Module Name: src
Committed By: uwe
Date: Mon May 7 23:42:13 UTC 2018
Modified Files:
src/sys/netinet: tcp_output.c
Log Message:
Fix unsigned wraparound on window size calculations.
This is another instance where tp->rcv_adv - tp->rcv_nxt can wrap
around after successful zero-window probe from the peer. The first
one was fixed by chs@ in revision 1.112 on 2004-05-08.
While here, CSE and de-obfuscate the code a bit.
To generate a diff of this commit:
cvs rdiff -u -r1.206 -r1.207 src/sys/netinet/tcp_output.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/netinet/tcp_output.c
diff -u src/sys/netinet/tcp_output.c:1.206 src/sys/netinet/tcp_output.c:1.207
--- src/sys/netinet/tcp_output.c:1.206 Thu May 3 07:13:48 2018
+++ src/sys/netinet/tcp_output.c Mon May 7 23:42:13 2018
@@ -1,4 +1,4 @@
-/* $NetBSD: tcp_output.c,v 1.206 2018/05/03 07:13:48 maxv Exp $ */
+/* $NetBSD: tcp_output.c,v 1.207 2018/05/07 23:42:13 uwe Exp $ */
/*
* Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@@ -135,7 +135,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: tcp_output.c,v 1.206 2018/05/03 07:13:48 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: tcp_output.c,v 1.207 2018/05/07 23:42:13 uwe Exp $");
#ifdef _KERNEL_OPT
#include "opt_inet.h"
@@ -987,16 +987,27 @@ again:
* taking into account that we are limited by
* TCP_MAXWIN << tp->rcv_scale.
*/
- long adv = min(win, (long)TCP_MAXWIN << tp->rcv_scale) -
- (tp->rcv_adv - tp->rcv_nxt);
+ long recwin = min(win, (long)TCP_MAXWIN << tp->rcv_scale);
+ long oldwin, adv;
/*
- * If the new window size ends up being the same as the old
- * size when it is scaled, then don't force a window update.
+ * rcv_nxt may overtake rcv_adv when we accept a
+ * zero-window probe.
*/
- if ((tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale ==
- (adv + tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale)
+ if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt))
+ oldwin = tp->rcv_adv - tp->rcv_nxt;
+ else
+ oldwin = 0;
+
+ /*
+ * If the new window size ends up being the same as or
+ * less than the old size when it is scaled, then
+ * don't force a window update.
+ */
+ if (recwin >> tp->rcv_scale <= oldwin >> tp->rcv_scale)
goto dontupdate;
+
+ adv = recwin - oldwin;
if (adv >= (long) (2 * rxsegsize))
goto send;
if (2 * adv >= (long) so->so_rcv.sb_hiwat)
