netdev - Re: binding UDP port 0 with SO

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Message-ID: <CAEZM=bM=AGp=FOxLiDiBFgVJWGmNdPpG_FV3Ne2i5jeALiB4YA@mail.gmail.com>
Date:	Thu, 2 Aug 2012 18:33:43 +0200
From:	"Tobias S. Josefowitz" <t.josefowitz@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: binding UDP port 0 with SO_REUSEADDR

Hi again,

I need to say, after looking at "my" socket(7),

       SO_REUSEADDR
              Indicates  that  the rules used in validating addresses supplied
              in a bind(2) call should allow reuse of  local  addresses.   For
              AF_INET  sockets  this means that a socket may bind, except when
              there is an active listening socket bound to the address.   When
              the listening socket is bound to INADDR_ANY with a specific port
              then it is not possible to bind  to  this  port  for  any  local
              address.  Argument is an integer boolean flag.

I think the surprise-factor of the bind-0-behaviour even increased for
me. Is there a specific reason for handing out used ports when binding
port 0 with REUSEADDR?

Best,

Tobi
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