tcpdump mailing list archives

Re: vlan [xx] filter not filtering any packets


From: Michael Richardson <mcr () sandelman ottawa on ca>
Date: Mon, 08 Jun 2009 12:08:09 -0400


"Nikola" == Nikola Ciprich <extmaillist () linuxbox cz> writes:
    Nikola> Hello,

    Nikola> I've spent some time playing with tcpdump and pcap with
    Nikola> regard to vlans. Using libpcap 1.0.0 + tcpdump 4.0.0, I can
    Nikola> able to correctly dump packets including (reconstructed)
    Nikola> vlan headers. But it seems that using the vlan filter
    Nikola> keyword does not work.

    Nikola> example: $ tcpdump -e -i eth1 13:10:05.592027
    Nikola> 00:30:48:92:f6:73 (oui Unknown) > 00:30:48:64:40:9d (oui
    Nikola> Unknown), ethertype 802.1Q (0x8100), length 102: vlan 10, p
    Nikola> 0, ethertype IPv4, 10.0.10.1 > 10.0.10.2: ICMP echo request,
    Nikola> id 27941, seq 12466, length 64

    Nikola> which is OK. But

  Can you capture the data to a .pcap file, and reproduce it with -r?
  If so, then a test case could be added.

  I suspect that the vlan filter may not work if there is further SNAP
headers, but that's just top of my head idea..

-- 
]     Y'avait une poule de jammé dans l'muffler!!!!!!!!!        |  firewalls  [
]   Michael Richardson, Sandelman Software Works, Ottawa, ON    |net architect[
] mcr () sandelman ottawa on ca http://www.sandelman.ottawa.on.ca/ |device driver[
]    h("Just another Debian GNU/Linux using, kernel hacking,    ruby  guy");  [

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