ditch check_command_and_run wrapper

Since we end up swallowing the warning when wanting to redirect stderr
of the command execution.

Fixes #286.

weave

@@ -24,12 +24,6 @@ usage() {
     exit 1
 }
 
-# utility function to check whether a command can be executed by the shell
-# see http://stackoverflow.com/questions/592620/how-to-check-if-a-program-exists-from-a-bash-script
-command_exists () {
-    command -v $1 >/dev/null 2>&1
-}
-
 [ `id -u` = 0 ] || {
     echo "weave must be run as 'root'" >&2
     exit 1
@@ -53,18 +47,17 @@ COMMAND=$1
 
 shift 1
 
-check_command_and_run_anything() {
-    if command_exists $1
-    then
-        shift 1
-        "$@"
-    else
-        echo "Cannot find $1; please install it. Continuing without it." >&2
-    fi
+# utility function to check whether a command can be executed by the shell
+# see http://stackoverflow.com/questions/592620/how-to-check-if-a-program-exists-from-a-bash-script
+command_exists () {
+    command -v $1 >/dev/null 2>&1
 }
 
-check_command_and_run() {
-    check_command_and_run_anything $1 "$@"
+command_exists_or_warn () {
+    if ! command_exists $1 ; then
+        echo "Cannot find $1; please install it. Continuing without it." >&2
+        return 1
+    fi
 }
 
 is_cidr() {
@@ -124,7 +117,7 @@ create_bridge() {
         ip link set dev v${CONTAINER_IFNAME}du master $BRIDGE
         ip link del dev v${CONTAINER_IFNAME}du
         # disable offloading
-        check_command_and_run ethtool -K $BRIDGE tx off >/dev/null
+        if command_exists_or_warn ethtool; then ethtool -K $BRIDGE tx off >/dev/null; fi
         # Work around the situation where there are no rules allowing traffic
         # across our bridge. E.g. ufw
         add_iptables_rule filter FORWARD -i $BRIDGE -o $BRIDGE -j ACCEPT
@@ -205,7 +198,7 @@ connect_container_to_bridge() {
         return 1
     fi
 
-    if check_command_and_run ethtool -K $GUEST_IFNAME tx off >/dev/null &&
+    if { if command_exists_or_warn ethtool; then ethtool -K $GUEST_IFNAME tx off >/dev/null; fi } &&
         ip link set $LOCAL_IFNAME master $BRIDGE &&
         ip link set $LOCAL_IFNAME up &&
         ip link set $GUEST_IFNAME netns $NETNS ; then
@@ -224,7 +217,7 @@ launch() {
         return 1
     fi
     connect_container_to_bridge &&
-        check_command_and_run_anything ethtool ip netns exec $NETNS ethtool -K eth0 tx off >/dev/null &&
+        { if command_exists_or_warn ethtool ; then ip netns exec $NETNS ethtool -K eth0 tx off >/dev/null; fi } &&
         ip netns exec $NETNS ip link set $CONTAINER_IFNAME up
 }
 
@@ -552,7 +545,9 @@ case "$COMMAND" in
             echo "Weave is not running." >&2
         fi
         docker rm -f $CONTAINER_NAME >/dev/null 2>&1 || true
-        check_command_and_run conntrack -D -p udp --dport $PORT >/dev/null 2>&1 || true
+        if command_exists_or_warn conntrack; then
+            conntrack -D -p udp --dport $PORT >/dev/null 2>&1 || true
+        fi
         ;;
     stop-dns)
         [ $# -eq 0 ] || usage
@@ -567,7 +562,9 @@ case "$COMMAND" in
         docker kill  $DNS_CONTAINER_NAME >/dev/null 2>&1 || true
         docker rm -f $CONTAINER_NAME     >/dev/null 2>&1 || true
         docker rm -f $DNS_CONTAINER_NAME >/dev/null 2>&1 || true
-        check_command_and_run conntrack -D -p udp --dport $PORT >/dev/null 2>&1 || true
+        if command_exists_or_warn conntrack; then
+            conntrack -D -p udp --dport $PORT >/dev/null 2>&1 || true
+        fi
         destroy_bridge
         for LOCAL_IFNAME in $(ip link show | grep v${CONTAINER_IFNAME}pl | cut -d ' ' -f 2 | tr -d ':') ; do
             ip link del $LOCAL_IFNAME