Ethereal-dev: [Ethereal-dev] Re: (usagi-users 02308) Incorrect UDP checksum when using router

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From: YOSHIFUJI Hideaki / 吉藤英明 <yoshfuji@xxxxxxxxxxxxxx>
Date: Tue, 15 Apr 2003 22:32:16 +0900 (JST)
In article <3E9C0EFB.8020308@xxxxxxxxxxxxxx> (at Tue, 15 Apr 2003 15:54:04 +0200), Yaniv Kaul <ykaul@xxxxxxxxxxxxxx> says:

> I'm sending UDP packets from 3ffe:0:c0a8:979:290:27ff:febd:6ba9 to 
> 3ffe:0:a09:c901:2e0:18ff:fe22:391f via 
> 3ffe:0:c0a8:9c9:2a0:8eff:fe0c:2e1, using router header option.
> It seems that the UDP checksum, when going out from the client is 
> incorrect, at least according to Ethereal. They are correct on the 
> server, therefore I think the checksum calc is done prior to taking into 
> account the routing.

If the checksum is ok at the final receiver, it is fine.
(checksum does not change while traveling.)
It seems ethereal (or tchdump) does not calculate checksum
properly.

-- 
Hideaki YOSHIFUJI @ USAGI Project <yoshfuji@xxxxxxxxxxxxxx>
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