catarrh
cb4c07f3c2
pcap.py: LINKTYPE_GSMTAP (155) was wrong — 155 is DLT_USER8, so Wireshark showed 'USER 8 / DLT=155'. Now write Ethernet-encapsulated PCAP (LINKTYPE 1): each GSMTAP message wrapped in Ethernet + IPv4 + UDP (port 4729), with correct checksums — matching a real tcpdump capture of GSMTAP-over-UDP and how Wireshark's gsmtap dissector is keyed. gsmtap.py: GSMTAP_TYPE_SIM was 0x07 (WiMAX burst) — corrected to 0x04; GSMTAP_SIM_APDU was 0x02 (PPS req) — corrected to 0x00; added PPS_REQ/ PPS_RSP. These match libosmocore/Wireshark packet-gsmtap.h. Verified with tshark: PCAP now decodes as GSM SIM (SELECT/STATUS/ATR) instead of 'USER 8'. tests: pcap tests assert Ethernet linktype + framing + GSMTAP payload.
102 lines
3.1 KiB
Python
102 lines
3.1 KiB
Python
"""GSMTAP UDP sender for Wireshark integration.
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GSMTAP header format (big-endian, 16 bytes). Based on libosmocore's gsmtap.h.
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"""
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import struct
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import socket
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GSMTAP_VERSION = 0x02
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GSMTAP_HDR_LEN = 4 # in 32-bit words (16 bytes)
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GSMTAP_TYPE_SIM = 0x04
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GSMTAP_SIM_APDU = 0x00
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GSMTAP_SIM_ATR = 0x01
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GSMTAP_SIM_PPS_REQ = 0x02
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GSMTAP_SIM_PPS_RSP = 0x03
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GSMTAP_UDP_PORT = 4729
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_GSMTAP_HDR_FMT = '!BBBBHBBIBBBB' # 16 bytes, big-endian
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_GSMTAP_HDR_SIZE = struct.calcsize(_GSMTAP_HDR_FMT)
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def build_gsmtap_packet(sub_type, data, slot_nr=0):
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"""Build a GSMTAP packet as bytes.
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Returns *gsmtap_hdr* + *data* as a single bytes object.
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"""
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hdr = struct.pack(
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_GSMTAP_HDR_FMT,
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GSMTAP_VERSION, # version
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GSMTAP_HDR_LEN, # hdr_len (in 32-bit words)
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GSMTAP_TYPE_SIM, # type
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0, # timeslot
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0, # arfcn
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0, # noise_db
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0, # signal_db
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0, # frame_number
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sub_type, # sub_type
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0, # antenna_nr
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slot_nr, # sub_slot
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0, # res
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)
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return hdr + data
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class GsmtapSender:
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"""Send ATR/APDU data as GSMTAP UDP packets."""
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def __init__(self, host='127.0.0.1', port=GSMTAP_UDP_PORT):
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self._addr = (host, port)
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self._sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
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def send_atr(self, data, slot_nr=0):
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packet = build_gsmtap_packet(GSMTAP_SIM_ATR, data, slot_nr)
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self._sock.sendto(packet, self._addr)
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def send_apdu(self, data, slot_nr=0):
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packet = build_gsmtap_packet(GSMTAP_SIM_APDU, data, slot_nr)
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self._sock.sendto(packet, self._addr)
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def close(self):
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self._sock.close()
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class GsmtapReceiver:
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"""Receive GSMTAP-SIM packets over UDP (compatible with simtrace2-sniff)."""
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def __init__(self, bind_ip='127.0.0.1', bind_port=GSMTAP_UDP_PORT):
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self._sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
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self._sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
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self._sock.bind((bind_ip, bind_port))
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self._sock.settimeout(1.0)
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def read_packet(self):
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"""Block until a GSMTAP-SIM packet arrives.
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Returns ``(sub_type, data)`` on success or ``(None, None)``
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on timeout. *sub_type* is ``GSMTAP_SIM_ATR`` or ``GSMTAP_SIM_APDU``.
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Raises ``ValueError`` for non-SIM or unknown GSMTAP packets.
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"""
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try:
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packet, addr = self._sock.recvfrom(65536)
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except socket.timeout:
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return None, None
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if len(packet) < _GSMTAP_HDR_SIZE:
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raise ValueError(f'GSMTAP packet too short: {len(packet)} bytes')
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(version, hdr_len, pkt_type, _timeslot, _arfcn, _noise, _signal,
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_frame, sub_type, _antenna, sub_slot, _res) = \
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struct.unpack(_GSMTAP_HDR_FMT, packet[:_GSMTAP_HDR_SIZE])
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if pkt_type != GSMTAP_TYPE_SIM:
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raise ValueError(f'Not a GSMTAP SIM packet (type={pkt_type})')
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data = packet[_GSMTAP_HDR_SIZE:]
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return sub_type, data
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def close(self):
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self._sock.close()
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