From e55f5694a7f28a142c32cb4262df018418fc5714 Mon Sep 17 00:00:00 2001
From: Scott Yeager <yeagersm@gmail.com>
Date: Fri, 20 Jun 2025 18:23:37 -0700
Subject: [PATCH] update route handling

---
 main.go | 57 ++++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 34 insertions(+), 23 deletions(-)

diff --git a/main.go b/main.go
index 61fc0f2..4f8c005 100644
--- a/main.go
+++ b/main.go
@@ -62,7 +62,7 @@ func cmdAdd(args *skel.CmdArgs) error {
 
 	// Configure container interface
 	containerIP := generateContainerIP(myceliumIP, args.ContainerID)
-	if err := configureContainerInterface(containerNS, containerVethName, containerIP, hostVethName); err != nil {
+	if err := configureContainerInterface(containerNS, containerVethName, containerIP, hostVeth); err != nil {
 		return fmt.Errorf("failed to configure container interface: %v", err)
 	}
 
@@ -182,7 +182,7 @@ func createVethPair(hostName, containerName string) (netlink.Link, netlink.Link,
 	return hostVeth, containerVeth, nil
 }
 
-func configureContainerInterface(containerNS netns.NsHandle, ifName string, containerIP net.IP, hostVethName string) error {
+func configureContainerInterface(containerNS netns.NsHandle, ifName string, containerIP net.IP, hostVeth netlink.Link) error {
 	// Switch to container namespace
 	originalNS, err := netns.Get()
 	if err != nil {
@@ -216,27 +216,23 @@ func configureContainerInterface(containerNS netns.NsHandle, ifName string, cont
 			return err
 		}
 
-		// Get host veth link-local address for routing
-		hostVeth, err := netlink.LinkByName(hostVethName)
-		if err == nil {
-			hostAddrs, err := netlink.AddrList(hostVeth, netlink.FAMILY_V6)
-			if err == nil {
-				for _, addr := range hostAddrs {
-					if addr.IP.IsLinkLocalUnicast() {
-						// Add route to Mycelium network via host veth
-						route := &netlink.Route{
-							Dst: &net.IPNet{
-								IP:   net.ParseIP("400::"),
-								Mask: net.CIDRMask(7, 128),
-							},
-							Gw:        addr.IP,
-							LinkIndex: link.Attrs().Index,
-						}
-						netlink.RouteAdd(route)
-						break
-					}
-				}
-			}
+		// Get host veth link-local address (it should be available now)
+		hostLinkLocal, err := getHostVethLinkLocal(hostVeth)
+		if err != nil {
+			return fmt.Errorf("failed to get host veth link-local address: %v", err)
+		}
+
+		// Add route to Mycelium network via host veth link-local address
+		route := &netlink.Route{
+			Dst: &net.IPNet{
+				IP:   net.ParseIP("400::"),
+				Mask: net.CIDRMask(7, 128),
+			},
+			Gw:        hostLinkLocal,
+			LinkIndex: link.Attrs().Index,
+		}
+		if err := netlink.RouteAdd(route); err != nil {
+			return fmt.Errorf("failed to add route to 400::/7: %v", err)
 		}
 
 		return nil
@@ -254,3 +250,18 @@ func configureHostInterface(hostVeth netlink.Link, containerIP net.IP) error {
 
 	return netlink.RouteAdd(route)
 }
+
+func getHostVethLinkLocal(hostVeth netlink.Link) (net.IP, error) {
+	addrs, err := netlink.AddrList(hostVeth, netlink.FAMILY_V6)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get addresses for host veth: %v", err)
+	}
+
+	for _, addr := range addrs {
+		if addr.IP.IsLinkLocalUnicast() {
+			return addr.IP, nil
+		}
+	}
+
+	return nil, fmt.Errorf("no link-local address found on host veth")
+}