/* * Copyright (c) 2000-2022 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 * 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. * * Please obtain a copy of the License at * http://www.opensource.apple.com/apsl/ and read it before using this file. * * The Original Code and all software distributed under the License are * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE, 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@ */ /* * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * 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. */ #define _IP_VHL #include "tcp_includes.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #if TCPDEBUG #include #endif #include #include #include #if IPSEC #include #endif /*IPSEC*/ #if MPTCP #include #include #include #include #endif #include #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) SYSCTL_SKMEM_TCP_INT(OID_AUTO, path_mtu_discovery, CTLFLAG_RW | CTLFLAG_LOCKED, int, path_mtu_discovery, 1, "Enable Path MTU Discovery"); 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"); SYSCTL_SKMEM_TCP_INT(OID_AUTO, tso, CTLFLAG_RW | CTLFLAG_LOCKED, int, tcp_do_tso, 1, "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"); SYSCTL_SKMEM_TCP_INT(OID_AUTO, accurate_ecn, CTLFLAG_RW | CTLFLAG_LOCKED, int, tcp_acc_ecn, 0, "Accurate ECN mode (0: disable, 1: enable ACE feedback"); // TO BE REMOVED SYSCTL_SKMEM_TCP_INT(OID_AUTO, do_ack_compression, CTLFLAG_RW | CTLFLAG_LOCKED, int, tcp_do_ack_compression, 1, "Enable TCP ACK compression (on (cell only): 1, off: 0, on (all interfaces): 2)"); SYSCTL_SKMEM_TCP_INT(OID_AUTO, ack_compression_rate, CTLFLAG_RW | CTLFLAG_LOCKED, int, tcp_ack_compression_rate, TCP_COMP_CHANGE_RATE, "Rate at which we force sending new ACKs (in ms)"); SYSCTL_SKMEM_TCP_INT(OID_AUTO, randomize_timestamps, CTLFLAG_RW | CTLFLAG_LOCKED, int, tcp_randomize_timestamps, 1, "Randomize TCP timestamps to prevent tracking (on: 1, off: 0)"); static int sysctl_change_ecn_setting SYSCTL_HANDLER_ARGS { #pragma unused(oidp, arg1, arg2) int i, err = 0, changed = 0; struct ifnet *ifp; err = sysctl_io_number(req, tcp_ecn_outbound, sizeof(int32_t), &i, &changed); if (err != 0 || req->newptr == USER_ADDR_NULL) { return err; } if (changed) { 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)) { /* * Reset ECN enable flags on non-cellular * interfaces so that the system default will take * over */ ifnet_head_lock_shared(); TAILQ_FOREACH(ifp, &ifnet_head, if_link) { if (!IFNET_IS_CELLULAR(ifp)) { if_clear_eflags(ifp, IFEF_ECN_ENABLE | IFEF_ECN_DISABLE); } } ifnet_head_done(); } else { /* * Set ECN enable flags on non-cellular * interfaces */ ifnet_head_lock_shared(); TAILQ_FOREACH(ifp, &ifnet_head, if_link) { if (!IFNET_IS_CELLULAR(ifp)) { if_set_eflags(ifp, IFEF_ECN_ENABLE); if_clear_eflags(ifp, IFEF_ECN_DISABLE); } } 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) { tcp_ecn_inbound = i; SYSCTL_SKMEM_UPDATE_FIELD(tcp.ecn_negotiate_in, tcp_ecn_inbound); } return err; } int tcp_ecn_outbound = 2; SYSCTL_PROC(_net_inet_tcp, OID_AUTO, ecn_initiate_out, CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_ecn_outbound, 0, sysctl_change_ecn_setting, "IU", "Initiate ECN for outbound connections"); int tcp_ecn_inbound = 2; SYSCTL_PROC(_net_inet_tcp, OID_AUTO, ecn_negotiate_in, CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_ecn_inbound, 0, sysctl_change_ecn_setting, "IU", "Initiate ECN for inbound connections"); SYSCTL_SKMEM_TCP_INT(OID_AUTO, packetchain, CTLFLAG_RW | CTLFLAG_LOCKED, int, tcp_packet_chaining, 50, "Enable TCP output packet chaining"); 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"); 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"); 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"); SYSCTL_SKMEM_TCP_INT(OID_AUTO, autosndbufinc, CTLFLAG_RW | CTLFLAG_LOCKED, uint32_t, tcp_autosndbuf_inc, 8 * 1024, "Increment in send socket bufffer size"); SYSCTL_SKMEM_TCP_INT(OID_AUTO, autosndbufmax, CTLFLAG_RW | CTLFLAG_LOCKED | CTLFLAG_KERN, uint32_t, tcp_autosndbuf_max, 2 * 1024 * 1024, "Maximum send socket buffer size"); 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"); 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"); SYSCTL_SKMEM_TCP_INT(OID_AUTO, enable_tlp, CTLFLAG_RW | CTLFLAG_LOCKED, int32_t, tcp_enable_tlp, 1, "Enable Tail loss probe"); static int32_t packchain_newlist = 0; static int32_t packchain_looped = 0; static int32_t packchain_sent = 0; /* temporary: for testing */ #if IPSEC extern int ipsec_bypass; #endif extern int slowlink_wsize; /* window correction for slow links */ extern u_int32_t kipf_count; static int tcp_ip_output(struct socket *, struct tcpcb *, struct mbuf *, int, struct mbuf *, int, int, boolean_t); static int tcp_recv_throttle(struct tcpcb *tp); __attribute__((noinline)) static int32_t tcp_tfo_check(struct tcpcb *tp, int32_t len) { struct socket *so = tp->t_inpcb->inp_socket; unsigned int optlen = 0; unsigned int cookie_len; if (tp->t_flags & TF_NOOPT) { goto fallback; } if (!(tp->t_flagsext & TF_FASTOPEN_FORCE_ENABLE) && !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; if (tp->t_flags & TF_REQ_SCALE) { optlen += 4; } #if MPTCP if ((so->so_flags & SOF_MP_SUBFLOW) && mptcp_enable && (tp->t_rxtshift <= mptcp_mpcap_retries || (tptomptp(tp)->mpt_mpte->mpte_flags & MPTE_FORCE_ENABLE))) { optlen += sizeof(struct mptcp_mpcapable_opt_common) + sizeof(mptcp_key_t); } #endif /* MPTCP */ if (tp->t_flags & TF_REQ_TSTMP) { optlen += TCPOLEN_TSTAMP_APPA; } if (SACK_ENABLED(tp)) { optlen += TCPOLEN_SACK_PERMITTED; } /* Now, decide whether to use TFO or not */ /* Don't even bother trying if there is no space at all... */ if (MAX_TCPOPTLEN - optlen < TCPOLEN_FASTOPEN_REQ) { goto fallback; } cookie_len = tcp_cache_get_cookie_len(tp); if (cookie_len == 0) { /* 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; } /* Ok, everything looks good. We can go on and do TFO */ return len; fallback: tcp_disable_tfo(tp); return 0; } /* Returns the number of bytes written to the TCP option-space */ __attribute__((noinline)) static unsigned int tcp_tfo_write_cookie_rep(struct tcpcb *tp, unsigned int optlen, u_char *opt) { u_char out[CCAES_BLOCK_SIZE]; unsigned ret = 0; u_char *bp; if (MAX_TCPOPTLEN - optlen < TCPOLEN_FASTOPEN_REQ + TFO_COOKIE_LEN_DEFAULT) { return ret; } tcp_tfo_gen_cookie(tp->t_inpcb, out, sizeof(out)); bp = opt + optlen; *bp++ = TCPOPT_FASTOPEN; *bp++ = 2 + TFO_COOKIE_LEN_DEFAULT; memcpy(bp, out, TFO_COOKIE_LEN_DEFAULT); ret += 2 + TFO_COOKIE_LEN_DEFAULT; tp->t_tfo_stats |= TFO_S_COOKIE_SENT; tcpstat.tcps_tfo_cookie_sent++; return ret; } __attribute__((noinline)) static unsigned int tcp_tfo_write_cookie(struct tcpcb *tp, unsigned int optlen, int32_t len, u_char *opt) { uint8_t tfo_len; struct socket *so = tp->t_inpcb->inp_socket; unsigned ret = 0; int res; u_char *bp; if (TCPOLEN_FASTOPEN_REQ > MAX_TCPOPTLEN - optlen) { return 0; } tfo_len = (uint8_t)(MAX_TCPOPTLEN - optlen - TCPOLEN_FASTOPEN_REQ); 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; /* * The cookie will be copied in the appropriate place within the * TCP-option space. That way we avoid the need for an intermediate * variable. */ res = tcp_cache_get_cookie(tp, bp + TCPOLEN_FASTOPEN_REQ, &tfo_len); if (res == 0) { *bp++ = TCPOPT_FASTOPEN; *bp++ = TCPOLEN_FASTOPEN_REQ; ret += TCPOLEN_FASTOPEN_REQ; tp->t_tfo_flags |= TFO_F_COOKIE_REQ; tp->t_tfo_stats |= TFO_S_COOKIE_REQ; tcpstat.tcps_tfo_cookie_req++; } else { *bp++ = TCPOPT_FASTOPEN; *bp++ = TCPOLEN_FASTOPEN_REQ + tfo_len; ret += TCPOLEN_FASTOPEN_REQ + tfo_len; tp->t_tfo_flags |= TFO_F_COOKIE_SENT; /* 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 ret; } static inline bool tcp_send_ecn_flags_on_syn(struct tcpcb *tp) { /* We allow Accurate ECN negotiation on first retransmission as well */ bool send_on_first_retrans = (tp->ecn_flags & TE_ACE_SETUPSENT) && (tp->t_rxtshift <= 1); return !(tp->ecn_flags & (TE_SETUPSENT | TE_ACE_SETUPSENT)) || send_on_first_retrans; } void tcp_set_ecn(struct tcpcb *tp, struct ifnet *ifp) { boolean_t inbound; /* * Socket option has precedence */ if (tp->ecn_flags & TE_ECN_MODE_ENABLE) { tp->ecn_flags |= TE_ENABLE_ECN; goto check_heuristic; } if (tp->ecn_flags & TE_ECN_MODE_DISABLE) { tp->ecn_flags &= ~TE_ENABLE_ECN; return; } /* * Per interface setting comes next */ if (ifp != NULL) { if (ifp->if_eflags & IFEF_ECN_ENABLE) { tp->ecn_flags |= TE_ENABLE_ECN; goto check_heuristic; } if (ifp->if_eflags & IFEF_ECN_DISABLE) { tp->ecn_flags &= ~TE_ENABLE_ECN; return; } } /* * System wide settings come last */ inbound = (tp->t_inpcb->inp_socket->so_head != NULL); if ((inbound && tcp_ecn_inbound == 1) || (!inbound && tcp_ecn_outbound == 1)) { tp->ecn_flags |= TE_ENABLE_ECN; goto check_heuristic; } else { tp->ecn_flags &= ~TE_ENABLE_ECN; } return; check_heuristic: if (TCP_ACC_ECN_ENABLED(tp)) { /* Allow ECN when Accurate ECN is enabled until heuristics are fixed */ tp->ecn_flags |= TE_ENABLE_ECN; /* Set the accurate ECN state */ if (tp->t_client_accecn_state == tcp_connection_client_accurate_ecn_feature_disabled) { tp->t_client_accecn_state = tcp_connection_client_accurate_ecn_feature_enabled; } if (tp->t_server_accecn_state == tcp_connection_server_accurate_ecn_feature_disabled) { tp->t_server_accecn_state = tcp_connection_server_accurate_ecn_feature_enabled; } } if (!tcp_heuristic_do_ecn(tp) && !TCP_ACC_ECN_ENABLED(tp)) { /* Allow ECN when Accurate ECN is enabled until heuristics are fixed */ tp->ecn_flags &= ~TE_ENABLE_ECN; } /* * If the interface setting, system-level setting and heuristics * allow to enable ECN, randomly select 5% of connections to * enable it */ if ((tp->ecn_flags & (TE_ECN_MODE_ENABLE | TE_ECN_MODE_DISABLE | TE_ENABLE_ECN)) == TE_ENABLE_ECN) { /* * Use the random value in iss for randomizing * this selection */ if ((tp->iss % 100) >= tcp_ecn_setup_percentage && !TCP_ACC_ECN_ENABLED(tp)) { /* Don't disable Accurate ECN randomly */ tp->ecn_flags &= ~TE_ENABLE_ECN; } } } int tcp_flight_size(struct tcpcb *tp) { int ret; VERIFY(tp->sackhint.sack_bytes_acked >= 0); VERIFY(tp->sackhint.sack_bytes_rexmit >= 0); /* * RFC6675, SetPipe (), SACK'd bytes are discounted. All the rest is still in-flight. */ ret = tp->snd_nxt - tp->snd_una - tp->sackhint.sack_bytes_acked; if (ret < 0) { /* * This happens when the RTO-timer fires because snd_nxt gets artificially * decreased. If we then receive some SACK-blogs, sack_bytes_acked is * going to be high. */ ret = 0; } return ret; } /* * Either of ECT0 or ECT1 flag should be set * when this function is called */ static void tcp_add_accecn_option(struct tcpcb *tp, uint16_t flags, uint32_t *lp, uint8_t *optlen) { uint8_t max_len = TCP_MAXOLEN - *optlen; uint8_t len = TCPOLEN_ACCECN_EMPTY; uint32_t e1b = (uint32_t)(tp->t_rcv_ect1_bytes & TCP_ACO_MASK); uint32_t e0b = (uint32_t)(tp->t_rcv_ect0_bytes & TCP_ACO_MASK); uint32_t ceb = (uint32_t)(tp->t_rcv_ce_bytes & TCP_ACO_MASK); if (max_len < TCPOLEN_ACCECN_EMPTY) { TCP_LOG(tp, "not enough space to add any AccECN option"); return; } if (!(flags & TH_SYN || (tp->ecn_flags & TE_ACE_FINAL_ACK_3WHS) || tp->snd_una == tp->iss + 1 || tp->ecn_flags & (TE_ACO_ECT1 | TE_ACO_ECT0))) { /* * Since this is neither a SYN-ACK packet, nor the final ACK of * the 3WHS (nor the first acked data segment) nor any of the ECT byte * counter flags are set, no need to send the option. */ return; } if ((flags & (TH_SYN | TH_ACK)) == (TH_SYN | TH_ACK) && tp->t_rxtshift >= 1) { /* * If this is a SYN-ACK retransmission (first), * retry without AccECN option and just with ACE fields. * From second retransmission onwards, we don't send any * Accurate ECN state. */ return; } if (max_len < (TCPOLEN_ACCECN_EMPTY + 1 * TCPOLEN_ACCECN_COUNTER)) { /* Can carry EMPTY option which can be used to test path in SYN-ACK packet */ if (flags & TH_SYN) { *lp++ = htonl((TCPOPT_ACCECN1 << 24) | (len << 16) | (TCPOPT_NOP << 8) | TCPOPT_NOP); *optlen += len + 2; /* 2 NOPs */ TCP_LOG(tp, "add empty AccECN option, optlen=%u", *optlen); } } else if (max_len < (TCPOLEN_ACCECN_EMPTY + 2 * TCPOLEN_ACCECN_COUNTER)) { /* Can carry one option */ len += 1 * TCPOLEN_ACCECN_COUNTER; if (tp->ecn_flags & TE_ACO_ECT1) { *lp++ = htonl((TCPOPT_ACCECN1 << 24) | (len << 16) | ((e1b >> 8) & 0xffff)); *lp++ = htonl(((e1b & 0xff) << 24) | (TCPOPT_NOP << 16) | (TCPOPT_NOP << 8) | TCPOPT_NOP); } else { *lp++ = htonl((TCPOPT_ACCECN0 << 24) | (len << 16) | ((e0b >> 8) & 0xffff)); *lp++ = htonl(((e0b & 0xff) << 24) | (TCPOPT_NOP << 16) | (TCPOPT_NOP << 8) | TCPOPT_NOP); } *optlen += len + 3; /* 3 NOPs */ TCP_LOG(tp, "add single counter for AccECN option, optlen=%u", *optlen); } else if (max_len < (TCPOLEN_ACCECN_EMPTY + 3 * TCPOLEN_ACCECN_COUNTER)) { /* Can carry two options */ len += 2 * TCPOLEN_ACCECN_COUNTER; if (tp->ecn_flags & TE_ACO_ECT1) { *lp++ = htonl((TCPOPT_ACCECN1 << 24) | (len << 16) | ((e1b >> 8) & 0xffff)); *lp++ = htonl(((e1b & 0xff) << 24) | (ceb & 0xffffff)); } else { *lp++ = htonl((TCPOPT_ACCECN0 << 24) | (len << 16) | ((e0b >> 8) & 0xffff)); *lp++ = htonl(((e0b & 0xff) << 24) | (ceb & 0xffffff)); } *optlen += len; /* 0 NOPs */ TCP_LOG(tp, "add 2 counters for AccECN option, optlen=%u", *optlen); } else { /* * TCP option sufficient to hold full AccECN option * but send counter that changed during the entire connection. */ len += 3 * TCPOLEN_ACCECN_COUNTER; /* Can carry all three options */ if (tp->ecn_flags & TE_ACO_ECT1) { *lp++ = htonl((TCPOPT_ACCECN1 << 24) | (len << 16) | ((e1b >> 8) & 0xffff)); *lp++ = htonl(((e1b & 0xff) << 24) | (ceb & 0xffffff)); *lp++ = htonl(((e0b & 0xffffff) << 8) | TCPOPT_NOP); } else { *lp++ = htonl((TCPOPT_ACCECN0 << 24) | (len << 16) | ((e0b >> 8) & 0xffff)); *lp++ = htonl(((e0b & 0xff) << 24) | (ceb & 0xffffff)); *lp++ = htonl(((e1b & 0xffffff) << 8) | TCPOPT_NOP); } *optlen += len + 1; /* 1 NOP */ TCP_LOG(tp, "add all 3 counters for AccECN option, optlen=%u", *optlen); } } /* * 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 tcp_output(struct tcpcb *tp) { struct inpcb *inp = tp->t_inpcb; struct socket *so = inp->inp_socket; int32_t len, recwin, sendwin, off; uint32_t max_len = 0; uint16_t flags; int error; struct mbuf *m; struct ip *ip = NULL; struct ip6_hdr *ip6 = NULL; struct tcphdr *th; u_char opt[TCP_MAXOLEN]; unsigned int ipoptlen, optlen, hdrlen; int idle, sendalot, lost = 0; int sendalot_cnt = 0; int i, sack_rxmit; int tso = 0; int sack_bytes_rxmt; tcp_seq old_snd_nxt = 0; struct sackhole *p; #if IPSEC size_t ipsec_optlen = 0; #endif /* IPSEC */ int idle_time = 0; struct mbuf *packetlist = NULL; struct mbuf *tp_inp_options = inp->inp_depend4.inp4_options; int isipv6 = inp->inp_vflag & INP_IPV6; int packchain_listadd = 0; int so_options = so->so_options; struct rtentry *rt; u_int32_t svc_flags = 0, allocated_len; #if MPTCP 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; boolean_t do_not_compress = FALSE; boolean_t sack_rxmted = FALSE; /* * Determine length of data that should be transmitted, * and flags that will be used. * If there is some data or critical controls (SYN, RST) * to send, then transmit; otherwise, investigate further. */ 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 && (tp->tcp_cc_index != TCP_CC_ALGO_CUBIC_INDEX || idle_time >= TCP_CC_CWND_NONVALIDATED_PERIOD)) { CC_ALGO(tp)->after_idle(tp); tcp_ccdbg_trace(tp, NULL, TCP_CC_IDLE_TIMEOUT); } /* * Do some other tasks that need to be done after * idle time */ if (!SLIST_EMPTY(&tp->t_rxt_segments)) { tcp_rxtseg_clean(tp); } /* If stretch ack was auto-disabled, re-evaluate it */ tcp_cc_after_idle_stretchack(tp); tp->t_forced_acks = TCP_FORCED_ACKS_COUNT; } 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. */ return 0; } #endif /* MPTCP */ again: #if MPTCP mptcp_acknow = FALSE; if (so->so_flags & SOF_MP_SUBFLOW && SEQ_LT(tp->snd_nxt, tp->snd_una)) { os_log_error(mptcp_log_handle, "%s - %lx: snd_nxt is %u and snd_una is %u, cnt %d\n", __func__, (unsigned long)VM_KERNEL_ADDRPERM(tp->t_mpsub->mpts_mpte), tp->snd_nxt, tp->snd_una, sendalot_cnt); } #endif do_not_compress = FALSE; sendalot_cnt++; KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_START, 0, 0, 0, 0, 0); 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 { 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; soif2kcl(so, FALSE); 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] == 0) { tp->t_timer[TCPT_REXMT] = OFFSET_FROM_START(tp, tp->t_rxtcur); if (tp->t_timer[TCPT_PERSIST] != 0) { tp->t_timer[TCPT_PERSIST] = 0; tp->t_persist_stop = 0; TCP_RESET_REXMT_STATE(tp); } } 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_LOG_OUTPUT(tp, "no source address silently ignored"); 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); soif2kcl(so, (ifp->if_eflags & IFEF_2KCL)); tcp_set_ecn(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)); wired = (!wifi && IFNET_IS_WIRED(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)) { max_len = tcp_sack_adjust(tp); } sendalot = 0; off = tp->snd_nxt - tp->snd_una; 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]; /* * 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; if (tcp_do_better_lr) { cwin = min(tp->snd_wnd, tp->snd_cwnd) - tcp_flight_size(tp); if (cwin <= 0 && sack_rxmted == FALSE) { /* Allow to clock out at least on per period */ cwin = tp->t_maxseg; } sack_rxmted = TRUE; } else { 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; sack_rxmit = 1; sendalot = 1; /* Everything sent after snd_nxt will allow us to account for fast-retransmit of the retransmitted segment */ tp->send_highest_sack = tp->snd_nxt; tp->t_new_dupacks = 0; tcpstat.tcps_sack_rexmits++; tcpstat.tcps_sack_rexmit_bytes += 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. */ if (tp->t_flags & TF_NEEDFIN) { flags |= TH_FIN; } /* * If in persist timeout with window of 0, send 1 byte. * Otherwise, if window is small but nonzero * and timer expired, we will send what we can * and go to transmit state. */ if (tp->t_flagsext & TF_FORCE) { if (sendwin == 0) { /* * If we still have some data to send, then * clear the FIN bit. Usually this would * happen below when it realizes that we * aren't sending all the data. However, * if we have exactly 1 byte of unsent data, * then it won't clear the FIN bit below, * and if we are in persist state, we wind * up sending the packet without recording * that we sent the FIN bit. * * We can't just blindly clear the FIN bit, * because if we don't have any more data * to send then the probe will be the FIN * itself. */ if (off < so->so_snd.sb_cc) { flags &= ~TH_FIN; } sendwin = 1; } else { tp->t_timer[TCPT_PERSIST] = 0; tp->t_persist_stop = 0; TCP_RESET_REXMT_STATE(tp); } } /* * 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 (tcp_do_better_lr) { cwin = tp->snd_cwnd - tcp_flight_size(tp); } else { cwin = tp->snd_cwnd - (tp->snd_nxt - tp->sack_newdata) - sack_bytes_rxmt; } if (cwin < 0) { cwin = 0; } /* * 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) { len = imin(len, cwin); } else { len = 0; } /* * At this point SACK recovery can not send any * data from scoreboard or any new data. Check * if we can do a rescue retransmit towards the * tail end of recovery window. */ if (len == 0 && cwin > 0 && SEQ_LT(tp->snd_fack, tp->snd_recover) && !(tp->t_flagsext & TF_RESCUE_RXT)) { len = min((tp->snd_recover - tp->snd_fack), tp->t_maxseg); len = imin(len, cwin); old_snd_nxt = tp->snd_nxt; sack_rescue_rxt = TRUE; tp->snd_nxt = tp->snd_recover - len; /* * If FIN has been sent, snd_max * must have been advanced to cover it. */ if ((tp->t_flags & TF_SENTFIN) && tp->snd_max == tp->snd_recover) { tp->snd_nxt--; } off = tp->snd_nxt - tp->snd_una; sendalot = 0; tp->t_flagsext |= TF_RESCUE_RXT; } } } if (max_len != 0 && len > 0) { len = min(len, max_len); } /* * 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 * know that foreign host supports TAO, suppress sending segment. */ if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { if (tp->t_state == TCPS_SYN_RECEIVED && tfo_enabled(tp) && tp->snd_nxt == tp->snd_una + 1) { /* We are sending the SYN again! */ off--; len++; } else { if (tp->t_state != TCPS_SYN_RECEIVED || tfo_enabled(tp)) { flags &= ~TH_SYN; } off--; len++; 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)), isipv6); } /* * 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. * This measure is needed to prevent interoperability problems * with not fully conformant TCP implementations. * * In case of TFO, we handle the setting of the len in * tcp_tfo_check. In case TFO is not enabled, never ever send * SYN+data. */ if ((flags & TH_SYN) && !tfo_enabled(tp)) { len = 0; flags &= ~TH_FIN; } /* * Don't send a RST with data. */ if (flags & TH_RST) { len = 0; } if ((flags & TH_SYN) && tp->t_state <= TCPS_SYN_SENT && tfo_enabled(tp)) { len = tcp_tfo_check(tp, len); } /* * 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, * 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 * if it isn't already going. If the window didn't * close completely, just wait for an ACK. */ len = 0; if (sendwin == 0) { tp->t_timer[TCPT_REXMT] = 0; tp->t_timer[TCPT_PTO] = 0; TCP_RESET_REXMT_STATE(tp); tp->snd_nxt = tp->snd_una; off = 0; 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. */ if (!INP_WAIT_FOR_IF_FEEDBACK(inp) && !IN_FASTRECOVERY(tp) && (so->so_snd.sb_flags & (SB_AUTOSIZE | SB_TRIM)) == SB_AUTOSIZE) { 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))) { 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; } } } /* * 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, * filters 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 ((tp->t_flags & TF_TSO) && tcp_do_tso && hwcksum_tx && kipf_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 ) { tso = 1; sendalot = 0; } else { len = tp->t_maxseg; sendalot = 1; tso = 0; } } else { tso = 0; } /* Send one segment or less as a tail loss probe */ if (tp->t_flagsext & TF_SENT_TLPROBE) { len = min(len, tp->t_maxseg); sendalot = 0; tso = 0; } #if MPTCP if (so->so_flags & SOF_MP_SUBFLOW && off < 0) { os_log_error(mptcp_log_handle, "%s - %lx: offset is negative! len %d off %d\n", __func__, (unsigned long)VM_KERNEL_ADDRPERM(tp->t_mpsub->mpts_mpte), len, off); } if ((so->so_flags & SOF_MP_SUBFLOW) && !(tp->t_mpflags & TMPF_TCP_FALLBACK)) { int newlen = len; struct mptcb *mp_tp = tptomptp(tp); 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 && mp_tp->mpt_version == MPTCP_VERSION_0) || tp->t_mpflags & TMPF_SND_JACK || tp->t_mpflags & TMPF_MPTCP_ECHO_ADDR)) { if (len > 0) { len = 0; tso = 0; } /* * 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 * option can be sent in one packet, reduce length to match * the contiguous MPTCP level. Set sendalot to send remainder. */ if (len > 0 && off >= 0) { newlen = mptcp_adj_sendlen(so, off); } if (newlen < len) { len = newlen; if (len <= tp->t_maxseg) { tso = 0; } } } #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; } } /* * 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. */ recwin = tcp_sbspace(tp); if (!(so->so_flags & SOF_MP_SUBFLOW)) { if (recwin < (int32_t)(so->so_rcv.sb_hiwat / 4) && recwin < (int)tp->t_maxseg) { recwin = 0; } } else { struct mptcb *mp_tp = tptomptp(tp); struct socket *mp_so = mptetoso(mp_tp->mpt_mpte); if (recwin < (int32_t)(mp_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)) { /* * Timestamp MUST be supported to use rledbat unless we haven't * yet negotiated it. */ if (TCP_RLEDBAT_ENABLED(tp) || (tcp_rledbat && tp->t_state < TCPS_ESTABLISHED)) { if (recwin > 0 && tcp_cc_rledbat.get_rlwin != NULL) { /* Min of flow control window and rledbat window */ recwin = imin(recwin, tcp_cc_rledbat.get_rlwin(tp)); } } else 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); } if (!(so->so_flags & SOF_MP_SUBFLOW)) { if (recwin < (int32_t)(tp->rcv_adv - tp->rcv_nxt)) { recwin = (int32_t)(tp->rcv_adv - tp->rcv_nxt); } } else { struct mptcb *mp_tp = tptomptp(tp); int64_t recwin_announced = (int64_t)(mp_tp->mpt_rcvadv - mp_tp->mpt_rcvnxt); /* Don't remove what we announced at the MPTCP-layer */ VERIFY(recwin_announced < INT32_MAX && recwin_announced > INT32_MIN); if (recwin < (int32_t)recwin_announced) { recwin = (int32_t)recwin_announced; } } /* * 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 (tp->t_flagsext & TF_FORCE) { goto send; } if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { goto send; } if (sack_rxmit) { goto send; } /* * If this here is the first segment after SYN/ACK and TFO * is being used, then we always send it, regardless of Nagle,... */ if (tp->t_state == TCPS_SYN_RECEIVED && tfo_enabled(tp) && (tp->t_tfo_flags & TFO_F_COOKIE_VALID) && tp->snd_nxt == tp->iss + 1) { 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 (off + len == tp->snd_wnd) { /* We are limited by the receiver's window... */ if (tp->t_rcvwnd_limited_start_time == 0) { tp->t_rcvwnd_limited_start_time = net_uptime_us(); } } else { /* We are no more limited by the receiver's window... */ if (tp->t_rcvwnd_limited_start_time != 0) { uint64_t now = net_uptime_us(); ASSERT(now >= tp->t_rcvwnd_limited_start_time); tp->t_rcvwnd_limited_total_time += (now - tp->t_rcvwnd_limited_start_time); tp->t_rcvwnd_limited_start_time = 0; } } 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 || /* * 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; } } else { tcpstat.tcps_fcholdpacket++; } } if (recwin > 0) { /* * "adv" is the amount we can increase the window, * taking into account that we are limited by * 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); if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { oldwin = tp->rcv_adv - tp->rcv_nxt; } if (tcp_ack_strategy == TCP_ACK_STRATEGY_LEGACY) { 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 there is more data to read, don't send an ACK. * Otherwise we will end up sending many ACKs if the * application is doing micro-reads. */ if (!(tp->t_flags & TF_STRETCHACK) && (tp->last_ack_sent != tp->rcv_nxt || ((oldwin + adv) >> tp->rcv_scale) > (oldwin >> tp->rcv_scale))) { goto send; } } } else { if (adv >= (int32_t) (2 * tp->t_maxseg)) { /* * ACK every second full-sized segment, if the * ACK is advancing or the window becomes bigger */ if (so->so_rcv.sb_cc < so->so_rcv.sb_lowat && (tp->last_ack_sent != tp->rcv_nxt || ((oldwin + adv) >> tp->rcv_scale) > (oldwin >> tp->rcv_scale))) { goto send; } } else if (tp->t_flags & TF_DELACK) { /* * If we delayed the ACK and the window * is not advancing by a lot (< 2MSS), ACK * immediately if the last incoming packet had * the push flag set and we emptied the buffer. * * This takes care of a sender doing small * repeated writes with Nagle enabled. */ if (so->so_rcv.sb_cc == 0 && tp->last_ack_sent != tp->rcv_nxt && (tp->t_flagsext & TF_LAST_IS_PSH)) { 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 (tcp_ack_strategy == TCP_ACK_STRATEGY_LEGACY && (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); } } /* * 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) { if (tp->t_forced_acks > 0) { tp->t_forced_acks--; } goto send; } if ((flags & TH_RST) || (flags & TH_SYN)) { 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 * and we have not yet done so, then we need to send. */ if ((flags & TH_FIN) && (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una)) { 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 * updates. The three ``states'' for the output side are: * idle not doing retransmits or persists * persisting to move a small or zero window * (re)transmitting and thereby not persisting * * tp->t_timer[TCPT_PERSIST] * is set when we are in persist state. * tp->t_force * is set when we are called to send a persist packet. * tp->t_timer[TCPT_REXMT] * is set when we are retransmitting * The output side is idle when both timers are zero. * * If send window is too small, there is data to transmit, and no * retransmit or persist is pending, then go to persist state. * If nothing happens soon, send when timer expires: * if window is nonzero, transmit what we can, * otherwise force out a byte. */ if (so->so_snd.sb_cc && tp->t_timer[TCPT_REXMT] == 0 && tp->t_timer[TCPT_PERSIST] == 0) { TCP_RESET_REXMT_STATE(tp); tcp_setpersist(tp); } 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)), isipv6); } /* 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: /* * Set TF_MAXSEGSNT flag if the segment size is greater than * the max segment size. */ if (len > 0) { do_not_compress = TRUE; if (len >= tp->t_maxseg) { tp->t_flags |= TF_MAXSEGSNT; } else { tp->t_flags &= ~TF_MAXSEGSNT; } } /* * If we are connected and no segment has been ACKed or SACKed yet and we * hit a retransmission timeout, then we should disable AccECN option * for the rest of the connection. */ if (TCP_ACC_ECN_ON(tp) && tp->t_state == TCPS_ESTABLISHED && tp->snd_una == tp->iss + 1 && (tp->snd_fack == 0) && tp->t_rxtshift > 0) { if ((tp->ecn_flags & TE_RETRY_WITHOUT_ACO) == 0) { tp->ecn_flags |= TE_RETRY_WITHOUT_ACO; } } /* * 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 <= MCLBYTES */ optlen = 0; if (isipv6) { hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); } else { hdrlen = sizeof(struct tcpiphdr); } if (flags & TH_SYN) { tp->snd_nxt = tp->iss; if ((tp->t_flags & TF_NOOPT) == 0) { u_short mss; opt[0] = TCPOPT_MAXSEG; opt[1] = TCPOLEN_MAXSEG; 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))) { *((u_int32_t *)(void *)(opt + optlen)) = htonl( TCPOPT_NOP << 24 | TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | tp->request_r_scale); optlen += 4; } #if MPTCP if (mptcp_enable && (so->so_flags & SOF_MP_SUBFLOW)) { optlen = mptcp_setup_syn_opts(so, opt, optlen); } #endif /* MPTCP */ } } /* * Send a timestamp and echo-reply if this is a SYN and our side * wants to use timestamps (TF_REQ_TSTMP is set) or both our side * and our peer have sent timestamps in our SYN's. */ if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && (flags & TH_RST) == 0 && ((flags & TH_ACK) == 0 || (tp->t_flags & TF_RCVD_TSTMP))) { 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); *lp++ = htonl(tcp_now + tp->t_ts_offset); *lp = htonl(tp->ts_recent); optlen += TCPOLEN_TSTAMP_APPA; } 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. */ /* * 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. */ 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) { /* * 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. */ 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, &mptcp_acknow, &do_not_compress); 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); } if (tfo_enabled(tp) && (flags & (TH_SYN | TH_ACK)) == (TH_SYN | TH_ACK) && (tp->t_tfo_flags & TFO_F_OFFER_COOKIE)) { optlen += tcp_tfo_write_cookie_rep(tp, optlen, opt); } if (SACK_ENABLED(tp) && ((tp->t_flags & TF_NOOPT) == 0)) { /* * 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). */ if (TCPS_HAVEESTABLISHED(tp->t_state) && (tp->t_flags & TF_SACK_PERMIT) && (tp->rcv_numsacks > 0 || TCP_SEND_DSACK_OPT(tp)) && MAX_TCPOPTLEN - optlen >= TCPOLEN_SACK + 2) { unsigned int sackoptlen = 0; 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 + (TCP_SEND_DSACK_OPT(tp) ? 1 : 0))); sackoptlen = (2 + nsack * TCPOLEN_SACK); VERIFY(sackoptlen < UINT8_MAX); /* * 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++ = (uint8_t)sackoptlen; lp = (u_int32_t *)(void *)bp; /* * First block of SACK option should represent * DSACK. Prefer to send SACK information if there * is space for only one SACK block. This will * allow for faster recovery. */ if (TCP_SEND_DSACK_OPT(tp) && nsack > 0 && (tp->rcv_numsacks == 0 || nsack > 1)) { *lp++ = htonl(tp->t_dsack_lseq); *lp++ = htonl(tp->t_dsack_rseq); tcpstat.tcps_dsack_sent++; tp->t_dsack_sent++; nsack--; } VERIFY(nsack == 0 || tp->rcv_numsacks >= nsack); for (i = 0; i < nsack; i++) { struct sackblk sack = tp->sackblks[i]; *lp++ = htonl(sack.start); *lp++ = htonl(sack.end); } optlen += sackoptlen; /* Make sure we didn't write too much */ VERIFY((u_char *)lp - opt <= MAX_TCPOPTLEN); } } /* * AccECN option - after SACK * Don't send on , * send only on before ACCECN is negotiated or * when doing an AccECN session. Don't send AccECN option * if retransmitting a SYN-ACK or a data segment */ if ((TCP_ACC_ECN_ON(tp) || (TCP_ACC_ECN_ENABLED(tp) && (flags & (TH_SYN | TH_ACK)) == (TH_SYN | TH_ACK))) && ((tp->ecn_flags & TE_RETRY_WITHOUT_ACO) == 0)) { uint32_t *lp = (uint32_t *)(void *)(opt + optlen); /* lp will become outdated after options are added */ tcp_add_accecn_option(tp, flags, lp, (uint8_t *)&optlen); } /* 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--; } } /* * For Accurate ECN, send ACE flag based on r.cep, if * We have completed handshake and are in ESTABLISHED state, and * This is not the final ACK of 3WHS. */ if (TCP_ACC_ECN_ON(tp) && TCPS_HAVEESTABLISHED(tp->t_state) && (tp->ecn_flags & TE_ACE_FINAL_ACK_3WHS) == 0) { uint8_t ace = tp->t_rcv_ce_packets & TCP_ACE_MASK; if (ace & 0x01) { flags |= TH_ECE; } else { flags &= ~TH_ECE; } if (ace & 0x02) { flags |= TH_CWR; } else { flags &= ~TH_CWR; } if (ace & 0x04) { flags |= TH_AE; } else { flags &= ~TH_AE; } } /* * 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 packet * * For a SYN-ACK, send an ECN setup SYN-ACK * * Below we send ECN for three different handhshake states: * 1. Server received SYN and is sending a SYN-ACK (state->TCPS_SYN_RECEIVED) * - both classic and Accurate ECN have special encoding * 2. Client is sending SYN packet (state->SYN_SENT) * - both classic and Accurate ECN have special encoding * 3. Client is sending final ACK of 3WHS (state->ESTABLISHED) * - Only Accurate ECN has special encoding */ if ((flags & (TH_SYN | TH_ACK)) == (TH_SYN | TH_ACK) && (tp->ecn_flags & TE_ENABLE_ECN)) { /* Server received either legacy or Accurate ECN setup SYN */ if (tp->ecn_flags & (TE_SETUPRECEIVED | TE_ACE_SETUPRECEIVED)) { if (tcp_send_ecn_flags_on_syn(tp)) { if (TCP_ACC_ECN_ENABLED(tp) && (tp->ecn_flags & TE_ACE_SETUPRECEIVED)) { /* * Accurate ECN mode is on. Initialize packet and byte counters * for the server sending SYN-ACK. Although s_cep will be initialized * during input processing of ACK of SYN-ACK, initialize here as well * in case ACK gets lost. * * Non-zero initial values are used to * support a stateless handshake (see * Section 5.1 of AccECN draft) and to be * distinct from cases where the fields * are incorrectly zeroed. */ tp->t_rcv_ce_packets = 5; tp->t_snd_ce_packets = 5; /* Initialize CE byte counter to 0 */ tp->t_rcv_ce_bytes = tp->t_snd_ce_bytes = 0; if (tp->ecn_flags & TE_ACE_SETUP_NON_ECT) { tp->t_prev_ace_flags = TH_CWR; flags |= tp->t_prev_ace_flags; /* Remove the setup flag as it is also used for final ACK */ tp->ecn_flags &= ~TE_ACE_SETUP_NON_ECT; tcpstat.tcps_ecn_ace_syn_not_ect++; } else if (tp->ecn_flags & TE_ACE_SETUP_ECT1) { tp->t_prev_ace_flags = (TH_CWR | TH_ECE); flags |= tp->t_prev_ace_flags; tp->ecn_flags &= ~TE_ACE_SETUP_ECT1; tcpstat.tcps_ecn_ace_syn_ect1++; } else if (tp->ecn_flags & TE_ACE_SETUP_ECT0) { tp->t_prev_ace_flags = TH_AE; flags |= tp->t_prev_ace_flags; tp->ecn_flags &= ~TE_ACE_SETUP_ECT0; tcpstat.tcps_ecn_ace_syn_ect0++; } else if (tp->ecn_flags & TE_ACE_SETUP_CE) { tp->t_prev_ace_flags = (TH_AE | TH_CWR); flags |= tp->t_prev_ace_flags; tp->ecn_flags &= ~TE_ACE_SETUP_CE; /* * Receive counter is updated on * all acceptable packets except * CE on SYN packets (SYN=1, ACK=0) */ tcpstat.tcps_ecn_ace_syn_ce++; } else { if (tp->t_prev_ace_flags != 0) { /* Set the flags for retransmitted SYN-ACK same as the previous one */ flags |= tp->t_prev_ace_flags; } else { /* We shouldn't come here */ panic("ECN flags (0x%x) not set correctly", tp->ecn_flags); } } /* * We are not yet committing to send IP ECT packets when * Accurate ECN mode is on */ tp->ecn_flags |= (TE_ACE_SETUPSENT); } else if (tp->ecn_flags & TE_SETUPRECEIVED) { /* * 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); } tcpstat.tcps_ecn_server_setup++; tcpstat.tcps_ecn_server_success++; } else { /* * For classic ECN, we sent an ECN-setup SYN-ACK but it was * dropped. Fallback to non-ECN-setup * SYN-ACK and clear flag to indicate that * we should not send data with IP ECT set * * Pretend we didn't receive an * ECN-setup SYN. * * We already incremented the counter * assuming that the ECN setup will * succeed. Decrementing here * tcps_ecn_server_success to correct it. * * For Accurate ECN, we don't yet remove TE_ACE_SETUPRECEIVED * as the client might have received Accurate ECN SYN-ACK. * We decide Accurate ECN's state on processing last ACK from the client. */ if (tp->ecn_flags & (TE_SETUPSENT | TE_ACE_SETUPSENT)) { tcpstat.tcps_ecn_lost_synack++; tcpstat.tcps_ecn_server_success--; tp->ecn_flags |= TE_LOST_SYNACK; } tp->ecn_flags &= ~(TE_SETUPRECEIVED | TE_SENDIPECT | TE_SENDCWR); } } } else if ((flags & (TH_SYN | TH_ACK)) == TH_SYN && (tp->ecn_flags & TE_ENABLE_ECN)) { if (tcp_send_ecn_flags_on_syn(tp)) { if (TCP_ACC_ECN_ENABLED(tp)) { /* We are negotiating AccECN in SYN */ flags |= TH_ACE; /* * For AccECN, we only set the ECN-setup sent * flag as we are not committing to set ECT yet. */ tp->ecn_flags |= (TE_ACE_SETUPSENT); } else { /* * 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); } tcpstat.tcps_ecn_client_setup++; tp->ecn_flags |= TE_CLIENT_SETUP; } else { /* * We sent an ECN-setup SYN but it was dropped. * Fall back to non-ECN and clear flag indicating * we should send data with IP ECT set. */ if (tp->ecn_flags & (TE_SETUPSENT | TE_ACE_SETUPSENT)) { tcpstat.tcps_ecn_lost_syn++; tp->ecn_flags |= TE_LOST_SYN; } tp->ecn_flags &= ~TE_SENDIPECT; } } else if (TCP_ACC_ECN_ON(tp) && (tp->ecn_flags & TE_ACE_FINAL_ACK_3WHS) && len == 0 && (flags & (TH_FLAGS_ALL)) == TH_ACK) { /* * Client has processed SYN-ACK and moved to ESTABLISHED. * This is the final ACK of 3WHS. If ACC_ECN has been negotiated, * then send the handshake encoding as per Table 3 of Accurate ECN draft. * We are clearing the ACE flags just in case if they were set before. * TODO: if client has to carry data in the 3WHS ACK, then we need to send a pure ACK first */ flags &= ~(TH_AE | TH_CWR | TH_ECE); if (tp->ecn_flags & TE_ACE_SETUP_NON_ECT) { flags |= TH_CWR; tp->ecn_flags &= ~TE_ACE_SETUP_NON_ECT; } else if (tp->ecn_flags & TE_ACE_SETUP_ECT1) { flags |= (TH_CWR | TH_ECE); tp->ecn_flags &= ~TE_ACE_SETUP_ECT1; } else if (tp->ecn_flags & TE_ACE_SETUP_ECT0) { flags |= TH_AE; tp->ecn_flags &= ~TE_ACE_SETUP_ECT0; } else if (tp->ecn_flags & TE_ACE_SETUP_CE) { flags |= (TH_AE | TH_CWR); tp->ecn_flags &= ~TE_ACE_SETUP_CE; } tp->ecn_flags &= ~(TE_ACE_FINAL_ACK_3WHS); } /* * 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; tcpstat.tcps_ecn_sent_ece++; } hdrlen += optlen; /* Reset DSACK sequence numbers */ tp->t_dsack_lseq = 0; tp->t_dsack_rseq = 0; if (isipv6) { ipoptlen = ip6_optlen(inp); } else { if (tp_inp_options) { ipoptlen = tp_inp_options->m_len - offsetof(struct ipoption, ipopt_list); } else { ipoptlen = 0; } } #if IPSEC ipoptlen += ipsec_optlen; #endif /* * Adjust data length if insertion of options will * 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 (tso) { int32_t tso_maxlen; tso_maxlen = tp->tso_max_segment_size ? tp->tso_max_segment_size : TCP_MAXWIN; /* hdrlen includes optlen */ if (len > tso_maxlen - hdrlen) { len = tso_maxlen - hdrlen; sendalot = 1; } else if (tp->t_flags & TF_NEEDFIN) { sendalot = 1; } if (len % (tp->t_maxopd - optlen) != 0) { len = len - (len % (tp->t_maxopd - optlen)); sendalot = 1; } } else { len = tp->t_maxopd - optlen - ipoptlen; sendalot = 1; } } if (max_linkhdr + hdrlen > MCLBYTES) { panic("tcphdr too big"); } /* Check if there is enough data in the send socket * buffer to start measuring bandwidth */ if ((tp->t_flagsext & TF_MEASURESNDBW) != 0 && (tp->t_bwmeas != NULL) && (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); /* * Grab a header mbuf, attaching a copy of data to * be transmitted, and initialize the header from * the template for sends on this connection. */ if (len) { /* Remember what the last head-of-line packet-size was */ if (tp->t_pmtud_lastseg_size == 0 && tp->snd_nxt == tp->snd_una) { ASSERT(len + optlen + ipoptlen <= IP_MAXPACKET); tp->t_pmtud_lastseg_size = (uint16_t)(len + optlen + ipoptlen); } if ((tp->t_flagsext & TF_FORCE) && len == 1) { tcpstat.tcps_sndprobe++; } else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 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, wired, txpackets, 1); INP_ADD_STAT(inp, cell, wifi, wired, txbytes, len); tp->t_stat.txretransmitbytes += len; tp->t_stat.rxmitpkts++; } if (tp->ecn_flags & TE_SENDIPECT) { tp->t_ecn_capable_packets_lost++; } } 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); } if (tp->ecn_flags & TE_SENDIPECT) { tp->t_ecn_capable_packets_sent++; } inp_decr_sndbytes_unsent(so, len); } inp_set_activity_bitmap(inp); #if MPTCP if (tp->t_mpflags & TMPF_MPTCP_TRUE) { tcpstat.tcps_mp_sndpacks++; tcpstat.tcps_mp_sndbytes += len; } #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 * 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 = NULL; /* minimum length we are going to allocate */ allocated_len = MHLEN; 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; } m->m_data += max_linkhdr; m->m_len = hdrlen; allocated_len = MCLBYTES; } 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 { 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 (so->so_flags & SOF_MP_SUBFLOW) { copymode = M_COPYM_NOOP_HDR; } #endif /* MPTCP */ if (m != NULL) { if (so->so_snd.sb_flags & SB_SENDHEAD) { VERIFY(so->so_snd.sb_flags & SB_SENDHEAD); VERIFY(so->so_snd.sb_sendoff <= so->so_snd.sb_cc); m->m_next = m_copym_mode(so->so_snd.sb_mb, off, (int)len, M_DONTWAIT, &so->so_snd.sb_sendhead, &so->so_snd.sb_sendoff, copymode); VERIFY(so->so_snd.sb_sendoff <= so->so_snd.sb_cc); } else { m->m_next = m_copym_mode(so->so_snd.sb_mb, off, (int)len, M_DONTWAIT, NULL, NULL, copymode); } if (m->m_next == NULL) { (void) m_free(m); error = ENOBUFS; goto out; } } else { /* * make sure we still have data left * to be sent at this point */ if (so->so_snd.sb_mb == 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 (so->so_snd.sb_flags & SB_SENDHEAD) { VERIFY(so->so_snd.sb_flags & SB_SENDHEAD); VERIFY(so->so_snd.sb_sendoff <= so->so_snd.sb_cc); m = m_copym_with_hdrs(so->so_snd.sb_mb, off, len, M_DONTWAIT, &so->so_snd.sb_sendhead, &so->so_snd.sb_sendoff, copymode); VERIFY(so->so_snd.sb_sendoff <= so->so_snd.sb_cc); } else { m = m_copym_with_hdrs(so->so_snd.sb_mb, off, len, M_DONTWAIT, NULL, NULL, copymode); } if (m == NULL) { error = ENOBUFS; goto out; } m->m_data += max_linkhdr; m->m_len = hdrlen; } } /* * If we're sending everything we've got, set PUSH. * (This will keep happy those implementations which only * give data to the user when a buffer fills or * a PUSH comes in.) * * On SYN-segments we should not add the PUSH-flag. */ if (off + len == so->so_snd.sb_cc && !(flags & TH_SYN)) { flags |= TH_PUSH; } } else { if (tp->t_flags & TF_ACKNOW) { tcpstat.tcps_sndacks++; } else if (flags & (TH_SYN | TH_FIN | TH_RST)) { tcpstat.tcps_sndctrl++; } else if (SEQ_GT(tp->snd_up, tp->snd_una)) { tcpstat.tcps_sndurg++; } else { tcpstat.tcps_sndwinup++; } MGETHDR(m, M_DONTWAIT, MT_HEADER); /* MAC-OK */ if (m == NULL) { error = ENOBUFS; goto out; } 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_pkthdr.rcvif = 0; m_add_crumb(m, PKT_CRUMB_TCP_OUTPUT); /* Any flag other than pure-ACK: Do not compress! */ if (flags & ~(TH_ACK)) { do_not_compress = TRUE; } if (tp->rcv_scale == 0) { do_not_compress = TRUE; } if (do_not_compress) { m->m_pkthdr.comp_gencnt = 0; } else { if (TSTMP_LT(tp->t_comp_lastinc + tcp_ack_compression_rate, tcp_now)) { tp->t_comp_gencnt++; /* 0 means no compression, thus jump this */ if (tp->t_comp_gencnt <= TCP_ACK_COMPRESSION_DUMMY) { tp->t_comp_gencnt = TCP_ACK_COMPRESSION_DUMMY + 1; } tp->t_comp_lastinc = tcp_now; } m->m_pkthdr.comp_gencnt = tp->t_comp_gencnt; } if (isipv6) { ip6 = mtod(m, struct ip6_hdr *); th = (struct tcphdr *)(void *)(ip6 + 1); tcp_fillheaders(m, 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; #if PF_ECN m_pftag(m)->pftag_hdr = (void *)ip6; m_pftag(m)->pftag_flags |= PF_TAG_HDR_INET6; #endif /* PF_ECN */ } else { ip = mtod(m, struct ip *); th = (struct tcphdr *)(void *)(ip + 1); /* this picks up the pseudo header (w/o the length) */ tcp_fillheaders(m, tp, ip, th); if ((tp->ecn_flags & TE_SENDIPECT) != 0 && len && !SEQ_LT(tp->snd_nxt, tp->snd_max) && !sack_rxmit && !(flags & TH_SYN)) { ip->ip_tos |= IPTOS_ECN_ECT0; } #if PF_ECN m_pftag(m)->pftag_hdr = (void *)ip; m_pftag(m)->pftag_flags |= PF_TAG_HDR_INET; #endif /* PF_ECN */ } /* * 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) && tp->snd_nxt == tp->snd_max) { tp->snd_nxt--; } /* * If we are doing retransmissions, then snd_nxt will * not reflect the first unsent octet. For ACK only * packets, we do not want the sequence number of the * retransmitted packet, we want the sequence number * of the next unsent octet. So, if there is no data * (and no SYN or FIN), use snd_max instead of snd_nxt * when filling in ti_seq. But if we are in persist * state, snd_max might reflect one byte beyond the * right edge of the window, so use snd_nxt in that * case, since we know we aren't doing a retransmission. * (retransmit and persist are mutually exclusive...) * * Note the state of this retransmit segment to detect spurious * retransmissions. */ if (sack_rxmit == 0) { 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 && !(tp->t_flagsext & TF_SENT_TLPROBE)) { tcp_rxtseg_insert(tp, tp->snd_nxt, (tp->snd_nxt + len - 1)); } if (len > 0) { m->m_pkthdr.pkt_flags |= PKTF_TCP_REXMT; } } } else { th->th_seq = htonl(tp->snd_max); } } 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; } 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; } /* Separate AE from flags */ th->th_flags = (flags & (TH_FLAGS_ALL)); th->th_x2 = (flags & (TH_AE)) >> 8; th->th_win = htons((u_short) (recwin >> tp->rcv_scale)); tp->t_last_recwin = recwin; if (!(so->so_flags & SOF_MP_SUBFLOW)) { if (recwin > 0 && SEQ_LT(tp->rcv_adv, tp->rcv_nxt + recwin)) { tp->rcv_adv = tp->rcv_nxt + recwin; } } else { struct mptcb *mp_tp = tptomptp(tp); if (recwin > 0) { tp->rcv_adv = tp->rcv_nxt + recwin; } if (recwin > 0 && MPTCP_SEQ_LT(mp_tp->mpt_rcvadv, mp_tp->mpt_rcvnxt + recwin)) { mp_tp->mpt_rcvadv = mp_tp->mpt_rcvnxt + recwin; } } /* * 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; } else { /* * If no urgent pointer to send, then we pull * the urgent pointer to the left edge of the send window * so that it doesn't drift into the send window on sequence * number wraparound. */ tp->snd_up = tp->snd_una; /* drag it along */ } /* * Put TCP length in extended header, and then * 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 (isipv6) { /* * 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 { 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 (isipv6) { m->m_pkthdr.csum_flags |= CSUM_TSO_IPV6; } else { m->m_pkthdr.csum_flags |= CSUM_TSO_IPV4; } m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; } else { m->m_pkthdr.tso_segsz = 0; } /* * In transmit state, time the transmission and arrange for * the retransmit. In persist state, just set snd_max. */ if (!(tp->t_flagsext & TF_FORCE) || tp->t_timer[TCPT_PERSIST] == 0) { tcp_seq startseq = tp->snd_nxt; /* * Advance snd_nxt over sequence space of this segment. */ if (flags & (TH_SYN | TH_FIN)) { if (flags & TH_SYN) { tp->snd_nxt++; } if ((flags & TH_FIN) && !(tp->t_flags & TF_SENTFIN)) { tp->snd_nxt++; tp->t_flags |= TF_SENTFIN; } } if (sack_rxmit) { goto timer; } if (sack_rescue_rxt == TRUE) { tp->snd_nxt = old_snd_nxt; sack_rescue_rxt = FALSE; tcpstat.tcps_pto_in_recovery++; } else { tp->snd_nxt += len; } 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. */ if (tp->t_rtttime == 0) { tp->t_rtttime = tcp_now; tp->t_rtseq = startseq; tcpstat.tcps_segstimed++; /* update variables related to pipe ack */ tp->t_pipeack_lastuna = tp->snd_una; } } /* * Set retransmit timer if not currently set, * and not doing an ack or a keep-alive probe. */ timer: if (tp->t_timer[TCPT_REXMT] == 0 && ((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_persist_stop = 0; TCP_RESET_REXMT_STATE(tp); } tp->t_timer[TCPT_REXMT] = OFFSET_FROM_START(tp, tp->t_rxtcur); } /* * Set tail loss probe timeout if new data is being * transmitted. This will be supported only when * SACK option is enabled on a connection. * * Every time new data is sent PTO will get reset. */ 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) { uint32_t pto, srtt; if (tcp_do_better_lr) { srtt = tp->t_srtt >> TCP_RTT_SHIFT; pto = 2 * srtt; if ((tp->snd_max - tp->snd_una) <= tp->t_maxseg) { pto += tcp_delack; } else { pto += 2; } } else { /* * Using SRTT alone to set PTO can cause spurious * retransmissions on wireless networks where there * is a lot of variance in RTT. Taking variance * into account will avoid this. */ srtt = tp->t_srtt >> TCP_RTT_SHIFT; pto = ((TCP_REXMTVAL(tp)) * 3) >> 1; pto = max(2 * srtt, pto); if ((tp->snd_max - tp->snd_una) == tp->t_maxseg) { pto = max(pto, (((3 * pto) >> 2) + tcp_delack * 2)); } else { pto = max(10, pto); } } /* if RTO is less than PTO, choose RTO instead */ if (tp->t_rxtcur < pto) { pto = tp->t_rxtcur; } tp->t_timer[TCPT_PTO] = OFFSET_FROM_START(tp, pto); } } 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->t_sndtime = tcp_now; } } #if TCPDEBUG /* * Trace. */ 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 * send to IP level. There should be a better way * to handle ttl and tos; we could keep them in * the template, but need a way to checksum without them. */ /* * m->m_pkthdr.len should have been set before cksum calcuration, * because in6_cksum() need it. */ 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. */ ip6->ip6_hlim = in6_selecthlim(inp, inp->in6p_route.ro_rt ? inp->in6p_route.ro_rt->rt_ifp : NULL); /* Don't set ECT bit if requested by an app */ /* Set ECN bits for testing purposes */ if (tp->ecn_flags & TE_FORCE_ECT1) { ip6->ip6_flow |= htonl(IPTOS_ECN_ECT1 << 20); } else if (tp->ecn_flags & TE_FORCE_ECT0) { ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); } 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 { ASSERT(m->m_pkthdr.len <= IP_MAXPACKET); ip->ip_len = (u_short)m->m_pkthdr.len; ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ /* Don't set ECN bit if requested by an app */ ip->ip_tos |= (inp->inp_ip_tos & ~IPTOS_ECN_MASK); /* Set ECN bits for testing purposes */ if (tp->ecn_flags & TE_FORCE_ECT1) { ip->ip_tos |= IPTOS_ECN_ECT1; } else if (tp->ecn_flags & TE_FORCE_ECT0) { ip->ip_tos |= IPTOS_ECN_ECT0; } 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 (!isipv6) { if (path_mtu_discovery && (tp->t_flags & TF_PMTUD)) { ip->ip_off |= IP_DF; } } #if NECP { necp_kernel_policy_id policy_id; necp_kernel_policy_id skip_policy_id; u_int32_t route_rule_id; u_int32_t pass_flags; if (!necp_socket_is_allowed_to_send_recv(inp, NULL, 0, &policy_id, &route_rule_id, &skip_policy_id, &pass_flags)) { TCP_LOG_DROP_NECP(isipv6 ? (void *)ip6 : (void *)ip, th, tp, true); m_freem(m); error = EHOSTUNREACH; goto out; } necp_mark_packet_from_socket(m, inp, policy_id, route_rule_id, skip_policy_id, pass_flags); if (net_qos_policy_restricted != 0) { necp_socket_update_qos_marking(inp, inp->inp_route.ro_rt, route_rule_id); } } #endif /* NECP */ #if IPSEC if (inp->inp_sp != NULL) { 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; /* * Embed the flow hash in pkt hdr and mark the packet as * capable of flow controlling */ 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 | 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; 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 (len == 0 && (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)); } if ((th->th_flags & TH_SYN) && tp->t_syn_sent < UINT8_MAX) { tp->t_syn_sent++; } if ((th->th_flags & TH_FIN) && tp->t_fin_sent < UINT8_MAX) { tp->t_fin_sent++; } if ((th->th_flags & TH_RST) && tp->t_rst_sent < UINT8_MAX) { tp->t_rst_sent++; } TCP_LOG_TH_FLAGS(isipv6 ? (void *)ip6 : (void *)ip, th, tp, true, inp->inp_last_outifp != NULL ? inp->inp_last_outifp : inp->inp_boundifp); tp->t_pktlist_sentlen += len; tp->t_lastchain++; if (isipv6) { DTRACE_TCP5(send, struct mbuf *, m, struct inpcb *, inp, struct ip6 *, ip6, struct tcpcb *, tp, struct tcphdr *, th); } else { 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 (sendalot == 0 || (tp->t_state != TCPS_ESTABLISHED) || (tp->t_flags & TF_ACKNOW) || (tp->t_flagsext & TF_FORCE) || tp->t_lastchain >= tcp_packet_chaining) { error = 0; 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)), isipv6); 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++; goto again; } 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_flagsext & TF_FORCE) || 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; if (SEQ_LT(p->rxmit, p->start)) { p->rxmit = p->start; } } else { lost = p->rxmit - tp->snd_una; p->rxmit = tp->snd_una; if (SEQ_LT(p->rxmit, p->start)) { p->rxmit = p->start; } } tp->sackhint.sack_bytes_rexmit -= lost; if (tp->sackhint.sack_bytes_rexmit < 0) { tp->sackhint.sack_bytes_rexmit = 0; } } else { if (SEQ_GT((tp->snd_nxt - lost), tp->snd_una)) { tp->snd_nxt -= lost; } else { tp->snd_nxt = tp->snd_una; } } } } out: if (tp->t_pktlist_head != NULL) { m_freem_list(tp->t_pktlist_head); } 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] == 0 && tp->t_timer[TCPT_PERSIST] == 0 && (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; tcp_check_timer_state(tp); KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END, 0, 0, 0, 0, 0); TCP_LOG_OUTPUT(tp, "error ENOBUFS silently handled"); tcp_ccdbg_trace(tp, NULL, TCP_CC_OUTPUT_ERROR); return 0; } 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. */ if (tso) { tp->t_flags &= ~TF_TSO; } tcp_mtudisc(inp, 0); tcp_check_timer_state(tp); TCP_LOG_OUTPUT(tp, "error EMSGSIZE silently handled"); KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END, 0, 0, 0, 0, 0); return 0; } /* * Unless this is due to interface restriction policy, * treat EHOSTUNREACH/ENETDOWN/EADDRNOTAVAIL as a soft error. */ if ((error == EHOSTUNREACH || error == ENETDOWN || error == EADDRNOTAVAIL) && TCPS_HAVERCVDSYN(tp->t_state) && !inp_restricted_send(inp, inp->inp_last_outifp)) { tp->t_softerror = error; TCP_LOG_OUTPUT(tp, "soft error %d silently handled", error); error = 0; } else { TCP_LOG_OUTPUT(tp, "error %d", error); } tcp_check_timer_state(tp); KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END, 0, 0, 0, 0, 0); return error; } 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, boolean_t isipv6) { int error = 0; boolean_t chain; boolean_t unlocked = FALSE; boolean_t ifdenied = FALSE; struct inpcb *inp = tp->t_inpcb; struct ifnet *outif = NULL; bool check_qos_marking_again = (so->so_flags1 & SOF1_QOSMARKING_POLICY_OVERRIDE) ? FALSE : TRUE; union { struct route _ro; struct route_in6 _ro6; } route_u_ = {}; #define ro route_u_._ro #define ro6 route_u_._ro6 union { struct ip_out_args _ipoa; struct ip6_out_args _ip6oa; } out_args_u_ = {}; #define ipoa out_args_u_._ipoa #define ip6oa out_args_u_._ip6oa if (isipv6) { 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; } else { 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; } struct flowadv *adv = (isipv6 ? &ip6oa.ip6oa_flowadv : &ipoa.ipoa_flowadv); /* If socket was bound to an ifindex, tell ip_output about it */ if (inp->inp_flags & INP_BOUND_IF) { if (isipv6) { ip6oa.ip6oa_boundif = inp->inp_boundifp->if_index; ip6oa.ip6oa_flags |= IP6OAF_BOUND_IF; } else { ipoa.ipoa_boundif = inp->inp_boundifp->if_index; ipoa.ipoa_flags |= IPOAF_BOUND_IF; } } else if (!in6_embedded_scope && isipv6 && (IN6_IS_SCOPE_EMBED(&inp->in6p_faddr))) { ip6oa.ip6oa_boundif = inp->inp_fifscope; ip6oa.ip6oa_flags |= IP6OAF_BOUND_IF; } if (INP_NO_CELLULAR(inp)) { if (isipv6) { ip6oa.ip6oa_flags |= IP6OAF_NO_CELLULAR; } else { ipoa.ipoa_flags |= IPOAF_NO_CELLULAR; } } if (INP_NO_EXPENSIVE(inp)) { if (isipv6) { ip6oa.ip6oa_flags |= IP6OAF_NO_EXPENSIVE; } else { ipoa.ipoa_flags |= IPOAF_NO_EXPENSIVE; } } if (INP_NO_CONSTRAINED(inp)) { if (isipv6) { ip6oa.ip6oa_flags |= IP6OAF_NO_CONSTRAINED; } else { ipoa.ipoa_flags |= IPOAF_NO_CONSTRAINED; } } if (INP_AWDL_UNRESTRICTED(inp)) { if (isipv6) { ip6oa.ip6oa_flags |= IP6OAF_AWDL_UNRESTRICTED; } else { ipoa.ipoa_flags |= IPOAF_AWDL_UNRESTRICTED; } } if (INP_INTCOPROC_ALLOWED(inp) && isipv6) { ip6oa.ip6oa_flags |= IP6OAF_INTCOPROC_ALLOWED; } if (INP_MANAGEMENT_ALLOWED(inp)) { if (isipv6) { ip6oa.ip6oa_flags |= IP6OAF_MANAGEMENT_ALLOWED; } else { ipoa.ipoa_flags |= IPOAF_MANAGEMENT_ALLOWED; } } if (isipv6) { ip6oa.ip6oa_sotc = so->so_traffic_class; ip6oa.ip6oa_netsvctype = so->so_netsvctype; ip6oa.qos_marking_gencount = inp->inp_policyresult.results.qos_marking_gencount; } else { ipoa.ipoa_sotc = so->so_traffic_class; ipoa.ipoa_netsvctype = so->so_netsvctype; ipoa.qos_marking_gencount = inp->inp_policyresult.results.qos_marking_gencount; } if ((so->so_flags1 & SOF1_QOSMARKING_ALLOWED)) { if (isipv6) { ip6oa.ip6oa_flags |= IP6OAF_QOSMARKING_ALLOWED; } else { ipoa.ipoa_flags |= IPOAF_QOSMARKING_ALLOWED; } } if (check_qos_marking_again) { if (isipv6) { ip6oa.ip6oa_flags |= IP6OAF_REDO_QOSMARKING_POLICY; } else { ipoa.ipoa_flags |= IPOAF_REDO_QOSMARKING_POLICY; } } if (isipv6) { flags |= IPV6_OUTARGS; } else { flags |= IP_OUTARGS; } /* Copy the cached route and take an extra reference */ if (isipv6) { in6p_route_copyout(inp, &ro6); } else { inp_route_copyout(inp, &ro); } #if (DEBUG || DEVELOPMENT) if ((so->so_flags & SOF_MARK_WAKE_PKT) && pkt != NULL) { so->so_flags &= ~SOF_MARK_WAKE_PKT; pkt->m_pkthdr.pkt_flags |= PKTF_WAKE_PKT; } #endif /* (DEBUG || DEVELOPMENT) */ /* * Make sure ACK/DELACK conditions are cleared before * we unlock the socket. */ tp->last_ack_sent = tp->rcv_nxt; tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); tp->t_timer[TCPT_DELACK] = 0; tp->t_unacksegs = 0; tp->t_unacksegs_ce = 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) && !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 * - 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 ; // 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 (isipv6) { error = ip6_output_list(pkt, cnt, inp->in6p_outputopts, &ro6, flags, NULL, NULL, &ip6oa); ifdenied = (ip6oa.ip6oa_flags & IP6OAF_R_IFDENIED); } else { error = ip_output_list(pkt, cnt, opt, &ro, flags, NULL, &ipoa); ifdenied = (ipoa.ipoa_flags & IPOAF_R_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. Flow control is allowed only if there * is outstanding data. * * 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 && 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, ((adv->code == FADV_FLOW_CONTROLLED) ? TCP_CC_FLOW_CONTROL : TCP_CC_SUSPEND)); if (adv->code == FADV_FLOW_CONTROLLED) { TCP_LOG_OUTPUT(tp, "flow controlled"); } else { TCP_LOG_OUTPUT(tp, "flow suspended"); } } } /* * 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 (inp->inp_sndingprog_waiters > 0) { wakeup(&inp->inp_sndinprog_cnt); } } if (isipv6) { /* * When an NECP IP tunnel policy forces the outbound interface, * ip6_output_list() informs the transport layer what is the actual * outgoing interface */ if (ip6oa.ip6oa_flags & IP6OAF_BOUND_IF) { outif = ifindex2ifnet[ip6oa.ip6oa_boundif]; } else if (ro6.ro_rt != NULL) { outif = ro6.ro_rt->rt_ifp; } } else { if (ro.ro_rt != NULL) { outif = ro.ro_rt->rt_ifp; } } if (check_qos_marking_again) { uint32_t qos_marking_gencount; bool allow_qos_marking; if (isipv6) { qos_marking_gencount = ip6oa.qos_marking_gencount; allow_qos_marking = ip6oa.ip6oa_flags & IP6OAF_QOSMARKING_ALLOWED ? TRUE : FALSE; } else { qos_marking_gencount = ipoa.qos_marking_gencount; allow_qos_marking = ipoa.ipoa_flags & IPOAF_QOSMARKING_ALLOWED ? TRUE : FALSE; } inp->inp_policyresult.results.qos_marking_gencount = qos_marking_gencount; if (allow_qos_marking == TRUE) { inp->inp_socket->so_flags1 |= SOF1_QOSMARKING_ALLOWED; } else { inp->inp_socket->so_flags1 &= ~SOF1_QOSMARKING_ALLOWED; } } if (outif != NULL && outif != inp->inp_last_outifp) { /* Update the send byte count */ if (so->so_snd.sb_cc > 0 && 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 SKYWALK if (NETNS_TOKEN_VALID(&inp->inp_netns_token)) { netns_set_ifnet(&inp->inp_netns_token, inp->inp_last_outifp); } #endif /* SKYWALK */ } if (error != 0 && ifdenied && (INP_NO_CELLULAR(inp) || INP_NO_EXPENSIVE(inp) || INP_NO_CONSTRAINED(inp))) { soevent(so, (SO_FILT_HINT_LOCKED | SO_FILT_HINT_IFDENIED)); } /* Synchronize cached PCB route & options */ if (isipv6) { in6p_route_copyin(inp, &ro6); } else { 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; #undef ro #undef ro6 #undef ipoa #undef ip6oa } int tcptv_persmin_val = TCPTV_PERSMIN; void tcp_setpersist(struct tcpcb *tp) { 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; } /* * Start/restart persistance timer. */ TCPT_RANGESET(tp->t_timer[TCPT_PERSIST], t * tcp_backoff[tp->t_rxtshift], 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) { tp->t_rxtshift++; } } static int tcp_recv_throttle(struct tcpcb *tp) { uint32_t base_rtt, newsize; 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) { /* * if latency increased on a background flow, * return 1 to start throttling. */ 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 > 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; }