Wireshark-dev: [Wireshark-dev] GTP extension headers for TPDU
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From: Rayne <hjazz6@xxxxxxxxx>
Date: Wed, 10 Jun 2009 19:36:37 -0700 (PDT)
Hi, 

I noticed that in the GTP dissector, when the GTP message is a TPDU (GTPv1), and the "Next Extension Header" bit (and/or the S and/or PN bit) is set, the offset is set to 11, which points to the "Next Extension Header Type" field. If this field has a value of 0, then the offset is increased by one, and we move on to check if the next layer is IPv4, IPv6 or PPP. 

My understanding is that if the "Next Extension Header Type" field value is 0, then either the S or PN bit is set to 1, so increasing the offset by 1 allows us to move past the "Next Extension Header Type" field to the next IP/PPP header, since there are no extension headers.

What happens if the "Next Extension Header Type" field value is not 0? The offset is still at 11, which still points to the "Next Extension Header Type" field. There doesn't seem to be any mechanism to deal with these extension headers.

Thank you.

Regards,
Rayne