Use dumpcap for ttcn3-tcpdump-*.sh if available

Check if dumpcap is installed (either as suid or with appropriate
capabilities) and use it for packet capture instead of
'sudo tcpdump' if available. This makes it easier to use TTCN-3
testsuite as regular user without altering sudoers.

Change-Id: I77df04d51a469c924cf727f0596cc33565909746

ttcn3-tcpdump-start.sh

@@ -2,6 +2,7 @@
 
 PIDFILE=/tmp/dumper.pid
 TCPDUMP=/usr/sbin/tcpdump
+DUMPCAP=/usr/bin/dumpcap
 TESTCASE=$1
 
 echo "------ $TESTCASE ------"
@@ -23,6 +24,21 @@ else
 # "laforge ALL=NOPASSWD: /usr/sbin/tcpdump, /bin/kill" in your sudoers file
 	CMD="sudo $TCPDUMP -U"
 fi
+
+if [ -x $DUMPCAP ]; then
+    CAP_ERR="1"
+    if [ -x /sbin/setcap ]; then
+	# N. B: this check requires libcap2-bin package
+	setcap -q -v 'cap_net_admin,cap_net_raw=pie' $DUMPCAP
+	CAP_ERR="$?"
+    fi
+    if [ -u $DUMPCAP -o "$CAP_ERR" = "0" ]; then
+	CMD="$DUMPCAP -q"
+    else
+ 	echo "NOTE: unable to use dumpcap due to missing capabilities or suid bit"
+    fi
+fi
+
 $CMD -s 1500 -n -i any -w "$TTCN3_PCAP_PATH/$TESTCASE.pcap" >$TTCN3_PCAP_PATH/$TESTCASE.pcap.stdout 2>&1 &
 PID=$!
 echo $PID > $PIDFILE

ttcn3-tcpdump-stop.sh

@@ -32,7 +32,8 @@ do
 done
 
 if [ -e $PIDFILE ]; then
-	if [ "$(id -u)" = "0" ]; then
+        DUMPER="$(ps -q "$(cat "$PIDFILE")" -o comm=)"
+	if [ "$DUMPER" != "sudo" ]; then
 		kill "$(cat "$PIDFILE")"
 	else
 	# NOTE: This requires you to be root or something like