run ethtool outside container netns

We want to run as little as possible inside the container netns.

Unfortunately we cannot make that change for the weave container,
since the interface on which we need to invoke ethtool is created by
docker and already inside the container netns by the time we get
control.

weave

@@ -198,9 +198,6 @@ with_container_netns () {
 }
 
 connect_container_to_bridge() {
-    if ! ip link add name $LOCAL_IFNAME mtu $MTU type veth peer name $GUEST_IFNAME mtu $MTU ; then
-        return 1
-    fi
     if ip link set $LOCAL_IFNAME master $BRIDGE &&
         ip link set $LOCAL_IFNAME up &&
         ip link set $GUEST_IFNAME netns $NETNS ; then
@@ -214,6 +211,9 @@ connect_container_to_bridge() {
 }
 
 launch() {
+    if ! ip link add name $LOCAL_IFNAME mtu $MTU type veth peer name $GUEST_IFNAME mtu $MTU ; then
+        return 1
+    fi
     connect_container_to_bridge &&
         check_command_and_run_anything ethtool ip netns exec $NETNS ethtool -K eth0 tx off >/dev/null &&
         ip netns exec $NETNS ip link set $CONTAINER_IFNAME up
@@ -235,8 +235,12 @@ attach() {
         return 0
     fi
 
-    if ! connect_container_to_bridge ||
-        ! check_command_and_run_anything ethtool ip netns exec $NETNS ethtool -K $CONTAINER_IFNAME tx off >/dev/null ||
+    if ! ip link add name $LOCAL_IFNAME mtu $MTU type veth peer name $GUEST_IFNAME mtu $MTU ; then
+        return 1
+    fi
+
+    if ! check_command_and_run ethtool -K $GUEST_IFNAME tx off >/dev/null ||
+        ! connect_container_to_bridge ||
         ! ip netns exec $NETNS ip addr add $1 dev $CONTAINER_IFNAME ||
         ! ip netns exec $NETNS ip link set $CONTAINER_IFNAME up ; then
         return 1