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/*
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* Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994
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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. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. 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_input.c 8.5 (Berkeley) 4/10/94
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* tcp_input.c,v 1.10 1994/10/13 18:36:32 wollman 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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#include "ip_icmp.h" |
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struct socket tcb;
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#define TCPREXMTTHRESH 3 |
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struct socket *tcp_last_so = &tcb;
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tcp_seq tcp_iss; /* tcp initial send seq # */
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#define TCP_PAWS_IDLE (24 * 24 * 60 * 60 * PR_SLOWHZ) |
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/* for modulo comparisons of timestamps */
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#define TSTMP_LT(a,b) ((int)((a)-(b)) < 0) |
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#define TSTMP_GEQ(a,b) ((int)((a)-(b)) >= 0) |
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/*
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* Insert segment ti into reassembly queue of tcp with
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* control block tp. Return TH_FIN if reassembly now includes
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* a segment with FIN. The macro form does the common case inline
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* (segment is the next to be received on an established connection,
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* and the queue is empty), avoiding linkage into and removal
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* from the queue and repetition of various conversions.
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* Set DELACK for segments received in order, but ack immediately
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* when segments are out of order (so fast retransmit can work).
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*/
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#ifdef TCP_ACK_HACK
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#define TCP_REASS(tp, ti, m, so, flags) {\
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if ((ti)->ti_seq == (tp)->rcv_nxt && \
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(tp)->seg_next == (tcpiphdrp_32)(tp) && \ |
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(tp)->t_state == TCPS_ESTABLISHED) {\ |
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if (ti->ti_flags & TH_PUSH) \
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tp->t_flags |= TF_ACKNOW; \ |
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else \
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tp->t_flags |= TF_DELACK; \ |
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(tp)->rcv_nxt += (ti)->ti_len; \ |
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flags = (ti)->ti_flags & TH_FIN; \ |
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STAT(tcpstat.tcps_rcvpack++); \ |
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STAT(tcpstat.tcps_rcvbyte += (ti)->ti_len); \ |
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if (so->so_emu) { \
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if (tcp_emu((so),(m))) sbappend((so), (m)); \
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} else \
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sbappend((so), (m)); \ |
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/* sorwakeup(so); */ \
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} else {\
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(flags) = tcp_reass((tp), (ti), (m)); \ |
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tp->t_flags |= TF_ACKNOW; \ |
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} \ |
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} |
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#else
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#define TCP_REASS(tp, ti, m, so, flags) { \
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if ((ti)->ti_seq == (tp)->rcv_nxt && \
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(tp)->seg_next == (tcpiphdrp_32)(tp) && \ |
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(tp)->t_state == TCPS_ESTABLISHED) { \ |
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tp->t_flags |= TF_DELACK; \ |
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(tp)->rcv_nxt += (ti)->ti_len; \ |
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flags = (ti)->ti_flags & TH_FIN; \ |
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STAT(tcpstat.tcps_rcvpack++); \ |
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STAT(tcpstat.tcps_rcvbyte += (ti)->ti_len); \ |
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if (so->so_emu) { \
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if (tcp_emu((so),(m))) sbappend(so, (m)); \
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} else \
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sbappend((so), (m)); \ |
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/* sorwakeup(so); */ \
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} else { \
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(flags) = tcp_reass((tp), (ti), (m)); \ |
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tp->t_flags |= TF_ACKNOW; \ |
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} \ |
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} |
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#endif
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static void tcp_dooptions(struct tcpcb *tp, u_char *cp, int cnt, |
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struct tcpiphdr *ti);
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static void tcp_xmit_timer(register struct tcpcb *tp, int rtt); |
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static int |
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tcp_reass(register struct tcpcb *tp, register struct tcpiphdr *ti, |
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struct mbuf *m)
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{ |
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register struct tcpiphdr *q; |
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struct socket *so = tp->t_socket;
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int flags;
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/*
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* Call with ti==0 after become established to
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* force pre-ESTABLISHED data up to user socket.
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*/
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if (ti == 0) |
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goto present;
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/*
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* Find a segment which begins after this one does.
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*/
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for (q = (struct tcpiphdr *)tp->seg_next; q != (struct tcpiphdr *)tp; |
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q = (struct tcpiphdr *)q->ti_next)
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if (SEQ_GT(q->ti_seq, ti->ti_seq))
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break;
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/*
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* If there is a preceding segment, it may provide some of
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* our data already. If so, drop the data from the incoming
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* segment. If it provides all of our data, drop us.
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*/
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if ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) { |
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register int i; |
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q = (struct tcpiphdr *)q->ti_prev;
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/* conversion to int (in i) handles seq wraparound */
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i = q->ti_seq + q->ti_len - ti->ti_seq; |
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if (i > 0) { |
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if (i >= ti->ti_len) {
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STAT(tcpstat.tcps_rcvduppack++); |
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STAT(tcpstat.tcps_rcvdupbyte += ti->ti_len); |
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m_freem(m); |
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/*
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* Try to present any queued data
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* at the left window edge to the user.
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* This is needed after the 3-WHS
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* completes.
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*/
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goto present; /* ??? */ |
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} |
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m_adj(m, i); |
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ti->ti_len -= i; |
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ti->ti_seq += i; |
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} |
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q = (struct tcpiphdr *)(q->ti_next);
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} |
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STAT(tcpstat.tcps_rcvoopack++); |
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STAT(tcpstat.tcps_rcvoobyte += ti->ti_len); |
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REASS_MBUF(ti) = (mbufp_32) m; /* XXX */
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/*
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* While we overlap succeeding segments trim them or,
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* if they are completely covered, dequeue them.
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*/
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while (q != (struct tcpiphdr *)tp) { |
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register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq; |
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if (i <= 0) |
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break;
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if (i < q->ti_len) {
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q->ti_seq += i; |
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q->ti_len -= i; |
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m_adj((struct mbuf *) REASS_MBUF(q), i);
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break;
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} |
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q = (struct tcpiphdr *)q->ti_next;
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m = (struct mbuf *) REASS_MBUF((struct tcpiphdr *)q->ti_prev); |
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remque_32((void *)(q->ti_prev));
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m_freem(m); |
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} |
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/*
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* Stick new segment in its place.
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*/
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insque_32(ti, (void *)(q->ti_prev));
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present:
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/*
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* Present data to user, advancing rcv_nxt through
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* completed sequence space.
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*/
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if (!TCPS_HAVEESTABLISHED(tp->t_state))
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return (0); |
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ti = (struct tcpiphdr *) tp->seg_next;
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if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt) |
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return (0); |
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if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len)
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return (0); |
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do {
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tp->rcv_nxt += ti->ti_len; |
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flags = ti->ti_flags & TH_FIN; |
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remque_32(ti); |
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m = (struct mbuf *) REASS_MBUF(ti); /* XXX */ |
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ti = (struct tcpiphdr *)ti->ti_next;
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/* if (so->so_state & SS_FCANTRCVMORE) */
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if (so->so_state & SS_FCANTSENDMORE)
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m_freem(m); |
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else {
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if (so->so_emu) {
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if (tcp_emu(so,m)) sbappend(so, m);
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} else
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sbappend(so, m); |
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} |
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} while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt); |
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/* sorwakeup(so); */
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return (flags);
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} |
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/*
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* TCP input routine, follows pages 65-76 of the
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* protocol specification dated September, 1981 very closely.
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*/
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void
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tcp_input(m, iphlen, inso) |
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register struct mbuf *m; |
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int iphlen;
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struct socket *inso;
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{ |
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struct ip save_ip, *ip;
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register struct tcpiphdr *ti; |
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caddr_t optp = NULL;
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int optlen = 0; |
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int len, tlen, off;
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register struct tcpcb *tp = 0; |
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register int tiflags; |
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struct socket *so = 0; |
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int todrop, acked, ourfinisacked, needoutput = 0; |
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/* int dropsocket = 0; */
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int iss = 0; |
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u_long tiwin; |
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int ret;
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/* int ts_present = 0; */
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DEBUG_CALL("tcp_input");
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DEBUG_ARGS((dfd," m = %8lx iphlen = %2d inso = %lx\n",
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(long )m, iphlen, (long )inso )); |
260 |
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/*
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* If called with m == 0, then we're continuing the connect
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*/
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if (m == NULL) { |
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so = inso; |
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/* Re-set a few variables */
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tp = sototcpcb(so); |
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m = so->so_m; |
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so->so_m = 0;
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ti = so->so_ti; |
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tiwin = ti->ti_win; |
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tiflags = ti->ti_flags; |
274 |
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goto cont_conn;
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} |
277 |
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278 |
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STAT(tcpstat.tcps_rcvtotal++); |
280 |
/*
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* Get IP and TCP header together in first mbuf.
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* Note: IP leaves IP header in first mbuf.
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*/
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ti = mtod(m, struct tcpiphdr *);
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if (iphlen > sizeof(struct ip )) { |
286 |
ip_stripoptions(m, (struct mbuf *)0); |
287 |
iphlen=sizeof(struct ip ); |
288 |
} |
289 |
/* XXX Check if too short */
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290 |
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291 |
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/*
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* Save a copy of the IP header in case we want restore it
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* for sending an ICMP error message in response.
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*/
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ip=mtod(m, struct ip *);
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save_ip = *ip; |
298 |
save_ip.ip_len+= iphlen; |
299 |
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/*
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* Checksum extended TCP header and data.
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*/
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tlen = ((struct ip *)ti)->ip_len;
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ti->ti_next = ti->ti_prev = 0;
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305 |
ti->ti_x1 = 0;
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306 |
ti->ti_len = htons((u_int16_t)tlen); |
307 |
len = sizeof(struct ip ) + tlen; |
308 |
/* keep checksum for ICMP reply
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309 |
* ti->ti_sum = cksum(m, len);
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310 |
* if (ti->ti_sum) { */
|
311 |
if(cksum(m, len)) {
|
312 |
STAT(tcpstat.tcps_rcvbadsum++); |
313 |
goto drop;
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314 |
} |
315 |
|
316 |
/*
|
317 |
* Check that TCP offset makes sense,
|
318 |
* pull out TCP options and adjust length. XXX
|
319 |
*/
|
320 |
off = ti->ti_off << 2;
|
321 |
if (off < sizeof (struct tcphdr) || off > tlen) { |
322 |
STAT(tcpstat.tcps_rcvbadoff++); |
323 |
goto drop;
|
324 |
} |
325 |
tlen -= off; |
326 |
ti->ti_len = tlen; |
327 |
if (off > sizeof (struct tcphdr)) { |
328 |
optlen = off - sizeof (struct tcphdr); |
329 |
optp = mtod(m, caddr_t) + sizeof (struct tcpiphdr); |
330 |
|
331 |
/*
|
332 |
* Do quick retrieval of timestamp options ("options
|
333 |
* prediction?"). If timestamp is the only option and it's
|
334 |
* formatted as recommended in RFC 1323 appendix A, we
|
335 |
* quickly get the values now and not bother calling
|
336 |
* tcp_dooptions(), etc.
|
337 |
*/
|
338 |
/* if ((optlen == TCPOLEN_TSTAMP_APPA ||
|
339 |
* (optlen > TCPOLEN_TSTAMP_APPA &&
|
340 |
* optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) &&
|
341 |
* *(u_int32_t *)optp == htonl(TCPOPT_TSTAMP_HDR) &&
|
342 |
* (ti->ti_flags & TH_SYN) == 0) {
|
343 |
* ts_present = 1;
|
344 |
* ts_val = ntohl(*(u_int32_t *)(optp + 4));
|
345 |
* ts_ecr = ntohl(*(u_int32_t *)(optp + 8));
|
346 |
* optp = NULL; / * we've parsed the options * /
|
347 |
* }
|
348 |
*/
|
349 |
} |
350 |
tiflags = ti->ti_flags; |
351 |
|
352 |
/*
|
353 |
* Convert TCP protocol specific fields to host format.
|
354 |
*/
|
355 |
NTOHL(ti->ti_seq); |
356 |
NTOHL(ti->ti_ack); |
357 |
NTOHS(ti->ti_win); |
358 |
NTOHS(ti->ti_urp); |
359 |
|
360 |
/*
|
361 |
* Drop TCP, IP headers and TCP options.
|
362 |
*/
|
363 |
m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); |
364 |
m->m_len -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); |
365 |
|
366 |
/*
|
367 |
* Locate pcb for segment.
|
368 |
*/
|
369 |
findso:
|
370 |
so = tcp_last_so; |
371 |
if (so->so_fport != ti->ti_dport ||
|
372 |
so->so_lport != ti->ti_sport || |
373 |
so->so_laddr.s_addr != ti->ti_src.s_addr || |
374 |
so->so_faddr.s_addr != ti->ti_dst.s_addr) { |
375 |
so = solookup(&tcb, ti->ti_src, ti->ti_sport, |
376 |
ti->ti_dst, ti->ti_dport); |
377 |
if (so)
|
378 |
tcp_last_so = so; |
379 |
STAT(tcpstat.tcps_socachemiss++); |
380 |
} |
381 |
|
382 |
/*
|
383 |
* If the state is CLOSED (i.e., TCB does not exist) then
|
384 |
* all data in the incoming segment is discarded.
|
385 |
* If the TCB exists but is in CLOSED state, it is embryonic,
|
386 |
* but should either do a listen or a connect soon.
|
387 |
*
|
388 |
* state == CLOSED means we've done socreate() but haven't
|
389 |
* attached it to a protocol yet...
|
390 |
*
|
391 |
* XXX If a TCB does not exist, and the TH_SYN flag is
|
392 |
* the only flag set, then create a session, mark it
|
393 |
* as if it was LISTENING, and continue...
|
394 |
*/
|
395 |
if (so == 0) { |
396 |
if ((tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) != TH_SYN)
|
397 |
goto dropwithreset;
|
398 |
|
399 |
if ((so = socreate()) == NULL) |
400 |
goto dropwithreset;
|
401 |
if (tcp_attach(so) < 0) { |
402 |
free(so); /* Not sofree (if it failed, it's not insqued) */
|
403 |
goto dropwithreset;
|
404 |
} |
405 |
|
406 |
sbreserve(&so->so_snd, TCP_SNDSPACE); |
407 |
sbreserve(&so->so_rcv, TCP_RCVSPACE); |
408 |
|
409 |
/* tcp_last_so = so; */ /* XXX ? */ |
410 |
/* tp = sototcpcb(so); */
|
411 |
|
412 |
so->so_laddr = ti->ti_src; |
413 |
so->so_lport = ti->ti_sport; |
414 |
so->so_faddr = ti->ti_dst; |
415 |
so->so_fport = ti->ti_dport; |
416 |
|
417 |
if ((so->so_iptos = tcp_tos(so)) == 0) |
418 |
so->so_iptos = ((struct ip *)ti)->ip_tos;
|
419 |
|
420 |
tp = sototcpcb(so); |
421 |
tp->t_state = TCPS_LISTEN; |
422 |
} |
423 |
|
424 |
/*
|
425 |
* If this is a still-connecting socket, this probably
|
426 |
* a retransmit of the SYN. Whether it's a retransmit SYN
|
427 |
* or something else, we nuke it.
|
428 |
*/
|
429 |
if (so->so_state & SS_ISFCONNECTING)
|
430 |
goto drop;
|
431 |
|
432 |
tp = sototcpcb(so); |
433 |
|
434 |
/* XXX Should never fail */
|
435 |
if (tp == 0) |
436 |
goto dropwithreset;
|
437 |
if (tp->t_state == TCPS_CLOSED)
|
438 |
goto drop;
|
439 |
|
440 |
/* Unscale the window into a 32-bit value. */
|
441 |
/* if ((tiflags & TH_SYN) == 0)
|
442 |
* tiwin = ti->ti_win << tp->snd_scale;
|
443 |
* else
|
444 |
*/
|
445 |
tiwin = ti->ti_win; |
446 |
|
447 |
/*
|
448 |
* Segment received on connection.
|
449 |
* Reset idle time and keep-alive timer.
|
450 |
*/
|
451 |
tp->t_idle = 0;
|
452 |
if (SO_OPTIONS)
|
453 |
tp->t_timer[TCPT_KEEP] = TCPTV_KEEPINTVL; |
454 |
else
|
455 |
tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_IDLE; |
456 |
|
457 |
/*
|
458 |
* Process options if not in LISTEN state,
|
459 |
* else do it below (after getting remote address).
|
460 |
*/
|
461 |
if (optp && tp->t_state != TCPS_LISTEN)
|
462 |
tcp_dooptions(tp, (u_char *)optp, optlen, ti); |
463 |
/* , */
|
464 |
/* &ts_present, &ts_val, &ts_ecr); */
|
465 |
|
466 |
/*
|
467 |
* Header prediction: check for the two common cases
|
468 |
* of a uni-directional data xfer. If the packet has
|
469 |
* no control flags, is in-sequence, the window didn't
|
470 |
* change and we're not retransmitting, it's a
|
471 |
* candidate. If the length is zero and the ack moved
|
472 |
* forward, we're the sender side of the xfer. Just
|
473 |
* free the data acked & wake any higher level process
|
474 |
* that was blocked waiting for space. If the length
|
475 |
* is non-zero and the ack didn't move, we're the
|
476 |
* receiver side. If we're getting packets in-order
|
477 |
* (the reassembly queue is empty), add the data to
|
478 |
* the socket buffer and note that we need a delayed ack.
|
479 |
*
|
480 |
* XXX Some of these tests are not needed
|
481 |
* eg: the tiwin == tp->snd_wnd prevents many more
|
482 |
* predictions.. with no *real* advantage..
|
483 |
*/
|
484 |
if (tp->t_state == TCPS_ESTABLISHED &&
|
485 |
(tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && |
486 |
/* (!ts_present || TSTMP_GEQ(ts_val, tp->ts_recent)) && */
|
487 |
ti->ti_seq == tp->rcv_nxt && |
488 |
tiwin && tiwin == tp->snd_wnd && |
489 |
tp->snd_nxt == tp->snd_max) { |
490 |
/*
|
491 |
* If last ACK falls within this segment's sequence numbers,
|
492 |
* record the timestamp.
|
493 |
*/
|
494 |
/* if (ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) &&
|
495 |
* SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len)) {
|
496 |
* tp->ts_recent_age = tcp_now;
|
497 |
* tp->ts_recent = ts_val;
|
498 |
* }
|
499 |
*/
|
500 |
if (ti->ti_len == 0) { |
501 |
if (SEQ_GT(ti->ti_ack, tp->snd_una) &&
|
502 |
SEQ_LEQ(ti->ti_ack, tp->snd_max) && |
503 |
tp->snd_cwnd >= tp->snd_wnd) { |
504 |
/*
|
505 |
* this is a pure ack for outstanding data.
|
506 |
*/
|
507 |
STAT(tcpstat.tcps_predack++); |
508 |
/* if (ts_present)
|
509 |
* tcp_xmit_timer(tp, tcp_now-ts_ecr+1);
|
510 |
* else
|
511 |
*/ if (tp->t_rtt && |
512 |
SEQ_GT(ti->ti_ack, tp->t_rtseq)) |
513 |
tcp_xmit_timer(tp, tp->t_rtt); |
514 |
acked = ti->ti_ack - tp->snd_una; |
515 |
STAT(tcpstat.tcps_rcvackpack++); |
516 |
STAT(tcpstat.tcps_rcvackbyte += acked); |
517 |
sbdrop(&so->so_snd, acked); |
518 |
tp->snd_una = ti->ti_ack; |
519 |
m_freem(m); |
520 |
|
521 |
/*
|
522 |
* If all outstanding data are acked, stop
|
523 |
* retransmit timer, otherwise restart timer
|
524 |
* using current (possibly backed-off) value.
|
525 |
* If process is waiting for space,
|
526 |
* wakeup/selwakeup/signal. If data
|
527 |
* are ready to send, let tcp_output
|
528 |
* decide between more output or persist.
|
529 |
*/
|
530 |
if (tp->snd_una == tp->snd_max)
|
531 |
tp->t_timer[TCPT_REXMT] = 0;
|
532 |
else if (tp->t_timer[TCPT_PERSIST] == 0) |
533 |
tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; |
534 |
|
535 |
/*
|
536 |
* There's room in so_snd, sowwakup will read()
|
537 |
* from the socket if we can
|
538 |
*/
|
539 |
/* if (so->so_snd.sb_flags & SB_NOTIFY)
|
540 |
* sowwakeup(so);
|
541 |
*/
|
542 |
/*
|
543 |
* This is called because sowwakeup might have
|
544 |
* put data into so_snd. Since we don't so sowwakeup,
|
545 |
* we don't need this.. XXX???
|
546 |
*/
|
547 |
if (so->so_snd.sb_cc)
|
548 |
(void) tcp_output(tp);
|
549 |
|
550 |
return;
|
551 |
} |
552 |
} else if (ti->ti_ack == tp->snd_una && |
553 |
tp->seg_next == (tcpiphdrp_32)tp && |
554 |
ti->ti_len <= sbspace(&so->so_rcv)) { |
555 |
/*
|
556 |
* this is a pure, in-sequence data packet
|
557 |
* with nothing on the reassembly queue and
|
558 |
* we have enough buffer space to take it.
|
559 |
*/
|
560 |
STAT(tcpstat.tcps_preddat++); |
561 |
tp->rcv_nxt += ti->ti_len; |
562 |
STAT(tcpstat.tcps_rcvpack++); |
563 |
STAT(tcpstat.tcps_rcvbyte += ti->ti_len); |
564 |
/*
|
565 |
* Add data to socket buffer.
|
566 |
*/
|
567 |
if (so->so_emu) {
|
568 |
if (tcp_emu(so,m)) sbappend(so, m);
|
569 |
} else
|
570 |
sbappend(so, m); |
571 |
|
572 |
/*
|
573 |
* XXX This is called when data arrives. Later, check
|
574 |
* if we can actually write() to the socket
|
575 |
* XXX Need to check? It's be NON_BLOCKING
|
576 |
*/
|
577 |
/* sorwakeup(so); */
|
578 |
|
579 |
/*
|
580 |
* If this is a short packet, then ACK now - with Nagel
|
581 |
* congestion avoidance sender won't send more until
|
582 |
* he gets an ACK.
|
583 |
*
|
584 |
* It is better to not delay acks at all to maximize
|
585 |
* TCP throughput. See RFC 2581.
|
586 |
*/
|
587 |
tp->t_flags |= TF_ACKNOW; |
588 |
tcp_output(tp); |
589 |
return;
|
590 |
} |
591 |
} /* header prediction */
|
592 |
/*
|
593 |
* Calculate amount of space in receive window,
|
594 |
* and then do TCP input processing.
|
595 |
* Receive window is amount of space in rcv queue,
|
596 |
* but not less than advertised window.
|
597 |
*/
|
598 |
{ int win;
|
599 |
win = sbspace(&so->so_rcv); |
600 |
if (win < 0) |
601 |
win = 0;
|
602 |
tp->rcv_wnd = max(win, (int)(tp->rcv_adv - tp->rcv_nxt));
|
603 |
} |
604 |
|
605 |
switch (tp->t_state) {
|
606 |
|
607 |
/*
|
608 |
* If the state is LISTEN then ignore segment if it contains an RST.
|
609 |
* If the segment contains an ACK then it is bad and send a RST.
|
610 |
* If it does not contain a SYN then it is not interesting; drop it.
|
611 |
* Don't bother responding if the destination was a broadcast.
|
612 |
* Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial
|
613 |
* tp->iss, and send a segment:
|
614 |
* <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
|
615 |
* Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss.
|
616 |
* Fill in remote peer address fields if not previously specified.
|
617 |
* Enter SYN_RECEIVED state, and process any other fields of this
|
618 |
* segment in this state.
|
619 |
*/
|
620 |
case TCPS_LISTEN: {
|
621 |
|
622 |
if (tiflags & TH_RST)
|
623 |
goto drop;
|
624 |
if (tiflags & TH_ACK)
|
625 |
goto dropwithreset;
|
626 |
if ((tiflags & TH_SYN) == 0) |
627 |
goto drop;
|
628 |
|
629 |
/*
|
630 |
* This has way too many gotos...
|
631 |
* But a bit of spaghetti code never hurt anybody :)
|
632 |
*/
|
633 |
|
634 |
/*
|
635 |
* If this is destined for the control address, then flag to
|
636 |
* tcp_ctl once connected, otherwise connect
|
637 |
*/
|
638 |
if ((so->so_faddr.s_addr&htonl(0xffffff00)) == special_addr.s_addr) { |
639 |
int lastbyte=ntohl(so->so_faddr.s_addr) & 0xff; |
640 |
if (lastbyte!=CTL_ALIAS && lastbyte!=CTL_DNS) {
|
641 |
#if 0
|
642 |
if(lastbyte==CTL_CMD || lastbyte==CTL_EXEC) {
|
643 |
/* Command or exec adress */
|
644 |
so->so_state |= SS_CTL;
|
645 |
} else
|
646 |
#endif
|
647 |
{ |
648 |
/* May be an add exec */
|
649 |
struct ex_list *ex_ptr;
|
650 |
for(ex_ptr = exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next) {
|
651 |
if(ex_ptr->ex_fport == so->so_fport &&
|
652 |
lastbyte == ex_ptr->ex_addr) { |
653 |
so->so_state |= SS_CTL; |
654 |
break;
|
655 |
} |
656 |
} |
657 |
} |
658 |
if(so->so_state & SS_CTL) goto cont_input; |
659 |
} |
660 |
/* CTL_ALIAS: Do nothing, tcp_fconnect will be called on it */
|
661 |
} |
662 |
|
663 |
if (so->so_emu & EMU_NOCONNECT) {
|
664 |
so->so_emu &= ~EMU_NOCONNECT; |
665 |
goto cont_input;
|
666 |
} |
667 |
|
668 |
if((tcp_fconnect(so) == -1) && (errno != EINPROGRESS) && (errno != EWOULDBLOCK)) { |
669 |
u_char code=ICMP_UNREACH_NET; |
670 |
DEBUG_MISC((dfd," tcp fconnect errno = %d-%s\n",
|
671 |
errno,strerror(errno))); |
672 |
if(errno == ECONNREFUSED) {
|
673 |
/* ACK the SYN, send RST to refuse the connection */
|
674 |
tcp_respond(tp, ti, m, ti->ti_seq+1, (tcp_seq)0, |
675 |
TH_RST|TH_ACK); |
676 |
} else {
|
677 |
if(errno == EHOSTUNREACH) code=ICMP_UNREACH_HOST;
|
678 |
HTONL(ti->ti_seq); /* restore tcp header */
|
679 |
HTONL(ti->ti_ack); |
680 |
HTONS(ti->ti_win); |
681 |
HTONS(ti->ti_urp); |
682 |
m->m_data -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); |
683 |
m->m_len += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); |
684 |
*ip=save_ip; |
685 |
icmp_error(m, ICMP_UNREACH,code, 0,strerror(errno));
|
686 |
} |
687 |
tp = tcp_close(tp); |
688 |
m_free(m); |
689 |
} else {
|
690 |
/*
|
691 |
* Haven't connected yet, save the current mbuf
|
692 |
* and ti, and return
|
693 |
* XXX Some OS's don't tell us whether the connect()
|
694 |
* succeeded or not. So we must time it out.
|
695 |
*/
|
696 |
so->so_m = m; |
697 |
so->so_ti = ti; |
698 |
tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT; |
699 |
tp->t_state = TCPS_SYN_RECEIVED; |
700 |
} |
701 |
return;
|
702 |
|
703 |
cont_conn:
|
704 |
/* m==NULL
|
705 |
* Check if the connect succeeded
|
706 |
*/
|
707 |
if (so->so_state & SS_NOFDREF) {
|
708 |
tp = tcp_close(tp); |
709 |
goto dropwithreset;
|
710 |
} |
711 |
cont_input:
|
712 |
tcp_template(tp); |
713 |
|
714 |
if (optp)
|
715 |
tcp_dooptions(tp, (u_char *)optp, optlen, ti); |
716 |
/* , */
|
717 |
/* &ts_present, &ts_val, &ts_ecr); */
|
718 |
|
719 |
if (iss)
|
720 |
tp->iss = iss; |
721 |
else
|
722 |
tp->iss = tcp_iss; |
723 |
tcp_iss += TCP_ISSINCR/2;
|
724 |
tp->irs = ti->ti_seq; |
725 |
tcp_sendseqinit(tp); |
726 |
tcp_rcvseqinit(tp); |
727 |
tp->t_flags |= TF_ACKNOW; |
728 |
tp->t_state = TCPS_SYN_RECEIVED; |
729 |
tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT; |
730 |
STAT(tcpstat.tcps_accepts++); |
731 |
goto trimthenstep6;
|
732 |
} /* case TCPS_LISTEN */
|
733 |
|
734 |
/*
|
735 |
* If the state is SYN_SENT:
|
736 |
* if seg contains an ACK, but not for our SYN, drop the input.
|
737 |
* if seg contains a RST, then drop the connection.
|
738 |
* if seg does not contain SYN, then drop it.
|
739 |
* Otherwise this is an acceptable SYN segment
|
740 |
* initialize tp->rcv_nxt and tp->irs
|
741 |
* if seg contains ack then advance tp->snd_una
|
742 |
* if SYN has been acked change to ESTABLISHED else SYN_RCVD state
|
743 |
* arrange for segment to be acked (eventually)
|
744 |
* continue processing rest of data/controls, beginning with URG
|
745 |
*/
|
746 |
case TCPS_SYN_SENT:
|
747 |
if ((tiflags & TH_ACK) &&
|
748 |
(SEQ_LEQ(ti->ti_ack, tp->iss) || |
749 |
SEQ_GT(ti->ti_ack, tp->snd_max))) |
750 |
goto dropwithreset;
|
751 |
|
752 |
if (tiflags & TH_RST) {
|
753 |
if (tiflags & TH_ACK)
|
754 |
tp = tcp_drop(tp,0); /* XXX Check t_softerror! */ |
755 |
goto drop;
|
756 |
} |
757 |
|
758 |
if ((tiflags & TH_SYN) == 0) |
759 |
goto drop;
|
760 |
if (tiflags & TH_ACK) {
|
761 |
tp->snd_una = ti->ti_ack; |
762 |
if (SEQ_LT(tp->snd_nxt, tp->snd_una))
|
763 |
tp->snd_nxt = tp->snd_una; |
764 |
} |
765 |
|
766 |
tp->t_timer[TCPT_REXMT] = 0;
|
767 |
tp->irs = ti->ti_seq; |
768 |
tcp_rcvseqinit(tp); |
769 |
tp->t_flags |= TF_ACKNOW; |
770 |
if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) {
|
771 |
STAT(tcpstat.tcps_connects++); |
772 |
soisfconnected(so); |
773 |
tp->t_state = TCPS_ESTABLISHED; |
774 |
|
775 |
/* Do window scaling on this connection? */
|
776 |
/* if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
|
777 |
* (TF_RCVD_SCALE|TF_REQ_SCALE)) {
|
778 |
* tp->snd_scale = tp->requested_s_scale;
|
779 |
* tp->rcv_scale = tp->request_r_scale;
|
780 |
* }
|
781 |
*/
|
782 |
(void) tcp_reass(tp, (struct tcpiphdr *)0, |
783 |
(struct mbuf *)0); |
784 |
/*
|
785 |
* if we didn't have to retransmit the SYN,
|
786 |
* use its rtt as our initial srtt & rtt var.
|
787 |
*/
|
788 |
if (tp->t_rtt)
|
789 |
tcp_xmit_timer(tp, tp->t_rtt); |
790 |
} else
|
791 |
tp->t_state = TCPS_SYN_RECEIVED; |
792 |
|
793 |
trimthenstep6:
|
794 |
/*
|
795 |
* Advance ti->ti_seq to correspond to first data byte.
|
796 |
* If data, trim to stay within window,
|
797 |
* dropping FIN if necessary.
|
798 |
*/
|
799 |
ti->ti_seq++; |
800 |
if (ti->ti_len > tp->rcv_wnd) {
|
801 |
todrop = ti->ti_len - tp->rcv_wnd; |
802 |
m_adj(m, -todrop); |
803 |
ti->ti_len = tp->rcv_wnd; |
804 |
tiflags &= ~TH_FIN; |
805 |
STAT(tcpstat.tcps_rcvpackafterwin++); |
806 |
STAT(tcpstat.tcps_rcvbyteafterwin += todrop); |
807 |
} |
808 |
tp->snd_wl1 = ti->ti_seq - 1;
|
809 |
tp->rcv_up = ti->ti_seq; |
810 |
goto step6;
|
811 |
} /* switch tp->t_state */
|
812 |
/*
|
813 |
* States other than LISTEN or SYN_SENT.
|
814 |
* First check timestamp, if present.
|
815 |
* Then check that at least some bytes of segment are within
|
816 |
* receive window. If segment begins before rcv_nxt,
|
817 |
* drop leading data (and SYN); if nothing left, just ack.
|
818 |
*
|
819 |
* RFC 1323 PAWS: If we have a timestamp reply on this segment
|
820 |
* and it's less than ts_recent, drop it.
|
821 |
*/
|
822 |
/* if (ts_present && (tiflags & TH_RST) == 0 && tp->ts_recent &&
|
823 |
* TSTMP_LT(ts_val, tp->ts_recent)) {
|
824 |
*
|
825 |
*/ /* Check to see if ts_recent is over 24 days old. */ |
826 |
/* if ((int)(tcp_now - tp->ts_recent_age) > TCP_PAWS_IDLE) {
|
827 |
*/ /* |
828 |
* * Invalidate ts_recent. If this segment updates
|
829 |
* * ts_recent, the age will be reset later and ts_recent
|
830 |
* * will get a valid value. If it does not, setting
|
831 |
* * ts_recent to zero will at least satisfy the
|
832 |
* * requirement that zero be placed in the timestamp
|
833 |
* * echo reply when ts_recent isn't valid. The
|
834 |
* * age isn't reset until we get a valid ts_recent
|
835 |
* * because we don't want out-of-order segments to be
|
836 |
* * dropped when ts_recent is old.
|
837 |
* */
|
838 |
/* tp->ts_recent = 0;
|
839 |
* } else {
|
840 |
* tcpstat.tcps_rcvduppack++;
|
841 |
* tcpstat.tcps_rcvdupbyte += ti->ti_len;
|
842 |
* tcpstat.tcps_pawsdrop++;
|
843 |
* goto dropafterack;
|
844 |
* }
|
845 |
* }
|
846 |
*/
|
847 |
|
848 |
todrop = tp->rcv_nxt - ti->ti_seq; |
849 |
if (todrop > 0) { |
850 |
if (tiflags & TH_SYN) {
|
851 |
tiflags &= ~TH_SYN; |
852 |
ti->ti_seq++; |
853 |
if (ti->ti_urp > 1) |
854 |
ti->ti_urp--; |
855 |
else
|
856 |
tiflags &= ~TH_URG; |
857 |
todrop--; |
858 |
} |
859 |
/*
|
860 |
* Following if statement from Stevens, vol. 2, p. 960.
|
861 |
*/
|
862 |
if (todrop > ti->ti_len
|
863 |
|| (todrop == ti->ti_len && (tiflags & TH_FIN) == 0)) {
|
864 |
/*
|
865 |
* Any valid FIN must be to the left of the window.
|
866 |
* At this point the FIN must be a duplicate or out
|
867 |
* of sequence; drop it.
|
868 |
*/
|
869 |
tiflags &= ~TH_FIN; |
870 |
|
871 |
/*
|
872 |
* Send an ACK to resynchronize and drop any data.
|
873 |
* But keep on processing for RST or ACK.
|
874 |
*/
|
875 |
tp->t_flags |= TF_ACKNOW; |
876 |
todrop = ti->ti_len; |
877 |
STAT(tcpstat.tcps_rcvduppack++); |
878 |
STAT(tcpstat.tcps_rcvdupbyte += todrop); |
879 |
} else {
|
880 |
STAT(tcpstat.tcps_rcvpartduppack++); |
881 |
STAT(tcpstat.tcps_rcvpartdupbyte += todrop); |
882 |
} |
883 |
m_adj(m, todrop); |
884 |
ti->ti_seq += todrop; |
885 |
ti->ti_len -= todrop; |
886 |
if (ti->ti_urp > todrop)
|
887 |
ti->ti_urp -= todrop; |
888 |
else {
|
889 |
tiflags &= ~TH_URG; |
890 |
ti->ti_urp = 0;
|
891 |
} |
892 |
} |
893 |
/*
|
894 |
* If new data are received on a connection after the
|
895 |
* user processes are gone, then RST the other end.
|
896 |
*/
|
897 |
if ((so->so_state & SS_NOFDREF) &&
|
898 |
tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) { |
899 |
tp = tcp_close(tp); |
900 |
STAT(tcpstat.tcps_rcvafterclose++); |
901 |
goto dropwithreset;
|
902 |
} |
903 |
|
904 |
/*
|
905 |
* If segment ends after window, drop trailing data
|
906 |
* (and PUSH and FIN); if nothing left, just ACK.
|
907 |
*/
|
908 |
todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); |
909 |
if (todrop > 0) { |
910 |
STAT(tcpstat.tcps_rcvpackafterwin++); |
911 |
if (todrop >= ti->ti_len) {
|
912 |
STAT(tcpstat.tcps_rcvbyteafterwin += ti->ti_len); |
913 |
/*
|
914 |
* If a new connection request is received
|
915 |
* while in TIME_WAIT, drop the old connection
|
916 |
* and start over if the sequence numbers
|
917 |
* are above the previous ones.
|
918 |
*/
|
919 |
if (tiflags & TH_SYN &&
|
920 |
tp->t_state == TCPS_TIME_WAIT && |
921 |
SEQ_GT(ti->ti_seq, tp->rcv_nxt)) { |
922 |
iss = tp->rcv_nxt + TCP_ISSINCR; |
923 |
tp = tcp_close(tp); |
924 |
goto findso;
|
925 |
} |
926 |
/*
|
927 |
* If window is closed can only take segments at
|
928 |
* window edge, and have to drop data and PUSH from
|
929 |
* incoming segments. Continue processing, but
|
930 |
* remember to ack. Otherwise, drop segment
|
931 |
* and ack.
|
932 |
*/
|
933 |
if (tp->rcv_wnd == 0 && ti->ti_seq == tp->rcv_nxt) { |
934 |
tp->t_flags |= TF_ACKNOW; |
935 |
STAT(tcpstat.tcps_rcvwinprobe++); |
936 |
} else
|
937 |
goto dropafterack;
|
938 |
} else
|
939 |
STAT(tcpstat.tcps_rcvbyteafterwin += todrop); |
940 |
m_adj(m, -todrop); |
941 |
ti->ti_len -= todrop; |
942 |
tiflags &= ~(TH_PUSH|TH_FIN); |
943 |
} |
944 |
|
945 |
/*
|
946 |
* If last ACK falls within this segment's sequence numbers,
|
947 |
* record its timestamp.
|
948 |
*/
|
949 |
/* if (ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) &&
|
950 |
* SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len +
|
951 |
* ((tiflags & (TH_SYN|TH_FIN)) != 0))) {
|
952 |
* tp->ts_recent_age = tcp_now;
|
953 |
* tp->ts_recent = ts_val;
|
954 |
* }
|
955 |
*/
|
956 |
|
957 |
/*
|
958 |
* If the RST bit is set examine the state:
|
959 |
* SYN_RECEIVED STATE:
|
960 |
* If passive open, return to LISTEN state.
|
961 |
* If active open, inform user that connection was refused.
|
962 |
* ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES:
|
963 |
* Inform user that connection was reset, and close tcb.
|
964 |
* CLOSING, LAST_ACK, TIME_WAIT STATES
|
965 |
* Close the tcb.
|
966 |
*/
|
967 |
if (tiflags&TH_RST) switch (tp->t_state) { |
968 |
|
969 |
case TCPS_SYN_RECEIVED:
|
970 |
/* so->so_error = ECONNREFUSED; */
|
971 |
goto close;
|
972 |
|
973 |
case TCPS_ESTABLISHED:
|
974 |
case TCPS_FIN_WAIT_1:
|
975 |
case TCPS_FIN_WAIT_2:
|
976 |
case TCPS_CLOSE_WAIT:
|
977 |
/* so->so_error = ECONNRESET; */
|
978 |
close:
|
979 |
tp->t_state = TCPS_CLOSED; |
980 |
STAT(tcpstat.tcps_drops++); |
981 |
tp = tcp_close(tp); |
982 |
goto drop;
|
983 |
|
984 |
case TCPS_CLOSING:
|
985 |
case TCPS_LAST_ACK:
|
986 |
case TCPS_TIME_WAIT:
|
987 |
tp = tcp_close(tp); |
988 |
goto drop;
|
989 |
} |
990 |
|
991 |
/*
|
992 |
* If a SYN is in the window, then this is an
|
993 |
* error and we send an RST and drop the connection.
|
994 |
*/
|
995 |
if (tiflags & TH_SYN) {
|
996 |
tp = tcp_drop(tp,0);
|
997 |
goto dropwithreset;
|
998 |
} |
999 |
|
1000 |
/*
|
1001 |
* If the ACK bit is off we drop the segment and return.
|
1002 |
*/
|
1003 |
if ((tiflags & TH_ACK) == 0) goto drop; |
1004 |
|
1005 |
/*
|
1006 |
* Ack processing.
|
1007 |
*/
|
1008 |
switch (tp->t_state) {
|
1009 |
/*
|
1010 |
* In SYN_RECEIVED state if the ack ACKs our SYN then enter
|
1011 |
* ESTABLISHED state and continue processing, otherwise
|
1012 |
* send an RST. una<=ack<=max
|
1013 |
*/
|
1014 |
case TCPS_SYN_RECEIVED:
|
1015 |
|
1016 |
if (SEQ_GT(tp->snd_una, ti->ti_ack) ||
|
1017 |
SEQ_GT(ti->ti_ack, tp->snd_max)) |
1018 |
goto dropwithreset;
|
1019 |
STAT(tcpstat.tcps_connects++); |
1020 |
tp->t_state = TCPS_ESTABLISHED; |
1021 |
/*
|
1022 |
* The sent SYN is ack'ed with our sequence number +1
|
1023 |
* The first data byte already in the buffer will get
|
1024 |
* lost if no correction is made. This is only needed for
|
1025 |
* SS_CTL since the buffer is empty otherwise.
|
1026 |
* tp->snd_una++; or:
|
1027 |
*/
|
1028 |
tp->snd_una=ti->ti_ack; |
1029 |
if (so->so_state & SS_CTL) {
|
1030 |
/* So tcp_ctl reports the right state */
|
1031 |
ret = tcp_ctl(so); |
1032 |
if (ret == 1) { |
1033 |
soisfconnected(so); |
1034 |
so->so_state &= ~SS_CTL; /* success XXX */
|
1035 |
} else if (ret == 2) { |
1036 |
so->so_state = SS_NOFDREF; /* CTL_CMD */
|
1037 |
} else {
|
1038 |
needoutput = 1;
|
1039 |
tp->t_state = TCPS_FIN_WAIT_1; |
1040 |
} |
1041 |
} else {
|
1042 |
soisfconnected(so); |
1043 |
} |
1044 |
|
1045 |
/* Do window scaling? */
|
1046 |
/* if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
|
1047 |
* (TF_RCVD_SCALE|TF_REQ_SCALE)) {
|
1048 |
* tp->snd_scale = tp->requested_s_scale;
|
1049 |
* tp->rcv_scale = tp->request_r_scale;
|
1050 |
* }
|
1051 |
*/
|
1052 |
(void) tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)0); |
1053 |
tp->snd_wl1 = ti->ti_seq - 1;
|
1054 |
/* Avoid ack processing; snd_una==ti_ack => dup ack */
|
1055 |
goto synrx_to_est;
|
1056 |
/* fall into ... */
|
1057 |
|
1058 |
/*
|
1059 |
* In ESTABLISHED state: drop duplicate ACKs; ACK out of range
|
1060 |
* ACKs. If the ack is in the range
|
1061 |
* tp->snd_una < ti->ti_ack <= tp->snd_max
|
1062 |
* then advance tp->snd_una to ti->ti_ack and drop
|
1063 |
* data from the retransmission queue. If this ACK reflects
|
1064 |
* more up to date window information we update our window information.
|
1065 |
*/
|
1066 |
case TCPS_ESTABLISHED:
|
1067 |
case TCPS_FIN_WAIT_1:
|
1068 |
case TCPS_FIN_WAIT_2:
|
1069 |
case TCPS_CLOSE_WAIT:
|
1070 |
case TCPS_CLOSING:
|
1071 |
case TCPS_LAST_ACK:
|
1072 |
case TCPS_TIME_WAIT:
|
1073 |
|
1074 |
if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) {
|
1075 |
if (ti->ti_len == 0 && tiwin == tp->snd_wnd) { |
1076 |
STAT(tcpstat.tcps_rcvdupack++); |
1077 |
DEBUG_MISC((dfd," dup ack m = %lx so = %lx \n",
|
1078 |
(long )m, (long )so)); |
1079 |
/*
|
1080 |
* If we have outstanding data (other than
|
1081 |
* a window probe), this is a completely
|
1082 |
* duplicate ack (ie, window info didn't
|
1083 |
* change), the ack is the biggest we've
|
1084 |
* seen and we've seen exactly our rexmt
|
1085 |
* threshold of them, assume a packet
|
1086 |
* has been dropped and retransmit it.
|
1087 |
* Kludge snd_nxt & the congestion
|
1088 |
* window so we send only this one
|
1089 |
* packet.
|
1090 |
*
|
1091 |
* We know we're losing at the current
|
1092 |
* window size so do congestion avoidance
|
1093 |
* (set ssthresh to half the current window
|
1094 |
* and pull our congestion window back to
|
1095 |
* the new ssthresh).
|
1096 |
*
|
1097 |
* Dup acks mean that packets have left the
|
1098 |
* network (they're now cached at the receiver)
|
1099 |
* so bump cwnd by the amount in the receiver
|
1100 |
* to keep a constant cwnd packets in the
|
1101 |
* network.
|
1102 |
*/
|
1103 |
if (tp->t_timer[TCPT_REXMT] == 0 || |
1104 |
ti->ti_ack != tp->snd_una) |
1105 |
tp->t_dupacks = 0;
|
1106 |
else if (++tp->t_dupacks == TCPREXMTTHRESH) { |
1107 |
tcp_seq onxt = tp->snd_nxt; |
1108 |
u_int win = |
1109 |
min(tp->snd_wnd, tp->snd_cwnd) / 2 /
|
1110 |
tp->t_maxseg; |
1111 |
|
1112 |
if (win < 2) |
1113 |
win = 2;
|
1114 |
tp->snd_ssthresh = win * tp->t_maxseg; |
1115 |
tp->t_timer[TCPT_REXMT] = 0;
|
1116 |
tp->t_rtt = 0;
|
1117 |
tp->snd_nxt = ti->ti_ack; |
1118 |
tp->snd_cwnd = tp->t_maxseg; |
1119 |
(void) tcp_output(tp);
|
1120 |
tp->snd_cwnd = tp->snd_ssthresh + |
1121 |
tp->t_maxseg * tp->t_dupacks; |
1122 |
if (SEQ_GT(onxt, tp->snd_nxt))
|
1123 |
tp->snd_nxt = onxt; |
1124 |
goto drop;
|
1125 |
} else if (tp->t_dupacks > TCPREXMTTHRESH) { |
1126 |
tp->snd_cwnd += tp->t_maxseg; |
1127 |
(void) tcp_output(tp);
|
1128 |
goto drop;
|
1129 |
} |
1130 |
} else
|
1131 |
tp->t_dupacks = 0;
|
1132 |
break;
|
1133 |
} |
1134 |
synrx_to_est:
|
1135 |
/*
|
1136 |
* If the congestion window was inflated to account
|
1137 |
* for the other side's cached packets, retract it.
|
1138 |
*/
|
1139 |
if (tp->t_dupacks > TCPREXMTTHRESH &&
|
1140 |
tp->snd_cwnd > tp->snd_ssthresh) |
1141 |
tp->snd_cwnd = tp->snd_ssthresh; |
1142 |
tp->t_dupacks = 0;
|
1143 |
if (SEQ_GT(ti->ti_ack, tp->snd_max)) {
|
1144 |
STAT(tcpstat.tcps_rcvacktoomuch++); |
1145 |
goto dropafterack;
|
1146 |
} |
1147 |
acked = ti->ti_ack - tp->snd_una; |
1148 |
STAT(tcpstat.tcps_rcvackpack++); |
1149 |
STAT(tcpstat.tcps_rcvackbyte += acked); |
1150 |
|
1151 |
/*
|
1152 |
* If we have a timestamp reply, update smoothed
|
1153 |
* round trip time. If no timestamp is present but
|
1154 |
* transmit timer is running and timed sequence
|
1155 |
* number was acked, update smoothed round trip time.
|
1156 |
* Since we now have an rtt measurement, cancel the
|
1157 |
* timer backoff (cf., Phil Karn's retransmit alg.).
|
1158 |
* Recompute the initial retransmit timer.
|
1159 |
*/
|
1160 |
/* if (ts_present)
|
1161 |
* tcp_xmit_timer(tp, tcp_now-ts_ecr+1);
|
1162 |
* else
|
1163 |
*/
|
1164 |
if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq))
|
1165 |
tcp_xmit_timer(tp,tp->t_rtt); |
1166 |
|
1167 |
/*
|
1168 |
* If all outstanding data is acked, stop retransmit
|
1169 |
* timer and remember to restart (more output or persist).
|
1170 |
* If there is more data to be acked, restart retransmit
|
1171 |
* timer, using current (possibly backed-off) value.
|
1172 |
*/
|
1173 |
if (ti->ti_ack == tp->snd_max) {
|
1174 |
tp->t_timer[TCPT_REXMT] = 0;
|
1175 |
needoutput = 1;
|
1176 |
} else if (tp->t_timer[TCPT_PERSIST] == 0) |
1177 |
tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; |
1178 |
/*
|
1179 |
* When new data is acked, open the congestion window.
|
1180 |
* If the window gives us less than ssthresh packets
|
1181 |
* in flight, open exponentially (maxseg per packet).
|
1182 |
* Otherwise open linearly: maxseg per window
|
1183 |
* (maxseg^2 / cwnd per packet).
|
1184 |
*/
|
1185 |
{ |
1186 |
register u_int cw = tp->snd_cwnd;
|
1187 |
register u_int incr = tp->t_maxseg;
|
1188 |
|
1189 |
if (cw > tp->snd_ssthresh)
|
1190 |
incr = incr * incr / cw; |
1191 |
tp->snd_cwnd = min(cw + incr, TCP_MAXWIN<<tp->snd_scale); |
1192 |
} |
1193 |
if (acked > so->so_snd.sb_cc) {
|
1194 |
tp->snd_wnd -= so->so_snd.sb_cc; |
1195 |
sbdrop(&so->so_snd, (int )so->so_snd.sb_cc);
|
1196 |
ourfinisacked = 1;
|
1197 |
} else {
|
1198 |
sbdrop(&so->so_snd, acked); |
1199 |
tp->snd_wnd -= acked; |
1200 |
ourfinisacked = 0;
|
1201 |
} |
1202 |
/*
|
1203 |
* XXX sowwakup is called when data is acked and there's room for
|
1204 |
* for more data... it should read() the socket
|
1205 |
*/
|
1206 |
/* if (so->so_snd.sb_flags & SB_NOTIFY)
|
1207 |
* sowwakeup(so);
|
1208 |
*/
|
1209 |
tp->snd_una = ti->ti_ack; |
1210 |
if (SEQ_LT(tp->snd_nxt, tp->snd_una))
|
1211 |
tp->snd_nxt = tp->snd_una; |
1212 |
|
1213 |
switch (tp->t_state) {
|
1214 |
|
1215 |
/*
|
1216 |
* In FIN_WAIT_1 STATE in addition to the processing
|
1217 |
* for the ESTABLISHED state if our FIN is now acknowledged
|
1218 |
* then enter FIN_WAIT_2.
|
1219 |
*/
|
1220 |
case TCPS_FIN_WAIT_1:
|
1221 |
if (ourfinisacked) {
|
1222 |
/*
|
1223 |
* If we can't receive any more
|
1224 |
* data, then closing user can proceed.
|
1225 |
* Starting the timer is contrary to the
|
1226 |
* specification, but if we don't get a FIN
|
1227 |
* we'll hang forever.
|
1228 |
*/
|
1229 |
if (so->so_state & SS_FCANTRCVMORE) {
|
1230 |
soisfdisconnected(so); |
1231 |
tp->t_timer[TCPT_2MSL] = TCP_MAXIDLE; |
1232 |
} |
1233 |
tp->t_state = TCPS_FIN_WAIT_2; |
1234 |
} |
1235 |
break;
|
1236 |
|
1237 |
/*
|
1238 |
* In CLOSING STATE in addition to the processing for
|
1239 |
* the ESTABLISHED state if the ACK acknowledges our FIN
|
1240 |
* then enter the TIME-WAIT state, otherwise ignore
|
1241 |
* the segment.
|
1242 |
*/
|
1243 |
case TCPS_CLOSING:
|
1244 |
if (ourfinisacked) {
|
1245 |
tp->t_state = TCPS_TIME_WAIT; |
1246 |
tcp_canceltimers(tp); |
1247 |
tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
|
1248 |
soisfdisconnected(so); |
1249 |
} |
1250 |
break;
|
1251 |
|
1252 |
/*
|
1253 |
* In LAST_ACK, we may still be waiting for data to drain
|
1254 |
* and/or to be acked, as well as for the ack of our FIN.
|
1255 |
* If our FIN is now acknowledged, delete the TCB,
|
1256 |
* enter the closed state and return.
|
1257 |
*/
|
1258 |
case TCPS_LAST_ACK:
|
1259 |
if (ourfinisacked) {
|
1260 |
tp = tcp_close(tp); |
1261 |
goto drop;
|
1262 |
} |
1263 |
break;
|
1264 |
|
1265 |
/*
|
1266 |
* In TIME_WAIT state the only thing that should arrive
|
1267 |
* is a retransmission of the remote FIN. Acknowledge
|
1268 |
* it and restart the finack timer.
|
1269 |
*/
|
1270 |
case TCPS_TIME_WAIT:
|
1271 |
tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
|
1272 |
goto dropafterack;
|
1273 |
} |
1274 |
} /* switch(tp->t_state) */
|
1275 |
|
1276 |
step6:
|
1277 |
/*
|
1278 |
* Update window information.
|
1279 |
* Don't look at window if no ACK: TAC's send garbage on first SYN.
|
1280 |
*/
|
1281 |
if ((tiflags & TH_ACK) &&
|
1282 |
(SEQ_LT(tp->snd_wl1, ti->ti_seq) || |
1283 |
(tp->snd_wl1 == ti->ti_seq && (SEQ_LT(tp->snd_wl2, ti->ti_ack) || |
1284 |
(tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd))))) { |
1285 |
/* keep track of pure window updates */
|
1286 |
if (ti->ti_len == 0 && |
1287 |
tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd) |
1288 |
STAT(tcpstat.tcps_rcvwinupd++); |
1289 |
tp->snd_wnd = tiwin; |
1290 |
tp->snd_wl1 = ti->ti_seq; |
1291 |
tp->snd_wl2 = ti->ti_ack; |
1292 |
if (tp->snd_wnd > tp->max_sndwnd)
|
1293 |
tp->max_sndwnd = tp->snd_wnd; |
1294 |
needoutput = 1;
|
1295 |
} |
1296 |
|
1297 |
/*
|
1298 |
* Process segments with URG.
|
1299 |
*/
|
1300 |
if ((tiflags & TH_URG) && ti->ti_urp &&
|
1301 |
TCPS_HAVERCVDFIN(tp->t_state) == 0) {
|
1302 |
/*
|
1303 |
* This is a kludge, but if we receive and accept
|
1304 |
* random urgent pointers, we'll crash in
|
1305 |
* soreceive. It's hard to imagine someone
|
1306 |
* actually wanting to send this much urgent data.
|
1307 |
*/
|
1308 |
if (ti->ti_urp + so->so_rcv.sb_cc > so->so_rcv.sb_datalen) {
|
1309 |
ti->ti_urp = 0;
|
1310 |
tiflags &= ~TH_URG; |
1311 |
goto dodata;
|
1312 |
} |
1313 |
/*
|
1314 |
* If this segment advances the known urgent pointer,
|
1315 |
* then mark the data stream. This should not happen
|
1316 |
* in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
|
1317 |
* a FIN has been received from the remote side.
|
1318 |
* In these states we ignore the URG.
|
1319 |
*
|
1320 |
* According to RFC961 (Assigned Protocols),
|
1321 |
* the urgent pointer points to the last octet
|
1322 |
* of urgent data. We continue, however,
|
1323 |
* to consider it to indicate the first octet
|
1324 |
* of data past the urgent section as the original
|
1325 |
* spec states (in one of two places).
|
1326 |
*/
|
1327 |
if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) {
|
1328 |
tp->rcv_up = ti->ti_seq + ti->ti_urp; |
1329 |
so->so_urgc = so->so_rcv.sb_cc + |
1330 |
(tp->rcv_up - tp->rcv_nxt); /* -1; */
|
1331 |
tp->rcv_up = ti->ti_seq + ti->ti_urp; |
1332 |
|
1333 |
} |
1334 |
} else
|
1335 |
/*
|
1336 |
* If no out of band data is expected,
|
1337 |
* pull receive urgent pointer along
|
1338 |
* with the receive window.
|
1339 |
*/
|
1340 |
if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
|
1341 |
tp->rcv_up = tp->rcv_nxt; |
1342 |
dodata:
|
1343 |
|
1344 |
/*
|
1345 |
* Process the segment text, merging it into the TCP sequencing queue,
|
1346 |
* and arranging for acknowledgment of receipt if necessary.
|
1347 |
* This process logically involves adjusting tp->rcv_wnd as data
|
1348 |
* is presented to the user (this happens in tcp_usrreq.c,
|
1349 |
* case PRU_RCVD). If a FIN has already been received on this
|
1350 |
* connection then we just ignore the text.
|
1351 |
*/
|
1352 |
if ((ti->ti_len || (tiflags&TH_FIN)) &&
|
1353 |
TCPS_HAVERCVDFIN(tp->t_state) == 0) {
|
1354 |
TCP_REASS(tp, ti, m, so, tiflags); |
1355 |
/*
|
1356 |
* Note the amount of data that peer has sent into
|
1357 |
* our window, in order to estimate the sender's
|
1358 |
* buffer size.
|
1359 |
*/
|
1360 |
len = so->so_rcv.sb_datalen - (tp->rcv_adv - tp->rcv_nxt); |
1361 |
} else {
|
1362 |
m_free(m); |
1363 |
tiflags &= ~TH_FIN; |
1364 |
} |
1365 |
|
1366 |
/*
|
1367 |
* If FIN is received ACK the FIN and let the user know
|
1368 |
* that the connection is closing.
|
1369 |
*/
|
1370 |
if (tiflags & TH_FIN) {
|
1371 |
if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { |
1372 |
/*
|
1373 |
* If we receive a FIN we can't send more data,
|
1374 |
* set it SS_FDRAIN
|
1375 |
* Shutdown the socket if there is no rx data in the
|
1376 |
* buffer.
|
1377 |
* soread() is called on completion of shutdown() and
|
1378 |
* will got to TCPS_LAST_ACK, and use tcp_output()
|
1379 |
* to send the FIN.
|
1380 |
*/
|
1381 |
/* sofcantrcvmore(so); */
|
1382 |
sofwdrain(so); |
1383 |
|
1384 |
tp->t_flags |= TF_ACKNOW; |
1385 |
tp->rcv_nxt++; |
1386 |
} |
1387 |
switch (tp->t_state) {
|
1388 |
|
1389 |
/*
|
1390 |
* In SYN_RECEIVED and ESTABLISHED STATES
|
1391 |
* enter the CLOSE_WAIT state.
|
1392 |
*/
|
1393 |
case TCPS_SYN_RECEIVED:
|
1394 |
case TCPS_ESTABLISHED:
|
1395 |
if(so->so_emu == EMU_CTL) /* no shutdown on socket */ |
1396 |
tp->t_state = TCPS_LAST_ACK; |
1397 |
else
|
1398 |
tp->t_state = TCPS_CLOSE_WAIT; |
1399 |
break;
|
1400 |
|
1401 |
/*
|
1402 |
* If still in FIN_WAIT_1 STATE FIN has not been acked so
|
1403 |
* enter the CLOSING state.
|
1404 |
*/
|
1405 |
case TCPS_FIN_WAIT_1:
|
1406 |
tp->t_state = TCPS_CLOSING; |
1407 |
break;
|
1408 |
|
1409 |
/*
|
1410 |
* In FIN_WAIT_2 state enter the TIME_WAIT state,
|
1411 |
* starting the time-wait timer, turning off the other
|
1412 |
* standard timers.
|
1413 |
*/
|
1414 |
case TCPS_FIN_WAIT_2:
|
1415 |
tp->t_state = TCPS_TIME_WAIT; |
1416 |
tcp_canceltimers(tp); |
1417 |
tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
|
1418 |
soisfdisconnected(so); |
1419 |
break;
|
1420 |
|
1421 |
/*
|
1422 |
* In TIME_WAIT state restart the 2 MSL time_wait timer.
|
1423 |
*/
|
1424 |
case TCPS_TIME_WAIT:
|
1425 |
tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
|
1426 |
break;
|
1427 |
} |
1428 |
} |
1429 |
|
1430 |
/*
|
1431 |
* If this is a small packet, then ACK now - with Nagel
|
1432 |
* congestion avoidance sender won't send more until
|
1433 |
* he gets an ACK.
|
1434 |
*
|
1435 |
* See above.
|
1436 |
*/
|
1437 |
/* if (ti->ti_len && (unsigned)ti->ti_len < tp->t_maxseg) {
|
1438 |
*/
|
1439 |
/* if ((ti->ti_len && (unsigned)ti->ti_len < tp->t_maxseg &&
|
1440 |
* (so->so_iptos & IPTOS_LOWDELAY) == 0) ||
|
1441 |
* ((so->so_iptos & IPTOS_LOWDELAY) &&
|
1442 |
* ((struct tcpiphdr_2 *)ti)->first_char == (char)27)) {
|
1443 |
*/
|
1444 |
if (ti->ti_len && (unsigned)ti->ti_len <= 5 && |
1445 |
((struct tcpiphdr_2 *)ti)->first_char == (char)27) { |
1446 |
tp->t_flags |= TF_ACKNOW; |
1447 |
} |
1448 |
|
1449 |
/*
|
1450 |
* Return any desired output.
|
1451 |
*/
|
1452 |
if (needoutput || (tp->t_flags & TF_ACKNOW)) {
|
1453 |
(void) tcp_output(tp);
|
1454 |
} |
1455 |
return;
|
1456 |
|
1457 |
dropafterack:
|
1458 |
/*
|
1459 |
* Generate an ACK dropping incoming segment if it occupies
|
1460 |
* sequence space, where the ACK reflects our state.
|
1461 |
*/
|
1462 |
if (tiflags & TH_RST)
|
1463 |
goto drop;
|
1464 |
m_freem(m); |
1465 |
tp->t_flags |= TF_ACKNOW; |
1466 |
(void) tcp_output(tp);
|
1467 |
return;
|
1468 |
|
1469 |
dropwithreset:
|
1470 |
/* reuses m if m!=NULL, m_free() unnecessary */
|
1471 |
if (tiflags & TH_ACK)
|
1472 |
tcp_respond(tp, ti, m, (tcp_seq)0, ti->ti_ack, TH_RST);
|
1473 |
else {
|
1474 |
if (tiflags & TH_SYN) ti->ti_len++;
|
1475 |
tcp_respond(tp, ti, m, ti->ti_seq+ti->ti_len, (tcp_seq)0,
|
1476 |
TH_RST|TH_ACK); |
1477 |
} |
1478 |
|
1479 |
return;
|
1480 |
|
1481 |
drop:
|
1482 |
/*
|
1483 |
* Drop space held by incoming segment and return.
|
1484 |
*/
|
1485 |
m_free(m); |
1486 |
|
1487 |
return;
|
1488 |
} |
1489 |
|
1490 |
/* , ts_present, ts_val, ts_ecr) */
|
1491 |
/* int *ts_present;
|
1492 |
* u_int32_t *ts_val, *ts_ecr;
|
1493 |
*/
|
1494 |
static void |
1495 |
tcp_dooptions(struct tcpcb *tp, u_char *cp, int cnt, struct tcpiphdr *ti) |
1496 |
{ |
1497 |
u_int16_t mss; |
1498 |
int opt, optlen;
|
1499 |
|
1500 |
DEBUG_CALL("tcp_dooptions");
|
1501 |
DEBUG_ARGS((dfd," tp = %lx cnt=%i \n", (long )tp, cnt)); |
1502 |
|
1503 |
for (; cnt > 0; cnt -= optlen, cp += optlen) { |
1504 |
opt = cp[0];
|
1505 |
if (opt == TCPOPT_EOL)
|
1506 |
break;
|
1507 |
if (opt == TCPOPT_NOP)
|
1508 |
optlen = 1;
|
1509 |
else {
|
1510 |
optlen = cp[1];
|
1511 |
if (optlen <= 0) |
1512 |
break;
|
1513 |
} |
1514 |
switch (opt) {
|
1515 |
|
1516 |
default:
|
1517 |
continue;
|
1518 |
|
1519 |
case TCPOPT_MAXSEG:
|
1520 |
if (optlen != TCPOLEN_MAXSEG)
|
1521 |
continue;
|
1522 |
if (!(ti->ti_flags & TH_SYN))
|
1523 |
continue;
|
1524 |
memcpy((char *) &mss, (char *) cp + 2, sizeof(mss)); |
1525 |
NTOHS(mss); |
1526 |
(void) tcp_mss(tp, mss); /* sets t_maxseg */ |
1527 |
break;
|
1528 |
|
1529 |
/* case TCPOPT_WINDOW:
|
1530 |
* if (optlen != TCPOLEN_WINDOW)
|
1531 |
* continue;
|
1532 |
* if (!(ti->ti_flags & TH_SYN))
|
1533 |
* continue;
|
1534 |
* tp->t_flags |= TF_RCVD_SCALE;
|
1535 |
* tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
|
1536 |
* break;
|
1537 |
*/
|
1538 |
/* case TCPOPT_TIMESTAMP:
|
1539 |
* if (optlen != TCPOLEN_TIMESTAMP)
|
1540 |
* continue;
|
1541 |
* *ts_present = 1;
|
1542 |
* memcpy((char *) ts_val, (char *)cp + 2, sizeof(*ts_val));
|
1543 |
* NTOHL(*ts_val);
|
1544 |
* memcpy((char *) ts_ecr, (char *)cp + 6, sizeof(*ts_ecr));
|
1545 |
* NTOHL(*ts_ecr);
|
1546 |
*
|
1547 |
*/ /* |
1548 |
* * A timestamp received in a SYN makes
|
1549 |
* * it ok to send timestamp requests and replies.
|
1550 |
* */
|
1551 |
/* if (ti->ti_flags & TH_SYN) {
|
1552 |
* tp->t_flags |= TF_RCVD_TSTMP;
|
1553 |
* tp->ts_recent = *ts_val;
|
1554 |
* tp->ts_recent_age = tcp_now;
|
1555 |
* }
|
1556 |
*/ break; |
1557 |
} |
1558 |
} |
1559 |
} |
1560 |
|
1561 |
|
1562 |
/*
|
1563 |
* Pull out of band byte out of a segment so
|
1564 |
* it doesn't appear in the user's data queue.
|
1565 |
* It is still reflected in the segment length for
|
1566 |
* sequencing purposes.
|
1567 |
*/
|
1568 |
|
1569 |
#ifdef notdef
|
1570 |
|
1571 |
void
|
1572 |
tcp_pulloutofband(so, ti, m) |
1573 |
struct socket *so;
|
1574 |
struct tcpiphdr *ti;
|
1575 |
register struct mbuf *m; |
1576 |
{ |
1577 |
int cnt = ti->ti_urp - 1; |
1578 |
|
1579 |
while (cnt >= 0) { |
1580 |
if (m->m_len > cnt) {
|
1581 |
char *cp = mtod(m, caddr_t) + cnt;
|
1582 |
struct tcpcb *tp = sototcpcb(so);
|
1583 |
|
1584 |
tp->t_iobc = *cp; |
1585 |
tp->t_oobflags |= TCPOOB_HAVEDATA; |
1586 |
memcpy(sp, cp+1, (unsigned)(m->m_len - cnt - 1)); |
1587 |
m->m_len--; |
1588 |
return;
|
1589 |
} |
1590 |
cnt -= m->m_len; |
1591 |
m = m->m_next; /* XXX WRONG! Fix it! */
|
1592 |
if (m == 0) |
1593 |
break;
|
1594 |
} |
1595 |
panic("tcp_pulloutofband");
|
1596 |
} |
1597 |
|
1598 |
#endif /* notdef */ |
1599 |
|
1600 |
/*
|
1601 |
* Collect new round-trip time estimate
|
1602 |
* and update averages and current timeout.
|
1603 |
*/
|
1604 |
|
1605 |
static void |
1606 |
tcp_xmit_timer(register struct tcpcb *tp, int rtt) |
1607 |
{ |
1608 |
register short delta; |
1609 |
|
1610 |
DEBUG_CALL("tcp_xmit_timer");
|
1611 |
DEBUG_ARG("tp = %lx", (long)tp); |
1612 |
DEBUG_ARG("rtt = %d", rtt);
|
1613 |
|
1614 |
STAT(tcpstat.tcps_rttupdated++); |
1615 |
if (tp->t_srtt != 0) { |
1616 |
/*
|
1617 |
* srtt is stored as fixed point with 3 bits after the
|
1618 |
* binary point (i.e., scaled by 8). The following magic
|
1619 |
* is equivalent to the smoothing algorithm in rfc793 with
|
1620 |
* an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
|
1621 |
* point). Adjust rtt to origin 0.
|
1622 |
*/
|
1623 |
delta = rtt - 1 - (tp->t_srtt >> TCP_RTT_SHIFT);
|
1624 |
if ((tp->t_srtt += delta) <= 0) |
1625 |
tp->t_srtt = 1;
|
1626 |
/*
|
1627 |
* We accumulate a smoothed rtt variance (actually, a
|
1628 |
* smoothed mean difference), then set the retransmit
|
1629 |
* timer to smoothed rtt + 4 times the smoothed variance.
|
1630 |
* rttvar is stored as fixed point with 2 bits after the
|
1631 |
* binary point (scaled by 4). The following is
|
1632 |
* equivalent to rfc793 smoothing with an alpha of .75
|
1633 |
* (rttvar = rttvar*3/4 + |delta| / 4). This replaces
|
1634 |
* rfc793's wired-in beta.
|
1635 |
*/
|
1636 |
if (delta < 0) |
1637 |
delta = -delta; |
1638 |
delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT); |
1639 |
if ((tp->t_rttvar += delta) <= 0) |
1640 |
tp->t_rttvar = 1;
|
1641 |
} else {
|
1642 |
/*
|
1643 |
* No rtt measurement yet - use the unsmoothed rtt.
|
1644 |
* Set the variance to half the rtt (so our first
|
1645 |
* retransmit happens at 3*rtt).
|
1646 |
*/
|
1647 |
tp->t_srtt = rtt << TCP_RTT_SHIFT; |
1648 |
tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
|
1649 |
} |
1650 |
tp->t_rtt = 0;
|
1651 |
tp->t_rxtshift = 0;
|
1652 |
|
1653 |
/*
|
1654 |
* the retransmit should happen at rtt + 4 * rttvar.
|
1655 |
* Because of the way we do the smoothing, srtt and rttvar
|
1656 |
* will each average +1/2 tick of bias. When we compute
|
1657 |
* the retransmit timer, we want 1/2 tick of rounding and
|
1658 |
* 1 extra tick because of +-1/2 tick uncertainty in the
|
1659 |
* firing of the timer. The bias will give us exactly the
|
1660 |
* 1.5 tick we need. But, because the bias is
|
1661 |
* statistical, we have to test that we don't drop below
|
1662 |
* the minimum feasible timer (which is 2 ticks).
|
1663 |
*/
|
1664 |
TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), |
1665 |
(short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */ |
1666 |
|
1667 |
/*
|
1668 |
* We received an ack for a packet that wasn't retransmitted;
|
1669 |
* it is probably safe to discard any error indications we've
|
1670 |
* received recently. This isn't quite right, but close enough
|
1671 |
* for now (a route might have failed after we sent a segment,
|
1672 |
* and the return path might not be symmetrical).
|
1673 |
*/
|
1674 |
tp->t_softerror = 0;
|
1675 |
} |
1676 |
|
1677 |
/*
|
1678 |
* Determine a reasonable value for maxseg size.
|
1679 |
* If the route is known, check route for mtu.
|
1680 |
* If none, use an mss that can be handled on the outgoing
|
1681 |
* interface without forcing IP to fragment; if bigger than
|
1682 |
* an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
|
1683 |
* to utilize large mbufs. If no route is found, route has no mtu,
|
1684 |
* or the destination isn't local, use a default, hopefully conservative
|
1685 |
* size (usually 512 or the default IP max size, but no more than the mtu
|
1686 |
* of the interface), as we can't discover anything about intervening
|
1687 |
* gateways or networks. We also initialize the congestion/slow start
|
1688 |
* window to be a single segment if the destination isn't local.
|
1689 |
* While looking at the routing entry, we also initialize other path-dependent
|
1690 |
* parameters from pre-set or cached values in the routing entry.
|
1691 |
*/
|
1692 |
|
1693 |
int
|
1694 |
tcp_mss(tp, offer) |
1695 |
register struct tcpcb *tp; |
1696 |
u_int offer; |
1697 |
{ |
1698 |
struct socket *so = tp->t_socket;
|
1699 |
int mss;
|
1700 |
|
1701 |
DEBUG_CALL("tcp_mss");
|
1702 |
DEBUG_ARG("tp = %lx", (long)tp); |
1703 |
DEBUG_ARG("offer = %d", offer);
|
1704 |
|
1705 |
mss = min(IF_MTU, IF_MRU) - sizeof(struct tcpiphdr); |
1706 |
if (offer)
|
1707 |
mss = min(mss, offer); |
1708 |
mss = max(mss, 32);
|
1709 |
if (mss < tp->t_maxseg || offer != 0) |
1710 |
tp->t_maxseg = mss; |
1711 |
|
1712 |
tp->snd_cwnd = mss; |
1713 |
|
1714 |
sbreserve(&so->so_snd, TCP_SNDSPACE + ((TCP_SNDSPACE % mss) ? |
1715 |
(mss - (TCP_SNDSPACE % mss)) : |
1716 |
0));
|
1717 |
sbreserve(&so->so_rcv, TCP_RCVSPACE + ((TCP_RCVSPACE % mss) ? |
1718 |
(mss - (TCP_RCVSPACE % mss)) : |
1719 |
0));
|
1720 |
|
1721 |
DEBUG_MISC((dfd, " returning mss = %d\n", mss));
|
1722 |
|
1723 |
return mss;
|
1724 |
} |