89 lines
3.3 KiB
Python
89 lines
3.3 KiB
Python
"""
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Simple and navie mDNS implementation.
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Low level socket management to listen to mDNS queries and respond to _http._tcp.local service queries with constant name.
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"""
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import socket
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from dnslib import DNSRecord, DNSHeader, QTYPE, A, SRV, TXT, RR, PTR
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import dns.message
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multicast_group = "224.0.0.251"
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multicast_port = 5353
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interface_ip = "0.0.0.0"
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SERVICE_TO_ANNOUNCE = "toto"
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def main():
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sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
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sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 32)
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# See man socket(7)
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sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
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# sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
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sock.bind(("", multicast_port))
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# sock.setsockopt(socket.SOL_IP, socket.IP_ADD_MEMBERSHIP, socket.inet_aton(multicast_group) + socket.inet_aton(interface_ip))
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sock.setsockopt(
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socket.IPPROTO_IP, socket.IP_MULTICAST_IF, socket.inet_aton(interface_ip)
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)
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sock.setsockopt(
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socket.IPPROTO_IP,
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socket.IP_ADD_MEMBERSHIP,
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socket.inet_aton(multicast_group) + socket.inet_aton(interface_ip),
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)
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while True:
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received, sender = sock.recvfrom(1500)
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print(f"Received packet of {len(received)} bytes from {sender}")
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try:
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msg = dns.message.from_wire(received)
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except dns.exception.FormError:
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print("Not a valid DNS message")
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continue
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if msg.opcode() == dns.opcode.QUERY:
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for question in msg.question:
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if str(question.name) == "_http._tcp.local.":
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print(f"question name {type(msg)}")
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unicast_response = question.rdclass == 0x8001
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response = DNSRecord(DNSHeader(id=0, bitmap=0x8400))
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ptr = PTR(SERVICE_TO_ANNOUNCE + "._http._tcp.local")
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srv = SRV(target="toto.local", priority=10, port=80, weight=100)
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txt = TXT("path=/")
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a = A("192.168.1.21")
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response.add_answer(
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RR("_http._tcp.local", QTYPE.PTR, rdata=ptr, ttl=120)
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)
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response.add_ar(
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RR(
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SERVICE_TO_ANNOUNCE + "._http._tcp.local",
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QTYPE.SRV,
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rdata=srv,
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ttl=120,
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)
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)
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response.add_ar(
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RR(
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SERVICE_TO_ANNOUNCE + "._http._tcp.local",
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QTYPE.TXT,
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rdata=txt,
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ttl=120,
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)
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)
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response.add_ar(
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RR(SERVICE_TO_ANNOUNCE + ".local", QTYPE.A, rdata=a, ttl=120)
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)
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print(str(response))
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if unicast_response:
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print("Unicast response")
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sock.sendto(response.pack(), sender)
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else:
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print("Multicast response")
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sock.sendto(response.pack(), (multicast_group, multicast_port))
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print(f"Send response to {sender}")
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if __name__ == "__main__":
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main()
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