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In the mixed threaded-resolver + c-ares configuration, Curl_async_getaddrinfo() called async_rr_start() - which initializes the c-ares channel and immediately dispatches the HTTPS RR query with ares_query_dnsrec() - before calling Curl_resolv_announce_start(). This let the HTTPS RR query reach the wire before the application-installed CURLOPT_RESOLVER_START_FUNCTION callback got a chance to configure the channel or veto the resolve, unlike the regular A/AAAA queries and the pure c-ares backend, which both already announce before querying. Split the c-ares channel setup (async_rr_init) from submitting the query (async_rr_start), and only submit it after Curl_resolv_announce_start() has returned success, so a non-zero return from the callback prevents the query from ever being sent. Reported-by: Joshua Rogers
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Copilot review overview
🟡 Changes recommended
The regression test assumes an unrelated connection result that can vary with local services.
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Review effort: Balanced
Findings: 1
Open (2)
What changed in this PR
Moves HTTPS RR submission after the resolver-start callback, allowing configuration or veto before network activity.
Changes:
- Splits c-ares channel initialization from query submission.
- Adds regression coverage for callback veto behavior.
- Clarifies callback invocation documentation.
| File | Description |
|---|---|
lib/vdns/asyn-thrdd.c |
Reorders HTTPS RR query startup. |
tests/libtest/lib464.c |
Adds resolver veto regression test. |
tests/libtest/Makefile.inc |
Registers the libtest. |
tests/data/test464 |
Defines test requirements and metadata. |
tests/data/Makefile.am |
Registers test 464. |
docs/libcurl/opts/CURLOPT_RESOLVER_START_FUNCTION.md |
Documents multiple callback invocations. |
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In the mixed threaded-resolver + c-ares configuration, Curl_async_getaddrinfo() called async_rr_start() - which initializes the c-ares channel and immediately dispatches the HTTPS RR query with ares_query_dnsrec() - before calling Curl_resolv_announce_start(). This let the HTTPS RR query reach the wire before the application-installed CURLOPT_RESOLVER_START_FUNCTION callback got a chance to configure the channel or veto the resolve, unlike the regular A/AAAA queries and the pure c-ares backend, which both already announce before querying.
Split the c-ares channel setup (async_rr_init) from submitting the query (async_rr_start), and only submit it after
Curl_resolv_announce_start() has returned success, so a non-zero return from the callback prevents the query from ever being sent.
Reported-by: Joshua Rogers