netdev - Re: linux kernel's IPV6_MULTICAST_HOPS default is 64; should be 1?

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Date:	Tue, 04 May 2010 14:38:24 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	brian.haley@...com
Cc:	dlstevens@...ibm.com, enh@...gle.com, netdev@...r.kernel.org,
	netdev-owner@...r.kernel.org
Subject: Re: linux kernel's IPV6_MULTICAST_HOPS default is 64; should be 1?

From: Brian Haley <brian.haley@...com>
Date: Tue, 04 May 2010 10:40:58 -0400

> Not exactly.  It fixes the case where it's wrong by default, but
> the corner case of setting it to -1 via setsockopt() says:
> 
>     x == -1:       use kernel default
> 
> But that will revert back to the kernel using 64 on the next transmit.
> I can work on an update to this that makes a new mcast_hops per-interface
> setting and makes ip6_dst_hoplimit() aware of it.  Or even easier, just
> have setsockopt() trap the -1 and set np->mcast_hops to 1.  Built but
> untested patch below.

I thought that we agreed that when the user explicitly asks for "-1"
it should get the behavior right now, with is to use
ip6_dst_hoplimit()?  I think I even acknowledged when Elliot mentioned
this explicitly, and I think it's a good idea.
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