More lenient ipv6 auto-update

src/service.rs

@@ -1345,6 +1345,28 @@ impl Service {
                     }
                     InsertResult::ValueUpdated | InsertResult::UpdatedPending => {}
                     InsertResult::Failed(reason) => {
+                        // On large networks with limited IPv6 nodes, it is hard to get enough
+                        // PONG votes in order to estimate our external IP address. Often the
+                        // routing table can be full, and so we reject useful IPv6 here.
+                        //
+                        // If we are low on votes and we initiated this connection (i.e it was not
+                        // forced on us) then lets get a PONG from this node.
+
+                        if direction == ConnectionDirection::Outgoing {
+                            if let Some(ip_votes) = self.ip_votes.as_mut() {
+                                match (ip_votes.majority(), enr.udp4_socket(), enr.udp6_socket()) {
+                                    // We don't have enough ipv4 votes, but this is an IPv4 node.
+                                    ((None, Some(_)), Some(_), _) | 
+                                    // We don't have enough ipv6 votes, but this is an IPv6 node
+                                    ((Some(_), None), _, Some(_)) |
+                                    // We don't have enough ipv6 or ipv4 nodes, ping this peer
+                                    ((None, None), _, _) => self.send_ping(enr, None),
+                                    // We have enough votes do nothing
+                                    ((_, _), _, _) =>  {}
+                                }
+                            }
+                        }
+
                         self.peers_to_ping.remove(&node_id);
                         trace!(%node_id, ?reason, "Could not insert node");
                     }