Re: [RFC Patch] net: reserve ports for applications using fixed portnumbers

From: Tetsuo Handa
Date: Fri Feb 05 2010 - 04:08:40 EST


Cong Wang wrote:
> The problem is that there are some existing applications which use
> fixed port number, we don't have chances to change this for them,
> thus making them working is desired, so they want to reserve these
> port for those applications.
>
> For example, if I have an appliction which uses port 40000, but
> before this application starts, another application gets this port
> number by bind() with port 0 (i.e. chosen by kernel), in this case,
> that application will fail to start. Again, we don't have any chance
> to change the source code of that application.
>
And there is a utility called "portreserved" (port reserve daemon).
http://fedoraproject.org/wiki/Features/Portreserve

But that utility cannot close the race window between "portreserved stops
reserving local port numbers" and "applications starts using local port
numbers which portreserved was reserving".

Thus, I think people want to have port reservation mechanism inside kernel
(if it has little impact).
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