On Di, 2015-01-13 at 09:53 +0530, Rahul Sharma wrote: > On Mon, Jan 12, 2015 at 5:21 PM, Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> wrote: > > On Mon, Jan 12, 2015 at 04:38:16PM +0530, Rahul Sharma wrote: > >> Hi Pablo, Hannes > >> > >> On Fri, Jan 9, 2015 at 9:20 PM, Hannes Frederic Sowa > >> <hannes@xxxxxxxxxxxxxxxxxxx> wrote: > >> > 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 > >> > > >> > > >> > >> I enabled pr_debug() and there was no error in nf_ct_frag6_gather(). > >> It seems to have defragmented the packet correctly. As expected, > >> ipv6_defrag() returns NF_STOLEN for the first packet after queuing it. > >> For the next fragment, ipv6_defrag() calls nf_ct_frag6_output() after > >> after reassembling it. > > > > nf_ct_frag6_output() doesn't exist anymore. You're using an old > > kernel, you should have started by telling so in your report. > > > > See 6aafeef ("netfilter: push reasm skb through instead of original > > frag skbs"). > > I apologize for not mentioning the kernel version in my first mail. I > had suspected problem in ipv6_find_hdr, the code for which was same. > Anyway, thanks for the help. I ll try to figure out how to make this > work in my kernel. If you have time could you quickly test a recent net-next kernel? 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