On Fr, 2015-01-09 at 12:45 +0100, Pablo Neira Ayuso wrote: > Hi Hannes, > > On Fri, Jan 09, 2015 at 12:34:15PM +0100, Hannes Frederic Sowa wrote: > > On Fri, Jan 9, 2015, at 08:18, Rahul Sharma wrote: > > > Hi Pablo, > > > > > > On Fri, Jan 9, 2015 at 5:35 AM, Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> > > > wrote: > > > > On Thu, Jan 08, 2015 at 11:39:16PM +0100, Hannes Frederic Sowa wrote: > > > >> Hi Pablo, > > > >> > > > >> On Thu, Jan 8, 2015, at 21:53, Pablo Neira Ayuso wrote: > > > >> > I'm afraid we cannot just get rid of that !ipv6_ext_hdr() check. The > > > >> > ipv6_find_hdr() function is designed to return the transport protocol. > > > >> > After the proposed change, it will return extension header numbers. > > > >> > This will break existing ip6tables rulesets since the `-p' option > > > >> > relies on this function to match the transport protocol. > > > >> > > > > >> > Note that the AH header is skipped (see code a bit below this > > > >> > problematic fragmentation handling) so the follow up header after the > > > >> > AH header is returned as the transport header. > > > >> > > > > >> > We can probably return the AH protocol number for non-1st fragments. > > > >> > However, that would be something new to ip6tables since nobody has > > > >> > ever seen packet matching `-p ah' rules. Thus, we restore control to > > > >> > the user to allow this, but we would accept all kind of fragmented AH > > > >> > traffic through the firewall since we cannot know what transport > > > >> > protocol contains from non-1st fragments (unless I'm missing anything, > > > >> > I need to have a closer look at this again tomorrow with fresher > > > >> > mind). > > > >> > > > >> The code in question is guarded by (_frag_off != 0), so we are > > > >> definitely processing a non-1st fragment currently. The -p match would > > > >> happen at the time when the packet is reassembled and thus ipv6_find_hdr > > > >> will find the real transport (final) header at this point (I hope I > > > >> followed the code correctly here). > > > > > > > > Then, Rahul should get things working by modprobing nf_defrag_ipv6. > > > > > > I already had nf_defrag_ipv6 installed when the issue occured. But I > > > see ip6table_raw_hook returning NF_DROP for the second fragment. > > > > That's what I expected. I think the change only affects hooks before > > reassembly. > > reassembly happens at NF_IP6_PRI_CONNTRACK_DEFRAG (-400), so that > happens before NF_IP6_PRI_RAW (-300) in IPv6 which is where the raw > table is placed. I tried to reproduce it, but couldn't get non-1st fragments getting dropped during traversal of the raw table. They get dropped earlier at during reassembly or pass. I agree with Pablo, I also would like to see more data. Thanks, Hannes -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
