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/*
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* Copyright (c) 1982, 1986, 1988, 1990, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)tcp_output.c 8.3 (Berkeley) 12/30/93
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* tcp_output.c,v 1.3 1994/09/15 10:36:55 davidg Exp
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*/
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/*
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* Changes and additions relating to SLiRP
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* Copyright (c) 1995 Danny Gasparovski.
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*
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* Please read the file COPYRIGHT for the
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* terms and conditions of the copyright.
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*/
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#include <slirp.h> |
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|
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static const u_char tcp_outflags[TCP_NSTATES] = { |
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TH_RST|TH_ACK, 0, TH_SYN, TH_SYN|TH_ACK,
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TH_ACK, TH_ACK, TH_FIN|TH_ACK, TH_FIN|TH_ACK, |
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TH_FIN|TH_ACK, TH_ACK, TH_ACK, |
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}; |
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#define MAX_TCPOPTLEN 32 /* max # bytes that go in options */ |
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/*
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* Tcp output routine: figure out what should be sent and send it.
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*/
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int
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tcp_output(struct tcpcb *tp)
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{
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register struct socket *so = tp->t_socket; |
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register long len, win; |
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int off, flags, error;
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register struct mbuf *m; |
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register struct tcpiphdr *ti; |
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u_char opt[MAX_TCPOPTLEN]; |
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unsigned optlen, hdrlen;
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int idle, sendalot;
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|
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DEBUG_CALL("tcp_output");
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DEBUG_ARG("tp = %lx", (long )tp); |
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|
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/*
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* Determine length of data that should be transmitted,
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* and flags that will be used.
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* If there is some data or critical controls (SYN, RST)
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* to send, then transmit; otherwise, investigate further.
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*/
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idle = (tp->snd_max == tp->snd_una); |
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if (idle && tp->t_idle >= tp->t_rxtcur)
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/*
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* We have been idle for "a while" and no acks are
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* expected to clock out any data we send --
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* slow start to get ack "clock" running again.
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*/
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tp->snd_cwnd = tp->t_maxseg; |
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again:
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sendalot = 0;
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off = tp->snd_nxt - tp->snd_una; |
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win = min(tp->snd_wnd, tp->snd_cwnd); |
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flags = tcp_outflags[tp->t_state]; |
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DEBUG_MISC((dfd, " --- tcp_output flags = 0x%x\n",flags));
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/*
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* If in persist timeout with window of 0, send 1 byte.
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* Otherwise, if window is small but nonzero
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* and timer expired, we will send what we can
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* and go to transmit state.
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*/
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if (tp->t_force) {
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if (win == 0) { |
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/*
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* If we still have some data to send, then
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* clear the FIN bit. Usually this would
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* happen below when it realizes that we
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* aren't sending all the data. However,
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* if we have exactly 1 byte of unset data,
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* then it won't clear the FIN bit below,
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* and if we are in persist state, we wind
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* up sending the packet without recording
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* that we sent the FIN bit.
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*
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* We can't just blindly clear the FIN bit,
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* because if we don't have any more data
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* to send then the probe will be the FIN
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* itself.
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*/
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if (off < so->so_snd.sb_cc)
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flags &= ~TH_FIN; |
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win = 1;
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} else {
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tp->t_timer[TCPT_PERSIST] = 0;
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tp->t_rxtshift = 0;
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} |
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} |
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len = min(so->so_snd.sb_cc, win) - off; |
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|
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if (len < 0) { |
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/*
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* If FIN has been sent but not acked,
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* but we haven't been called to retransmit,
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* len will be -1. Otherwise, window shrank
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* after we sent into it. If window shrank to 0,
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* cancel pending retransmit and pull snd_nxt
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* back to (closed) window. We will enter persist
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* state below. If the window didn't close completely,
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* just wait for an ACK.
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*/
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len = 0;
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if (win == 0) { |
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tp->t_timer[TCPT_REXMT] = 0;
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tp->snd_nxt = tp->snd_una; |
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} |
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} |
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if (len > tp->t_maxseg) {
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len = tp->t_maxseg; |
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sendalot = 1;
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} |
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if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc))
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flags &= ~TH_FIN; |
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win = sbspace(&so->so_rcv); |
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/*
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* Sender silly window avoidance. If connection is idle
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* and can send all data, a maximum segment,
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* at least a maximum default-size segment do it,
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* or are forced, do it; otherwise don't bother.
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* If peer's buffer is tiny, then send
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* when window is at least half open.
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* If retransmitting (possibly after persist timer forced us
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* to send into a small window), then must resend.
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*/
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if (len) {
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if (len == tp->t_maxseg)
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goto send;
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if ((1 || idle || tp->t_flags & TF_NODELAY) && |
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len + off >= so->so_snd.sb_cc) |
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goto send;
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if (tp->t_force)
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goto send;
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if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) |
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goto send;
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if (SEQ_LT(tp->snd_nxt, tp->snd_max))
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goto send;
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} |
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/*
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* Compare available window to amount of window
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* known to peer (as advertised window less
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* next expected input). If the difference is at least two
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* max size segments, or at least 50% of the maximum possible
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* window, then want to send a window update to peer.
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*/
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if (win > 0) { |
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/*
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* "adv" is the amount we can increase the window,
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* taking into account that we are limited by
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* TCP_MAXWIN << tp->rcv_scale.
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*/
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long adv = min(win, (long)TCP_MAXWIN << tp->rcv_scale) - |
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(tp->rcv_adv - tp->rcv_nxt); |
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if (adv >= (long) (2 * tp->t_maxseg)) |
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goto send;
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if (2 * adv >= (long) so->so_rcv.sb_datalen) |
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goto send;
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} |
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/*
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* Send if we owe peer an ACK.
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*/
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if (tp->t_flags & TF_ACKNOW)
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goto send;
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if (flags & (TH_SYN|TH_RST))
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goto send;
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if (SEQ_GT(tp->snd_up, tp->snd_una))
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goto send;
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/*
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* If our state indicates that FIN should be sent
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* and we have not yet done so, or we're retransmitting the FIN,
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* then we need to send.
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*/
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if (flags & TH_FIN &&
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((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
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goto send;
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/*
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* TCP window updates are not reliable, rather a polling protocol
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* using ``persist'' packets is used to insure receipt of window
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* updates. The three ``states'' for the output side are:
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* idle not doing retransmits or persists
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* persisting to move a small or zero window
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* (re)transmitting and thereby not persisting
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*
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* tp->t_timer[TCPT_PERSIST]
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* is set when we are in persist state.
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* tp->t_force
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* is set when we are called to send a persist packet.
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* tp->t_timer[TCPT_REXMT]
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* is set when we are retransmitting
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* The output side is idle when both timers are zero.
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*
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* If send window is too small, there is data to transmit, and no
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* retransmit or persist is pending, then go to persist state.
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* If nothing happens soon, send when timer expires:
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* if window is nonzero, transmit what we can,
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* otherwise force out a byte.
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*/
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if (so->so_snd.sb_cc && tp->t_timer[TCPT_REXMT] == 0 && |
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tp->t_timer[TCPT_PERSIST] == 0) {
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tp->t_rxtshift = 0;
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tcp_setpersist(tp); |
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} |
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/*
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* No reason to send a segment, just return.
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*/
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return (0); |
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send:
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/*
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* Before ESTABLISHED, force sending of initial options
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* unless TCP set not to do any options.
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* NOTE: we assume that the IP/TCP header plus TCP options
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* always fit in a single mbuf, leaving room for a maximum
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* link header, i.e.
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* max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MHLEN
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*/
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optlen = 0;
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hdrlen = sizeof (struct tcpiphdr); |
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if (flags & TH_SYN) {
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tp->snd_nxt = tp->iss; |
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if ((tp->t_flags & TF_NOOPT) == 0) { |
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uint16_t mss; |
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opt[0] = TCPOPT_MAXSEG;
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opt[1] = 4; |
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mss = htons((uint16_t) tcp_mss(tp, 0));
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memcpy((caddr_t)(opt + 2), (caddr_t)&mss, sizeof(mss)); |
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optlen = 4;
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} |
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} |
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hdrlen += optlen; |
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/*
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* Adjust data length if insertion of options will
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* bump the packet length beyond the t_maxseg length.
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*/
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if (len > tp->t_maxseg - optlen) {
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len = tp->t_maxseg - optlen; |
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sendalot = 1;
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} |
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/*
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* Grab a header mbuf, attaching a copy of data to
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* be transmitted, and initialize the header from
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* the template for sends on this connection.
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*/
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if (len) {
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m = m_get(so->slirp); |
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if (m == NULL) { |
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error = 1;
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goto out;
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} |
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m->m_data += IF_MAXLINKHDR; |
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m->m_len = hdrlen; |
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sbcopy(&so->so_snd, off, (int) len, mtod(m, caddr_t) + hdrlen);
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m->m_len += len; |
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|
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/*
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* If we're sending everything we've got, set PUSH.
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* (This will keep happy those implementations which only
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* give data to the user when a buffer fills or
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* a PUSH comes in.)
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*/
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if (off + len == so->so_snd.sb_cc)
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flags |= TH_PUSH; |
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} else {
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m = m_get(so->slirp); |
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if (m == NULL) { |
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error = 1;
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goto out;
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} |
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m->m_data += IF_MAXLINKHDR; |
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m->m_len = hdrlen; |
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} |
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|
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ti = mtod(m, struct tcpiphdr *);
|
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|
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memcpy((caddr_t)ti, &tp->t_template, sizeof (struct tcpiphdr)); |
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|
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/*
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* Fill in fields, remembering maximum advertised
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* window for use in delaying messages about window sizes.
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* If resending a FIN, be sure not to use a new sequence number.
|
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*/
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if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
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tp->snd_nxt == tp->snd_max) |
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tp->snd_nxt--; |
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/*
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* If we are doing retransmissions, then snd_nxt will
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* not reflect the first unsent octet. For ACK only
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* packets, we do not want the sequence number of the
|
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* retransmitted packet, we want the sequence number
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* of the next unsent octet. So, if there is no data
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* (and no SYN or FIN), use snd_max instead of snd_nxt
|
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* when filling in ti_seq. But if we are in persist
|
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* state, snd_max might reflect one byte beyond the
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* right edge of the window, so use snd_nxt in that
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* case, since we know we aren't doing a retransmission.
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* (retransmit and persist are mutually exclusive...)
|
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*/
|
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if (len || (flags & (TH_SYN|TH_FIN)) || tp->t_timer[TCPT_PERSIST])
|
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ti->ti_seq = htonl(tp->snd_nxt); |
| 349 |
else
|
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ti->ti_seq = htonl(tp->snd_max); |
| 351 |
ti->ti_ack = htonl(tp->rcv_nxt); |
| 352 |
if (optlen) {
|
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memcpy((caddr_t)(ti + 1), (caddr_t)opt, optlen);
|
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ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2; |
| 355 |
} |
| 356 |
ti->ti_flags = flags; |
| 357 |
/*
|
| 358 |
* Calculate receive window. Don't shrink window,
|
| 359 |
* but avoid silly window syndrome.
|
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*/
|
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if (win < (long)(so->so_rcv.sb_datalen / 4) && win < (long)tp->t_maxseg) |
| 362 |
win = 0;
|
| 363 |
if (win > (long)TCP_MAXWIN << tp->rcv_scale) |
| 364 |
win = (long)TCP_MAXWIN << tp->rcv_scale;
|
| 365 |
if (win < (long)(tp->rcv_adv - tp->rcv_nxt)) |
| 366 |
win = (long)(tp->rcv_adv - tp->rcv_nxt);
|
| 367 |
ti->ti_win = htons((uint16_t) (win>>tp->rcv_scale)); |
| 368 |
|
| 369 |
if (SEQ_GT(tp->snd_up, tp->snd_una)) {
|
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ti->ti_urp = htons((uint16_t)(tp->snd_up - ntohl(ti->ti_seq))); |
| 371 |
ti->ti_flags |= TH_URG; |
| 372 |
} else
|
| 373 |
/*
|
| 374 |
* If no urgent pointer to send, then we pull
|
| 375 |
* the urgent pointer to the left edge of the send window
|
| 376 |
* so that it doesn't drift into the send window on sequence
|
| 377 |
* number wraparound.
|
| 378 |
*/
|
| 379 |
tp->snd_up = tp->snd_una; /* drag it along */
|
| 380 |
|
| 381 |
/*
|
| 382 |
* Put TCP length in extended header, and then
|
| 383 |
* checksum extended header and data.
|
| 384 |
*/
|
| 385 |
if (len + optlen)
|
| 386 |
ti->ti_len = htons((uint16_t)(sizeof (struct tcphdr) + |
| 387 |
optlen + len)); |
| 388 |
ti->ti_sum = cksum(m, (int)(hdrlen + len));
|
| 389 |
|
| 390 |
/*
|
| 391 |
* In transmit state, time the transmission and arrange for
|
| 392 |
* the retransmit. In persist state, just set snd_max.
|
| 393 |
*/
|
| 394 |
if (tp->t_force == 0 || tp->t_timer[TCPT_PERSIST] == 0) { |
| 395 |
tcp_seq startseq = tp->snd_nxt; |
| 396 |
|
| 397 |
/*
|
| 398 |
* Advance snd_nxt over sequence space of this segment.
|
| 399 |
*/
|
| 400 |
if (flags & (TH_SYN|TH_FIN)) {
|
| 401 |
if (flags & TH_SYN)
|
| 402 |
tp->snd_nxt++; |
| 403 |
if (flags & TH_FIN) {
|
| 404 |
tp->snd_nxt++; |
| 405 |
tp->t_flags |= TF_SENTFIN; |
| 406 |
} |
| 407 |
} |
| 408 |
tp->snd_nxt += len; |
| 409 |
if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
|
| 410 |
tp->snd_max = tp->snd_nxt; |
| 411 |
/*
|
| 412 |
* Time this transmission if not a retransmission and
|
| 413 |
* not currently timing anything.
|
| 414 |
*/
|
| 415 |
if (tp->t_rtt == 0) { |
| 416 |
tp->t_rtt = 1;
|
| 417 |
tp->t_rtseq = startseq; |
| 418 |
} |
| 419 |
} |
| 420 |
|
| 421 |
/*
|
| 422 |
* Set retransmit timer if not currently set,
|
| 423 |
* and not doing an ack or a keep-alive probe.
|
| 424 |
* Initial value for retransmit timer is smoothed
|
| 425 |
* round-trip time + 2 * round-trip time variance.
|
| 426 |
* Initialize shift counter which is used for backoff
|
| 427 |
* of retransmit time.
|
| 428 |
*/
|
| 429 |
if (tp->t_timer[TCPT_REXMT] == 0 && |
| 430 |
tp->snd_nxt != tp->snd_una) {
|
| 431 |
tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; |
| 432 |
if (tp->t_timer[TCPT_PERSIST]) {
|
| 433 |
tp->t_timer[TCPT_PERSIST] = 0;
|
| 434 |
tp->t_rxtshift = 0;
|
| 435 |
} |
| 436 |
} |
| 437 |
} else
|
| 438 |
if (SEQ_GT(tp->snd_nxt + len, tp->snd_max))
|
| 439 |
tp->snd_max = tp->snd_nxt + len; |
| 440 |
|
| 441 |
/*
|
| 442 |
* Fill in IP length and desired time to live and
|
| 443 |
* send to IP level. There should be a better way
|
| 444 |
* to handle ttl and tos; we could keep them in
|
| 445 |
* the template, but need a way to checksum without them.
|
| 446 |
*/
|
| 447 |
m->m_len = hdrlen + len; /* XXX Needed? m_len should be correct */
|
| 448 |
|
| 449 |
{
|
| 450 |
|
| 451 |
((struct ip *)ti)->ip_len = m->m_len;
|
| 452 |
|
| 453 |
((struct ip *)ti)->ip_ttl = IPDEFTTL;
|
| 454 |
((struct ip *)ti)->ip_tos = so->so_iptos;
|
| 455 |
|
| 456 |
error = ip_output(so, m); |
| 457 |
} |
| 458 |
if (error) {
|
| 459 |
out:
|
| 460 |
return (error);
|
| 461 |
} |
| 462 |
|
| 463 |
/*
|
| 464 |
* Data sent (as far as we can tell).
|
| 465 |
* If this advertises a larger window than any other segment,
|
| 466 |
* then remember the size of the advertised window.
|
| 467 |
* Any pending ACK has now been sent.
|
| 468 |
*/
|
| 469 |
if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) |
| 470 |
tp->rcv_adv = tp->rcv_nxt + win; |
| 471 |
tp->last_ack_sent = tp->rcv_nxt; |
| 472 |
tp->t_flags &= ~(TF_ACKNOW|TF_DELACK); |
| 473 |
if (sendalot)
|
| 474 |
goto again;
|
| 475 |
|
| 476 |
return (0); |
| 477 |
} |
| 478 |
|
| 479 |
void
|
| 480 |
tcp_setpersist(struct tcpcb *tp)
|
| 481 |
{
|
| 482 |
int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; |
| 483 |
|
| 484 |
/*
|
| 485 |
* Start/restart persistence timer.
|
| 486 |
*/
|
| 487 |
TCPT_RANGESET(tp->t_timer[TCPT_PERSIST], |
| 488 |
t * tcp_backoff[tp->t_rxtshift], |
| 489 |
TCPTV_PERSMIN, TCPTV_PERSMAX); |
| 490 |
if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
|
| 491 |
tp->t_rxtshift++; |
| 492 |
} |