mwan3: add back support for iputils ping

With the new wrapper code, we can override the broken binding behavior of
iputils ping v20101006.

Signed-off-by: Aaron Goodman <aaronjg@stanford.edu>

net/mwan3/files/usr/sbin/mwan3track

@@ -6,7 +6,6 @@
 
 INTERFACE=""
 DEVICE=""
-PING="/bin/ping"
 
 IFDOWN_EVENT=0
 IFUP_EVENT=0
@@ -47,10 +46,19 @@ if_up() {
 validate_track_method() {
 	case "$1" in
 		ping)
-			[ -x "$PING" ] || {
-				LOG warn "Missing ping. Please enable ping util and recompile busybox."
+			if [ -x "/usr/bin/ping" ] && [ "$(/usr/bin/ping -V | grep -o '[0-9]*$')" -gt 20150519 ]; then
+				# -4 option added in iputils c3e68ac6
+				PING="/usr/bin/ping -${FAMILY#ipv}"
+			elif [ "$FAMILY" = "ipv6" ] && [ -x "/usr/bin/ping6" ]; then
+				PING="/usr/bin/ping6"
+			elif [ "$FAMILY" = "ipv4" ] && [ -x "/usr/bin/ping" ]; then
+				PING="/usr/bin/ping"
+			elif [ -x "/bin/ping" ]; then
+				PING="/bin/ping -${FAMILY#ipv}"
+			else
+				LOG warn "Missing ping. Please enable BUSYBOX_DEFAULT_PING and recompile busybox or install iputils-ping package."
 				return 1
-			}
+			fi
 			;;
 		arping)
 			command -v arping 1>/dev/null 2>&1 || {
@@ -218,12 +226,12 @@ main() {
 				case "$track_method" in
 					ping)
 						if [ $check_quality -eq 0 ]; then
-							WRAP $PING -${FAMILY#ipv} -c $count -W $timeout -s $size -t $max_ttl -q $track_ip &> /dev/null &
+							WRAP $PING -c $count -W $timeout -s $size -t $max_ttl -q $track_ip &> /dev/null &
 							TRACK_PID=$!
 							wait $TRACK_PID
 							result=$?
 						else
-							WRAP $PING -${family#ipv} -c $count -W $timeout -s $size -t $max_ttl -q $track_ip 2>/dev/null > $TRACK_OUTPUT &
+							WRAP $PING -c $count -W $timeout -s $size -t $max_ttl -q $track_ip 2>/dev/null > $TRACK_OUTPUT &
 							TRACK_PID=$!
 							wait $TRACK_PID
 							ping_status=$?