re-organize configuration files; add tcpdump integration

Let's make sure we share common configuration between the test
suites and split the config file into a "default" part which is
used (but not copied) in the Docker images, and a "local" part
which is basically those overrides that the user (or docker image)
wants to do from the default.

Change-Id: I3db452e24e5238aa05254d903739c64d202e61db
diff --git a/ttcn3-tcpdump-start.sh b/ttcn3-tcpdump-start.sh
new file mode 100755
index 0000000..1349cd7
--- /dev/null
+++ b/ttcn3-tcpdump-start.sh
@@ -0,0 +1,24 @@
+#!/bin/sh
+
+PIDFILE=/tmp/tcpdump.pid
+TESTCASE=$1
+
+if [ "z$TTCN3_PCAP_PATH" = "z" ]; then
+	TTCN3_PCAP_PATH=/tmp
+fi
+
+if [ -e $PIDFILE ]; then
+	kill "$(cat "$PIDFILE")"
+	rm $PIDFILE
+fi
+
+# NOTE: This requires you to be root or something like
+# "laforge ALL=NOPASSWD: /usr/sbin/tcpdump, /bin/kill" in your sudoers file
+if [ "$(id -u)" = "0" ]; then
+	CMD=/usr/sbin/tcpdump
+else
+	CMD="sudo /usr/sbin/tcpdump"
+fi
+$CMD -s 0 -n -i any -w "$TTCN3_PCAP_PATH/$TESTCASE.pcap" >/dev/null 2>&1 &
+PID=$!
+echo $PID > $PIDFILE