102 lines
4.0 KiB
Python
102 lines
4.0 KiB
Python
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#!/usr/bin/env python3
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"""
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Pulls a capture off the ITS-G5 receiver's in-memory pcap buffer over the existing USB serial
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connection and saves it as a real .pcap file on this machine.
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Requires the firmware to be built with:
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Example Configuration -> Select destination to store pcap file -> Memory
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Usage (typical):
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1. Close idf.py monitor (only one program can hold the COM port at a time).
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2. Run a capture on the device: `sniffer -P` ... let it run ... `sniffer --stop`
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3. python dump_pcap.py COM5
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The device has no access to this computer's filesystem, so it can't write here directly. Instead,
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`pcap --dump` streams the raw pcap bytes back over the same serial link, wrapped in plain-text
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markers ("===PCAP-DUMP-START:<len>===" ... raw bytes ... "===PCAP-DUMP-END==="). This script finds
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those markers and writes just the raw bytes out as a .pcap file.
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Install dependency once: pip install pyserial
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"""
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import argparse
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import datetime
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import re
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import sys
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try:
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import serial
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except ImportError:
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print("Missing dependency. Install it with: pip install pyserial", file=sys.stderr)
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sys.exit(1)
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START_RE = re.compile(rb"===PCAP-DUMP-START:(\d+)===\n")
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END_MARKER = b"\n===PCAP-DUMP-END===\n"
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def main():
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parser = argparse.ArgumentParser(description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter)
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parser.add_argument("port", help="Serial port the device is on, e.g. COM5")
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parser.add_argument("-b", "--baud", type=int, default=115200, help="Baud rate (default: 115200)")
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parser.add_argument("-o", "--outdir", default="recordings", help="Output directory (default: ./recordings)")
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parser.add_argument("-t", "--timeout", type=float, default=15.0, help="Seconds to wait for the dump to start")
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args = parser.parse_args()
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import os
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os.makedirs(args.outdir, exist_ok=True)
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print(f"Opening {args.port} @ {args.baud}...")
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with serial.Serial(args.port, args.baud, timeout=1) as ser:
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# Nudge the console in case there's stale input, then request the dump.
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ser.reset_input_buffer()
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ser.write(b"\r\n")
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ser.write(b"pcap -f dump --dump\r\n")
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print("Waiting for dump to start...")
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buf = b""
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match = None
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deadline = datetime.datetime.now() + datetime.timedelta(seconds=args.timeout)
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while datetime.datetime.now() < deadline:
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chunk = ser.read(256)
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if chunk:
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buf += chunk
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match = START_RE.search(buf)
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if match:
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break
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if not match:
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print("Timed out waiting for '===PCAP-DUMP-START:...===' marker.\n"
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"Check that: the firmware is built with the Memory pcap destination, a capture was\n"
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"actually taken ('sniffer -P' then 'sniffer --stop'), and no other program (like\n"
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"idf.py monitor) is holding the serial port open.", file=sys.stderr)
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sys.exit(1)
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length = int(match.group(1))
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print(f"Dump starting, {length} bytes expected.")
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# Anything after the marker in our buffer is already part of the payload.
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payload = buf[match.end():]
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remaining = length - len(payload)
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while remaining > 0:
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chunk = ser.read(min(remaining, 4096))
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if not chunk:
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print(f"Serial read timed out with {remaining} bytes still missing.", file=sys.stderr)
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sys.exit(1)
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payload += chunk
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remaining -= len(chunk)
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# Drain (and sanity-check) the trailing end marker, but don't fail hard if it's not exact.
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tail = ser.read(len(END_MARKER))
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if tail != END_MARKER:
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print("Warning: end marker didn't match exactly - payload may still be fine.", file=sys.stderr)
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timestamp = datetime.datetime.now().strftime("%Y%m%d_%H%M%S")
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outpath = os.path.join(args.outdir, f"capture_{timestamp}.pcap")
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with open(outpath, "wb") as f:
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f.write(payload)
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print(f"Saved {len(payload)} bytes to {outpath}")
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if __name__ == "__main__":
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main()
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