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fix: dev: Don't serve a stale CNAME or record when fresh data of the other exists

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When a cached name held both a CNAME and records of another type — one stale,
the other still fresh — named with serve-stale could return the expired set
instead of the fresh one, in either direction. It now prefers whichever is fresh.

Merge branch 'ondrej/fix-serve_stale-cname-and-type' into 'main'

See merge request isc-projects/bind9!12282
This commit is contained in:
Ondřej Surý 2026-06-24 06:53:34 +02:00
commit ac6696cdb5
1 changed files with 153 additions and 0 deletions
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153
tests/dns/qpdb_test.c
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@ -120,6 +120,155 @@ cleanup_all_deadnodes(dns_db_t *db) {
qpcache_unref(qpdb);
}
/*
* Add to cache DB 'db' an rdataset of type 'rtype' at 'name', with the single
* rdata parsed from the text 'rdatastr'. The rdataset is given TTL 'ttl'
* relative to 'now', so passing a 'now' in the past makes the entry expired
* (and, with serve-stale enabled, stale).
*/
static void
servestale_addrdataset(dns_db_t *db, const dns_name_t *name, isc_stdtime_t now,
dns_rdatatype_t rtype, const char *rdatastr,
dns_ttl_t ttl, dns_trust_t trust) {
isc_result_t result;
dns_rdata_t rdata;
dns_dbnode_t *node = NULL;
dns_rdatalist_t rdatalist;
dns_rdataset_t rdataset;
unsigned char rdatabuf[1024];
dns_rdata_init(&rdata);
result = dns_test_rdatafromstring(&rdata, dns_rdataclass_in, rtype,
rdatabuf, sizeof(rdatabuf), rdatastr,
false);
assert_int_equal(result, ISC_R_SUCCESS);
dns_rdatalist_init(&rdatalist);
rdatalist.rdclass = dns_rdataclass_in;
rdatalist.type = rtype;
rdatalist.ttl = ttl;
ISC_LIST_APPEND(rdatalist.rdata, &rdata, link);
dns_rdataset_init(&rdataset);
dns_rdatalist_tordataset(&rdatalist, &rdataset);
rdataset.trust = trust;
result = dns_db_findnode(db, name, true, &node);
assert_true(result == ISC_R_SUCCESS || result == DNS_R_CNAME);
assert_non_null(node);
result = dns_db_addrdataset(db, node, NULL, now, &rdataset, 0, NULL);
assert_int_equal(result, ISC_R_SUCCESS);
dns_db_detachnode(&node);
}
/*
* Create a cache DB with serve-stale enabled and bind 'name' to a freshly
* initialized name pointing into 'fname'.
*/
static dns_db_t *
servestale_setup(isc_mem_t *mctx, dns_fixedname_t *fname, dns_name_t **namep) {
isc_result_t result;
dns_db_t *db = NULL;
result = dns_db_create(mctx, CACHEDB_DEFAULT, dns_rootname,
dns_dbtype_cache, dns_rdataclass_in, 0, NULL,
&db);
assert_int_equal(result, ISC_R_SUCCESS);
/* Keep expired entries for a day as a last-resort fallback. */
dns_db_setservestalettl(db, 86400);
dns_test_namefromstring("example.com.", fname);
*namep = dns_fixedname_name(fname);
return db;
}
/*
* Regression test for the find loop accepting a stale CNAME as a final answer
* and stopping early even though a fresh record of the requested type exists
* at the same node.
*
* A stale CNAME that expired two hours ago (but is still inside the stale
* window) is added first and a fresh non-priority type is (HINFO) added last
* last, so the stale CNAME sits at the head of the node's type list and is
* visited first by the find loop. With serve-stale enabled, the search must
* skip the stale CNAME and return the fresh HINFO rather than the stale CNAME.
*/
ISC_LOOP_TEST_IMPL(servestale_fresh_over_stale_cname) {
isc_result_t result;
dns_db_t *db = NULL;
isc_mem_t *mctx = NULL;
isc_stdtime_t now = isc_stdtime_now();
dns_fixedname_t fname, ffound;
dns_name_t *name = NULL, *foundname = NULL;
dns_rdataset_t rdataset;
isc_mem_create("test", &mctx);
db = servestale_setup(mctx, &fname, &name);
servestale_addrdataset(db, name, now - 7200, dns_rdatatype_cname,
"target.example.com.", 3600, dns_trust_answer);
servestale_addrdataset(db, name, now, dns_rdatatype_hinfo,
"CRAY-1 NEXUS", 3600, dns_trust_answer);
foundname = dns_fixedname_initname(&ffound);
dns_rdataset_init(&rdataset);
result = dns_db_find(db, name, NULL, dns_rdatatype_hinfo,
DNS_DBFIND_STALEOK, now, NULL, foundname,
&rdataset, NULL);
assert_int_equal(result, ISC_R_SUCCESS);
assert_int_equal(rdataset.type, dns_rdatatype_hinfo);
assert_false(rdataset.attributes.stale);
dns_rdataset_disassociate(&rdataset);
dns_db_detach(&db);
isc_mem_detach(&mctx);
isc_loopmgr_shutdown();
}
/*
* Same regression, but for a stale record of the requested type masking a
* fresh CNAME. A fresh CNAME is added first and a stale A is added last; the
* stale A is visited first and must not short-circuit the search. The fresh
* CNAME has to win, returning DNS_R_CNAME instead of the stale A.
*/
ISC_LOOP_TEST_IMPL(servestale_fresh_cname_over_stale_type) {
isc_result_t result;
dns_db_t *db = NULL;
isc_mem_t *mctx = NULL;
isc_stdtime_t now = isc_stdtime_now();
dns_fixedname_t fname, ffound;
dns_name_t *name = NULL, *foundname = NULL;
dns_rdataset_t rdataset;
isc_mem_create("test", &mctx);
db = servestale_setup(mctx, &fname, &name);
servestale_addrdataset(db, name, now, dns_rdatatype_cname,
"target.example.com.", 3600, dns_trust_answer);
servestale_addrdataset(db, name, now - 7200, dns_rdatatype_a,
"10.53.0.1", 3600, dns_trust_answer);
foundname = dns_fixedname_initname(&ffound);
dns_rdataset_init(&rdataset);
result = dns_db_find(db, name, NULL, dns_rdatatype_a,
DNS_DBFIND_STALEOK, now, NULL, foundname,
&rdataset, NULL);
assert_int_equal(result, DNS_R_CNAME);
assert_int_equal(rdataset.type, dns_rdatatype_cname);
assert_false(rdataset.attributes.stale);
dns_rdataset_disassociate(&rdataset);
dns_db_detach(&db);
isc_mem_detach(&mctx);
isc_loopmgr_shutdown();
}
ISC_LOOP_TEST_IMPL(overmempurge_bigrdata) {
size_t maxcache = 2097152U; /* 2MB - same as DNS_CACHE_MINSIZE */
size_t hiwater = maxcache - (maxcache >> 3); /* borrowed from cache.c */
@ -226,6 +375,10 @@ ISC_LOOP_TEST_IMPL(overmempurge_longname) {
ISC_TEST_LIST_START
ISC_TEST_ENTRY_CUSTOM(overmempurge_bigrdata, setup_managers, teardown_managers)
ISC_TEST_ENTRY_CUSTOM(overmempurge_longname, setup_managers, teardown_managers)
ISC_TEST_ENTRY_CUSTOM(servestale_fresh_over_stale_cname, setup_managers,
teardown_managers)
ISC_TEST_ENTRY_CUSTOM(servestale_fresh_cname_over_stale_type, setup_managers,
teardown_managers)
ISC_TEST_LIST_END
ISC_TEST_MAIN