diff --git a/testing/do-tests b/testing/do-tests
index 992f3f5d89..d0d1ead887 100755
--- a/testing/do-tests
+++ b/testing/do-tests
@@ -111,6 +111,13 @@ done
 [ -f $SHAREDDIR/.strongswan-version ] && SWANVERSION=`cat $SHAREDDIR/.strongswan-version`
 KERNELVERSION=`ssh $SSHCONF root@\$ipv4_winnetou uname -r 2>/dev/null`
 
+# check if tcpdump supports --immediate-mode
+ssh $SSHCONF root@$ipv4_winnetou tcpdump --immediate-mode -c 1 >/dev/null 2>&1
+if [ $? -eq 0 ]
+then
+	TCPDUMP_IM=--immediate-mode
+fi
+
 ##############################################################################
 # create header for the results html file
 #
@@ -359,7 +366,7 @@ do
 	    do
 		host=`echo $host_iface | awk -F ":" '{print $1}'`
 		iface=`echo $host_iface | awk -F ":" '{if ($2 != "") { print $2 } else { printf("eth0") }}'`
-		tcpdump_cmd="tcpdump -i $iface not port ssh and not port domain > /tmp/tcpdump.log 2>&1 &"
+		tcpdump_cmd="tcpdump -l $TCPDUMP_IM -i $iface not port ssh and not port domain >/tmp/tcpdump.log 2>/tmp/tcpdump.err.log &"
 		echo "${host}# $tcpdump_cmd" >> $CONSOLE_LOG
 		ssh $SSHCONF root@`eval echo \\\$ipv4_$host '$tcpdump_cmd'`
 		eval TDUP_${host}="true"
@@ -417,6 +424,8 @@ do
 	#
 
 	function stop_tcpdump {
+	    # wait for packets to get processed, but don't wait longer than 1s
+	    eval ssh $SSHCONF root@\$ipv4_${1} "\"i=100; while [ \\\$i -gt 0 ]; do pkill -USR1 tcpdump; tail -1 /tmp/tcpdump.err.log | perl -n -e '/(\\d+).*?(\\d+)/; exit (\\\$1 == \\\$2)' || break; sleep 0.01; i=\\\$((\\\$i-1)); done;\""
 	    echo "${1}# killall tcpdump" >> $CONSOLE_LOG
 	    eval ssh $SSHCONF root@\$ipv4_${1} "\"killall tcpdump; while true; do killall -q -0 tcpdump || break; sleep 0.01; done;\""
 	    eval TDUP_${1}="false"