Wireshark · Ethereal-users: Re: [Ethereal-users] ethereal 0.10.12 + synclink / lapd / isis

[Guy Harris <gharris@xxxxxxxxx>]

clay wispell wrote:

> i am capturing and decoding data from an agilent omniber captured from a 
> microgate synclink card. packet-lapd.c has been modified so that the 
> incoming data is decoded as lapd (native cisco-hdlc on layer 2)

So what's the *actual* link-layer format on the wire?  Is it really 
LAPD, or is it Cisco HDLC, or is it something else?

> and so 
> that any information packets are decoded based on the nlpid of the 
> packet. clnp and esis work well (nlpid 0x81 and 0x82), however, isis 
> (nlpid 0x83) causes a segmentation fault. it appears that the culprit is 
> a null value returned here in packet-lapd.c
>
>    isis_handle = find_dissector("isis");

The ISIS dissector doesn't register itself by name, so the 
"find_dissector()" call fails.

If you want to dissect the packet based on the NLPID, you should 
probably make "dissect_osi()" (in packet-osi.c) register itself by name, 
and call *that* dissector, so that it'll do all the work for you 
(handling not only ISIS, but CLNP and ESIS).