tcp_input.c

qemu虚拟机代码

/*
 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)tcp_input.c	8.5 (Berkeley) 4/10/94
 * tcp_input.c,v 1.10 1994/10/13 18:36:32 wollman Exp
 */

/*
 * Changes and additions relating to SLiRP
 * Copyright (c) 1995 Danny Gasparovski.
 * 
 * Please read the file COPYRIGHT for the 
 * terms and conditions of the copyright.
 */

#include <slirp.h>
#include "ip_icmp.h"

struct socket tcb;

int	tcprexmtthresh = 3;
struct	socket *tcp_last_so = &tcb;

tcp_seq tcp_iss;                /* tcp initial send seq # */

#define TCP_PAWS_IDLE	(24 * 24 * 60 * 60 * PR_SLOWHZ)

/* for modulo comparisons of timestamps */
#define TSTMP_LT(a,b)	((int)((a)-(b)) < 0)
#define TSTMP_GEQ(a,b)	((int)((a)-(b)) >= 0)

/*
 * Insert segment ti into reassembly queue of tcp with
 * control block tp.  Return TH_FIN if reassembly now includes
 * a segment with FIN.  The macro form does 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).
 */
#ifdef TCP_ACK_HACK
#define TCP_REASS(tp, ti, m, so, flags) {\
       if ((ti)->ti_seq == (tp)->rcv_nxt && \
           (tp)->seg_next == (tcpiphdrp_32)(tp) && \
           (tp)->t_state == TCPS_ESTABLISHED) {\
               if (ti->ti_flags & TH_PUSH) \
                       tp->t_flags |= TF_ACKNOW; \
               else \
                       tp->t_flags |= TF_DELACK; \
               (tp)->rcv_nxt += (ti)->ti_len; \
               flags = (ti)->ti_flags & TH_FIN; \
               tcpstat.tcps_rcvpack++;\
               tcpstat.tcps_rcvbyte += (ti)->ti_len;\
               if (so->so_emu) { \
		       if (tcp_emu((so),(m))) sbappend((so), (m)); \
	       } else \
	       	       sbappend((so), (m)); \
/*               sorwakeup(so); */ \
	} else {\
               (flags) = tcp_reass((tp), (ti), (m)); \
               tp->t_flags |= TF_ACKNOW; \
       } \
}
#else
#define	TCP_REASS(tp, ti, m, so, flags) { \
	if ((ti)->ti_seq == (tp)->rcv_nxt && \
	    (tp)->seg_next == (tcpiphdrp_32)(tp) && \
	    (tp)->t_state == TCPS_ESTABLISHED) { \
		tp->t_flags |= TF_DELACK; \
		(tp)->rcv_nxt += (ti)->ti_len; \
		flags = (ti)->ti_flags & TH_FIN; \
		tcpstat.tcps_rcvpack++;\
		tcpstat.tcps_rcvbyte += (ti)->ti_len;\
		if (so->so_emu) { \
			if (tcp_emu((so),(m))) sbappend(so, (m)); \
		} else \
			sbappend((so), (m)); \
/*		sorwakeup(so); */ \
	} else { \
		(flags) = tcp_reass((tp), (ti), (m)); \
		tp->t_flags |= TF_ACKNOW; \
	} \
}
#endif

int
tcp_reass(tp, ti, m)
	register struct tcpcb *tp;
	register struct tcpiphdr *ti;
	struct mbuf *m;
{
	register struct tcpiphdr *q;
	struct socket *so = tp->t_socket;
	int flags;
	
	/*
	 * Call with ti==0 after become established to
	 * force pre-ESTABLISHED data up to user socket.
	 */
	if (ti == 0)
		goto present;

	/*
	 * Find a segment which begins after this one does.
	 */
	for (q = (struct tcpiphdr *)tp->seg_next; q != (struct tcpiphdr *)tp;
	    q = (struct tcpiphdr *)q->ti_next)
		if (SEQ_GT(q->ti_seq, ti->ti_seq))
			break;

	/*
	 * If there is a preceding segment, it may provide some of
	 * our data already.  If so, drop the data from the incoming
	 * segment.  If it provides all of our data, drop us.
	 */
	if ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) {
		register int i;
		q = (struct tcpiphdr *)q->ti_prev;
		/* conversion to int (in i) handles seq wraparound */
		i = q->ti_seq + q->ti_len - ti->ti_seq;
		if (i > 0) {
			if (i >= ti->ti_len) {
				tcpstat.tcps_rcvduppack++;
				tcpstat.tcps_rcvdupbyte += ti->ti_len;
				m_freem(m);
				/*
				 * Try to present any queued data
				 * at the left window edge to the user.
				 * This is needed after the 3-WHS
				 * completes.
				 */
				goto present;   /* ??? */
			}
			m_adj(m, i);
			ti->ti_len -= i;
			ti->ti_seq += i;
		}
		q = (struct tcpiphdr *)(q->ti_next);
	}
	tcpstat.tcps_rcvoopack++;
	tcpstat.tcps_rcvoobyte += ti->ti_len;
	REASS_MBUF(ti) = (mbufp_32) m;		/* XXX */

	/*
	 * While we overlap succeeding segments trim them or,
	 * if they are completely covered, dequeue them.
	 */
	while (q != (struct tcpiphdr *)tp) {
		register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq;
		if (i <= 0)
			break;
		if (i < q->ti_len) {
			q->ti_seq += i;
			q->ti_len -= i;
			m_adj((struct mbuf *) REASS_MBUF(q), i);
			break;
		}
		q = (struct tcpiphdr *)q->ti_next;
		m = (struct mbuf *) REASS_MBUF((struct tcpiphdr *)q->ti_prev);
		remque_32((void *)(q->ti_prev));
		m_freem(m);
	}

	/*
	 * Stick new segment in its place.
	 */
	insque_32(ti, (void *)(q->ti_prev));

present:
	/*
	 * Present data to user, advancing rcv_nxt through
	 * completed sequence space.
	 */
	if (!TCPS_HAVEESTABLISHED(tp->t_state))
		return (0);
	ti = (struct tcpiphdr *) tp->seg_next;
	if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt)
		return (0);
	if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len)
		return (0);
	do {
		tp->rcv_nxt += ti->ti_len;
		flags = ti->ti_flags & TH_FIN;
		remque_32(ti);
		m = (struct mbuf *) REASS_MBUF(ti); /* XXX */
		ti = (struct tcpiphdr *)ti->ti_next;
/*		if (so->so_state & SS_FCANTRCVMORE) */
		if (so->so_state & SS_FCANTSENDMORE)
			m_freem(m);
		else {
			if (so->so_emu) {
				if (tcp_emu(so,m)) sbappend(so, m);
			} else
				sbappend(so, m);
		}
	} while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt);
/*	sorwakeup(so); */
	return (flags);
}

/*
 * TCP input routine, follows pages 65-76 of the
 * protocol specification dated September, 1981 very closely.
 */
void
tcp_input(m, iphlen, inso)
	register struct mbuf *m;
	int iphlen;
	struct socket *inso;
{
  	struct ip save_ip, *ip;
	register struct tcpiphdr *ti;
	caddr_t optp = NULL;
	int optlen = 0;
	int len, tlen, off;
	register struct tcpcb *tp = 0;
	register int tiflags;
	struct socket *so = 0;
	int todrop, acked, ourfinisacked, needoutput = 0;
/*	int dropsocket = 0; */
	int iss = 0;
	u_long tiwin;
	int ret;
/*	int ts_present = 0; */

	DEBUG_CALL("tcp_input");
	DEBUG_ARGS((dfd," m = %8lx  iphlen = %2d  inso = %lx\n", 
		    (long )m, iphlen, (long )inso ));
	
	/*
	 * If called with m == 0, then we're continuing the connect
	 */
	if (m == NULL) {
		so = inso;
		
		/* Re-set a few variables */
		tp = sototcpcb(so);
		m = so->so_m;
		so->so_m = 0;
		ti = so->so_ti;
		tiwin = ti->ti_win;
		tiflags = ti->ti_flags;
		
		goto cont_conn;
	}
	
	
	tcpstat.tcps_rcvtotal++;
	/*
	 * Get IP and TCP header together in first mbuf.
	 * Note: IP leaves IP header in first mbuf.
	 */
	ti = mtod(m, struct tcpiphdr *);
	if (iphlen > sizeof(struct ip )) {
	  ip_stripoptions(m, (struct mbuf *)0);
	  iphlen=sizeof(struct ip );
	}
	/* XXX Check if too short */
	

	/*
	 * Save a copy of the IP header in case we want restore it
	 * for sending an ICMP error message in response.
	 */
	ip=mtod(m, struct ip *);
	save_ip = *ip; 
	save_ip.ip_len+= iphlen;

	/*
	 * Checksum extended TCP header and data.
	 */
	tlen = ((struct ip *)ti)->ip_len;
	ti->ti_next = ti->ti_prev = 0;
	ti->ti_x1 = 0;
	ti->ti_len = htons((u_int16_t)tlen);
	len = sizeof(struct ip ) + tlen;
	/* keep checksum for ICMP reply
	 * ti->ti_sum = cksum(m, len); 
	 * if (ti->ti_sum) { */
	if(cksum(m, len)) {
	  tcpstat.tcps_rcvbadsum++;
	  goto drop;
	}

	/*
	 * Check that TCP offset makes sense,
	 * pull out TCP options and adjust length.		XXX
	 */
	off = ti->ti_off << 2;
	if (off < sizeof (struct tcphdr) || off > tlen) {
	  tcpstat.tcps_rcvbadoff++;
	  goto drop;
	}
	tlen -= off;
	ti->ti_len = tlen;
	if (off > sizeof (struct tcphdr)) {
	  optlen = off - sizeof (struct tcphdr);
	  optp = mtod(m, caddr_t) + sizeof (struct tcpiphdr);

		/* 
		 * Do quick retrieval of timestamp options ("options
		 * prediction?").  If timestamp is the only option and it's
		 * formatted as recommended in RFC 1323 appendix A, we
		 * quickly get the values now and not bother calling
		 * tcp_dooptions(), etc.
		 */
/*		if ((optlen == TCPOLEN_TSTAMP_APPA ||
 *		     (optlen > TCPOLEN_TSTAMP_APPA &&
 *			optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) &&
 *		     *(u_int32_t *)optp == htonl(TCPOPT_TSTAMP_HDR) &&
 *		     (ti->ti_flags & TH_SYN) == 0) {
 *			ts_present = 1;
 *			ts_val = ntohl(*(u_int32_t *)(optp + 4));
 *			ts_ecr = ntohl(*(u_int32_t *)(optp + 8));
 *			optp = NULL;   / * we've parsed the options * /
 *		}
 */
	}
	tiflags = ti->ti_flags;
	
	/*
	 * Convert TCP protocol specific fields to host format.
	 */
	NTOHL(ti->ti_seq);
	NTOHL(ti->ti_ack);
	NTOHS(ti->ti_win);
	NTOHS(ti->ti_urp);

	/*
	 * Drop TCP, IP headers and TCP options.
	 */
	m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
	m->m_len  -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
	
	/*
	 * Locate pcb for segment.
	 */
findso:
	so = tcp_last_so;
	if (so->so_fport != ti->ti_dport ||
	    so->so_lport != ti->ti_sport ||
	    so->so_laddr.s_addr != ti->ti_src.s_addr ||
	    so->so_faddr.s_addr != ti->ti_dst.s_addr) {
		so = solookup(&tcb, ti->ti_src, ti->ti_sport,
			       ti->ti_dst, ti->ti_dport);
		if (so)
			tcp_last_so = so;
		++tcpstat.tcps_socachemiss;
	}

	/*
	 * 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.
	 *
	 * state == CLOSED means we've done socreate() but haven't
	 * attached it to a protocol yet... 
	 * 
	 * XXX If a TCB does not exist, and the TH_SYN flag is
	 * the only flag set, then create a session, mark it
	 * as if it was LISTENING, and continue...
	 */
	if (so == 0) {
	  if ((tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) != TH_SYN)
	    goto dropwithreset;
		
	  if ((so = socreate()) == NULL)
	    goto dropwithreset;
	  if (tcp_attach(so) < 0) {
	    free(so); /* Not sofree (if it failed, it's not insqued) */
	    goto dropwithreset;
	  }
		
	  sbreserve(&so->so_snd, tcp_sndspace);
	  sbreserve(&so->so_rcv, tcp_rcvspace);
	  
	  /*		tcp_last_so = so; */  /* XXX ? */
	  /*		tp = sototcpcb(so);    */
		
	  so->so_laddr = ti->ti_src;
	  so->so_lport = ti->ti_sport;
	  so->so_faddr = ti->ti_dst;
	  so->so_fport = ti->ti_dport;
		
	  if ((so->so_iptos = tcp_tos(so)) == 0)
	    so->so_iptos = ((struct ip *)ti)->ip_tos;
		
	  tp = sototcpcb(so);
	  tp->t_state = TCPS_LISTEN;
	}
           
        /*
         * If this is a still-connecting socket, this probably
         * a retransmit of the SYN.  Whether it's a retransmit SYN
	 * or something else, we nuke it.
         */
        if (so->so_state & SS_ISFCONNECTING)
                goto drop;

	tp = sototcpcb(so);