Re: IPv6 has trouble assigning an interface

[Felix von Leitner <felix-linuxkernel@fefe.de>]

Thus spake Pekka Savola (pekkas@netcore.fi):
> >Here is an strace of some piece of code of mine:
> >
> >socket(PF_INET6, SOCK_DGRAM, IPPROTO_IP) = 3
> >setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [12884901889], 4) = 0
> >bind(3, {sa_family=AF_INET6, sin6_port=htons(8002), inet_pton(AF_INET6, 
> >"::", &sin6_addr), sin6_flowinfo=0, sin6_scope_id=0}, 28) = 0
> >setsockopt(3, SOL_IPV6, IPV6_MULTICAST_LOOP, "\1", 1) = 0
> >[...]
> >sendto(3, "ncp-lowfat-1.2.2", 16, 0, {sa_family=AF_INET6, 
> >sin6_port=htons(8002), inet_pton(AF_INET6, "ff02::6e63:7030", &sin6_addr), 
> >sin6_flowinfo=0, sin6_scope_id=0}, 28) = -1 EADDRNOTAVAIL (Cannot assign 
> >requested address)
> >
> >ff02 is a link-local multicast address.  I've bound to ::.  How can this
> >fail?  link-local should always work, even if no routes are set and no
> >router has been found.
> Umm.. link-local unicast and multicast both require that you specify 
> the interface, because otherwise it's ambiguous -- how could the 
> kernel know which interface should be used to send the packet?

OK for unicast.
But multicast?  I expected link-local multicast to send on _all_
interfaces if I don't specify one.

Felix