netdev - Re: [PATCH nf-next 0/4] netfilter: rework netfilter ipv6 defrag

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Message-ID: <CANr6G5zvmj_tL5Pt6-70GQ4dTJXLewX9A4uMGC_0OFzXYQVdew@mail.gmail.com>
Date:	Mon, 19 Oct 2015 23:16:33 -0700
From:	Joe Stringer <joestringer@...ira.com>
To:	Florian Westphal <fw@...len.de>
Cc:	netfilter-devel@...r.kernel.org,
	Linux Netdev List <netdev@...r.kernel.org>,
	Andy Zhou <azhou@...ira.com>
Subject: Re: [PATCH nf-next 0/4] netfilter: rework netfilter ipv6 defrag

On 17 October 2015 at 13:14, Florian Westphal <fw@...len.de> wrote:
> [ CC netdev since patch #2 isn't nf-specific.  Dave, if you want
>   I can resubmit that one after the next nf-pull request; let me know if
>   you would prefer that ].
>
> Openvswitch seems broken wrt. to defragmentation, it doesn't call
> nf_ct_frag6_consume_orig to free the original fragments.

This will need to be fixed for 'net' as well, do you have a path in
mind for that?

> Moreover, openvswitch design seems to require that it can reuse current
> skb rather than work with a new skb pointer (it uses skb_morph for this).
>
> Instead of OVS-side fix this series tries to alter netfilter ipv6 defrag
> accordingly.
>
> 1. nf_ct_frag6_consume_orig is removed, since
> commit 6aafeef03b9d9ecf ("netfilter: push reasm skb through instead of
> original frag skbs") nothing needs the original fragments so there is no
> reason why we need to clone+store original skb -- just stash original
> skbs in the frag_list.
>
> 2. Use skb_morph to make the last skb processed (not necessarily last
> fragment) the reassembled one.
>
> 3. remove the no-longer needed recursion into nf_iterate, we can now just
> return ACCEPT/STOLEN as needed instead of NF_HOOK_THRESH()+NF_STOLEN.
>
> Tested with flood-ping6+ fault-injection framework 'failslab' type.

Overall, I like it in that it seems to make the IPv6 code more
consistent with IPv4, and it's a net negative LoC, simplifying the
code.

Patch 3 when taken independently from patch 4 hides user-visible error
codes on the OVS side. The OVS conntrack action hides -EINPROGRESS
from userspace, treating it as a successful execution. All other
errors are returned up. With that patch, all errors will be hidden. I
see that it's fixed in Patch 4, so maybe it's not a biggie but those
two patches should be tightly coupled.
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