Wireshark · Wireshark-dev: Re: [Wireshark-dev] False positive from the new "Look for incomplete dissectors" function.

[Dario Lombardo <dario.lombardo.ml@xxxxxxxxx>]

Hi Anders

If you carefully have a look at the bytes, you can notice that the 2 bytes reported by the logs are claimed by the SIP dissector, but they're not decoded. 

Until SIP/2.0, bytes are decoded (address up to 0x0040+12). 

From "Max-Forward" and beyond (address 0x0040+15) they are decoded. 

Addresses 0x0040 +13 and +14 are not decoded. That's exactly what I would have expected. If you click on them, the entire "SIP - REGISTER" is highlighted.

It is related to the textual nature of sip... the 2 undecoded bytes are 0x0d0a (CR+NL). A char sequence that not only is allowed in sip, but AFAIK, can also be repeated multiple times. 

As told the algorithm is not perfect and I will have to take care of special cases like that. I will have a look at the sip dissector to understand how to threat those text protocols (maybe many others are around... like HTTP :)).

Thanks for having pointed it out.

On Thu, Feb 12, 2015 at 4:32 PM, Anders Broman <anders.broman@xxxxxxxxxxxx> wrote:

Hi,

The enclosed frame shows what I think is a false positive.

Regards

Anders

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