contrib/freeswitch_dialplan_dgsm.py: new fileosmith/dgsm

Add example script for the distributed GSM network, which resolves the
destination SIP servers of calls with osmo-mslookup-client and bridges
the calls accordingly.

Related: OS#4255
Change-Id: Ie4c310d2d726a72cba16503199a50b4d2177f5eb

1 files changed, 77 insertions, 0 deletions

diff --git a/contrib/freeswitch_dialplan_dgsm.py b/contrib/freeswitch_dialplan_dgsm.py
new file mode 100755
index 0000000..66f2d9a
--- /dev/null
+++ b/contrib/freeswitch_dialplan_dgsm.py
@@ -0,0 +1,77 @@
+#!/usr/bin/env python3
+"""
+SPDX-License-Identifier: AGPL-3.0-or-later
+Copyright 2019 sysmocom s.f.m.c GmbH <info@sysmocom.de>
+
+This is a freeswitch dialplan implementation, see:
+https://freeswitch.org/confluence/display/FREESWITCH/mod_python
+
+Find the right SIP server with mslookup (depending on the destination number)
+and bridge calls accordingly.
+"""
+import json
+import subprocess
+
+
+def query_mslookup(service_type, id, id_type='msisdn'):
+    query_str = '%s.%s.%s' % (service_type, id, id_type)
+    print('[dialplan-dgsm] mslookup: ' + query_str)
+
+    result_line = subprocess.check_output([
+        'osmo-mslookup-client', query_str, '-f', 'json'])
+    if isinstance(result_line, bytes):
+        result_line = result_line.decode('ascii')
+
+    print('[dialplan-dgsm] mslookup result: ' + result_line)
+    return json.loads(result_line)
+
+
+def handler(session, args):
+    """ Handle calls: bridge to the SIP server found with mslookup. """
+    print('[dialplan-dgsm] call handler')
+    msisdn = session.getVariable('destination_number')
+
+    # Run osmo-mslookup-client binary. We have also tried to directly call the
+    # C functions with ctypes but this has lead to hard-to-debug segfaults.
+    try:
+        result = query_mslookup("sip.voice", msisdn)
+
+        # This example only makes use of IPv4
+        if not result['v4']:
+            print('[dialplan-dgsm] no IPv4 result from mslookup')
+            session.hangup('UNALLOCATED_NUMBER')
+            return
+
+        sip_ip, sip_port = result['v4']
+        dial_str = 'sofia/internal/sip:{}@{}:{}'.format(
+            msisdn, sip_ip, sip_port)
+        print('[dialplan-dgsm] dial_str: ' + str(dial_str))
+
+        session.execute('bridge', dial_str)
+    except:
+        print('[dialplan-dgsm]: exception during call handler')
+        session.hangup('UNALLOCATED_NUMBER')
+
+
+def fsapi(session, stream, env, args):
+    """ Freeswitch refuses to load the module without this. """
+    stream.write(env.serialize())
+
+
+def main():
+    import argparse
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument('id', type=int)
+    parser.add_argument('-i', '--id-type', default='msisdn',
+                        help='default: "msisdn"')
+    parser.add_argument('-s', '--service', default='sip.voice',
+                        help='default: "sip.voice"')
+    args = parser.parse_args()
+
+    result = query_mslookup(args.service, args.id, args.id_type)
+    print(json.dumps(result))
+
+
+if __name__ == '__main__':
+    main()