1488 lines
41 KiB
C
1488 lines
41 KiB
C
/*
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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. 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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#define TCPREXMTTHRESH 3
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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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tcpfrag_list_empty(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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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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} 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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tcpfrag_list_empty(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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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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} 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==NULL 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 == NULL)
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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 = tcpfrag_list_first(tp); !tcpfrag_list_end(q, tp);
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q = tcpiphdr_next(q))
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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 (!tcpfrag_list_end(tcpiphdr_prev(q), tp)) {
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register int i;
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q = tcpiphdr_prev(q);
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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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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 = tcpiphdr_next(q);
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}
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ti->ti_mbuf = m;
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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 (!tcpfrag_list_end(q, 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(q->ti_mbuf, i);
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break;
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}
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q = tcpiphdr_next(q);
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m = tcpiphdr_prev(q)->ti_mbuf;
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remque(tcpiphdr2qlink(tcpiphdr_prev(q)));
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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(tcpiphdr2qlink(ti), tcpiphdr2qlink(tcpiphdr_prev(q)));
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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 = tcpfrag_list_first(tp);
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if (tcpfrag_list_end(ti, 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(tcpiphdr2qlink(ti));
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m = ti->ti_mbuf;
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ti = tcpiphdr_next(ti);
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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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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(struct mbuf *m, int iphlen, 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 = NULL;
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register int tiflags;
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struct socket *so = NULL;
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int todrop, acked, ourfinisacked, needoutput = 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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struct ex_list *ex_ptr;
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Slirp *slirp;
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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 ));
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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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slirp = so->slirp;
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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 = NULL;
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ti = so->so_ti;
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tiwin = ti->ti_win;
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tiflags = ti->ti_flags;
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goto cont_conn;
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}
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slirp = m->slirp;
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/*
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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 )) {
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ip_stripoptions(m, (struct mbuf *)0);
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iphlen=sizeof(struct ip );
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}
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/* XXX Check if too short */
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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;
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save_ip.ip_len+= iphlen;
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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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tcpiphdr2qlink(ti)->next = tcpiphdr2qlink(ti)->prev = NULL;
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memset(&ti->ti_i.ih_mbuf, 0 , sizeof(struct mbuf_ptr));
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ti->ti_x1 = 0;
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ti->ti_len = htons((u_int16_t)tlen);
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len = sizeof(struct ip ) + tlen;
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if(cksum(m, len)) {
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goto drop;
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}
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/*
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* Check that TCP offset makes sense,
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* pull out TCP options and adjust length. XXX
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*/
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off = ti->ti_off << 2;
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if (off < sizeof (struct tcphdr) || off > tlen) {
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goto drop;
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}
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tlen -= off;
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ti->ti_len = tlen;
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if (off > sizeof (struct tcphdr)) {
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optlen = off - sizeof (struct tcphdr);
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optp = mtod(m, caddr_t) + sizeof (struct tcpiphdr);
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}
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tiflags = ti->ti_flags;
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/*
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* Convert TCP protocol specific fields to host format.
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*/
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NTOHL(ti->ti_seq);
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NTOHL(ti->ti_ack);
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NTOHS(ti->ti_win);
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NTOHS(ti->ti_urp);
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/*
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* Drop TCP, IP headers and TCP options.
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*/
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m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
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m->m_len -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
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if (slirp->restricted) {
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for (ex_ptr = slirp->exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next) {
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if (ex_ptr->ex_fport == ti->ti_dport &&
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ti->ti_dst.s_addr == ex_ptr->ex_addr.s_addr) {
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break;
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}
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}
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if (!ex_ptr)
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goto drop;
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}
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/*
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* Locate pcb for segment.
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*/
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findso:
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so = slirp->tcp_last_so;
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if (so->so_fport != ti->ti_dport ||
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so->so_lport != ti->ti_sport ||
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so->so_laddr.s_addr != ti->ti_src.s_addr ||
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so->so_faddr.s_addr != ti->ti_dst.s_addr) {
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so = solookup(&slirp->tcb, ti->ti_src, ti->ti_sport,
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ti->ti_dst, ti->ti_dport);
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if (so)
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slirp->tcp_last_so = so;
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}
|
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|
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/*
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* If the state is CLOSED (i.e., TCB does not exist) then
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* all data in the incoming segment is discarded.
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* If the TCB exists but is in CLOSED state, it is embryonic,
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* but should either do a listen or a connect soon.
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*
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* state == CLOSED means we've done socreate() but haven't
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* attached it to a protocol yet...
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*
|
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* XXX If a TCB does not exist, and the TH_SYN flag is
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* the only flag set, then create a session, mark it
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* as if it was LISTENING, and continue...
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*/
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if (so == NULL) {
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if ((tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) != TH_SYN)
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goto dropwithreset;
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|
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if ((so = socreate(slirp)) == NULL)
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goto dropwithreset;
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if (tcp_attach(so) < 0) {
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free(so); /* Not sofree (if it failed, it's not insqued) */
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goto dropwithreset;
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}
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sbreserve(&so->so_snd, TCP_SNDSPACE);
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sbreserve(&so->so_rcv, TCP_RCVSPACE);
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|
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so->so_laddr = ti->ti_src;
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so->so_lport = ti->ti_sport;
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so->so_faddr = ti->ti_dst;
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so->so_fport = ti->ti_dport;
|
|
|
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if ((so->so_iptos = tcp_tos(so)) == 0)
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so->so_iptos = ((struct ip *)ti)->ip_tos;
|
|
|
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tp = sototcpcb(so);
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tp->t_state = TCPS_LISTEN;
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}
|
|
|
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/*
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* If this is a still-connecting socket, this probably
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* a retransmit of the SYN. Whether it's a retransmit SYN
|
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* or something else, we nuke it.
|
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*/
|
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if (so->so_state & SS_ISFCONNECTING)
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goto drop;
|
|
|
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tp = sototcpcb(so);
|
|
|
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/* XXX Should never fail */
|
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if (tp == NULL)
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goto dropwithreset;
|
|
if (tp->t_state == TCPS_CLOSED)
|
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goto drop;
|
|
|
|
tiwin = ti->ti_win;
|
|
|
|
/*
|
|
* Segment received on connection.
|
|
* Reset idle time and keep-alive timer.
|
|
*/
|
|
tp->t_idle = 0;
|
|
if (SO_OPTIONS)
|
|
tp->t_timer[TCPT_KEEP] = TCPTV_KEEPINTVL;
|
|
else
|
|
tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_IDLE;
|
|
|
|
/*
|
|
* Process options if not in LISTEN state,
|
|
* else do it below (after getting remote address).
|
|
*/
|
|
if (optp && tp->t_state != TCPS_LISTEN)
|
|
tcp_dooptions(tp, (u_char *)optp, optlen, ti);
|
|
|
|
/*
|
|
* Header prediction: check for the two common cases
|
|
* of a uni-directional data xfer. If the packet has
|
|
* no control flags, is in-sequence, the window didn't
|
|
* change and we're not retransmitting, it's a
|
|
* candidate. If the length is zero and the ack moved
|
|
* forward, we're the sender side of the xfer. Just
|
|
* free the data acked & wake any higher level process
|
|
* that was blocked waiting for space. If the length
|
|
* is non-zero and the ack didn't move, we're the
|
|
* receiver side. If we're getting packets in-order
|
|
* (the reassembly queue is empty), add the data to
|
|
* the socket buffer and note that we need a delayed ack.
|
|
*
|
|
* XXX Some of these tests are not needed
|
|
* eg: the tiwin == tp->snd_wnd prevents many more
|
|
* predictions.. with no *real* advantage..
|
|
*/
|
|
if (tp->t_state == TCPS_ESTABLISHED &&
|
|
(tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
|
|
ti->ti_seq == tp->rcv_nxt &&
|
|
tiwin && tiwin == tp->snd_wnd &&
|
|
tp->snd_nxt == tp->snd_max) {
|
|
if (ti->ti_len == 0) {
|
|
if (SEQ_GT(ti->ti_ack, tp->snd_una) &&
|
|
SEQ_LEQ(ti->ti_ack, tp->snd_max) &&
|
|
tp->snd_cwnd >= tp->snd_wnd) {
|
|
/*
|
|
* this is a pure ack for outstanding data.
|
|
*/
|
|
if (tp->t_rtt &&
|
|
SEQ_GT(ti->ti_ack, tp->t_rtseq))
|
|
tcp_xmit_timer(tp, tp->t_rtt);
|
|
acked = ti->ti_ack - tp->snd_una;
|
|
sbdrop(&so->so_snd, acked);
|
|
tp->snd_una = ti->ti_ack;
|
|
m_freem(m);
|
|
|
|
/*
|
|
* If all outstanding data are acked, stop
|
|
* retransmit timer, otherwise restart timer
|
|
* using current (possibly backed-off) value.
|
|
* If process is waiting for space,
|
|
* wakeup/selwakeup/signal. If data
|
|
* are ready to send, let tcp_output
|
|
* decide between more output or persist.
|
|
*/
|
|
if (tp->snd_una == tp->snd_max)
|
|
tp->t_timer[TCPT_REXMT] = 0;
|
|
else if (tp->t_timer[TCPT_PERSIST] == 0)
|
|
tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
|
|
|
|
/*
|
|
* This is called because sowwakeup might have
|
|
* put data into so_snd. Since we don't so sowwakeup,
|
|
* we don't need this.. XXX???
|
|
*/
|
|
if (so->so_snd.sb_cc)
|
|
(void) tcp_output(tp);
|
|
|
|
return;
|
|
}
|
|
} else if (ti->ti_ack == tp->snd_una &&
|
|
tcpfrag_list_empty(tp) &&
|
|
ti->ti_len <= sbspace(&so->so_rcv)) {
|
|
/*
|
|
* this is a pure, in-sequence data packet
|
|
* with nothing on the reassembly queue and
|
|
* we have enough buffer space to take it.
|
|
*/
|
|
tp->rcv_nxt += ti->ti_len;
|
|
/*
|
|
* Add data to socket buffer.
|
|
*/
|
|
if (so->so_emu) {
|
|
if (tcp_emu(so,m)) sbappend(so, m);
|
|
} else
|
|
sbappend(so, m);
|
|
|
|
/*
|
|
* If this is a short packet, then ACK now - with Nagel
|
|
* congestion avoidance sender won't send more until
|
|
* he gets an ACK.
|
|
*
|
|
* It is better to not delay acks at all to maximize
|
|
* TCP throughput. See RFC 2581.
|
|
*/
|
|
tp->t_flags |= TF_ACKNOW;
|
|
tcp_output(tp);
|
|
return;
|
|
}
|
|
} /* header prediction */
|
|
/*
|
|
* Calculate amount of space in receive window,
|
|
* and then do TCP input processing.
|
|
* Receive window is amount of space in rcv queue,
|
|
* but not less than advertised window.
|
|
*/
|
|
{ int win;
|
|
win = sbspace(&so->so_rcv);
|
|
if (win < 0)
|
|
win = 0;
|
|
tp->rcv_wnd = max(win, (int)(tp->rcv_adv - tp->rcv_nxt));
|
|
}
|
|
|
|
switch (tp->t_state) {
|
|
|
|
/*
|
|
* If the state is LISTEN then ignore segment if it contains an RST.
|
|
* If the segment contains an ACK then it is bad and send a RST.
|
|
* If it does not contain a SYN then it is not interesting; drop it.
|
|
* Don't bother responding if the destination was a broadcast.
|
|
* Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial
|
|
* tp->iss, and send a segment:
|
|
* <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
|
|
* Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss.
|
|
* Fill in remote peer address fields if not previously specified.
|
|
* Enter SYN_RECEIVED state, and process any other fields of this
|
|
* segment in this state.
|
|
*/
|
|
case TCPS_LISTEN: {
|
|
|
|
if (tiflags & TH_RST)
|
|
goto drop;
|
|
if (tiflags & TH_ACK)
|
|
goto dropwithreset;
|
|
if ((tiflags & TH_SYN) == 0)
|
|
goto drop;
|
|
|
|
/*
|
|
* This has way too many gotos...
|
|
* But a bit of spaghetti code never hurt anybody :)
|
|
*/
|
|
|
|
/*
|
|
* If this is destined for the control address, then flag to
|
|
* tcp_ctl once connected, otherwise connect
|
|
*/
|
|
if ((so->so_faddr.s_addr & slirp->vnetwork_mask.s_addr) ==
|
|
slirp->vnetwork_addr.s_addr) {
|
|
if (so->so_faddr.s_addr != slirp->vhost_addr.s_addr &&
|
|
so->so_faddr.s_addr != slirp->vnameserver_addr.s_addr) {
|
|
/* May be an add exec */
|
|
for (ex_ptr = slirp->exec_list; ex_ptr;
|
|
ex_ptr = ex_ptr->ex_next) {
|
|
if(ex_ptr->ex_fport == so->so_fport &&
|
|
so->so_faddr.s_addr == ex_ptr->ex_addr.s_addr) {
|
|
so->so_state |= SS_CTL;
|
|
break;
|
|
}
|
|
}
|
|
if (so->so_state & SS_CTL) {
|
|
goto cont_input;
|
|
}
|
|
}
|
|
/* CTL_ALIAS: Do nothing, tcp_fconnect will be called on it */
|
|
}
|
|
|
|
if (so->so_emu & EMU_NOCONNECT) {
|
|
so->so_emu &= ~EMU_NOCONNECT;
|
|
goto cont_input;
|
|
}
|
|
|
|
if((tcp_fconnect(so) == -1) && (errno != EINPROGRESS) && (errno != EWOULDBLOCK)) {
|
|
u_char code=ICMP_UNREACH_NET;
|
|
DEBUG_MISC((dfd," tcp fconnect errno = %d-%s\n",
|
|
errno,strerror(errno)));
|
|
if(errno == ECONNREFUSED) {
|
|
/* ACK the SYN, send RST to refuse the connection */
|
|
tcp_respond(tp, ti, m, ti->ti_seq+1, (tcp_seq)0,
|
|
TH_RST|TH_ACK);
|
|
} else {
|
|
if(errno == EHOSTUNREACH) code=ICMP_UNREACH_HOST;
|
|
HTONL(ti->ti_seq); /* restore tcp header */
|
|
HTONL(ti->ti_ack);
|
|
HTONS(ti->ti_win);
|
|
HTONS(ti->ti_urp);
|
|
m->m_data -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
|
|
m->m_len += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
|
|
*ip=save_ip;
|
|
icmp_error(m, ICMP_UNREACH,code, 0,strerror(errno));
|
|
}
|
|
tcp_close(tp);
|
|
m_free(m);
|
|
} else {
|
|
/*
|
|
* Haven't connected yet, save the current mbuf
|
|
* and ti, and return
|
|
* XXX Some OS's don't tell us whether the connect()
|
|
* succeeded or not. So we must time it out.
|
|
*/
|
|
so->so_m = m;
|
|
so->so_ti = ti;
|
|
tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT;
|
|
tp->t_state = TCPS_SYN_RECEIVED;
|
|
}
|
|
return;
|
|
|
|
cont_conn:
|
|
/* m==NULL
|
|
* Check if the connect succeeded
|
|
*/
|
|
if (so->so_state & SS_NOFDREF) {
|
|
tp = tcp_close(tp);
|
|
goto dropwithreset;
|
|
}
|
|
cont_input:
|
|
tcp_template(tp);
|
|
|
|
if (optp)
|
|
tcp_dooptions(tp, (u_char *)optp, optlen, ti);
|
|
|
|
if (iss)
|
|
tp->iss = iss;
|
|
else
|
|
tp->iss = slirp->tcp_iss;
|
|
slirp->tcp_iss += TCP_ISSINCR/2;
|
|
tp->irs = ti->ti_seq;
|
|
tcp_sendseqinit(tp);
|
|
tcp_rcvseqinit(tp);
|
|
tp->t_flags |= TF_ACKNOW;
|
|
tp->t_state = TCPS_SYN_RECEIVED;
|
|
tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT;
|
|
goto trimthenstep6;
|
|
} /* case TCPS_LISTEN */
|
|
|
|
/*
|
|
* If the state is SYN_SENT:
|
|
* if seg contains an ACK, but not for our SYN, drop the input.
|
|
* if seg contains a RST, then drop the connection.
|
|
* if seg does not contain SYN, then drop it.
|
|
* Otherwise this is an acceptable SYN segment
|
|
* initialize tp->rcv_nxt and tp->irs
|
|
* if seg contains ack then advance tp->snd_una
|
|
* if SYN has been acked change to ESTABLISHED else SYN_RCVD state
|
|
* arrange for segment to be acked (eventually)
|
|
* continue processing rest of data/controls, beginning with URG
|
|
*/
|
|
case TCPS_SYN_SENT:
|
|
if ((tiflags & TH_ACK) &&
|
|
(SEQ_LEQ(ti->ti_ack, tp->iss) ||
|
|
SEQ_GT(ti->ti_ack, tp->snd_max)))
|
|
goto dropwithreset;
|
|
|
|
if (tiflags & TH_RST) {
|
|
if (tiflags & TH_ACK) {
|
|
tcp_drop(tp, 0); /* XXX Check t_softerror! */
|
|
}
|
|
goto drop;
|
|
}
|
|
|
|
if ((tiflags & TH_SYN) == 0)
|
|
goto drop;
|
|
if (tiflags & TH_ACK) {
|
|
tp->snd_una = ti->ti_ack;
|
|
if (SEQ_LT(tp->snd_nxt, tp->snd_una))
|
|
tp->snd_nxt = tp->snd_una;
|
|
}
|
|
|
|
tp->t_timer[TCPT_REXMT] = 0;
|
|
tp->irs = ti->ti_seq;
|
|
tcp_rcvseqinit(tp);
|
|
tp->t_flags |= TF_ACKNOW;
|
|
if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) {
|
|
soisfconnected(so);
|
|
tp->t_state = TCPS_ESTABLISHED;
|
|
|
|
(void) tcp_reass(tp, (struct tcpiphdr *)0,
|
|
(struct mbuf *)0);
|
|
/*
|
|
* if we didn't have to retransmit the SYN,
|
|
* use its rtt as our initial srtt & rtt var.
|
|
*/
|
|
if (tp->t_rtt)
|
|
tcp_xmit_timer(tp, tp->t_rtt);
|
|
} else
|
|
tp->t_state = TCPS_SYN_RECEIVED;
|
|
|
|
trimthenstep6:
|
|
/*
|
|
* Advance ti->ti_seq to correspond to first data byte.
|
|
* If data, trim to stay within window,
|
|
* dropping FIN if necessary.
|
|
*/
|
|
ti->ti_seq++;
|
|
if (ti->ti_len > tp->rcv_wnd) {
|
|
todrop = ti->ti_len - tp->rcv_wnd;
|
|
m_adj(m, -todrop);
|
|
ti->ti_len = tp->rcv_wnd;
|
|
tiflags &= ~TH_FIN;
|
|
}
|
|
tp->snd_wl1 = ti->ti_seq - 1;
|
|
tp->rcv_up = ti->ti_seq;
|
|
goto step6;
|
|
} /* switch tp->t_state */
|
|
/*
|
|
* States other than LISTEN or SYN_SENT.
|
|
* Check that at least some bytes of segment are within
|
|
* receive window. If segment begins before rcv_nxt,
|
|
* drop leading data (and SYN); if nothing left, just ack.
|
|
*/
|
|
todrop = tp->rcv_nxt - ti->ti_seq;
|
|
if (todrop > 0) {
|
|
if (tiflags & TH_SYN) {
|
|
tiflags &= ~TH_SYN;
|
|
ti->ti_seq++;
|
|
if (ti->ti_urp > 1)
|
|
ti->ti_urp--;
|
|
else
|
|
tiflags &= ~TH_URG;
|
|
todrop--;
|
|
}
|
|
/*
|
|
* Following if statement from Stevens, vol. 2, p. 960.
|
|
*/
|
|
if (todrop > ti->ti_len
|
|
|| (todrop == ti->ti_len && (tiflags & TH_FIN) == 0)) {
|
|
/*
|
|
* Any valid FIN must be to the left of the window.
|
|
* At this point the FIN must be a duplicate or out
|
|
* of sequence; drop it.
|
|
*/
|
|
tiflags &= ~TH_FIN;
|
|
|
|
/*
|
|
* Send an ACK to resynchronize and drop any data.
|
|
* But keep on processing for RST or ACK.
|
|
*/
|
|
tp->t_flags |= TF_ACKNOW;
|
|
todrop = ti->ti_len;
|
|
}
|
|
m_adj(m, todrop);
|
|
ti->ti_seq += todrop;
|
|
ti->ti_len -= todrop;
|
|
if (ti->ti_urp > todrop)
|
|
ti->ti_urp -= todrop;
|
|
else {
|
|
tiflags &= ~TH_URG;
|
|
ti->ti_urp = 0;
|
|
}
|
|
}
|
|
/*
|
|
* If new data are received on a connection after the
|
|
* user processes are gone, then RST the other end.
|
|
*/
|
|
if ((so->so_state & SS_NOFDREF) &&
|
|
tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) {
|
|
tp = tcp_close(tp);
|
|
goto dropwithreset;
|
|
}
|
|
|
|
/*
|
|
* If segment ends after window, drop trailing data
|
|
* (and PUSH and FIN); if nothing left, just ACK.
|
|
*/
|
|
todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd);
|
|
if (todrop > 0) {
|
|
if (todrop >= ti->ti_len) {
|
|
/*
|
|
* If a new connection request is received
|
|
* while in TIME_WAIT, drop the old connection
|
|
* and start over if the sequence numbers
|
|
* are above the previous ones.
|
|
*/
|
|
if (tiflags & TH_SYN &&
|
|
tp->t_state == TCPS_TIME_WAIT &&
|
|
SEQ_GT(ti->ti_seq, tp->rcv_nxt)) {
|
|
iss = tp->rcv_nxt + TCP_ISSINCR;
|
|
tp = tcp_close(tp);
|
|
goto findso;
|
|
}
|
|
/*
|
|
* If window is closed can only take segments at
|
|
* window edge, and have to drop data and PUSH from
|
|
* incoming segments. Continue processing, but
|
|
* remember to ack. Otherwise, drop segment
|
|
* and ack.
|
|
*/
|
|
if (tp->rcv_wnd == 0 && ti->ti_seq == tp->rcv_nxt) {
|
|
tp->t_flags |= TF_ACKNOW;
|
|
} else {
|
|
goto dropafterack;
|
|
}
|
|
}
|
|
m_adj(m, -todrop);
|
|
ti->ti_len -= todrop;
|
|
tiflags &= ~(TH_PUSH|TH_FIN);
|
|
}
|
|
|
|
/*
|
|
* If the RST bit is set examine the state:
|
|
* SYN_RECEIVED STATE:
|
|
* If passive open, return to LISTEN state.
|
|
* If active open, inform user that connection was refused.
|
|
* ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES:
|
|
* Inform user that connection was reset, and close tcb.
|
|
* CLOSING, LAST_ACK, TIME_WAIT STATES
|
|
* Close the tcb.
|
|
*/
|
|
if (tiflags&TH_RST) switch (tp->t_state) {
|
|
|
|
case TCPS_SYN_RECEIVED:
|
|
case TCPS_ESTABLISHED:
|
|
case TCPS_FIN_WAIT_1:
|
|
case TCPS_FIN_WAIT_2:
|
|
case TCPS_CLOSE_WAIT:
|
|
tp->t_state = TCPS_CLOSED;
|
|
tcp_close(tp);
|
|
goto drop;
|
|
|
|
case TCPS_CLOSING:
|
|
case TCPS_LAST_ACK:
|
|
case TCPS_TIME_WAIT:
|
|
tcp_close(tp);
|
|
goto drop;
|
|
}
|
|
|
|
/*
|
|
* If a SYN is in the window, then this is an
|
|
* error and we send an RST and drop the connection.
|
|
*/
|
|
if (tiflags & TH_SYN) {
|
|
tp = tcp_drop(tp,0);
|
|
goto dropwithreset;
|
|
}
|
|
|
|
/*
|
|
* If the ACK bit is off we drop the segment and return.
|
|
*/
|
|
if ((tiflags & TH_ACK) == 0) goto drop;
|
|
|
|
/*
|
|
* Ack processing.
|
|
*/
|
|
switch (tp->t_state) {
|
|
/*
|
|
* In SYN_RECEIVED state if the ack ACKs our SYN then enter
|
|
* ESTABLISHED state and continue processing, otherwise
|
|
* send an RST. una<=ack<=max
|
|
*/
|
|
case TCPS_SYN_RECEIVED:
|
|
|
|
if (SEQ_GT(tp->snd_una, ti->ti_ack) ||
|
|
SEQ_GT(ti->ti_ack, tp->snd_max))
|
|
goto dropwithreset;
|
|
tp->t_state = TCPS_ESTABLISHED;
|
|
/*
|
|
* The sent SYN is ack'ed with our sequence number +1
|
|
* The first data byte already in the buffer will get
|
|
* lost if no correction is made. This is only needed for
|
|
* SS_CTL since the buffer is empty otherwise.
|
|
* tp->snd_una++; or:
|
|
*/
|
|
tp->snd_una=ti->ti_ack;
|
|
if (so->so_state & SS_CTL) {
|
|
/* So tcp_ctl reports the right state */
|
|
ret = tcp_ctl(so);
|
|
if (ret == 1) {
|
|
soisfconnected(so);
|
|
so->so_state &= ~SS_CTL; /* success XXX */
|
|
} else if (ret == 2) {
|
|
so->so_state &= SS_PERSISTENT_MASK;
|
|
so->so_state |= SS_NOFDREF; /* CTL_CMD */
|
|
} else {
|
|
needoutput = 1;
|
|
tp->t_state = TCPS_FIN_WAIT_1;
|
|
}
|
|
} else {
|
|
soisfconnected(so);
|
|
}
|
|
|
|
(void) tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)0);
|
|
tp->snd_wl1 = ti->ti_seq - 1;
|
|
/* Avoid ack processing; snd_una==ti_ack => dup ack */
|
|
goto synrx_to_est;
|
|
/* fall into ... */
|
|
|
|
/*
|
|
* In ESTABLISHED state: drop duplicate ACKs; ACK out of range
|
|
* ACKs. If the ack is in the range
|
|
* tp->snd_una < ti->ti_ack <= tp->snd_max
|
|
* then advance tp->snd_una to ti->ti_ack and drop
|
|
* data from the retransmission queue. If this ACK reflects
|
|
* more up to date window information we update our window information.
|
|
*/
|
|
case TCPS_ESTABLISHED:
|
|
case TCPS_FIN_WAIT_1:
|
|
case TCPS_FIN_WAIT_2:
|
|
case TCPS_CLOSE_WAIT:
|
|
case TCPS_CLOSING:
|
|
case TCPS_LAST_ACK:
|
|
case TCPS_TIME_WAIT:
|
|
|
|
if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) {
|
|
if (ti->ti_len == 0 && tiwin == tp->snd_wnd) {
|
|
DEBUG_MISC((dfd," dup ack m = %lx so = %lx \n",
|
|
(long )m, (long )so));
|
|
/*
|
|
* If we have outstanding data (other than
|
|
* a window probe), this is a completely
|
|
* duplicate ack (ie, window info didn't
|
|
* change), the ack is the biggest we've
|
|
* seen and we've seen exactly our rexmt
|
|
* threshold of them, assume a packet
|
|
* has been dropped and retransmit it.
|
|
* Kludge snd_nxt & the congestion
|
|
* window so we send only this one
|
|
* packet.
|
|
*
|
|
* We know we're losing at the current
|
|
* window size so do congestion avoidance
|
|
* (set ssthresh to half the current window
|
|
* and pull our congestion window back to
|
|
* the new ssthresh).
|
|
*
|
|
* Dup acks mean that packets have left the
|
|
* network (they're now cached at the receiver)
|
|
* so bump cwnd by the amount in the receiver
|
|
* to keep a constant cwnd packets in the
|
|
* network.
|
|
*/
|
|
if (tp->t_timer[TCPT_REXMT] == 0 ||
|
|
ti->ti_ack != tp->snd_una)
|
|
tp->t_dupacks = 0;
|
|
else if (++tp->t_dupacks == TCPREXMTTHRESH) {
|
|
tcp_seq onxt = tp->snd_nxt;
|
|
u_int win =
|
|
min(tp->snd_wnd, tp->snd_cwnd) / 2 /
|
|
tp->t_maxseg;
|
|
|
|
if (win < 2)
|
|
win = 2;
|
|
tp->snd_ssthresh = win * tp->t_maxseg;
|
|
tp->t_timer[TCPT_REXMT] = 0;
|
|
tp->t_rtt = 0;
|
|
tp->snd_nxt = ti->ti_ack;
|
|
tp->snd_cwnd = tp->t_maxseg;
|
|
(void) tcp_output(tp);
|
|
tp->snd_cwnd = tp->snd_ssthresh +
|
|
tp->t_maxseg * tp->t_dupacks;
|
|
if (SEQ_GT(onxt, tp->snd_nxt))
|
|
tp->snd_nxt = onxt;
|
|
goto drop;
|
|
} else if (tp->t_dupacks > TCPREXMTTHRESH) {
|
|
tp->snd_cwnd += tp->t_maxseg;
|
|
(void) tcp_output(tp);
|
|
goto drop;
|
|
}
|
|
} else
|
|
tp->t_dupacks = 0;
|
|
break;
|
|
}
|
|
synrx_to_est:
|
|
/*
|
|
* If the congestion window was inflated to account
|
|
* for the other side's cached packets, retract it.
|
|
*/
|
|
if (tp->t_dupacks > TCPREXMTTHRESH &&
|
|
tp->snd_cwnd > tp->snd_ssthresh)
|
|
tp->snd_cwnd = tp->snd_ssthresh;
|
|
tp->t_dupacks = 0;
|
|
if (SEQ_GT(ti->ti_ack, tp->snd_max)) {
|
|
goto dropafterack;
|
|
}
|
|
acked = ti->ti_ack - tp->snd_una;
|
|
|
|
/*
|
|
* If transmit timer is running and timed sequence
|
|
* number was acked, update smoothed round trip time.
|
|
* Since we now have an rtt measurement, cancel the
|
|
* timer backoff (cf., Phil Karn's retransmit alg.).
|
|
* Recompute the initial retransmit timer.
|
|
*/
|
|
if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq))
|
|
tcp_xmit_timer(tp,tp->t_rtt);
|
|
|
|
/*
|
|
* If all outstanding data is acked, stop retransmit
|
|
* timer and remember to restart (more output or persist).
|
|
* If there is more data to be acked, restart retransmit
|
|
* timer, using current (possibly backed-off) value.
|
|
*/
|
|
if (ti->ti_ack == tp->snd_max) {
|
|
tp->t_timer[TCPT_REXMT] = 0;
|
|
needoutput = 1;
|
|
} else if (tp->t_timer[TCPT_PERSIST] == 0)
|
|
tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
|
|
/*
|
|
* When new data is acked, open the congestion window.
|
|
* If the window gives us less than ssthresh packets
|
|
* in flight, open exponentially (maxseg per packet).
|
|
* Otherwise open linearly: maxseg per window
|
|
* (maxseg^2 / cwnd per packet).
|
|
*/
|
|
{
|
|
register u_int cw = tp->snd_cwnd;
|
|
register u_int incr = tp->t_maxseg;
|
|
|
|
if (cw > tp->snd_ssthresh)
|
|
incr = incr * incr / cw;
|
|
tp->snd_cwnd = min(cw + incr, TCP_MAXWIN<<tp->snd_scale);
|
|
}
|
|
if (acked > so->so_snd.sb_cc) {
|
|
tp->snd_wnd -= so->so_snd.sb_cc;
|
|
sbdrop(&so->so_snd, (int )so->so_snd.sb_cc);
|
|
ourfinisacked = 1;
|
|
} else {
|
|
sbdrop(&so->so_snd, acked);
|
|
tp->snd_wnd -= acked;
|
|
ourfinisacked = 0;
|
|
}
|
|
tp->snd_una = ti->ti_ack;
|
|
if (SEQ_LT(tp->snd_nxt, tp->snd_una))
|
|
tp->snd_nxt = tp->snd_una;
|
|
|
|
switch (tp->t_state) {
|
|
|
|
/*
|
|
* In FIN_WAIT_1 STATE in addition to the processing
|
|
* for the ESTABLISHED state if our FIN is now acknowledged
|
|
* then enter FIN_WAIT_2.
|
|
*/
|
|
case TCPS_FIN_WAIT_1:
|
|
if (ourfinisacked) {
|
|
/*
|
|
* If we can't receive any more
|
|
* data, then closing user can proceed.
|
|
* Starting the timer is contrary to the
|
|
* specification, but if we don't get a FIN
|
|
* we'll hang forever.
|
|
*/
|
|
if (so->so_state & SS_FCANTRCVMORE) {
|
|
tp->t_timer[TCPT_2MSL] = TCP_MAXIDLE;
|
|
}
|
|
tp->t_state = TCPS_FIN_WAIT_2;
|
|
}
|
|
break;
|
|
|
|
/*
|
|
* In CLOSING STATE in addition to the processing for
|
|
* the ESTABLISHED state if the ACK acknowledges our FIN
|
|
* then enter the TIME-WAIT state, otherwise ignore
|
|
* the segment.
|
|
*/
|
|
case TCPS_CLOSING:
|
|
if (ourfinisacked) {
|
|
tp->t_state = TCPS_TIME_WAIT;
|
|
tcp_canceltimers(tp);
|
|
tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
|
|
}
|
|
break;
|
|
|
|
/*
|
|
* In LAST_ACK, we may still be waiting for data to drain
|
|
* and/or to be acked, as well as for the ack of our FIN.
|
|
* If our FIN is now acknowledged, delete the TCB,
|
|
* enter the closed state and return.
|
|
*/
|
|
case TCPS_LAST_ACK:
|
|
if (ourfinisacked) {
|
|
tcp_close(tp);
|
|
goto drop;
|
|
}
|
|
break;
|
|
|
|
/*
|
|
* In TIME_WAIT state the only thing that should arrive
|
|
* is a retransmission of the remote FIN. Acknowledge
|
|
* it and restart the finack timer.
|
|
*/
|
|
case TCPS_TIME_WAIT:
|
|
tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
|
|
goto dropafterack;
|
|
}
|
|
} /* switch(tp->t_state) */
|
|
|
|
step6:
|
|
/*
|
|
* Update window information.
|
|
* Don't look at window if no ACK: TAC's send garbage on first SYN.
|
|
*/
|
|
if ((tiflags & TH_ACK) &&
|
|
(SEQ_LT(tp->snd_wl1, ti->ti_seq) ||
|
|
(tp->snd_wl1 == ti->ti_seq && (SEQ_LT(tp->snd_wl2, ti->ti_ack) ||
|
|
(tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd))))) {
|
|
tp->snd_wnd = tiwin;
|
|
tp->snd_wl1 = ti->ti_seq;
|
|
tp->snd_wl2 = ti->ti_ack;
|
|
if (tp->snd_wnd > tp->max_sndwnd)
|
|
tp->max_sndwnd = tp->snd_wnd;
|
|
needoutput = 1;
|
|
}
|
|
|
|
/*
|
|
* Process segments with URG.
|
|
*/
|
|
if ((tiflags & TH_URG) && ti->ti_urp &&
|
|
TCPS_HAVERCVDFIN(tp->t_state) == 0) {
|
|
/*
|
|
* This is a kludge, but if we receive and accept
|
|
* random urgent pointers, we'll crash in
|
|
* soreceive. It's hard to imagine someone
|
|
* actually wanting to send this much urgent data.
|
|
*/
|
|
if (ti->ti_urp + so->so_rcv.sb_cc > so->so_rcv.sb_datalen) {
|
|
ti->ti_urp = 0;
|
|
tiflags &= ~TH_URG;
|
|
goto dodata;
|
|
}
|
|
/*
|
|
* If this segment advances the known urgent pointer,
|
|
* then mark the data stream. This should not happen
|
|
* in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
|
|
* a FIN has been received from the remote side.
|
|
* In these states we ignore the URG.
|
|
*
|
|
* According to RFC961 (Assigned Protocols),
|
|
* the urgent pointer points to the last octet
|
|
* of urgent data. We continue, however,
|
|
* to consider it to indicate the first octet
|
|
* of data past the urgent section as the original
|
|
* spec states (in one of two places).
|
|
*/
|
|
if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) {
|
|
tp->rcv_up = ti->ti_seq + ti->ti_urp;
|
|
so->so_urgc = so->so_rcv.sb_cc +
|
|
(tp->rcv_up - tp->rcv_nxt); /* -1; */
|
|
tp->rcv_up = ti->ti_seq + ti->ti_urp;
|
|
|
|
}
|
|
} else
|
|
/*
|
|
* If no out of band data is expected,
|
|
* pull receive urgent pointer along
|
|
* with the receive window.
|
|
*/
|
|
if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
|
|
tp->rcv_up = tp->rcv_nxt;
|
|
dodata:
|
|
|
|
/*
|
|
* Process the segment text, merging it into the TCP sequencing queue,
|
|
* and arranging for acknowledgment of receipt if necessary.
|
|
* This process logically involves adjusting tp->rcv_wnd as data
|
|
* is presented to the user (this happens in tcp_usrreq.c,
|
|
* case PRU_RCVD). If a FIN has already been received on this
|
|
* connection then we just ignore the text.
|
|
*/
|
|
if ((ti->ti_len || (tiflags&TH_FIN)) &&
|
|
TCPS_HAVERCVDFIN(tp->t_state) == 0) {
|
|
TCP_REASS(tp, ti, m, so, tiflags);
|
|
} else {
|
|
m_free(m);
|
|
tiflags &= ~TH_FIN;
|
|
}
|
|
|
|
/*
|
|
* If FIN is received ACK the FIN and let the user know
|
|
* that the connection is closing.
|
|
*/
|
|
if (tiflags & TH_FIN) {
|
|
if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
|
|
/*
|
|
* If we receive a FIN we can't send more data,
|
|
* set it SS_FDRAIN
|
|
* Shutdown the socket if there is no rx data in the
|
|
* buffer.
|
|
* soread() is called on completion of shutdown() and
|
|
* will got to TCPS_LAST_ACK, and use tcp_output()
|
|
* to send the FIN.
|
|
*/
|
|
sofwdrain(so);
|
|
|
|
tp->t_flags |= TF_ACKNOW;
|
|
tp->rcv_nxt++;
|
|
}
|
|
switch (tp->t_state) {
|
|
|
|
/*
|
|
* In SYN_RECEIVED and ESTABLISHED STATES
|
|
* enter the CLOSE_WAIT state.
|
|
*/
|
|
case TCPS_SYN_RECEIVED:
|
|
case TCPS_ESTABLISHED:
|
|
if(so->so_emu == EMU_CTL) /* no shutdown on socket */
|
|
tp->t_state = TCPS_LAST_ACK;
|
|
else
|
|
tp->t_state = TCPS_CLOSE_WAIT;
|
|
break;
|
|
|
|
/*
|
|
* If still in FIN_WAIT_1 STATE FIN has not been acked so
|
|
* enter the CLOSING state.
|
|
*/
|
|
case TCPS_FIN_WAIT_1:
|
|
tp->t_state = TCPS_CLOSING;
|
|
break;
|
|
|
|
/*
|
|
* In FIN_WAIT_2 state enter the TIME_WAIT state,
|
|
* starting the time-wait timer, turning off the other
|
|
* standard timers.
|
|
*/
|
|
case TCPS_FIN_WAIT_2:
|
|
tp->t_state = TCPS_TIME_WAIT;
|
|
tcp_canceltimers(tp);
|
|
tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
|
|
break;
|
|
|
|
/*
|
|
* In TIME_WAIT state restart the 2 MSL time_wait timer.
|
|
*/
|
|
case TCPS_TIME_WAIT:
|
|
tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
|
|
break;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If this is a small packet, then ACK now - with Nagel
|
|
* congestion avoidance sender won't send more until
|
|
* he gets an ACK.
|
|
*
|
|
* See above.
|
|
*/
|
|
if (ti->ti_len && (unsigned)ti->ti_len <= 5 &&
|
|
((struct tcpiphdr_2 *)ti)->first_char == (char)27) {
|
|
tp->t_flags |= TF_ACKNOW;
|
|
}
|
|
|
|
/*
|
|
* Return any desired output.
|
|
*/
|
|
if (needoutput || (tp->t_flags & TF_ACKNOW)) {
|
|
(void) tcp_output(tp);
|
|
}
|
|
return;
|
|
|
|
dropafterack:
|
|
/*
|
|
* Generate an ACK dropping incoming segment if it occupies
|
|
* sequence space, where the ACK reflects our state.
|
|
*/
|
|
if (tiflags & TH_RST)
|
|
goto drop;
|
|
m_freem(m);
|
|
tp->t_flags |= TF_ACKNOW;
|
|
(void) tcp_output(tp);
|
|
return;
|
|
|
|
dropwithreset:
|
|
/* reuses m if m!=NULL, m_free() unnecessary */
|
|
if (tiflags & TH_ACK)
|
|
tcp_respond(tp, ti, m, (tcp_seq)0, ti->ti_ack, TH_RST);
|
|
else {
|
|
if (tiflags & TH_SYN) ti->ti_len++;
|
|
tcp_respond(tp, ti, m, ti->ti_seq+ti->ti_len, (tcp_seq)0,
|
|
TH_RST|TH_ACK);
|
|
}
|
|
|
|
return;
|
|
|
|
drop:
|
|
/*
|
|
* Drop space held by incoming segment and return.
|
|
*/
|
|
m_free(m);
|
|
|
|
return;
|
|
}
|
|
|
|
static void
|
|
tcp_dooptions(struct tcpcb *tp, u_char *cp, int cnt, struct tcpiphdr *ti)
|
|
{
|
|
u_int16_t mss;
|
|
int opt, optlen;
|
|
|
|
DEBUG_CALL("tcp_dooptions");
|
|
DEBUG_ARGS((dfd," tp = %lx cnt=%i \n", (long )tp, cnt));
|
|
|
|
for (; cnt > 0; cnt -= optlen, cp += optlen) {
|
|
opt = cp[0];
|
|
if (opt == TCPOPT_EOL)
|
|
break;
|
|
if (opt == TCPOPT_NOP)
|
|
optlen = 1;
|
|
else {
|
|
optlen = cp[1];
|
|
if (optlen <= 0)
|
|
break;
|
|
}
|
|
switch (opt) {
|
|
|
|
default:
|
|
continue;
|
|
|
|
case TCPOPT_MAXSEG:
|
|
if (optlen != TCPOLEN_MAXSEG)
|
|
continue;
|
|
if (!(ti->ti_flags & TH_SYN))
|
|
continue;
|
|
memcpy((char *) &mss, (char *) cp + 2, sizeof(mss));
|
|
NTOHS(mss);
|
|
(void) tcp_mss(tp, mss); /* sets t_maxseg */
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* Pull out of band byte out of a segment so
|
|
* it doesn't appear in the user's data queue.
|
|
* It is still reflected in the segment length for
|
|
* sequencing purposes.
|
|
*/
|
|
|
|
#ifdef notdef
|
|
|
|
void
|
|
tcp_pulloutofband(so, ti, m)
|
|
struct socket *so;
|
|
struct tcpiphdr *ti;
|
|
register struct mbuf *m;
|
|
{
|
|
int cnt = ti->ti_urp - 1;
|
|
|
|
while (cnt >= 0) {
|
|
if (m->m_len > cnt) {
|
|
char *cp = mtod(m, caddr_t) + cnt;
|
|
struct tcpcb *tp = sototcpcb(so);
|
|
|
|
tp->t_iobc = *cp;
|
|
tp->t_oobflags |= TCPOOB_HAVEDATA;
|
|
memcpy(sp, cp+1, (unsigned)(m->m_len - cnt - 1));
|
|
m->m_len--;
|
|
return;
|
|
}
|
|
cnt -= m->m_len;
|
|
m = m->m_next; /* XXX WRONG! Fix it! */
|
|
if (m == 0)
|
|
break;
|
|
}
|
|
panic("tcp_pulloutofband");
|
|
}
|
|
|
|
#endif /* notdef */
|
|
|
|
/*
|
|
* Collect new round-trip time estimate
|
|
* and update averages and current timeout.
|
|
*/
|
|
|
|
static void
|
|
tcp_xmit_timer(register struct tcpcb *tp, int rtt)
|
|
{
|
|
register short delta;
|
|
|
|
DEBUG_CALL("tcp_xmit_timer");
|
|
DEBUG_ARG("tp = %lx", (long)tp);
|
|
DEBUG_ARG("rtt = %d", rtt);
|
|
|
|
if (tp->t_srtt != 0) {
|
|
/*
|
|
* srtt is stored as fixed point with 3 bits after the
|
|
* binary point (i.e., scaled by 8). The following magic
|
|
* is equivalent to the smoothing algorithm in rfc793 with
|
|
* an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
|
|
* point). Adjust rtt to origin 0.
|
|
*/
|
|
delta = rtt - 1 - (tp->t_srtt >> TCP_RTT_SHIFT);
|
|
if ((tp->t_srtt += delta) <= 0)
|
|
tp->t_srtt = 1;
|
|
/*
|
|
* We accumulate a smoothed rtt variance (actually, a
|
|
* smoothed mean difference), then set the retransmit
|
|
* timer to smoothed rtt + 4 times the smoothed variance.
|
|
* rttvar is stored as fixed point with 2 bits after the
|
|
* binary point (scaled by 4). The following is
|
|
* equivalent to rfc793 smoothing with an alpha of .75
|
|
* (rttvar = rttvar*3/4 + |delta| / 4). This replaces
|
|
* rfc793's wired-in beta.
|
|
*/
|
|
if (delta < 0)
|
|
delta = -delta;
|
|
delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT);
|
|
if ((tp->t_rttvar += delta) <= 0)
|
|
tp->t_rttvar = 1;
|
|
} else {
|
|
/*
|
|
* No rtt measurement yet - use the unsmoothed rtt.
|
|
* Set the variance to half the rtt (so our first
|
|
* retransmit happens at 3*rtt).
|
|
*/
|
|
tp->t_srtt = rtt << TCP_RTT_SHIFT;
|
|
tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
|
|
}
|
|
tp->t_rtt = 0;
|
|
tp->t_rxtshift = 0;
|
|
|
|
/*
|
|
* the retransmit should happen at rtt + 4 * rttvar.
|
|
* Because of the way we do the smoothing, srtt and rttvar
|
|
* will each average +1/2 tick of bias. When we compute
|
|
* the retransmit timer, we want 1/2 tick of rounding and
|
|
* 1 extra tick because of +-1/2 tick uncertainty in the
|
|
* firing of the timer. The bias will give us exactly the
|
|
* 1.5 tick we need. But, because the bias is
|
|
* statistical, we have to test that we don't drop below
|
|
* the minimum feasible timer (which is 2 ticks).
|
|
*/
|
|
TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
|
|
(short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */
|
|
|
|
/*
|
|
* We received an ack for a packet that wasn't retransmitted;
|
|
* it is probably safe to discard any error indications we've
|
|
* received recently. This isn't quite right, but close enough
|
|
* for now (a route might have failed after we sent a segment,
|
|
* and the return path might not be symmetrical).
|
|
*/
|
|
tp->t_softerror = 0;
|
|
}
|
|
|
|
/*
|
|
* Determine a reasonable value for maxseg size.
|
|
* If the route is known, check route for mtu.
|
|
* If none, use an mss that can be handled on the outgoing
|
|
* interface without forcing IP to fragment; if bigger than
|
|
* an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
|
|
* to utilize large mbufs. If no route is found, route has no mtu,
|
|
* or the destination isn't local, use a default, hopefully conservative
|
|
* size (usually 512 or the default IP max size, but no more than the mtu
|
|
* of the interface), as we can't discover anything about intervening
|
|
* gateways or networks. We also initialize the congestion/slow start
|
|
* window to be a single segment if the destination isn't local.
|
|
* While looking at the routing entry, we also initialize other path-dependent
|
|
* parameters from pre-set or cached values in the routing entry.
|
|
*/
|
|
|
|
int
|
|
tcp_mss(struct tcpcb *tp, u_int offer)
|
|
{
|
|
struct socket *so = tp->t_socket;
|
|
int mss;
|
|
|
|
DEBUG_CALL("tcp_mss");
|
|
DEBUG_ARG("tp = %lx", (long)tp);
|
|
DEBUG_ARG("offer = %d", offer);
|
|
|
|
mss = min(IF_MTU, IF_MRU) - sizeof(struct tcpiphdr);
|
|
if (offer)
|
|
mss = min(mss, offer);
|
|
mss = max(mss, 32);
|
|
if (mss < tp->t_maxseg || offer != 0)
|
|
tp->t_maxseg = mss;
|
|
|
|
tp->snd_cwnd = mss;
|
|
|
|
sbreserve(&so->so_snd, TCP_SNDSPACE + ((TCP_SNDSPACE % mss) ?
|
|
(mss - (TCP_SNDSPACE % mss)) :
|
|
0));
|
|
sbreserve(&so->so_rcv, TCP_RCVSPACE + ((TCP_RCVSPACE % mss) ?
|
|
(mss - (TCP_RCVSPACE % mss)) :
|
|
0));
|
|
|
|
DEBUG_MISC((dfd, " returning mss = %d\n", mss));
|
|
|
|
return mss;
|
|
}
|