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From: Willy Tarreau <>
To: Nebojsa Miljanovic <>
Cc: Alan Cox <>,, "Kittlitz,
	Edward (Ned)" <>,, "Polhemus,
	William (Bart)" <>
Subject: Re: SO_REUSEADDR not allowing server and client to use same port
Date: Tue, 18 Mar 2008 06:48:19 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Mon, Mar 17, 2008 at 01:17:29PM -0500, Nebojsa Miljanovic wrote:
> OK. I see. So, it would have to be some malicious application running together
> with the server (i.e. on the same CPU). I do see now why you said it would be
> very very hard to make this happen.
> Still, it would be nice to introduce SO_REUSEPORT socket options so secure
> servers (who happen to be clients as well) can re-use ports when necessary.
> Another option would be to check if port re-use is happening inside same
> application and allow it. That may make half of the folks happy, so I am not
> sure if I like it as much as I like SO_REUSEPORT option.

It is most often useful for hot-restart without interrupting service.
As an example, when I update a config in haproxy, I restart a new instance
which does everything and binds to the ports, and then signals the old one
it may go. That way, there is a complete continuity of service. This is
possible by default on *BSD, and with a (very) little patch on linux.

And I agree with Alan about the security implications. If a service binds
itself with SO_REUSEPORT, it definitely says "I agree to share my connection".
So this is not to be used by default in any random application. But for
servers, it's really useful.


  reply	other threads:[~2008-03-18  5:51 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-28 18:15 Nebojsa Miljanovic
2008-02-28 18:30 ` Phil Oester
2008-02-28 20:19 ` Alan Cox
2008-02-28 20:41   ` Willy Tarreau
2008-03-13 19:18   ` Nebojsa Miljanovic
2008-03-15 13:34     ` Alan Cox
2008-03-17 16:43       ` Nebojsa Miljanovic
2008-03-17 17:30         ` Alan Cox
2008-03-17 18:17           ` Nebojsa Miljanovic
2008-03-18  5:48             ` Willy Tarreau [this message]
2008-02-28 20:36 ` Willy Tarreau
2008-02-28 20:44   ` Nebojsa Miljanovic

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