isis: do not include non-link-local IPv6 addresses in Hello PDUs

RFC 5308 Section 3 says the following:
  For Hello PDUs, the "Interface Address" TLV MUST contain only the
  link-local IPv6 addresses assigned to the interface that is sending
  the Hello.

This fixes a problem where IPv6 routes were incorrectly computed using
unique local addresses (fc00::/7) as nexthops when testing holo-isis
in munet.

Signed-off-by: Renato Westphal <[email protected]>

holo-isis/src/interface.rs

@@ -489,7 +489,11 @@ impl Interface {
         {
             protocols_supported.push(Nlpid::Ipv6 as u8);
             ipv6_addrs.extend(
-                self.system.ipv6_addr_list.iter().map(|addr| addr.ip()),
+                self.system
+                    .ipv6_addr_list
+                    .iter()
+                    .filter(|addr| addr.ip().is_unicast_link_local())
+                    .map(|addr| addr.ip()),
             );
         }