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Re: DAQ and libpcap 1.1.1 vs 1.0.0
From: Russ Combs <rcombs () sourcefire com>
Date: Mon, 8 Nov 2010 14:59:48 -0500

Did you enable debug on your DAQ build (-g -O0)?

I don't have --disable-remote (or anything "remote") with libpcap-1.1.1.

On Mon, Nov 8, 2010 at 2:55 PM, Russ Combs <rcombs () sourcefire com> wrote:



On Mon, Nov 8, 2010 at 12:35 PM, <vincent () cojot name> wrote:


Hi Russ,

On my RHEL5.5 system, the following CFLAGS are passed to libpcap's
configure:

+ CFLAGS='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions
-fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic'
+ ./configure --prefix=/usr/libpcap1 --enable-ipv6 --without-libnl

I recompiled without --disable-remote and ran gdb on snort.
Running gdb on this build wasn't very informative:


Did you build the DAQ with debug support (-g -O0)?


(gdb) set args -i eth0
(gdb) r
Starting program: /usr/sbin/snort-plain -i eth0
[Thread debugging using libthread_db enabled]
Running in packet dump mode

       --== Initializing Snort ==--
Initializing Output Plugins!
pcap DAQ configured to passive.
Acquiring network traffic from "eth0".

Program received signal SIGSEGV, Segmentation fault.
0x000000000049feec in pcap_daq_start ()
(gdb) bt
#0  0x000000000049feec in pcap_daq_start ()
#1  0x0000000000438624 in DAQ_Start () at ../../src/sfdaq.c:414
#2  0x0000000000424bda in SnortMain (argc=3, argv=0x7fffffffe7e8) at
../../src/snort.c:712
#3  0x0000003536e1d994 in __libc_start_main () from /lib64/libc.so.6
#4  0x0000000000404359 in _start ()
(gdb) b DAQ_Start
Breakpoint 1 at 0x438610: file ../../src/sfdaq.c, line 414.
(gdb) r
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Starting program: /usr/sbin/snort-plain -i eth0
[Thread debugging using libthread_db enabled]
Running in packet dump mode

       --== Initializing Snort ==--
Initializing Output Plugins!
pcap DAQ configured to passive.
Acquiring network traffic from "eth0".

Breakpoint 1, DAQ_Start () at ../../src/sfdaq.c:414
414         int err = daq_start(daq_mod, daq_hand);
(gdb) s
413     {
(gdb) s
414         int err = daq_start(daq_mod, daq_hand);
(gdb) s

Program received signal SIGSEGV, Segmentation fault.
0x000000000049feec in pcap_daq_start ()
(gdb) what daq_mod
type = const DAQ_Module_t *
(gdb) what daq_hand
type = void *
(gdb) display daq_hand
1: daq_hand = (void *) 0x156c9c0
(gdb) display daq_mod
2: daq_mod = (const DAQ_Module_t *) 0x4e6000

And in the syslod, I got:
snort[24390]: segfault at 0000000000000010 rip 000000000049feec rsp
00007fff03cf30f0 error 4

Perhaps there's a security feature kicking in?


On Mon, 8 Nov 2010, vincent () cojot name wrote:


Hi Russ,

On Mon, 8 Nov 2010, Russ Combs wrote:

 I don't seem to have a --disable-remote for my libpcap 1.1.1 configure.

What exactly does that do?


# ./configure --help|grep remot
 --disable-remote        disable remote capture capabilities


Don't have this in my libpcap-1.1.1.



That's all I know. I don't know yet why it causes daq to crash snort when
that support is compiled in. libpcap-1.0.0 didn't have these 'remote
capture' features (I think).

 I'm glad you've got a workaround but would like to figure out what the
issue is and fix the DAQ if needed.


Yes, so would I. Now that I got the binary distribution 'stabilized'
enough, I can spend more time trying to figure out why it crashes under
RHEL5.5 when 'remote capture' is enabled inside libpcap 1.1.1.

Regards,

Vincent



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