netdev - Re: [PATCH 1/1] net: Add SO_REUSEPORT_LISTEN

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Date:	Wed, 23 Mar 2016 22:10:06 -0700
From:	Tolga Ceylan <tolga.ceylan@...il.com>
To:	Willy Tarreau <w@....eu>
Cc:	Tom Herbert <tom@...bertland.com>,
	Eric Dumazet <eric.dumazet@...il.com>, cgallek@...gle.com,
	Josh Snyder <josh@...e406.com>,
	Aaron Conole <aconole@...heb.org>,
	"David S. Miller" <davem@...emloft.net>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH 1/1] net: Add SO_REUSEPORT_LISTEN_OFF socket option as
 drain mode

On Mon, Dec 21, 2015 at 12:41 PM, Willy Tarreau <w@....eu> wrote:
> On Mon, Dec 21, 2015 at 12:38:27PM -0800, Tom Herbert wrote:
>> On Fri, Dec 18, 2015 at 11:00 PM, Willy Tarreau <w@....eu> wrote:
>> > On Fri, Dec 18, 2015 at 06:38:03PM -0800, Eric Dumazet wrote:
>> >> On Fri, 2015-12-18 at 19:58 +0100, Willy Tarreau wrote:
>> >> > Hi Josh,
>> >> >
>> >> > On Fri, Dec 18, 2015 at 08:33:45AM -0800, Josh Snyder wrote:
>> >> > > I was also puzzled that binding succeeded. Looking into the code paths
>> >> > > involved, in inet_csk_get_port, we quickly goto have_snum. From there, we end
>> >> > > up dropping into tb_found. Since !hlist_empty(&tb->owners), we end up checking
>> >> > > that (tb->fastreuseport > 0 && sk->sk_reuseport && uid_eq(tb->fastuid, uid)).
>> >> > > This test passes, so we goto success and bind.
>> >> > >
>> >> > > Crucially, we are checking the fastreuseport field on the inet_bind_bucket, and
>> >> > > not the sk_reuseport variable on the other sockets in the bucket. Since this
>> >> > > bit is set based on sk_reuseport at the time the first socket binds (see
>> >> > > tb_not_found), I can see no reason why sockets need to keep SO_REUSEPORT set
>> >> > > beyond initial binding.
>> >> > >
>> >> > > Given this, I believe Willy's patch elegantly solves the problem at hand.
>> >> >
>> >> > Great, thanks for your in-depth explanation.
>> >> >
>> >> > Eric, do you think that this patch may be acceptable material for next
>> >> > merge window (given that it's not a fix per-se) ? If so I'll resubmit
>> >> > later.
>> >>
>> >> I need to check with Craig Gallek, because he was about to upstream a
>> >> change to make SO_REUSEPORT more scalable & sexy (like having an [e]BPF
>> >> filter to perform the selection in an array of sockets)
>> >

Hi All,

I apologize for not properly following up on this. I had the
impression that we did not want to merge my original patch and then I
also noticed that it fails to keep the hash consistent. Recently, I
read the follow ups on it as well as Willy's patch/proposals.

Is there any update on Willy's SO_REUSEPORT patch? IMHO, it solves the
problem and it is simpler than adding new sock option.

Best Regards,
Tolga Ceylan