(usagi-users 03465) IPv6 Multicast question - connect fails

[Bas Vermeulen <bvermeul@xxxxxxxxxxxxxxxxxxx>]

Hi,

I've got some code that does the following:

Takes an IPv6 multicast address, and opens an UDP socket with
socket(). It then sets the SO_REUSABLE sockopt, and binds the socket to
in6addr_any and port 5060. I then connect() to the IPv6 multicast
address (FF35::d:d44).

This works when the default interface has a global IPv6 address, but
fails with a site-local (FEC0::1) or link-local (FE80::1) address.

Does anyone know why, and where I can find more information on this
behaviour? I've included my test program. Any comments are welcome.

Thanks in advance,

-- 
Bas Vermeulen <bvermeul@xxxxxxxxxxxxxxxxxxx>

#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>

int main(int argc, char **argv)
{
	struct in6_addr addr6;
	char* interface;
	int err = 0;
	printf("Trying to connect to %s: ", argv[1]);
	if ((interface = strchr(argv[1], '%')) != NULL)
	{
		*interface = '\0';
		interface++;
	}

	if (inet_pton(AF_INET6, argv[1], &addr6) == 1)
	{
		int s, i = 1, ttl = 16;
		struct sockaddr_in6 my_addr;
		struct sockaddr_in6 dest_addr;
		struct ipv6_mreq mreq;

		if ((s = socket(PF_INET6, SOCK_DGRAM, 0)) < 0) { err = 1; goto done; }
		if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &i, sizeof(i)) < 0) { close(s); err = 2; goto done; }
		memset(&my_addr, 0, sizeof(my_addr));
		my_addr.sin6_family = AF_INET6;
		memcpy(&my_addr.sin6_addr, &in6addr_any, sizeof(my_addr.sin6_addr));
		my_addr.sin6_port = htons(0);
		if (bind(s, &my_addr, sizeof(my_addr)) < 0) { close(s); err = 3; goto done; }

		memset(&dest_addr, 0, sizeof(dest_addr));
		dest_addr.sin6_family = AF_INET6;
		memcpy(&dest_addr.sin6_addr, &addr6, sizeof(dest_addr.sin6_addr));
		dest_addr.sin6_port = htons(5060);
		if (interface)
			dest_addr.sin6_scope_id = if_nametoindex(interface);
		if (connect(s, &dest_addr, sizeof(dest_addr)) < 0) { close(s); err = 4; goto done; }
		setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &ttl, sizeof(ttl));
		printf("success.\n");
		return 0;
	}
done:
	switch (err)
	{
	case 0: printf("failed - not an IPv6 address.\n"); break;
	case 1: printf("failed - socket() - %s.\n", strerror(errno)); break;
	case 2: printf("failed - setsockopt(SO_REUSEADDR) - %s.\n", strerror(errno)); break;
	case 3: printf("failed - bind() - %s.\n", strerror(errno)); break;
	case 4: printf("failed - connect() - %s.\n", strerror(errno)); break;
	case 5: printf("failed - setsockopt(JOIN_GROUP) - %s.\n", strerror(errno)); break;
	}
	return 0;
}