From: Patrick McHardy <kaber@trash.net>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Kernel Netdev Mailing List <netdev@vger.kernel.org>
Subject: Re: [XFRM]: Improve MTU estimation
Date: Fri, 04 Aug 2006 13:11:19 +0200 [thread overview]
Message-ID: <44D32B57.2000304@trash.net> (raw)
In-Reply-To: <20060804101345.GA17583@gondor.apana.org.au>
Herbert Xu wrote:
> On Fri, Aug 04, 2006 at 12:09:18PM +0200, Patrick McHardy wrote:
>
>>I was wondering why the old code distinguished between transport mode
>>and tunnel mode, I couldn't spot anything that would be affected. I'll
>>look into the transport mode case again.
>
>
> The problem is basically you don't know a priori the size of the IP
> options. So you assume the worst case where the IP options causes
> the largest amount of padding for encryption (IP option length itself
> must be a multiple of 4, so for a block size of 8 the worst is 4,
> and the worst is 12 for a block size of 16).
>
> Of course it gets hairier if you have ESP padding. I'm not even sure
> if the current code gets that right.
Unless I'm missing something, the padding caused by IP options
is always less than the worst case that can happen anyway
(max(block size, padlen)-1), so it can simply be ignored.
next prev parent reply other threads:[~2006-08-04 11:13 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-08-04 8:50 [XFRM]: Improve MTU estimation Patrick McHardy
2006-08-04 9:27 ` Patrick McHardy
2006-08-04 10:01 ` Herbert Xu
2006-08-04 10:09 ` Patrick McHardy
2006-08-04 10:13 ` Herbert Xu
2006-08-04 11:11 ` Patrick McHardy [this message]
2006-08-04 11:16 ` Herbert Xu
2006-08-04 11:21 ` Patrick McHardy
2006-08-04 11:25 ` Herbert Xu
2006-08-04 11:50 ` Patrick McHardy
2006-08-04 11:51 ` Patrick McHardy
2006-08-04 11:55 ` Herbert Xu
2006-08-04 11:54 ` Herbert Xu
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