Subject: Re: sunrpc port allocation and IANA reserved list
From: Ben Hutchings <bhutchings@solarflare.com>
To: Chuck Lever <chuck.lever@oracle.com>
Cc: Chris Friesen <cfriesen@nortel.com>,
       Trond Myklebust <trond.myklebust@fys.uio.no>, netdev@vger.kernel.org,
       Linux kernel <linux-kernel@vger.kernel.org>
In-Reply-To: <212D08D7-AC22-4857-837A-E72B0A11E8DE@oracle.com>
References: <4AF9A63B.6010101@nortel.com>
	 <1257875623.2834.19.camel@achroite.uk.solarflarecom.com>
	 <4AF9B2CF.6050305@nortel.com>
	 <1257884799.3044.7.camel@heimdal.trondhjem.org>
	 <4AF9D5D1.9040501@nortel.com>
	 <1257888720.2834.30.camel@achroite.uk.solarflarecom.com>
	 <212D08D7-AC22-4857-837A-E72B0A11E8DE@oracle.com>
Content-Type: text/plain
Organization: Solarflare Communications
Date: Tue, 10 Nov 2009 21:42:01 +0000
Message-Id: <1257889321.2834.35.camel@achroite.uk.solarflarecom.com>
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1844
Lines: 50

On Tue, 2009-11-10 at 16:34 -0500, Chuck Lever wrote:
> On Nov 10, 2009, at 4:32 PM, Ben Hutchings wrote:
> 
> > On Tue, 2009-11-10 at 15:06 -0600, Chris Friesen wrote:
> >> On 11/10/2009 02:26 PM, Trond Myklebust wrote:
[...]
> >>> Just use /proc/sys/sunrpc/{max,min}_resvport interface to restrict  
> >>> the
> >>> range used to a safer one. That's what it is for...
> >
> > Unless I'm much mistaken, that only affects in-kernel SunRPC users.
> >
> >> What constitutes a "safer range"?  IANA has ports assigned
> >> intermittently all the way through the default RPC range.  The  
> >> largest
> >> unassigned range is 922-988 (since 921 is used by lwresd).  If  
> >> someone
> >> needs more than 66 ports, how are they supposed to handle it?
> >
> > I'm sure we could afford 128 bytes for a blacklist of privileged  
> > ports.
> > However, the problem is that there is no API for userland to request
> > 'any free privileged port' - it has to just try binding to different
> > ports until it finds one available.
> 
> bindresvport(3) and bindresvport_sa(3t) ?

These are library calls; they are not an API between userland the
kernel.

> > This means that the kernel can't
> > tell whether a process is trying to allocate a specifically assigned
> > port or whether the blacklist should be applied.
> 
> Such a blacklist would have to be managed by glibc or libtirpc.

Right.

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/