Wireshark-dev: Re: [Wireshark-dev] dissection of packets with unknown format (LDP/MPLS/PWE)
From: "Francesco Fondelli" <[email protected]>
Date: Tue, 13 May 2008 13:59:50 +0200
On Mon, Apr 28, 2008 at 3:13 AM, Alexandre Abreu <[email protected]> wrote:
> Hi.
>  Has anyone ever found a case where the successful dissection of one
>  protocol depends on what was negotiated in another protocol? I've been

to be honest it should work anyway (PW + ethernet):

    while (there are labels) {
           if (bos)

    next_tvb = tvb_new_subset(tvb, offset, -1, -1);

    ipvers = (tvb_get_guint8(tvb, offset) >> 4) & 0x0F;
    if (ipvers == 6) {
      call_dissector(ipv6_handle, next_tvb, pinfo, tree);
    } else if (ipvers == 4) {
      call_dissector(ipv4_handle, next_tvb, pinfo, tree);
    } else if (ipvers == 1) {
      dissect_mpls_control(next_tvb, pinfo, tree);
    } else {
      call_dissector(eth_withoutfcs_handle, next_tvb, pinfo, tree);

if you got control word after PW label and you transport ethernet (nibble 0000)
dissect_mpls_control() should call call_dissector(eth_withoutfcs_handle...).
If you don't have control word you take the else path. If this is not
the case there is a bug.

could you please send a pcap file? I can work on it.

A "Decode this PW as...[eth/TDM/etc]" option was on my wish-list... because you
cannot relay on catching LDP signalling (it might be absent or on a different
physical wire/fiber).

>  Tks in advance

you are welcome

>  AA