Fix routing between containers on same host

main.go

@@ -259,8 +259,28 @@ func configureContainerInterface(containerNS netns.NsHandle, ifName string, cont
 	}
 
 	if hostLLAddr != nil {
-		// Add route to Mycelium network via host veth
+		// First remove any existing route to our /64
+		myceliumPrefix := &net.IPNet{
+			IP:   containerIP.Mask(net.CIDRMask(64, 128)),
+			Mask: net.CIDRMask(64, 128),
+		}
+		existingRoute := &netlink.Route{
+			Dst: myceliumPrefix,
+		}
+		netlink.RouteDel(existingRoute)
+
+		// Add route to our /64 via host veth
 		route := &netlink.Route{
+			Dst:       myceliumPrefix,
+			Gw:        hostLLAddr,
+			LinkIndex: link.Attrs().Index,
+		}
+		if err := netlink.RouteAdd(route); err != nil {
+			return err
+		}
+
+		// Add route to Mycelium network via host veth
+		route = &netlink.Route{
 			Dst: &net.IPNet{
 				IP:   net.ParseIP("400::"),
 				Mask: net.CIDRMask(7, 128),