Log network activity using tcpdump for nitb interface

Change-Id: I4c5d0e2d9857160f905e743517e744f1a06368af
diff --git a/src/osmo_gsm_tester/pcaprecorder.py b/src/osmo_gsm_tester/pcaprecorder.py
new file mode 100644
index 0000000..8a63b30
--- /dev/null
+++ b/src/osmo_gsm_tester/pcaprecorder.py
@@ -0,0 +1,59 @@
+# osmo_gsm_tester: specifics for running an osmo-nitb
+#
+# Copyright (C) 2016-2017 by sysmocom - s.f.m.c. GmbH
+#
+# Author: Pau Espin Pedrol <pespin@sysmocom.de>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import os
+import random
+import re
+import socket
+
+from . import log, util, config, template, process, osmo_ctrl
+
+class PcapRecorder(log.Origin):
+
+    def __init__(self, suite_run, run_dir, iface=None, addr=None):
+        self.suite_run = suite_run
+        self.run_dir = run_dir
+        self.iface = iface
+        if not self.iface:
+            self.iface = "any"
+        self.addr = addr
+        self.set_log_category(log.C_RUN)
+        self.set_name('pcap-recorder_%s' % self.iface)
+        self.start()
+
+    def start(self):
+        self.log('Recording pcap', self.run_dir, self.gen_filter())
+        dumpfile = os.path.join(os.path.abspath(self.run_dir), self.name() + ".pcap")
+        self.process = process.Process(self.name(), self.run_dir,
+                                       ('tcpdump', '-n',
+                                       '-i', self.iface,
+                                       '-w', dumpfile,
+                                       self.gen_filter())
+                                       )
+        self.suite_run.remember_to_stop(self.process)
+        self.process.launch()
+
+    def gen_filter(self):
+        filter = ""
+        if self.addr:
+            filter += 'host ' + self.addr
+        return filter
+
+    def running(self):
+        return not self.process.terminated()