From: Bart De Schuymer <bdschuym@pandora•be>
To: Florian Westphal <fw@strlen•de>, David Newall <davidn@davidnewall•com>
Cc: Stephen Hemminger <stephen@networkplumber•org>,
Netdev <netdev@vger•kernel.org>,
bridge@lists•linux-foundation.org,
netfilter-devel@vger•kernel.org
Subject: Re: Revert 462fb2af9788a82a534f8184abfde31574e1cfa0 (bridge : Sanitize skb before it enters the IP stack)
Date: Mon, 19 May 2014 22:49:32 +0200 [thread overview]
Message-ID: <537A6E5C.6090602@pandora.be> (raw)
In-Reply-To: <20140519170915.GB24523@breakpoint.cc>
Florian Westphal schreef op 19/05/2014 19:09:
> David Newall <davidn@davidnewall•com> wrote:
>
> [ remove lkml and cc nf-devel ]
>
>> I tried to persevere with the commit: I recalculated checksum, which
>> left routes and times improperly updated in options. Then I tried
>> calling ip_forward_options, which looks like it would correctly
>> update RR and TS (not to mention checksum)m but that bombed because
>> skb_rtable returned NULL.
>
> Yes. bridge<->netfilter wiring is pure duct tape.
> The glue code will set up a fake rtable for the skb after the
> prerouting hook. [ see br_nf_pre_routing_finish() ].
>
>> I see three ways to progress:
>>
>> 1. Possibly call ip_forward_option, but that requires somebody who
>> understands this code to help;
>> 2. Just recalculate the checksum, leaving crap in the options; or
>> 3. Revert the commit.
>
> I think none of these are an option.
>
> I fail to understand why a bridge should honor/modifiy IP options.
>
> For the 'local delivery' case the ip stack will take care of
> option parsing, for forwarding it should be sufficient to do
> sanity tests (for netfilters sake).
>
>>From a quick glance, it should be sufficient to edit
> br_parse_ip_options() and remove everything after
>
> memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
>
> A 2nd step would be to move a copy of ip_options_compile()
> into br_netfilter.c and trim it down to only validate the
> ipv4 header without modifying it.
Perhaps it's possible to call ip_options_compile with a skb == NULL,
like ip_options.c::ip_options_get_finish does. That way we don't need to
duplicate code.
An alternative would be to make sure that the data pointed to by IPCB
and BR_INPUT_SKB_CB don't overlap. If this were the case, we could
indeed just revert the commit that was referred to.
cheers,
Bart
next prev parent reply other threads:[~2014-05-19 20:49 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-11 14:41 Bad checksum on bridge with IP options David Newall
2014-05-11 19:42 ` Lukas Tribus
2014-05-12 8:14 ` David Newall
2014-05-12 10:15 ` Lukas Tribus
2014-05-12 10:25 ` David Newall
2014-05-12 10:31 ` Lukas Tribus
2014-05-12 10:48 ` David Newall
2014-05-12 13:23 ` David Newall
2014-05-12 13:51 ` Florian Westphal
2014-05-12 14:19 ` David Newall
2014-05-12 18:54 ` Lukas Tribus
2014-05-12 23:46 ` David Newall
2014-05-14 13:08 ` David Newall
2014-05-16 14:33 ` Revert 462fb2af9788a82a534f8184abfde31574e1cfa0 (bridge : Sanitize skb before it enters the IP stack) David Newall
2014-05-16 15:19 ` Eric Dumazet
2014-05-16 15:23 ` David Newall
2014-05-16 15:24 ` David Newall
2014-05-19 12:58 ` David Newall
2014-05-19 14:01 ` Florian Westphal
2014-05-19 14:19 ` David Newall
2014-05-19 17:09 ` Florian Westphal
2014-05-19 20:49 ` Bart De Schuymer [this message]
2014-05-21 7:49 ` David Newall
2014-05-21 18:51 ` Bart De Schuymer
2014-05-21 20:18 ` David Miller
2014-05-22 18:57 ` Bart De Schuymer
2014-05-24 18:00 ` David Miller
2014-05-24 5:56 ` David Newall
2014-05-24 17:43 ` David Miller
2014-05-25 2:32 ` David Newall
2014-05-25 3:02 ` David Miller
2014-05-25 6:37 ` David Newall
2014-05-27 8:55 ` David Laight
2014-05-29 22:34 ` David Miller
2014-05-30 9:17 ` David Newall
2014-05-31 0:46 ` David Miller
2014-05-31 6:13 ` David Newall
2014-05-31 6:37 ` David Miller
2014-05-22 3:50 ` David Newall
2014-05-22 18:57 ` Bart De Schuymer
2014-05-20 3:57 ` David Newall
2014-05-20 4:55 ` Valdis.Kletnieks
2014-05-20 16:05 ` Vlad Yasevich
2014-05-21 8:10 ` David Newall
2014-05-21 20:14 ` David Miller
2014-05-22 20:06 ` Bandan Das
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