add a test to see whether ethtool is available before trying to run it

weaver/weave

@@ -87,7 +87,12 @@ ip netns exec $NSPID ip link set $GUEST_IFNAME name $CONTAINER_IFNAME
 ip netns exec $NSPID ip addr add $IPADDR dev $CONTAINER_IFNAME
 ip netns exec $NSPID ip link set $CONTAINER_IFNAME up
 
-ip netns exec $NSPID ethtool -K $IFACE tx off > /dev/null
+if [ command -v ethtool >/dev/null 2>&1 ]
+then
+    ip netns exec $NSPID ethtool -K $IFACE tx off > /dev/null
+else
+    echo "Unable to run ethtool command; continuing without it" >&2
+fi
 
 [ -f /var/run/netns/$NSPID ] && rm -f /var/run/netns/$NSPID