3151 lines
87 KiB
C
3151 lines
87 KiB
C
/*
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* Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
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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 8.12 (Berkeley) 5/24/95
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* $FreeBSD$
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*/
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#include "opt_ipfw.h" /* for ipfw_fwd */
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#include "opt_inet6.h"
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#include "opt_ipsec.h"
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#include "opt_mac.h"
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#include "opt_tcpdebug.h"
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#include "opt_tcp_input.h"
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#include <sys/param.h>
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#include <sys/kernel.h>
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#include <sys/mac.h>
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#include <sys/malloc.h>
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#include <sys/mbuf.h>
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#include <sys/proc.h> /* for proc0 declaration */
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#include <sys/protosw.h>
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#include <sys/signalvar.h>
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#include <sys/socket.h>
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#include <sys/socketvar.h>
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#include <sys/sysctl.h>
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#include <sys/syslog.h>
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#include <sys/systm.h>
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#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
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#include <net/if.h>
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#include <net/route.h>
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#include <netinet/in.h>
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#include <netinet/in_pcb.h>
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#include <netinet/in_systm.h>
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#include <netinet/in_var.h>
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#include <netinet/ip.h>
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#include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */
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#include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
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#include <netinet/ip_var.h>
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#include <netinet/ip6.h>
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#include <netinet/icmp6.h>
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#include <netinet6/in6_pcb.h>
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#include <netinet6/ip6_var.h>
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#include <netinet6/nd6.h>
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#include <netinet/tcp.h>
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#include <netinet/tcp_fsm.h>
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#include <netinet/tcp_seq.h>
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#include <netinet/tcp_timer.h>
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#include <netinet/tcp_var.h>
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#include <netinet6/tcp6_var.h>
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#include <netinet/tcpip.h>
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#ifdef TCPDEBUG
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#include <netinet/tcp_debug.h>
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#endif /* TCPDEBUG */
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#ifdef FAST_IPSEC
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#include <netipsec/ipsec.h>
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#include <netipsec/ipsec6.h>
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#endif /*FAST_IPSEC*/
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#ifdef IPSEC
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#include <netinet6/ipsec.h>
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#include <netinet6/ipsec6.h>
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#include <netkey/key.h>
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#endif /*IPSEC*/
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#include <machine/in_cksum.h>
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MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry");
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static const int tcprexmtthresh = 3;
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tcp_cc tcp_ccgen;
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struct tcpstat tcpstat;
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SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW,
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&tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
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static int log_in_vain = 0;
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SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
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&log_in_vain, 0, "Log all incoming TCP connections");
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static int blackhole = 0;
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SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
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&blackhole, 0, "Do not send RST when dropping refused connections");
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int tcp_delack_enabled = 1;
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SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
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&tcp_delack_enabled, 0,
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"Delay ACK to try and piggyback it onto a data packet");
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#ifdef TCP_DROP_SYNFIN
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static int drop_synfin = 0;
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SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
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&drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
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#endif
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static int tcp_do_rfc3042 = 1;
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SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW,
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&tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)");
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static int tcp_do_rfc3390 = 1;
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SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW,
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&tcp_do_rfc3390, 0,
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"Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
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struct inpcbhead tcb;
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#define tcb6 tcb /* for KAME src sync over BSD*'s */
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struct inpcbinfo tcbinfo;
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struct mtx *tcbinfo_mtx;
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static void tcp_dooptions(struct tcpopt *, u_char *, int, int);
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static void tcp_pulloutofband(struct socket *,
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struct tcphdr *, struct mbuf *, int);
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static int tcp_reass(struct tcpcb *, struct tcphdr *, int *,
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struct mbuf *);
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static void tcp_xmit_timer(struct tcpcb *, int);
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static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *);
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static int tcp_timewait(struct tcptw *, struct tcpopt *,
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struct tcphdr *, struct mbuf *, int);
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/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
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#ifdef INET6
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#define ND6_HINT(tp) \
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do { \
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if ((tp) && (tp)->t_inpcb && \
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((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \
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nd6_nud_hint(NULL, NULL, 0); \
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} while (0)
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#else
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#define ND6_HINT(tp)
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#endif
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/*
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* Indicate whether this ack should be delayed. We can delay the ack if
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* - there is no delayed ack timer in progress and
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* - our last ack wasn't a 0-sized window. We never want to delay
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* the ack that opens up a 0-sized window and
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* - delayed acks are enabled or
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* - this is a half-synchronized T/TCP connection.
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*/
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#define DELAY_ACK(tp) \
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((!callout_active(tp->tt_delack) && \
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(tp->t_flags & TF_RXWIN0SENT) == 0) && \
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(tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN)))
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static int
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tcp_reass(tp, th, tlenp, m)
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register struct tcpcb *tp;
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register struct tcphdr *th;
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int *tlenp;
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struct mbuf *m;
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{
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struct tseg_qent *q;
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struct tseg_qent *p = NULL;
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struct tseg_qent *nq;
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struct tseg_qent *te;
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struct socket *so = tp->t_inpcb->inp_socket;
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int flags;
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/*
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* Call with th==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 (th == 0)
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goto present;
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/* Allocate a new queue entry. If we can't, just drop the pkt. XXX */
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MALLOC(te, struct tseg_qent *, sizeof (struct tseg_qent), M_TSEGQ,
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M_NOWAIT);
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if (te == NULL) {
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tcpstat.tcps_rcvmemdrop++;
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m_freem(m);
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return (0);
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}
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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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LIST_FOREACH(q, &tp->t_segq, tqe_q) {
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if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
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break;
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p = q;
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}
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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 (p != NULL) {
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register int i;
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/* conversion to int (in i) handles seq wraparound */
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i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
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if (i > 0) {
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if (i >= *tlenp) {
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tcpstat.tcps_rcvduppack++;
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tcpstat.tcps_rcvdupbyte += *tlenp;
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m_freem(m);
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FREE(te, M_TSEGQ);
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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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*tlenp -= i;
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th->th_seq += i;
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}
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}
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tcpstat.tcps_rcvoopack++;
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tcpstat.tcps_rcvoobyte += *tlenp;
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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) {
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register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
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if (i <= 0)
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break;
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if (i < q->tqe_len) {
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q->tqe_th->th_seq += i;
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q->tqe_len -= i;
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m_adj(q->tqe_m, i);
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break;
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}
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nq = LIST_NEXT(q, tqe_q);
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LIST_REMOVE(q, tqe_q);
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m_freem(q->tqe_m);
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FREE(q, M_TSEGQ);
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q = nq;
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}
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/* Insert the new segment queue entry into place. */
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te->tqe_m = m;
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te->tqe_th = th;
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te->tqe_len = *tlenp;
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if (p == NULL) {
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LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
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} else {
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LIST_INSERT_AFTER(p, te, tqe_q);
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}
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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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q = LIST_FIRST(&tp->t_segq);
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if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
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return (0);
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do {
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tp->rcv_nxt += q->tqe_len;
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flags = q->tqe_th->th_flags & TH_FIN;
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nq = LIST_NEXT(q, tqe_q);
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LIST_REMOVE(q, tqe_q);
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if (so->so_state & SS_CANTRCVMORE)
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m_freem(q->tqe_m);
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else
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sbappendstream(&so->so_rcv, q->tqe_m);
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FREE(q, M_TSEGQ);
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q = nq;
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} while (q && q->tqe_th->th_seq == tp->rcv_nxt);
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ND6_HINT(tp);
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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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#ifdef INET6
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int
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tcp6_input(mp, offp, proto)
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struct mbuf **mp;
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int *offp, proto;
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{
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register struct mbuf *m = *mp;
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struct in6_ifaddr *ia6;
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IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
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/*
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* draft-itojun-ipv6-tcp-to-anycast
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* better place to put this in?
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*/
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ia6 = ip6_getdstifaddr(m);
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if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
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struct ip6_hdr *ip6;
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ip6 = mtod(m, struct ip6_hdr *);
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icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
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(caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
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return IPPROTO_DONE;
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}
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tcp_input(m, *offp);
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return IPPROTO_DONE;
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}
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#endif
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void
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tcp_input(m, off0)
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register struct mbuf *m;
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int off0;
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{
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register struct tcphdr *th;
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register struct ip *ip = NULL;
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register struct ipovly *ipov;
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register struct inpcb *inp = NULL;
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u_char *optp = NULL;
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int optlen = 0;
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int len, tlen, off;
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int drop_hdrlen;
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register struct tcpcb *tp = 0;
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register int thflags;
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struct socket *so = 0;
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int todrop, acked, ourfinisacked, needoutput = 0;
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u_long tiwin;
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struct tcpopt to; /* options in this segment */
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struct rmxp_tao tao; /* our TAO cache entry */
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int headlocked = 0;
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struct sockaddr_in *next_hop = NULL;
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int rstreason; /* For badport_bandlim accounting purposes */
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struct ip6_hdr *ip6 = NULL;
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#ifdef INET6
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int isipv6;
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#else
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const int isipv6 = 0;
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#endif
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#ifdef TCPDEBUG
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/*
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* The size of tcp_saveipgen must be the size of the max ip header,
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* now IPv6.
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*/
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u_char tcp_saveipgen[40];
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struct tcphdr tcp_savetcp;
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short ostate = 0;
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#endif
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/* Grab info from MT_TAG mbufs prepended to the chain. */
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for (;m && m->m_type == MT_TAG; m = m->m_next) {
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if (m->_m_tag_id == PACKET_TAG_IPFORWARD)
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next_hop = (struct sockaddr_in *)m->m_hdr.mh_data;
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}
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#ifdef INET6
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isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
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#endif
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bzero(&tao, sizeof(tao));
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bzero((char *)&to, sizeof(to));
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|
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tcpstat.tcps_rcvtotal++;
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|
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if (isipv6) {
|
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/* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
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ip6 = mtod(m, struct ip6_hdr *);
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tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
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if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
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tcpstat.tcps_rcvbadsum++;
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goto drop;
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}
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th = (struct tcphdr *)((caddr_t)ip6 + off0);
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|
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/*
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* Be proactive about unspecified IPv6 address in source.
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* As we use all-zero to indicate unbounded/unconnected pcb,
|
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* unspecified IPv6 address can be used to confuse us.
|
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*
|
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* Note that packets with unspecified IPv6 destination is
|
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* already dropped in ip6_input.
|
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*/
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if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
|
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/* XXX stat */
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goto drop;
|
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}
|
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} else {
|
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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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if (off0 > sizeof (struct ip)) {
|
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ip_stripoptions(m, (struct mbuf *)0);
|
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off0 = sizeof(struct ip);
|
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}
|
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if (m->m_len < sizeof (struct tcpiphdr)) {
|
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if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) {
|
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tcpstat.tcps_rcvshort++;
|
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return;
|
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}
|
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}
|
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ip = mtod(m, struct ip *);
|
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ipov = (struct ipovly *)ip;
|
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th = (struct tcphdr *)((caddr_t)ip + off0);
|
|
tlen = ip->ip_len;
|
|
|
|
if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
|
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if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
|
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th->th_sum = m->m_pkthdr.csum_data;
|
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else
|
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th->th_sum = in_pseudo(ip->ip_src.s_addr,
|
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ip->ip_dst.s_addr,
|
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htonl(m->m_pkthdr.csum_data +
|
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ip->ip_len +
|
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IPPROTO_TCP));
|
|
th->th_sum ^= 0xffff;
|
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#ifdef TCPDEBUG
|
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ipov->ih_len = (u_short)tlen;
|
|
ipov->ih_len = htons(ipov->ih_len);
|
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#endif
|
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} else {
|
|
/*
|
|
* Checksum extended TCP header and data.
|
|
*/
|
|
len = sizeof (struct ip) + tlen;
|
|
bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
|
|
ipov->ih_len = (u_short)tlen;
|
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ipov->ih_len = htons(ipov->ih_len);
|
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th->th_sum = in_cksum(m, len);
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|
}
|
|
if (th->th_sum) {
|
|
tcpstat.tcps_rcvbadsum++;
|
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goto drop;
|
|
}
|
|
#ifdef INET6
|
|
/* Re-initialization for later version check */
|
|
ip->ip_v = IPVERSION;
|
|
#endif
|
|
}
|
|
|
|
/*
|
|
* Check that TCP offset makes sense,
|
|
* pull out TCP options and adjust length. XXX
|
|
*/
|
|
off = th->th_off << 2;
|
|
if (off < sizeof (struct tcphdr) || off > tlen) {
|
|
tcpstat.tcps_rcvbadoff++;
|
|
goto drop;
|
|
}
|
|
tlen -= off; /* tlen is used instead of ti->ti_len */
|
|
if (off > sizeof (struct tcphdr)) {
|
|
if (isipv6) {
|
|
IP6_EXTHDR_CHECK(m, off0, off, );
|
|
ip6 = mtod(m, struct ip6_hdr *);
|
|
th = (struct tcphdr *)((caddr_t)ip6 + off0);
|
|
} else {
|
|
if (m->m_len < sizeof(struct ip) + off) {
|
|
if ((m = m_pullup(m, sizeof (struct ip) + off))
|
|
== 0) {
|
|
tcpstat.tcps_rcvshort++;
|
|
return;
|
|
}
|
|
ip = mtod(m, struct ip *);
|
|
ipov = (struct ipovly *)ip;
|
|
th = (struct tcphdr *)((caddr_t)ip + off0);
|
|
}
|
|
}
|
|
optlen = off - sizeof (struct tcphdr);
|
|
optp = (u_char *)(th + 1);
|
|
}
|
|
thflags = th->th_flags;
|
|
|
|
#ifdef TCP_DROP_SYNFIN
|
|
/*
|
|
* If the drop_synfin option is enabled, drop all packets with
|
|
* both the SYN and FIN bits set. This prevents e.g. nmap from
|
|
* identifying the TCP/IP stack.
|
|
*
|
|
* This is a violation of the TCP specification.
|
|
*/
|
|
if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN))
|
|
goto drop;
|
|
#endif
|
|
|
|
/*
|
|
* Convert TCP protocol specific fields to host format.
|
|
*/
|
|
th->th_seq = ntohl(th->th_seq);
|
|
th->th_ack = ntohl(th->th_ack);
|
|
th->th_win = ntohs(th->th_win);
|
|
th->th_urp = ntohs(th->th_urp);
|
|
|
|
/*
|
|
* Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options,
|
|
* until after ip6_savecontrol() is called and before other functions
|
|
* which don't want those proto headers.
|
|
* Because ip6_savecontrol() is going to parse the mbuf to
|
|
* search for data to be passed up to user-land, it wants mbuf
|
|
* parameters to be unchanged.
|
|
* XXX: the call of ip6_savecontrol() has been obsoleted based on
|
|
* latest version of the advanced API (20020110).
|
|
*/
|
|
drop_hdrlen = off0 + off;
|
|
|
|
/*
|
|
* Locate pcb for segment.
|
|
*/
|
|
INP_INFO_WLOCK(&tcbinfo);
|
|
headlocked = 1;
|
|
findpcb:
|
|
/* IPFIREWALL_FORWARD section */
|
|
if (next_hop != NULL && isipv6 == 0) { /* IPv6 support is not yet */
|
|
/*
|
|
* Transparently forwarded. Pretend to be the destination.
|
|
* already got one like this?
|
|
*/
|
|
inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport,
|
|
ip->ip_dst, th->th_dport,
|
|
0, m->m_pkthdr.rcvif);
|
|
if (!inp) {
|
|
/* It's new. Try find the ambushing socket. */
|
|
inp = in_pcblookup_hash(&tcbinfo,
|
|
ip->ip_src, th->th_sport,
|
|
next_hop->sin_addr,
|
|
next_hop->sin_port ?
|
|
ntohs(next_hop->sin_port) :
|
|
th->th_dport,
|
|
1, m->m_pkthdr.rcvif);
|
|
}
|
|
} else {
|
|
if (isipv6)
|
|
inp = in6_pcblookup_hash(&tcbinfo,
|
|
&ip6->ip6_src, th->th_sport,
|
|
&ip6->ip6_dst, th->th_dport,
|
|
1, m->m_pkthdr.rcvif);
|
|
else
|
|
inp = in_pcblookup_hash(&tcbinfo,
|
|
ip->ip_src, th->th_sport,
|
|
ip->ip_dst, th->th_dport,
|
|
1, m->m_pkthdr.rcvif);
|
|
}
|
|
|
|
#ifdef IPSEC
|
|
if (isipv6) {
|
|
if (inp != NULL && ipsec6_in_reject(m, inp)) {
|
|
ipsec6stat.in_polvio++;
|
|
goto drop;
|
|
}
|
|
} else {
|
|
if (inp != NULL && ipsec4_in_reject(m, inp)) {
|
|
ipsecstat.in_polvio++;
|
|
goto drop;
|
|
}
|
|
}
|
|
#endif
|
|
#ifdef FAST_IPSEC
|
|
if (isipv6) {
|
|
if (inp != NULL && ipsec6_in_reject(m, inp)) {
|
|
goto drop;
|
|
}
|
|
} else
|
|
if (inp != NULL && ipsec4_in_reject(m, inp)) {
|
|
goto drop;
|
|
}
|
|
#endif /*FAST_IPSEC*/
|
|
|
|
/*
|
|
* If the state is CLOSED (i.e., TCB does not exist) then
|
|
* all data in the incoming segment is discarded.
|
|
* If the TCB exists but is in CLOSED state, it is embryonic,
|
|
* but should either do a listen or a connect soon.
|
|
*/
|
|
if (inp == NULL) {
|
|
if (log_in_vain) {
|
|
#ifdef INET6
|
|
char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
|
|
#else
|
|
char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"];
|
|
#endif
|
|
|
|
if (isipv6) {
|
|
strcpy(dbuf, "[");
|
|
strcpy(sbuf, "[");
|
|
strcat(dbuf, ip6_sprintf(&ip6->ip6_dst));
|
|
strcat(sbuf, ip6_sprintf(&ip6->ip6_src));
|
|
strcat(dbuf, "]");
|
|
strcat(sbuf, "]");
|
|
} else {
|
|
strcpy(dbuf, inet_ntoa(ip->ip_dst));
|
|
strcpy(sbuf, inet_ntoa(ip->ip_src));
|
|
}
|
|
switch (log_in_vain) {
|
|
case 1:
|
|
if ((thflags & TH_SYN) == 0)
|
|
break;
|
|
/* FALLTHROUGH */
|
|
case 2:
|
|
log(LOG_INFO,
|
|
"Connection attempt to TCP %s:%d "
|
|
"from %s:%d flags:0x%02x\n",
|
|
dbuf, ntohs(th->th_dport), sbuf,
|
|
ntohs(th->th_sport), thflags);
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
if (blackhole) {
|
|
switch (blackhole) {
|
|
case 1:
|
|
if (thflags & TH_SYN)
|
|
goto drop;
|
|
break;
|
|
case 2:
|
|
goto drop;
|
|
default:
|
|
goto drop;
|
|
}
|
|
}
|
|
rstreason = BANDLIM_RST_CLOSEDPORT;
|
|
goto dropwithreset;
|
|
}
|
|
INP_LOCK(inp);
|
|
if (inp->inp_vflag & INP_TIMEWAIT) {
|
|
/*
|
|
* The only option of relevance is TOF_CC, and only if
|
|
* present in a SYN segment. See tcp_timewait().
|
|
*/
|
|
if (thflags & TH_SYN)
|
|
tcp_dooptions(&to, optp, optlen, 1);
|
|
if (tcp_timewait((struct tcptw *)inp->inp_ppcb,
|
|
&to, th, m, tlen))
|
|
goto findpcb;
|
|
/*
|
|
* tcp_timewait unlocks inp.
|
|
*/
|
|
INP_INFO_WUNLOCK(&tcbinfo);
|
|
return;
|
|
}
|
|
tp = intotcpcb(inp);
|
|
if (tp == 0) {
|
|
INP_UNLOCK(inp);
|
|
rstreason = BANDLIM_RST_CLOSEDPORT;
|
|
goto dropwithreset;
|
|
}
|
|
if (tp->t_state == TCPS_CLOSED)
|
|
goto drop;
|
|
|
|
/* Unscale the window into a 32-bit value. */
|
|
if ((thflags & TH_SYN) == 0)
|
|
tiwin = th->th_win << tp->snd_scale;
|
|
else
|
|
tiwin = th->th_win;
|
|
|
|
#ifdef MAC
|
|
if (mac_check_inpcb_deliver(inp, m))
|
|
goto drop;
|
|
#endif
|
|
so = inp->inp_socket;
|
|
#ifdef TCPDEBUG
|
|
if (so->so_options & SO_DEBUG) {
|
|
ostate = tp->t_state;
|
|
if (isipv6)
|
|
bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6));
|
|
else
|
|
bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
|
|
tcp_savetcp = *th;
|
|
}
|
|
#endif
|
|
if (so->so_options & SO_ACCEPTCONN) {
|
|
struct in_conninfo inc;
|
|
|
|
#ifdef INET6
|
|
inc.inc_isipv6 = isipv6;
|
|
#endif
|
|
if (isipv6) {
|
|
inc.inc6_faddr = ip6->ip6_src;
|
|
inc.inc6_laddr = ip6->ip6_dst;
|
|
} else {
|
|
inc.inc_faddr = ip->ip_src;
|
|
inc.inc_laddr = ip->ip_dst;
|
|
}
|
|
inc.inc_fport = th->th_sport;
|
|
inc.inc_lport = th->th_dport;
|
|
|
|
/*
|
|
* If the state is LISTEN then ignore segment if it contains
|
|
* a 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.
|
|
*
|
|
* If the state is SYN_RECEIVED (syncache) and seg contains
|
|
* an ACK, but not for our SYN/ACK, send a RST. If the seg
|
|
* contains a RST, check the sequence number to see if it
|
|
* is a valid reset segment.
|
|
*/
|
|
if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) {
|
|
if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) {
|
|
if (!syncache_expand(&inc, th, &so, m)) {
|
|
/*
|
|
* No syncache entry, or ACK was not
|
|
* for our SYN/ACK. Send a RST.
|
|
*/
|
|
tcpstat.tcps_badsyn++;
|
|
rstreason = BANDLIM_RST_OPENPORT;
|
|
goto dropwithreset;
|
|
}
|
|
if (so == NULL) {
|
|
/*
|
|
* Could not complete 3-way handshake,
|
|
* connection is being closed down, and
|
|
* syncache will free mbuf.
|
|
*/
|
|
INP_UNLOCK(inp);
|
|
INP_INFO_WUNLOCK(&tcbinfo);
|
|
return;
|
|
}
|
|
/*
|
|
* Socket is created in state SYN_RECEIVED.
|
|
* Continue processing segment.
|
|
*/
|
|
INP_UNLOCK(inp);
|
|
inp = sotoinpcb(so);
|
|
INP_LOCK(inp);
|
|
tp = intotcpcb(inp);
|
|
/*
|
|
* This is what would have happened in
|
|
* tcp_output() when the SYN,ACK was sent.
|
|
*/
|
|
tp->snd_up = tp->snd_una;
|
|
tp->snd_max = tp->snd_nxt = tp->iss + 1;
|
|
tp->last_ack_sent = tp->rcv_nxt;
|
|
/*
|
|
* RFC1323: The window in SYN & SYN/ACK
|
|
* segments is never scaled.
|
|
*/
|
|
tp->snd_wnd = tiwin; /* unscaled */
|
|
goto after_listen;
|
|
}
|
|
if (thflags & TH_RST) {
|
|
syncache_chkrst(&inc, th);
|
|
goto drop;
|
|
}
|
|
if (thflags & TH_ACK) {
|
|
syncache_badack(&inc);
|
|
tcpstat.tcps_badsyn++;
|
|
rstreason = BANDLIM_RST_OPENPORT;
|
|
goto dropwithreset;
|
|
}
|
|
goto drop;
|
|
}
|
|
|
|
/*
|
|
* Segment's flags are (SYN) or (SYN|FIN).
|
|
*/
|
|
#ifdef INET6
|
|
/*
|
|
* If deprecated address is forbidden,
|
|
* we do not accept SYN to deprecated interface
|
|
* address to prevent any new inbound connection from
|
|
* getting established.
|
|
* When we do not accept SYN, we send a TCP RST,
|
|
* with deprecated source address (instead of dropping
|
|
* it). We compromise it as it is much better for peer
|
|
* to send a RST, and RST will be the final packet
|
|
* for the exchange.
|
|
*
|
|
* If we do not forbid deprecated addresses, we accept
|
|
* the SYN packet. RFC2462 does not suggest dropping
|
|
* SYN in this case.
|
|
* If we decipher RFC2462 5.5.4, it says like this:
|
|
* 1. use of deprecated addr with existing
|
|
* communication is okay - "SHOULD continue to be
|
|
* used"
|
|
* 2. use of it with new communication:
|
|
* (2a) "SHOULD NOT be used if alternate address
|
|
* with sufficient scope is available"
|
|
* (2b) nothing mentioned otherwise.
|
|
* Here we fall into (2b) case as we have no choice in
|
|
* our source address selection - we must obey the peer.
|
|
*
|
|
* The wording in RFC2462 is confusing, and there are
|
|
* multiple description text for deprecated address
|
|
* handling - worse, they are not exactly the same.
|
|
* I believe 5.5.4 is the best one, so we follow 5.5.4.
|
|
*/
|
|
if (isipv6 && !ip6_use_deprecated) {
|
|
struct in6_ifaddr *ia6;
|
|
|
|
if ((ia6 = ip6_getdstifaddr(m)) &&
|
|
(ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
|
|
INP_UNLOCK(inp);
|
|
tp = NULL;
|
|
rstreason = BANDLIM_RST_OPENPORT;
|
|
goto dropwithreset;
|
|
}
|
|
}
|
|
#endif
|
|
/*
|
|
* If it is from this socket, drop it, it must be forged.
|
|
* Don't bother responding if the destination was a broadcast.
|
|
*/
|
|
if (th->th_dport == th->th_sport) {
|
|
if (isipv6) {
|
|
if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
|
|
&ip6->ip6_src))
|
|
goto drop;
|
|
} else {
|
|
if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
|
|
goto drop;
|
|
}
|
|
}
|
|
/*
|
|
* RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
|
|
*
|
|
* Note that it is quite possible to receive unicast
|
|
* link-layer packets with a broadcast IP address. Use
|
|
* in_broadcast() to find them.
|
|
*/
|
|
if (m->m_flags & (M_BCAST|M_MCAST))
|
|
goto drop;
|
|
if (isipv6) {
|
|
if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
|
|
IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
|
|
goto drop;
|
|
} else {
|
|
if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
|
|
IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
|
|
ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
|
|
in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
|
|
goto drop;
|
|
}
|
|
/*
|
|
* SYN appears to be valid; create compressed TCP state
|
|
* for syncache, or perform t/tcp connection.
|
|
*/
|
|
if (so->so_qlen <= so->so_qlimit) {
|
|
#ifdef TCPDEBUG
|
|
if (so->so_options & SO_DEBUG)
|
|
tcp_trace(TA_INPUT, ostate, tp,
|
|
(void *)tcp_saveipgen, &tcp_savetcp, 0);
|
|
#endif
|
|
tcp_dooptions(&to, optp, optlen, 1);
|
|
if (!syncache_add(&inc, &to, th, &so, m))
|
|
goto drop;
|
|
if (so == NULL) {
|
|
/*
|
|
* Entry added to syncache, mbuf used to
|
|
* send SYN,ACK packet.
|
|
*/
|
|
KASSERT(headlocked, ("headlocked"));
|
|
INP_UNLOCK(inp);
|
|
INP_INFO_WUNLOCK(&tcbinfo);
|
|
return;
|
|
}
|
|
/*
|
|
* Segment passed TAO tests.
|
|
*/
|
|
INP_UNLOCK(inp);
|
|
inp = sotoinpcb(so);
|
|
INP_LOCK(inp);
|
|
tp = intotcpcb(inp);
|
|
tp->snd_wnd = tiwin;
|
|
tp->t_starttime = ticks;
|
|
tp->t_state = TCPS_ESTABLISHED;
|
|
|
|
/*
|
|
* T/TCP logic:
|
|
* If there is a FIN or if there is data, then
|
|
* delay SYN,ACK(SYN) in the hope of piggy-backing
|
|
* it on a response segment. Otherwise must send
|
|
* ACK now in case the other side is slow starting.
|
|
*/
|
|
if (thflags & TH_FIN || tlen != 0)
|
|
tp->t_flags |= (TF_DELACK | TF_NEEDSYN);
|
|
else
|
|
tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
|
|
tcpstat.tcps_connects++;
|
|
soisconnected(so);
|
|
goto trimthenstep6;
|
|
}
|
|
goto drop;
|
|
}
|
|
after_listen:
|
|
|
|
/* XXX temp debugging */
|
|
/* should not happen - syncache should pick up these connections */
|
|
if (tp->t_state == TCPS_LISTEN)
|
|
panic("tcp_input: TCPS_LISTEN");
|
|
|
|
/*
|
|
* This is the second part of the MSS DoS prevention code (after
|
|
* minmss on the sending side) and it deals with too many too small
|
|
* tcp packets in a too short timeframe (1 second).
|
|
*
|
|
* For every full second we count the number of received packets
|
|
* and bytes. If we get a lot of packets per second for this connection
|
|
* (tcp_minmssoverload) we take a closer look at it and compute the
|
|
* average packet size for the past second. If that is less than
|
|
* tcp_minmss we get too many packets with very small payload which
|
|
* is not good and burdens our system (and every packet generates
|
|
* a wakeup to the process connected to our socket). We can reasonable
|
|
* expect this to be small packet DoS attack to exhaust our CPU
|
|
* cycles.
|
|
*
|
|
* Care has to be taken for the minimum packet overload value. This
|
|
* value defines the minimum number of packets per second before we
|
|
* start to worry. This must not be too low to avoid killing for
|
|
* example interactive connections with many small packets like
|
|
* telnet or SSH.
|
|
*
|
|
* Setting either tcp_minmssoverload or tcp_minmss to "0" disables
|
|
* this check.
|
|
*
|
|
* Account for packet if payload packet, skip over ACK, etc.
|
|
*/
|
|
if (tcp_minmss && tcp_minmssoverload &&
|
|
tp->t_state == TCPS_ESTABLISHED && tlen > 0) {
|
|
if (tp->rcv_second > ticks) {
|
|
tp->rcv_pps++;
|
|
tp->rcv_byps += tlen + off;
|
|
if (tp->rcv_pps > tcp_minmssoverload) {
|
|
if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) {
|
|
printf("too many small tcp packets from "
|
|
"%s:%u, av. %lubyte/packet, "
|
|
"dropping connection\n",
|
|
#ifdef INET6
|
|
isipv6 ?
|
|
ip6_sprintf(&inp->inp_inc.inc6_faddr) :
|
|
#endif
|
|
inet_ntoa(inp->inp_inc.inc_faddr),
|
|
inp->inp_inc.inc_fport,
|
|
tp->rcv_byps / tp->rcv_pps);
|
|
tp = tcp_drop(tp, ECONNRESET);
|
|
tcpstat.tcps_minmssdrops++;
|
|
goto drop;
|
|
}
|
|
}
|
|
} else {
|
|
tp->rcv_second = ticks + hz;
|
|
tp->rcv_pps = 1;
|
|
tp->rcv_byps = tlen + off;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Segment received on connection.
|
|
* Reset idle time and keep-alive timer.
|
|
*/
|
|
tp->t_rcvtime = ticks;
|
|
if (TCPS_HAVEESTABLISHED(tp->t_state))
|
|
callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp);
|
|
|
|
/*
|
|
* Process options only when we get SYN/ACK back. The SYN case
|
|
* for incoming connections is handled in tcp_syncache.
|
|
* XXX this is traditional behavior, may need to be cleaned up.
|
|
*/
|
|
tcp_dooptions(&to, optp, optlen, thflags & TH_SYN);
|
|
if (thflags & TH_SYN) {
|
|
if (to.to_flags & TOF_SCALE) {
|
|
tp->t_flags |= TF_RCVD_SCALE;
|
|
tp->requested_s_scale = to.to_requested_s_scale;
|
|
}
|
|
if (to.to_flags & TOF_TS) {
|
|
tp->t_flags |= TF_RCVD_TSTMP;
|
|
tp->ts_recent = to.to_tsval;
|
|
tp->ts_recent_age = ticks;
|
|
}
|
|
if (to.to_flags & (TOF_CC|TOF_CCNEW))
|
|
tp->t_flags |= TF_RCVD_CC;
|
|
if (to.to_flags & TOF_MSS)
|
|
tcp_mss(tp, to.to_mss);
|
|
}
|
|
|
|
/*
|
|
* 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.
|
|
* Make sure that the hidden state-flags are also off.
|
|
* Since we check for TCPS_ESTABLISHED above, it can only
|
|
* be TH_NEEDSYN.
|
|
*/
|
|
if (tp->t_state == TCPS_ESTABLISHED &&
|
|
(thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
|
|
((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
|
|
((to.to_flags & TOF_TS) == 0 ||
|
|
TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
|
|
/*
|
|
* Using the CC option is compulsory if once started:
|
|
* the segment is OK if no T/TCP was negotiated or
|
|
* if the segment has a CC option equal to CCrecv
|
|
*/
|
|
((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) ||
|
|
((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) &&
|
|
th->th_seq == tp->rcv_nxt &&
|
|
tiwin && tiwin == tp->snd_wnd &&
|
|
tp->snd_nxt == tp->snd_max) {
|
|
|
|
/*
|
|
* If last ACK falls within this segment's sequence numbers,
|
|
* record the timestamp.
|
|
* NOTE that the test is modified according to the latest
|
|
* proposal of the tcplw@cray.com list (Braden 1993/04/26).
|
|
*/
|
|
if ((to.to_flags & TOF_TS) != 0 &&
|
|
SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
|
|
tp->ts_recent_age = ticks;
|
|
tp->ts_recent = to.to_tsval;
|
|
}
|
|
|
|
if (tlen == 0) {
|
|
if (SEQ_GT(th->th_ack, tp->snd_una) &&
|
|
SEQ_LEQ(th->th_ack, tp->snd_max) &&
|
|
tp->snd_cwnd >= tp->snd_wnd &&
|
|
((!tcp_do_newreno &&
|
|
tp->t_dupacks < tcprexmtthresh) ||
|
|
(tcp_do_newreno && !IN_FASTRECOVERY(tp)))) {
|
|
KASSERT(headlocked, ("headlocked"));
|
|
INP_INFO_WUNLOCK(&tcbinfo);
|
|
/*
|
|
* this is a pure ack for outstanding data.
|
|
*/
|
|
++tcpstat.tcps_predack;
|
|
/*
|
|
* "bad retransmit" recovery
|
|
*/
|
|
if (tp->t_rxtshift == 1 &&
|
|
ticks < tp->t_badrxtwin) {
|
|
++tcpstat.tcps_sndrexmitbad;
|
|
tp->snd_cwnd = tp->snd_cwnd_prev;
|
|
tp->snd_ssthresh =
|
|
tp->snd_ssthresh_prev;
|
|
tp->snd_recover = tp->snd_recover_prev;
|
|
if (tp->t_flags & TF_WASFRECOVERY)
|
|
ENTER_FASTRECOVERY(tp);
|
|
tp->snd_nxt = tp->snd_max;
|
|
tp->t_badrxtwin = 0;
|
|
}
|
|
|
|
/*
|
|
* Recalculate the transmit timer / rtt.
|
|
*
|
|
* Some boxes send broken timestamp replies
|
|
* during the SYN+ACK phase, ignore
|
|
* timestamps of 0 or we could calculate a
|
|
* huge RTT and blow up the retransmit timer.
|
|
*/
|
|
if ((to.to_flags & TOF_TS) != 0 &&
|
|
to.to_tsecr) {
|
|
tcp_xmit_timer(tp,
|
|
ticks - to.to_tsecr + 1);
|
|
} else if (tp->t_rtttime &&
|
|
SEQ_GT(th->th_ack, tp->t_rtseq)) {
|
|
tcp_xmit_timer(tp,
|
|
ticks - tp->t_rtttime);
|
|
}
|
|
tcp_xmit_bandwidth_limit(tp, th->th_ack);
|
|
acked = th->th_ack - tp->snd_una;
|
|
tcpstat.tcps_rcvackpack++;
|
|
tcpstat.tcps_rcvackbyte += acked;
|
|
sbdrop(&so->so_snd, acked);
|
|
if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
|
|
SEQ_LEQ(th->th_ack, tp->snd_recover))
|
|
tp->snd_recover = th->th_ack - 1;
|
|
tp->snd_una = th->th_ack;
|
|
/*
|
|
* pull snd_wl2 up to prevent seq wrap relative
|
|
* to th_ack.
|
|
*/
|
|
tp->snd_wl2 = th->th_ack;
|
|
tp->t_dupacks = 0;
|
|
m_freem(m);
|
|
ND6_HINT(tp); /* some progress has been done */
|
|
|
|
/*
|
|
* 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.
|
|
|
|
#ifdef TCPDEBUG
|
|
if (so->so_options & SO_DEBUG)
|
|
tcp_trace(TA_INPUT, ostate, tp,
|
|
(void *)tcp_saveipgen,
|
|
&tcp_savetcp, 0);
|
|
#endif
|
|
*/
|
|
if (tp->snd_una == tp->snd_max)
|
|
callout_stop(tp->tt_rexmt);
|
|
else if (!callout_active(tp->tt_persist))
|
|
callout_reset(tp->tt_rexmt,
|
|
tp->t_rxtcur,
|
|
tcp_timer_rexmt, tp);
|
|
|
|
sowwakeup(so);
|
|
if (so->so_snd.sb_cc)
|
|
(void) tcp_output(tp);
|
|
goto check_delack;
|
|
}
|
|
} else if (th->th_ack == tp->snd_una &&
|
|
LIST_EMPTY(&tp->t_segq) &&
|
|
tlen <= sbspace(&so->so_rcv)) {
|
|
KASSERT(headlocked, ("headlocked"));
|
|
INP_INFO_WUNLOCK(&tcbinfo);
|
|
/*
|
|
* this is a pure, in-sequence data packet
|
|
* with nothing on the reassembly queue and
|
|
* we have enough buffer space to take it.
|
|
*/
|
|
++tcpstat.tcps_preddat;
|
|
tp->rcv_nxt += tlen;
|
|
/*
|
|
* Pull snd_wl1 up to prevent seq wrap relative to
|
|
* th_seq.
|
|
*/
|
|
tp->snd_wl1 = th->th_seq;
|
|
/*
|
|
* Pull rcv_up up to prevent seq wrap relative to
|
|
* rcv_nxt.
|
|
*/
|
|
tp->rcv_up = tp->rcv_nxt;
|
|
tcpstat.tcps_rcvpack++;
|
|
tcpstat.tcps_rcvbyte += tlen;
|
|
ND6_HINT(tp); /* some progress has been done */
|
|
/*
|
|
#ifdef TCPDEBUG
|
|
if (so->so_options & SO_DEBUG)
|
|
tcp_trace(TA_INPUT, ostate, tp,
|
|
(void *)tcp_saveipgen, &tcp_savetcp, 0);
|
|
#endif
|
|
* Add data to socket buffer.
|
|
*/
|
|
if (so->so_state & SS_CANTRCVMORE) {
|
|
m_freem(m);
|
|
} else {
|
|
m_adj(m, drop_hdrlen); /* delayed header drop */
|
|
sbappendstream(&so->so_rcv, m);
|
|
}
|
|
sorwakeup(so);
|
|
if (DELAY_ACK(tp)) {
|
|
tp->t_flags |= TF_DELACK;
|
|
} else {
|
|
tp->t_flags |= TF_ACKNOW;
|
|
tcp_output(tp);
|
|
}
|
|
goto check_delack;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* 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 = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
|
|
}
|
|
|
|
switch (tp->t_state) {
|
|
|
|
/*
|
|
* If the state is SYN_RECEIVED:
|
|
* if seg contains an ACK, but not for our SYN/ACK, send a RST.
|
|
*/
|
|
case TCPS_SYN_RECEIVED:
|
|
if ((thflags & TH_ACK) &&
|
|
(SEQ_LEQ(th->th_ack, tp->snd_una) ||
|
|
SEQ_GT(th->th_ack, tp->snd_max))) {
|
|
rstreason = BANDLIM_RST_OPENPORT;
|
|
goto dropwithreset;
|
|
}
|
|
break;
|
|
|
|
/*
|
|
* 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 (tcp_do_rfc1644)
|
|
tcp_hc_gettao(&inp->inp_inc, &tao);
|
|
|
|
if ((thflags & TH_ACK) &&
|
|
(SEQ_LEQ(th->th_ack, tp->iss) ||
|
|
SEQ_GT(th->th_ack, tp->snd_max))) {
|
|
/*
|
|
* If we have a cached CCsent for the remote host,
|
|
* hence we haven't just crashed and restarted,
|
|
* do not send a RST. This may be a retransmission
|
|
* from the other side after our earlier ACK was lost.
|
|
* Our new SYN, when it arrives, will serve as the
|
|
* needed ACK.
|
|
*/
|
|
if (tao.tao_ccsent != 0)
|
|
goto drop;
|
|
else {
|
|
rstreason = BANDLIM_UNLIMITED;
|
|
goto dropwithreset;
|
|
}
|
|
}
|
|
if (thflags & TH_RST) {
|
|
if (thflags & TH_ACK)
|
|
tp = tcp_drop(tp, ECONNREFUSED);
|
|
goto drop;
|
|
}
|
|
if ((thflags & TH_SYN) == 0)
|
|
goto drop;
|
|
tp->snd_wnd = th->th_win; /* initial send window */
|
|
tp->cc_recv = to.to_cc; /* foreign CC */
|
|
|
|
tp->irs = th->th_seq;
|
|
tcp_rcvseqinit(tp);
|
|
if (thflags & TH_ACK) {
|
|
/*
|
|
* Our SYN was acked. If segment contains CC.ECHO
|
|
* option, check it to make sure this segment really
|
|
* matches our SYN. If not, just drop it as old
|
|
* duplicate, but send an RST if we're still playing
|
|
* by the old rules. If no CC.ECHO option, make sure
|
|
* we don't get fooled into using T/TCP.
|
|
*/
|
|
if (to.to_flags & TOF_CCECHO) {
|
|
if (tp->cc_send != to.to_ccecho) {
|
|
if (tao.tao_ccsent != 0)
|
|
goto drop;
|
|
else {
|
|
rstreason = BANDLIM_UNLIMITED;
|
|
goto dropwithreset;
|
|
}
|
|
}
|
|
} else
|
|
tp->t_flags &= ~TF_RCVD_CC;
|
|
tcpstat.tcps_connects++;
|
|
soisconnected(so);
|
|
#ifdef MAC
|
|
mac_set_socket_peer_from_mbuf(m, so);
|
|
#endif
|
|
/* Do window scaling on this connection? */
|
|
if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
|
|
(TF_RCVD_SCALE|TF_REQ_SCALE)) {
|
|
tp->snd_scale = tp->requested_s_scale;
|
|
tp->rcv_scale = tp->request_r_scale;
|
|
}
|
|
/* Segment is acceptable, update cache if undefined. */
|
|
if (tao.tao_ccsent == 0 && tcp_do_rfc1644)
|
|
tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CCSENT, to.to_ccecho, 0);
|
|
|
|
tp->rcv_adv += tp->rcv_wnd;
|
|
tp->snd_una++; /* SYN is acked */
|
|
/*
|
|
* If there's data, delay ACK; if there's also a FIN
|
|
* ACKNOW will be turned on later.
|
|
*/
|
|
if (DELAY_ACK(tp) && tlen != 0)
|
|
callout_reset(tp->tt_delack, tcp_delacktime,
|
|
tcp_timer_delack, tp);
|
|
else
|
|
tp->t_flags |= TF_ACKNOW;
|
|
/*
|
|
* Received <SYN,ACK> in SYN_SENT[*] state.
|
|
* Transitions:
|
|
* SYN_SENT --> ESTABLISHED
|
|
* SYN_SENT* --> FIN_WAIT_1
|
|
*/
|
|
tp->t_starttime = ticks;
|
|
if (tp->t_flags & TF_NEEDFIN) {
|
|
tp->t_state = TCPS_FIN_WAIT_1;
|
|
tp->t_flags &= ~TF_NEEDFIN;
|
|
thflags &= ~TH_SYN;
|
|
} else {
|
|
tp->t_state = TCPS_ESTABLISHED;
|
|
callout_reset(tp->tt_keep, tcp_keepidle,
|
|
tcp_timer_keep, tp);
|
|
}
|
|
} else {
|
|
/*
|
|
* Received initial SYN in SYN-SENT[*] state =>
|
|
* simultaneous open. If segment contains CC option
|
|
* and there is a cached CC, apply TAO test.
|
|
* If it succeeds, connection is * half-synchronized.
|
|
* Otherwise, do 3-way handshake:
|
|
* SYN-SENT -> SYN-RECEIVED
|
|
* SYN-SENT* -> SYN-RECEIVED*
|
|
* If there was no CC option, clear cached CC value.
|
|
*/
|
|
tp->t_flags |= TF_ACKNOW;
|
|
callout_stop(tp->tt_rexmt);
|
|
if (to.to_flags & TOF_CC) {
|
|
if (tao.tao_cc != 0 &&
|
|
CC_GT(to.to_cc, tao.tao_cc)) {
|
|
/*
|
|
* update cache and make transition:
|
|
* SYN-SENT -> ESTABLISHED*
|
|
* SYN-SENT* -> FIN-WAIT-1*
|
|
*/
|
|
tao.tao_cc = to.to_cc;
|
|
tcp_hc_updatetao(&inp->inp_inc,
|
|
TCP_HC_TAO_CC, to.to_cc, 0);
|
|
tp->t_starttime = ticks;
|
|
if (tp->t_flags & TF_NEEDFIN) {
|
|
tp->t_state = TCPS_FIN_WAIT_1;
|
|
tp->t_flags &= ~TF_NEEDFIN;
|
|
} else {
|
|
tp->t_state = TCPS_ESTABLISHED;
|
|
callout_reset(tp->tt_keep,
|
|
tcp_keepidle,
|
|
tcp_timer_keep,
|
|
tp);
|
|
}
|
|
tp->t_flags |= TF_NEEDSYN;
|
|
} else
|
|
tp->t_state = TCPS_SYN_RECEIVED;
|
|
} else {
|
|
if (tcp_do_rfc1644) {
|
|
/* CC.NEW or no option => invalidate cache */
|
|
tao.tao_cc = 0;
|
|
tcp_hc_updatetao(&inp->inp_inc,
|
|
TCP_HC_TAO_CC, to.to_cc, 0);
|
|
}
|
|
tp->t_state = TCPS_SYN_RECEIVED;
|
|
}
|
|
}
|
|
|
|
trimthenstep6:
|
|
/*
|
|
* Advance th->th_seq to correspond to first data byte.
|
|
* If data, trim to stay within window,
|
|
* dropping FIN if necessary.
|
|
*/
|
|
th->th_seq++;
|
|
if (tlen > tp->rcv_wnd) {
|
|
todrop = tlen - tp->rcv_wnd;
|
|
m_adj(m, -todrop);
|
|
tlen = tp->rcv_wnd;
|
|
thflags &= ~TH_FIN;
|
|
tcpstat.tcps_rcvpackafterwin++;
|
|
tcpstat.tcps_rcvbyteafterwin += todrop;
|
|
}
|
|
tp->snd_wl1 = th->th_seq - 1;
|
|
tp->rcv_up = th->th_seq;
|
|
/*
|
|
* Client side of transaction: already sent SYN and data.
|
|
* If the remote host used T/TCP to validate the SYN,
|
|
* our data will be ACK'd; if so, enter normal data segment
|
|
* processing in the middle of step 5, ack processing.
|
|
* Otherwise, goto step 6.
|
|
*/
|
|
if (thflags & TH_ACK)
|
|
goto process_ACK;
|
|
|
|
goto step6;
|
|
|
|
/*
|
|
* If the state is LAST_ACK or CLOSING or TIME_WAIT:
|
|
* if segment contains a SYN and CC [not CC.NEW] option:
|
|
* if state == TIME_WAIT and connection duration > MSL,
|
|
* drop packet and send RST;
|
|
*
|
|
* if SEG.CC > CCrecv then is new SYN, and can implicitly
|
|
* ack the FIN (and data) in retransmission queue.
|
|
* Complete close and delete TCPCB. Then reprocess
|
|
* segment, hoping to find new TCPCB in LISTEN state;
|
|
*
|
|
* else must be old SYN; drop it.
|
|
* else do normal processing.
|
|
*/
|
|
case TCPS_LAST_ACK:
|
|
case TCPS_CLOSING:
|
|
case TCPS_TIME_WAIT:
|
|
KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
|
|
if ((thflags & TH_SYN) &&
|
|
(to.to_flags & TOF_CC) && tp->cc_recv != 0) {
|
|
if (tp->t_state == TCPS_TIME_WAIT &&
|
|
(ticks - tp->t_starttime) > tcp_msl) {
|
|
rstreason = BANDLIM_UNLIMITED;
|
|
goto dropwithreset;
|
|
}
|
|
if (CC_GT(to.to_cc, tp->cc_recv)) {
|
|
tp = tcp_close(tp);
|
|
goto findpcb;
|
|
}
|
|
else
|
|
goto drop;
|
|
}
|
|
break; /* continue normal processing */
|
|
}
|
|
|
|
/*
|
|
* States other than LISTEN or SYN_SENT.
|
|
* First check the RST flag and sequence number since reset segments
|
|
* are exempt from the timestamp and connection count tests. This
|
|
* fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
|
|
* below which allowed reset segments in half the sequence space
|
|
* to fall though and be processed (which gives forged reset
|
|
* segments with a random sequence number a 50 percent chance of
|
|
* killing a connection).
|
|
* Then check timestamp, if present.
|
|
* Then check the connection count, if present.
|
|
* Then 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.
|
|
*
|
|
*
|
|
* If the RST bit is set, check the sequence number to see
|
|
* if this is a valid reset segment.
|
|
* RFC 793 page 37:
|
|
* In all states except SYN-SENT, all reset (RST) segments
|
|
* are validated by checking their SEQ-fields. A reset is
|
|
* valid if its sequence number is in the window.
|
|
* Note: this does not take into account delayed ACKs, so
|
|
* we should test against last_ack_sent instead of rcv_nxt.
|
|
* The sequence number in the reset segment is normally an
|
|
* echo of our outgoing acknowlegement numbers, but some hosts
|
|
* send a reset with the sequence number at the rightmost edge
|
|
* of our receive window, and we have to handle this case.
|
|
* If we have multiple segments in flight, the intial reset
|
|
* segment sequence numbers will be to the left of last_ack_sent,
|
|
* but they will eventually catch up.
|
|
* In any case, it never made sense to trim reset segments to
|
|
* fit the receive window since RFC 1122 says:
|
|
* 4.2.2.12 RST Segment: RFC-793 Section 3.4
|
|
*
|
|
* A TCP SHOULD allow a received RST segment to include data.
|
|
*
|
|
* DISCUSSION
|
|
* It has been suggested that a RST segment could contain
|
|
* ASCII text that encoded and explained the cause of the
|
|
* RST. No standard has yet been established for such
|
|
* data.
|
|
*
|
|
* If the reset segment passes the sequence number test 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_WAIT_2, CLOSE_WAIT STATES:
|
|
* Inform user that connection was reset, and close tcb.
|
|
* CLOSING, LAST_ACK STATES:
|
|
* Close the tcb.
|
|
* TIME_WAIT STATE:
|
|
* Drop the segment - see Stevens, vol. 2, p. 964 and
|
|
* RFC 1337.
|
|
*/
|
|
if (thflags & TH_RST) {
|
|
if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
|
|
SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
|
|
switch (tp->t_state) {
|
|
|
|
case TCPS_SYN_RECEIVED:
|
|
so->so_error = ECONNREFUSED;
|
|
goto close;
|
|
|
|
case TCPS_ESTABLISHED:
|
|
case TCPS_FIN_WAIT_1:
|
|
case TCPS_FIN_WAIT_2:
|
|
case TCPS_CLOSE_WAIT:
|
|
so->so_error = ECONNRESET;
|
|
close:
|
|
tp->t_state = TCPS_CLOSED;
|
|
tcpstat.tcps_drops++;
|
|
tp = tcp_close(tp);
|
|
break;
|
|
|
|
case TCPS_CLOSING:
|
|
case TCPS_LAST_ACK:
|
|
tp = tcp_close(tp);
|
|
break;
|
|
|
|
case TCPS_TIME_WAIT:
|
|
KASSERT(tp->t_state != TCPS_TIME_WAIT,
|
|
("timewait"));
|
|
break;
|
|
}
|
|
}
|
|
goto drop;
|
|
}
|
|
|
|
/*
|
|
* RFC 1323 PAWS: If we have a timestamp reply on this segment
|
|
* and it's less than ts_recent, drop it.
|
|
*/
|
|
if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
|
|
TSTMP_LT(to.to_tsval, tp->ts_recent)) {
|
|
|
|
/* Check to see if ts_recent is over 24 days old. */
|
|
if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
|
|
/*
|
|
* Invalidate ts_recent. If this segment updates
|
|
* ts_recent, the age will be reset later and ts_recent
|
|
* will get a valid value. If it does not, setting
|
|
* ts_recent to zero will at least satisfy the
|
|
* requirement that zero be placed in the timestamp
|
|
* echo reply when ts_recent isn't valid. The
|
|
* age isn't reset until we get a valid ts_recent
|
|
* because we don't want out-of-order segments to be
|
|
* dropped when ts_recent is old.
|
|
*/
|
|
tp->ts_recent = 0;
|
|
} else {
|
|
tcpstat.tcps_rcvduppack++;
|
|
tcpstat.tcps_rcvdupbyte += tlen;
|
|
tcpstat.tcps_pawsdrop++;
|
|
if (tlen)
|
|
goto dropafterack;
|
|
goto drop;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* T/TCP mechanism
|
|
* If T/TCP was negotiated and the segment doesn't have CC,
|
|
* or if its CC is wrong then drop the segment.
|
|
* RST segments do not have to comply with this.
|
|
*/
|
|
if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) &&
|
|
((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc))
|
|
goto dropafterack;
|
|
|
|
/*
|
|
* In the SYN-RECEIVED state, validate that the packet belongs to
|
|
* this connection before trimming the data to fit the receive
|
|
* window. Check the sequence number versus IRS since we know
|
|
* the sequence numbers haven't wrapped. This is a partial fix
|
|
* for the "LAND" DoS attack.
|
|
*/
|
|
if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
|
|
rstreason = BANDLIM_RST_OPENPORT;
|
|
goto dropwithreset;
|
|
}
|
|
|
|
todrop = tp->rcv_nxt - th->th_seq;
|
|
if (todrop > 0) {
|
|
if (thflags & TH_SYN) {
|
|
thflags &= ~TH_SYN;
|
|
th->th_seq++;
|
|
if (th->th_urp > 1)
|
|
th->th_urp--;
|
|
else
|
|
thflags &= ~TH_URG;
|
|
todrop--;
|
|
}
|
|
/*
|
|
* Following if statement from Stevens, vol. 2, p. 960.
|
|
*/
|
|
if (todrop > tlen
|
|
|| (todrop == tlen && (thflags & 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.
|
|
*/
|
|
thflags &= ~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 = tlen;
|
|
tcpstat.tcps_rcvduppack++;
|
|
tcpstat.tcps_rcvdupbyte += todrop;
|
|
} else {
|
|
tcpstat.tcps_rcvpartduppack++;
|
|
tcpstat.tcps_rcvpartdupbyte += todrop;
|
|
}
|
|
drop_hdrlen += todrop; /* drop from the top afterwards */
|
|
th->th_seq += todrop;
|
|
tlen -= todrop;
|
|
if (th->th_urp > todrop)
|
|
th->th_urp -= todrop;
|
|
else {
|
|
thflags &= ~TH_URG;
|
|
th->th_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 && tlen) {
|
|
tp = tcp_close(tp);
|
|
tcpstat.tcps_rcvafterclose++;
|
|
rstreason = BANDLIM_UNLIMITED;
|
|
goto dropwithreset;
|
|
}
|
|
|
|
/*
|
|
* If segment ends after window, drop trailing data
|
|
* (and PUSH and FIN); if nothing left, just ACK.
|
|
*/
|
|
todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd);
|
|
if (todrop > 0) {
|
|
tcpstat.tcps_rcvpackafterwin++;
|
|
if (todrop >= tlen) {
|
|
tcpstat.tcps_rcvbyteafterwin += tlen;
|
|
/*
|
|
* 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.
|
|
*/
|
|
KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
|
|
if (thflags & TH_SYN &&
|
|
tp->t_state == TCPS_TIME_WAIT &&
|
|
SEQ_GT(th->th_seq, tp->rcv_nxt)) {
|
|
tp = tcp_close(tp);
|
|
goto findpcb;
|
|
}
|
|
/*
|
|
* 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 && th->th_seq == tp->rcv_nxt) {
|
|
tp->t_flags |= TF_ACKNOW;
|
|
tcpstat.tcps_rcvwinprobe++;
|
|
} else
|
|
goto dropafterack;
|
|
} else
|
|
tcpstat.tcps_rcvbyteafterwin += todrop;
|
|
m_adj(m, -todrop);
|
|
tlen -= todrop;
|
|
thflags &= ~(TH_PUSH|TH_FIN);
|
|
}
|
|
|
|
/*
|
|
* If last ACK falls within this segment's sequence numbers,
|
|
* record its timestamp.
|
|
* NOTE that the test is modified according to the latest
|
|
* proposal of the tcplw@cray.com list (Braden 1993/04/26).
|
|
*/
|
|
if ((to.to_flags & TOF_TS) != 0 &&
|
|
SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
|
|
tp->ts_recent_age = ticks;
|
|
tp->ts_recent = to.to_tsval;
|
|
}
|
|
|
|
/*
|
|
* If a SYN is in the window, then this is an
|
|
* error and we send an RST and drop the connection.
|
|
*/
|
|
if (thflags & TH_SYN) {
|
|
tp = tcp_drop(tp, ECONNRESET);
|
|
rstreason = BANDLIM_UNLIMITED;
|
|
goto drop;
|
|
}
|
|
|
|
/*
|
|
* If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
|
|
* flag is on (half-synchronized state), then queue data for
|
|
* later processing; else drop segment and return.
|
|
*/
|
|
if ((thflags & TH_ACK) == 0) {
|
|
if (tp->t_state == TCPS_SYN_RECEIVED ||
|
|
(tp->t_flags & TF_NEEDSYN))
|
|
goto step6;
|
|
else
|
|
goto drop;
|
|
}
|
|
|
|
/*
|
|
* Ack processing.
|
|
*/
|
|
switch (tp->t_state) {
|
|
|
|
/*
|
|
* In SYN_RECEIVED state, the ack ACKs our SYN, so enter
|
|
* ESTABLISHED state and continue processing.
|
|
* The ACK was checked above.
|
|
*/
|
|
case TCPS_SYN_RECEIVED:
|
|
|
|
tcpstat.tcps_connects++;
|
|
soisconnected(so);
|
|
/* Do window scaling? */
|
|
if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
|
|
(TF_RCVD_SCALE|TF_REQ_SCALE)) {
|
|
tp->snd_scale = tp->requested_s_scale;
|
|
tp->rcv_scale = tp->request_r_scale;
|
|
}
|
|
/*
|
|
* Upon successful completion of 3-way handshake,
|
|
* update cache.CC, pass any queued data to the user,
|
|
* and advance state appropriately.
|
|
*/
|
|
if (tcp_do_rfc1644) {
|
|
tao.tao_cc = tp->cc_recv;
|
|
tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CC,
|
|
tp->cc_recv, 0);
|
|
}
|
|
/*
|
|
* Make transitions:
|
|
* SYN-RECEIVED -> ESTABLISHED
|
|
* SYN-RECEIVED* -> FIN-WAIT-1
|
|
*/
|
|
tp->t_starttime = ticks;
|
|
if (tp->t_flags & TF_NEEDFIN) {
|
|
tp->t_state = TCPS_FIN_WAIT_1;
|
|
tp->t_flags &= ~TF_NEEDFIN;
|
|
} else {
|
|
tp->t_state = TCPS_ESTABLISHED;
|
|
callout_reset(tp->tt_keep, tcp_keepidle,
|
|
tcp_timer_keep, tp);
|
|
}
|
|
/*
|
|
* If segment contains data or ACK, will call tcp_reass()
|
|
* later; if not, do so now to pass queued data to user.
|
|
*/
|
|
if (tlen == 0 && (thflags & TH_FIN) == 0)
|
|
(void) tcp_reass(tp, (struct tcphdr *)0, 0,
|
|
(struct mbuf *)0);
|
|
tp->snd_wl1 = th->th_seq - 1;
|
|
/* FALLTHROUGH */
|
|
|
|
/*
|
|
* In ESTABLISHED state: drop duplicate ACKs; ACK out of range
|
|
* ACKs. If the ack is in the range
|
|
* tp->snd_una < th->th_ack <= tp->snd_max
|
|
* then advance tp->snd_una to th->th_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:
|
|
KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
|
|
if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
|
|
if (tlen == 0 && tiwin == tp->snd_wnd) {
|
|
tcpstat.tcps_rcvdupack++;
|
|
/*
|
|
* 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
|
|
* threshhold 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 (!callout_active(tp->tt_rexmt) ||
|
|
th->th_ack != tp->snd_una)
|
|
tp->t_dupacks = 0;
|
|
else if (++tp->t_dupacks > tcprexmtthresh ||
|
|
(tcp_do_newreno &&
|
|
IN_FASTRECOVERY(tp))) {
|
|
tp->snd_cwnd += tp->t_maxseg;
|
|
(void) tcp_output(tp);
|
|
goto drop;
|
|
} else if (tp->t_dupacks == tcprexmtthresh) {
|
|
tcp_seq onxt = tp->snd_nxt;
|
|
u_int win;
|
|
if (tcp_do_newreno &&
|
|
SEQ_LEQ(th->th_ack,
|
|
tp->snd_recover)) {
|
|
tp->t_dupacks = 0;
|
|
break;
|
|
}
|
|
win = min(tp->snd_wnd, tp->snd_cwnd) /
|
|
2 / tp->t_maxseg;
|
|
if (win < 2)
|
|
win = 2;
|
|
tp->snd_ssthresh = win * tp->t_maxseg;
|
|
ENTER_FASTRECOVERY(tp);
|
|
tp->snd_recover = tp->snd_max;
|
|
callout_stop(tp->tt_rexmt);
|
|
tp->t_rtttime = 0;
|
|
tp->snd_nxt = th->th_ack;
|
|
tp->snd_cwnd = tp->t_maxseg;
|
|
(void) tcp_output(tp);
|
|
KASSERT(tp->snd_limited <= 2,
|
|
("tp->snd_limited too big"));
|
|
tp->snd_cwnd = tp->snd_ssthresh +
|
|
tp->t_maxseg *
|
|
(tp->t_dupacks - tp->snd_limited);
|
|
if (SEQ_GT(onxt, tp->snd_nxt))
|
|
tp->snd_nxt = onxt;
|
|
goto drop;
|
|
} else if (tcp_do_rfc3042) {
|
|
u_long oldcwnd = tp->snd_cwnd;
|
|
tcp_seq oldsndmax = tp->snd_max;
|
|
u_int sent;
|
|
KASSERT(tp->t_dupacks == 1 ||
|
|
tp->t_dupacks == 2,
|
|
("dupacks not 1 or 2"));
|
|
if (tp->t_dupacks == 1)
|
|
tp->snd_limited = 0;
|
|
tp->snd_cwnd =
|
|
(tp->snd_nxt - tp->snd_una) +
|
|
(tp->t_dupacks - tp->snd_limited) *
|
|
tp->t_maxseg;
|
|
(void) tcp_output(tp);
|
|
sent = tp->snd_max - oldsndmax;
|
|
if (sent > tp->t_maxseg) {
|
|
KASSERT(tp->snd_limited == 0 &&
|
|
tp->t_dupacks == 2,
|
|
("sent too much"));
|
|
tp->snd_limited = 2;
|
|
} else if (sent > 0)
|
|
++tp->snd_limited;
|
|
tp->snd_cwnd = oldcwnd;
|
|
goto drop;
|
|
}
|
|
} else
|
|
tp->t_dupacks = 0;
|
|
break;
|
|
}
|
|
|
|
KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una"));
|
|
|
|
/*
|
|
* If the congestion window was inflated to account
|
|
* for the other side's cached packets, retract it.
|
|
*/
|
|
if (tcp_do_newreno) {
|
|
if (IN_FASTRECOVERY(tp)) {
|
|
if (SEQ_LT(th->th_ack, tp->snd_recover)) {
|
|
tcp_newreno_partial_ack(tp, th);
|
|
} else {
|
|
/*
|
|
* Window inflation should have left us
|
|
* with approximately snd_ssthresh
|
|
* outstanding data.
|
|
* But in case we would be inclined to
|
|
* send a burst, better to do it via
|
|
* the slow start mechanism.
|
|
*/
|
|
if (SEQ_GT(th->th_ack +
|
|
tp->snd_ssthresh,
|
|
tp->snd_max))
|
|
tp->snd_cwnd = tp->snd_max -
|
|
th->th_ack +
|
|
tp->t_maxseg;
|
|
else
|
|
tp->snd_cwnd = tp->snd_ssthresh;
|
|
}
|
|
}
|
|
} else {
|
|
if (tp->t_dupacks >= tcprexmtthresh &&
|
|
tp->snd_cwnd > tp->snd_ssthresh)
|
|
tp->snd_cwnd = tp->snd_ssthresh;
|
|
}
|
|
tp->t_dupacks = 0;
|
|
if (SEQ_GT(th->th_ack, tp->snd_max)) {
|
|
tcpstat.tcps_rcvacktoomuch++;
|
|
goto dropafterack;
|
|
}
|
|
/*
|
|
* If we reach this point, ACK is not a duplicate,
|
|
* i.e., it ACKs something we sent.
|
|
*/
|
|
if (tp->t_flags & TF_NEEDSYN) {
|
|
/*
|
|
* T/TCP: Connection was half-synchronized, and our
|
|
* SYN has been ACK'd (so connection is now fully
|
|
* synchronized). Go to non-starred state,
|
|
* increment snd_una for ACK of SYN, and check if
|
|
* we can do window scaling.
|
|
*/
|
|
tp->t_flags &= ~TF_NEEDSYN;
|
|
tp->snd_una++;
|
|
/* Do window scaling? */
|
|
if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
|
|
(TF_RCVD_SCALE|TF_REQ_SCALE)) {
|
|
tp->snd_scale = tp->requested_s_scale;
|
|
tp->rcv_scale = tp->request_r_scale;
|
|
}
|
|
}
|
|
|
|
process_ACK:
|
|
acked = th->th_ack - tp->snd_una;
|
|
tcpstat.tcps_rcvackpack++;
|
|
tcpstat.tcps_rcvackbyte += acked;
|
|
|
|
/*
|
|
* If we just performed our first retransmit, and the ACK
|
|
* arrives within our recovery window, then it was a mistake
|
|
* to do the retransmit in the first place. Recover our
|
|
* original cwnd and ssthresh, and proceed to transmit where
|
|
* we left off.
|
|
*/
|
|
if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
|
|
++tcpstat.tcps_sndrexmitbad;
|
|
tp->snd_cwnd = tp->snd_cwnd_prev;
|
|
tp->snd_ssthresh = tp->snd_ssthresh_prev;
|
|
tp->snd_recover = tp->snd_recover_prev;
|
|
if (tp->t_flags & TF_WASFRECOVERY)
|
|
ENTER_FASTRECOVERY(tp);
|
|
tp->snd_nxt = tp->snd_max;
|
|
tp->t_badrxtwin = 0; /* XXX probably not required */
|
|
}
|
|
|
|
/*
|
|
* If we have a timestamp reply, update smoothed
|
|
* round trip time. If no timestamp is present but
|
|
* 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.
|
|
*
|
|
* Some boxes send broken timestamp replies
|
|
* during the SYN+ACK phase, ignore
|
|
* timestamps of 0 or we could calculate a
|
|
* huge RTT and blow up the retransmit timer.
|
|
*/
|
|
if ((to.to_flags & TOF_TS) != 0 &&
|
|
to.to_tsecr) {
|
|
tcp_xmit_timer(tp, ticks - to.to_tsecr + 1);
|
|
} else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
|
|
tcp_xmit_timer(tp, ticks - tp->t_rtttime);
|
|
}
|
|
tcp_xmit_bandwidth_limit(tp, th->th_ack);
|
|
|
|
/*
|
|
* 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 (th->th_ack == tp->snd_max) {
|
|
callout_stop(tp->tt_rexmt);
|
|
needoutput = 1;
|
|
} else if (!callout_active(tp->tt_persist))
|
|
callout_reset(tp->tt_rexmt, tp->t_rxtcur,
|
|
tcp_timer_rexmt, tp);
|
|
|
|
/*
|
|
* If no data (only SYN) was ACK'd,
|
|
* skip rest of ACK processing.
|
|
*/
|
|
if (acked == 0)
|
|
goto step6;
|
|
|
|
/*
|
|
* 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).
|
|
*/
|
|
if (!tcp_do_newreno || !IN_FASTRECOVERY(tp)) {
|
|
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;
|
|
}
|
|
sowwakeup(so);
|
|
/* detect una wraparound */
|
|
if (tcp_do_newreno && !IN_FASTRECOVERY(tp) &&
|
|
SEQ_GT(tp->snd_una, tp->snd_recover) &&
|
|
SEQ_LEQ(th->th_ack, tp->snd_recover))
|
|
tp->snd_recover = th->th_ack - 1;
|
|
if (tcp_do_newreno && IN_FASTRECOVERY(tp) &&
|
|
SEQ_GEQ(th->th_ack, tp->snd_recover))
|
|
EXIT_FASTRECOVERY(tp);
|
|
tp->snd_una = th->th_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.
|
|
*/
|
|
/* XXXjl
|
|
* we should release the tp also, and use a
|
|
* compressed state.
|
|
*/
|
|
if (so->so_state & SS_CANTRCVMORE) {
|
|
soisdisconnected(so);
|
|
callout_reset(tp->tt_2msl, tcp_maxidle,
|
|
tcp_timer_2msl, tp);
|
|
}
|
|
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) {
|
|
KASSERT(headlocked, ("headlocked"));
|
|
tcp_twstart(tp);
|
|
INP_INFO_WUNLOCK(&tcbinfo);
|
|
m_freem(m);
|
|
return;
|
|
}
|
|
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) {
|
|
tp = 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:
|
|
KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
|
|
callout_reset(tp->tt_2msl, 2 * tcp_msl,
|
|
tcp_timer_2msl, tp);
|
|
goto dropafterack;
|
|
}
|
|
}
|
|
|
|
step6:
|
|
/*
|
|
* Update window information.
|
|
* Don't look at window if no ACK: TAC's send garbage on first SYN.
|
|
*/
|
|
if ((thflags & TH_ACK) &&
|
|
(SEQ_LT(tp->snd_wl1, th->th_seq) ||
|
|
(tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
|
|
(tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
|
|
/* keep track of pure window updates */
|
|
if (tlen == 0 &&
|
|
tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
|
|
tcpstat.tcps_rcvwinupd++;
|
|
tp->snd_wnd = tiwin;
|
|
tp->snd_wl1 = th->th_seq;
|
|
tp->snd_wl2 = th->th_ack;
|
|
if (tp->snd_wnd > tp->max_sndwnd)
|
|
tp->max_sndwnd = tp->snd_wnd;
|
|
needoutput = 1;
|
|
}
|
|
|
|
/*
|
|
* Process segments with URG.
|
|
*/
|
|
if ((thflags & TH_URG) && th->th_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 (th->th_urp + so->so_rcv.sb_cc > sb_max) {
|
|
th->th_urp = 0; /* XXX */
|
|
thflags &= ~TH_URG; /* XXX */
|
|
goto dodata; /* XXX */
|
|
}
|
|
/*
|
|
* 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(th->th_seq+th->th_urp, tp->rcv_up)) {
|
|
tp->rcv_up = th->th_seq + th->th_urp;
|
|
so->so_oobmark = so->so_rcv.sb_cc +
|
|
(tp->rcv_up - tp->rcv_nxt) - 1;
|
|
if (so->so_oobmark == 0)
|
|
so->so_state |= SS_RCVATMARK;
|
|
sohasoutofband(so);
|
|
tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
|
|
}
|
|
/*
|
|
* Remove out of band data so doesn't get presented to user.
|
|
* This can happen independent of advancing the URG pointer,
|
|
* but if two URG's are pending at once, some out-of-band
|
|
* data may creep in... ick.
|
|
*/
|
|
if (th->th_urp <= (u_long)tlen &&
|
|
!(so->so_options & SO_OOBINLINE)) {
|
|
/* hdr drop is delayed */
|
|
tcp_pulloutofband(so, th, m, drop_hdrlen);
|
|
}
|
|
} 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: /* XXX */
|
|
KASSERT(headlocked, ("headlocked"));
|
|
/*
|
|
* 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 ((tlen || (thflags & TH_FIN)) &&
|
|
TCPS_HAVERCVDFIN(tp->t_state) == 0) {
|
|
m_adj(m, drop_hdrlen); /* delayed header drop */
|
|
/*
|
|
* Insert segment which includes th into TCP reassembly queue
|
|
* with control block tp. Set thflags to whether reassembly now
|
|
* includes a segment with FIN. This handles the common case
|
|
* inline (segment is the next to be received on an established
|
|
* connection, and the queue is empty), avoiding linkage into
|
|
* and removal from the queue and repetition of various
|
|
* conversions.
|
|
* Set DELACK for segments received in order, but ack
|
|
* immediately when segments are out of order (so
|
|
* fast retransmit can work).
|
|
*/
|
|
if (th->th_seq == tp->rcv_nxt &&
|
|
LIST_EMPTY(&tp->t_segq) &&
|
|
TCPS_HAVEESTABLISHED(tp->t_state)) {
|
|
if (DELAY_ACK(tp))
|
|
tp->t_flags |= TF_DELACK;
|
|
else
|
|
tp->t_flags |= TF_ACKNOW;
|
|
tp->rcv_nxt += tlen;
|
|
thflags = th->th_flags & TH_FIN;
|
|
tcpstat.tcps_rcvpack++;
|
|
tcpstat.tcps_rcvbyte += tlen;
|
|
ND6_HINT(tp);
|
|
if (so->so_state & SS_CANTRCVMORE)
|
|
m_freem(m);
|
|
else
|
|
sbappendstream(&so->so_rcv, m);
|
|
sorwakeup(so);
|
|
} else {
|
|
thflags = tcp_reass(tp, th, &tlen, m);
|
|
tp->t_flags |= TF_ACKNOW;
|
|
}
|
|
|
|
/*
|
|
* Note the amount of data that peer has sent into
|
|
* our window, in order to estimate the sender's
|
|
* buffer size.
|
|
*/
|
|
len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
|
|
} else {
|
|
m_freem(m);
|
|
thflags &= ~TH_FIN;
|
|
}
|
|
|
|
/*
|
|
* If FIN is received ACK the FIN and let the user know
|
|
* that the connection is closing.
|
|
*/
|
|
if (thflags & TH_FIN) {
|
|
if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
|
|
socantrcvmore(so);
|
|
/*
|
|
* If connection is half-synchronized
|
|
* (ie NEEDSYN flag on) then delay ACK,
|
|
* so it may be piggybacked when SYN is sent.
|
|
* Otherwise, since we received a FIN then no
|
|
* more input can be expected, send ACK now.
|
|
*/
|
|
if (tp->t_flags & TF_NEEDSYN)
|
|
tp->t_flags |= TF_DELACK;
|
|
else
|
|
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:
|
|
tp->t_starttime = ticks;
|
|
/*FALLTHROUGH*/
|
|
case TCPS_ESTABLISHED:
|
|
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:
|
|
KASSERT(headlocked == 1, ("headlocked should be 1"));
|
|
tcp_twstart(tp);
|
|
INP_INFO_WUNLOCK(&tcbinfo);
|
|
return;
|
|
|
|
/*
|
|
* In TIME_WAIT state restart the 2 MSL time_wait timer.
|
|
*/
|
|
case TCPS_TIME_WAIT:
|
|
KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
|
|
callout_reset(tp->tt_2msl, 2 * tcp_msl,
|
|
tcp_timer_2msl, tp);
|
|
break;
|
|
}
|
|
}
|
|
INP_INFO_WUNLOCK(&tcbinfo);
|
|
#ifdef TCPDEBUG
|
|
if (so->so_options & SO_DEBUG)
|
|
tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
|
|
&tcp_savetcp, 0);
|
|
#endif
|
|
|
|
/*
|
|
* Return any desired output.
|
|
*/
|
|
if (needoutput || (tp->t_flags & TF_ACKNOW))
|
|
(void) tcp_output(tp);
|
|
|
|
check_delack:
|
|
if (tp->t_flags & TF_DELACK) {
|
|
tp->t_flags &= ~TF_DELACK;
|
|
callout_reset(tp->tt_delack, tcp_delacktime,
|
|
tcp_timer_delack, tp);
|
|
}
|
|
INP_UNLOCK(inp);
|
|
return;
|
|
|
|
dropafterack:
|
|
/*
|
|
* Generate an ACK dropping incoming segment if it occupies
|
|
* sequence space, where the ACK reflects our state.
|
|
*
|
|
* We can now skip the test for the RST flag since all
|
|
* paths to this code happen after packets containing
|
|
* RST have been dropped.
|
|
*
|
|
* In the SYN-RECEIVED state, don't send an ACK unless the
|
|
* segment we received passes the SYN-RECEIVED ACK test.
|
|
* If it fails send a RST. This breaks the loop in the
|
|
* "LAND" DoS attack, and also prevents an ACK storm
|
|
* between two listening ports that have been sent forged
|
|
* SYN segments, each with the source address of the other.
|
|
*/
|
|
if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
|
|
(SEQ_GT(tp->snd_una, th->th_ack) ||
|
|
SEQ_GT(th->th_ack, tp->snd_max)) ) {
|
|
rstreason = BANDLIM_RST_OPENPORT;
|
|
goto dropwithreset;
|
|
}
|
|
#ifdef TCPDEBUG
|
|
if (so->so_options & SO_DEBUG)
|
|
tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
|
|
&tcp_savetcp, 0);
|
|
#endif
|
|
KASSERT(headlocked, ("headlocked should be 1"));
|
|
INP_INFO_WUNLOCK(&tcbinfo);
|
|
m_freem(m);
|
|
tp->t_flags |= TF_ACKNOW;
|
|
(void) tcp_output(tp);
|
|
INP_UNLOCK(inp);
|
|
return;
|
|
|
|
dropwithreset:
|
|
/*
|
|
* Generate a RST, dropping incoming segment.
|
|
* Make ACK acceptable to originator of segment.
|
|
* Don't bother to respond if destination was broadcast/multicast.
|
|
*/
|
|
if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
|
|
goto drop;
|
|
if (isipv6) {
|
|
if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
|
|
IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
|
|
goto drop;
|
|
} else {
|
|
if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
|
|
IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
|
|
ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
|
|
in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
|
|
goto drop;
|
|
}
|
|
/* IPv6 anycast check is done at tcp6_input() */
|
|
|
|
/*
|
|
* Perform bandwidth limiting.
|
|
*/
|
|
if (badport_bandlim(rstreason) < 0)
|
|
goto drop;
|
|
|
|
#ifdef TCPDEBUG
|
|
if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
|
|
tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
|
|
&tcp_savetcp, 0);
|
|
#endif
|
|
|
|
if (thflags & TH_ACK)
|
|
/* mtod() below is safe as long as hdr dropping is delayed */
|
|
tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
|
|
TH_RST);
|
|
else {
|
|
if (thflags & TH_SYN)
|
|
tlen++;
|
|
/* mtod() below is safe as long as hdr dropping is delayed */
|
|
tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
|
|
(tcp_seq)0, TH_RST|TH_ACK);
|
|
}
|
|
|
|
if (tp)
|
|
INP_UNLOCK(inp);
|
|
if (headlocked)
|
|
INP_INFO_WUNLOCK(&tcbinfo);
|
|
return;
|
|
|
|
drop:
|
|
/*
|
|
* Drop space held by incoming segment and return.
|
|
*/
|
|
#ifdef TCPDEBUG
|
|
if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
|
|
tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
|
|
&tcp_savetcp, 0);
|
|
#endif
|
|
if (tp)
|
|
INP_UNLOCK(inp);
|
|
m_freem(m);
|
|
if (headlocked)
|
|
INP_INFO_WUNLOCK(&tcbinfo);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Parse TCP options and place in tcpopt.
|
|
*/
|
|
static void
|
|
tcp_dooptions(to, cp, cnt, is_syn)
|
|
struct tcpopt *to;
|
|
u_char *cp;
|
|
int cnt;
|
|
int is_syn;
|
|
{
|
|
int opt, optlen;
|
|
|
|
to->to_flags = 0;
|
|
for (; cnt > 0; cnt -= optlen, cp += optlen) {
|
|
opt = cp[0];
|
|
if (opt == TCPOPT_EOL)
|
|
break;
|
|
if (opt == TCPOPT_NOP)
|
|
optlen = 1;
|
|
else {
|
|
if (cnt < 2)
|
|
break;
|
|
optlen = cp[1];
|
|
if (optlen < 2 || optlen > cnt)
|
|
break;
|
|
}
|
|
switch (opt) {
|
|
case TCPOPT_MAXSEG:
|
|
if (optlen != TCPOLEN_MAXSEG)
|
|
continue;
|
|
if (!is_syn)
|
|
continue;
|
|
to->to_flags |= TOF_MSS;
|
|
bcopy((char *)cp + 2,
|
|
(char *)&to->to_mss, sizeof(to->to_mss));
|
|
to->to_mss = ntohs(to->to_mss);
|
|
break;
|
|
case TCPOPT_WINDOW:
|
|
if (optlen != TCPOLEN_WINDOW)
|
|
continue;
|
|
if (! is_syn)
|
|
continue;
|
|
to->to_flags |= TOF_SCALE;
|
|
to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
|
|
break;
|
|
case TCPOPT_TIMESTAMP:
|
|
if (optlen != TCPOLEN_TIMESTAMP)
|
|
continue;
|
|
to->to_flags |= TOF_TS;
|
|
bcopy((char *)cp + 2,
|
|
(char *)&to->to_tsval, sizeof(to->to_tsval));
|
|
to->to_tsval = ntohl(to->to_tsval);
|
|
bcopy((char *)cp + 6,
|
|
(char *)&to->to_tsecr, sizeof(to->to_tsecr));
|
|
to->to_tsecr = ntohl(to->to_tsecr);
|
|
break;
|
|
case TCPOPT_CC:
|
|
if (optlen != TCPOLEN_CC)
|
|
continue;
|
|
to->to_flags |= TOF_CC;
|
|
bcopy((char *)cp + 2,
|
|
(char *)&to->to_cc, sizeof(to->to_cc));
|
|
to->to_cc = ntohl(to->to_cc);
|
|
break;
|
|
case TCPOPT_CCNEW:
|
|
if (optlen != TCPOLEN_CC)
|
|
continue;
|
|
if (!is_syn)
|
|
continue;
|
|
to->to_flags |= TOF_CCNEW;
|
|
bcopy((char *)cp + 2,
|
|
(char *)&to->to_cc, sizeof(to->to_cc));
|
|
to->to_cc = ntohl(to->to_cc);
|
|
break;
|
|
case TCPOPT_CCECHO:
|
|
if (optlen != TCPOLEN_CC)
|
|
continue;
|
|
if (!is_syn)
|
|
continue;
|
|
to->to_flags |= TOF_CCECHO;
|
|
bcopy((char *)cp + 2,
|
|
(char *)&to->to_ccecho, sizeof(to->to_ccecho));
|
|
to->to_ccecho = ntohl(to->to_ccecho);
|
|
break;
|
|
default:
|
|
continue;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
static void
|
|
tcp_pulloutofband(so, th, m, off)
|
|
struct socket *so;
|
|
struct tcphdr *th;
|
|
register struct mbuf *m;
|
|
int off; /* delayed to be droped hdrlen */
|
|
{
|
|
int cnt = off + th->th_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;
|
|
bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
|
|
m->m_len--;
|
|
if (m->m_flags & M_PKTHDR)
|
|
m->m_pkthdr.len--;
|
|
return;
|
|
}
|
|
cnt -= m->m_len;
|
|
m = m->m_next;
|
|
if (m == 0)
|
|
break;
|
|
}
|
|
panic("tcp_pulloutofband");
|
|
}
|
|
|
|
/*
|
|
* Collect new round-trip time estimate
|
|
* and update averages and current timeout.
|
|
*/
|
|
static void
|
|
tcp_xmit_timer(tp, rtt)
|
|
register struct tcpcb *tp;
|
|
int rtt;
|
|
{
|
|
register int delta;
|
|
|
|
tcpstat.tcps_rttupdated++;
|
|
tp->t_rttupdated++;
|
|
if (tp->t_srtt != 0) {
|
|
/*
|
|
* srtt is stored as fixed point with 5 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) << TCP_DELTA_SHIFT)
|
|
- (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_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 4 bits after the
|
|
* binary point (scaled by 16). 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 - TCP_DELTA_SHIFT);
|
|
if ((tp->t_rttvar += delta) <= 0)
|
|
tp->t_rttvar = 1;
|
|
if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
|
|
tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
|
|
} 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_rttbest = tp->t_srtt + tp->t_rttvar;
|
|
}
|
|
tp->t_rtttime = 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),
|
|
max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
|
|
|
|
/*
|
|
* 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.
|
|
*
|
|
* Also take into account the space needed for options that we
|
|
* send regularly. Make maxseg shorter by that amount to assure
|
|
* that we can send maxseg amount of data even when the options
|
|
* are present. Store the upper limit of the length of options plus
|
|
* data in maxopd.
|
|
*
|
|
*
|
|
* In case of T/TCP, we call this routine during implicit connection
|
|
* setup as well (offer = -1), to initialize maxseg from the cached
|
|
* MSS of our peer.
|
|
*
|
|
* NOTE that this routine is only called when we process an incoming
|
|
* segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt().
|
|
*/
|
|
void
|
|
tcp_mss(tp, offer)
|
|
struct tcpcb *tp;
|
|
int offer;
|
|
{
|
|
int rtt, mss;
|
|
u_long bufsize;
|
|
u_long maxmtu;
|
|
struct inpcb *inp = tp->t_inpcb;
|
|
struct socket *so;
|
|
struct hc_metrics_lite metrics;
|
|
struct rmxp_tao tao;
|
|
int origoffer = offer;
|
|
#ifdef INET6
|
|
int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
|
|
size_t min_protoh = isipv6 ?
|
|
sizeof (struct ip6_hdr) + sizeof (struct tcphdr) :
|
|
sizeof (struct tcpiphdr);
|
|
#else
|
|
const size_t min_protoh = sizeof(struct tcpiphdr);
|
|
#endif
|
|
bzero(&tao, sizeof(tao));
|
|
|
|
/* initialize */
|
|
#ifdef INET6
|
|
if (isipv6) {
|
|
maxmtu = tcp_maxmtu6(&inp->inp_inc);
|
|
tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt;
|
|
} else
|
|
#endif
|
|
{
|
|
maxmtu = tcp_maxmtu(&inp->inp_inc);
|
|
tp->t_maxopd = tp->t_maxseg = tcp_mssdflt;
|
|
}
|
|
so = inp->inp_socket;
|
|
|
|
/*
|
|
* no route to sender, take default mss and return
|
|
*/
|
|
if (maxmtu == 0)
|
|
return;
|
|
|
|
/* what have we got? */
|
|
switch (offer) {
|
|
case 0:
|
|
/*
|
|
* Offer == 0 means that there was no MSS on the SYN
|
|
* segment, in this case we use tcp_mssdflt.
|
|
*/
|
|
offer =
|
|
#ifdef INET6
|
|
isipv6 ? tcp_v6mssdflt :
|
|
#endif
|
|
tcp_mssdflt;
|
|
break;
|
|
|
|
case -1:
|
|
/*
|
|
* Offer == -1 means that we didn't receive SYN yet,
|
|
* use cached value in that case;
|
|
*/
|
|
if (tcp_do_rfc1644)
|
|
tcp_hc_gettao(&inp->inp_inc, &tao);
|
|
if (tao.tao_mssopt != 0)
|
|
offer = tao.tao_mssopt;
|
|
/* FALLTHROUGH */
|
|
|
|
default:
|
|
/*
|
|
* Prevent DoS attack with too small MSS. Round up
|
|
* to at least minmss.
|
|
*/
|
|
offer = max(offer, tcp_minmss);
|
|
/*
|
|
* Sanity check: make sure that maxopd will be large
|
|
* enough to allow some data on segments even if the
|
|
* all the option space is used (40bytes). Otherwise
|
|
* funny things may happen in tcp_output.
|
|
*/
|
|
offer = max(offer, 64);
|
|
if (tcp_do_rfc1644)
|
|
tcp_hc_updatetao(&inp->inp_inc,
|
|
TCP_HC_TAO_MSSOPT, 0, offer);
|
|
}
|
|
|
|
/*
|
|
* rmx information is now retrieved from tcp_hostcache
|
|
*/
|
|
tcp_hc_get(&inp->inp_inc, &metrics);
|
|
|
|
/*
|
|
* if there's a discovered mtu int tcp hostcache, use it
|
|
* else, use the link mtu.
|
|
*/
|
|
if (metrics.rmx_mtu)
|
|
mss = metrics.rmx_mtu - min_protoh;
|
|
else {
|
|
#ifdef INET6
|
|
if (isipv6) {
|
|
mss = maxmtu - min_protoh;
|
|
if (!path_mtu_discovery &&
|
|
!in6_localaddr(&inp->in6p_faddr))
|
|
mss = min(mss, tcp_v6mssdflt);
|
|
} else
|
|
#endif
|
|
{
|
|
mss = maxmtu - min_protoh;
|
|
if (!path_mtu_discovery &&
|
|
!in_localaddr(inp->inp_faddr))
|
|
mss = min(mss, tcp_mssdflt);
|
|
}
|
|
}
|
|
mss = min(mss, offer);
|
|
|
|
/*
|
|
* maxopd stores the maximum length of data AND options
|
|
* in a segment; maxseg is the amount of data in a normal
|
|
* segment. We need to store this value (maxopd) apart
|
|
* from maxseg, because now every segment carries options
|
|
* and thus we normally have somewhat less data in segments.
|
|
*/
|
|
tp->t_maxopd = mss;
|
|
|
|
/*
|
|
* In case of T/TCP, origoffer==-1 indicates, that no segments
|
|
* were received yet. In this case we just guess, otherwise
|
|
* we do the same as before T/TCP.
|
|
*/
|
|
if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
|
|
(origoffer == -1 ||
|
|
(tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
|
|
mss -= TCPOLEN_TSTAMP_APPA;
|
|
if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC &&
|
|
(origoffer == -1 ||
|
|
(tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC))
|
|
mss -= TCPOLEN_CC_APPA;
|
|
tp->t_maxseg = mss;
|
|
|
|
#if (MCLBYTES & (MCLBYTES - 1)) == 0
|
|
if (mss > MCLBYTES)
|
|
mss &= ~(MCLBYTES-1);
|
|
#else
|
|
if (mss > MCLBYTES)
|
|
mss = mss / MCLBYTES * MCLBYTES;
|
|
#endif
|
|
tp->t_maxseg = mss;
|
|
|
|
/*
|
|
* If there's a pipesize, change the socket buffer to that size,
|
|
* don't change if sb_hiwat is different than default (then it
|
|
* has been changed on purpose with setsockopt).
|
|
* Make the socket buffers an integral number of mss units;
|
|
* if the mss is larger than the socket buffer, decrease the mss.
|
|
*/
|
|
if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe)
|
|
bufsize = metrics.rmx_sendpipe;
|
|
else
|
|
bufsize = so->so_snd.sb_hiwat;
|
|
if (bufsize < mss)
|
|
mss = bufsize;
|
|
else {
|
|
bufsize = roundup(bufsize, mss);
|
|
if (bufsize > sb_max)
|
|
bufsize = sb_max;
|
|
if (bufsize > so->so_snd.sb_hiwat)
|
|
(void)sbreserve(&so->so_snd, bufsize, so, NULL);
|
|
}
|
|
tp->t_maxseg = mss;
|
|
|
|
if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe)
|
|
bufsize = metrics.rmx_recvpipe;
|
|
else
|
|
bufsize = so->so_rcv.sb_hiwat;
|
|
if (bufsize > mss) {
|
|
bufsize = roundup(bufsize, mss);
|
|
if (bufsize > sb_max)
|
|
bufsize = sb_max;
|
|
if (bufsize > so->so_rcv.sb_hiwat)
|
|
(void)sbreserve(&so->so_rcv, bufsize, so, NULL);
|
|
}
|
|
/*
|
|
* While we're here, check the others too
|
|
*/
|
|
if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) {
|
|
tp->t_srtt = rtt;
|
|
tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
|
|
tcpstat.tcps_usedrtt++;
|
|
if (metrics.rmx_rttvar) {
|
|
tp->t_rttvar = metrics.rmx_rttvar;
|
|
tcpstat.tcps_usedrttvar++;
|
|
} else {
|
|
/* default variation is +- 1 rtt */
|
|
tp->t_rttvar =
|
|
tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
|
|
}
|
|
TCPT_RANGESET(tp->t_rxtcur,
|
|
((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
|
|
tp->t_rttmin, TCPTV_REXMTMAX);
|
|
}
|
|
if (metrics.rmx_ssthresh) {
|
|
/*
|
|
* There's some sort of gateway or interface
|
|
* buffer limit on the path. Use this to set
|
|
* the slow start threshhold, but set the
|
|
* threshold to no less than 2*mss.
|
|
*/
|
|
tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh);
|
|
tcpstat.tcps_usedssthresh++;
|
|
}
|
|
if (metrics.rmx_bandwidth)
|
|
tp->snd_bandwidth = metrics.rmx_bandwidth;
|
|
|
|
/*
|
|
* Set the slow-start flight size depending on whether this
|
|
* is a local network or not.
|
|
*
|
|
* Extend this so we cache the cwnd too and retrieve it here.
|
|
* Make cwnd even bigger than RFC3390 suggests but only if we
|
|
* have previous experience with the remote host. Be careful
|
|
* not make cwnd bigger than remote receive window or our own
|
|
* send socket buffer. Maybe put some additional upper bound
|
|
* on the retrieved cwnd. Should do incremental updates to
|
|
* hostcache when cwnd collapses so next connection doesn't
|
|
* overloads the path again.
|
|
*
|
|
* RFC3390 says only do this if SYN or SYN/ACK didn't got lost.
|
|
* We currently check only in syncache_socket for that.
|
|
*/
|
|
#define TCP_METRICS_CWND
|
|
#ifdef TCP_METRICS_CWND
|
|
if (metrics.rmx_cwnd)
|
|
tp->snd_cwnd = max(mss,
|
|
min(metrics.rmx_cwnd / 2,
|
|
min(tp->snd_wnd, so->so_snd.sb_hiwat)));
|
|
else
|
|
#endif
|
|
if (tcp_do_rfc3390)
|
|
tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380));
|
|
#ifdef INET6
|
|
else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
|
|
(!isipv6 && in_localaddr(inp->inp_faddr)))
|
|
#else
|
|
else if (in_localaddr(inp->inp_faddr))
|
|
#endif
|
|
tp->snd_cwnd = mss * ss_fltsz_local;
|
|
else
|
|
tp->snd_cwnd = mss * ss_fltsz;
|
|
}
|
|
|
|
/*
|
|
* Determine the MSS option to send on an outgoing SYN.
|
|
*/
|
|
int
|
|
tcp_mssopt(inc)
|
|
struct in_conninfo *inc;
|
|
{
|
|
int mss = 0;
|
|
u_long maxmtu = 0;
|
|
u_long thcmtu = 0;
|
|
size_t min_protoh;
|
|
#ifdef INET6
|
|
int isipv6 = inc->inc_isipv6 ? 1 : 0;
|
|
#endif
|
|
|
|
KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer"));
|
|
|
|
#ifdef INET6
|
|
if (isipv6) {
|
|
mss = tcp_v6mssdflt;
|
|
maxmtu = tcp_maxmtu6(inc);
|
|
thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
|
|
min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
|
|
} else
|
|
#endif
|
|
{
|
|
mss = tcp_mssdflt;
|
|
maxmtu = tcp_maxmtu(inc);
|
|
thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
|
|
min_protoh = sizeof(struct tcpiphdr);
|
|
}
|
|
if (maxmtu && thcmtu)
|
|
mss = min(maxmtu, thcmtu) - min_protoh;
|
|
else if (maxmtu || thcmtu)
|
|
mss = max(maxmtu, thcmtu) - min_protoh;
|
|
|
|
return (mss);
|
|
}
|
|
|
|
|
|
/*
|
|
* On a partial ack arrives, force the retransmission of the
|
|
* next unacknowledged segment. Do not clear tp->t_dupacks.
|
|
* By setting snd_nxt to ti_ack, this forces retransmission timer to
|
|
* be started again.
|
|
*/
|
|
static void
|
|
tcp_newreno_partial_ack(tp, th)
|
|
struct tcpcb *tp;
|
|
struct tcphdr *th;
|
|
{
|
|
tcp_seq onxt = tp->snd_nxt;
|
|
u_long ocwnd = tp->snd_cwnd;
|
|
|
|
callout_stop(tp->tt_rexmt);
|
|
tp->t_rtttime = 0;
|
|
tp->snd_nxt = th->th_ack;
|
|
/*
|
|
* Set snd_cwnd to one segment beyond acknowledged offset.
|
|
* (tp->snd_una has not yet been updated when this function is called.)
|
|
*/
|
|
tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una);
|
|
tp->t_flags |= TF_ACKNOW;
|
|
(void) tcp_output(tp);
|
|
tp->snd_cwnd = ocwnd;
|
|
if (SEQ_GT(onxt, tp->snd_nxt))
|
|
tp->snd_nxt = onxt;
|
|
/*
|
|
* Partial window deflation. Relies on fact that tp->snd_una
|
|
* not updated yet.
|
|
*/
|
|
tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg);
|
|
}
|
|
|
|
/*
|
|
* Returns 1 if the TIME_WAIT state was killed and we should start over,
|
|
* looking for a pcb in the listen state. Returns 0 otherwise.
|
|
*/
|
|
static int
|
|
tcp_timewait(tw, to, th, m, tlen)
|
|
struct tcptw *tw;
|
|
struct tcpopt *to;
|
|
struct tcphdr *th;
|
|
struct mbuf *m;
|
|
int tlen;
|
|
{
|
|
int thflags;
|
|
tcp_seq seq;
|
|
#ifdef INET6
|
|
int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
|
|
#else
|
|
const int isipv6 = 0;
|
|
#endif
|
|
|
|
thflags = th->th_flags;
|
|
|
|
/*
|
|
* NOTE: for FIN_WAIT_2 (to be added later),
|
|
* must validate sequence number before accepting RST
|
|
*/
|
|
|
|
/*
|
|
* If the segment contains RST:
|
|
* Drop the segment - see Stevens, vol. 2, p. 964 and
|
|
* RFC 1337.
|
|
*/
|
|
if (thflags & TH_RST)
|
|
goto drop;
|
|
|
|
/*
|
|
* If segment contains a SYN and CC [not CC.NEW] option:
|
|
* if connection duration > MSL, drop packet and send RST;
|
|
*
|
|
* if SEG.CC > CCrecv then is new SYN.
|
|
* Complete close and delete TCPCB. Then reprocess
|
|
* segment, hoping to find new TCPCB in LISTEN state;
|
|
*
|
|
* else must be old SYN; drop it.
|
|
* else do normal processing.
|
|
*/
|
|
if ((thflags & TH_SYN) && (to->to_flags & TOF_CC) && tw->cc_recv != 0) {
|
|
if ((ticks - tw->t_starttime) > tcp_msl)
|
|
goto reset;
|
|
if (CC_GT(to->to_cc, tw->cc_recv)) {
|
|
(void) tcp_twclose(tw, 0);
|
|
return (1);
|
|
}
|
|
goto drop;
|
|
}
|
|
|
|
#if 0
|
|
/* PAWS not needed at the moment */
|
|
/*
|
|
* RFC 1323 PAWS: If we have a timestamp reply on this segment
|
|
* and it's less than ts_recent, drop it.
|
|
*/
|
|
if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
|
|
TSTMP_LT(to.to_tsval, tp->ts_recent)) {
|
|
if ((thflags & TH_ACK) == 0)
|
|
goto drop;
|
|
goto ack;
|
|
}
|
|
/*
|
|
* ts_recent is never updated because we never accept new segments.
|
|
*/
|
|
#endif
|
|
|
|
/*
|
|
* 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 ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) {
|
|
(void) tcp_twclose(tw, 0);
|
|
return (1);
|
|
}
|
|
|
|
/*
|
|
* Drop the the segment if it does not contain an ACK.
|
|
*/
|
|
if ((thflags & TH_ACK) == 0)
|
|
goto drop;
|
|
|
|
/*
|
|
* Reset the 2MSL timer if this is a duplicate FIN.
|
|
*/
|
|
if (thflags & TH_FIN) {
|
|
seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0);
|
|
if (seq + 1 == tw->rcv_nxt)
|
|
tcp_timer_2msl_reset(tw, 2 * tcp_msl);
|
|
}
|
|
|
|
/*
|
|
* Acknowledge the segment if it has data or is not a duplicate ACK.
|
|
*/
|
|
if (thflags != TH_ACK || tlen != 0 ||
|
|
th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt)
|
|
tcp_twrespond(tw, NULL, m, TH_ACK);
|
|
goto drop;
|
|
|
|
reset:
|
|
/*
|
|
* Generate a RST, dropping incoming segment.
|
|
* Make ACK acceptable to originator of segment.
|
|
* Don't bother to respond if destination was broadcast/multicast.
|
|
*/
|
|
if (m->m_flags & (M_BCAST|M_MCAST))
|
|
goto drop;
|
|
if (isipv6) {
|
|
struct ip6_hdr *ip6;
|
|
|
|
/* IPv6 anycast check is done at tcp6_input() */
|
|
ip6 = mtod(m, struct ip6_hdr *);
|
|
if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
|
|
IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
|
|
goto drop;
|
|
} else {
|
|
struct ip *ip;
|
|
|
|
ip = mtod(m, struct ip *);
|
|
if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
|
|
IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
|
|
ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
|
|
in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
|
|
goto drop;
|
|
}
|
|
if (thflags & TH_ACK) {
|
|
tcp_respond(NULL,
|
|
mtod(m, void *), th, m, 0, th->th_ack, TH_RST);
|
|
} else {
|
|
seq = th->th_seq + (thflags & TH_SYN ? 1 : 0);
|
|
tcp_respond(NULL,
|
|
mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK);
|
|
}
|
|
INP_UNLOCK(tw->tw_inpcb);
|
|
return (0);
|
|
|
|
drop:
|
|
INP_UNLOCK(tw->tw_inpcb);
|
|
m_freem(m);
|
|
return (0);
|
|
}
|