enb: add optional gtp_bind_addr paramter to enb class

this allows to optionally specify a the GTP bind_address for a enb object
in the resources.conf

this address is then used for binding the listening socket for gtp connections
which, in turn, allows to run the enb and epc on the same host.

when gtp_bind_addr is not specified, addr is used by default

this is especially useful if eNB and EPC run on the same host
and ZMQ is used for RF between eNB and UE. Two eNB addresses
are needed in this case, one bind address and one "remote-accessable"
address for the UEs ZMQ radio to connect to

Change-Id: I4fe38f31401428ed3e74e1d0b64960f0af122d37

src/osmo_gsm_tester/obj/enb.py

@@ -32,6 +32,9 @@ class eNodeB(log.Origin, metaclass=ABCMeta):
         self._addr = conf.get('addr', None)
         if self._addr is None:
             raise log.Error('addr not set')
+        self._gtp_bind_addr = conf.get('gtp_bind_addr', None)
+        if self._gtp_bind_addr is None:
+            self._gtp_bind_addr = self._addr
         self.set_name('%s_%s' % (name, self._addr))
         self._txmode = 0
         self._num_prb = 0
@@ -52,6 +55,7 @@ class eNodeB(log.Origin, metaclass=ABCMeta):
         config.overlay(values, dict(enb={ 'num_ports': self.num_ports() }))
         assert self._epc is not None
         config.overlay(values, dict(enb={ 'mme_addr': self._epc.addr() }))
+        config.overlay(values, dict(enb={ 'gtp_bind_addr': self._gtp_bind_addr }))
         return values
 
     def num_ports(self):

src/osmo_gsm_tester/resource.py

@@ -88,6 +88,7 @@ RESOURCES_SCHEMA = {
         'enb[].type': schema.STR,
         'enb[].remote_user': schema.STR,
         'enb[].addr': schema.IPV4,
+        'enb[].gtp_bind_addr': schema.IPV4,
         'enb[].num_prb': schema.UINT,
         'enb[].transmission_mode': schema.LTE_TRANSMISSION_MODE,
         'enb[].num_cells': schema.UINT,

src/osmo_gsm_tester/templates/amarisoft_enb.cfg.tmpl

@@ -48,7 +48,7 @@
   ],
   /* GTP bind address (=address of the ethernet interface connected to
      the MME). Must be modified if the MME runs on a different host. */
-  gtp_addr: "${enb.addr}",
+  gtp_addr: "${enb.gtp_bind_addr}",
 
   /* high 20 bits of SIB1.cellIdentifier */
   enb_id: 0x19B,

src/osmo_gsm_tester/templates/srsenb.conf.tmpl

@@ -23,7 +23,7 @@ enb_id = 0x19B
 mcc = ${enb.mcc}
 mnc = ${enb.mnc}
 mme_addr = ${enb.mme_addr}
-gtp_bind_addr = ${enb.addr}
+gtp_bind_addr = ${enb.gtp_bind_addr}
 s1c_bind_addr = ${enb.addr}
 n_prb = ${enb.num_prb}
 tm = ${enb.transmission_mode}