icmp: Set sin6_scope_id for outbound ICMPv6 echo requests

If we ping a link-local address, we need to pass this to sendto(), as
it will obviously fail with -EINVAL otherwise.

If we ping other addresses, it's probably a good idea anyway to
specify the configured outbound interface here.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

icmp.c

@@ -192,6 +192,7 @@ int icmp_tap_handler(const struct ctx *c, int af, const void *addr,
 		struct sockaddr_in6 sa = {
 			.sin6_family = AF_INET6,
 			.sin6_addr = IN6ADDR_ANY_INIT,
+			.sin6_scope_id = c->ifi6,
 		};
 		struct icmp6hdr *ih;
 		int id, s;