| /* | |
| * Copyright (c) 1982, 1986, 1988, 1990, 1993 | |
| * 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. 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 8.3 (Berkeley) 12/30/93 | |
| * tcp_output.c,v 1.3 1994/09/15 10:36:55 davidg Exp | |
| */ | |
| /* | |
| * Changes and additions relating to SLiRP | |
| * Copyright (c) 1995 Danny Gasparovski. | |
| * | |
| * Please read the file COPYRIGHT for the | |
| * terms and conditions of the copyright. | |
| */ | |
| #include <slirp.h> | |
| static const u_char tcp_outflags[TCP_NSTATES] = { | |
| TH_RST|TH_ACK, 0, TH_SYN, TH_SYN|TH_ACK, | |
| TH_ACK, TH_ACK, TH_FIN|TH_ACK, TH_FIN|TH_ACK, | |
| TH_FIN|TH_ACK, TH_ACK, TH_ACK, | |
| }; | |
| #undef MAX_TCPOPTLEN | |
| #define MAX_TCPOPTLEN 32 /* max # bytes that go in options */ | |
| /* | |
| * Tcp output routine: figure out what should be sent and send it. | |
| */ | |
| int | |
| tcp_output(struct tcpcb *tp) | |
| { | |
| register struct socket *so = tp->t_socket; | |
| register long len, win; | |
| int off, flags, error; | |
| register struct mbuf *m; | |
| register struct tcpiphdr *ti; | |
| u_char opt[MAX_TCPOPTLEN]; | |
| unsigned optlen, hdrlen; | |
| int idle, sendalot; | |
| DEBUG_CALL("tcp_output"); | |
| DEBUG_ARG("tp = %lx", (long )tp); | |
| /* | |
| * 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->snd_max == tp->snd_una); | |
| if (idle && tp->t_idle >= 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. | |
| */ | |
| tp->snd_cwnd = tp->t_maxseg; | |
| again: | |
| sendalot = 0; | |
| off = tp->snd_nxt - tp->snd_una; | |
| win = min(tp->snd_wnd, tp->snd_cwnd); | |
| flags = tcp_outflags[tp->t_state]; | |
| DEBUG_MISC(" --- tcp_output flags = 0x%x\n",flags); | |
| /* | |
| * 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 (win == 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 unset 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 < (int)so->so_snd.sb_cc) | |
| flags &= ~TH_FIN; | |
| win = 1; | |
| } else { | |
| tp->t_timer[TCPT_PERSIST] = 0; | |
| tp->t_rxtshift = 0; | |
| } | |
| } | |
| len = min((long)so->so_snd.sb_cc, win) - off; | |
| if (len < 0) { | |
| /* | |
| * If FIN has been sent but not acked, | |
| * but we haven't been called to retransmit, | |
| * len will be -1. Otherwise, window shrank | |
| * after we sent into it. If window shrank to 0, | |
| * cancel pending retransmit and pull snd_nxt | |
| * back to (closed) window. We will enter persist | |
| * state below. If the window didn't close completely, | |
| * just wait for an ACK. | |
| */ | |
| len = 0; | |
| if (win == 0) { | |
| tp->t_timer[TCPT_REXMT] = 0; | |
| tp->snd_nxt = tp->snd_una; | |
| } | |
| } | |
| if (len > tp->t_maxseg) { | |
| len = tp->t_maxseg; | |
| sendalot = 1; | |
| } | |
| if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) | |
| flags &= ~TH_FIN; | |
| win = sbspace(&so->so_rcv); | |
| /* | |
| * Sender silly window avoidance. If connection is idle | |
| * and can send all data, a maximum segment, | |
| * at least a maximum default-size segment do it, | |
| * or are forced, do it; otherwise don't bother. | |
| * If peer's buffer is tiny, then send | |
| * when window is at least half open. | |
| * If retransmitting (possibly after persist timer forced us | |
| * to send into a small window), then must resend. | |
| */ | |
| if (len) { | |
| if (len == tp->t_maxseg) | |
| goto send; | |
| if ((1 || idle || (tp->t_flags & TF_NODELAY)) && | |
| ((len + off) >= (long)so->so_snd.sb_cc)) | |
| goto send; | |
| if (tp->t_force) | |
| goto send; | |
| if ((len >= (long)(tp->max_sndwnd / 2)) && (tp->max_sndwnd > 0)) | |
| goto send; | |
| if (SEQ_LT(tp->snd_nxt, tp->snd_max)) | |
| 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 (win > 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(win, (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_datalen) | |
| goto send; | |
| } | |
| /* | |
| * Send if we owe peer an ACK. | |
| */ | |
| if (tp->t_flags & TF_ACKNOW) | |
| goto send; | |
| if (flags & (TH_SYN|TH_RST)) | |
| 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, or we're retransmitting the FIN, | |
| * then we need to send. | |
| */ | |
| if (flags & TH_FIN && | |
| ((tp->t_flags & TF_SENTFIN) == 0 || 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 | |
| * | |
| * 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); | |
| } | |
| /* | |
| * 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 <= MHLEN | |
| */ | |
| optlen = 0; | |
| hdrlen = sizeof (struct tcpiphdr); | |
| if (flags & TH_SYN) { | |
| tp->snd_nxt = tp->iss; | |
| if ((tp->t_flags & TF_NOOPT) == 0) { | |
| uint16_t mss; | |
| opt[0] = TCPOPT_MAXSEG; | |
| opt[1] = 4; | |
| mss = htons((uint16_t) tcp_mss(tp, 0)); | |
| memcpy((caddr_t)(opt + 2), (caddr_t)&mss, sizeof(mss)); | |
| optlen = 4; | |
| } | |
| } | |
| hdrlen += optlen; | |
| /* | |
| * Adjust data length if insertion of options will | |
| * bump the packet length beyond the t_maxseg length. | |
| */ | |
| if (len > (long)(tp->t_maxseg - optlen)) { | |
| len = tp->t_maxseg - optlen; | |
| sendalot = 1; | |
| } | |
| /* | |
| * 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) { | |
| m = m_get(so->slirp); | |
| if (m == NULL) { | |
| error = 1; | |
| goto out; | |
| } | |
| m->m_data += IF_MAXLINKHDR; | |
| m->m_len = hdrlen; | |
| sbcopy(&so->so_snd, off, (int) len, mtod(m, caddr_t) + hdrlen); | |
| m->m_len += len; | |
| /* | |
| * 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 { | |
| m = m_get(so->slirp); | |
| if (m == NULL) { | |
| error = 1; | |
| goto out; | |
| } | |
| m->m_data += IF_MAXLINKHDR; | |
| m->m_len = hdrlen; | |
| } | |
| ti = mtod(m, struct tcpiphdr *); | |
| memcpy((caddr_t)ti, &tp->t_template, sizeof (struct tcpiphdr)); | |
| /* | |
| * 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 (len || (flags & (TH_SYN|TH_FIN)) || tp->t_timer[TCPT_PERSIST]) | |
| ti->ti_seq = htonl(tp->snd_nxt); | |
| else | |
| ti->ti_seq = htonl(tp->snd_max); | |
| ti->ti_ack = htonl(tp->rcv_nxt); | |
| if (optlen) { | |
| memcpy((caddr_t)(ti + 1), (caddr_t)opt, optlen); | |
| ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2; | |
| } | |
| ti->ti_flags = flags; | |
| /* | |
| * Calculate receive window. Don't shrink window, | |
| * but avoid silly window syndrome. | |
| */ | |
| if (win < (long)(so->so_rcv.sb_datalen / 4) && win < (long)tp->t_maxseg) | |
| win = 0; | |
| if (win > (long)TCP_MAXWIN << tp->rcv_scale) | |
| win = (long)TCP_MAXWIN << tp->rcv_scale; | |
| if (win < (long)(tp->rcv_adv - tp->rcv_nxt)) | |
| win = (long)(tp->rcv_adv - tp->rcv_nxt); | |
| ti->ti_win = htons((uint16_t) (win>>tp->rcv_scale)); | |
| if (SEQ_GT(tp->snd_up, tp->snd_una)) { | |
| ti->ti_urp = htons((uint16_t)(tp->snd_up - ntohl(ti->ti_seq))); | |
| ti->ti_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. | |
| */ | |
| if (len + optlen) | |
| ti->ti_len = htons((uint16_t)(sizeof (struct tcphdr) + | |
| optlen + len)); | |
| ti->ti_sum = cksum(m, (int)(hdrlen + 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; | |
| } | |
| } | |
| 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_rtt == 0) { | |
| tp->t_rtt = 1; | |
| tp->t_rtseq = startseq; | |
| } | |
| } | |
| /* | |
| * 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. | |
| */ | |
| if (tp->t_timer[TCPT_REXMT] == 0 && | |
| tp->snd_nxt != tp->snd_una) { | |
| tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; | |
| if (tp->t_timer[TCPT_PERSIST]) { | |
| tp->t_timer[TCPT_PERSIST] = 0; | |
| tp->t_rxtshift = 0; | |
| } | |
| } | |
| } else | |
| if (SEQ_GT(tp->snd_nxt + len, tp->snd_max)) | |
| tp->snd_max = tp->snd_nxt + len; | |
| /* | |
| * 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_len = hdrlen + len; /* XXX Needed? m_len should be correct */ | |
| { | |
| ((struct ip *)ti)->ip_len = m->m_len; | |
| ((struct ip *)ti)->ip_ttl = IPDEFTTL; | |
| ((struct ip *)ti)->ip_tos = so->so_iptos; | |
| error = ip_output(so, m); | |
| } | |
| if (error) { | |
| out: | |
| return (error); | |
| } | |
| /* | |
| * 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 (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) | |
| tp->rcv_adv = tp->rcv_nxt + win; | |
| tp->last_ack_sent = tp->rcv_nxt; | |
| tp->t_flags &= ~(TF_ACKNOW|TF_DELACK); | |
| if (sendalot) | |
| goto again; | |
| return (0); | |
| } | |
| void | |
| tcp_setpersist(struct tcpcb *tp) | |
| { | |
| int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; | |
| /* | |
| * Start/restart persistence 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++; | |
| } |