Reimplement docker_bridge_ip shell pipeline in Go

prog/weaveutil/addrs.go

@@ -77,3 +77,16 @@ func printNetDevs(cid string, netDevs []weavenet.Dev) {
 		fmt.Println()
 	}
 }
+
+func bridgeIP(args []string) error {
+	if len(args) < 1 {
+		cmdUsage("bridge-ip", "<bridgeName>")
+	}
+	bridgeName := args[0]
+	ip, err := weavenet.FindBridgeIP(bridgeName, nil)
+	if err != nil {
+		return err
+	}
+	fmt.Printf("%v", ip)
+	return nil
+}

prog/weaveutil/main.go

@@ -35,6 +35,7 @@ func init() {
 		"cni-net":                cniNet,
 		"cni-ipam":               cniIPAM,
 		"expose-nat":             exposeNAT,
+		"bridge-ip":              bridgeIP,
 	}
 }
 

weave

@@ -825,8 +825,7 @@ destroy_bridge() {
 }
 
 docker_bridge_ip() {
-    DOCKER_BRIDGE_IP=$(ip -4 addr show dev $DOCKER_BRIDGE | grep -m1 -o 'inet [.0-9]*') || return 1
-    DOCKER_BRIDGE_IP=${DOCKER_BRIDGE_IP#inet }
+    DOCKER_BRIDGE_IP=$(util_op bridge-ip $DOCKER_BRIDGE)
 }
 
 do_or_die() {