Hi,
I ran into an issue using libpcap and tcpdump.
Whenever I enter a filter tcpdump segfaults:
i.e.:
works fine :
#tcpdump
segfault
#tcpdump port 80
tcpdump included with fc4 works fine
(tcpdump version 3.8 libpcap version 0.8.3 )
However, I tried compiling
libpcap 0.8.3 0.9.4 -current (libpcap-2005.10.09)
tcpdump 3.8.3 3.9.4 -current (tcpdump-2005.10.09)
All those fail at the same place in optimize.c.
I added a bunch of checks for null pointers and managed to get
everything compiled and running.
Anyone else stumbled into this?
uname -a
Linux new_tornado 2.6.12-1.1456_FC4smp #1 SMP Thu Sep 22 02:22:14 EDT
2005 i686 athlon i386 GNU/Linux
gcc --version
gcc (GCC) 4.0.1 20050727 (Red Hat 4.0.1-5)
Copyright (C) 2005 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is
NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE.
Thanks for your time.
Attached is a patch to optimize.c against libpcap-current (2005.10.09).
Louis-Michel Gelinas
--- libpcap-2005.10.09/optimize.c 2005-07-31 13:58:24.000000000 -0400
+++ libpcap-2005.10.09.patched/optimize.c 2005-11-09 19:28:16.000000000 -0500
@@ -218,6 +218,7 @@
struct block *b;
{
int level;
+ if (!b) return ;
if (isMarked(b))
return;
@@ -228,6 +229,7 @@
if (JT(b)) {
find_levels_r(JT(b));
find_levels_r(JF(b));
+ if ( !b || !(b->level) || !JT(b) || !JF(b) ) { level =0 ; return;}
level = MAX(JT(b)->level, JF(b)->level) + 1;
} else
level = 0;
@@ -1771,7 +1773,7 @@
make_marks(p)
struct block *p;
{
- if (!isMarked(p)) {
+ if (p && !isMarked(p)) {
Mark(p);
if (BPF_CLASS(p->s.code) != BPF_RET) {
make_marks(JT(p));
@@ -1863,7 +1865,7 @@
done = 0;
JT(p) = JT(p)->link;
}
- if (JF(p)->link) {
+ if (JF(p) && JF(p)->link) {
done = 0;
JF(p) = JF(p)->link;
}
@@ -2202,7 +2204,9 @@
}
else
dst->jt = off;
- off = JF(p)->offset - (p->offset + slen) - 1;
+ if ( JF(p) ) {
+ off = JF(p)->offset - (p->offset + slen) - 1;
+ }
if (off >= 256) {
/* offset too large for branch, must add a jump */
if (p->longjf == 0) {
-
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