Wireshark · Ethereal-dev: Re: [Ethereal-dev] reassembling TCP even if checksums are incorrect

[Guy Harris <gharris@xxxxxxxxx>]

LEGO wrote:
> I have some captures made on a sun in which TCP checksums are
> incorrect for every packet (They are probably calculated after they
> are passed to snoop, the service works OK so on the wire I assume
> those are correct).

Yes, this is

	http://www.ethereal.com/faq#q5.14

Ultimately, what would be nice would be to

	1) get, from the capture mechanism, an indication of what packets are 
being sent by the machine

and

	2) get, from the interface enumeration mechanism, an indication of 
whether the interface does checksum offloading

and turn off the checksum check on outgoing packets on those interfaces.

> The TCP dissector does not reassemble
> [Unreassembled Packet [incorrect TCP checksum]: GIOP]
>
> Is it OK if we add a prefererence to TCP so it can ignore checksums
> when reassembling in that condition?

There's already a preference to turn off checksum checking, which is 
useful if you're capturing traffic to and from a machine with checksum 
offloading.