On 1 April 2012 19:48, Nick Wagner <ne...@wingedbeast.org> wrote: >> >> Yea, you are kinda' right. I want the daemon to listen on any and all >> interfaces >> ie. 0.0.0.0. But it seems that when the slp daemon starts up, and there is >> not >> default gw, the multicast setup fails. This is probably a fundamental >> misunderstanding >> on my part. If multicast needs a default route when any interface is >> used, that means >> that only one interface sends out the IGMP group join stuff. That >> would mean only >> one interface sends the service multicast packets (our is only a SA). >> What am i doing >> wrong, or do I just misunderstand the problem? >> > > Sockets that want to send multicast over a particular network interface must > set a socket option to send over that interface. Otherwise, the stack will > only send it out whatever network interface it considers the > primary/default. And the socket option (IP_MULTICAST_IF) takes an ip > address, although I have no idea if that preference "sticks" if the > interface changes its address subsequent to the setsockopt. I've never > tried to do any of this with 0.0.0.0, it could be that it just fails. > Ok. I think i have an understanding of the startup. The daemon starts up, and must send out IGMP join requests on the interfaces. If the 0.0.0.0 is given, then the kernel just chooses the default route, and sends it. That is why when our system does not yet have the default route setup, the mulicast setup fails.
BTW, our concerns are about restarting the slp daemon. In an small system, there are always ewww responses, when a daemon needs to be restarted. I know most don't see an issue with this, but there could be blocking issues with restarting the damon (using system()). > I don't know anything about your device/product, but is there a point in > your device that you know it has the necessary ip addresses? Either via > moving the daemon startup in rc.d, or using whatever watchdogs your device > may have? And is slpd the only program on your device that has this sort of > ip address issue? The difference would be that most daemons only listen, where the slp needs to register itself, ie. send data to a multicast address. I have guessed 3 "possible" work-arounds to this. 1. Is there a way to setup a routing rule with iptables or equivalent, to forward multicast addresses from the loopback interface? 2. Some type of simple userspace daemon which listens to loopback multicast and then forwards the traffic to the interfaces. Of course, this is a thought without reading the slp protocol in depth :-P 3. Allow SIG_HUP to call re-initialize network also (opposite to HandleSigTerm()) without exiting daemon. /Ryan > > --Nick ------------------------------------------------------------------------------ This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure _______________________________________________ Openslp-users mailing list Openslp-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/openslp-users
