Refactor common.GetBridgeNetDev

- Optimize. Use LinkByName instead of iterating over list of available
  links. Linux does not support interfaces with the same names.
- Remove unnecessary indirection in utility functions which return
  common.NetDev.

common/utils.go

@@ -55,7 +55,7 @@ func FindNetDevs(processID int, match func(link netlink.Link) bool) ([]NetDev, e
 				if err != nil {
 					return err
 				}
-				netDevs = append(netDevs, *netDev)
+				netDevs = append(netDevs, netDev)
 			}
 			return nil
 		})
@@ -77,13 +77,13 @@ func forEachLink(f func(netlink.Link) error) error {
 	return nil
 }
 
-func linkToNetDev(link netlink.Link) (*NetDev, error) {
+func linkToNetDev(link netlink.Link) (NetDev, error) {
 	addrs, err := netlink.AddrList(link, netlink.FAMILY_V4)
 	if err != nil {
-		return nil, err
+		return NetDev{}, err
 	}
 
-	netDev := &NetDev{Name: link.Attrs().Name, MAC: link.Attrs().HardwareAddr}
+	netDev := NetDev{Name: link.Attrs().Name, MAC: link.Attrs().HardwareAddr}
 	for _, addr := range addrs {
 		netDev.CIDRs = append(netDev.CIDRs, addr.IPNet)
 	}
@@ -133,11 +133,20 @@ func GetWeaveNetDevs(processID int) ([]NetDev, error) {
 	})
 }
 
-// Get the weave bridge interface
-func GetBridgeNetDev(bridgeName string) ([]NetDev, error) {
-	return FindNetDevs(1, func(link netlink.Link) bool {
-		return link.Attrs().Name == bridgeName
+// Get the weave bridge interface.
+func GetBridgeNetDev(bridgeName string) (NetDev, error) {
+	var netdev NetDev
+
+	err := weavenet.WithNetNSLinkByPid(1, bridgeName, func(link netlink.Link) error {
+		var err error
+		netdev, err = linkToNetDev(link)
+		if err != nil {
+			return err
+		}
+		return nil
 	})
+
+	return netdev, err
 }
 
 // Do post-attach configuration of all veths we have created

net/netns.go

@@ -35,3 +35,13 @@ func WithNetNSLink(ns netns.NsHandle, ifName string, work func(link netlink.Link
 		return work(link)
 	})
 }
+
+func WithNetNSLinkByPid(pid int, ifName string, work func(link netlink.Link) error) error {
+	ns, err := netns.GetFromPid(pid)
+	if err != nil {
+		return err
+	}
+	defer ns.Close()
+
+	return WithNetNSLink(ns, ifName, work)
+}

plugin/net/cni.go

@@ -131,23 +131,20 @@ func setupRoutes(link netlink.Link, name string, ipnet net.IPNet, gw net.IP, rou
 }
 
 func findBridgeIP(bridgeName string, subnet net.IPNet) (net.IP, error) {
-	netdevs, err := common.GetBridgeNetDev(bridgeName)
+	netdev, err := common.GetBridgeNetDev(bridgeName)
 	if err != nil {
 		return nil, fmt.Errorf("Failed to get netdev for %q bridge: %s", bridgeName, err)
 	}
-	if len(netdevs) == 0 {
-		return nil, fmt.Errorf("Could not find %q bridge", bridgeName)
-	}
-	if len(netdevs[0].CIDRs) == 0 {
+	if len(netdev.CIDRs) == 0 {
 		return nil, fmt.Errorf("Bridge %q has no IP addresses", bridgeName)
 	}
-	for _, cidr := range netdevs[0].CIDRs {
+	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 netdevs[0].CIDRs[0].IP, nil
+	return netdev.CIDRs[0].IP, nil
 }
 
 func (c *CNIPlugin) CmdDel(args *skel.CmdArgs) error {

prog/weaveutil/addrs.go

@@ -41,7 +41,11 @@ func containerAddrs(args []string) error {
 
 func getNetDevs(bridgeName string, c *docker.Client, containerID string) ([]common.NetDev, error) {
 	if containerID == "weave:expose" {
-		return common.GetBridgeNetDev(bridgeName)
+		if netDev, err := common.GetBridgeNetDev(bridgeName); err != nil {
+			return nil, err
+		} else {
+			return []common.NetDev{netDev}, nil
+		}
 	}
 
 	container, err := c.InspectContainer(containerID)

prog/weaveutil/main.go

@@ -30,6 +30,7 @@ func main() {
 		usage()
 		os.Exit(1)
 	}
+
 	cmd, found := commands[os.Args[1]]
 	if !found {
 		usage()

proxy/proxy.go

@@ -149,14 +149,14 @@ func NewProxy(c Config) (*Proxy, error) {
 	p.client = client.Client
 
 	if !p.WithoutDNS {
-		netDevs, err := common.GetBridgeNetDev(c.DockerBridge)
+		netDev, err := common.GetBridgeNetDev(c.DockerBridge)
 		if err != nil {
 			return nil, err
 		}
-		if len(netDevs) != 1 || len(netDevs[0].CIDRs) != 1 {
+		if len(netDev.CIDRs) != 1 {
 			return nil, fmt.Errorf("Could not obtain address of %s", c.DockerBridge)
 		}
-		p.dockerBridgeIP = netDevs[0].CIDRs[0].IP.String()
+		p.dockerBridgeIP = netDev.CIDRs[0].IP.String()
 	}
 
 	p.hostnameMatchRegexp, err = regexp.Compile(c.HostnameMatch)