tcp_output.c

嵌入式操作系统ECOS的网络开发包

//==========================================================================
//
//      sys/netinet/tcp_output.c
//
//     
//
//==========================================================================
//####BSDCOPYRIGHTBEGIN####
//
// -------------------------------------------
//
// Portions of this software may have been derived from OpenBSD or other sources,
// and are covered by the appropriate copyright disclaimers included herein.
//
// -------------------------------------------
//
//####BSDCOPYRIGHTEND####
//==========================================================================
//#####DESCRIPTIONBEGIN####
//
// Author(s):    gthomas
// Contributors: gthomas
// Date:         2000-01-10
// Purpose:      
// Description:  
//              
//
//####DESCRIPTIONEND####
//
//==========================================================================


/*	$OpenBSD: tcp_output.c,v 1.27 1999/12/15 16:37:20 provos Exp $	*/
/*	$NetBSD: tcp_output.c,v 1.16 1997/06/03 16:17:09 kml Exp $	*/

/*
 * Copyright (c) 1982, 1986, 1988, 1990, 1993
 *	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_output.c	8.3 (Berkeley) 12/30/93
 */

/*
%%% portions-copyright-nrl-95
Portions of this software are Copyright 1995-1998 by Randall Atkinson,
Ronald Lee, Daniel McDonald, Bao Phan, and Chris Winters. All Rights
Reserved. All rights under this copyright have been assigned to the US
Naval Research Laboratory (NRL). The NRL Copyright Notice and License
Agreement Version 1.1 (January 17, 1995) applies to these portions of the
software.
You should have received a copy of the license with this software. If you
didn't get a copy, you may request one from <[e-mail]>.
*/

#include <sys/param.h>
#ifndef __ECOS
#include <sys/systm.h>
#endif
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/errno.h>
#include <sys/domain.h>

#include <net/route.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/in_pcb.h>
#include <netinet/ip_var.h>
#include <netinet/tcp.h>
#define	TCPOUTFLAGS
#include <netinet/tcp_fsm.h>
#include <netinet/tcp_seq.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#include <netinet/tcpip.h>
#include <netinet/tcp_debug.h>

#ifdef TUBA
#include <netiso/iso.h>
#include <netiso/tuba_table.h>
#endif

#ifdef INET6
#include <netinet6/tcpipv6.h>
#endif /* INET6 */

#ifdef TCP_SIGNATURE
#include <sys/md5k.h>
#endif /* TCP_SIGNATURE */

#ifdef notyet
extern struct mbuf *m_copypack();
#endif

#ifdef TCP_SACK
extern int tcprexmtthresh;
#endif

#ifdef TCP_SACK
#ifdef TCP_SACK_DEBUG
void
tcp_print_holes(tp)
struct tcpcb *tp;
{
	struct sackhole *p = tp->snd_holes;
	if (p == 0)
		return;
	printf("Hole report: start--end dups rxmit\n");
	while (p) {
		printf("%x--%x d %d r %x\n",  p->start, p->end, p->dups,
                    p->rxmit);
		p = p->next;
	}
	printf("\n");
}
#endif /* TCP_SACK_DEBUG */

/*
 * Returns pointer to a sackhole if there are any pending retransmissions;
 * NULL otherwise.
 */
struct sackhole *
tcp_sack_output(tp)
register struct tcpcb *tp;
{
	struct sackhole *p;
	if (tp->sack_disable)
		return 0;
	p = tp->snd_holes;
	while (p) {
		if (p->dups >= tcprexmtthresh && SEQ_LT(p->rxmit, p->end)) {
			if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */
				p = p->next;
				continue;
			}
#ifdef TCP_SACK_DEBUG
			if (p)
				tcp_print_holes(tp);
#endif
			return p;
		}
        	p = p->next;
	}
	return 0;
}

/*
 * After a timeout, the SACK list may be rebuilt.  This SACK information
 * should be used to avoid retransmitting SACKed data.  This function
 * traverses the SACK list to see if snd_nxt should be moved forward.
 */
void
tcp_sack_adjust(tp)
	struct tcpcb *tp;
{
	int i;

	for (i = 0; i < tp->rcv_numsacks; i++) {
		if (SEQ_LT(tp->snd_nxt, tp->sackblks[i].start))
			break;
		if (SEQ_LEQ(tp->sackblks[i].end, tp->snd_nxt))
			continue;
		if (tp->sackblks[i].start == 0 && tp->sackblks[i].end == 0)
			continue;
		/* snd_nxt must be in middle of block of SACKed data */
		tp->snd_nxt = tp->sackblks[i].end;
		break;
	}
}
#endif /* TCP_SACK */

/*
 * Tcp output routine: figure out what should be sent and send it.
 */
int
tcp_output(tp)
	register struct tcpcb *tp;
{
	register struct socket *so = tp->t_inpcb->inp_socket;
	register long len, win;
	int off, flags, error = 0;
	register struct mbuf *m;
	register struct tcphdr *th;
	u_char opt[MAX_TCPOPTLEN];
	unsigned int optlen, hdrlen;
	int idle, sendalot;
#ifdef TCP_SACK
	int i, sack_rxmit = 0;
	struct sackhole *p;
#endif
#if defined(TCP_SACK) || defined(TCP_NEWRENO)
	int maxburst = TCP_MAXBURST;
#endif
#ifdef TCP_SIGNATURE
	unsigned int sigoff;
#endif /* TCP_SIGNATURE */

#if defined(TCP_SACK) && defined(TCP_SIGNATURE) && defined(DIAGNOSTIC)
	if (!tp->sack_disable && (tp->t_flags & TF_SIGNATURE))
		return (EINVAL);
#endif /* defined(TCP_SACK) && defined(TCP_SIGNATURE) && defined(DIAGNOSTIC) */

	/*
	 * Determine length of data that should be transmitted,
	 * and flags that will be used.
	 * If there is some data or critical controls (SYN, RST)
	 * to send, then transmit; otherwise, investigate further.
	 */
	idle = (tp->snd_max == tp->snd_una);
	if (idle && tp->t_idle >= tp->t_rxtcur)
		/*
		 * We have been idle for "a while" and no acks are
		 * expected to clock out any data we send --
		 * slow start to get ack "clock" running again.
		 */
		tp->snd_cwnd = tp->t_maxseg;
again:
	sendalot = 0;
#ifdef TCP_SACK
	/*
	 * If we've recently taken a timeout, snd_max will be greater than
	 * snd_nxt.  There may be SACK information that allows us to avoid
	 * resending already delivered data.  Adjust snd_nxt accordingly.
	 */
	if (!tp->sack_disable && SEQ_LT(tp->snd_nxt, tp->snd_max))
		tcp_sack_adjust(tp);
#endif
	off = tp->snd_nxt - tp->snd_una;
	win = ulmin(tp->snd_wnd, tp->snd_cwnd);

	flags = tcp_outflags[tp->t_state];
	/*
	 * If in persist timeout with window of 0, send 1 byte.
	 * Otherwise, if window is small but nonzero
	 * and timer expired, we will send what we can
	 * and go to transmit state.
	 */

#ifdef TCP_SACK
	/* 
	 * Send any SACK-generated retransmissions.  If we're explicitly trying
	 * to send out new data (when sendalot is 1), bypass this function.
	 * If we retransmit in fast recovery mode, decrement snd_cwnd, since
	 * we're replacing a (future) new transmission with a retransmission 
	 * now, and we previously incremented snd_cwnd in tcp_input().
	 */
	if (!tp->sack_disable && !sendalot) {
		if ((p = tcp_sack_output(tp))) {
			off = p->rxmit - tp->snd_una;
			sack_rxmit = 1;
#if 0
			/* Coalesce holes into a single retransmission */
#endif
			len = min(tp->t_maxseg, p->end - p->rxmit);
#ifndef TCP_FACK
			/* in FACK, hold snd_cwnd constant during recovery */
			if (SEQ_LT(tp->snd_una, tp->snd_last))
				tp->snd_cwnd -= tp->t_maxseg;
#endif
    		}
	}
#endif /* TCP_SACK */

	if (tp->t_force) {
		if (win == 0) {
			/*
			 * If we still have some data to send, then
			 * clear the FIN bit.  Usually this would
			 * happen below when it realizes that we
			 * aren't sending all the data.  However,
			 * if we have exactly 1 byte of unset data,
			 * then it won't clear the FIN bit below,
			 * and if we are in persist state, we wind
			 * up sending the packet without recording
			 * that we sent the FIN bit.
			 *
			 * We can't just blindly clear the FIN bit,
			 * because if we don't have any more data
			 * to send then the probe will be the FIN
			 * itself.
			 */
			if (off < so->so_snd.sb_cc)
				flags &= ~TH_FIN;
			win = 1;
		} else {
			tp->t_timer[TCPT_PERSIST] = 0;
			tp->t_rxtshift = 0;
		}
	}

#ifdef TCP_SACK
	if (!sack_rxmit) {
#endif
	len = ulmin(so->so_snd.sb_cc, win) - off;

#if defined(TCP_SACK) && defined(TCP_FACK)
	/* 
	 * If we're in fast recovery (SEQ_GT(tp->snd_last, tp->snd_una)), and 
	 * amount of outstanding data (snd_awnd) is >= snd_cwnd, then
	 * do not send data (like zero window conditions)
	 */
	if (!tp->sack_disable && len && SEQ_GT(tp->snd_last, tp->snd_una) && 
	    (tp->snd_awnd >= tp->snd_cwnd)) 
		len = 0;
#endif /* TCP_FACK */
#ifdef TCP_SACK
	}
#endif

	if (len < 0) {
		/*
		 * If FIN has been sent but not acked,
		 * but we haven't been called to retransmit,
		 * len will be -1.  Otherwise, window shrank
		 * after we sent into it.  If window shrank to 0,
		 * cancel pending retransmit and pull snd_nxt
		 * back to (closed) window.  We will enter persist
		 * state below.  If the window didn't close completely,
		 * just wait for an ACK.
		 */
		len = 0;
		if (win == 0) {
			tp->t_timer[TCPT_REXMT] = 0;
			tp->snd_nxt = tp->snd_una;
		}
	}
	if (len > tp->t_maxseg) {
		len = tp->t_maxseg;
		sendalot = 1;
	}
	if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc))
		flags &= ~TH_FIN;

	win = sbspace(&so->so_rcv);

	/*
	 * Sender silly window avoidance.  If connection is idle
	 * and can send all data, a maximum segment,
	 * at least a maximum default-size segment do it,
	 * or are forced, do it; otherwise don't bother.
	 * If peer's buffer is tiny, then send
	 * when window is at least half open.
	 * If retransmitting (possibly after persist timer forced us