[Snort-devel] [PATCHES] Fixes for daq_nfq

Russ Combs rcombs at ...402...
Tue Mar 22 20:47:05 EDT 2011


OK - what version of pcap are you using?

On Tue, Mar 22, 2011 at 8:42 PM, Kelvie Wong <kwong at ...3121...> wrote:

> Hey Russ,
>
> On March 22, 2011 04:51:49 PM Russ Combs wrote:
> > Are you using the latest Snort?  The NFQ DAQ was recently changed to
> return
> > the IP4 or IP6 flavor instead of RAW because Snort determines the layer 3
> > protocol from the layer 2 header, and in this case there is no layer 2
> > header.  Returning IP4 or IP6 allows Snort to work with either.
> >
> >
> Yeah, I'm using Snort 2.9.0.4; I think the main problem is that this value
> is
> being handed over to libpcap, in the pcap_open_dead line.  If you feed it
> DLT_IPV4, it will set its link layer type to -1, as it does not recognize
> it.
>
>
> >     if (!ScTestMode())
> >     {
> >         pcap_t* pcap = pcap_open_dead(DAQ_GetBaseProtocol(),
> > DAQ_GetSnapLen()); data->dumpd = pcap ? pcap_dump_open(pcap,
> data->logdir)
> > : NULL;
> >
> >         if(data->dumpd == NULL)
> >         {
> >             FatalError("log_tcpdump: Failed to open log file \"%s\":
> %s\n",
> >                        data->logdir, pcap_geterr(pcap));
> >         }
> >         pcap_close(pcap);
> >     }
> >
> >  pcap_open_dead is being called with DAQ_GetBaseProtocol, which takes the
> > value from nfq_daq_get_datalink_type.
> >
> >  The problem is that nfq_daq_get_datalink_type now returns DLT_IPV4 or
> > DLT_IPV6 instead of DLT_RAW (as it did in 0.2). According to the pcap
> > manpage (http://www.tcpdump.org/pcap3_man.html) it supports neither of
> > those values.
> >
>
>
> This causes the error when pcap_dump_open is called, as this error message
> shows (it's a pcap error message).
>
> >  ERROR: log_tcpdump: Failed to open log file
> > "/var/log/snort/snort.log.1300810527":
> > /var/log/snort/snort.log.1300810527: link-layer type -1 isn't supported
> in
> > savefiles
>
> --
> Kelvie Wong
> Software Developer
>
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