Introduce doc/examples/ directory

It contains simple usual setups to get started with osmo-gsm-tester,
such as creating a 4G network using srsLTE or a 2G network using the
osmocom stack (+ ofono modems).

Change-Id: I55d5b1152da201799af21a77ef6c562f97bd94fc
diff --git a/doc/examples/4g_srsLTE/suites/4g/iperf3_dl.py b/doc/examples/4g_srsLTE/suites/4g/iperf3_dl.py
new file mode 100755
index 0000000..88ae82d
--- /dev/null
+++ b/doc/examples/4g_srsLTE/suites/4g/iperf3_dl.py
@@ -0,0 +1,49 @@
+#!/usr/bin/env python3
+from osmo_gsm_tester.testenv import *
+
+def print_result_node(result, node_str):
+    sent = result['end']['sum_sent']
+    recv = result['end']['sum_received']
+    print("Result %s:" % node_str)
+    print("\tSEND: %d KB, %d kbps, %d seconds (%s retrans)" % (sent['bytes']/1000, sent['bits_per_second']/1000, sent['seconds'], str(sent.get('retransmits', 'unknown'))))
+    print("\tRECV: %d KB, %d kbps, %d seconds" % (recv['bytes']/1000, recv['bits_per_second']/1000, recv['seconds']))
+
+def print_results(cli_res, srv_res):
+    print_result_node(cli_res, 'client')
+    print_result_node(srv_res, 'server')
+
+epc = suite.epc()
+enb = suite.enb()
+ue = suite.modem()
+iperf3srv = suite.iperf3srv({'addr': epc.tun_addr()})
+iperf3srv.set_run_node(epc.run_node())
+iperf3cli = iperf3srv.create_client()
+iperf3cli.set_run_node(ue.run_node())
+
+epc.subscriber_add(ue)
+epc.start()
+enb.ue_add(ue)
+enb.start(epc)
+
+print('waiting for ENB to connect to EPC...')
+wait(epc.enb_is_connected, enb)
+print('ENB is connected to EPC')
+
+ue.connect(enb)
+
+iperf3srv.start()
+proc = iperf3cli.prepare_test_proc(True, ue.netns())
+
+print('waiting for UE to attach...')
+wait(ue.is_connected, None)
+print('UE is attached')
+
+print("Running iperf3 client to %s through %s" % (str(iperf3cli), ue.netns()))
+proc.launch_sync()
+iperf3srv.stop()
+print_results(iperf3cli.get_results(), iperf3srv.get_results())
+
+max_rate = enb.ue_max_rate(downlink=True)
+res_str = ue.verify_metric(max_rate * 0.8, operation='avg', metric='dl_brate', criterion='gt')
+print(res_str)
+test.set_report_stdout(res_str)