Messages in this thread | | | Date | Fri, 2 Mar 2012 14:19:45 -0800 (PST) | From | david@lang ... | Subject | Re: [PATCH 0/10] af_unix: add multicast and filtering features to AF_UNIX |
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On Fri, 2 Mar 2012, David Miller wrote:
> From: Luiz Augusto von Dentz <luiz.dentz@gmail.com> > Date: Fri, 2 Mar 2012 10:39:24 +0200 > >> Like I said before there is many projects using AF_UNIX as IPC >> transport, the documentation actually induces people to use for this >> purpose, and many would benefit from being able to do multicast. > > You can't have it both ways. > > If it's useful for many applications, then many applications would > benefit from a userland library that solved the problem using > existing facilities such as IP multicast.
I missed the start of this discussion (but did see the lwn.net article on it)
as I understand it, they are looking for some features that are not in IP multicast (or at least not as I understand it)
1. reliable delivery
2. in-order delivery
3. sender blocking on recipients rather than dropping messages when the channel is full.
IP multicast definantly does not do #3, and as far as I understand it, is essentially UDP to multiple recipients, and UDP does not provide either #1 or #2
Yes, this could be done entirely in userspace (with something like 0MQ as I see others mentioning), and I don't understand the Android aversion to any userspace daemons, but with all of that being said, I do think that a kernel-based mechanism that supports having iptables type filters on it would be a very nice thing to have (and should be able to re-use a lot of existing code that would end up being duplicated if this is done in a userspace daemon)
now it may be that some of the requirements may result in error O_PONY or O_SANITY (the sender blocking seems like a potential problem, but that may possibly make sense as a configurable option)
David Lang
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