added GTPping program to answer GTPU Ping frames

Author: bjoern-r

GTPping.py

@@ -0,0 +1,110 @@
+
+# Author: Bjoern Riemer
+# simple program to answer GTP Ping messages used in GTPU 
+
+import os
+import signal
+from struct import pack, unpack
+from threading import Thread
+from socket import socket, timeout, error, \
+    ntohs, htons, inet_aton, inet_ntoa, \
+    AF_PACKET, SOCK_RAW, AF_INET, SOCK_DGRAM, SOL_SOCKET, SO_REUSEADDR
+#from libmich.mobnet.utils import log
+
+def threadit(f, *args, **kwargs):
+    th = Thread(target=f, args=args, kwargs=kwargs)
+    th.start()
+    return th
+
+class GTPping(object):
+    '''
+    GTPU ping handler
+    '''
+    #
+    # verbosity level: list of log types to display when calling
+    # self._log(logtype, msg)
+    DEBUG = ('ERR', 'WNG', 'INF', 'DBG')
+    #
+    # packet buffer space (over MTU...)
+    BUFLEN = 2048
+
+    INT_IP = '0.0.0.0'
+    INT_PORT = 2152
+
+    def __init__(self):
+        #
+        # create an UDP socket on the RNC / eNobeB side, on port 2152
+        self.int_sk = socket(AF_INET, SOCK_DGRAM)
+        # configure timeout, binding and rebinding on same address
+        #self.int_sk.settimeout(0.003)
+        #self.int_sk.setblocking(0)
+        self.int_sk.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1)
+        self.int_sk.bind((self.INT_IP, self.INT_PORT))
+        #
+        # interrupt handler
+        def sigint_handler(signum, frame):
+            self._log('INF', 'CTRL+C caught')
+            self.stop()
+        #signal.signal(signal.SIGINT, sigint_handler)
+        #
+        # and start listening and transferring packets in background
+        self._listening = True
+        self._listener_t = threadit(self.listen)
+        self._log('INF', 'GTPU handler started')
+
+
+    def _log(self, logtype='DBG', msg=''):
+        # logtype: 'ERR', 'WNG', 'INF', 'DBG'
+        if logtype in self.DEBUG:
+            #log('[{0}] [GTPUd] {1}'.format(logtype, msg))
+            print('[{0}] [GTPUd] {1}'.format(logtype, msg))
+
+    def listen(self):
+        while self._listening:
+            try:
+                (bufint, from_address) = self.int_sk.recvfrom(self.BUFLEN)
+            except timeout:
+                # nothing to read anymore
+                self._log('INF', 'read timeout')
+                pass
+            except error as err:
+                self._log('ERR', 'internal network IF error '\
+                          '(recv): {0}'\
+                          .format(err))
+                self.stop()
+            else:
+                self.handle_gtp_ping(bufint,from_address)
+
+    def stop(self):
+        # stop local GTPU handler
+        if self._listening:
+            self._listening = False
+            sleep(self.SELECT_TO * 2)
+            try:
+                # closing sockets
+                self.int_sk.close()
+            except Exception as err:
+                self._log('ERR', 'socket error: {0}'.format(err))
+
+    def handle_gtp_ping(self, buf='\0', from_address=None):
+        # extract the GTP header
+        try:
+            flags, msgtype, msglen, teid, seq = unpack('>BBHIH', buf[:10])
+        except:
+            self._log('WNG', 'invalid GTP packet')
+            return
+        if msgtype == 0x01:
+            self._log('INF', "got GTP ping seq=%d teid=%d" % (seq,teid))
+            if flags & 0x02:
+                pass
+            try:
+                gtphdr = pack('>BBHIH', flags, 0x02, msglen, teid, seq)
+                ret = self.int_sk.sendto(gtphdr+buf[10:], from_address)
+            except Exception as err:
+                self._log('ERR', 'internal network IF error (sendto): {0}'.format(err))
+        else:
+            #self._log('DBG', "packet is not GTP ping")
+            pass
+
+if __name__ == '__main__':
+    gtpping = GTPping()