linux-kernel - Re: Address already in use problem

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Message-ID: <20160921161211.GC13620@hmsreliant.think-freely.org>
Date:   Wed, 21 Sep 2016 12:12:12 -0400
From:   Neil Horman <nhorman@...driver.com>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     Sun Paul <paulrbk@...il.com>,
        "linux-sctp@...r.kernel.org" <linux-sctp@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Address already in use problem

On Wed, Sep 21, 2016 at 03:56:41PM +0000, David Laight wrote:
> From: Neil Horman
> > Sent: 21 September 2016 16:43
> > On Wed, Sep 21, 2016 at 09:44:30PM +0800, Sun Paul wrote:
> > > Hi
> > >
> > > we have an SCTP application running in JAVA. and we found that there
> > > is a problem when we as a client trying to connect to a remote IP
> > > address.
> > >
> > > If the remote IP address is not accessible, our application will keep
> > > retrying to connect using a self-defined local port address, says
> > > 51001,
> > >
> > > We found that after sometimes, says 2 hrs, this port 51001 is never
> > > able to bind to us again. even we tried to restart the application.
> > >
> > Sounds like you have another application that inadvertently bound to that port.
> > Its not a privlidged port, nor is it well known, so it seems plausible that
> > another application would eventually bind to it.  Thats not a bug, just the way
> > ip works.
> > 
> > run netstat -anp | grep 51001
> > 
> > And see what application is holding the port.
> 
> Not much chance of a distro having a netstat that gives sctp info.
> You might find something in /proc/net/sctp.
> 

True, but there is also no guarantee that the other application that claimed the
port in question is using SCTP.
Neil

> 3.18 contains a fix for a problem with shutdown() being called
> after the remote sends an INIT to restart an active connection
> when there is unacked data.
> If that happens the socket isn't released ever.
> 
> A workaround is to use SO_LINGER to get the connection aborted.
> 
> 	David
> 
>