[src/trunk]: src/sys/net/npf If we're trying to read the mss on a packet that...

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/cf88237b4780
branches:  trunk
changeset: 321800:cf88237b4780
user:      maxv <maxv%NetBSD.org@localhost>
date:      Fri Apr 06 14:50:55 2018 +0000

description:
If we're trying to read the mss on a packet that for some reason has two
MAXSEG options, we find ourselves patching the second option with the
value of the first one.

Fix that by using a local variable.

diffstat:

 sys/net/npf/npf_inet.c |  12 +++++++++---
 1 files changed, 9 insertions(+), 3 deletions(-)

diffs (47 lines):

diff -r 868e88a7e5c8 -r cf88237b4780 sys/net/npf/npf_inet.c
--- a/sys/net/npf/npf_inet.c    Fri Apr 06 10:48:44 2018 +0000
+++ b/sys/net/npf/npf_inet.c    Fri Apr 06 14:50:55 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: npf_inet.c,v 1.47 2018/03/23 08:28:54 maxv Exp $       */
+/*     $NetBSD: npf_inet.c,v 1.48 2018/04/06 14:50:55 maxv Exp $       */
 
 /*-
  * Copyright (c) 2009-2014 The NetBSD Foundation, Inc.
@@ -40,7 +40,7 @@
 
 #ifdef _KERNEL
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: npf_inet.c,v 1.47 2018/03/23 08:28:54 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: npf_inet.c,v 1.48 2018/04/06 14:50:55 maxv Exp $");
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -230,6 +230,7 @@
        nbuf_t *nbuf = npc->npc_nbuf;
        const struct tcphdr *th = npc->npc_l4.tcp;
        int topts_len, step;
+       bool setmss = false;
        uint8_t *nptr;
        uint8_t val;
        bool ok;
@@ -245,6 +246,11 @@
        }
        KASSERT(topts_len <= MAX_TCPOPTLEN);
 
+       /* Determine if we want to set or get the mss. */
+       if (mss) {
+               setmss = (*mss != 0);
+       }
+
        /* First step: IP and TCP header up to options. */
        step = npc->npc_hlen + sizeof(struct tcphdr);
        nbuf_reset(nbuf);
@@ -270,7 +276,7 @@
                        goto done;
                }
                if (mss) {
-                       if (*mss) {
+                       if (setmss) {
                                memcpy(nptr + 2, mss, sizeof(uint16_t));
                        } else {
                                memcpy(mss, nptr + 2, sizeof(uint16_t));