fix IPv6 gateway reachability with ND proxy

IPv6 gateway traffic (DHCPv6/ICMP) fails when VPP takes over the uplink.
- Without gateway ND proxy, host NS for the default gateway is dropped by VPP
  with "neighbor solicitations for unknown targets" error due to missing /128
  target entry in the tap FIB.

Fix:
- Enable ND proxy for the gateway on the tap so the host can resolve the
  gateway via VPP.

Signed-off-by: Aritra Basu <[email protected]>

Author: Aritra Basu

vpp-manager/vpp_runner.go

@@ -654,6 +654,22 @@ func (v *VppRunner) configureVppUplinkInterface(
 		}
 	}
 
+	/*
+	 * Add ND proxy for IPv6 gateway addresses.
+	 * Without ND proxy for gateway, host's NS for gateway is dropped with "neighbor
+	 * solicitations for unknown targets" error because there's no /128 FIB entry.
+	 * This requires VPP patch https://gerrit.fd.io/r/c/vpp/+/44350 to fix NA loop bug.
+	 */
+	for _, route := range ifState.Routes {
+		if route.Gw != nil && route.Gw.To4() == nil {
+			log.Infof("Adding ND proxy for IPv6 gateway %s", route.Gw)
+			err = v.vpp.EnableIP6NdProxy(tapSwIfIndex, route.Gw)
+			if err != nil {
+				log.Errorf("Error configuring ND proxy for gateway %s: %v", route.Gw, err)
+			}
+		}
+	}
+
 	if *config.GetCalicoVppDebug().GSOEnabled {
 		err = v.vpp.EnableGSOFeature(tapSwIfIndex)
 		if err != nil {

vpplink/generated/vpp_clone_current.sh

@@ -145,6 +145,7 @@ git_cherry_pick refs/changes/07/43107/4 # 43107: vcl: fix fifo private vpp sh on
 git_cherry_pick refs/changes/14/43714/5 # 43714: session: fix handling of closed during migration | https://gerrit.fd.io/r/c/vpp/+/43714
 git_cherry_pick refs/changes/39/43139/5 # 43139: udp: regrab connected session after transport clone | https://gerrit.fd.io/r/c/vpp/+/43139
 git_cherry_pick refs/changes/23/43723/3 # 43723: session svm: fix session migrate attach data corruption | https://gerrit.fd.io/r/c/vpp/+/43723
+git_cherry_pick refs/changes/50/44350/2 # 44350: vnet: fix unicast NA handling in ND proxy | https://gerrit.fd.io/r/c/vpp/+/44350
 
 # --------------- private plugins ---------------
 # Generated with 'git format-patch --zero-commit -o ./patches/ HEAD^^^'