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dns: preserve reentrant c-ares query after qid reuse #46880

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dns: preserve reentrant c-ares query after qid reuse #46880

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e0f5550
dns: preserve reentrant c-ares query after qid reuse
fvallenilla Aug 21, 2026
1433e78
Merge remote-tracking branch 'origin/main' into fv/cares-qid-ownershi…
fvallenilla Aug 24, 2026
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18 changes: 18 additions & 0 deletions bazel/c-ares.patch
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Original file line number Diff line number Diff line change
Expand Up @@ -31,3 +31,21 @@ index eabd17fc..83bcf06f 100644
if (file_lookup(hquery) == ARES_SUCCESS) {
end_hquery(hquery, ARES_SUCCESS);

# Fix reentrant query removal after QID reuse (c-ares PR #1256)
diff --git a/src/lib/ares_process.c b/src/lib/ares_process.c
--- a/src/lib/ares_process.c
+++ b/src/lib/ares_process.c
@@ -1601,7 +1601,12 @@ static void ares_detach_query(ares_query_t *query)
{
/* Remove the query from all the lists in which it is linked */
ares_query_remove_from_conn(query);
- ares_htable_szvp_remove(query->channel->queries_by_qid, query->qid);
+ /* A callback may queue a new query that reuses this ID. Only remove the
+ * entry if it still points to this query. */
+ if (ares_htable_szvp_get_direct(query->channel->queries_by_qid, query->qid) ==
+ query) {
+ ares_htable_szvp_remove(query->channel->queries_by_qid, query->qid);
+ }
ares_llist_node_destroy(query->node_all_queries);
query->node_all_queries = NULL;
}
1 change: 1 addition & 0 deletions changelogs/current/bug_fixes/dns_resolver__preserve-reused-cares-qid.rst
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@@ -0,0 +1 @@
Fixed the c-ares resolver to preserve a reentrant query when it reuses the completing query's DNS transaction ID. Previously, the old query could remove the new query's ID mapping and permanently stall DNS refresh for the affected cluster.
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