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List:       opensolaris-laptop-discuss
Subject:    Re: [laptop-discuss] Incorrect Checksums on pcwl0
From:       "Garrett D'Amore" <gdamore () opensolaris ! org>
Date:       2008-09-30 18:47:54
Message-ID: 48E2745A.1030602 () opensolaris ! org
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steve wrote:
> Jürgen Keil wrote:
>   
>>> I'm using an Avaya PCMCIA NIC on my laptop with the pcwl driver.
>>>
>>> When I observe network traffic using WireShark 1.0.1, it shows all of my 
>>> TCP and UDP packets have incorrect checksums with a message stating:
>>>
>>> maybe caused by "TCP checksum offload?"
>>> &
>>> maybe caused by "UDP checksum offload?"
>>>       
>> On which machine is wireshark running ?
>> On the laptop with the PCMCIA NIC / pcwl driver ?
>>
>> In this case it is the expected behavior that outgoing
>> packets don't have valid udp and tcp checksums,
>> if the nic is using hardware checksum support.
>>
>> If you run the packet trace software on a different
>> machine, the checksums should be ok for packets
>> transmitted by the pcwl driver.
>> --
>> This message posted from opensolaris.org
>> _______________________________________________
>> laptop-discuss mailing list
>> laptop-discuss@opensolaris.org
>>     
>
> First of all, I appreciate the assistance.
>
> My laptop has the pcwl driver
> The machine out in the garage has the malo driver
>
> Running wireshark on both machines and initiating an ssh session shows 
> that both NICs are sending and receiving packets with bad checksums.
>
> I ran the test again without putting the cards in promiscuous mode - no 
> diff.
>
> ....
>
> Well, there ya go. I just tested it with tcpdump and all checksums are 
> now showing up as correct. Who's right? My money's on tcpdump.
>
> So it appears WireShark has a glitch. Does this sound right?
>   

Possibly.

I guarantee you that checksum offload is not at fault here-- pcwl 
*cannot* do any checksum offload.

    -- Garrett
> Thanks for your help,
> Cheers,
> Steve
>
> _______________________________________________
> laptop-discuss mailing list
> laptop-discuss@opensolaris.org
>   

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