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59c00a6f31
Make the decision in fctx_query() before the dispatch is bound so the chosen transport and the DNS_FETCHOPT_TCP flag agree. The previous location in resquery_send() ran after the UDP dispatch had already been attached, so the flag flip had no effect on the wire. Moving the decision earlier also means FCTX_ADDRINFO_NOEDNS0 servers, previously exempt, now escalate to TCP too. TCP works regardless of EDNS state, so this is the intended behaviour. Assisted-by: Claude:claude-opus-4-7
57 lines
1.8 KiB
Python
57 lines
1.8 KiB
Python
# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
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#
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# SPDX-License-Identifier: MPL-2.0
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#
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# This Source Code Form is subject to the terms of the Mozilla Public
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# License, v. 2.0. If a copy of the MPL was not distributed with this
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# file, you can obtain one at https://mozilla.org/MPL/2.0/.
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#
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# See the COPYRIGHT file distributed with this work for additional
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# information regarding copyright ownership.
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from re import compile as Re
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from re import escape
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import dns.message
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import dns.name
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import dns.rdataclass
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import dns.rdatatype
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import pytest
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import isctest
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pytestmark = pytest.mark.extra_artifacts(
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[
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"ans*/ans.run",
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]
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)
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def _count_received(path, qname, protocol):
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pattern = Re(rf"Received {escape(qname)}/IN/A .* \({protocol}\)$")
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with open(path, encoding="utf-8") as fh:
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return sum(1 for line in fh if pattern.search(line.rstrip()))
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def test_tcponly_fallback():
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"""
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A resolver must fall back to TCP after repeated UDP timeouts to the
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same authoritative server. ans4 drops every UDP query and answers
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only over TCP; the resolver must reach the answer via the TCP
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fallback path, after at least two UDP attempts have been dropped.
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"""
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msg = dns.message.make_query("foo.tcp-only.", "A")
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res = isctest.query.udp(msg, "10.53.0.2", timeout=15)
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isctest.check.noerror(res)
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rdataset = res.find_rrset(
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res.answer,
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dns.name.from_text("foo.tcp-only."),
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dns.rdataclass.IN,
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dns.rdatatype.A,
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)
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assert str(rdataset[0]) == "127.0.0.1"
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udp = _count_received("ans4/ans.run", "foo.tcp-only", "UDP")
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tcp = _count_received("ans4/ans.run", "foo.tcp-only", "TCP")
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assert udp == 2, f"expected exactly 2 UDP queries, got {udp}"
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assert tcp == 1, f"expected exactly 1 TCP query, got {tcp}"
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