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If a segment is received with RST set and the segment is completely to the

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left of the receive window, ignore it.  Add some additional comments to
the code that deals with received segemnts that are completely to the right
of the receive window.  If an invalid SYN is received, force an ACK and
drop it; if the other side really sent the SYN; it'll respond with a reset.
This commit is contained in:
matt 2004-04-17 23:35:37 +00:00
parent 66a6704d83
commit 35b9f3ec72
1 changed files with 23 additions and 13 deletions
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36
sys/netinet/tcp_input.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: tcp_input.c,v 1.192 2004/04/14 18:07:52 ragge Exp $ */
/* $NetBSD: tcp_input.c,v 1.193 2004/04/17 23:35:37 matt Exp $ */
/*
* Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@ -148,7 +148,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: tcp_input.c,v 1.192 2004/04/14 18:07:52 ragge Exp $");
__KERNEL_RCSID(0, "$NetBSD: tcp_input.c,v 1.193 2004/04/17 23:35:37 matt Exp $");
#include "opt_inet.h"
#include "opt_ipsec.h"
@ -1766,11 +1766,13 @@ after_listen:
if (todrop > tlen ||
(todrop == tlen && (tiflags & 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.
* Any valid FIN or RST must be to the left of the
* window. At this point the FIN or RST must be a
* duplicate or out of sequence; drop it.
*/
tiflags &= ~TH_FIN;
if (tiflags & TH_RST)
goto drop;
tiflags &= ~(TH_FIN|TH_RST);
/*
* Send an ACK to resynchronize and drop any data.
* But keep on processing for RST or ACK.
@ -1813,6 +1815,12 @@ after_listen:
if (todrop > 0) {
tcpstat.tcps_rcvpackafterwin++;
if (todrop >= tlen) {
/*
* The segment actually starts after the window.
* th->th_seq + tlen - tp->rcv_nxt - tp->rcv_wnd >= tlen
* th->th_seq - tp->rcv_nxt - tp->rcv_wnd >= 0
* th->th_seq >= tp->rcv_nxt + tp->rcv_wnd
*/
tcpstat.tcps_rcvbyteafterwin += tlen;
/*
* If a new connection request is received
@ -1840,7 +1848,7 @@ after_listen:
* window edge, and have to drop data and PUSH from
* incoming segments. Continue processing, but
* remember to ack. Otherwise, drop segment
* and ack.
* and (if not RST) ack.
*/
if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
tp->t_flags |= TF_ACKNOW;
@ -1901,13 +1909,15 @@ after_listen:
}
/*
* If a SYN is in the window, then this is an
* error and we send an RST and drop the connection.
* Since we've covered the SYN-SENT and SYN-RECEIVED states above
* we must be in a synchronized state. RFC791 states (under RST
* generation) that any unacceptable segment (an out-of-order SYN
* qualifies) received in a synchronized state must elicit only an
* empty acknowledgment segment ... and the connection remains in
* the same state.
*/
if (tiflags & TH_SYN) {
tp = tcp_drop(tp, ECONNRESET);
goto dropwithreset;
}
if (tiflags & TH_SYN)
goto dropafterack;
/*
* If the ACK bit is off we drop the segment and return.