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Avoid deadlock situation described by Stevens using his suggested replacement

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code.

Obtained from: Stevens, vol. 2, pp. 959-960
This commit is contained in:
Garrett Wollman 1995-02-16 01:39:19 +00:00
parent 9bb8795d71
commit dac2030182
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=6480
2 changed files with 40 additions and 60 deletions
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50
sys/netinet/tcp_input.c
View File

@ -30,8 +30,8 @@
* 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
* $Id: tcp_input.c,v 1.13 1995/02/14 06:23:56 phk Exp $
* From: @(#)tcp_input.c 8.5 (Berkeley) 4/10/94
* $Id: tcp_input.c,v 1.14 1995/02/16 00:55:39 wollman Exp $
*/
#ifndef TUBA_INCLUDE
@ -935,36 +935,26 @@ tcp_input(m, iphlen)
tiflags &= ~TH_URG;
todrop--;
}
if (todrop >= ti->ti_len) {
tcpstat.tcps_rcvduppack++;
tcpstat.tcps_rcvdupbyte += ti->ti_len;
/*
* Following if statement from Stevens, vol. 2, p. 960.
*/
if (todrop > ti->ti_len
|| (todrop == ti->ti_len && (tiflags & TH_FIN) == 0)) {
/*
* 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.
* 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.
*/
if ((tiflags & TH_FIN && todrop == ti->ti_len + 1)
#ifdef TCP_COMPAT_42
|| (tiflags & TH_RST && ti->ti_seq == tp->rcv_nxt - 1)
#endif
) {
todrop = ti->ti_len;
tiflags &= ~TH_FIN;
tp->t_flags |= TF_ACKNOW;
} else {
/*
* Handle the case when a bound socket connects
* to itself. Allow packets with a SYN and
* an ACK to continue with the processing.
*/
if (todrop != 0 || (tiflags & TH_ACK) == 0)
goto dropafterack;
}
tiflags &= ~TH_FIN;
/*
* Send an ACK to resynchronize and drop any data.
* But keep on processing for RST or ACK.
*/
tp->t_flags |= TF_ACKNOW;
todrop = ti->ti_len;
tcpstat.tcps_rcvduppack++;
tcpstat.tcps_rcvdupbyte += todrop;
} else {
tcpstat.tcps_rcvpartduppack++;
tcpstat.tcps_rcvpartdupbyte += todrop;

50
sys/netinet/tcp_reass.c
View File

@ -30,8 +30,8 @@
* 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
* $Id: tcp_input.c,v 1.13 1995/02/14 06:23:56 phk Exp $
* From: @(#)tcp_input.c 8.5 (Berkeley) 4/10/94
* $Id: tcp_input.c,v 1.14 1995/02/16 00:55:39 wollman Exp $
*/
#ifndef TUBA_INCLUDE
@ -935,36 +935,26 @@ tcp_input(m, iphlen)
tiflags &= ~TH_URG;
todrop--;
}
if (todrop >= ti->ti_len) {
tcpstat.tcps_rcvduppack++;
tcpstat.tcps_rcvdupbyte += ti->ti_len;
/*
* Following if statement from Stevens, vol. 2, p. 960.
*/
if (todrop > ti->ti_len
|| (todrop == ti->ti_len && (tiflags & TH_FIN) == 0)) {
/*
* 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.
* 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.
*/
if ((tiflags & TH_FIN && todrop == ti->ti_len + 1)
#ifdef TCP_COMPAT_42
|| (tiflags & TH_RST && ti->ti_seq == tp->rcv_nxt - 1)
#endif
) {
todrop = ti->ti_len;
tiflags &= ~TH_FIN;
tp->t_flags |= TF_ACKNOW;
} else {
/*
* Handle the case when a bound socket connects
* to itself. Allow packets with a SYN and
* an ACK to continue with the processing.
*/
if (todrop != 0 || (tiflags & TH_ACK) == 0)
goto dropafterack;
}
tiflags &= ~TH_FIN;
/*
* Send an ACK to resynchronize and drop any data.
* But keep on processing for RST or ACK.
*/
tp->t_flags |= TF_ACKNOW;
todrop = ti->ti_len;
tcpstat.tcps_rcvduppack++;
tcpstat.tcps_rcvdupbyte += todrop;
} else {
tcpstat.tcps_rcvpartduppack++;
tcpstat.tcps_rcvpartdupbyte += todrop;