mrcharles
33827de0dc
Split per O&M lane work order. Full history: KNEL/PFVCluster. https://projects.knownelement.com/issues/769#note-4152
102 lines
3.1 KiB
Python
102 lines
3.1 KiB
Python
#!/usr/bin/env python3
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"""mdns-browse: one-shot multicast mDNS enumeration from this vantage.
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Sends PTR queries for the DNS-SD service-enumeration name plus common
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service types, listens briefly, prints every answer record. Stdlib only.
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Diagnostic tool for #619 (WiFi-side multicast reachability)."""
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import socket
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import struct
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import sys
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import time
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MDNS_GROUP = "224.0.0.251"
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MDNS_PORT = 5353
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LISTEN_SECONDS = float(sys.argv[1]) if len(sys.argv) > 1 else 6.0
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TYPES = {
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1: "A", 28: "AAAA", 12: "PTR", 16: "TXT", 33: "SRV", 47: "NONE",
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}
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QUERIES = [
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"_services._dns-sd._udp.local",
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"_hap._tcp.local",
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"_airplay._tcp.local",
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"_googlecast._tcp.local",
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]
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def encode_name(name):
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out = b""
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for part in name.split("."):
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out += bytes([len(part)]) + part.encode("latin1")
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return out + b"\x00"
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def read_name(data, off):
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parts = []
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seen = set()
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while True:
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if off in seen or len(seen) > 64:
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return ".".join(parts), off
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seen.add(off)
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length = data[off]
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if length == 0:
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off += 1
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break
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if length & 0xC0:
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ptr = struct.unpack(">H", data[off:off + 2])[0] & 0x3FFF
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parts.append(read_name(data, ptr)[0])
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off += 2
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break
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parts.append(data[off + 1:off + 1 + length].decode("latin1"))
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off += 1 + length
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return ".".join(parts), off
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def build_query(names):
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packet = struct.pack(">HHHHHH", 0, 0, len(names), 0, 0, 0)
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for name in names:
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packet += encode_name(name) + struct.pack(">HH", 12, 1)
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return packet
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def main():
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sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
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sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
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sock.bind(("", MDNS_PORT))
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mreq = socket.inet_aton(MDNS_GROUP) + socket.inet_aton("0.0.0.0")
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sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)
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sock.settimeout(0.5)
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sock.sendto(build_query(QUERIES), (MDNS_GROUP, MDNS_PORT))
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deadline = time.time() + LISTEN_SECONDS
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found = set()
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while time.time() < deadline:
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try:
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data, addr = sock.recvfrom(16384)
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except socket.timeout:
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continue
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an = struct.unpack(">H", data[6:8])[0]
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off = 12
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qd = struct.unpack(">H", data[4:6])[0]
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try:
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for _ in range(qd):
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_, off = read_name(data, off)
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off += 4
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for _ in range(an):
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name, name_end = read_name(data, off)
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rtype, _rclass, ttl, rlen = struct.unpack(
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">HHIH", data[name_end:name_end + 10])
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detail = ""
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if rtype == 12:
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detail = " -> " + read_name(data, name_end + 10)[0]
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found.add((TYPES.get(rtype, rtype), name, detail, addr[0]))
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off = name_end + 10 + rlen
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except (IndexError, struct.error):
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continue
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for rtype, name, detail, src in sorted(found):
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print(f"{src:15} {rtype:5} {name}{detail}")
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print(f"-- {len(found)} records from {LISTEN_SECONDS}s listen --")
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if __name__ == "__main__":
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main()
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