Re: Ethernet header below MPLS...

[barcaroller <barcaroller () gmail com>]

On 2016-09-16 12:32:26 +0000, Francesco Fondelli said:

> If the Ethernet PW is without the CW (Control Word) - as it seems from
> your ASCII art - the "magic" might be happened in
> dissect_pw_eth_heuristic() around line 134 of packet-pw-eth.c.
>
> To get the big picture (line 462 of packet-mpls.c + line 134 of
> packet-pw-eth.c):
>
> - is there any user specific label binding for this label (via decode
> as)? yes use it, else
> - use the 1st nibble logic (see BCP 4928, RFC 4385 and 5586): 4 =>
> IPv4, 6 => IPv6, 1 => PW Associated Channel (i.e. OAM stuff like
> S-BFD, BFD, LM, CC, CV...)
> - if the first nibble is 0 well... wiiild guessss... we try with a bit
> of "magic" (at line 134 of packet-pw-eth.c)
>      - if the first 6+6 bytes look like (by checking manufacture OUI
> database) a pair of Ethernet addresses we go with Ethernet PW
> *without* CW (it seems your case)
>      - else hmmm wait... the first nibble was 0 so it might have been
> the case of Ethernet PW with a 'Generic PW MPLS Control Word' as per
> RFC 4385 (uncommon)
>
> Isn't Wireshark great? :-)
>
> ciao
> fra

Thanks for your detailed response, Francesco!  It answered my question.


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