Re: [PATCH] net/ipv6/exthdrs.c et al: Optional strict PadN optionchecking

[David Miller]

From: Eldad Zack <eldad@xxxxxxxxxxxxxxx>
Date: Sat,  7 Apr 2012 17:16:14 +0200

> Added strict checking of PadN. PadN can be used to increase header
> size and thus push the protocol header into the 2nd fragment.
> 
> PadN is used to align the options within the Hop-by-Hop or
> Destination Options header to 64-bit boundaries. The maximum valid
> size is thus 7 bytes.
> RFC 4942 recommends to actively check the "payload" itself and
> ensure that it contains only zeroes.
> 
> See also RFC 4942 section 2.1.9.5.
> 
> Signed-off-by: Eldad Zack <eldad@xxxxxxxxxxxxxxx>

I think you should do away with the sysctl and always perform these
checks.

At the very leat, the optlen > 7 check should always be performed.
And frankly the pad byte being zero check makes sense to do all the
time as far as I can tell too.
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