netdev - Re: bridge: Do not compile options in br_parse_ip

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Message-ID: <20141004180647.GB1241@breakpoint.cc>
Date:	Sat, 4 Oct 2014 20:06:47 +0200
From:	Florian Westphal <fw@...len.de>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Florian Westphal <fw@...len.de>, netfilter-devel@...r.kernel.org,
	bsd@...hat.com, stephen@...workplumber.org, netdev@...r.kernel.org,
	eric.dumazet@...il.com, davidn@...idnewall.com,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: bridge: Do not compile options in br_parse_ip_options

Herbert Xu <herbert@...dor.apana.org.au> wrote:
> On Sat, Oct 04, 2014 at 09:55:08PM +0800, Herbert Xu wrote:
> >
> > I'll try to create a patch that essentially reverts the patch
> > that led us here.
> 
> Here is a patch that's only compile-tested:
> 
> bridge: Do not compile options in br_parse_ip_options
> 
> Commit 462fb2af9788a82a534f8184abfde31574e1cfa0
> 
> 	bridge : Sanitize skb before it enters the IP stack
> 
> broke when IP options are actually used because it mangles the
> skb as if it entered the IP stack which is wrong because the
> bridge is supposed to operate below the IP stack.
> 
> Since nobody has actually requested for parsing of IP options
> this patch fixes it by simply reverting to the previous approach
> of ignoring all IP options, i.e., zeroing the IPCB.

Fair enough.  We lose frag_max_size information from ipv4 defrag,
plus netfilter hooks are called without validating ip options.

The former has not worked ever with bridge, and the latter
evidentily isn't a problem either since this has not worked at all
for three years...

So I am fine with it, provided we rename br_parse_ip_options() --
thats not what it does after this patch (br_validate_iphdr(), for
example?)

> If and when somebody who uses IP options and actually needs them
> to be parsed by the bridge complains then we can revisit this.

Ok, fair enough.

Thanks Herbert.
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