Re: IPv6 has trouble assigning an interface

[Pekka Savola <pekkas@netcore.fi>]

On Mon, 25 Apr 2005, Felix von Leitner wrote:
> 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?

--
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
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