static #ifndef GPROF inline #endif int tcp_segsize(struct tcpcb *tp, int *txsegsizep, int *rxsegsizep, bool *alwaysfragp) { #ifdef INET struct inpcb *inp = tp->t_inpcb; #endif #ifdef INET6 struct in6pcb *in6p = tp->t_in6pcb; #endif struct socket *so = NULL; struct rtentry *rt; struct ifnet *ifp; int size; int hdrlen; int optlen; *alwaysfragp = false; #ifdef DIAGNOSTIC if (tp->t_inpcb && tp->t_in6pcb) panic("tcp_segsize: both t_inpcb and t_in6pcb are set"); #endif switch (tp->t_family) { #ifdef INET case AF_INET: hdrlen = sizeof(struct ip) + sizeof(struct tcphdr); break; #endif #ifdef INET6 case AF_INET6: hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); break; #endif default: size = tcp_mssdflt; goto out; } rt = NULL; #ifdef INET if (inp) { rt = in_pcbrtentry(inp); so = inp->inp_socket; } #endif #ifdef INET6 if (in6p) { rt = in6_pcbrtentry(in6p); so = in6p->in6p_socket; } #endif if (rt == NULL) { size = tcp_mssdflt; goto out; } ifp = rt->rt_ifp; size = tcp_mssdflt; if (tp->t_mtudisc && rt->rt_rmx.rmx_mtu != 0) { #ifdef INET6 if (in6p && rt->rt_rmx.rmx_mtu < IPV6_MMTU) { /* * RFC2460 section 5, last paragraph: if path MTU is * smaller than 1280, use 1280 as packet size and * attach fragment header. */ size = IPV6_MMTU - hdrlen - sizeof(struct ip6_frag); *alwaysfragp = true; } else size = rt->rt_rmx.rmx_mtu - hdrlen; #else size = rt->rt_rmx.rmx_mtu - hdrlen; #endif } else if (ifp->if_flags & IFF_LOOPBACK) size = ifp->if_mtu - hdrlen; #ifdef INET else if (inp && tp->t_mtudisc) size = ifp->if_mtu - hdrlen; else if (inp && in_localaddr(inp->inp_faddr)) size = ifp->if_mtu - hdrlen; #endif #ifdef INET6 else if (in6p) { #ifdef INET if (IN6_IS_ADDR_V4MAPPED(&in6p->in6p_faddr)) { /* mapped addr case */ struct in_addr d; bcopy(&in6p->in6p_faddr.s6_addr32[3], &d, sizeof(d)); if (tp->t_mtudisc || in_localaddr(d)) size = ifp->if_mtu - hdrlen; } else #endif { /* * for IPv6, path MTU discovery is always turned on, * or the node must use packet size <= 1280. */ size = tp->t_mtudisc ? IN6_LINKMTU(ifp) : IPV6_MMTU; size -= hdrlen; } } #endif out: /* * Now we must make room for whatever extra TCP/IP options are in * the packet. */ optlen = tcp_optlen(tp); /* * XXX tp->t_ourmss should have the right size, but without this code * fragmentation will occur... need more investigation */ #ifdef INET if (inp) { #if defined(IPSEC) if (ipsec_used && !IPSEC_PCB_SKIP_IPSEC(inp->inp_sp, IPSEC_DIR_OUTBOUND)) optlen += ipsec4_hdrsiz_tcp(tp); #endif optlen += ip_optlen(inp); } #endif #ifdef INET6 #ifdef INET if (in6p && tp->t_family == AF_INET) { #if defined(IPSEC) if (ipsec_used && !IPSEC_PCB_SKIP_IPSEC(in6p->in6p_sp, IPSEC_DIR_OUTBOUND)) optlen += ipsec4_hdrsiz_tcp(tp); #endif /* XXX size -= ip_optlen(in6p); */ } else #endif if (in6p && tp->t_family == AF_INET6) { #if defined(IPSEC) if (ipsec_used && !IPSEC_PCB_SKIP_IPSEC(in6p->in6p_sp, IPSEC_DIR_OUTBOUND)) optlen += ipsec6_hdrsiz_tcp(tp); #endif optlen += ip6_optlen(in6p); } #endif size -= optlen; /* there may not be any room for data if mtu is too small */ if (size < 0) return (EMSGSIZE); /* * *rxsegsizep holds *estimated* inbound segment size (estimation * assumes that path MTU is the same for both ways). this is only * for silly window avoidance, do not use the value for other purposes. * * ipseclen is subtracted from both sides, this may not be right. * I'm not quite sure about this (could someone comment). */ *txsegsizep = min(tp->t_peermss - optlen, size); /* * Never send more than half a buffer full. This insures that we can * always keep 2 packets on the wire, no matter what SO_SNDBUF is, and * therefore acks will never be delayed unless we run out of data to * transmit. */ if (so) *txsegsizep = min(so->so_snd.sb_hiwat >> 1, *txsegsizep); *rxsegsizep = min(tp->t_ourmss - optlen, size); if (*txsegsizep != tp->t_segsz) { /* * If the new segment size is larger, we don't want to * mess up the congestion window, but if it is smaller * we'll have to reduce the congestion window to ensure * that we don't get into trouble with initial windows * and the rest. In any case, if the segment size * has changed, chances are the path has, too, and * our congestion window will be different. */ if (*txsegsizep < tp->t_segsz) { tp->snd_cwnd = max((tp->snd_cwnd / tp->t_segsz) * *txsegsizep, *txsegsizep); tp->snd_ssthresh = max((tp->snd_ssthresh / tp->t_segsz) * *txsegsizep, *txsegsizep); } tp->t_segsz = *txsegsizep; } return (0); }
/* * 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; #ifdef TCP_SIGNATURE int sigoff = 0; #endif struct mbuf *m; struct ip *ip = NULL; struct ipovly *ipov = NULL; struct tcphdr *th; u_char opt[TCP_MAXOLEN]; unsigned ipoptlen, optlen, hdrlen; int idle, sendalot; int i, sack_rxmit; int sack_bytes_rxmt; struct sackhole *p; #if 0 int maxburst = TCP_MAXBURST; #endif struct rmxp_tao tao; #ifdef INET6 struct ip6_hdr *ip6 = NULL; int isipv6; bzero(&tao, sizeof(tao)); isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; #endif #ifdef TCP_ECN int needect; #endif INP_LOCK_ASSERT(tp->t_inpcb); /* * 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 && (ticks - 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. */ int ss = ss_fltsz; #ifdef INET6 if (isipv6) { if (in6_localaddr(&tp->t_inpcb->in6p_faddr)) ss = ss_fltsz_local; } else #endif if (in_localaddr(tp->t_inpcb->inp_faddr)) ss = ss_fltsz_local; tp->snd_cwnd = tp->t_maxseg * ss; } tp->t_flags &= ~TF_LASTIDLE; if (idle) { if (tp->t_flags & TF_MORETOCOME) { tp->t_flags |= TF_LASTIDLE; idle = 0; } } again: /* * 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); sendwin = min(sendwin, tp->snd_bwnd); 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; KASSERT(off >= 0,("%s: sack block to the left of una : %d", __func__, off)); 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; SOCKBUF_LOCK(&so->so_snd); /* * 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 { callout_stop(tp->tt_persist); 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 (tcp_do_rfc1644) tcp_hc_gettao(&tp->t_inpcb->inp_inc, &tao); if (len > 0 && tp->t_state == TCPS_SYN_SENT && tao.tao_ccsent == 0) goto just_return; } /* * Be careful not to send data and/or FIN on SYN segments * in cases when no CC option will be sent. * This measure is needed to prevent interoperability problems * with not fully conformant TCP implementations. */ if ((flags & TH_SYN) && ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 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) { callout_stop(tp->tt_rexmt); tp->t_rxtshift = 0; tp->snd_nxt = tp->snd_una; if (!callout_active(tp->tt_persist)) 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; 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; } 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; /* * NOTE! on localhost connections an 'ack' from the remote * end may occur synchronously with the output and cause * us to flush a buffer queued with moretocome. XXX * * note: the len + off check is almost certainly unnecessary. */ if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ (idle || (tp->t_flags & TF_NODELAY)) && len + off >= so->so_snd.sb_cc && (tp->t_flags & TF_NOPUSH) == 0) { goto send; } if (tp->t_force) /* typ. timeout case */ 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) && !callout_active(tp->tt_rexmt) && !callout_active(tp->tt_persist)) { callout_reset(tp->tt_rexmt, tp->t_rxtcur, tcp_timer_rexmt, tp); 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 * * callout_active(tp->tt_persist) * is true when we are in persist state. * tp->t_force * is set when we are called to send a persist packet. * callout_active(tp->tt_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 && !callout_active(tp->tt_rexmt) && !callout_active(tp->tt_persist)) { tp->t_rxtshift = 0; tcp_setpersist(tp); } /* * No reason to send a segment, just return. */ just_return: SOCKBUF_UNLOCK(&so->so_snd); return (0); send: SOCKBUF_LOCK_ASSERT(&so->so_snd); /* * 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; #ifdef 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->t_inpcb->inp_inc)); (void)memcpy(opt + 2, &mss, sizeof(mss)); optlen = TCPOLEN_MAXSEG; /* * If this is the first SYN of connection (not a SYN * ACK), include SACK_PERMIT_HDR option. If this is a * SYN ACK, include SACK_PERMIT_HDR option if peer has * already done so. This is only for active connect, * since the syncache takes care of the passive connect. */ if (tp->sack_enable && ((flags & TH_ACK) == 0 || (tp->t_flags & TF_SACK_PERMIT))) { *((u_int32_t *) (opt + optlen)) = htonl(TCPOPT_SACK_PERMIT_HDR); optlen += 4; } 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(ticks); *lp = htonl(tp->ts_recent); optlen += TCPOLEN_TSTAMP_APPA; } /* * 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. No more than three SACKs are sent. */ if (tp->sack_enable && tp->t_state == TCPS_ESTABLISHED && (tp->t_flags & (TF_SACK_PERMIT|TF_NOOPT)) == TF_SACK_PERMIT && tp->rcv_numsacks) { u_int32_t *lp = (u_int32_t *)(opt + optlen); u_int32_t *olp = lp++; int count = 0; /* actual number of SACKs inserted */ int maxsack = (MAX_TCPOPTLEN - (optlen + 4))/TCPOLEN_SACK; tcpstat.tcps_sack_send_blocks++; maxsack = min(maxsack, TCP_MAX_SACK); for (i = 0; (i < tp->rcv_numsacks && count < maxsack); i++) { struct sackblk sack = tp->sackblks[i]; if (sack.start == 0 && sack.end == 0) continue; *lp++ = htonl(sack.start); *lp++ = htonl(sack.end); count++; } *olp = htonl(TCPOPT_SACK_HDR|(TCPOLEN_SACK*count+2)); optlen += TCPOLEN_SACK*count + 4; /* including leading NOPs */ } /* * Send `CC-family' options if our side wants to use them (TF_REQ_CC), * options are allowed (!TF_NOOPT) and it's not a RST. */ if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && (flags & TH_RST) == 0) { switch (flags & (TH_SYN|TH_ACK)) { /* * This is a normal ACK, send CC if we received CC before * from our peer. */ case TH_ACK: if (!(tp->t_flags & TF_RCVD_CC)) break; /*FALLTHROUGH*/ /* * We can only get here in T/TCP's SYN_SENT* state, when * we're a sending a non-SYN segment without waiting for * the ACK of our SYN. A check above assures that we only * do this if our peer understands T/TCP. */ case 0: opt[optlen++] = TCPOPT_NOP; opt[optlen++] = TCPOPT_NOP; opt[optlen++] = TCPOPT_CC; opt[optlen++] = TCPOLEN_CC; *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); optlen += 4; break; /* * This is our initial SYN, check whether we have to use * CC or CC.new. */ case TH_SYN: opt[optlen++] = TCPOPT_NOP; opt[optlen++] = TCPOPT_NOP; opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? TCPOPT_CCNEW : TCPOPT_CC; opt[optlen++] = TCPOLEN_CC; *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); optlen += 4; break; /* * This is a SYN,ACK; send CC and CC.echo if we received * CC from our peer. */ case (TH_SYN|TH_ACK): if (tp->t_flags & TF_RCVD_CC) { opt[optlen++] = TCPOPT_NOP; opt[optlen++] = TCPOPT_NOP; opt[optlen++] = TCPOPT_CC; opt[optlen++] = TCPOLEN_CC; *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); optlen += 4; opt[optlen++] = TCPOPT_NOP; opt[optlen++] = TCPOPT_NOP; opt[optlen++] = TCPOPT_CCECHO; opt[optlen++] = TCPOLEN_CC; *(u_int32_t *)&opt[optlen] = htonl(tp->cc_recv); optlen += 4; } break; } } #ifdef TCP_SIGNATURE #ifdef INET6 if (!isipv6) #endif if (tp->t_flags & TF_SIGNATURE) { int i; u_char *bp; /* Initialize TCP-MD5 option (RFC2385) */ bp = (u_char *)opt + optlen; *bp++ = TCPOPT_SIGNATURE; *bp++ = TCPOLEN_SIGNATURE; sigoff = optlen + 2; for (i = 0; i < TCP_SIGLEN; i++) *bp++ = 0; optlen += TCPOLEN_SIGNATURE; /* Terminate options list and maintain 32-bit alignment. */ *bp++ = TCPOPT_NOP; *bp++ = TCPOPT_EOL; optlen += 2; } #endif /* TCP_SIGNATURE */ hdrlen += optlen; #ifdef 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