Re: [PATCH net-next 1/1] net/smc: add SMC rendezvous protocol

[David Miller <davem@davemloft.net>]

From: Florian Westphal <fw@strlen.de>
Date: Thu, 12 Oct 2017 13:14:29 +0200

> Ursula Braun <ubraun@linux.vnet.ibm.com> wrote:
>> On 10/11/2017 11:06 PM, David Miller wrote:
>> > From: Ursula Braun <ubraun@linux.vnet.ibm.com>
>> > Date: Tue, 10 Oct 2017 16:14:19 +0200
>> > 
>> >> The goal of this patch is to leave common TCP code unmodified. Thus,
>> >> it uses netfilter hooks to intercept TCP SYN and SYN/ACK
>> >> packets. For outgoing packets originating from SMC sockets, the
>> >> experimental option is added. For inbound packets destined for SMC
>> >> sockets, the experimental option is checked.
>> > 
>> > I think this really isn't going to pass.
>> > 
>> > It's a user experience nightmare when the kernel inserts and
>> > deletes filtering rules outside of what the user configures
>> > on their system.
> 
> It depends if the hook is passive or not (i.e. mangles
> payload/metadata or returns verdict other than NF_ACCEPT).
> 
> OUTPUT hook added here is not passive as it mangles tcp options.
> 
>> > This approach was also considerd for ipv6 ILA, and the same
>> > pushback was given.
> 
> ahem.
> net/ipv6/ila/ila_xlat.c:   err = nf_register_net_hooks(net, ila_nf_hook_ops,

My bad, I thought we had decided against that.

Oh well.