Re: Any way to automatically change arbitrary headers of IP packets on-the-fly?

[email protected] Thu, 14 Apr 2005 01:23:31 -0400

Newsgroups	gmane.comp.security.linux,gmane.comp.security.penetration,gmane.comp.security.vulnerabilities,gmane.comp.security.libnet,gmane.comp.security.basics
Message-ID	<[email protected]>

On Mon, 11 Apr 2005 19:39:25 -0300, =?ISO-8859-1?Q?Jo=E3o_Paulo_Caldas_Campello?= said:

>    I've already read Netfilter documentation (specially the "Linux
> netfilter Hacking HOWTO") so I know this kind of packet mangling can
> be done in userspace. I thought it could be done in the "MANGLE" table
> of netfilter, but I found no TARGET that achieves that nor any
> documentation about altering arbitrary IP headers.

Currently, iptables doesn't seem to support that, probably to keep you from
shooting yourself in the foot.  Consider for example how fast the kernel will
fold up if you change that first nybble of the packet from an x'4' to an x'6'
without changing the rest of the packet to match.  Suddenly, that sk_buff is
a lot too short.. ;)

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