gsmtap.py: send example msg using scapy

The GSM message appears in wireshark when sniffing on localhost

usb_application/gsmtap.py

@@ -0,0 +1,17 @@
+#!/usr/bin/env python
+
+from scapy.all import IP, UDP, sr1
+
+ip="127.0.0.1"
+port=4729
+sp=58621
+data=("\x02\x04\x04"+"\x00"*13+"\x9f\x16\xa0\xc0\x00\x00\x16", "\x9f\x16\xa0\xc0\x00\x00\x16")
+
+p=IP(dst=ip, src=ip)/UDP(sport=sp, dport=port)/data[0]
+
+if p:
+    p.show()
+
+ans = sr1(p, timeout=2)
+if ans:
+    print(a)