bgp: Unnumbered, disable v4, enable v6.

The end goal is to have full BGP unnumbered support including
routing of IPv4 prefixes over IPv6 nexthop, but the support is not
yet there.

Signed-off-by: Frode Nordahl <frode.nordahl@canonical.com>

microovn/frr/bgp/redirect.go

@@ -356,18 +356,67 @@ func startBgpUnnumbered(_ context.Context, extConnections []types.BgpExternalCon
 
 	var confBuilder strings.Builder
 	fmt.Fprintln(&confBuilder, "configure")
+
+	// Ensure we don't announce any default route from VRF to our peer.
+	fmt.Fprint(&confBuilder, `
+ip prefix-list no-default seq 5 deny 0.0.0.0/0
+ip prefix-list no-default seq 10 permit 0.0.0.0/0 le 32
+ipv6 prefix-list no-default seq 5 deny ::/0
+ipv6 prefix-list no-default seq 10 permit ::/0 le 128
+`)
+
 	fmt.Fprintf(&confBuilder, "router bgp %s vrf %s\n", asn, vrfName)
 	for _, connection := range extConnections {
 		fmt.Fprintf(&confBuilder,
 			"neighbor %s interface remote-as external\n",
 			getBgpRedirectIfaceName(connection.Iface),
 		)
+
+		// Disable IPv4 address family until we actually have support for
+		// routing IPv4 prefixes over IPv6 nexthops in OVN.
+		fmt.Fprint(&confBuilder,
+			"address-family ipv4 unicast\n",
+		)
+		fmt.Fprintf(&confBuilder,
+			"no neighbor %s activate\n",
+			getBgpRedirectIfaceName(connection.Iface),
+		)
+		fmt.Fprintln(&confBuilder,
+			"exit-address-family",
+		)
+
+		// Enable IPv6 address family.
+		fmt.Fprint(&confBuilder,
+			"address-family ipv6 unicast\n",
+		)
+		fmt.Fprintf(&confBuilder,
+			"neighbor %s soft-reconfiguration inbound\n",
+			getBgpRedirectIfaceName(connection.Iface),
+		)
+		fmt.Fprintf(&confBuilder,
+			"neighbor %s prefix-list no-default out\n",
+			getBgpRedirectIfaceName(connection.Iface),
+		)
+		fmt.Fprintln(&confBuilder,
+			"redistribute kernel",
+		)
+		fmt.Fprintf(&confBuilder,
+			"neighbor %s activate\n",
+			getBgpRedirectIfaceName(connection.Iface),
+		)
+		fmt.Fprintln(&confBuilder,
+			"exit-address-family",
+		)
 	}
 	fmt.Fprintln(&confBuilder, "do copy running-config startup-config")
 
 	cmd := exec.Command(filepath.Join(paths.Wrappers(), "vtysh"))
 	cmd.Stdin = strings.NewReader(confBuilder.String())
-	err := cmd.Run()
+	err := cmd.Start()
+	if err != nil {
+		return err
+	}
+	err = cmd.Wait()
 	return err
 }
 

tests/test_helper/bgp_utils.bash

@@ -28,8 +28,19 @@ function frr_start_bgp_unnumbered() {
 
     cat << EOF | lxc_exec "$container" "vtysh"
         configure
+        !
         router bgp $asn
         neighbor $interface interface remote-as external
+        !
+        address-family ipv4 unicast
+          no neighbor $interface activate
+        exit-address-family
+        !
+        address-family ipv6 unicast
+          neighbor $interface soft-reconfiguration inbound
+          neighbor $interface activate
+        exit-address-family
+        !
 EOF
 }