Extract FindBridgeIP to net package

net/bridge.go

@@ -2,6 +2,7 @@ package net
 
 import (
 	"fmt"
+	"net"
 
 	"github.com/Sirupsen/logrus"
 	"github.com/vishvananda/netlink"
@@ -86,3 +87,24 @@ func DetectHairpin(portIfName string, log *logrus.Logger) error {
 
 	return nil
 }
+
+var ErrBridgeNoIP = fmt.Errorf("Bridge has no IP address")
+
+func FindBridgeIP(bridgeName string, subnet *net.IPNet) (net.IP, error) {
+	netdev, err := GetBridgeNetDev(bridgeName)
+	if err != nil {
+		return nil, fmt.Errorf("Failed to get netdev for %q bridge: %s", bridgeName, err)
+	}
+	if len(netdev.CIDRs) == 0 {
+		return nil, ErrBridgeNoIP
+	}
+	if subnet != nil {
+		for _, cidr := range netdev.CIDRs {
+			if subnet.Contains(cidr.IP) {
+				return cidr.IP, nil
+			}
+		}
+	}
+	// No subnet, or none in the required subnet; just return the first one
+	return netdev.CIDRs[0].IP, nil
+}

plugin/net/cni.go

@@ -73,8 +73,8 @@ func (c *CNIPlugin) CmdAdd(args *skel.CmdArgs) error {
 
 	// If config says nothing about routes or gateway, default one will be via the bridge
 	if result.IP4.Routes == nil && result.IP4.Gateway == nil {
-		bridgeIP, err := findBridgeIP(conf.BrName, result.IP4.IP)
-		if err == errBridgeNoIP {
+		bridgeIP, err := weavenet.FindBridgeIP(conf.BrName, &result.IP4.IP)
+		if err == weavenet.ErrBridgeNoIP {
 			bridgeArgs := *args
 			bridgeArgs.ContainerID = "weave:expose"
 			bridgeIPResult, err := c.getIP(conf.IPAM.Type, &bridgeArgs)
@@ -164,25 +164,6 @@ func assignBridgeIP(bridgeName string, ipnet net.IPNet) error {
 	return nil
 }
 
-var errBridgeNoIP = fmt.Errorf("Bridge has no IP address")
-
-func findBridgeIP(bridgeName string, subnet net.IPNet) (net.IP, error) {
-	netdev, err := weavenet.GetBridgeNetDev(bridgeName)
-	if err != nil {
-		return nil, fmt.Errorf("Failed to get netdev for %q bridge: %s", bridgeName, err)
-	}
-	if len(netdev.CIDRs) == 0 {
-		return nil, errBridgeNoIP
-	}
-	for _, cidr := range netdev.CIDRs {
-		if subnet.Contains(cidr.IP) {
-			return cidr.IP, nil
-		}
-	}
-	// None in the required subnet; just return the first one
-	return netdev.CIDRs[0].IP, nil
-}
-
 func (c *CNIPlugin) CmdDel(args *skel.CmdArgs) error {
 	conf, err := loadNetConf(args.StdinData)
 	if err != nil {

proxy/proxy.go

@@ -148,14 +148,11 @@ func NewProxy(c Config) (*Proxy, error) {
 	p.client = client.Client
 
 	if !p.WithoutDNS {
-		netDev, err := weavenet.GetBridgeNetDev(c.DockerBridge)
+		ip, err := weavenet.FindBridgeIP(c.DockerBridge, nil)
 		if err != nil {
 			return nil, err
 		}
-		if len(netDev.CIDRs) < 1 {
-			return nil, fmt.Errorf("Could not obtain address of %s", c.DockerBridge)
-		}
-		p.dockerBridgeIP = netDev.CIDRs[0].IP.String()
+		p.dockerBridgeIP = ip.String()
 		Log.Infof("Using docker bridge IP for DNS: %v", p.dockerBridgeIP)
 	}