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Avoid including additionals when the answer is suppressed by known-answer supression #614

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Merged
bdraco merged 1 commit into from
Jun 14, 2021
+120 −3
Merged

Avoid including additionals when the answer is suppressed by known-answer supression #614

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112 changes: 111 additions & 1 deletion tests/test_handlers.py
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,7 @@
import unittest.mock

import zeroconf as r
from zeroconf import ServiceInfo, Zeroconf
from zeroconf import ServiceInfo, Zeroconf, current_time_millis
from zeroconf import const

from . import _clear_cache
Expand Down Expand Up @@ -292,3 +292,113 @@ def test_unicast_response():
# unregister
zc.unregister_service(info)
zc.close()


def test_known_answer_supression():
zc = Zeroconf(interfaces=['127.0.0.1'])
type_ = "_knownservice._tcp.local."
name = "knownname"
registration_name = "%s.%s" % (name, type_)
desc = {'path': '/~paulsm/'}
server_name = "ash-2.local."
info = ServiceInfo(
type_, registration_name, 80, 0, 0, desc, server_name, addresses=[socket.inet_aton("10.0.1.2")]
)
zc.register_service(info)

now = current_time_millis()

# Test PTR supression
generated = r.DNSOutgoing(const._FLAGS_QR_QUERY)
question = r.DNSQuestion(type_, const._TYPE_PTR, const._CLASS_IN)
generated.add_question(question)
packets = generated.packets()
unicast_out, multicast_out = zc.query_handler.response(
r.DNSIncoming(packets[0]), "1.2.3.4", const._MDNS_PORT
)
assert unicast_out is None
assert multicast_out is not None and multicast_out.answers

generated = r.DNSOutgoing(const._FLAGS_QR_QUERY)
question = r.DNSQuestion(type_, const._TYPE_PTR, const._CLASS_IN)
generated.add_question(question)
generated.add_answer_at_time(info.dns_pointer(), now)
packets = generated.packets()
unicast_out, multicast_out = zc.query_handler.response(
r.DNSIncoming(packets[0]), "1.2.3.4", const._MDNS_PORT
)
assert unicast_out is None
# If the answer is suppressed, the additional should be suppresed as well
assert not multicast_out or not multicast_out.answers

# Test A supression
generated = r.DNSOutgoing(const._FLAGS_QR_QUERY)
question = r.DNSQuestion(server_name, const._TYPE_A, const._CLASS_IN)
generated.add_question(question)
packets = generated.packets()
unicast_out, multicast_out = zc.query_handler.response(
r.DNSIncoming(packets[0]), "1.2.3.4", const._MDNS_PORT
)
assert unicast_out is None
assert multicast_out is not None and multicast_out.answers

generated = r.DNSOutgoing(const._FLAGS_QR_QUERY)
question = r.DNSQuestion(server_name, const._TYPE_A, const._CLASS_IN)
generated.add_question(question)
for dns_address in info.dns_addresses():
generated.add_answer_at_time(dns_address, now)
packets = generated.packets()
unicast_out, multicast_out = zc.query_handler.response(
r.DNSIncoming(packets[0]), "1.2.3.4", const._MDNS_PORT
)
assert unicast_out is None
assert not multicast_out or not multicast_out.answers

# Test SRV supression
generated = r.DNSOutgoing(const._FLAGS_QR_QUERY)
question = r.DNSQuestion(registration_name, const._TYPE_SRV, const._CLASS_IN)
generated.add_question(question)
packets = generated.packets()
unicast_out, multicast_out = zc.query_handler.response(
r.DNSIncoming(packets[0]), "1.2.3.4", const._MDNS_PORT
)
assert unicast_out is None
assert multicast_out is not None and multicast_out.answers

generated = r.DNSOutgoing(const._FLAGS_QR_QUERY)
question = r.DNSQuestion(registration_name, const._TYPE_SRV, const._CLASS_IN)
generated.add_question(question)
generated.add_answer_at_time(info.dns_service(), now)
packets = generated.packets()
unicast_out, multicast_out = zc.query_handler.response(
r.DNSIncoming(packets[0]), "1.2.3.4", const._MDNS_PORT
)
assert unicast_out is None
# If the answer is suppressed, the additional should be suppresed as well
assert not multicast_out or not multicast_out.answers

# Test TXT supression
generated = r.DNSOutgoing(const._FLAGS_QR_QUERY)
question = r.DNSQuestion(registration_name, const._TYPE_TXT, const._CLASS_IN)
generated.add_question(question)
packets = generated.packets()
unicast_out, multicast_out = zc.query_handler.response(
r.DNSIncoming(packets[0]), "1.2.3.4", const._MDNS_PORT
)
assert unicast_out is None
assert multicast_out is not None and multicast_out.answers

generated = r.DNSOutgoing(const._FLAGS_QR_QUERY)
question = r.DNSQuestion(registration_name, const._TYPE_TXT, const._CLASS_IN)
generated.add_question(question)
generated.add_answer_at_time(info.dns_text(), now)
packets = generated.packets()
unicast_out, multicast_out = zc.query_handler.response(
r.DNSIncoming(packets[0]), "1.2.3.4", const._MDNS_PORT
)
assert unicast_out is None
assert not multicast_out or not multicast_out.answers

# unregister
zc.unregister_service(info)
zc.close()
11 changes: 9 additions & 2 deletions zeroconf/_handlers.py
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Original file line number Diff line number Diff line change
Expand Up @@ -75,6 +75,9 @@ def _answer_service_type_enumeration_query(self, msg: DNSIncoming, out: DNSOutgo
def _answer_ptr_query(self, msg: DNSIncoming, out: DNSOutgoing, question: DNSQuestion) -> None:
"""Answer a PTR query."""
for service in self.registry.get_infos_type(question.name):
dns_pointer = service.dns_pointer()
if dns_pointer.suppressed_by(msg):
continue
out.add_answer(msg, service.dns_pointer())
# Add recommended additional answers according to
# https://tools.ietf.org/html/rfc6763#section-12.1.
Expand Down Expand Up @@ -103,8 +106,12 @@ def _answer_non_ptr_query(self, msg: DNSIncoming, out: DNSOutgoing, question: DN
if question.type in (_TYPE_TXT, _TYPE_ANY):
out.add_answer(msg, service.dns_text())
if question.type == _TYPE_SRV:
for dns_address in service.dns_addresses():
out.add_additional_answer(dns_address)
dns_service = service.dns_service()
if not dns_service.suppressed_by(msg):
# Add recommended additional answers according to
# https://datatracker.ietf.org/doc/html/rfc6763#section-12.2
for dns_address in service.dns_addresses():
out.add_additional_answer(dns_address)

def response( # pylint: disable=unused-argument
self, msg: DNSIncoming, addr: Optional[str], port: int
Expand Down