linux-kernel - Re: [RFC Patch] net: reserve ports for applications using fixed port numbers

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Message-Id: <201002050041.o150fCO8081208@www262.sakura.ne.jp>
Date:	Fri, 05 Feb 2010 09:41:12 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	davem@...emloft.net
Cc:	opurdila@...acom.com, amwang@...hat.com,
	linux-kernel@...r.kernel.org, eric.dumazet@...il.com,
	linux-rdma@...r.kernel.org, netdev@...r.kernel.org,
	nhorman@...driver.com, linux-sctp@...r.kernel.org
Subject: Re: [RFC Patch] net: reserve ports for applications using fixed port numbers

David Miller wrote:
> > Octavian Purdila wrote:
> >> 
> >> int inet_is_reserved_local_port(int port)
> >> {
> >> 	if (test_bit(port, reserved_ports))
> >> 		return 1;
> >> 	return 0;
> >> }
> >> 
> > Above check is exactly what I'm doing in the LSM hook.
> 
> But his version can be done inline in 2 or 3 instructions.
> 
> An LSM hook will result in an indirect function call,
> all live registers spilled to the stack, then all of
> those reloaded when the function returns.
> 
> It will be much more expensive.

If you can accept his version, I want to use his version (with an interface for
updating above "reserved_ports" by not only root user's sysctl() but also MAC's
policy configuration).
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