netdev - Re: [REGRESSION] NFS is creating a hidden port (left over from xs

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Date:	Fri, 12 Jun 2015 08:43:42 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Trond Myklebust <trond.myklebust@...marydata.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Anna Schumaker <anna.schumaker@...app.com>,
	Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
	Linux Network Devel Mailing List <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [REGRESSION] NFS is creating a hidden port (left over from
 xs_bind() )

On Fri, 2015-06-12 at 10:57 -0400, Trond Myklebust wrote:
> On Fri, Jun 12, 2015 at 10:40 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:

> > Strange, because the usual way to not have time-wait is to use SO_LINGER
> > with linger=0
> >
> > And apparently xs_tcp_finish_connecting() has this :
> >
> >                 sock_reset_flag(sk, SOCK_LINGER);
> >                 tcp_sk(sk)->linger2 = 0;
> 
> Are you sure? I thought that SO_LINGER is more about controlling how
> the socket behaves w.r.t. waiting for the TCP_CLOSE state to be
> achieved (i.e. about aborting the FIN state negotiation early). I've
> never observed an effect on the TCP time-wait states.

Definitely this is standard way to avoid time-wait states.

Maybe not very well documented. We probably should...

http://stackoverflow.com/questions/3757289/tcp-option-so-linger-zero-when-its-required




> Yes. SO_REUSEADDR has the problem that it requires you bind to
> something other than 0.0.0.0, so it is less appropriate for outgoing
> connections; the RPC code really should not have to worry about
> routing and routability of a particular source address.

OK understood.

Are you trying to reuse same 4-tuple ?



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