runqemu fixes about iptables rules and preconfigured tap

index 8b8c5a4..8f66cfa2 100755
@@ -50,3 +50,17 @@ if [ ! -e "$TUNCTL" ]; then
 fi
 
 $TUNCTL -d $TAP
+
+# cleanup the remaining iptables rules
+IPTABLES=`which iptables 2> /dev/null`
+if [ "x$IPTABLES" = "x" ]; then
+	IPTABLES=/sbin/iptables
+fi
+if [ ! -x "$IPTABLES" ]; then
+	echo "$IPTABLES cannot be executed"
+	exit 1
+fi
+n=$[ (`echo $TAP | sed 's/tap//'` * 2) + 1 ]
+dest=$[ (`echo $TAP | sed 's/tap//'` * 2) + 2 ]
+$IPTABLES -D POSTROUTING -t nat -j MASQUERADE -s 192.168.7.$n/32
+$IPTABLES -D POSTROUTING -t nat -j MASQUERADE -s 192.168.7.$dest/32

index 8a6e551..8165e13 100755
@@ -175,12 +175,14 @@ else
         POSSIBLE=`$IFCONFIG link | grep 'tap' | awk '{print $2}' | sed s/://`
         TAP=""
         LOCKFILE=""
+        USE_PRECONF_TAP="no"
         for tap in $POSSIBLE; do
             LOCKFILE="$LOCKDIR/$tap"
             echo "Acquiring lockfile for $tap..."
             acquire_lock $LOCKFILE
             if [ $? -eq 0 ]; then
                 TAP=$tap
+                USE_PRECONF_TAP="yes"
                 break
             fi
         done

@@ -215,7 +217,7 @@ else
         fi
 
         cleanup() {
-            if [ ! -e "$NOSUDO_FLAG" ]; then
+            if [ ! -e "$NOSUDO_FLAG" -a "$USE_PRECONF_TAP" = "no" ]; then
                 # Redirect stderr since we could see a LD_PRELOAD warning here if pseudo is loaded
                 # but inactive. This looks scary but is harmless
                 sudo $QEMUIFDOWN $TAP $OECORE_NATIVE_SYSROOT 2> /dev/null

index 8165e13..3f8674c 100755
@@ -135,15 +135,12 @@ else
                 return 1
             fi
 
-            touch $lockfile.lock
-            exec 8>$lockfile.lock
-            flock -n -x 8
-            if [ $? -ne 0 ]; then
-                exec 8>&-
+            if [ -e $lockfile.lock ]; then
                 return 1
+            else
+                touch $lockfile.lock
+                return 0
             fi
-
-            return 0
         }
 
         release_lock() {

@@ -154,7 +151,6 @@ else
             fi
 
             rm -f $lockfile.lock
-            exec  8>&-
         }
 
         LOCKDIR="/tmp/qemu-tap-locks"

@@ -184,6 +180,8 @@ else
                 TAP=$tap
                 USE_PRECONF_TAP="yes"
                 break
+            else
+                echo "Skipping $tap as it's locked by $LOCKFILE.lock"
             fi
         done
 

index 3f8674c..d6ceb28 100755
@@ -211,7 +211,7 @@ else
                 TAP=$tap
             fi 
         else
-            echo "Using preconfigured tap device '$TAP'"
+            echo "Using preconfigured tap device '$TAP'. If this is not intended, create $LOCKFILE.lock to make runqemu skip $TAP."
         fi
 
         cleanup() {