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Alexandre RIO
2025-12-22 13:57:56 +01:00
parent 4cf8499c32
commit b6a0322cdd
3 changed files with 53 additions and 15 deletions
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60
main.py
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@@ -1,3 +1,9 @@
"""
Simple and navie mDNS implementation.
Low level socket management to listen to mDNS queries and respond to _http._tcp.local service queries with constant name.
"""
import socket
from dnslib import DNSRecord, DNSHeader, QTYPE, A, SRV, TXT, RR, PTR
import dns.message
@@ -6,21 +12,30 @@ multicast_group = "224.0.0.251"
multicast_port = 5353
interface_ip = "0.0.0.0"
SERVICE_TO_ANNOUNCE = "toto"
def main():
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 32)
# See man socket(7)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
#sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
# sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
sock.bind(("", multicast_port))
# sock.setsockopt(socket.SOL_IP, socket.IP_ADD_MEMBERSHIP, socket.inet_aton(multicast_group) + socket.inet_aton(interface_ip))
sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_IF, socket.inet_aton(interface_ip))
sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, socket.inet_aton(multicast_group) + socket.inet_aton(interface_ip))
sock.setsockopt(
socket.IPPROTO_IP, socket.IP_MULTICAST_IF, socket.inet_aton(interface_ip)
)
sock.setsockopt(
socket.IPPROTO_IP,
socket.IP_ADD_MEMBERSHIP,
socket.inet_aton(multicast_group) + socket.inet_aton(interface_ip),
)
while True:
received, sender = sock.recvfrom(1500)
print(f'Received packet of {len(received)} bytes from {sender}')
print(f"Received packet of {len(received)} bytes from {sender}")
try:
msg = dns.message.from_wire(received)
except dns.exception.FormError:
@@ -29,18 +44,36 @@ def main():
if msg.opcode() == dns.opcode.QUERY:
for question in msg.question:
if str(question.name) == '_http._tcp.local.':
if str(question.name) == "_http._tcp.local.":
print(f"question name {type(msg)}")
unicast_response = question.rdclass == 0x8001
response = DNSRecord(DNSHeader(id = 0, bitmap=0x8400))
ptr = PTR("toto._http._tcp.local")
response = DNSRecord(DNSHeader(id=0, bitmap=0x8400))
ptr = PTR(SERVICE_TO_ANNOUNCE + "._http._tcp.local")
srv = SRV(target="toto.local", priority=10, port=80, weight=100)
txt = TXT("path=/")
a = A("192.168.1.21")
response.add_answer(RR('_http._tcp.local', QTYPE.PTR, rdata = ptr, ttl=120))
response.add_ar(RR('toto._http._tcp.local', QTYPE.SRV, rdata = srv, ttl=120))
response.add_ar(RR('toto._http._tcp.local', QTYPE.TXT, rdata = txt, ttl=120))
response.add_ar(RR('toto.local', QTYPE.A, rdata = a, ttl=120))
response.add_answer(
RR("_http._tcp.local", QTYPE.PTR, rdata=ptr, ttl=120)
)
response.add_ar(
RR(
SERVICE_TO_ANNOUNCE + "._http._tcp.local",
QTYPE.SRV,
rdata=srv,
ttl=120,
)
)
response.add_ar(
RR(
SERVICE_TO_ANNOUNCE + "._http._tcp.local",
QTYPE.TXT,
rdata=txt,
ttl=120,
)
)
response.add_ar(
RR(SERVICE_TO_ANNOUNCE + ".local", QTYPE.A, rdata=a, ttl=120)
)
print(str(response))
if unicast_response:
print("Unicast response")
@@ -48,7 +81,8 @@ def main():
else:
print("Multicast response")
sock.sendto(response.pack(), (multicast_group, multicast_port))
print(f'Send response to {sender}')
print(f"Send response to {sender}")
if __name__ == "__main__":
main()