Re: [9fans] multicast

[Jeff Sickel <jas@corpus-callosum.com>]

Steve,

Did you ever figure out how to setup addmulti?

-jas

> On Oct 6, 2014, at 10:41 AM, Steve Simon <steve@quintile.net> wrote:
>
> I am trying to listen to multicast DNS packets
> but when I try to configure the IP interface it fails,
> what am I missing?
>
> I do this (multicast with promiscuous)
>
> 	snprint(addr, sizeof(addr), "%s/udp!*!*", Netdir);
> 	if((cfd = announce(addr, dir)) < 0)
> 		sysfatal("%s cannot announce, %r\n", addr);
> 	if(fprint(cfd, "addmulti 224.0.0.251") < 0)
> 		sysfatal("add multicast addr 224.0.0.251 failed, %r");
>
> and it dies with 'addmulti for a non multicast address'
>
> which is caused by this failing:
>
> /sys/src/9/ip/ipifc.c
>
> 	int
> 	ipismulticast(uchar *ip)
> 	{
> 		if(isv4(ip)){
> 			if(ip[IPv4off] >= 0xe0 && ip[IPv4off] < 0xf0)
> 				return V4;
> 		}
> 		else if(ip[0] == 0xff)
> 			return V6;
> 		return 0;
> 	}
>
> But 0xe0 is 224 so it should not fail.
>
> I'am very confused.
>
> -Steve
>