Date: Fri, 12 May 2006 14:12:27 +0100 From: Bruce M Simpson <bms@spc.org> To: Stephen Clark <Stephen.Clark@seclark.us> Cc: freebsd-net@freebsd.org, Robert Watson <rwatson@FreeBSD.org>, pavlin@icir.org, atanu@icir.org Subject: Re: IP_MAX_MEMBERSHIPS story. Message-ID: <20060512131227.GD79277@spc.org> In-Reply-To: <4463FD1D.9010600@seclark.us> References: <20060509122801.GA65297@spc.org> <20060509131517.GB79277@spc.org> <20060512030152.X20138@fledge.watson.org> <4463FD1D.9010600@seclark.us>
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On Thu, May 11, 2006 at 11:12:29PM -0400, Stephen Clark wrote: > >I'm loosely of the opinion that the membership array should be > >variable length, and that we should default it to 20, but have a > >significantly larger maximum. It's not horribly efficient, but also > >wouldn't be so particularly terrible either. > > I think it should be tunable other than going in a changing the source > code, which I have to do every time I do a cvsup. This is the express intention of such a change. The problem the user(s) are having is because each imo_membership member's cardinality of relationship is 1:1 with respect to each multicast group membership and each ifnet interface upon which the membership is established. Therefore, joining the same group 20 times on different interfaces would exceed IP_MAX_MEMBERSHIPS. Fixing this in any way would still break the ip_mroute_kmod ABI and as such is a HEAD change. Based on Robert's feedback I would therefore make a change such that imo_membership is dynamically sized at runtime, rather than making IP_MAX_MEMBERSHIPS a load-time tunable. Based on reading of the code it looks like it may be best that imo_moptions becomes a pointer, not an array. I am happier with this kind of change because it is less invasive to other parts of netinet, and also because it fits in with the lazy allocation which already exists viz ip_findmoptions(). It is also much simpler -- the complexity belongs in ip_findmoptions() and ip_freemoptions(). Further feedback hoped for. I will post patches soon. Regards, BMS
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