Subject: Re: bind() should not return -EADDRINUSE

From: Phillip Susi <[email-masked]>
Date: Thu, 11 Dec 2014 14:50:48 -0500

On 12/11/2014 2:23 PM, David Miller wrote:
> From: Phillip Susi <[email-masked]> Date: Thu, 11 Dec 2014
> 14:19:11 -0500
> 
>> Attempting to establish a connection to a remote host using the
>> same local port, but a different remote port as the previous
>> connection ( that is still in TIME_WAIT ) results in bind()
>> returning -EADDRINUSE. By changing the remote port, you avoid the
>> conflict with the other connection that is in TIME_WAIT, but
>> since the remote port is not known when bind() is called, it
>> incorrectly returns -EADDRINUSE.  This check should not be done
>> in bind(), but deferred until the remote port is known in the
>> call to connect(), or listen().
> 
> Bind has to allocate and hold from everyone else on the system the 
> local port at bind() time, so we cannot defer this decision.

What on earth for?  If two processes are going to connect to different
remotes using the same source, that is perfectly fine.  The only
contention is if two processes want to listen() with the same local
addr and wildcard remote.