diff options
Diffstat (limited to 'slirp/src/tcp_timer.c')
| -rw-r--r-- | slirp/src/tcp_timer.c | 293 |
1 files changed, 293 insertions, 0 deletions
diff --git a/slirp/src/tcp_timer.c b/slirp/src/tcp_timer.c new file mode 100644 index 0000000..7be5457 --- /dev/null +++ b/slirp/src/tcp_timer.c @@ -0,0 +1,293 @@ +/* + * 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_timer.c 8.1 (Berkeley) 6/10/93 + * tcp_timer.c,v 1.2 1994/08/02 07:49:10 davidg Exp + */ + +#include "slirp.h" + +static struct tcpcb *tcp_timers(register struct tcpcb *tp, int timer); + +/* + * Fast timeout routine for processing delayed acks + */ +void +tcp_fasttimo(Slirp *slirp) +{ + register struct socket *so; + register struct tcpcb *tp; + + DEBUG_CALL("tcp_fasttimo"); + + so = slirp->tcb.so_next; + if (so) + for (; so != &slirp->tcb; so = so->so_next) + if ((tp = (struct tcpcb *)so->so_tcpcb) && + (tp->t_flags & TF_DELACK)) { + tp->t_flags &= ~TF_DELACK; + tp->t_flags |= TF_ACKNOW; + (void) tcp_output(tp); + } +} + +/* + * Tcp protocol timeout routine called every 500 ms. + * Updates the timers in all active tcb's and + * causes finite state machine actions if timers expire. + */ +void +tcp_slowtimo(Slirp *slirp) +{ + register struct socket *ip, *ipnxt; + register struct tcpcb *tp; + register int i; + + DEBUG_CALL("tcp_slowtimo"); + + /* + * Search through tcb's and update active timers. + */ + ip = slirp->tcb.so_next; + if (ip == NULL) { + return; + } + for (; ip != &slirp->tcb; ip = ipnxt) { + ipnxt = ip->so_next; + tp = sototcpcb(ip); + if (tp == NULL) { + continue; + } + for (i = 0; i < TCPT_NTIMERS; i++) { + if (tp->t_timer[i] && --tp->t_timer[i] == 0) { + tcp_timers(tp,i); + if (ipnxt->so_prev != ip) + goto tpgone; + } + } + tp->t_idle++; + if (tp->t_rtt) + tp->t_rtt++; +tpgone: + ; + } + slirp->tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */ + slirp->tcp_now++; /* for timestamps */ +} + +/* + * Cancel all timers for TCP tp. + */ +void +tcp_canceltimers(struct tcpcb *tp) +{ + register int i; + + for (i = 0; i < TCPT_NTIMERS; i++) + tp->t_timer[i] = 0; +} + +const int tcp_backoff[TCP_MAXRXTSHIFT + 1] = + { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; + +/* + * TCP timer processing. + */ +static struct tcpcb * +tcp_timers(register struct tcpcb *tp, int timer) +{ + register int rexmt; + + DEBUG_CALL("tcp_timers"); + + switch (timer) { + + /* + * 2 MSL timeout in shutdown went off. If we're closed but + * still waiting for peer to close and connection has been idle + * too long, or if 2MSL time is up from TIME_WAIT, delete connection + * control block. Otherwise, check again in a bit. + */ + case TCPT_2MSL: + if (tp->t_state != TCPS_TIME_WAIT && + tp->t_idle <= TCP_MAXIDLE) + tp->t_timer[TCPT_2MSL] = TCPTV_KEEPINTVL; + else + tp = tcp_close(tp); + break; + + /* + * Retransmission timer went off. Message has not + * been acked within retransmit interval. Back off + * to a longer retransmit interval and retransmit one segment. + */ + case TCPT_REXMT: + + /* + * XXXXX If a packet has timed out, then remove all the queued + * packets for that session. + */ + + if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { + /* + * This is a hack to suit our terminal server here at the uni of canberra + * since they have trouble with zeroes... It usually lets them through + * unharmed, but under some conditions, it'll eat the zeros. If we + * keep retransmitting it, it'll keep eating the zeroes, so we keep + * retransmitting, and eventually the connection dies... + * (this only happens on incoming data) + * + * So, if we were gonna drop the connection from too many retransmits, + * don't... instead halve the t_maxseg, which might break up the NULLs and + * let them through + * + * *sigh* + */ + + tp->t_maxseg >>= 1; + if (tp->t_maxseg < 32) { + /* + * We tried our best, now the connection must die! + */ + tp->t_rxtshift = TCP_MAXRXTSHIFT; + tp = tcp_drop(tp, tp->t_softerror); + /* tp->t_softerror : ETIMEDOUT); */ /* XXX */ + return (tp); /* XXX */ + } + + /* + * Set rxtshift to 6, which is still at the maximum + * backoff time + */ + tp->t_rxtshift = 6; + } + rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; + TCPT_RANGESET(tp->t_rxtcur, rexmt, + (short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */ + tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; + /* + * If losing, let the lower level know and try for + * a better route. Also, if we backed off this far, + * our srtt estimate is probably bogus. Clobber it + * so we'll take the next rtt measurement as our srtt; + * move the current srtt into rttvar to keep the current + * retransmit times until then. + */ + if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { + tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); + tp->t_srtt = 0; + } + tp->snd_nxt = tp->snd_una; + /* + * If timing a segment in this window, stop the timer. + */ + tp->t_rtt = 0; + /* + * Close the congestion window down to one segment + * (we'll open it by one segment for each ack we get). + * Since we probably have a window's worth of unacked + * data accumulated, this "slow start" keeps us from + * dumping all that data as back-to-back packets (which + * might overwhelm an intermediate gateway). + * + * There are two phases to the opening: Initially we + * open by one mss on each ack. This makes the window + * size increase exponentially with time. If the + * window is larger than the path can handle, this + * exponential growth results in dropped packet(s) + * almost immediately. To get more time between + * drops but still "push" the network to take advantage + * of improving conditions, we switch from exponential + * to linear window opening at some threshold size. + * For a threshold, we use half the current window + * size, truncated to a multiple of the mss. + * + * (the minimum cwnd that will give us exponential + * growth is 2 mss. We don't allow the threshold + * to go below this.) + */ + { + unsigned win = MIN(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; + if (win < 2) + win = 2; + tp->snd_cwnd = tp->t_maxseg; + tp->snd_ssthresh = win * tp->t_maxseg; + tp->t_dupacks = 0; + } + (void) tcp_output(tp); + break; + + /* + * Persistence timer into zero window. + * Force a byte to be output, if possible. + */ + case TCPT_PERSIST: + tcp_setpersist(tp); + tp->t_force = 1; + (void) tcp_output(tp); + tp->t_force = 0; + break; + + /* + * Keep-alive timer went off; send something + * or drop connection if idle for too long. + */ + case TCPT_KEEP: + if (tp->t_state < TCPS_ESTABLISHED) + goto dropit; + + if (slirp_do_keepalive && tp->t_state <= TCPS_CLOSE_WAIT) { + if (tp->t_idle >= TCPTV_KEEP_IDLE + TCP_MAXIDLE) + goto dropit; + /* + * Send a packet designed to force a response + * if the peer is up and reachable: + * either an ACK if the connection is still alive, + * or an RST if the peer has closed the connection + * due to timeout or reboot. + * Using sequence number tp->snd_una-1 + * causes the transmitted zero-length segment + * to lie outside the receive window; + * by the protocol spec, this requires the + * correspondent TCP to respond. + */ + tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL, + tp->rcv_nxt, tp->snd_una - 1, 0, + tp->t_socket->so_ffamily); + tp->t_timer[TCPT_KEEP] = TCPTV_KEEPINTVL; + } else + tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_IDLE; + break; + + dropit: + tp = tcp_drop(tp, 0); + break; + } + + return (tp); +} |