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Re: DAQ and libpcap 1.1.1 vs 1.0.0
From: vincent () cojot name
Date: Tue, 9 Nov 2010 10:50:49 +0100 (CET)

On Mon, 8 Nov 2010, Russ Combs wrote:

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

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

Hi Russ,

You are right. The libpcap I was passed by a trustable 3rd-party was a modified 1.1.1 with remote packet capture (http://www.liberouter.org/nific/usecases/rpcap/rpcap.php). I'm reverting to standard libpcap and will push new rpms really soon.

Thank you,

Vincent

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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