1296 lines
34 KiB
C
1296 lines
34 KiB
C
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/*
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* Copyright (c) 1982, 1986, 1988 Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms are permitted
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* provided that this notice is preserved and that due credit is given
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* to the University of California at Berkeley. The name of the University
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* may not be used to endorse or promote products derived from this
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* software without specific prior written permission. This software
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* is provided ``as is'' without express or implied warranty.
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*
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* @(#)tcp_input.c 1.1 94/10/31 SMI; from UCB 7.15.1.2 3/16/88
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/mbuf.h>
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#include <sys/protosw.h>
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#include <sys/socket.h>
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#include <sys/socketvar.h>
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#include <sys/errno.h>
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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/ip.h>
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#include <netinet/ip_var.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 <netinet/tcpip.h>
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#include <netinet/tcp_debug.h>
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int tcpprintfs = 0;
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int tcprexmtthresh = 3;
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struct tcpiphdr tcp_saveti;
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extern int tcp_nodelack;
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extern int tcp_default_mss;
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struct tcpcb *tcp_newtcpcb();
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/*
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* Insert segment ti into reassembly queue of tcp with
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* control block tp. Return TH_FIN if reassembly now includes
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* a segment with FIN. The macro form does the common case inline
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* (segment is the next to be received on an established connection,
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* and the queue is empty), avoiding linkage into and removal
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* from the queue and repetition of various conversions.
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*/
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#define TCP_REASS(tp, ti, m, so, flags) { \
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if ((ti)->ti_seq == (tp)->rcv_nxt && \
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(tp)->seg_next == (struct tcpiphdr *)(tp) && \
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(tp)->t_state == TCPS_ESTABLISHED) { \
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(tp)->rcv_nxt += (ti)->ti_len; \
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flags = (ti)->ti_flags & TH_FIN; \
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tcpstat.tcps_rcvpack++;\
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tcpstat.tcps_rcvbyte += (ti)->ti_len;\
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sbappend(&(so)->so_rcv, (m)); \
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sorwakeup(so); \
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} else \
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(flags) = tcp_reass((tp), (ti)); \
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}
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tcp_reass(tp, ti)
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register struct tcpcb *tp;
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register struct tcpiphdr *ti;
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{
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register struct tcpiphdr *q;
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struct socket *so = tp->t_inpcb->inp_socket;
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struct mbuf *m;
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int flags;
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/*
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* Call with ti==0 after become established to
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* force pre-ESTABLISHED data up to user socket.
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*/
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if (ti == 0)
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goto present;
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/*
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* Find a segment which begins after this one does.
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*/
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for (q = tp->seg_next; q != (struct tcpiphdr *)tp;
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q = (struct tcpiphdr *)q->ti_next)
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if (SEQ_GT(q->ti_seq, ti->ti_seq))
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break;
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/*
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* If there is a preceding segment, it may provide some of
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* our data already. If so, drop the data from the incoming
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* segment. If it provides all of our data, drop us.
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*/
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if ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) {
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register int i;
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q = (struct tcpiphdr *)q->ti_prev;
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/* conversion to int (in i) handles seq wraparound */
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i = q->ti_seq + q->ti_len - ti->ti_seq;
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if (i > 0) {
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if (i >= ti->ti_len) {
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tcpstat.tcps_rcvduppack++;
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tcpstat.tcps_rcvdupbyte += ti->ti_len;
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goto drop;
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}
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m_adj(dtom(ti), i);
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ti->ti_len -= i;
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ti->ti_seq += i;
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}
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q = (struct tcpiphdr *)(q->ti_next);
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}
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tcpstat.tcps_rcvoopack++;
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tcpstat.tcps_rcvoobyte += ti->ti_len;
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/*
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* While we overlap succeeding segments trim them or,
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* if they are completely covered, dequeue them.
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*/
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while (q != (struct tcpiphdr *)tp) {
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register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq;
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if (i <= 0)
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break;
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if (i < q->ti_len) {
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q->ti_seq += i;
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q->ti_len -= i;
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m_adj(dtom(q), i);
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break;
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}
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q = (struct tcpiphdr *)q->ti_next;
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m = dtom(q->ti_prev);
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remque(q->ti_prev);
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m_freem(m);
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}
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/*
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* Stick new segment in its place.
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*/
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insque(ti, q->ti_prev);
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present:
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/*
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* Present data to user, advancing rcv_nxt through
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* completed sequence space.
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*/
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if (TCPS_HAVERCVDSYN(tp->t_state) == 0)
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return (0);
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ti = tp->seg_next;
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if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt)
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return (0);
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if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len)
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return (0);
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do {
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tp->rcv_nxt += ti->ti_len;
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flags = ti->ti_flags & TH_FIN;
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remque(ti);
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m = dtom(ti);
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ti = (struct tcpiphdr *)ti->ti_next;
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if (so->so_state & SS_CANTRCVMORE)
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m_freem(m);
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else
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sbappend(&so->so_rcv, m);
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} while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt);
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sorwakeup(so);
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return (flags);
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drop:
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m_freem(dtom(ti));
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return (0);
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}
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struct inpcb *tcp_last_inp;
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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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tcp_input(m0)
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struct mbuf *m0;
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{
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register struct tcpiphdr *ti;
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static struct inpcb *inp;
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register struct mbuf *m;
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struct mbuf *om = 0;
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int len, tlen, off;
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register struct tcpcb *tp = 0;
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register int tiflags;
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struct socket *so;
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int todrop, acked, ourfinisacked, needoutput = 0;
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short ostate;
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struct in_addr laddr;
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int dropsocket = 0;
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int iss = 0;
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tcpstat.tcps_rcvtotal++;
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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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m = m0;
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ti = mtod(m, struct tcpiphdr *);
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if (((struct ip *)ti)->ip_hl > (sizeof (struct ip) >> 2))
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ip_stripoptions((struct ip *)ti, (struct mbuf *)0);
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if (m->m_off > MMAXOFF || 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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ti = mtod(m, struct tcpiphdr *);
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}
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/*
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* Checksum extended TCP header and data.
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*/
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tlen = ((struct ip *)ti)->ip_len;
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len = sizeof (struct ip) + tlen;
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ti->ti_next = ti->ti_prev = 0;
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ti->ti_x1 = 0;
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ti->ti_len = (u_short)tlen;
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ti->ti_len = htons((u_short)ti->ti_len);
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if (ti->ti_sum = in_cksum(m, len)) {
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if (tcpprintfs)
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printf("tcp sum: src %x\n", ti->ti_src);
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tcpstat.tcps_rcvbadsum++;
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goto drop;
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}
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/*
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* Check that TCP offset makes sense,
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* pull out TCP options and adjust length.
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*/
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off = ti->ti_off << 2;
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if (off < sizeof (struct tcphdr) || off > tlen) {
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if (tcpprintfs)
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printf("tcp off: src %x off %d\n", ti->ti_src, off);
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tcpstat.tcps_rcvbadoff++;
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goto drop;
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}
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tlen -= off;
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ti->ti_len = tlen;
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if (off > sizeof (struct tcphdr)) {
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if (m->m_len < sizeof(struct ip) + off) {
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if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) {
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tcpstat.tcps_rcvshort++;
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return;
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}
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ti = mtod(m, struct tcpiphdr *);
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}
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om = m_get(M_DONTWAIT, MT_DATA);
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if (om == 0)
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goto drop;
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om->m_len = off - sizeof (struct tcphdr);
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{ caddr_t op = mtod(m, caddr_t) + sizeof (struct tcpiphdr);
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bcopy(op, mtod(om, caddr_t), (unsigned)om->m_len);
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m->m_len -= om->m_len;
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bcopy(op+om->m_len, op,
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(unsigned)(m->m_len-sizeof (struct tcpiphdr)));
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}
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}
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tiflags = ti->ti_flags;
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/*
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* Drop TCP and IP headers; TCP options were dropped above.
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*/
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m->m_off += sizeof(struct tcpiphdr);
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m->m_len -= sizeof(struct tcpiphdr);
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#if defined(sparc) || defined(sun2) || defined(sun3) || defined(sun3x)
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/*
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* Not needed on big-endian machines
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*/
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# else
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/*
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* Convert TCP protocol specific fields to host format.
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*/
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ti->ti_seq = ntohl(ti->ti_seq);
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ti->ti_ack = ntohl(ti->ti_ack);
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ti->ti_win = ntohs(ti->ti_win);
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ti->ti_urp = ntohs(ti->ti_urp);
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#endif
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/*
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* Locate pcb for segment, trying last one cache first.
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*/
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findpcb:
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inp = tcp_last_inp;
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if (tcp_last_inp == (struct inpcb *)0 ||
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inp->inp_faddr.s_addr != ti->ti_src.s_addr ||
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inp->inp_fport != ti->ti_sport ||
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inp->inp_laddr.s_addr != ti->ti_dst.s_addr ||
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inp->inp_lport != ti->ti_dport) {
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inp = in_pcblookup
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(&tcb, ti->ti_src, ti->ti_sport, ti->ti_dst, ti->ti_dport,
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INPLOOKUP_WILDCARD);
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tcp_last_inp = inp;
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}
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/*
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* If the state is CLOSED (i.e., TCB does not exist) then
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* all data in the incoming segment is discarded.
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* If the TCB exists but is in CLOSED state, it is embryonic,
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* but should either do a listen or a connect soon.
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*/
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if (inp == 0)
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goto dropwithreset;
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tp = intotcpcb(inp);
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if (tp == 0)
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goto dropwithreset;
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if (tp->t_state == TCPS_CLOSED)
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goto drop;
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so = inp->inp_socket;
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if (so->so_options & SO_DEBUG) {
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ostate = tp->t_state;
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tcp_saveti = *ti;
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}
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if (so->so_options & SO_ACCEPTCONN) {
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int save_rcv = so->so_rcv.sb_hiwat;
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int save_snd = so->so_snd.sb_hiwat;
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so = sonewconn(so);
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if (so == 0)
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goto drop;
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(void) sbreserve(&so->so_rcv, save_rcv);
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(void) sbreserve(&so->so_snd, save_snd);
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/*
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* This is ugly, but ....
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*
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* Mark socket as temporary until we're
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* committed to keeping it. The code at
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* ``drop'' and ``dropwithreset'' check the
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* flag dropsocket to see if the temporary
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* socket created here should be discarded.
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* We mark the socket as discardable until
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* we're committed to it below in TCPS_LISTEN.
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*/
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dropsocket++;
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inp = (struct inpcb *)so->so_pcb;
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inp->inp_laddr = ti->ti_dst;
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inp->inp_lport = ti->ti_dport;
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inp->inp_options = ip_srcroute();
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tp = intotcpcb(inp);
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tp->t_state = TCPS_LISTEN;
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}
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/*
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* Segment received on connection.
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* Reset idle time and keep-alive timer.
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*/
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tp->t_idle = 0;
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tp->t_timer[TCPT_KEEP] = tcp_keepidle;
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/*
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* Process options if not in LISTEN state,
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* else do it below (after getting remote address).
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*/
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if (om && tp->t_state != TCPS_LISTEN) {
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tcp_dooptions(tp, om, ti);
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om = 0;
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}
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/*
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* Calculate amount of space in receive window,
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* and then do TCP input processing.
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* Receive window is amount of space in rcv queue,
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* but not less than advertised window.
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*/
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{ int win;
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win = sbspace(&so->so_rcv);
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if (win < 0)
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win = 0;
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tp->rcv_wnd = MAX(win, (int)(tp->rcv_adv - tp->rcv_nxt));
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}
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switch (tp->t_state) {
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/*
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* If the state is LISTEN then ignore segment if it contains an RST.
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* If the segment contains an ACK then it is bad and send a RST.
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* If it does not contain a SYN then it is not interesting; drop it.
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* Don't bother responding if the destination was a broadcast.
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* Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial
|
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* tp->iss, and send a segment:
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* <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
|
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* Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss.
|
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* Fill in remote peer address fields if not previously specified.
|
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* Enter SYN_RECEIVED state, and process any other fields of this
|
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* segment in this state.
|
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*/
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case TCPS_LISTEN: {
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struct mbuf *am;
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register struct sockaddr_in *sin;
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|
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if (tiflags & TH_RST)
|
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goto drop;
|
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if (tiflags & TH_ACK)
|
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goto dropwithreset;
|
|
if ((tiflags & TH_SYN) == 0)
|
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goto drop;
|
|
if (in_broadcast(ti->ti_dst))
|
|
goto drop;
|
|
am = m_get(M_DONTWAIT, MT_SONAME);
|
|
if (am == NULL)
|
|
goto drop;
|
|
am->m_len = sizeof (struct sockaddr_in);
|
|
sin = mtod(am, struct sockaddr_in *);
|
|
sin->sin_family = AF_INET;
|
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sin->sin_addr = ti->ti_src;
|
|
sin->sin_port = ti->ti_sport;
|
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laddr = inp->inp_laddr;
|
|
if (inp->inp_laddr.s_addr == INADDR_ANY)
|
|
inp->inp_laddr = ti->ti_dst;
|
|
if (in_pcbconnect(inp, am)) {
|
|
inp->inp_laddr = laddr;
|
|
(void) m_free(am);
|
|
goto drop;
|
|
}
|
|
(void) m_free(am);
|
|
tp->t_template = tcp_template(tp);
|
|
if (tp->t_template == 0) {
|
|
tp = tcp_drop(tp, ENOBUFS);
|
|
dropsocket = 0; /* socket is already gone */
|
|
goto drop;
|
|
}
|
|
if (om) {
|
|
tcp_dooptions(tp, om, ti);
|
|
om = 0;
|
|
}
|
|
if (iss)
|
|
tp->iss = iss;
|
|
else
|
|
tp->iss = tcp_iss;
|
|
tcp_iss += TCP_ISSINCR/2;
|
|
tp->irs = ti->ti_seq;
|
|
tcp_sendseqinit(tp);
|
|
tcp_rcvseqinit(tp);
|
|
tp->t_flags |= TF_ACKNOW;
|
|
tp->t_state = TCPS_SYN_RECEIVED;
|
|
tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT;
|
|
dropsocket = 0; /* committed to socket */
|
|
tcpstat.tcps_accepts++;
|
|
goto trimthenstep6;
|
|
}
|
|
|
|
/*
|
|
* If the state is SYN_SENT:
|
|
* if seg contains an ACK, but not for our SYN, drop the input.
|
|
* if seg contains a RST, then drop the connection.
|
|
* if seg does not contain SYN, then drop it.
|
|
* Otherwise this is an acceptable SYN segment
|
|
* initialize tp->rcv_nxt and tp->irs
|
|
* if seg contains ack then advance tp->snd_una
|
|
* if SYN has been acked change to ESTABLISHED else SYN_RCVD state
|
|
* arrange for segment to be acked (eventually)
|
|
* continue processing rest of data/controls, beginning with URG
|
|
*/
|
|
case TCPS_SYN_SENT:
|
|
if ((tiflags & TH_ACK) &&
|
|
(SEQ_LEQ(ti->ti_ack, tp->iss) ||
|
|
SEQ_GT(ti->ti_ack, tp->snd_max)))
|
|
goto dropwithreset;
|
|
if (tiflags & TH_RST) {
|
|
if (tiflags & TH_ACK)
|
|
tp = tcp_drop(tp, ECONNREFUSED);
|
|
goto drop;
|
|
}
|
|
if ((tiflags & TH_SYN) == 0)
|
|
goto drop;
|
|
if (tiflags & TH_ACK) {
|
|
tp->snd_una = ti->ti_ack;
|
|
if (SEQ_LT(tp->snd_nxt, tp->snd_una))
|
|
tp->snd_nxt = tp->snd_una;
|
|
}
|
|
tp->t_timer[TCPT_REXMT] = 0;
|
|
tp->irs = ti->ti_seq;
|
|
tcp_rcvseqinit(tp);
|
|
tp->t_flags |= TF_ACKNOW;
|
|
if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) {
|
|
tcpstat.tcps_connects++;
|
|
soisconnected(so);
|
|
tp->t_state = TCPS_ESTABLISHED;
|
|
tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp));
|
|
(void) tcp_reass(tp, (struct tcpiphdr *)0);
|
|
/*
|
|
* if we didn't have to retransmit the SYN,
|
|
* use its rtt as our initial srtt & rtt var.
|
|
*/
|
|
if (tp->t_rtt) {
|
|
tp->t_srtt = tp->t_rtt << 3;
|
|
tp->t_rttvar = tp->t_rtt << 1;
|
|
TCPT_RANGESET(tp->t_rxtcur,
|
|
((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
|
|
TCPTV_MIN, TCPTV_REXMTMAX);
|
|
tp->t_rtt = 0;
|
|
}
|
|
} else
|
|
tp->t_state = TCPS_SYN_RECEIVED;
|
|
|
|
trimthenstep6:
|
|
/*
|
|
* Advance ti->ti_seq to correspond to first data byte.
|
|
* If data, trim to stay within window,
|
|
* dropping FIN if necessary.
|
|
*/
|
|
ti->ti_seq++;
|
|
if (ti->ti_len > tp->rcv_wnd) {
|
|
todrop = ti->ti_len - tp->rcv_wnd;
|
|
m_adj(m, -todrop);
|
|
ti->ti_len = tp->rcv_wnd;
|
|
tiflags &= ~TH_FIN;
|
|
tcpstat.tcps_rcvpackafterwin++;
|
|
tcpstat.tcps_rcvbyteafterwin += todrop;
|
|
}
|
|
tp->snd_wl1 = ti->ti_seq - 1;
|
|
tp->rcv_up = ti->ti_seq;
|
|
goto step6;
|
|
}
|
|
|
|
/*
|
|
* States other than LISTEN or SYN_SENT.
|
|
* First check that at least some bytes of segment are within
|
|
* receive window. If segment begins before rcv_nxt,
|
|
* drop leading data (and SYN); if nothing left, just ack.
|
|
*/
|
|
todrop = tp->rcv_nxt - ti->ti_seq;
|
|
if ((todrop > 0) && (tiflags & TH_SYN)) {
|
|
/* shave SYN off front of segment */
|
|
tiflags &= ~TH_SYN;
|
|
ti->ti_seq++;
|
|
if (ti->ti_urp > 1)
|
|
ti->ti_urp--;
|
|
else
|
|
tiflags &= ~TH_URG;
|
|
todrop--;
|
|
}
|
|
|
|
if (todrop > 0) {
|
|
if (todrop > ti->ti_len ||
|
|
todrop == ti->ti_len && (tiflags&TH_FIN) == 0) {
|
|
tcpstat.tcps_rcvduppack++;
|
|
tcpstat.tcps_rcvdupbyte += ti->ti_len;
|
|
/*
|
|
* If segment is just one to the left of the window,
|
|
* check two special cases:
|
|
* 1. Don't toss RST in response to 4.2-style keepalive.
|
|
* 2. If the only thing to drop is a FIN, we can drop
|
|
* it, but check the ACK or we will get into FIN
|
|
* wars if our FINs crossed (both CLOSING).
|
|
* In either case, send ACK to resynchronize,
|
|
* but keep on processing for RST or ACK.
|
|
*
|
|
* If segment has no data at all - i.e. its an
|
|
* ACK-only segment - go ahead and accept it since
|
|
* it may carry updated window or ack information.
|
|
*/
|
|
if ((tiflags & TH_FIN && todrop == ti->ti_len + 1) ||
|
|
(tiflags & TH_RST && ti->ti_seq ==
|
|
tp->rcv_nxt - 1) ||
|
|
(ti->ti_len == 0)) {
|
|
todrop = ti->ti_len;
|
|
tiflags &= ~TH_FIN;
|
|
tp->t_flags |= TF_ACKNOW;
|
|
} else
|
|
/* drop unacceptable packet */
|
|
goto dropafterack;
|
|
} else {
|
|
tcpstat.tcps_rcvpartduppack++;
|
|
tcpstat.tcps_rcvpartdupbyte += todrop;
|
|
}
|
|
m_adj(m, todrop);
|
|
ti->ti_seq += todrop;
|
|
ti->ti_len -= todrop;
|
|
if (ti->ti_urp > todrop)
|
|
ti->ti_urp -= todrop;
|
|
else {
|
|
tiflags &= ~TH_URG;
|
|
ti->ti_urp = 0;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If new data are received on a connection after the
|
|
* user processes are gone, then RST the other end.
|
|
*/
|
|
if ((so->so_state & SS_NOFDREF) &&
|
|
tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) {
|
|
tp = tcp_close(tp);
|
|
tcpstat.tcps_rcvafterclose++;
|
|
goto dropwithreset;
|
|
}
|
|
|
|
/*
|
|
* If segment ends after window, drop trailing data
|
|
* (and PUSH and FIN); if nothing left, just ACK.
|
|
*/
|
|
todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd);
|
|
if (todrop > 0) {
|
|
tcpstat.tcps_rcvpackafterwin++;
|
|
if (todrop >= ti->ti_len) {
|
|
tcpstat.tcps_rcvbyteafterwin += ti->ti_len;
|
|
/*
|
|
* If a new connection request is received
|
|
* while in TIME_WAIT, drop the old connection
|
|
* and start over if the sequence numbers
|
|
* are above the previous ones.
|
|
*/
|
|
if (tiflags & TH_SYN &&
|
|
tp->t_state == TCPS_TIME_WAIT &&
|
|
SEQ_GT(ti->ti_seq, tp->rcv_nxt)) {
|
|
iss = tp->rcv_nxt + TCP_ISSINCR;
|
|
tp = tcp_close(tp);
|
|
goto 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 && ti->ti_seq == tp->rcv_nxt) {
|
|
tp->t_flags |= TF_ACKNOW;
|
|
tcpstat.tcps_rcvwinprobe++;
|
|
} else
|
|
goto dropafterack;
|
|
} else
|
|
tcpstat.tcps_rcvbyteafterwin += todrop;
|
|
m_adj(m, -todrop);
|
|
ti->ti_len -= todrop;
|
|
tiflags &= ~(TH_PUSH|TH_FIN);
|
|
}
|
|
|
|
/*
|
|
* If the RST bit is set examine the state:
|
|
* SYN_RECEIVED STATE:
|
|
* If passive open, return to LISTEN state.
|
|
* If active open, inform user that connection was refused.
|
|
* ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES:
|
|
* Inform user that connection was reset, and close tcb.
|
|
* CLOSING, LAST_ACK, TIME_WAIT STATES
|
|
* Close the tcb.
|
|
*/
|
|
if (tiflags&TH_RST) switch (tp->t_state) {
|
|
|
|
case TCPS_SYN_RECEIVED:
|
|
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);
|
|
goto drop;
|
|
|
|
case TCPS_CLOSING:
|
|
case TCPS_LAST_ACK:
|
|
case TCPS_TIME_WAIT:
|
|
tp = tcp_close(tp);
|
|
goto drop;
|
|
}
|
|
|
|
/*
|
|
* If a SYN is in the window, then this is an
|
|
* error and we send an RST and drop the connection.
|
|
*/
|
|
if (tiflags & TH_SYN) {
|
|
tp = tcp_drop(tp, ECONNRESET);
|
|
goto dropwithreset;
|
|
}
|
|
|
|
/*
|
|
* If the ACK bit is off we drop the segment and return.
|
|
*/
|
|
if ((tiflags & TH_ACK) == 0)
|
|
goto drop;
|
|
|
|
/*
|
|
* Ack processing.
|
|
*/
|
|
switch (tp->t_state) {
|
|
|
|
/*
|
|
* In SYN_RECEIVED state if the ack ACKs our SYN then enter
|
|
* ESTABLISHED state and continue processing, otherwise
|
|
* send an RST.
|
|
*/
|
|
case TCPS_SYN_RECEIVED:
|
|
if (SEQ_GT(tp->snd_una, ti->ti_ack) ||
|
|
SEQ_GT(ti->ti_ack, tp->snd_max))
|
|
goto dropwithreset;
|
|
tcpstat.tcps_connects++;
|
|
soisconnected(so);
|
|
tp->t_state = TCPS_ESTABLISHED;
|
|
tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp));
|
|
(void) tcp_reass(tp, (struct tcpiphdr *)0);
|
|
tp->snd_wl1 = ti->ti_seq - 1;
|
|
/* fall into ... */
|
|
|
|
/*
|
|
* In ESTABLISHED state: drop duplicate ACKs; ACK out of range
|
|
* ACKs. If the ack is in the range
|
|
* tp->snd_una < ti->ti_ack <= tp->snd_max
|
|
* then advance tp->snd_una to ti->ti_ack and drop
|
|
* data from the retransmission queue. If this ACK reflects
|
|
* more up to date window information we update our window information.
|
|
*/
|
|
case TCPS_ESTABLISHED:
|
|
case TCPS_FIN_WAIT_1:
|
|
case TCPS_FIN_WAIT_2:
|
|
case TCPS_CLOSE_WAIT:
|
|
case TCPS_CLOSING:
|
|
case TCPS_LAST_ACK:
|
|
case TCPS_TIME_WAIT:
|
|
|
|
if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) {
|
|
if (ti->ti_len == 0 && ti->ti_win == tp->snd_wnd) {
|
|
tcpstat.tcps_rcvdupack++;
|
|
/*
|
|
* If we have outstanding data (not 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. If this packet fills the
|
|
* only hole in the receiver's seq.
|
|
* space, the next real ack will fully
|
|
* open our window. This means we
|
|
* have to do the usual slow-start to
|
|
* not overwhelm an intermediate gateway
|
|
* with a burst of packets. Leave
|
|
* here with the congestion window set
|
|
* to allow 2 packets on the next real
|
|
* ack and the exp-to-linear thresh
|
|
* set for half the current window
|
|
* size (since we know we're losing at
|
|
* the current window size).
|
|
*/
|
|
if (tp->t_timer[TCPT_REXMT] == 0 ||
|
|
ti->ti_ack != tp->snd_una)
|
|
tp->t_dupacks = 0;
|
|
else if (++tp->t_dupacks == tcprexmtthresh) {
|
|
tcp_seq onxt = tp->snd_nxt;
|
|
u_int win =
|
|
MIN(tp->snd_wnd, tp->snd_cwnd) / 2 /
|
|
tp->t_maxseg;
|
|
|
|
if (win < 2)
|
|
win = 2;
|
|
tp->snd_ssthresh = win * tp->t_maxseg;
|
|
|
|
tp->t_timer[TCPT_REXMT] = 0;
|
|
tp->t_rtt = 0;
|
|
tp->snd_nxt = ti->ti_ack;
|
|
tp->snd_cwnd = tp->t_maxseg;
|
|
(void) tcp_output(tp);
|
|
|
|
if (SEQ_GT(onxt, tp->snd_nxt))
|
|
tp->snd_nxt = onxt;
|
|
goto drop;
|
|
}
|
|
} else
|
|
tp->t_dupacks = 0;
|
|
break;
|
|
}
|
|
tp->t_dupacks = 0;
|
|
if (SEQ_GT(ti->ti_ack, tp->snd_max)) {
|
|
tcpstat.tcps_rcvacktoomuch++;
|
|
goto dropafterack;
|
|
}
|
|
acked = ti->ti_ack - tp->snd_una;
|
|
tcpstat.tcps_rcvackpack++;
|
|
tcpstat.tcps_rcvackbyte += acked;
|
|
|
|
/*
|
|
* If transmit timer is running and timed sequence
|
|
* number was acked, update smoothed round trip time.
|
|
* Since we now have an rtt measurement, cancel the
|
|
* timer backoff (cf., Phil Karn's retransmit alg.).
|
|
* Recompute the initial retransmit timer.
|
|
*/
|
|
if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) {
|
|
tcpstat.tcps_rttupdated++;
|
|
if (tp->t_srtt != 0) {
|
|
register short delta;
|
|
|
|
/*
|
|
* srtt is stored as fixed point with 3 bits
|
|
* after the binary point (i.e., scaled by 8).
|
|
* The following magic is equivalent
|
|
* to the smoothing algorithm in rfc793
|
|
* with an alpha of .875
|
|
* (srtt = rtt/8 + srtt*7/8 in fixed point).
|
|
* Adjust t_rtt to origin 0.
|
|
*/
|
|
delta = tp->t_rtt - 1 - (tp->t_srtt >> 3);
|
|
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 + 2 times the smoothed variance.
|
|
* rttvar is stored as fixed point
|
|
* with 2 bits after the binary point
|
|
* (scaled by 4). The following is equivalent
|
|
* to rfc793 smoothing with an alpha of .75
|
|
* (rttvar = rttvar*3/4 + |delta| / 4).
|
|
* This replaces rfc793's wired-in beta.
|
|
*/
|
|
if (delta < 0)
|
|
delta = -delta;
|
|
delta -= (tp->t_rttvar >> 2);
|
|
if ((tp->t_rttvar += delta) <= 0)
|
|
tp->t_rttvar = 1;
|
|
} else {
|
|
/*
|
|
* No rtt measurement yet - use the
|
|
* unsmoothed rtt. Set the variance
|
|
* to half the rtt (so our first
|
|
* retransmit happens at 2*rtt)
|
|
*/
|
|
tp->t_srtt = tp->t_rtt << 3;
|
|
tp->t_rttvar = tp->t_rtt << 1;
|
|
}
|
|
tp->t_rtt = 0;
|
|
tp->t_rxtshift = 0;
|
|
TCPT_RANGESET(tp->t_rxtcur,
|
|
((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
|
|
TCPTV_MIN, TCPTV_REXMTMAX);
|
|
}
|
|
|
|
/*
|
|
* If all outstanding data is acked, stop retransmit
|
|
* timer and remember to restart (more output or persist).
|
|
* If there is more data to be acked, restart retransmit
|
|
* timer, using current (possibly backed-off) value.
|
|
*/
|
|
if (ti->ti_ack == tp->snd_max) {
|
|
tp->t_timer[TCPT_REXMT] = 0;
|
|
needoutput = 1;
|
|
} else if (tp->t_timer[TCPT_PERSIST] == 0)
|
|
tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
|
|
/*
|
|
* When new data is acked, open the congestion window.
|
|
* If the window gives us less than ssthresh packets
|
|
* in flight, open exponentially (maxseg per packet).
|
|
* Otherwise open linearly (maxseg per window,
|
|
* or maxseg^2 / cwnd per packet).
|
|
*/
|
|
{
|
|
u_int incr = tp->t_maxseg;
|
|
|
|
if (tp->snd_cwnd > tp->snd_ssthresh)
|
|
incr = MAX(incr * incr / tp->snd_cwnd, 1);
|
|
|
|
tp->snd_cwnd = MIN(tp->snd_cwnd + incr, IP_MAXPACKET); /* XXX */
|
|
}
|
|
if (acked > so->so_snd.sb_cc) {
|
|
tp->snd_wnd -= so->so_snd.sb_cc;
|
|
(void) sbdrop(&so->so_snd, (int)so->so_snd.sb_cc);
|
|
ourfinisacked = 1;
|
|
} else {
|
|
(void) sbdrop(&so->so_snd, acked);
|
|
tp->snd_wnd -= acked;
|
|
ourfinisacked = 0;
|
|
}
|
|
if ((so->so_snd.sb_flags & SB_WAIT) || so->so_snd.sb_sel ||
|
|
(so->so_state & SS_ASYNC))
|
|
sowwakeup(so);
|
|
tp->snd_una = ti->ti_ack;
|
|
if (SEQ_LT(tp->snd_nxt, tp->snd_una))
|
|
tp->snd_nxt = tp->snd_una;
|
|
|
|
switch (tp->t_state) {
|
|
|
|
/*
|
|
* In FIN_WAIT_1 STATE in addition to the processing
|
|
* for the ESTABLISHED state if our FIN is now acknowledged
|
|
* then enter FIN_WAIT_2.
|
|
*/
|
|
case TCPS_FIN_WAIT_1:
|
|
if (ourfinisacked) {
|
|
/*
|
|
* If we can't receive any more
|
|
* data, then closing user can proceed.
|
|
* Starting the timer is contrary to the
|
|
* specification, but if we don't get a FIN
|
|
* we'll hang forever.
|
|
*/
|
|
if (so->so_state & SS_CANTRCVMORE) {
|
|
soisdisconnected(so);
|
|
tp->t_timer[TCPT_2MSL] = tcp_maxidle;
|
|
}
|
|
tp->t_state = TCPS_FIN_WAIT_2;
|
|
}
|
|
break;
|
|
|
|
/*
|
|
* In CLOSING STATE in addition to the processing for
|
|
* the ESTABLISHED state if the ACK acknowledges our FIN
|
|
* then enter the TIME-WAIT state, otherwise ignore
|
|
* the segment.
|
|
*/
|
|
case TCPS_CLOSING:
|
|
if (ourfinisacked) {
|
|
tp->t_state = TCPS_TIME_WAIT;
|
|
tcp_canceltimers(tp);
|
|
tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
|
|
soisdisconnected(so);
|
|
}
|
|
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:
|
|
tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
|
|
goto dropafterack;
|
|
}
|
|
}
|
|
|
|
step6:
|
|
/*
|
|
* Update window information.
|
|
* Don't look at window if no ACK: TAC's send garbage on first SYN.
|
|
*/
|
|
if ((tiflags & TH_ACK) &&
|
|
(SEQ_LT(tp->snd_wl1, ti->ti_seq) || tp->snd_wl1 == ti->ti_seq &&
|
|
(SEQ_LT(tp->snd_wl2, ti->ti_ack) ||
|
|
tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd))) {
|
|
/* keep track of pure window updates */
|
|
if (ti->ti_len == 0 &&
|
|
tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd)
|
|
tcpstat.tcps_rcvwinupd++;
|
|
tp->snd_wnd = ti->ti_win;
|
|
tp->snd_wl1 = ti->ti_seq;
|
|
tp->snd_wl2 = ti->ti_ack;
|
|
if (tp->snd_wnd > tp->max_sndwnd)
|
|
tp->max_sndwnd = tp->snd_wnd;
|
|
needoutput = 1;
|
|
}
|
|
|
|
/*
|
|
* Process segments with URG.
|
|
*/
|
|
if ((tiflags & TH_URG) && ti->ti_urp &&
|
|
TCPS_HAVERCVDFIN(tp->t_state) == 0) {
|
|
/*
|
|
* This is a kludge, but if we receive and accept
|
|
* random urgent pointers, we'll crash in
|
|
* soreceive. It's hard to imagine someone
|
|
* actually wanting to send this much urgent data.
|
|
*/
|
|
if (ti->ti_urp + so->so_rcv.sb_cc > SB_MAX) {
|
|
ti->ti_urp = 0; /* XXX */
|
|
tiflags &= ~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.
|
|
*/
|
|
if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) {
|
|
tp->rcv_up = ti->ti_seq + ti->ti_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 (ti->ti_urp <= ti->ti_len &&
|
|
(so->so_options & SO_OOBINLINE) == 0)
|
|
tcp_pulloutofband(so, ti);
|
|
} 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 */
|
|
|
|
/*
|
|
* Process the segment text, merging it into the TCP sequencing queue,
|
|
* and arranging for acknowledgment of receipt if necessary.
|
|
* This process logically involves adjusting tp->rcv_wnd as data
|
|
* is presented to the user (this happens in tcp_usrreq.c,
|
|
* case PRU_RCVD). If a FIN has already been received on this
|
|
* connection then we just ignore the text.
|
|
*/
|
|
if ((ti->ti_len || (tiflags&TH_FIN)) &&
|
|
TCPS_HAVERCVDFIN(tp->t_state) == 0) {
|
|
TCP_REASS(tp, ti, m, so, tiflags);
|
|
if (tcp_nodelack == 0)
|
|
tp->t_flags |= TF_DELACK;
|
|
else
|
|
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);
|
|
if (len > tp->max_rcvd)
|
|
tp->max_rcvd = len;
|
|
} else {
|
|
m_freem(m);
|
|
tiflags &= ~TH_FIN;
|
|
}
|
|
|
|
/*
|
|
* If FIN is received ACK the FIN and let the user know
|
|
* that the connection is closing.
|
|
*/
|
|
if (tiflags & TH_FIN) {
|
|
if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
|
|
socantrcvmore(so);
|
|
tp->t_flags |= TF_ACKNOW;
|
|
tp->rcv_nxt++;
|
|
}
|
|
switch (tp->t_state) {
|
|
|
|
/*
|
|
* In SYN_RECEIVED and ESTABLISHED STATES
|
|
* enter the CLOSE_WAIT state.
|
|
*/
|
|
case TCPS_SYN_RECEIVED:
|
|
case TCPS_ESTABLISHED:
|
|
tp->t_state = TCPS_CLOSE_WAIT;
|
|
break;
|
|
|
|
/*
|
|
* If still in FIN_WAIT_1 STATE FIN has not been acked so
|
|
* enter the CLOSING state.
|
|
*/
|
|
case TCPS_FIN_WAIT_1:
|
|
tp->t_state = TCPS_CLOSING;
|
|
break;
|
|
|
|
/*
|
|
* In FIN_WAIT_2 state enter the TIME_WAIT state,
|
|
* starting the time-wait timer, turning off the other
|
|
* standard timers.
|
|
*/
|
|
case TCPS_FIN_WAIT_2:
|
|
tp->t_state = TCPS_TIME_WAIT;
|
|
tcp_canceltimers(tp);
|
|
tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
|
|
soisdisconnected(so);
|
|
break;
|
|
|
|
/*
|
|
* In TIME_WAIT state restart the 2 MSL time_wait timer.
|
|
*/
|
|
case TCPS_TIME_WAIT:
|
|
tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
|
|
break;
|
|
}
|
|
}
|
|
if (so->so_options & SO_DEBUG)
|
|
tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0);
|
|
|
|
/*
|
|
* Return any desired output.
|
|
*/
|
|
if (needoutput || (tp->t_flags & TF_ACKNOW))
|
|
(void) tcp_output(tp);
|
|
return;
|
|
|
|
dropafterack:
|
|
/*
|
|
* Generate an ACK dropping incoming segment if it occupies
|
|
* sequence space, where the ACK reflects our state.
|
|
*/
|
|
if (tiflags & TH_RST)
|
|
goto drop;
|
|
m_freem(m);
|
|
tp->t_flags |= TF_ACKNOW;
|
|
(void) tcp_output(tp);
|
|
return;
|
|
|
|
dropwithreset:
|
|
if (om) {
|
|
(void) m_free(om);
|
|
om = 0;
|
|
}
|
|
/*
|
|
* Generate a RST, dropping incoming segment.
|
|
* Make ACK acceptable to originator of segment.
|
|
* Don't bother to respond if destination was broadcast.
|
|
*/
|
|
if ((tiflags & TH_RST) || in_broadcast(ti->ti_dst))
|
|
goto drop;
|
|
if (tiflags & TH_ACK)
|
|
tcp_respond(tp, ti, (tcp_seq)0, ti->ti_ack, TH_RST);
|
|
else {
|
|
if (tiflags & TH_SYN)
|
|
ti->ti_len++;
|
|
tcp_respond(tp, ti, (tcp_seq)(ti->ti_seq+ti->ti_len), (tcp_seq)0,
|
|
TH_RST|TH_ACK);
|
|
}
|
|
/* destroy temporarily created socket */
|
|
if (dropsocket)
|
|
(void) soabort(so);
|
|
return;
|
|
|
|
drop:
|
|
if (om)
|
|
(void) m_free(om);
|
|
/*
|
|
* Drop space held by incoming segment and return.
|
|
*/
|
|
if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
|
|
tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0);
|
|
m_freem(m);
|
|
/* destroy temporarily created socket */
|
|
if (dropsocket)
|
|
(void) soabort(so);
|
|
return;
|
|
}
|
|
|
|
tcp_dooptions(tp, om, ti)
|
|
struct tcpcb *tp;
|
|
struct mbuf *om;
|
|
struct tcpiphdr *ti;
|
|
{
|
|
register u_char *cp;
|
|
int opt, optlen, cnt;
|
|
|
|
cp = mtod(om, u_char *);
|
|
cnt = om->m_len;
|
|
for (; cnt > 0; cnt -= optlen, cp += optlen) {
|
|
opt = cp[0];
|
|
if (opt == TCPOPT_EOL)
|
|
break;
|
|
if (opt == TCPOPT_NOP)
|
|
optlen = 1;
|
|
else {
|
|
optlen = cp[1];
|
|
if (optlen <= 0)
|
|
break;
|
|
}
|
|
switch (opt) {
|
|
|
|
default:
|
|
break;
|
|
|
|
case TCPOPT_MAXSEG:
|
|
if (optlen != 4)
|
|
continue;
|
|
if (!(ti->ti_flags & TH_SYN))
|
|
continue;
|
|
tp->t_maxseg = *(u_short *)(cp + 2);
|
|
tp->t_maxseg = MIN(ntohs((u_short)tp->t_maxseg),
|
|
tcp_mss(tp));
|
|
|
|
/*
|
|
* Cannot be zero; used as divisor later on
|
|
*/
|
|
if (tp->t_maxseg == 0)
|
|
tp->t_maxseg = tcp_default_mss;
|
|
break;
|
|
}
|
|
}
|
|
(void) m_free(om);
|
|
}
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
tcp_pulloutofband(so, ti)
|
|
struct socket *so;
|
|
struct tcpiphdr *ti;
|
|
{
|
|
register struct mbuf *m;
|
|
int cnt = ti->ti_urp - 1;
|
|
|
|
m = dtom(ti);
|
|
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--;
|
|
return;
|
|
}
|
|
cnt -= m->m_len;
|
|
m = m->m_next;
|
|
if (m == 0)
|
|
break;
|
|
}
|
|
panic("tcp_pulloutofband");
|
|
}
|
|
|
|
/*
|
|
* Determine a reasonable value for maxseg size.
|
|
* If the route is known, use one that can be handled
|
|
* on the given interface without forcing IP to fragment.
|
|
* If bigger than an mbuf cluster (MCLBYTES), round down to nearest size
|
|
* to utilize large mbufs.
|
|
* If interface pointer is unavailable, or the destination isn't local,
|
|
* use a conservative size (512 or the default IP max size, but no more
|
|
* than the mtu of the interface through which we route),
|
|
* 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; this information should
|
|
* probably all be saved with the routing entry at the transport level.
|
|
*
|
|
* This is ugly, and doesn't belong at this level, but has to happen somehow.
|
|
*/
|
|
tcp_mss(tp)
|
|
register struct tcpcb *tp;
|
|
{
|
|
struct route *ro;
|
|
struct ifnet *ifp;
|
|
int mss;
|
|
struct inpcb *inp;
|
|
|
|
inp = tp->t_inpcb;
|
|
ro = &inp->inp_route;
|
|
if ((ro->ro_rt == (struct rtentry *)0) ||
|
|
(ifp = ro->ro_rt->rt_ifp) == (struct ifnet *)0) {
|
|
/* No route yet, so try to acquire one */
|
|
if (inp->inp_faddr.s_addr != INADDR_ANY) {
|
|
ro->ro_dst.sa_family = AF_INET;
|
|
((struct sockaddr_in *) &ro->ro_dst)->sin_addr =
|
|
inp->inp_faddr;
|
|
rtalloc(ro);
|
|
}
|
|
if ((ro->ro_rt == 0) || (ifp = ro->ro_rt->rt_ifp) == 0)
|
|
return (tcp_default_mss);
|
|
}
|
|
|
|
mss = ifp->if_mtu - sizeof(struct tcpiphdr);
|
|
if (in_localaddr(inp->inp_faddr))
|
|
return (mss);
|
|
|
|
mss = MIN(mss, tcp_default_mss);
|
|
tp->snd_cwnd = mss;
|
|
return (mss);
|
|
}
|
|
|