static void dctcp_ack_received(struct cc_var *ccv, uint16_t type) { struct dctcp *dctcp_data; int bytes_acked = 0; dctcp_data = ccv->cc_data; if (CCV(ccv, t_flags) & TF_ECN_PERMIT) { /* * DCTCP doesn't treat receipt of ECN marked packet as a * congestion event. Thus, DCTCP always executes the ACK * processing out of congestion recovery. */ if (IN_CONGRECOVERY(CCV(ccv, t_flags))) { EXIT_CONGRECOVERY(CCV(ccv, t_flags)); newreno_cc_algo.ack_received(ccv, type); ENTER_CONGRECOVERY(CCV(ccv, t_flags)); } else newreno_cc_algo.ack_received(ccv, type); if (type == CC_DUPACK) bytes_acked = CCV(ccv, t_maxseg); if (type == CC_ACK) bytes_acked = ccv->bytes_this_ack; /* Update total bytes. */ dctcp_data->bytes_total += bytes_acked; /* Update total marked bytes. */ if (dctcp_data->ece_curr) { if (!dctcp_data->ece_prev && bytes_acked > CCV(ccv, t_maxseg)) { dctcp_data->bytes_ecn += (bytes_acked - CCV(ccv, t_maxseg)); } else dctcp_data->bytes_ecn += bytes_acked; dctcp_data->ece_prev = 1; } else { if (dctcp_data->ece_prev && bytes_acked > CCV(ccv, t_maxseg)) dctcp_data->bytes_ecn += CCV(ccv, t_maxseg); dctcp_data->ece_prev = 0; } dctcp_data->ece_curr = 0; /* * Update the fraction of marked bytes at the end of * current window size. */ if ((IN_FASTRECOVERY(CCV(ccv, t_flags)) && SEQ_GEQ(ccv->curack, CCV(ccv, snd_recover))) || (!IN_FASTRECOVERY(CCV(ccv, t_flags)) && SEQ_GT(ccv->curack, dctcp_data->save_sndnxt))) dctcp_update_alpha(ccv); } else newreno_cc_algo.ack_received(ccv, type); }
/* * Perform any necessary tasks before we enter congestion recovery. */ static void newreno_cong_signal(struct cc_var *ccv, uint32_t type) { u_int win; /* Catch algos which mistakenly leak private signal types. */ KASSERT((type & CC_SIGPRIVMASK) == 0, ("%s: congestion signal type 0x%08x is private\n", __func__, type)); win = max(CCV(ccv, snd_cwnd) / 2 / CCV(ccv, t_maxseg), 2) * CCV(ccv, t_maxseg); switch (type) { case CC_NDUPACK: if (!IN_FASTRECOVERY(CCV(ccv, t_flags))) { if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) CCV(ccv, snd_ssthresh) = win; ENTER_RECOVERY(CCV(ccv, t_flags)); } break; case CC_ECN: if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) { CCV(ccv, snd_ssthresh) = win; CCV(ccv, snd_cwnd) = win; ENTER_CONGRECOVERY(CCV(ccv, t_flags)); } break; } }
/* * Perform any necessary tasks before we exit congestion recovery. */ static void newreno_post_recovery(struct cc_var *ccv) { int pipe; pipe = 0; if (IN_FASTRECOVERY(CCV(ccv, t_flags))) { /* * Fast recovery will conclude after returning from this * function. Window inflation should have left us with * approximately snd_ssthresh outstanding data. But in case we * would be inclined to send a burst, better to do it via the * slow start mechanism. * * XXXLAS: Find a way to do this without needing curack */ if (V_tcp_do_rfc6675_pipe) pipe = tcp_compute_pipe(ccv->ccvc.tcp); else pipe = CCV(ccv, snd_max) - ccv->curack; if (pipe < CCV(ccv, snd_ssthresh)) CCV(ccv, snd_cwnd) = pipe + CCV(ccv, t_maxseg); else CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh); } }
void tcp_save_congestion_state(struct tcpcb *tp) { /* * Record connection's current states so that they could be * recovered, if this turns out to be a spurious retransmit. */ tp->snd_cwnd_prev = tp->snd_cwnd; tp->snd_wacked_prev = tp->snd_wacked; tp->snd_ssthresh_prev = tp->snd_ssthresh; tp->snd_recover_prev = tp->snd_recover; /* * State for Eifel response after spurious timeout retransmit * is detected. We save the current value of snd_max even if * we are called from fast retransmit code, so if RTO needs * rebase, it will be rebased using the RTT of segment that * is not sent during possible congestion. */ tp->snd_max_prev = tp->snd_max; if (IN_FASTRECOVERY(tp)) tp->rxt_flags |= TRXT_F_WASFRECOVERY; else tp->rxt_flags &= ~TRXT_F_WASFRECOVERY; if (tp->t_flags & TF_RCVD_TSTMP) { /* States for Eifel detection */ tp->t_rexmtTS = ticks; tp->rxt_flags |= TRXT_F_FIRSTACCACK; } #ifdef later tcp_sack_save_scoreboard(&tp->scb); #endif }
void tcp_save_congestion_state(struct tcpcb *tp) { tp->snd_cwnd_prev = tp->snd_cwnd; tp->snd_wacked_prev = tp->snd_wacked; tp->snd_ssthresh_prev = tp->snd_ssthresh; tp->snd_recover_prev = tp->snd_recover; tp->t_rxtcur_prev = tp->t_rxtcur; tp->t_srtt_prev = tp->t_srtt + (tcp_eifel_rtoinc << TCP_RTT_SHIFT); tp->t_rttvar_prev = tp->t_rttvar; tp->snd_max_prev = tp->snd_max; tp->rxt_flags &= ~TRXT_F_REBASERTO; if (IN_FASTRECOVERY(tp)) tp->rxt_flags |= TRXT_F_WASFRECOVERY; else tp->rxt_flags &= ~TRXT_F_WASFRECOVERY; if (tp->t_flags & TF_RCVD_TSTMP) { tp->t_rexmtTS = ticks; tp->rxt_flags |= TRXT_F_FIRSTACCACK; } #ifdef later tcp_sack_save_scoreboard(&tp->scb); #endif }
static void tcp_cubic_after_timeout(struct tcpcb *tp) { VERIFY(tp->t_ccstate != NULL); if (!IN_FASTRECOVERY(tp)) { tcp_cubic_clear_state(tp); tcp_cubic_pre_fr(tp); } /* * Close the congestion window down to one segment as a retransmit * timeout might indicate severe congestion. */ tp->snd_cwnd = tp->t_maxseg; }
/* * Perform any necessary tasks before we enter congestion recovery. */ static void newreno_cong_signal(struct cc_var *ccv, uint32_t type) { uint32_t cwin, ssthresh_on_loss; u_int mss; cwin = CCV(ccv, snd_cwnd); mss = CCV(ccv, t_maxseg); ssthresh_on_loss = max((CCV(ccv, snd_max) - CCV(ccv, snd_una)) / 2 / mss, 2) * mss; /* Catch algos which mistakenly leak private signal types. */ KASSERT((type & CC_SIGPRIVMASK) == 0, ("%s: congestion signal type 0x%08x is private\n", __func__, type)); cwin = max(cwin / 2 / mss, 2) * mss; switch (type) { case CC_NDUPACK: if (!IN_FASTRECOVERY(CCV(ccv, t_flags))) { if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) { CCV(ccv, snd_ssthresh) = ssthresh_on_loss; CCV(ccv, snd_cwnd) = cwin; } ENTER_RECOVERY(CCV(ccv, t_flags)); } break; case CC_ECN: if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) { CCV(ccv, snd_ssthresh) = ssthresh_on_loss; CCV(ccv, snd_cwnd) = cwin; ENTER_CONGRECOVERY(CCV(ccv, t_flags)); } break; case CC_RTO: CCV(ccv, snd_ssthresh) = ssthresh_on_loss; CCV(ccv, snd_cwnd) = mss; break; } }
/* * Tcp output routine: figure out what should be sent and send it. */ int tcp_output(struct tcpcb *tp) { struct inpcb * const inp = tp->t_inpcb; struct socket *so = inp->inp_socket; long len, recvwin, sendwin; int nsacked = 0; 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 int ipoptlen, optlen, hdrlen; int idle; boolean_t sendalot; struct ip6_hdr *ip6 = NULL; #ifdef INET6 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; #else const boolean_t isipv6 = FALSE; #endif KKASSERT(so->so_port == &curthread->td_msgport); /* * 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. */ /* * If we have been idle for a while, the send congestion window * could be no longer representative of the current state of the link. * So unless we are expecting more acks to come in, slow-start from * scratch to re-determine the send congestion window. */ if (tp->snd_max == tp->snd_una && (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { if (tcp_do_rfc3390) { int initial_cwnd = min(4 * tp->t_maxseg, max(2 * tp->t_maxseg, 4380)); tp->snd_cwnd = min(tp->snd_cwnd, initial_cwnd); } else { tp->snd_cwnd = tp->t_maxseg; } tp->snd_wacked = 0; } /* * Calculate whether the transmit stream was previously idle * and adjust TF_LASTIDLE for the next time. */ idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); if (idle && (tp->t_flags & TF_MORETOCOME)) tp->t_flags |= TF_LASTIDLE; else tp->t_flags &= ~TF_LASTIDLE; if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && !IN_FASTRECOVERY(tp)) nsacked = tcp_sack_bytes_below(&tp->scb, tp->snd_nxt); again: /* Make use of SACK information when slow-starting after a RTO. */ if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && !IN_FASTRECOVERY(tp)) { tcp_seq old_snd_nxt = tp->snd_nxt; tcp_sack_skip_sacked(&tp->scb, &tp->snd_nxt); nsacked += tp->snd_nxt - old_snd_nxt; } sendalot = FALSE; off = tp->snd_nxt - tp->snd_una; sendwin = min(tp->snd_wnd, tp->snd_cwnd + nsacked); sendwin = min(sendwin, tp->snd_bwnd); flags = tcp_outflags[tp->t_state]; /* * 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_flags & 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.ssb_cc) flags &= ~TH_FIN; sendwin = 1; } else { tcp_callout_stop(tp, 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.ssb_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. */ len = (long)ulmin(so->so_snd.ssb_cc, sendwin) - off; /* * Lop off SYN bit if it has already been sent. However, if this * is SYN-SENT state and if segment contains data, suppress sending * segment (sending the segment would be an option if we still * did TAO and the remote host supported it). */ 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) 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) { 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) { tcp_callout_stop(tp, tp->tt_rexmt); tp->t_rxtshift = 0; tp->snd_nxt = tp->snd_una; if (!tcp_callout_active(tp, tp->tt_persist)) tcp_setpersist(tp); } } KASSERT(len >= 0, ("%s: len < 0", __func__)); /* * Automatic sizing of send socket buffer. Often the send buffer * size is not optimally adjusted to the actual network conditions * at hand (delay bandwidth product). Setting the buffer size too * small limits throughput on links with high bandwidth and high * delay (eg. trans-continental/oceanic links). Setting the * buffer size too big consumes too much real kernel memory, * especially with many connections on busy servers. * * The criteria to step up the send buffer one notch are: * 1. receive window of remote host is larger than send buffer * (with a fudge factor of 5/4th); * 2. send buffer is filled to 7/8th with data (so we actually * have data to make use of it); * 3. send buffer fill has not hit maximal automatic size; * 4. our send window (slow start and cogestion controlled) is * larger than sent but unacknowledged data in send buffer. * * The remote host receive window scaling factor may limit the * growing of the send buffer before it reaches its allowed * maximum. * * It scales directly with slow start or congestion window * and does at most one step per received ACK. This fast * scaling has the drawback of growing the send buffer beyond * what is strictly necessary to make full use of a given * delay*bandwith product. However testing has shown this not * to be much of an problem. At worst we are trading wasting * of available bandwith (the non-use of it) for wasting some * socket buffer memory. * * TODO: Shrink send buffer during idle periods together * with congestion window. Requires another timer. Has to * wait for upcoming tcp timer rewrite. */ if (tcp_do_autosndbuf && so->so_snd.ssb_flags & SSB_AUTOSIZE) { if ((tp->snd_wnd / 4 * 5) >= so->so_snd.ssb_hiwat && so->so_snd.ssb_cc >= (so->so_snd.ssb_hiwat / 8 * 7) && so->so_snd.ssb_cc < tcp_autosndbuf_max && sendwin >= (so->so_snd.ssb_cc - (tp->snd_nxt - tp->snd_una))) { u_long newsize; newsize = ulmin(so->so_snd.ssb_hiwat + tcp_autosndbuf_inc, tcp_autosndbuf_max); if (!ssb_reserve(&so->so_snd, newsize, so, NULL)) atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE); if (newsize >= (TCP_MAXWIN << tp->snd_scale)) atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE); } } /* * 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 = TRUE; } if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.ssb_cc)) flags &= ~TH_FIN; recvwin = ssb_space(&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 limiting 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.ssb_cc && !(tp->t_flags & TF_NOPUSH)) { goto send; } if (tp->t_flags & TF_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; } /* * 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. */ if (recvwin > 0) { /* * "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(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - (tp->rcv_adv - tp->rcv_nxt); long hiwat; /* * This ack case typically occurs when the user has drained * the TCP socket buffer sufficiently to warrent an ack * containing a 'pure window update'... that is, an ack that * ONLY updates the tcp window. * * It is unclear why we would need to do a pure window update * past 2 segments if we are going to do one at 1/2 the high * water mark anyway, especially since under normal conditions * the user program will drain the socket buffer quickly. * The 2-segment pure window update will often add a large * number of extra, unnecessary acks to the stream. * * avoid_pure_win_update now defaults to 1. */ if (avoid_pure_win_update == 0 || (tp->t_flags & TF_RXRESIZED)) { if (adv >= (long) (2 * tp->t_maxseg)) { goto send; } } hiwat = (long)(TCP_MAXWIN << tp->rcv_scale); if (hiwat > (long)so->so_rcv.ssb_hiwat) hiwat = (long)so->so_rcv.ssb_hiwat; if (adv >= hiwat / 2) 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))) 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) || tp->snd_nxt == tp->snd_una)) goto send; /* * 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 * * tcp_callout_active(tp, tp->tt_persist) * is true when we are in persist state. * The TF_FORCE flag in tp->t_flags * is set when we are called to send a persist packet. * tcp_callout_active(tp, 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.ssb_cc > 0 && !tcp_callout_active(tp, tp->tt_rexmt) && !tcp_callout_active(tp, tp->tt_persist)) { tp->t_rxtshift = 0; tcp_setpersist(tp); } /* * No reason to send a segment, just return. */ 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 (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)) { u_short mss; opt[0] = TCPOPT_MAXSEG; opt[1] = TCPOLEN_MAXSEG; mss = htons((u_short) tcp_mssopt(tp)); memcpy(opt + 2, &mss, sizeof mss); optlen = TCPOLEN_MAXSEG; if ((tp->t_flags & TF_REQ_SCALE) && (!(flags & TH_ACK) || (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; } if ((tcp_do_sack && !(flags & TH_ACK)) || tp->t_flags & TF_SACK_PERMITTED) { uint32_t *lp = (uint32_t *)(opt + optlen); *lp = htonl(TCPOPT_SACK_PERMITTED_ALIGNED); optlen += TCPOLEN_SACK_PERMITTED_ALIGNED; } } } /* * 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) && (!(flags & TH_ACK) || (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; } /* Set receive buffer autosizing timestamp. */ if (tp->rfbuf_ts == 0 && (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) tp->rfbuf_ts = ticks; /* * If this is a SACK connection and we have a block to report, * fill in the SACK blocks in the TCP options. */ if ((tp->t_flags & (TF_SACK_PERMITTED | TF_NOOPT)) == TF_SACK_PERMITTED && (!LIST_EMPTY(&tp->t_segq) || tp->reportblk.rblk_start != tp->reportblk.rblk_end)) tcp_sack_fill_report(tp, opt, &optlen); #ifdef TCP_SIGNATURE 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 */ KASSERT(optlen <= TCP_MAXOLEN, ("too many TCP options")); hdrlen += optlen; if (isipv6) { ipoptlen = ip6_optlen(inp); } else { if (inp->inp_options) { ipoptlen = inp->inp_options->m_len - offsetof(struct ipoption, ipopt_list); } else {
void tcp_timer_rexmt(void * xtp) { struct tcpcb *tp = xtp; CURVNET_SET(tp->t_vnet); int rexmt; struct inpcb *inp; #ifdef TCPDEBUG int ostate; ostate = tp->t_state; #endif inp = tp->t_inpcb; KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp)); INP_WLOCK(inp); if (callout_pending(&tp->t_timers->tt_rexmt) || !callout_active(&tp->t_timers->tt_rexmt)) { INP_WUNLOCK(inp); CURVNET_RESTORE(); return; } callout_deactivate(&tp->t_timers->tt_rexmt); if ((inp->inp_flags & INP_DROPPED) != 0) { INP_WUNLOCK(inp); CURVNET_RESTORE(); return; } KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0, ("%s: tp %p tcpcb can't be stopped here", __func__, tp)); tcp_free_sackholes(tp); if (tp->t_fb->tfb_tcp_rexmit_tmr) { /* The stack has a timer action too. */ (*tp->t_fb->tfb_tcp_rexmit_tmr)(tp); } /* * Retransmission timer went off. Message has not * been acked within retransmit interval. Back off * to a longer retransmit interval and retransmit one segment. */ if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { tp->t_rxtshift = TCP_MAXRXTSHIFT; TCPSTAT_INC(tcps_timeoutdrop); if (tcp_inpinfo_lock_add(inp)) { tcp_inpinfo_lock_del(inp, tp); goto out; } tp = tcp_drop(tp, tp->t_softerror ? tp->t_softerror : ETIMEDOUT); tcp_inpinfo_lock_del(inp, tp); goto out; } if (tp->t_state == TCPS_SYN_SENT) { /* * If the SYN was retransmitted, indicate CWND to be * limited to 1 segment in cc_conn_init(). */ tp->snd_cwnd = 1; } else if (tp->t_rxtshift == 1) { /* * first retransmit; record ssthresh and cwnd so they can * be recovered if this turns out to be a "bad" retransmit. * A retransmit is considered "bad" if an ACK for this * segment is received within RTT/2 interval; the assumption * here is that the ACK was already in flight. See * "On Estimating End-to-End Network Path Properties" by * Allman and Paxson for more details. */ tp->snd_cwnd_prev = tp->snd_cwnd; tp->snd_ssthresh_prev = tp->snd_ssthresh; tp->snd_recover_prev = tp->snd_recover; if (IN_FASTRECOVERY(tp->t_flags)) tp->t_flags |= TF_WASFRECOVERY; else tp->t_flags &= ~TF_WASFRECOVERY; if (IN_CONGRECOVERY(tp->t_flags)) tp->t_flags |= TF_WASCRECOVERY; else tp->t_flags &= ~TF_WASCRECOVERY; tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1)); tp->t_flags |= TF_PREVVALID; } else
void tcp_timer_rexmt(void * xtp) { struct tcpcb *tp = xtp; CURVNET_SET(tp->t_vnet); int rexmt; int headlocked; struct inpcb *inp; #ifdef TCPDEBUG int ostate; ostate = tp->t_state; #endif INP_INFO_RLOCK(&V_tcbinfo); inp = tp->t_inpcb; /* * XXXRW: While this assert is in fact correct, bugs in the tcpcb * tear-down mean we need it as a work-around for races between * timers and tcp_discardcb(). * * KASSERT(inp != NULL, ("tcp_timer_rexmt: inp == NULL")); */ if (inp == NULL) { tcp_timer_race++; INP_INFO_RUNLOCK(&V_tcbinfo); CURVNET_RESTORE(); return; } INP_WLOCK(inp); if ((inp->inp_flags & INP_DROPPED) || callout_pending(&tp->t_timers->tt_rexmt) || !callout_active(&tp->t_timers->tt_rexmt)) { INP_WUNLOCK(inp); INP_INFO_RUNLOCK(&V_tcbinfo); CURVNET_RESTORE(); return; } callout_deactivate(&tp->t_timers->tt_rexmt); tcp_free_sackholes(tp); /* * Retransmission timer went off. Message has not * been acked within retransmit interval. Back off * to a longer retransmit interval and retransmit one segment. */ if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { tp->t_rxtshift = TCP_MAXRXTSHIFT; TCPSTAT_INC(tcps_timeoutdrop); in_pcbref(inp); INP_INFO_RUNLOCK(&V_tcbinfo); INP_WUNLOCK(inp); INP_INFO_WLOCK(&V_tcbinfo); INP_WLOCK(inp); if (in_pcbrele_wlocked(inp)) { INP_INFO_WUNLOCK(&V_tcbinfo); CURVNET_RESTORE(); return; } if (inp->inp_flags & INP_DROPPED) { INP_WUNLOCK(inp); INP_INFO_WUNLOCK(&V_tcbinfo); CURVNET_RESTORE(); return; } tp = tcp_drop(tp, tp->t_softerror ? tp->t_softerror : ETIMEDOUT); headlocked = 1; goto out; } INP_INFO_RUNLOCK(&V_tcbinfo); headlocked = 0; if (tp->t_rxtshift == 1) { /* * first retransmit; record ssthresh and cwnd so they can * be recovered if this turns out to be a "bad" retransmit. * A retransmit is considered "bad" if an ACK for this * segment is received within RTT/2 interval; the assumption * here is that the ACK was already in flight. See * "On Estimating End-to-End Network Path Properties" by * Allman and Paxson for more details. */ tp->snd_cwnd_prev = tp->snd_cwnd; tp->snd_ssthresh_prev = tp->snd_ssthresh; tp->snd_recover_prev = tp->snd_recover; if (IN_FASTRECOVERY(tp->t_flags)) tp->t_flags |= TF_WASFRECOVERY; else tp->t_flags &= ~TF_WASFRECOVERY; if (IN_CONGRECOVERY(tp->t_flags)) tp->t_flags |= TF_WASCRECOVERY; else tp->t_flags &= ~TF_WASCRECOVERY; tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1)); tp->t_flags |= TF_PREVVALID; } else
/* * Tcp output routine: figure out what should be sent and send it. */ int tcp_output(struct tcpcb *tp) { struct inpcb * const inp = tp->t_inpcb; struct socket *so = inp->inp_socket; long len, recvwin, sendwin; int nsacked = 0; int off, flags, error = 0; #ifdef TCP_SIGNATURE int sigoff = 0; #endif struct mbuf *m; struct ip *ip; struct tcphdr *th; u_char opt[TCP_MAXOLEN]; unsigned int ipoptlen, optlen, hdrlen; int idle; boolean_t sendalot; struct ip6_hdr *ip6; #ifdef INET6 const boolean_t isipv6 = INP_ISIPV6(inp); #else const boolean_t isipv6 = FALSE; #endif boolean_t can_tso = FALSE, use_tso; boolean_t report_sack, idle_cwv = FALSE; u_int segsz, tso_hlen, tso_lenmax = 0; int segcnt = 0; boolean_t need_sched = FALSE; KKASSERT(so->so_port == &curthread->td_msgport); /* * 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. */ /* * If we have been idle for a while, the send congestion window * could be no longer representative of the current state of the * link; need to validate congestion window. However, we should * not perform congestion window validation here, since we could * be asked to send pure ACK. */ if (tp->snd_max == tp->snd_una && (ticks - tp->snd_last) >= tp->t_rxtcur && tcp_idle_restart) idle_cwv = TRUE; /* * Calculate whether the transmit stream was previously idle * and adjust TF_LASTIDLE for the next time. */ idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); if (idle && (tp->t_flags & TF_MORETOCOME)) tp->t_flags |= TF_LASTIDLE; else tp->t_flags &= ~TF_LASTIDLE; if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && !IN_FASTRECOVERY(tp)) nsacked = tcp_sack_bytes_below(&tp->scb, tp->snd_nxt); /* * Find out whether TSO could be used or not * * For TSO capable devices, the following assumptions apply to * the processing of TCP flags: * - If FIN is set on the large TCP segment, the device must set * FIN on the last segment that it creates from the large TCP * segment. * - If PUSH is set on the large TCP segment, the device must set * PUSH on the last segment that it creates from the large TCP * segment. */ #if !defined(IPSEC) && !defined(FAST_IPSEC) if (tcp_do_tso #ifdef TCP_SIGNATURE && (tp->t_flags & TF_SIGNATURE) == 0 #endif ) { if (!isipv6) { struct rtentry *rt = inp->inp_route.ro_rt; if (rt != NULL && (rt->rt_flags & RTF_UP) && (rt->rt_ifp->if_hwassist & CSUM_TSO)) { can_tso = TRUE; tso_lenmax = rt->rt_ifp->if_tsolen; } } } #endif /* !IPSEC && !FAST_IPSEC */ again: m = NULL; ip = NULL; th = NULL; ip6 = NULL; if ((tp->t_flags & (TF_SACK_PERMITTED | TF_NOOPT)) == TF_SACK_PERMITTED && (!TAILQ_EMPTY(&tp->t_segq) || tp->reportblk.rblk_start != tp->reportblk.rblk_end)) report_sack = TRUE; else report_sack = FALSE; /* Make use of SACK information when slow-starting after a RTO. */ if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && !IN_FASTRECOVERY(tp)) { tcp_seq old_snd_nxt = tp->snd_nxt; tcp_sack_skip_sacked(&tp->scb, &tp->snd_nxt); nsacked += tp->snd_nxt - old_snd_nxt; } sendalot = FALSE; off = tp->snd_nxt - tp->snd_una; sendwin = min(tp->snd_wnd, tp->snd_cwnd + nsacked); sendwin = min(sendwin, tp->snd_bwnd); flags = tcp_outflags[tp->t_state]; /* * 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_flags & 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.ssb_cc) flags &= ~TH_FIN; sendwin = 1; } else { tcp_callout_stop(tp, 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.ssb_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. * * A negative length can also occur when we are in the * TCPS_SYN_RECEIVED state due to a simultanious connect where * our SYN has not been acked yet. * * 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. */ len = (long)ulmin(so->so_snd.ssb_cc, sendwin) - off; /* * Lop off SYN bit if it has already been sent. However, if this * is SYN-SENT state and if segment contains data, suppress sending * segment (sending the segment would be an option if we still * did TAO and the remote host supported it). */ 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) { tp->t_flags &= ~(TF_ACKNOW | TF_XMITNOW); 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) { len = 0; flags &= ~TH_FIN; } if (len < 0) { /* * A negative len can occur if our FIN has been sent but not * acked, or if we are in a simultanious connect in the * TCPS_SYN_RECEIVED state with our SYN sent but not yet * acked. * * If our window has contracted to 0 in the FIN case * (which can only occur if we have NOT been called to * retransmit as per code a few paragraphs up) then we * want to shift the retransmit timer over to the * persist timer. * * However, if we are in the TCPS_SYN_RECEIVED state * (the SYN case) we will be in a simultanious connect and * the window may be zero degeneratively. In this case we * do not want to shift to the persist timer after the SYN * or the SYN+ACK transmission. */ len = 0; if (sendwin == 0 && tp->t_state != TCPS_SYN_RECEIVED) { tcp_callout_stop(tp, tp->tt_rexmt); tp->t_rxtshift = 0; tp->snd_nxt = tp->snd_una; if (!tcp_callout_active(tp, tp->tt_persist)) tcp_setpersist(tp); } } KASSERT(len >= 0, ("%s: len < 0", __func__)); /* * Automatic sizing of send socket buffer. Often the send buffer * size is not optimally adjusted to the actual network conditions * at hand (delay bandwidth product). Setting the buffer size too * small limits throughput on links with high bandwidth and high * delay (eg. trans-continental/oceanic links). Setting the * buffer size too big consumes too much real kernel memory, * especially with many connections on busy servers. * * The criteria to step up the send buffer one notch are: * 1. receive window of remote host is larger than send buffer * (with a fudge factor of 5/4th); * 2. hiwat has not significantly exceeded bwnd (inflight) * (bwnd is a maximal value if inflight is disabled). * 3. send buffer is filled to 7/8th with data (so we actually * have data to make use of it); * 4. hiwat has not hit maximal automatic size; * 5. our send window (slow start and cogestion controlled) is * larger than sent but unacknowledged data in send buffer. * * The remote host receive window scaling factor may limit the * growing of the send buffer before it reaches its allowed * maximum. * * It scales directly with slow start or congestion window * and does at most one step per received ACK. This fast * scaling has the drawback of growing the send buffer beyond * what is strictly necessary to make full use of a given * delay*bandwith product. However testing has shown this not * to be much of an problem. At worst we are trading wasting * of available bandwith (the non-use of it) for wasting some * socket buffer memory. * * The criteria for shrinking the buffer is based solely on * the inflight code (snd_bwnd). If inflight is disabled, * the buffer will not be shrinked. Note that snd_bwnd already * has a fudge factor. Our test adds a little hysteresis. */ if (tcp_do_autosndbuf && (so->so_snd.ssb_flags & SSB_AUTOSIZE)) { const int asbinc = tcp_autosndbuf_inc; const int hiwat = so->so_snd.ssb_hiwat; const int lowat = so->so_snd.ssb_lowat; u_long newsize; if ((tp->snd_wnd / 4 * 5) >= hiwat && so->so_snd.ssb_cc >= (hiwat / 8 * 7) && hiwat < tp->snd_bwnd + hiwat / 10 && hiwat + asbinc < tcp_autosndbuf_max && hiwat < (TCP_MAXWIN << tp->snd_scale) && sendwin >= (so->so_snd.ssb_cc - (tp->snd_nxt - tp->snd_una))) { newsize = ulmin(hiwat + asbinc, tcp_autosndbuf_max); if (!ssb_reserve(&so->so_snd, newsize, so, NULL)) atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE); #if 0 if (newsize >= (TCP_MAXWIN << tp->snd_scale)) atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE); #endif } else if ((long)tp->snd_bwnd < (long)(hiwat * 3 / 4 - lowat - asbinc) && hiwat > tp->t_maxseg * 2 + asbinc && hiwat + asbinc >= tcp_autosndbuf_min && tcp_do_autosndbuf == 1) { newsize = ulmax(hiwat - asbinc, tp->t_maxseg * 2); ssb_reserve(&so->so_snd, newsize, so, NULL); } } /* * Don't use TSO, if: * - Congestion window needs validation * - There are SACK blocks to report * - RST or SYN flags is set * - URG will be set * * XXX * Checking for SYN|RST looks overkill, just to be safe than sorry */ use_tso = can_tso; if (report_sack || idle_cwv || (flags & (TH_RST | TH_SYN))) use_tso = FALSE; if (use_tso) { tcp_seq ugr_nxt = tp->snd_nxt; if ((flags & TH_FIN) && (tp->t_flags & TF_SENTFIN) && tp->snd_nxt == tp->snd_max) --ugr_nxt; if (SEQ_GT(tp->snd_up, ugr_nxt)) use_tso = FALSE; } if (use_tso) { /* * Find out segment size and header length for TSO */ error = tcp_tso_getsize(tp, &segsz, &tso_hlen); if (error) use_tso = FALSE; } if (!use_tso) { segsz = tp->t_maxseg; tso_hlen = 0; /* not used */ } /* * Truncate to the maximum segment length if not TSO, and ensure that * FIN is removed if the length no longer contains the last data byte. */ if (len > segsz) { if (!use_tso) { len = segsz; ++segcnt; } else { int nsegs; if (__predict_false(tso_lenmax < segsz)) tso_lenmax = segsz << 1; /* * Truncate TSO transfers to (IP_MAXPACKET - iphlen - * thoff), and make sure that we send equal size * transfers down the stack (rather than big-small- * big-small-...). */ len = min(len, tso_lenmax); nsegs = min(len, (IP_MAXPACKET - tso_hlen)) / segsz; KKASSERT(nsegs > 0); len = nsegs * segsz; if (len <= segsz) { use_tso = FALSE; ++segcnt; } else { segcnt += nsegs; } } sendalot = TRUE; } else { use_tso = FALSE; if (len > 0) ++segcnt; } if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.ssb_cc)) flags &= ~TH_FIN; recvwin = ssb_space(&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 limiting the window size) * - we need to retransmit */ if (len) { if (len >= segsz) 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.ssb_cc && !(tp->t_flags & TF_NOPUSH)) { goto send; } if (tp->t_flags & TF_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 (tp->t_flags & TF_XMITNOW) 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. */ if (recvwin > 0) { /* * "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(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - (tp->rcv_adv - tp->rcv_nxt); long hiwat; /* * This ack case typically occurs when the user has drained * the TCP socket buffer sufficiently to warrent an ack * containing a 'pure window update'... that is, an ack that * ONLY updates the tcp window. * * It is unclear why we would need to do a pure window update * past 2 segments if we are going to do one at 1/2 the high * water mark anyway, especially since under normal conditions * the user program will drain the socket buffer quickly. * The 2-segment pure window update will often add a large * number of extra, unnecessary acks to the stream. * * avoid_pure_win_update now defaults to 1. */ if (avoid_pure_win_update == 0 || (tp->t_flags & TF_RXRESIZED)) { if (adv >= (long) (2 * segsz)) { goto send; } } hiwat = (long)(TCP_MAXWIN << tp->rcv_scale); if (hiwat > (long)so->so_rcv.ssb_hiwat) hiwat = (long)so->so_rcv.ssb_hiwat; if (adv >= hiwat / 2) 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))) 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) || tp->snd_nxt == tp->snd_una)) goto send; /* * 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 * * tcp_callout_active(tp, tp->tt_persist) * is true when we are in persist state. * The TF_FORCE flag in tp->t_flags * is set when we are called to send a persist packet. * tcp_callout_active(tp, 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. * * Don't try to set the persist state if we are in TCPS_SYN_RECEIVED * with data pending. This situation can occur during a * simultanious connect. */ if (so->so_snd.ssb_cc > 0 && tp->t_state != TCPS_SYN_RECEIVED && !tcp_callout_active(tp, tp->tt_rexmt) && !tcp_callout_active(tp, tp->tt_persist)) { tp->t_rxtshift = 0; tcp_setpersist(tp); } /* * No reason to send a segment, just return. */ tp->t_flags &= ~TF_XMITNOW; return (0); send: if (need_sched && len > 0) { tcp_output_sched(tp); return 0; } /* * 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)) { u_short mss; opt[0] = TCPOPT_MAXSEG; opt[1] = TCPOLEN_MAXSEG; mss = htons((u_short) tcp_mssopt(tp)); memcpy(opt + 2, &mss, sizeof mss); optlen = TCPOLEN_MAXSEG; if ((tp->t_flags & TF_REQ_SCALE) && (!(flags & TH_ACK) || (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; } if ((tcp_do_sack && !(flags & TH_ACK)) || tp->t_flags & TF_SACK_PERMITTED) { uint32_t *lp = (uint32_t *)(opt + optlen); *lp = htonl(TCPOPT_SACK_PERMITTED_ALIGNED); optlen += TCPOLEN_SACK_PERMITTED_ALIGNED; } } } /* * 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) && (!(flags & TH_ACK) || (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; } /* Set receive buffer autosizing timestamp. */ if (tp->rfbuf_ts == 0 && (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) tp->rfbuf_ts = ticks; /* * If this is a SACK connection and we have a block to report, * fill in the SACK blocks in the TCP options. */ if (report_sack) tcp_sack_fill_report(tp, opt, &optlen); #ifdef TCP_SIGNATURE 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 */ KASSERT(optlen <= TCP_MAXOLEN, ("too many TCP options")); hdrlen += optlen; if (isipv6) { ipoptlen = ip6_optlen(inp); } else { if (inp->inp_options) { ipoptlen = inp->inp_options->m_len - offsetof(struct ipoption, ipopt_list); } else {
/* * Perform any necessary tasks before we enter congestion recovery. */ static void dctcp_cong_signal(struct cc_var *ccv, uint32_t type) { struct dctcp *dctcp_data; u_int win, mss; dctcp_data = ccv->cc_data; win = CCV(ccv, snd_cwnd); mss = CCV(ccv, t_maxseg); switch (type) { case CC_NDUPACK: if (!IN_FASTRECOVERY(CCV(ccv, t_flags))) { if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) { CCV(ccv, snd_ssthresh) = mss * max(win / 2 / mss, 2); dctcp_data->num_cong_events++; } else { /* cwnd has already updated as congestion * recovery. Reverse cwnd value using * snd_cwnd_prev and recalculate snd_ssthresh */ win = CCV(ccv, snd_cwnd_prev); CCV(ccv, snd_ssthresh) = max(win / 2 / mss, 2) * mss; } ENTER_RECOVERY(CCV(ccv, t_flags)); } break; case CC_ECN: /* * Save current snd_cwnd when the host encounters both * congestion recovery and fast recovery. */ CCV(ccv, snd_cwnd_prev) = win; if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) { if (V_dctcp_slowstart && dctcp_data->num_cong_events++ == 0) { CCV(ccv, snd_ssthresh) = mss * max(win / 2 / mss, 2); dctcp_data->alpha = MAX_ALPHA_VALUE; dctcp_data->bytes_ecn = 0; dctcp_data->bytes_total = 0; dctcp_data->save_sndnxt = CCV(ccv, snd_nxt); } else CCV(ccv, snd_ssthresh) = max((win - ((win * dctcp_data->alpha) >> 11)) / mss, 2) * mss; CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh); ENTER_CONGRECOVERY(CCV(ccv, t_flags)); } dctcp_data->ece_curr = 1; break; case CC_RTO: if (CCV(ccv, t_flags) & TF_ECN_PERMIT) { CCV(ccv, t_flags) |= TF_ECN_SND_CWR; dctcp_update_alpha(ccv); dctcp_data->save_sndnxt += CCV(ccv, t_maxseg); dctcp_data->num_cong_events++; } break; } }
/* * 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