netdev - Re: Improved handling of IPv6 atomic fragments (FO=0, MF=0)

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Message-ID: <1327920477.2288.28.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC>
Date:	Mon, 30 Jan 2012 11:47:57 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Fernando Gont <fernando@...t.com.ar>
Cc:	security@...nel.org, netdev <netdev@...r.kernel.org>
Subject: Re: Improved handling of IPv6 atomic fragments (FO=0, MF=0)

Le lundi 30 janvier 2012 à 07:24 -0300, Fernando Gont a écrit :
> Folks,
> 
> FYI. We have published an IETF I-D that proposes an improved handling of
> IPv6 atomic fragments (IPv6 fragments that have an offset of 0, and MF=0).
> 
> The I-D is available here:
> <http://tools.ietf.org/id/draft-gont-6man-ipv6-atomic-fragments-00.txt>
> 
> The aforementioned behaviour eliminates fragmentation-based attacks
> against traffic that employs atomic fragments, and has already been
> implemented by OpenBSD.
> 
> Thanks,

Unless I missed something, linux already does that.

ipv6_frag_rcv()

        if (!(fhdr->frag_off & htons(0xFFF9))) {
                /* It is not a fragmented frame */
                skb->transport_header += sizeof(struct frag_hdr);
                IP6_INC_STATS_BH(net,
                                 ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMOKS);

                IP6CB(skb)->nhoff = (u8 *)fhdr - skb_network_header(skb);
                return 1;
        }



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