/* * Copyright (c) 2006 Apple Computer, Inc. All Rights Reserved. * * @APPLE_LICENSE_OSREFERENCE_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_LICENSE_OSREFERENCE_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 $ */ #define _IP_VHL #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #if INET6 #include #include #include #endif #include #define TCPOUTFLAGS #include #include #include #include #include #if TCPDEBUG #include #endif #include #if IPSEC #include #endif /*IPSEC*/ #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) #ifdef notyet extern struct mbuf *m_copypack(); #endif static int path_mtu_discovery = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, &path_mtu_discovery, 1, "Enable Path MTU Discovery"); int ss_fltsz = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, &ss_fltsz, 1, "Slow start flight size"); int ss_fltsz_local = 4; /* starts with four segments max */ SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW, &ss_fltsz_local, 1, "Slow start flight size for local networks"); int tcp_do_newreno = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, &tcp_do_newreno, 0, "Enable NewReno Algorithms"); int tcp_packet_chaining = 50; SYSCTL_INT(_net_inet_tcp, OID_AUTO, packetchain, CTLFLAG_RW, &tcp_packet_chaining, 0, "Enable TCP output packet chaining"); struct mbuf *m_copym_with_hdrs(struct mbuf*, int, int, int, struct mbuf**, int*); static long packchain_newlist = 0; static long packchain_looped = 0; static long packchain_sent = 0; /* temporary: for testing */ #if IPSEC extern int ipsec_bypass; #endif extern int slowlink_wsize; /* window correction for slow links */ extern u_long route_generation; extern int fw_enable; /* firewall is on: disable packet chaining */ extern int ipsec_bypass; extern vm_size_t so_cache_zone_element_size; static __inline__ u_int16_t get_socket_id(struct socket * s) { u_int16_t val; if (so_cache_zone_element_size == 0) { return (0); } val = (u_int16_t)(((u_int32_t)s) / so_cache_zone_element_size); if (val == 0) { val = 0xffff; } return (val); } /* * Tcp output routine: figure out what should be sent and send it. */ int tcp_output(struct tcpcb *tp) { struct socket *so = tp->t_inpcb->inp_socket; long len, recwin, sendwin; int off, flags, error; register struct mbuf *m; struct ip *ip = NULL; register struct ipovly *ipov = NULL; #if INET6 struct ip6_hdr *ip6 = NULL; #endif /* INET6 */ register struct tcphdr *th; u_char opt[TCP_MAXOLEN]; unsigned ipoptlen, optlen, hdrlen; int idle, sendalot, howmuchsent = 0; int i, sack_rxmit; int sack_bytes_rxmt; struct sackhole *p; int maxburst = TCP_MAXBURST; struct rmxp_tao *taop; struct rmxp_tao tao_noncached; int last_off = 0; int m_off; struct mbuf *m_last = 0; struct mbuf *m_head = 0; struct mbuf *packetlist = 0; struct mbuf *lastpacket = 0; #if INET6 int isipv6 = tp->t_inpcb->inp_vflag & INP_IPV6 ; #endif short packchain_listadd = 0; u_int16_t socket_id = get_socket_id(so); /* * 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); if (idle && tp->t_rcvtime >= tp->t_rxtcur) { /* * We have been idle for "a while" and no acks are * expected to clock out any data we send -- * slow start to get ack "clock" running again. * * Set the slow-start flight size depending on whether * this is a local network or not. */ if ( #if INET6 (isipv6 && in6_localaddr(&tp->t_inpcb->in6p_faddr)) || (!isipv6 && #endif in_localaddr(tp->t_inpcb->inp_faddr) #if INET6 ) #endif ) tp->snd_cwnd = tp->t_maxseg * ss_fltsz_local; else tp->snd_cwnd = tp->t_maxseg * ss_fltsz; } tp->t_flags &= ~TF_LASTIDLE; if (idle) { if (tp->t_flags & TF_MORETOCOME) { tp->t_flags |= TF_LASTIDLE; idle = 0; } } again: KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_START, 0,0,0,0,0); #if INET6 if (isipv6) { KERNEL_DEBUG(DBG_LAYER_BEG, ((tp->t_inpcb->inp_fport << 16) | tp->t_inpcb->inp_lport), (((tp->t_inpcb->in6p_laddr.s6_addr16[0] & 0xffff) << 16) | (tp->t_inpcb->in6p_faddr.s6_addr16[0] & 0xffff)), sendalot,0,0); } else #endif { KERNEL_DEBUG(DBG_LAYER_BEG, ((tp->t_inpcb->inp_fport << 16) | tp->t_inpcb->inp_lport), (((tp->t_inpcb->inp_laddr.s_addr & 0xffff) << 16) | (tp->t_inpcb->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). */ if ((tp->t_inpcb->inp_route.ro_rt != NULL && (tp->t_inpcb->inp_route.ro_rt->generation_id != route_generation)) || (tp->t_inpcb->inp_route.ro_rt == NULL)) { /* check that the source address is still valid */ if (ifa_foraddr(tp->t_inpcb->inp_laddr.s_addr) == 0) { if (tp->t_state >= TCPS_CLOSE_WAIT) { tcp_close(tp); return(EADDRNOTAVAIL); } /* set Retransmit timer if it wasn't set * reset Persist timer and shift register as the * adversed peer window may not be valid anymore */ if (!tp->t_timer[TCPT_REXMT]) { tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; if (tp->t_timer[TCPT_PERSIST]) { tp->t_timer[TCPT_PERSIST] = 0; tp->t_rxtshift = 0; } } if (packetlist) { error = ip_output_list(packetlist, packchain_listadd, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, (so->so_options & SO_DONTROUTE), 0); tp->t_lastchain = 0; } if (so->so_flags & SOF_NOADDRAVAIL) return(EADDRNOTAVAIL); else return(0); /* silently ignore and keep data in socket */ } } } /* * 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 (tp->sack_enable && SEQ_LT(tp->snd_nxt, tp->snd_max)) 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 (tp->sack_enable && IN_FASTRECOVERY(tp) && (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { long cwin; cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; if (cwin < 0) cwin = 0; /* Do not retransmit SACK segments beyond snd_recover */ if (SEQ_GT(p->end, tp->snd_recover)) { /* * (At least) part of sack hole extends beyond * snd_recover. Check to see if we can rexmit data * for this hole. */ if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { /* * Can't rexmit any more data for this hole. * That data will be rexmitted in the next * sack recovery episode, when snd_recover * moves past p->rxmit. */ p = NULL; goto after_sack_rexmit; } else /* Can rexmit part of the current hole */ len = ((long)ulmin(cwin, tp->snd_recover - p->rxmit)); } else len = ((long)ulmin(cwin, p->end - p->rxmit)); off = p->rxmit - tp->snd_una; if (len > 0) { sack_rxmit = 1; sendalot = 1; tcpstat.tcps_sack_rexmits++; tcpstat.tcps_sack_rexmit_bytes += min(len, tp->t_maxseg); } } 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 (tp->t_flags & TF_NEEDSYN) flags |= TH_SYN; /* * 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_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_rxtshift = 0; } } /* * 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 = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); else { long cwin; /* * We are inside of a SACK recovery episode and are * sending new data, having retransmitted all the * data possible in the scoreboard. */ len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) - off); /* * Don't remove this (len > 0) check ! * We explicitly check for len > 0 here (although it * isn't really necessary), to work around a gcc * optimization issue - to force gcc to compute * len above. Without this check, the computation * of len is bungled by the optimizer. */ if (len > 0) { cwin = tp->snd_cwnd - (tp->snd_nxt - tp->sack_newdata) - sack_bytes_rxmt; if (cwin < 0) cwin = 0; len = lmin(len, cwin); } } } /* * 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)) { flags &= ~TH_SYN; off--, len++; if (len > 0 && tp->t_state == TCPS_SYN_SENT) { if (packetlist) { error = ip_output_list(packetlist, packchain_listadd, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, (so->so_options & SO_DONTROUTE), 0); tp->t_lastchain = 0; } 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. */ if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { len = 0; flags &= ~TH_FIN; } if (len < 0) { /* * 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_rxtshift = 0; tp->snd_nxt = tp->snd_una; if (tp->t_timer[TCPT_PERSIST] == 0) tcp_setpersist(tp); } } /* * len will be >= 0 after this point. Truncate to the maximum * segment length and ensure that FIN is removed if the length * no longer contains the last data byte. */ if (len > tp->t_maxseg) { len = tp->t_maxseg; howmuchsent += len; sendalot = 1; } 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; } if (tp->t_flags & TF_SLOWLINK && slowlink_wsize > 0 ) /* Clips window size for slow links */ recwin = min(sbspace(&so->so_rcv), slowlink_wsize); else recwin = sbspace(&so->so_rcv); /* * Sender silly window avoidance. We transmit under the following * conditions when len is non-zero: * * - We have a full segment * - This is the last buffer in a write()/send() and we are * either idle or running NODELAY * - we've timed out (e.g. persist timer) * - we have more then 1/2 the maximum send window's worth of * data (receiver may be limited the window size) * - we need to retransmit */ if (len) { if (len == tp->t_maxseg) goto send; if (!(tp->t_flags & TF_MORETOCOME) && (idle || tp->t_flags & TF_NODELAY) && (tp->t_flags & TF_NOPUSH) == 0 && len + off >= so->so_snd.sb_cc) goto send; if (tp->t_force) goto send; if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) goto send; if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ goto send; if (sack_rxmit) goto send; } /* * Compare available window to amount of window * known to peer (as advertised window less * next expected input). If the difference is at least two * max size segments, or at least 50% of the maximum possible * window, then want to send a window update to peer. * Skip this if the connection is in T/TCP half-open state. */ if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN)) { /* * "adv" is the amount we can increase the window, * taking into account that we are limited by * TCP_MAXWIN << tp->rcv_scale. */ long adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) - (tp->rcv_adv - tp->rcv_nxt); if (adv >= (long) (2 * tp->t_maxseg)) goto send; if (2 * adv >= (long) so->so_rcv.sb_hiwat) goto send; } /* * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW * is also a catch-all for the retransmit timer timeout case. */ if (tp->t_flags & TF_ACKNOW) goto send; if ((flags & TH_RST) || ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) goto send; if (SEQ_GT(tp->snd_up, tp->snd_una)) goto send; /* * 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) == 0 || 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 (tp->sack_enable && 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] = 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) { tp->t_rxtshift = 0; 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. */ if (packetlist) { error = ip_output_list(packetlist, packchain_listadd, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, (so->so_options & SO_DONTROUTE), 0); } KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END, 0,0,0,0,0); return (0); send: /* * 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 INET6 if (isipv6) hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); else #endif 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 *)(opt + optlen)) = htonl( TCPOPT_NOP << 24 | TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | tp->request_r_scale); optlen += 4; } } } /* * 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 *)(opt + optlen); /* Form timestamp option as shown in appendix A of RFC 1323. */ *lp++ = htonl(TCPOPT_TSTAMP_HDR); *lp++ = htonl(tcp_now); *lp = htonl(tp->ts_recent); optlen += TCPOLEN_TSTAMP_APPA; } if (tp->sack_enable && ((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; } /* * 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 && MAX_TCPOPTLEN - optlen - 2 >= TCPOLEN_SACK) { int nsack, sackoptlen, padlen; u_char *bp = (u_char *)opt + optlen; u_int32_t *lp; nsack = (MAX_TCPOPTLEN - optlen - 2) / TCPOLEN_SACK; nsack = min(nsack, tp->rcv_numsacks); sackoptlen = (2 + nsack * TCPOLEN_SACK); /* * First we need to pad options so that the * SACK blocks can start at a 4-byte boundary * (sack option and length are at a 2 byte offset). */ padlen = (MAX_TCPOPTLEN - optlen - sackoptlen) % 4; optlen += padlen; while (padlen-- > 0) *bp++ = TCPOPT_NOP; tcpstat.tcps_sack_send_blocks++; *bp++ = TCPOPT_SACK; *bp++ = sackoptlen; lp = (u_int32_t *)bp; for (i = 0; i < nsack; i++) { struct sackblk sack = tp->sackblks[i]; *lp++ = htonl(sack.start); *lp++ = htonl(sack.end); } optlen += sackoptlen; } } /* Pad TCP options to a 4 byte boundary */ if (optlen < MAX_TCPOPTLEN && (optlen % sizeof(u_int32_t))) { int pad = sizeof(u_int32_t) - (optlen % sizeof(u_int32_t)); u_char *bp = (u_char *)opt + optlen; optlen += pad; while (pad) { *bp++ = TCPOPT_EOL; pad--; } } hdrlen += optlen; #if INET6 if (isipv6) ipoptlen = ip6_optlen(tp->t_inpcb); else #endif { if (tp->t_inpcb->inp_options) { ipoptlen = tp->t_inpcb->inp_options->m_len - offsetof(struct ipoption, ipopt_list); } else ipoptlen = 0; } #if IPSEC if (ipsec_bypass == 0) ipoptlen += ipsec_hdrsiz_tcp(tp); #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. */ if (len + optlen + ipoptlen > tp->t_maxopd) { /* * If there is still more to send, don't close the connection. */ flags &= ~TH_FIN; len = tp->t_maxopd - optlen - ipoptlen; howmuchsent += len; sendalot = 1; } /*#ifdef DIAGNOSTIC*/ #if INET6 if (max_linkhdr + hdrlen > MCLBYTES) panic("tcphdr too big"); #else if (max_linkhdr + hdrlen > MHLEN) panic("tcphdr too big"); #endif /*#endif*/ /* * 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) { if (tp->t_force && len == 1) tcpstat.tcps_sndprobe++; else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { tcpstat.tcps_sndrexmitpack++; tcpstat.tcps_sndrexmitbyte += len; } else { tcpstat.tcps_sndpack++; tcpstat.tcps_sndbyte += len; } #ifdef notyet if ((m = m_copypack(so->so_snd.sb_mb, off, (int)len, max_linkhdr + hdrlen)) == 0) { error = ENOBUFS; goto out; } /* * m_copypack left space for our hdr; use it. */ m->m_len += hdrlen; m->m_data -= hdrlen; #else /* * 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; #if INET6 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; } #endif if (len <= MHLEN - hdrlen - max_linkhdr) { if (m == NULL) { 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 == -1) { 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 { if (m != NULL) { m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); if (m->m_next == 0) { (void) m_free(m); error = ENOBUFS; goto out; } } else { /* * determine whether the mbuf pointer and offset passed back by the 'last' call * to m_copym_with_hdrs are still valid... if the head of the socket chain has * changed (due to an incoming ACK for instance), or the offset into the chain we * just computed is different from the one last returned by m_copym_with_hdrs (perhaps * we're re-transmitting a packet sent earlier), than we can't pass the mbuf pointer and * offset into it as valid hints for m_copym_with_hdrs to use (if valid, these hints allow * m_copym_with_hdrs to avoid rescanning from the beginning of the socket buffer mbuf list. * setting the mbuf pointer to NULL is sufficient to disable the hint mechanism. */ if (m_head != so->so_snd.sb_mb || last_off != off) m_last = NULL; last_off = off + len; m_head = so->so_snd.sb_mb; /* makes sure we still have data left to be sent at this point */ if (m_head == NULL) { error = 0; /* should we return an error? */ goto out; } /* * m_copym_with_hdrs will always return the last mbuf pointer and the offset into it that * it acted on to fullfill the current request, whether a valid 'hint' was passed in or not */ if ((m = m_copym_with_hdrs(so->so_snd.sb_mb, off, (int) len, M_DONTWAIT, &m_last, &m_off)) == NULL) { error = ENOBUFS; goto out; } m->m_data += max_linkhdr; m->m_len = hdrlen; } } #endif /* * If we're sending everything we've got, set PUSH. * (This will keep happy those implementations which only * give data to the user when a buffer fills or * a PUSH comes in.) */ if (off + len == so->so_snd.sb_cc) 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); if (m == NULL) { error = ENOBUFS; goto out; } #if INET6 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && MHLEN >= hdrlen) { MH_ALIGN(m, hdrlen); } else #endif m->m_data += max_linkhdr; m->m_len = hdrlen; } m->m_pkthdr.rcvif = 0; #if INET6 if (isipv6) { ip6 = mtod(m, struct ip6_hdr *); th = (struct tcphdr *)(ip6 + 1); tcp_fillheaders(tp, ip6, th); } else #endif /* INET6 */ { ip = mtod(m, struct ip *); ipov = (struct ipovly *)ip; th = (struct tcphdr *)(ip + 1); /* this picks up the pseudo header (w/o the length) */ tcp_fillheaders(tp, ip, th); } /* * 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...) */ if (sack_rxmit == 0) { if (len || (flags & (TH_SYN|TH_FIN)) || tp->t_timer[TCPT_PERSIST]) th->th_seq = htonl(tp->snd_nxt); else th->th_seq = htonl(tp->snd_max); } else { th->th_seq = htonl(p->rxmit); p->rxmit += len; tp->sackhint.sack_bytes_rexmit += len; } th->th_ack = htonl(tp->rcv_nxt); if (optlen) { bcopy(opt, th + 1, optlen); th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; } th->th_flags = flags; /* * Calculate receive window. Don't shrink window, * but avoid silly window syndrome. */ if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && recwin < (long)tp->t_maxseg) recwin = 0; if (recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) recwin = (long)(tp->rcv_adv - tp->rcv_nxt); if (tp->t_flags & TF_SLOWLINK && slowlink_wsize > 0) { if (recwin > (long)slowlink_wsize) recwin = slowlink_wsize; th->th_win = htons((u_short) (recwin>>tp->rcv_scale)); } else { if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) recwin = (long)TCP_MAXWIN << tp->rcv_scale; th->th_win = htons((u_short) (recwin>>tp->rcv_scale)); } /* * Adjust the RXWIN0SENT flag - indicate that we have advertised * a 0 window. This may cause the remote transmitter to stall. This * flag tells soreceive() to disable delayed acknowledgements when * draining the buffer. This can occur if the receiver is attempting * to read more data then can be buffered prior to transmitting on * the connection. */ if (recwin == 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 INET6 if (isipv6) /* * ip6_plen is not need to be filled now, and will be filled * in ip6_output. */ th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), sizeof(struct tcphdr) + optlen + len); else #endif /* INET6 */ { 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))); } /* * In transmit state, time the transmission and arrange for * the retransmit. In persist state, just set snd_max. */ if (tp->t_force == 0 || 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->snd_nxt++; tp->t_flags |= TF_SENTFIN; } } if (sack_rxmit) goto timer; tp->snd_nxt += len; if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { tp->snd_max = tp->snd_nxt; /* * Time this transmission if not a retransmission and * not currently timing anything. */ if (tp->t_rtttime == 0) { tp->t_rtttime = 1; tp->t_rtseq = startseq; tcpstat.tcps_segstimed++; } } /* * Set retransmit timer if not currently set, * and not doing an ack or a keep-alive probe. * Initial value for retransmit timer is smoothed * round-trip time + 2 * round-trip time variance. * Initialize shift counter which is used for backoff * of retransmit time. */ timer: if (tp->t_timer[TCPT_REXMT] == 0 && ((sack_rxmit && tp->snd_nxt != tp->snd_max) || tp->snd_nxt != tp->snd_una)) { if (tp->t_timer[TCPT_PERSIST]) { tp->t_timer[TCPT_PERSIST] = 0; tp->t_rxtshift = 0; } tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; } } 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) { ++xlen; tp->t_flags |= TF_SENTFIN; } if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) tp->snd_max = tp->snd_nxt + len; } #if TCPDEBUG /* * Trace. */ if (so->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 INET6 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(tp->t_inpcb, tp->t_inpcb->in6p_route.ro_rt ? tp->t_inpcb->in6p_route.ro_rt->rt_ifp : NULL); /* TODO: IPv6 IP6TOS_ECT bit on */ #if IPSEC if (ipsec_bypass == 0 && ipsec_setsocket(m, so) != 0) { m_freem(m); error = ENOBUFS; goto out; } #endif /*IPSEC*/ m->m_pkthdr.socket_id = socket_id; error = ip6_output(m, tp->t_inpcb->in6p_outputopts, &tp->t_inpcb->in6p_route, (so->so_options & SO_DONTROUTE), NULL, NULL, 0); } else #endif /* INET6 */ { struct rtentry *rt; ip->ip_len = m->m_pkthdr.len; #if INET6 if (isipv6) ip->ip_ttl = in6_selecthlim(tp->t_inpcb, tp->t_inpcb->in6p_route.ro_rt ? tp->t_inpcb->in6p_route.ro_rt->rt_ifp : NULL); else #endif /* INET6 */ ip->ip_ttl = tp->t_inpcb->inp_ip_ttl; /* XXX */ ip->ip_tos = tp->t_inpcb->inp_ip_tos; /* XXX */ #if INET6 if (isipv6) { KERNEL_DEBUG(DBG_LAYER_BEG, ((tp->t_inpcb->inp_fport << 16) | tp->t_inpcb->inp_lport), (((tp->t_inpcb->in6p_laddr.s6_addr16[0] & 0xffff) << 16) | (tp->t_inpcb->in6p_faddr.s6_addr16[0] & 0xffff)), 0,0,0); } else #endif { KERNEL_DEBUG(DBG_LAYER_BEG, ((tp->t_inpcb->inp_fport << 16) | tp->t_inpcb->inp_lport), (((tp->t_inpcb->inp_laddr.s_addr & 0xffff) << 16) | (tp->t_inpcb->inp_faddr.s_addr & 0xffff)), 0,0,0); } /* * See if we should do MTU discovery. We do it only if the following * are true: * 1) we have a valid route to the destination * 2) the MTU is not locked (if it is, then discovery has been * disabled) */ if (path_mtu_discovery && (rt = tp->t_inpcb->inp_route.ro_rt) && rt->rt_flags & RTF_UP && !(rt->rt_rmx.rmx_locks & RTV_MTU)) { ip->ip_off |= IP_DF; } #if IPSEC if (ipsec_bypass == 0) ipsec_setsocket(m, so); #endif /*IPSEC*/ /* * The socket is kept locked while sending out packets in ip_output, even if packet chaining is not active. */ m->m_pkthdr.socket_id = socket_id; if (packetlist) { m->m_nextpkt = NULL; lastpacket->m_nextpkt = m; lastpacket = m; packchain_listadd++; } else { m->m_nextpkt = NULL; packchain_newlist++; packetlist = lastpacket = m; packchain_listadd=0; } if ((ipsec_bypass == 0) || fw_enable || sendalot == 0 || (tp->t_state != TCPS_ESTABLISHED) || (tp->snd_cwnd <= (tp->snd_wnd / 4)) || (tp->t_flags & (TH_PUSH | TF_ACKNOW)) || tp->t_force != 0 || packchain_listadd >= tcp_packet_chaining) { lastpacket->m_nextpkt = 0; error = ip_output_list(packetlist, packchain_listadd, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, (so->so_options & SO_DONTROUTE), 0); tp->t_lastchain = packchain_listadd; packchain_sent++; packetlist = NULL; if (error == 0) howmuchsent = 0; } else { error = 0; packchain_looped++; tcpstat.tcps_sndtotal++; if (recwin > 0 && SEQ_GT(tp->rcv_nxt+recwin, tp->rcv_adv)) tp->rcv_adv = tp->rcv_nxt + recwin; tp->last_ack_sent = tp->rcv_nxt; tp->t_flags &= ~(TF_ACKNOW|TF_DELACK); goto again; } } if (error) { /* * We know that the packet was lost, so back out the * sequence number advance, if any. */ if (tp->t_force == 0 || tp->t_timer[TCPT_PERSIST] == 0) { /* * No need to check for TH_FIN here because * the TF_SENTFIN flag handles that case. */ if ((flags & TH_SYN) == 0) { if (sack_rxmit) { p->rxmit -= howmuchsent; tp->sackhint.sack_bytes_rexmit -= howmuchsent; } else tp->snd_nxt -= howmuchsent; } } howmuchsent = 0; out: if (error == ENOBUFS) { if (!tp->t_timer[TCPT_REXMT] && !tp->t_timer[TCPT_PERSIST]) tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; tcp_quench(tp->t_inpcb, 0); if (packetlist) m_freem_list(packetlist); tp->t_lastchain = 0; KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END, 0,0,0,0,0); 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. */ tcp_mtudisc(tp->t_inpcb, 0); if (packetlist) m_freem_list(packetlist); tp->t_lastchain = 0; KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END, 0,0,0,0,0); return 0; } if ((error == EHOSTUNREACH || error == ENETDOWN) && TCPS_HAVERCVDSYN(tp->t_state)) { tp->t_softerror = error; if (packetlist) m_freem_list(packetlist); tp->t_lastchain = 0; KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END, 0,0,0,0,0); return (0); } if (packetlist) m_freem_list(packetlist); tp->t_lastchain = 0; KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END, 0,0,0,0,0); return (error); } sentit: tcpstat.tcps_sndtotal++; /* * Data sent (as far as we can tell). * If this advertises a larger window than any other segment, * then remember the size of the advertised window. * Any pending ACK has now been sent. */ if (recwin > 0 && SEQ_GT(tp->rcv_nxt+recwin, tp->rcv_adv)) tp->rcv_adv = tp->rcv_nxt + recwin; tp->last_ack_sent = tp->rcv_nxt; tp->t_flags &= ~(TF_ACKNOW|TF_DELACK); KERNEL_DEBUG(DBG_FNC_TCP_OUTPUT | DBG_FUNC_END,0,0,0,0,0); if (sendalot && (!tcp_do_newreno || --maxburst)) goto again; return (0); } void tcp_setpersist(tp) register struct tcpcb *tp; { int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; if (tp->t_timer[TCPT_REXMT]) panic("tcp_setpersist: retransmit pending"); /* * Start/restart persistance timer. */ TCPT_RANGESET(tp->t_timer[TCPT_PERSIST], t * tcp_backoff[tp->t_rxtshift], TCPTV_PERSMIN, TCPTV_PERSMAX); if (tp->t_rxtshift < TCP_MAXRXTSHIFT) tp->t_rxtshift++; }