_SKMEM_TCP_INT(OID_AUTO, ack_prioritize,
+       CTLFLAG_RW | CTLFLAG_LOCKED, uint32_t, 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,
+SYSCTL_SKMEM_TCP_INT(OID_AUTO, rtt_recvbg,
+       CTLFLAG_RW | CTLFLAG_LOCKED, uint32_t, 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,
+SYSCTL_SKMEM_TCP_INT(OID_AUTO, recv_throttle_minwin,
+       CTLFLAG_RW | CTLFLAG_LOCKED, uint32_t, tcp_recv_throttle_minwin, 16 * 1024,
        "Minimum recv win for throttling");
 
-int32_t tcp_enable_tlp = 1;
-SYSCTL_INT(_net_inet_tcp, OID_AUTO, enable_tlp,
+SYSCTL_SKMEM_TCP_INT(OID_AUTO, enable_tlp,
        CTLFLAG_RW | CTLFLAG_LOCKED,
-       &tcp_enable_tlp, 1, "Enable Tail loss probe");
+       int32_t, tcp_enable_tlp, 1, "Enable Tail loss probe");
 
 static int32_t packchain_newlist = 0;
 static int32_t packchain_looped = 0;
@@ -295,16 +289,15 @@ extern int ipsec_bypass;
 
 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 */
+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;
 
-static int tcp_ip_output(struct socket *, struct tcpcb *, struct mbuf *, int,
-    struct mbuf *, int, int, int32_t, boolean_t);
+static int tcp_ip_output(struct socket *, struct tcpcb *, struct mbuf *,
+    int, struct mbuf *, int, int, boolean_t);
 static struct mbuf* tcp_send_lroacks(struct tcpcb *tp, struct mbuf *m, struct tcphdr *th);
 static int tcp_recv_throttle(struct tcpcb *tp);
 
@@ -317,8 +310,18 @@ static int32_t tcp_tfo_check(struct tcpcb *tp, int32_t len)
        if (tp->t_flags & TF_NOOPT)
                goto fallback;
 
-       if (!tcp_heuristic_do_tfo(tp))
+       if ((so->so_flags1 & SOF1_DATA_AUTHENTICATED) &&
+           !(tp->t_flagsext & TF_FASTOPEN_HEUR))
+               return (len);
+
+       if (!tcp_heuristic_do_tfo(tp)) {
+               tp->t_tfo_stats |= TFO_S_HEURISTICS_DISABLE;
+               tcpstat.tcps_tfo_heuristics_disable++;
                goto fallback;
+       }
+
+       if (so->so_flags1 & SOF1_DATA_AUTHENTICATED)
+               return (len);
 
        optlen += TCPOLEN_MAXSEG;
 
@@ -348,6 +351,10 @@ static int32_t tcp_tfo_check(struct tcpcb *tp, int32_t len)
                /* No cookie, so we request one */
                return (0);
 
+       /* There is not enough space for the cookie, so we cannot do TFO */
+       if (MAX_TCPOPTLEN - optlen < cookie_len)
+               goto fallback;
+
        /* Do not send SYN+data if there is more in the queue than MSS */
        if (so->so_snd.sb_cc > (tp->t_maxopd - MAX_TCPOPTLEN))
                goto fallback;
@@ -388,14 +395,25 @@ tcp_tfo_write_cookie_rep(struct tcpcb *tp, unsigned optlen, u_char *opt)
 }
 
 static unsigned
-tcp_tfo_write_cookie(struct tcpcb *tp, unsigned optlen, int32_t *len,
+tcp_tfo_write_cookie(struct tcpcb *tp, unsigned optlen, int32_t len,
                     u_char *opt)
 {
        u_int8_t tfo_len = MAX_TCPOPTLEN - optlen - TCPOLEN_FASTOPEN_REQ;
+       struct socket *so = tp->t_inpcb->inp_socket;
        unsigned ret = 0;
        int res;
        u_char *bp;
 
+       if (so->so_flags1 & SOF1_DATA_AUTHENTICATED) {
+               /* If there is some data, let's track it */
+               if (len > 0) {
+                       tp->t_tfo_stats |= TFO_S_SYN_DATA_SENT;
+                       tcpstat.tcps_tfo_syn_data_sent++;
+               }
+
+               return (0);
+       }
+
        bp = opt + optlen;
 
        /*
@@ -422,7 +440,7 @@ tcp_tfo_write_cookie(struct tcpcb *tp, unsigned optlen, int32_t *len,
                tp->t_tfo_flags |= TFO_F_COOKIE_SENT;
 
                /* If there is some data, let's track it */
-               if (*len) {
+               if (len > 0) {
                        tp->t_tfo_stats |= TFO_S_SYN_DATA_SENT;
                        tcpstat.tcps_tfo_syn_data_sent++;
                }
@@ -439,7 +457,6 @@ tcp_send_ecn_flags_on_syn(struct tcpcb *tp, struct socket *so)
            (tp->t_flagsext & TF_FASTOPEN)));
 }
 
-#define        TCP_ECN_SETUP_PERCENTAGE_MAX    5
 void
 tcp_set_ecn(struct tcpcb *tp, struct ifnet *ifp)
 {
@@ -500,7 +517,7 @@ check_heuristic:
                 * Use the random value in iss for randomizing
                 * this selection
                 */
-               if ((tp->iss % 100) >= TCP_ECN_SETUP_PERCENTAGE_MAX)
+               if ((tp->iss % 100) >= tcp_ecn_setup_percentage)
                        tp->ecn_flags &= ~TE_ENABLE_ECN;
        }
 }
@@ -561,26 +578,24 @@ tcp_output(struct tcpcb *tp)
        struct mbuf *tp_inp_options = inp->inp_depend4.inp4_options;
 #if INET6
        int isipv6 = inp->inp_vflag & INP_IPV6 ;
+#else
+       int isipv6 = 0;
 #endif
        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 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;
-       boolean_t mptcp_acknow = FALSE;
-       boolean_t early_data_sent = FALSE;
+       boolean_t mptcp_acknow;
 #endif /* MPTCP */
        boolean_t cell = FALSE;
        boolean_t wifi = FALSE;
        boolean_t wired = FALSE;
        boolean_t sack_rescue_rxt = FALSE;
+       int sotc = so->so_traffic_class;
 
        /*
         * Determine length of data that should be transmitted,
@@ -619,11 +634,11 @@ tcp_output(struct tcpcb *tp)
                        idle = 0;
                }
        }
-#if MPTCP 
+#if MPTCP
        if (tp->t_mpflags & TMPF_RESET) {
                tcp_check_timer_state(tp);
-               /* 
-                * Once a RST has been sent for an MPTCP subflow, 
+               /*
+                * 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.
                 */
@@ -632,6 +647,10 @@ tcp_output(struct tcpcb *tp)
 #endif /* MPTCP */
 
 again:
+#if MPTCP
+       mptcp_acknow = FALSE;
+#endif
+
        KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_START, 0,0,0,0,0);
 
 #if INET6
@@ -702,9 +721,8 @@ again:
                                    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;
+                                       TCP_RESET_REXMT_STATE(tp);
                                }
                        }
 
@@ -713,7 +731,7 @@ again:
                        TCP_PKTLIST_CLEAR(tp);
 
                        /* drop connection if source address isn't available */
-                       if (so->so_flags & SOF_NOADDRAVAIL) { 
+                       if (so->so_flags & SOF_NOADDRAVAIL) {
                                tcp_drop(tp, EADDRNOTAVAIL);
                                return(EADDRNOTAVAIL);
                        } else {
@@ -748,9 +766,9 @@ again:
                 *         has been disabled)
                 */
 
-               if (!path_mtu_discovery || ((rt != NULL) && 
+               if (!path_mtu_discovery || ((rt != NULL) &&
                    (!(rt->rt_flags & RTF_UP) ||
-                   (rt->rt_rmx.rmx_locks & RTV_MTU)))) 
+                   (rt->rt_rmx.rmx_locks & RTV_MTU))))
                        tp->t_flags &= ~TF_PMTUD;
                else
                        tp->t_flags |= TF_PMTUD;
@@ -797,7 +815,7 @@ again:
        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;
@@ -825,7 +843,7 @@ again:
                        len = ((int32_t)min(cwin, p->end - p->rxmit));
                }
                if (len > 0) {
-                       off = p->rxmit - tp->snd_una; 
+                       off = p->rxmit - tp->snd_una;
                        sack_rxmit = 1;
                        sendalot = 1;
                        tcpstat.tcps_sack_rexmits++;
@@ -874,9 +892,8 @@ after_sack_rexmit:
                        sendwin = 1;
                } else {
                        tp->t_timer[TCPT_PERSIST] = 0;
-                       tp->t_rxtshift = 0;
-                       tp->t_rxtstart = 0;
                        tp->t_persist_stop = 0;
+                       TCP_RESET_REXMT_STATE(tp);
                }
        }
 
@@ -911,12 +928,12 @@ after_sack_rexmit:
                         * sending new data, having retransmitted all the
                         * data possible in the scoreboard.
                         */
-                       len = min(so->so_snd.sb_cc, tp->snd_wnd) 
+                       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 
+                        * 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.
@@ -956,22 +973,6 @@ after_sack_rexmit:
                }
        }
 
-#if MPTCP
-       if ((tp->t_mpflags & TMPF_FASTJOIN_SEND) &&
-           (tp->t_state == TCPS_SYN_SENT) &&
-           (!(tp->t_flags & TF_CLOSING)) &&
-           (so->so_snd.sb_cc != 0) &&
-           (tp->t_rxtshift == 0)) {
-               flags &= ~TH_SYN;
-               flags |= TH_ACK;
-               off = 0;
-               len = min(so->so_snd.sb_cc, tp->t_maxseg);
-               early_data_sent = TRUE;
-       } else if (early_data_sent) {
-               /* for now, we allow only one data segment to be sent */
-               return (0);
-       }
-#endif /* MPTCP */
        /*
         * Lop off SYN bit if it has already been sent.  However, if this
         * is SYN-SENT state and if segment contains data and if we don't
@@ -980,7 +981,8 @@ after_sack_rexmit:
        if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
                if (tp->t_state != TCPS_SYN_RECEIVED || tfo_enabled(tp))
                        flags &= ~TH_SYN;
-               off--, len++;
+               off--;
+               len++;
                if (len > 0 && tp->t_state == TCPS_SYN_SENT) {
                        while (inp->inp_sndinprog_cnt == 0 &&
                                tp->t_pktlist_head != NULL) {
@@ -992,19 +994,13 @@ after_sack_rexmit:
                                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
+                                   (sack_rxmit || (sack_bytes_rxmt != 0)),
                                    isipv6);
-#else /* INET6 */
-                                   0);
-#endif /* !INET6 */
-
-
                        }
 
                        /*
                         * tcp was closed while we were in ip,
-                        * resume close 
+                        * resume close
                         */
                        if (inp->inp_sndinprog_cnt == 0 &&
                                (tp->t_flags & TF_CLOSING)) {
@@ -1039,9 +1035,9 @@ after_sack_rexmit:
        /*
         * 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 
+        * 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,
@@ -1057,8 +1053,7 @@ after_sack_rexmit:
                if (sendwin == 0) {
                        tp->t_timer[TCPT_REXMT] = 0;
                        tp->t_timer[TCPT_PTO] = 0;
-                       tp->t_rxtshift = 0;
-                       tp->t_rxtstart = 0;
+                       TCP_RESET_REXMT_STATE(tp);
                        tp->snd_nxt = tp->snd_una;
                        off = 0;
                        if (tp->t_timer[TCPT_PERSIST] == 0)
@@ -1075,34 +1070,17 @@ after_sack_rexmit:
         *      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;
+                   sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) {
+                       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;
                        }
                }
        }
@@ -1164,30 +1142,36 @@ after_sack_rexmit:
        }
 
 #if MPTCP
-       if ((so->so_flags & SOF_MP_SUBFLOW) && 
+       if ((so->so_flags & SOF_MP_SUBFLOW) &&
            !(tp->t_mpflags & TMPF_TCP_FALLBACK)) {
                int newlen = len;
-               if ((tp->t_state >= TCPS_ESTABLISHED) &&
-                   ((tp->t_mpflags & TMPF_SND_MPPRIO) ||
-                   (tp->t_mpflags & TMPF_SND_REM_ADDR) ||
-                   (tp->t_mpflags & TMPF_SND_MPFAIL) ||
-                   (tp->t_mpflags & TMPF_MPCAP_RETRANSMIT))) {
+               if (tp->t_state >= TCPS_ESTABLISHED &&
+                   (tp->t_mpflags & TMPF_SND_MPPRIO ||
+                    tp->t_mpflags & TMPF_SND_REM_ADDR ||
+                    tp->t_mpflags & TMPF_SND_MPFAIL ||
+                    tp->t_mpflags & TMPF_SND_KEYS ||
+                    tp->t_mpflags & TMPF_SND_JACK)) {
                        if (len > 0) {
                                len = 0;
                        }
-                       sendalot = 1;
+                       /*
+                        * On a new subflow, don't try to send again, because
+                        * we are still waiting for the fourth ack.
+                        */
+                       if (!(tp->t_mpflags & TMPF_PREESTABLISHED))
+                               sendalot = 1;
                        mptcp_acknow = TRUE;
                } else {
                        mptcp_acknow = FALSE;
                }
                /*
                 * The contiguous bytes in the subflow socket buffer can be
-                * discontiguous at the MPTCP level. Since only one DSS 
+                * 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);
+                       newlen = mptcp_adj_sendlen(so, off);
                if (newlen < len) {
                        len = newlen;
                        sendalot = 1;
@@ -1200,8 +1184,8 @@ after_sack_rexmit:
         * 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. 
+        * 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) >
@@ -1209,7 +1193,7 @@ after_sack_rexmit:
                        sbpull_unordered_data(so, off, len);
 
                        /* check if len needs to be modified */
-                       if ((off + len) > 
+                       if ((off + len) >
                            so->so_msg_state->msg_serial_bytes) {
                                len = so->so_msg_state->msg_serial_bytes - off;
                                if (len <= 0) {
@@ -1227,8 +1211,57 @@ after_sack_rexmit:
                if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc))
                        flags &= ~TH_FIN;
        }
-
+       /*
+        * 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 25% of the maximum possible
+        * window, then want to send a window update to peer.
+        * Skip this if the connection is in T/TCP half-open state.
+        */
        recwin = tcp_sbspace(tp);
+#if MPTCP
+       if (so->so_flags & SOF_MP_SUBFLOW) {
+               struct mptcb *mp_tp = tptomptp(tp);
+
+               if (mp_tp != NULL) {
+                       mpte_lock_assert_held(mp_tp->mpt_mpte);
+                       recwin = imin(recwin, mptcp_sbspace(mp_tp));
+               }
+       }
+#endif
+
+       if (recwin < (int32_t)(so->so_rcv.sb_hiwat / 4) &&
+           recwin < (int)tp->t_maxseg)
+               recwin = 0;
+
+#if TRAFFIC_MGT
+       if (tcp_recv_bg == 1 || IS_TCP_RECV_BG(so)) {
+               if (recwin > 0 && tcp_recv_throttle(tp)) {
+                       uint32_t min_iaj_win = tcp_min_iaj_win * tp->t_maxseg;
+                       uint32_t bg_rwintop = tp->rcv_adv;
+                       if (SEQ_LT(bg_rwintop, tp->rcv_nxt + min_iaj_win))
+                               bg_rwintop =  tp->rcv_nxt + min_iaj_win;
+                       recwin = imin((int32_t)(bg_rwintop - tp->rcv_nxt),
+                           recwin);
+                       if (recwin < 0)
+                               recwin = 0;
+               }
+       }
+#endif /* TRAFFIC_MGT */
+
+       if (recwin > (int32_t)(TCP_MAXWIN << tp->rcv_scale))
+               recwin = (int32_t)(TCP_MAXWIN << tp->rcv_scale);
+
+       /*
+        * MPTCP needs to be able to announce a smaller window than previously,
+        * because the other subflow may have filled up the available window-
+        * space. So we have to be able to go backwards and announce a smaller
+        * window.
+        */
+       if (!(so->so_flags & SOF_MP_SUBFLOW) &&
+           recwin < (int32_t)(tp->rcv_adv - tp->rcv_nxt))
+               recwin = (int32_t)(tp->rcv_adv - tp->rcv_nxt);
 
        /*
         * Sender silly window avoidance.   We transmit under the following
@@ -1258,12 +1291,20 @@ after_sack_rexmit:
                    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 ||
+                           (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)
+                           (len + off >= so->so_snd.sb_cc ||
+                            /*
+                             * MPTCP needs to respect the DSS-mappings. So, it
+                             * may be sending data that *could* have been
+                             * coalesced, but cannot because of
+                             * mptcp_adj_sendlen().
+                             */
+                            so->so_flags & SOF_MP_SUBFLOW))
                                goto send;
                        if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
                                goto send;
@@ -1272,14 +1313,6 @@ after_sack_rexmit:
                }
        }
 
-       /*
-        * 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 25% of the maximum possible
-        * window, then want to send a window update to peer.
-        * Skip this if the connection is in T/TCP half-open state.
-        */
        if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN)) {
                /*
                 * "adv" is the amount we can increase the window,
@@ -1297,34 +1330,35 @@ after_sack_rexmit:
                        /*
                         * 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 
+                        * 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 
+                        * 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 || 
+                               (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;
+               if (4 * adv >= (int32_t) so->so_rcv.sb_hiwat)
+                       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);
+               }
        }
 
        /*
@@ -1354,14 +1388,14 @@ after_sack_rexmit:
         * 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) && 
+       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
@@ -1386,8 +1420,7 @@ after_sack_rexmit:
         */
        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_RESET_REXMT_STATE(tp);
                tcp_setpersist(tp);
        }
 just_return:
@@ -1405,12 +1438,7 @@ just_return:
                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 */
+                   (sack_rxmit || (sack_bytes_rxmt != 0)), isipv6);
        }
        /* tcp was closed while we were in ip; resume close */
        if (inp->inp_sndinprog_cnt == 0 &&
@@ -1471,9 +1499,8 @@ send:
                                optlen += 4;
                        }
 #if MPTCP
-                       if (mptcp_enable) {
-                               optlen = mptcp_setup_syn_opts(so, flags, opt,
-                                   optlen);
+                       if (mptcp_enable && (so->so_flags & SOF_MP_SUBFLOW)) {
+                               optlen = mptcp_setup_syn_opts(so, opt, optlen);
                        }
 #endif /* MPTCP */
                }
@@ -1502,7 +1529,7 @@ send:
                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
@@ -1541,14 +1568,14 @@ send:
                        tp->t_mpflags |= TMPF_MPTCP_ACKNOW;
                }
                optlen = mptcp_setup_opts(tp, off, &opt[0], optlen, flags,
-                   len, &dlenp, &finp, &dss_val, &sseqp, &mptcp_acknow);
+                   len, &mptcp_acknow);
                tp->t_mpflags &= ~TMPF_SEND_DSN;
        }
 #endif /* MPTCP */
 
        if (tfo_enabled(tp) && !(tp->t_flags & TF_NOOPT) &&
            (flags & (TH_SYN | TH_ACK)) == TH_SYN)
-               optlen += tcp_tfo_write_cookie(tp, optlen, &len, opt);
+               optlen += tcp_tfo_write_cookie(tp, optlen, len, opt);
 
        if (tfo_enabled(tp) &&
            (flags & (TH_SYN | TH_ACK)) == (TH_SYN | TH_ACK) &&
@@ -1804,43 +1831,30 @@ send:
                        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");
 
        /* Check if there is enough data in the send socket
-        * buffer to start measuring b
+        * buffer to start measuring bandwidth
         */
        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;
+               (tp->t_flagsext & TF_BWMEAS_INPROGRESS) == 0) {
+               tp->t_bwmeas->bw_size = min(min(
+                   (so->so_snd.sb_cc - (tp->snd_max - tp->snd_una)),
+                   tp->snd_cwnd), tp->snd_wnd);
+               if (tp->t_bwmeas->bw_minsize > 0 &&
+                   tp->t_bwmeas->bw_size < tp->t_bwmeas->bw_minsize)
+                       tp->t_bwmeas->bw_size = 0;
+               if (tp->t_bwmeas->bw_maxsize > 0)
+                       tp->t_bwmeas->bw_size = min(tp->t_bwmeas->bw_size,
+                           tp->t_bwmeas->bw_maxsize);
+               if (tp->t_bwmeas->bw_size > 0) {
+                       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);
@@ -1869,14 +1883,16 @@ send:
                } else {
                        tcpstat.tcps_sndpack++;
                        tcpstat.tcps_sndbyte += len;
-                       
+
                        if (nstat_collect) {
                                INP_ADD_STAT(inp, cell, wifi, wired,
                                    txpackets, 1);
                                INP_ADD_STAT(inp, cell, wifi, wired,
                                    txbytes, len);
                        }
+                       inp_decr_sndbytes_unsent(so, len);
                }
+               inp_set_activity_bitmap(inp);
 #if MPTCP
                if (tp->t_mpflags & TMPF_MPTCP_TRUE) {
                        tcpstat.tcps_mp_sndpacks++;
@@ -1884,9 +1900,9 @@ send:
                }
 #endif /* MPTCP */
                /*
-                * 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 
+                * 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
@@ -1965,7 +1981,7 @@ send:
                                        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
@@ -2019,10 +2035,6 @@ send:
                m->m_len = hdrlen;
        }
        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
@@ -2037,8 +2049,8 @@ send:
                }
                svc_flags |= PKT_SCF_IPV6;
 #if PF_ECN
-               m->m_pkthdr.pf_mtag.pftag_hdr = (void *)ip6;
-               m->m_pkthdr.pf_mtag.pftag_flags |= PF_TAG_HDR_INET6;
+               m_pftag(m)->pftag_hdr = (void *)ip6;
+               m_pftag(m)->pftag_flags |= PF_TAG_HDR_INET6;
 #endif /* PF_ECN */
        } else
 #endif /* INET6 */
@@ -2054,8 +2066,8 @@ send:
                        ip->ip_tos |= IPTOS_ECN_ECT0;
                }
 #if PF_ECN
-               m->m_pkthdr.pf_mtag.pftag_hdr = (void *)ip;
-               m->m_pkthdr.pf_mtag.pftag_flags |= PF_TAG_HDR_INET;
+               m_pftag(m)->pftag_hdr = (void *)ip;
+               m_pftag(m)->pftag_flags |= PF_TAG_HDR_INET;
 #endif /* PF_ECN */
        }
 
@@ -2087,6 +2099,10 @@ send:
                if (len || (flags & (TH_SYN|TH_FIN)) ||
                    tp->t_timer[TCPT_PERSIST]) {
                        th->th_seq = htonl(tp->snd_nxt);
+                       if (len > 0) {
+                               m->m_pkthdr.tx_start_seq = tp->snd_nxt;
+                               m->m_pkthdr.pkt_flags |= PKTF_START_SEQ;
+                       }
                        if (SEQ_LT(tp->snd_nxt, tp->snd_max)) {
                                if (SACK_ENABLED(tp) && len > 1) {
                                        tcp_rxtseg_insert(tp, tp->snd_nxt,
@@ -2101,57 +2117,25 @@ send:
                }
        } else {
                th->th_seq = htonl(p->rxmit);
+               if (len > 0) {
+                       m->m_pkthdr.pkt_flags |=
+                           (PKTF_TCP_REXMT | PKTF_START_SEQ);
+                       m->m_pkthdr.tx_start_seq = p->rxmit;
+               }
                tcp_rxtseg_insert(tp, p->rxmit, (p->rxmit + len - 1));
                p->rxmit += len;
                tp->sackhint.sack_bytes_rexmit += len;
-               if (len > 0)
-                       m->m_pkthdr.pkt_flags |= PKTF_TCP_REXMT;
        }
        th->th_ack = htonl(tp->rcv_nxt);
        tp->last_ack_sent = tp->rcv_nxt;
-#if MPTCP
-       /* Initialize the ACK field to a value as 0 ack fields are dropped */
-       if (early_data_sent) {
-               th->th_ack = th->th_seq + 1;
-       }
-#endif /* MPTCP */
        if (optlen) {
                bcopy(opt, th + 1, optlen);
                th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
        }
        th->th_flags = flags;
-       /*
-        * Calculate receive window.  Don't shrink window,
-        * but avoid silly window syndrome.
-        */
-       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));
+       if (recwin > 0 && SEQ_LT(tp->rcv_adv, tp->rcv_nxt + recwin))
+               tp->rcv_adv = tp->rcv_nxt + recwin;
 
        /*
         * Adjust the RXWIN0SENT flag - indicate that we have advertised
@@ -2183,6 +2167,17 @@ send:
         * checksum extended header and data.
         */
        m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */
+
+       /*
+        * If this is potentially the last packet on the stream, then mark
+        * it in order to enable some optimizations in the underlying
+        * layers
+        */
+       if (tp->t_state != TCPS_ESTABLISHED &&
+           (tp->t_state == TCPS_CLOSING || tp->t_state == TCPS_TIME_WAIT
+           || tp->t_state == TCPS_LAST_ACK || (th->th_flags & TH_RST)))
+               m->m_pkthdr.pkt_flags |= PKTF_LAST_PKT;
+
 #if INET6
        if (isipv6) {
                /*
@@ -2192,7 +2187,7 @@ send:
                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, 
+                       th->th_sum = in_addword(th->th_sum,
                                htons((u_short)(optlen + len)));
        }
        else
@@ -2201,7 +2196,7 @@ send:
                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, 
+                       th->th_sum = in_addword(th->th_sum,
                                htons((u_short)(optlen + len)));
        }
 
@@ -2236,7 +2231,7 @@ send:
                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;
@@ -2253,6 +2248,7 @@ send:
                }
                if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
                        tp->snd_max = tp->snd_nxt;
+                       tp->t_sndtime = tcp_now;
                        /*
                         * Time this transmission if not a retransmission and
                         * not currently timing anything.
@@ -2277,9 +2273,8 @@ timer:
                        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;
-                               tp->t_rxtstart = 0;
                                tp->t_persist_stop = 0;
+                               TCP_RESET_REXMT_STATE(tp);
                        }
                        tp->t_timer[TCPT_REXMT] =
                                OFFSET_FROM_START(tp, tp->t_rxtcur);
@@ -2292,18 +2287,18 @@ timer:
                 *
                 * Every time new data is sent PTO will get reset.
                 */
-               if (tcp_enable_tlp && tp->t_state == TCPS_ESTABLISHED &&
-                   SACK_ENABLED(tp) && !IN_FASTRECOVERY(tp)
-                   && tp->snd_nxt == tp->snd_max
-                   && SEQ_GT(tp->snd_nxt, tp->snd_una)
-                   && tp->t_rxtshift == 0
-                   && (tp->t_flagsext & (TF_SENT_TLPROBE|TF_PKTS_REORDERED)) == 0) {
-                       u_int32_t pto, srtt, new_rto = 0;
+               if (tcp_enable_tlp && len != 0 && tp->t_state == TCPS_ESTABLISHED &&
+                   SACK_ENABLED(tp) && !IN_FASTRECOVERY(tp) &&
+                   tp->snd_nxt == tp->snd_max &&
+                   SEQ_GT(tp->snd_nxt, tp->snd_una) &&
+                   tp->t_rxtshift == 0 &&
+                   (tp->t_flagsext & (TF_SENT_TLPROBE|TF_PKTS_REORDERED)) == 0) {
+                       u_int32_t pto, srtt;
 
                        /*
                         * Using SRTT alone to set PTO can cause spurious
                         * retransmissions on wireless networks where there
-                        * is a lot of variance in RTT. Taking variance 
+                        * is a lot of variance in RTT. Taking variance
                         * into account will avoid this.
                         */
                        srtt = tp->t_srtt >> TCP_RTT_SHIFT;
@@ -2316,21 +2311,9 @@ timer:
                                pto = max(10, pto);
 
                        /* if RTO is less than PTO, choose RTO instead */
-                       if (tp->t_rxtcur < pto) {
-                               /*
-                                * Schedule PTO instead of RTO in favor of
-                                * fast recovery.
-                                */
+                       if (tp->t_rxtcur < pto)
                                pto = tp->t_rxtcur;
 
-                               /* Reset the next RTO to be after PTO. */
-                               TCPT_RANGESET(new_rto,
-                                   (pto + TCP_REXMTVAL(tp)),
-                                   max(tp->t_rttmin, tp->t_rttcur + 2),
-                                   TCPTV_REXMTMAX, 0);
-                               tp->t_timer[TCPT_REXMT] =
-                                   OFFSET_FROM_START(tp, new_rto);
-                       }
                        tp->t_timer[TCPT_PTO] = OFFSET_FROM_START(tp, pto);
                }
        } else {
@@ -2341,13 +2324,15 @@ timer:
                int xlen = len;
                if (flags & TH_SYN)
                        ++xlen;
-               if ((flags & TH_FIN) && 
+               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))
+               if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) {
                        tp->snd_max = tp->snd_nxt + len;
+                       tp->t_sndtime = tcp_now;
+               }
        }
 
 #if TCPDEBUG
@@ -2415,14 +2400,19 @@ timer:
 #if NECP
        {
                necp_kernel_policy_id policy_id;
+               necp_kernel_policy_id skip_policy_id;
                u_int32_t route_rule_id;
-               if (!necp_socket_is_allowed_to_send_recv(inp, &policy_id, &route_rule_id)) {
+               if (!necp_socket_is_allowed_to_send_recv(inp, &policy_id, &route_rule_id, &skip_policy_id)) {
                        m_freem(m);
                        error = EHOSTUNREACH;
                        goto out;
                }
+               necp_mark_packet_from_socket(m, inp, policy_id, route_rule_id, skip_policy_id);
 
-               necp_mark_packet_from_socket(m, inp, policy_id, route_rule_id);
+               if (net_qos_policy_restricted != 0) {
+                       necp_socket_update_qos_marking(inp, inp->inp_route.ro_rt,
+                           NULL, route_rule_id);
+               }
        }
 #endif /* NECP */
 
@@ -2442,13 +2432,13 @@ timer:
         */
        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_flags |= (PKTF_FLOW_ID | PKTF_FLOW_LOCALSRC | PKTF_FLOW_ADV);
        m->m_pkthdr.pkt_proto = IPPROTO_TCP;
+       m->m_pkthdr.tx_tcp_pid = so->last_pid;
+       if (so->so_flags & SOF_DELEGATED)
+               m->m_pkthdr.tx_tcp_e_pid = so->e_pid;
+       else
+               m->m_pkthdr.tx_tcp_e_pid = 0;
 
        m->m_nextpkt = NULL;
 
@@ -2456,19 +2446,28 @@ timer:
            !(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 
+                * 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);
+                   (inp->inp_last_outifp->if_eflags &
+                   (IFEF_TXSTART | IFEF_NOACKPRI)) == IFEF_TXSTART) {
+                       if (th->th_flags == TH_ACK &&
+                           tp->snd_una == tp->snd_max &&
+                           tp->t_timer[TCPT_REXMT] == 0)
+                               svc_flags |= PKT_SCF_TCP_ACK;
+                       if (th->th_flags & TH_SYN)
+                               svc_flags |= PKT_SCF_TCP_SYN;
+               }
+               set_packet_service_class(m, so, sotc, svc_flags);
+       } else {
+               /*
+                * Optimization for loopback just set the mbuf
+                * service class
+                */
+               (void) m_set_service_class(m, so_tc2msc(sotc));
        }
 
        tp->t_pktlist_sentlen += len;
@@ -2497,7 +2496,7 @@ timer:
        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 */      
+               /* 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;
@@ -2520,7 +2519,7 @@ timer:
 
        if (sendalot == 0 || (tp->t_state != TCPS_ESTABLISHED) ||
            (tp->snd_cwnd <= (tp->snd_wnd / 8)) ||
-           (tp->t_flags & (TH_PUSH | TF_ACKNOW)) ||
+           (tp->t_flags & TF_ACKNOW) ||
            (tp->t_flagsext & TF_FORCE) ||
            tp->t_lastchain >= tcp_packet_chaining) {
                error = 0;
@@ -2535,12 +2534,7 @@ timer:
                        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 */
+                           (sack_rxmit || (sack_bytes_rxmt != 0)), isipv6);
                        if (error) {
                                /*
                                 * Take into account the rest of unsent
@@ -2607,9 +2601,16 @@ out:
                TCP_PKTLIST_CLEAR(tp);
 
                if (error == ENOBUFS) {
+                       /*
+                        * Set retransmit timer if not currently set
+                        * when we failed to send a segment that can be
+                        * retransmitted (i.e. not pure ack or rst)
+                        */
                        if (!tp->t_timer[TCPT_REXMT] &&
-                               !tp->t_timer[TCPT_PERSIST])
-                               tp->t_timer[TCPT_REXMT] = 
+                           !tp->t_timer[TCPT_PERSIST] &&
+                           (len != 0 || (flags & (TH_SYN | TH_FIN)) != 0 ||
+                           so->so_snd.sb_cc > 0))
+                               tp->t_timer[TCPT_REXMT] =
                                        OFFSET_FROM_START(tp, tp->t_rxtcur);
                        tp->snd_cwnd = tp->t_maxseg;
                        tp->t_bytes_acked = 0;
@@ -2646,7 +2647,7 @@ out:
                 * treat EHOSTUNREACH/ENETDOWN as a soft error.
                 */
                if ((error == EHOSTUNREACH || error == ENETDOWN) &&
-                   TCPS_HAVERCVDSYN(tp->t_state) && 
+                   TCPS_HAVERCVDSYN(tp->t_state) &&
                    !inp_restricted_send(inp, inp->inp_last_outifp)) {
                                tp->t_softerror = error;
                                error = 0;
@@ -2668,22 +2669,32 @@ out:
 
 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 cnt, struct mbuf *opt, int flags, int sack_in_progress, 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 ip_out_args ipoa;
        struct route ro;
        struct ifnet *outif = NULL;
+
+       bzero(&ipoa, sizeof(ipoa));
+       ipoa.ipoa_boundif = IFSCOPE_NONE;
+       ipoa.ipoa_flags = IPOAF_SELECT_SRCIF | IPOAF_BOUND_SRCADDR;
+       ipoa.ipoa_sotc = SO_TC_UNSPEC;
+       ipoa.ipoa_netsvctype = _NET_SERVICE_TYPE_UNSPEC;
 #if INET6
-       struct ip6_out_args ip6oa =
-           { IFSCOPE_NONE, { 0 }, IP6OAF_SELECT_SRCIF|IP6OAF_BOUND_SRCADDR, 0 };
+       struct ip6_out_args ip6oa;
        struct route_in6 ro6;
+
+       bzero(&ip6oa, sizeof(ip6oa));
+       ip6oa.ip6oa_boundif = IFSCOPE_NONE;
+       ip6oa.ip6oa_flags = IP6OAF_SELECT_SRCIF | IP6OAF_BOUND_SRCADDR;
+       ip6oa.ip6oa_sotc = SO_TC_UNSPEC;
+       ip6oa.ip6oa_netsvctype = _NET_SERVICE_TYPE_UNSPEC;
+
        struct flowadv *adv =
            (isipv6 ? &ip6oa.ip6oa_flowadv : &ipoa.ipoa_flowadv);
 #else /* INET6 */
@@ -2711,7 +2722,7 @@ tcp_ip_output(struct socket *so, struct tcpcb *tp, struct mbuf *pkt,
                else
 #endif /* INET6 */
                        ipoa.ipoa_flags |=  IPOAF_NO_CELLULAR;
-       } 
+       }
        if (INP_NO_EXPENSIVE(inp)) {
 #if INET6
                if (isipv6)
@@ -2719,7 +2730,7 @@ tcp_ip_output(struct socket *so, struct tcpcb *tp, struct mbuf *pkt,
                else
 #endif /* INET6 */
                        ipoa.ipoa_flags |=  IPOAF_NO_EXPENSIVE;
-       
+
        }
        if (INP_AWDL_UNRESTRICTED(inp)) {
 #if INET6
@@ -2728,7 +2739,28 @@ tcp_ip_output(struct socket *so, struct tcpcb *tp, struct mbuf *pkt,
                else
 #endif /* INET6 */
                        ipoa.ipoa_flags |=  IPOAF_AWDL_UNRESTRICTED;
-       
+
+       }
+#if INET6
+       if (INP_INTCOPROC_ALLOWED(inp) && isipv6) {
+               ip6oa.ip6oa_flags |=  IP6OAF_INTCOPROC_ALLOWED;
+       }
+       if (isipv6) {
+               ip6oa.ip6oa_sotc = so->so_traffic_class;
+               ip6oa.ip6oa_netsvctype = so->so_netsvctype;
+       } else
+#endif /* INET6 */
+       {
+               ipoa.ipoa_sotc = so->so_traffic_class;
+               ipoa.ipoa_netsvctype = so->so_netsvctype;
+       }
+       if ((so->so_flags1 & SOF1_QOSMARKING_ALLOWED)) {
+#if INET6
+               if (isipv6)
+                       ip6oa.ip6oa_flags |= IP6OAF_QOSMARKING_ALLOWED;
+               else
+#endif /* INET6 */
+                       ipoa.ipoa_flags |= IPOAF_QOSMARKING_ALLOWED;
        }
 #if INET6
        if (isipv6)
@@ -2746,14 +2778,9 @@ tcp_ip_output(struct socket *so, struct tcpcb *tp, struct mbuf *pkt,
                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.
         * Make sure ACK/DELACK conditions are cleared before
         * we unlock the socket.
         */
-       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->t_flags &= ~(TF_ACKNOW | TF_DELACK);
        tp->t_timer[TCPT_DELACK] = 0;
@@ -2773,12 +2800,12 @@ tcp_ip_output(struct socket *so, struct tcpcb *tp, struct mbuf *pkt,
         */
        if (tcp_output_unlocked && !so->so_upcallusecount &&
            (tp->t_state == TCPS_ESTABLISHED) && (sack_in_progress == 0) &&
-           !IN_FASTRECOVERY(tp)) {
+           !IN_FASTRECOVERY(tp) && !(so->so_flags & SOF_MP_SUBFLOW)) {
 
                unlocked = TRUE;
                socket_unlock(so, 0);
        }
-       
+
        /*
         * Don't send down a chain of packets when:
         * - TCP chaining is disabled
@@ -2843,27 +2870,29 @@ tcp_ip_output(struct socket *so, struct tcpcb *tp, struct mbuf *pkt,
        if (unlocked)
                socket_lock(so, 0);
 
-       /* 
+       /*
         * Enter flow controlled state if the connection is established
-        * and is not in recovery.
+        * and is not in recovery. Flow control is allowed only if there
+        * is outstanding data.
         *
-        * A connection will enter suspended state even if it is in 
+        * 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) && 
+           adv->code == FADV_SUSPENDED) &&
            !(tp->t_flags & TF_CLOSING) &&
-           tp->t_state == TCPS_ESTABLISHED) {
+           tp->t_state == TCPS_ESTABLISHED &&
+           SEQ_GT(tp->snd_max, tp->snd_una)) {
                int rc;
                rc = inp_set_fc_state(inp, adv->code);
 
-               if (rc == 1) 
-                       tcp_ccdbg_trace(tp, NULL, 
+               if (rc == 1)
+                       tcp_ccdbg_trace(tp, NULL,
                            ((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.
@@ -2877,18 +2906,28 @@ tcp_ip_output(struct socket *so, struct tcpcb *tp, struct mbuf *pkt,
 
 #if INET6
        if (isipv6) {
-               if (ro6.ro_rt != NULL && (outif = ro6.ro_rt->rt_ifp) !=
-                   inp->in6p_last_outifp)
-                       inp->in6p_last_outifp = outif;
+               if (ro6.ro_rt != NULL)
+                       outif = ro6.ro_rt->rt_ifp;
        } else
 #endif /* INET6 */
-               if (ro.ro_rt != NULL && (outif = ro.ro_rt->rt_ifp) !=
-                   inp->inp_last_outifp)
-                       inp->inp_last_outifp = outif;
+               if (ro.ro_rt != NULL)
+                       outif = ro.ro_rt->rt_ifp;
+
+       if (outif != NULL && outif != inp->inp_last_outifp &&
+           so->so_snd.sb_cc > 0) {
+               /* Update the send byte count */
+               if (so->so_snd.sb_flags & SB_SNDBYTE_CNT) {
+                       inp_decr_sndbytes_total(so, so->so_snd.sb_cc);
+                       inp_decr_sndbytes_allunsent(so, tp->snd_una);
+                       so->so_snd.sb_flags &= ~SB_SNDBYTE_CNT;
+               }
+               inp->inp_last_outifp = outif;
 
-       if (error != 0 && ifdenied && 
+       }
+
+       if (error != 0 && ifdenied &&
            (INP_NO_CELLULAR(inp) || INP_NO_EXPENSIVE(inp)))
-               soevent(inp->inp_socket,
+               soevent(so,
                    (SO_FILT_HINT_LOCKED|SO_FILT_HINT_IFDENIED));
 
        /* Synchronize cached PCB route & options */
@@ -2899,7 +2938,7 @@ tcp_ip_output(struct socket *so, struct tcpcb *tp, struct mbuf *pkt,
 #endif /* INET6 */
                inp_route_copyin(inp, &ro);
 
-       if (tp->t_state < TCPS_ESTABLISHED && tp->t_rxtshift == 0 && 
+       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
@@ -2910,9 +2949,10 @@ tcp_ip_output(struct socket *so, struct tcpcb *tp, struct mbuf *pkt,
        return (error);
 }
 
+int tcptv_persmin_val = TCPTV_PERSMIN;
+
 void
-tcp_setpersist(tp)
-       register struct tcpcb *tp;
+tcp_setpersist(struct tcpcb *tp)
 {
        int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
 
@@ -2933,7 +2973,7 @@ tcp_setpersist(tp)
         */
        TCPT_RANGESET(tp->t_timer[TCPT_PERSIST],
            t * tcp_backoff[tp->t_rxtshift],
-           TCPTV_PERSMIN, TCPTV_PERSMAX, 0);
+           tcptv_persmin_val, TCPTV_PERSMAX, 0);
        tp->t_timer[TCPT_PERSIST] = OFFSET_FROM_START(tp, tp->t_timer[TCPT_PERSIST]);
 
        if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
@@ -2951,8 +2991,8 @@ tcp_send_lroacks(struct tcpcb *tp, struct mbuf *m, struct tcphdr *th)
        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 tack_offset = 28; /* IPv6 and IP options not supported */
+       int twin_offset = 34; /* 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;
@@ -3043,17 +3083,16 @@ 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
                 */
@@ -3061,26 +3100,26 @@ tcp_recv_throttle (struct tcpcb *tp)
                        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) {
+                       if (tp->t_rttcur > (base_rtt + target_qdelay)) {
                                tp->t_flagsext |= TF_RECV_THROTTLE;
-
+                               if (tp->t_recv_throttle_ts == 0)
+                                       tp->t_recv_throttle_ts = tcp_now;
                                /*
                                 * Reduce the recv socket buffer size to
                                 * minimize latecy.
                                 */
-                               if (sbrcv->sb_idealsize > 
+                               if (sbrcv->sb_idealsize >
                                    tcp_recv_throttle_minwin) {
                                        newsize = sbrcv->sb_idealsize >> 1;
                                        /* Set a minimum of 16 K */
-                                       newsize = 
-                                           max(newsize, 
+                                       newsize =
+                                           max(newsize,
                                            tcp_recv_throttle_minwin);
                                        sbrcv->sb_idealsize = newsize;
                                }
@@ -3097,6 +3136,6 @@ tcp_recv_throttle (struct tcpcb *tp)
         */
        if (tp->acc_iaj > tcp_acc_iaj_react_limit)
                return (1);
-       
+
        return (0);
 }