diff options
Diffstat (limited to 'slirp/src/tcp_output.c')
| -rw-r--r-- | slirp/src/tcp_output.c | 524 |
1 files changed, 524 insertions, 0 deletions
diff --git a/slirp/src/tcp_output.c b/slirp/src/tcp_output.c new file mode 100644 index 0000000000..e9674df121 --- /dev/null +++ b/slirp/src/tcp_output.c @@ -0,0 +1,524 @@ +/* + * 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 uint8_t 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, tcpiph_save; + struct ip *ip; + struct ip6 *ip6; + uint8_t opt[MAX_TCPOPTLEN]; + unsigned optlen, hdrlen; + int idle, sendalot; + + DEBUG_CALL("tcp_output"); + DEBUG_ARG("tp = %p", 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", 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 < so->so_snd.sb_cc) + flags &= ~TH_FIN; + win = 1; + } else { + tp->t_timer[TCPT_PERSIST] = 0; + tp->t_rxtshift = 0; + } + } + + len = MIN(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 >= so->so_snd.sb_cc) + goto send; + if (tp->t_force) + goto send; + if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) + goto send; + if (SEQ_LT(tp->snd_nxt, tp->snd_max)) + 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((char *)(opt + 2), (char *)&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 > 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, char *) + 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((char *)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((char *)(ti + 1), (char *)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 */ + tcpiph_save = *mtod(m, struct tcpiphdr *); + + switch (so->so_ffamily) { + case AF_INET: + m->m_data += sizeof(struct tcpiphdr) - sizeof(struct tcphdr) + - sizeof(struct ip); + m->m_len -= sizeof(struct tcpiphdr) - sizeof(struct tcphdr) + - sizeof(struct ip); + ip = mtod(m, struct ip *); + + ip->ip_len = m->m_len; + ip->ip_dst = tcpiph_save.ti_dst; + ip->ip_src = tcpiph_save.ti_src; + ip->ip_p = tcpiph_save.ti_pr; + + ip->ip_ttl = IPDEFTTL; + ip->ip_tos = so->so_iptos; + error = ip_output(so, m); + break; + + case AF_INET6: + m->m_data += sizeof(struct tcpiphdr) - sizeof(struct tcphdr) + - sizeof(struct ip6); + m->m_len -= sizeof(struct tcpiphdr) - sizeof(struct tcphdr) + - sizeof(struct ip6); + ip6 = mtod(m, struct ip6 *); + + ip6->ip_pl = tcpiph_save.ti_len; + ip6->ip_dst = tcpiph_save.ti_dst6; + ip6->ip_src = tcpiph_save.ti_src6; + ip6->ip_nh = tcpiph_save.ti_nh6; + + error = ip6_output(so, m, 0); + break; + + default: + g_assert_not_reached(); + } + + 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++; +} |