From 2702b85ee51ddf1833420190eb369daf439838ae Mon Sep 17 00:00:00 2001
From: Bryan Boreham <bjboreham@gmail.com>
Date: Mon, 23 May 2016 18:36:20 +0100
Subject: [PATCH] Improve veth name construction; use a constant instead of
 "ethwe"

---
 net/veth.go                                 | 12 +++++++++---
 plugin/net/driver.go                        |  2 +-
 prog/weaveutil/attach.go                    |  4 ++--
 prog/weavewait/check_network_iface.go       |  2 +-
 prog/weavewait/check_network_iface_mcast.go |  2 +-
 5 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/net/veth.go b/net/veth.go
index c8132c17..ea3e30d4 100644
--- a/net/veth.go
+++ b/net/veth.go
@@ -100,6 +100,11 @@ func contains(addrs []netlink.Addr, addr *net.IPNet) bool {
 	return false
 }
 
+const (
+	VethName   = "ethwe"        // name inside container namespace
+	vethPrefix = "v" + VethName // starts with "veth" to suppress UI notifications
+)
+
 func interfaceExistsInNamespace(ns netns.NsHandle, ifName string) bool {
 	err := WithNetNS(ns, func() error {
 		_, err := netlink.LinkByName(ifName)
@@ -110,10 +115,11 @@ func interfaceExistsInNamespace(ns netns.NsHandle, ifName string) bool {
 
 func AttachContainer(ns netns.NsHandle, id, ifName, bridgeName string, mtu int, withMulticastRoute bool, cidrs []*net.IPNet) error {
 	if !interfaceExistsInNamespace(ns, ifName) {
-		if len(id) > 5 {
-			id = id[:5]
+		maxIDLen := IFNAMSIZ - 1 - len(vethPrefix+"pl")
+		if len(id) > maxIDLen {
+			id = id[:maxIDLen] // trim passed ID if too long
 		}
-		name, peerName := "vethwepl"+id, "vethwg"+id
+		name, peerName := vethPrefix+"pl"+id, vethPrefix+"pg"+id
 		_, err := CreateAndAttachVeth(name, peerName, bridgeName, mtu, func(veth netlink.Link) error {
 			EthtoolTXOff(peerName) // TODO: do we want to do this under fastdp?
 			if err := netlink.LinkSetNsFd(veth, int(ns)); err != nil {
diff --git a/plugin/net/driver.go b/plugin/net/driver.go
index 30e4aa55..08f90a73 100644
--- a/plugin/net/driver.go
+++ b/plugin/net/driver.go
@@ -108,7 +108,7 @@ func (driver *driver) JoinEndpoint(j *api.JoinRequest) (*api.JoinResponse, error
 	response := &api.JoinResponse{
 		InterfaceName: &api.InterfaceName{
 			SrcName:   peerName,
-			DstPrefix: "ethwe",
+			DstPrefix: weavenet.VethName,
 		},
 	}
 	if !driver.noMulticastRoute {
diff --git a/prog/weaveutil/attach.go b/prog/weaveutil/attach.go
index 3e0ce82e..2dbe037f 100644
--- a/prog/weaveutil/attach.go
+++ b/prog/weaveutil/attach.go
@@ -40,7 +40,7 @@ func attach(args []string) error {
 	if err != nil {
 		return err
 	}
-	err = weavenet.AttachContainer(nsContainer, fmt.Sprint(pid), "ethwe", args[1], mtu, withMulticastRoute, cidrs)
+	err = weavenet.AttachContainer(nsContainer, fmt.Sprint(pid), weavenet.VethName, args[1], mtu, withMulticastRoute, cidrs)
 	// If we detected an error but the container has died, tell the user that instead.
 	if err != nil && !processExists(pid) {
 		err = fmt.Errorf("Container %s died", args[0])
@@ -97,5 +97,5 @@ func detach(args []string) error {
 	if err != nil {
 		return err
 	}
-	return weavenet.DetachContainer(ns, args[0], "ethwe", cidrs)
+	return weavenet.DetachContainer(ns, args[0], weavenet.VethName, cidrs)
 }
diff --git a/prog/weavewait/check_network_iface.go b/prog/weavewait/check_network_iface.go
index 9a627af8..78490144 100644
--- a/prog/weavewait/check_network_iface.go
+++ b/prog/weavewait/check_network_iface.go
@@ -7,6 +7,6 @@ import (
 )
 
 func checkNetwork() error {
-	_, err := weavenet.EnsureInterface("ethwe")
+	_, err := weavenet.EnsureInterface(weavenet.VethName)
 	return err
 }
diff --git a/prog/weavewait/check_network_iface_mcast.go b/prog/weavewait/check_network_iface_mcast.go
index 898c3b3d..978da38d 100644
--- a/prog/weavewait/check_network_iface_mcast.go
+++ b/prog/weavewait/check_network_iface_mcast.go
@@ -7,6 +7,6 @@ import (
 )
 
 func checkNetwork() error {
-	_, err := weavenet.EnsureInterfaceAndMcastRoute("ethwe")
+	_, err := weavenet.EnsureInterfaceAndMcastRoute(weavenet.VethName)
 	return err
 }