55 lines
2.5 KiB
Python
55 lines
2.5 KiB
Python
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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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(socket.IPPROTO_IP, socket.IP_MULTICAST_IF, socket.inet_aton(interface_ip))
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sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, socket.inet_aton(multicast_group) + socket.inet_aton(interface_ip))
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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("toto._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(RR('_http._tcp.local', QTYPE.PTR, rdata = ptr, ttl=120))
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response.add_ar(RR('toto._http._tcp.local', QTYPE.SRV, rdata = srv, ttl=120))
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response.add_ar(RR('toto._http._tcp.local', QTYPE.TXT, rdata = txt, ttl=120))
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response.add_ar(RR('toto.local', QTYPE.A, rdata = a, ttl=120))
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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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