Add weaveutil process-addrs

Fetches addresses for every veth that is in a network namespace and
attached to the specified bridge.  Works by iterating over every process.

prog/weaveutil/main.go

@@ -20,6 +20,7 @@ func init() {
 		"create-plugin-network":  createPluginNetwork,
 		"remove-plugin-network":  removePluginNetwork,
 		"container-addrs":        containerAddrs,
+		"process-addrs":          processAddrs,
 		"attach-container":       attach,
 		"detach-container":       detach,
 	}

prog/weaveutil/proc-addrs.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"strconv"
+
+	"github.com/weaveworks/weave/common"
+	weavenet "github.com/weaveworks/weave/net"
+)
+
+func processAddrs(args []string) error {
+	if len(args) < 1 {
+		cmdUsage("process-addrs", "<bridgeName>")
+	}
+	bridgeName := args[0]
+
+	pred, err := common.ConnectedToBridgePredicate(bridgeName)
+	if err != nil {
+		if err == weavenet.ErrLinkNotFound {
+			return nil
+		}
+		return err
+	}
+
+	pids, err := common.AllPids("/proc")
+	if err != nil {
+		return err
+	}
+
+	// NB: Because network namespaces (netns) are changed many times inside the loop,
+	//     it's NOT safe to exec any code depending on the root netns without
+	//     wrapping with WithNetNS*.
+	for _, pid := range pids {
+		netDevs, err := common.GetNetDevsWithPredicate(pid, pred)
+		if err != nil {
+			return err
+		}
+		printNetDevs(strconv.Itoa(pid), netDevs)
+	}
+	return nil
+}