MSVSphere Packaging Team
1 year ago
parent
2b068456f8
commit
ee32dc2838
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From ed920ea2ae1cc1214b42b82a5149758dbec941a5 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Ond=C5=99ej=20Sur=C3=BD?= <ondrej@isc.org>
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Date: Tue, 30 May 2023 08:46:17 +0200
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Subject: [PATCH] Improve RBT overmem cache cleaning
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When cache memory usage is over the configured cache size (overmem) and
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we are cleaning unused entries, it might not be enough to clean just two
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entries if the entries to be expired are smaller than the newly added
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rdata. This could be abused by an attacker to cause a remote Denial of
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Service by possibly running out of the operating system memory.
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Currently, the addrdataset() tries to do a single TTL-based cleaning
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considering the serve-stale TTL and then optionally moves to overmem
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cleaning if we are in that condition. Then the overmem_purge() tries to
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do another single TTL based cleaning from the TTL heap and then continue
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with LRU-based cleaning up to 2 entries cleaned.
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Squash the TTL-cleaning mechanism into single call from addrdataset(),
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but ignore the serve-stale TTL if we are currently overmem.
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Then instead of having a fixed number of entries to clean, pass the size
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of newly added rdatasetheader to the overmem_purge() function and
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cleanup at least the size of the newly added data. This prevents the
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cache going over the configured memory limit (`max-cache-size`).
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Additionally, refactor the overmem_purge() function to reduce for-loop
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nesting for readability.
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(cherry picked from commit f1d9e9ee3859976f403914d20ad2a10855343702)
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---
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lib/dns/rbtdb.c | 105 ++++++++++++++++++++++++++++++------------------
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1 file changed, 65 insertions(+), 40 deletions(-)
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diff --git a/lib/dns/rbtdb.c b/lib/dns/rbtdb.c
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index 51178cc877..75f97f5550 100644
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--- a/lib/dns/rbtdb.c
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+++ b/lib/dns/rbtdb.c
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@@ -599,7 +599,7 @@ static void
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expire_header(dns_rbtdb_t *rbtdb, rdatasetheader_t *header, bool tree_locked,
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expire_t reason);
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static void
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-overmem_purge(dns_rbtdb_t *rbtdb, unsigned int locknum_start, isc_stdtime_t now,
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+overmem_purge(dns_rbtdb_t *rbtdb, unsigned int locknum_start, size_t purgesize,
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bool tree_locked);
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static isc_result_t
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resign_insert(dns_rbtdb_t *rbtdb, int idx, rdatasetheader_t *newheader);
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@@ -6802,6 +6802,16 @@ cleanup:
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static dns_dbmethods_t zone_methods;
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+static size_t
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+rdataset_size(rdatasetheader_t *header) {
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+ if (!NONEXISTENT(header)) {
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+ return (dns_rdataslab_size((unsigned char *)header,
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+ sizeof(*header)));
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+ }
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+
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+ return (sizeof(*header));
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+}
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+
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static isc_result_t
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addrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
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isc_stdtime_t now, dns_rdataset_t *rdataset, unsigned int options,
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@@ -6965,7 +6975,8 @@ addrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
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}
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if (cache_is_overmem) {
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- overmem_purge(rbtdb, rbtnode->locknum, now, tree_locked);
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+ overmem_purge(rbtdb, rbtnode->locknum, rdataset_size(newheader),
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+ tree_locked);
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}
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NODE_LOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
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@@ -6984,10 +6995,18 @@ addrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
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}
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header = isc_heap_element(rbtdb->heaps[rbtnode->locknum], 1);
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- if (header != NULL && header->rdh_ttl + rbtdb->serve_stale_ttl <
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- now - RBTDB_VIRTUAL)
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- {
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- expire_header(rbtdb, header, tree_locked, expire_ttl);
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+ if (header != NULL) {
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+ dns_ttl_t rdh_ttl = header->rdh_ttl;
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+
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+ /* Only account for stale TTL if cache is not overmem */
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+ if (!cache_is_overmem) {
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+ rdh_ttl += rbtdb->serve_stale_ttl;
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+ }
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+
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+ if (rdh_ttl < now - RBTDB_VIRTUAL) {
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+ expire_header(rbtdb, header, tree_locked,
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+ expire_ttl);
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+ }
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}
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/*
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@@ -10531,52 +10550,58 @@ update_header(dns_rbtdb_t *rbtdb, rdatasetheader_t *header, isc_stdtime_t now) {
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ISC_LIST_PREPEND(rbtdb->rdatasets[header->node->locknum], header, link);
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}
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+static size_t
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+expire_lru_headers(dns_rbtdb_t *rbtdb, unsigned int locknum, size_t purgesize,
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+ bool tree_locked) {
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+ rdatasetheader_t *header, *header_prev;
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+ size_t purged = 0;
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+
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+ for (header = ISC_LIST_TAIL(rbtdb->rdatasets[locknum]);
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+ header != NULL && purged <= purgesize; header = header_prev)
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+ {
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+ header_prev = ISC_LIST_PREV(header, link);
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+ /*
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+ * Unlink the entry at this point to avoid checking it
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+ * again even if it's currently used someone else and
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+ * cannot be purged at this moment. This entry won't be
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+ * referenced any more (so unlinking is safe) since the
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+ * TTL was reset to 0.
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+ */
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+ ISC_LIST_UNLINK(rbtdb->rdatasets[locknum], header, link);
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+ size_t header_size = rdataset_size(header);
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+ expire_header(rbtdb, header, tree_locked, expire_lru);
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+ purged += header_size;
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+ }
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+
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+ return (purged);
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+}
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+
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/*%
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- * Purge some expired and/or stale (i.e. unused for some period) cache entries
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- * under an overmem condition. To recover from this condition quickly, up to
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- * 2 entries will be purged. This process is triggered while adding a new
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- * entry, and we specifically avoid purging entries in the same LRU bucket as
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- * the one to which the new entry will belong. Otherwise, we might purge
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- * entries of the same name of different RR types while adding RRsets from a
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- * single response (consider the case where we're adding A and AAAA glue records
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- * of the same NS name).
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+ * Purge some stale (i.e. unused for some period - LRU based cleaning) cache
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+ * entries under the overmem condition. To recover from this condition quickly,
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+ * we cleanup entries up to the size of newly added rdata (passed as purgesize).
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+ *
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+ * This process is triggered while adding a new entry, and we specifically avoid
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+ * purging entries in the same LRU bucket as the one to which the new entry will
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+ * belong. Otherwise, we might purge entries of the same name of different RR
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+ * types while adding RRsets from a single response (consider the case where
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+ * we're adding A and AAAA glue records of the same NS name).
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*/
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static void
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-overmem_purge(dns_rbtdb_t *rbtdb, unsigned int locknum_start, isc_stdtime_t now,
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+overmem_purge(dns_rbtdb_t *rbtdb, unsigned int locknum_start, size_t purgesize,
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bool tree_locked) {
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- rdatasetheader_t *header, *header_prev;
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unsigned int locknum;
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- int purgecount = 2;
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+ size_t purged = 0;
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for (locknum = (locknum_start + 1) % rbtdb->node_lock_count;
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- locknum != locknum_start && purgecount > 0;
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+ locknum != locknum_start && purged <= purgesize;
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locknum = (locknum + 1) % rbtdb->node_lock_count)
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{
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NODE_LOCK(&rbtdb->node_locks[locknum].lock,
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isc_rwlocktype_write);
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- header = isc_heap_element(rbtdb->heaps[locknum], 1);
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- if (header && header->rdh_ttl < now - RBTDB_VIRTUAL) {
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- expire_header(rbtdb, header, tree_locked, expire_ttl);
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- purgecount--;
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- }
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-
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- for (header = ISC_LIST_TAIL(rbtdb->rdatasets[locknum]);
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- header != NULL && purgecount > 0; header = header_prev)
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- {
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- header_prev = ISC_LIST_PREV(header, link);
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- /*
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- * Unlink the entry at this point to avoid checking it
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- * again even if it's currently used someone else and
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- * cannot be purged at this moment. This entry won't be
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- * referenced any more (so unlinking is safe) since the
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- * TTL was reset to 0.
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- */
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- ISC_LIST_UNLINK(rbtdb->rdatasets[locknum], header,
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- link);
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- expire_header(rbtdb, header, tree_locked, expire_lru);
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- purgecount--;
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- }
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+ purged += expire_lru_headers(rbtdb, locknum, purgesize - purged,
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+ tree_locked);
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NODE_UNLOCK(&rbtdb->node_locks[locknum].lock,
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isc_rwlocktype_write);
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--
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2.40.1
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@ -0,0 +1,37 @@
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From e73ecbf039c3b2cd33dd2926691a8a346c9ca574 Mon Sep 17 00:00:00 2001
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From: Matthijs Mekking <matthijs@isc.org>
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Date: Tue, 2 Aug 2022 14:21:40 +0200
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Subject: [PATCH 1/3] Don't enable serve-stale on duplicate queries
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When checking if we should enable serve-stale, add an early out case
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when the result is an error signalling a duplicate query or a query
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that would be dropped.
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(cherry picked from commit 059a4c2f4d9d3cff371842f43208d021509314fa)
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(cherry picked from commit dd7dde5743715dc0dec2defbb92b1a8637977bf9)
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---
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lib/ns/query.c | 8 ++++++++
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1 file changed, 8 insertions(+)
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diff --git a/lib/ns/query.c b/lib/ns/query.c
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index 4f61374e2c..c169e22bf4 100644
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--- a/lib/ns/query.c
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+++ b/lib/ns/query.c
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@@ -7205,6 +7205,14 @@ query_usestale(query_ctx_t *qctx, isc_result_t result) {
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return (false);
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}
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+ if (result == DNS_R_DUPLICATE || result == DNS_R_DROP) {
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+ /*
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+ * Don't enable serve-stale if the result signals a duplicate
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+ * query or query that is being dropped.
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+ */
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+ return (false);
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+ }
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+
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qctx_clean(qctx);
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qctx_freedata(qctx);
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--
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2.40.1
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@ -0,0 +1,72 @@
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From 589c06568e3036bfe713d42b53c8e88005ce17e4 Mon Sep 17 00:00:00 2001
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From: Evan Hunt <each@isc.org>
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Date: Thu, 25 May 2023 23:53:50 -0700
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Subject: [PATCH 2/3] Stale answer lookups could loop when over recursion quota
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When a query was aborted because of the recursion quota being exceeded,
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but triggered a stale answer response and a stale data refresh query,
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it could cause named to loop back where we are iterating and following
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a delegation. Having no good answer in cache, we would fall back to
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using serve-stale again, use the stale data, try to refresh the RRset,
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and loop back again, without ever terminating until crashing due to
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stack overflow.
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This happens because in the functions 'query_notfound()' and
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'query_delegation_recurse()', we check whether we can fall back to
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serving stale data. We shouldn't do so if we are already refreshing
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an RRset due to having prioritized stale data in cache.
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In other words, we need to add an extra check to 'query_usestale()' to
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disallow serving stale data if we are currently refreshing a stale
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RRset.
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As an additional mitigation to prevent looping, we now use the result
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code ISC_R_ALREADYRUNNING rather than ISC_R_FAILURE when a recursion
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loop is encountered, and we check for that condition in
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'query_usestale()' as well.
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(cherry picked from commit 0101e28f91fb36b6a16a0049d3b3e2b7846f23f0)
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---
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lib/ns/query.c | 17 ++++++++++++++---
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1 file changed, 14 insertions(+), 3 deletions(-)
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diff --git a/lib/ns/query.c b/lib/ns/query.c
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index c169e22bf4..1eb662ea4d 100644
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--- a/lib/ns/query.c
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+++ b/lib/ns/query.c
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@@ -6229,7 +6229,7 @@ ns_query_recurse(ns_client_t *client, dns_rdatatype_t qtype, dns_name_t *qname,
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if (recparam_match(&client->query.recparam, qtype, qname, qdomain)) {
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ns_client_log(client, NS_LOGCATEGORY_CLIENT, NS_LOGMODULE_QUERY,
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ISC_LOG_INFO, "recursion loop detected");
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- return (ISC_R_FAILURE);
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+ return (ISC_R_ALREADYRUNNING);
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}
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recparam_update(&client->query.recparam, qtype, qname, qdomain);
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@@ -7205,10 +7205,21 @@ query_usestale(query_ctx_t *qctx, isc_result_t result) {
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return (false);
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}
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- if (result == DNS_R_DUPLICATE || result == DNS_R_DROP) {
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+ if (qctx->refresh_rrset) {
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+ /*
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+ * This is a refreshing query, we have already prioritized
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+ * stale data, so don't enable serve-stale again.
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+ */
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+ return (false);
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+ }
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+
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+ if (result == DNS_R_DUPLICATE || result == DNS_R_DROP ||
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+ result == ISC_R_ALREADYRUNNING)
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+ {
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/*
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* Don't enable serve-stale if the result signals a duplicate
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- * query or query that is being dropped.
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+ * query or a query that is being dropped or can't proceed
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+ * because of a recursion loop.
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*/
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return (false);
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}
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--
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2.40.1
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@ -0,0 +1,60 @@
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From c20e9d30bae58d3120aa7c6a0e5dcae0e7e93dbd Mon Sep 17 00:00:00 2001
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From: Matthijs Mekking <matthijs@isc.org>
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Date: Thu, 1 Jun 2023 10:03:48 +0200
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Subject: [PATCH 3/3] Fix serve-stale hang at shutdown
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The 'refresh_rrset' variable is used to determine if we can detach from
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the client. This can cause a hang on shutdown. To fix this, move setting
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of the 'nodetach' variable up to where 'refresh_rrset' is set (in
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query_lookup(), and thus not in ns_query_done()), and set it to false
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when actually refreshing the RRset, so that when this lookup is
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completed, the client will be detached.
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(cherry picked from commit c003c5bc3c68f3e513654b6689e1f60280d14844)
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---
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lib/ns/query.c | 13 ++++++++-----
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1 file changed, 8 insertions(+), 5 deletions(-)
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diff --git a/lib/ns/query.c b/lib/ns/query.c
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index 1eb662ea4d..4fe3e30f45 100644
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|
--- a/lib/ns/query.c
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+++ b/lib/ns/query.c
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@@ -5644,6 +5644,7 @@ query_refresh_rrset(query_ctx_t *orig_qctx) {
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|
qctx.client->query.dboptions &= ~(DNS_DBFIND_STALETIMEOUT |
|
||||||
|
DNS_DBFIND_STALEOK |
|
||||||
|
DNS_DBFIND_STALEENABLED);
|
||||||
|
+ qctx.client->nodetach = false;
|
||||||
|
|
||||||
|
/*
|
||||||
|
* We'll need some resources...
|
||||||
|
@@ -5868,7 +5869,14 @@ query_lookup(query_ctx_t *qctx) {
|
||||||
|
"%s stale answer used, an attempt to "
|
||||||
|
"refresh the RRset will still be made",
|
||||||
|
namebuf);
|
||||||
|
+
|
||||||
|
qctx->refresh_rrset = STALE(qctx->rdataset);
|
||||||
|
+
|
||||||
|
+ /*
|
||||||
|
+ * If we are refreshing the RRSet, we must not
|
||||||
|
+ * detach from the client in query_send().
|
||||||
|
+ */
|
||||||
|
+ qctx->client->nodetach = qctx->refresh_rrset;
|
||||||
|
}
|
||||||
|
} else {
|
||||||
|
/*
|
||||||
|
@@ -11469,12 +11477,7 @@ ns_query_done(query_ctx_t *qctx) {
|
||||||
|
/*
|
||||||
|
* Client may have been detached after query_send(), so
|
||||||
|
* we test and store the flag state here, for safety.
|
||||||
|
- * If we are refreshing the RRSet, we must not detach from the client
|
||||||
|
- * in the query_send(), so we need to override the flag.
|
||||||
|
*/
|
||||||
|
- if (qctx->refresh_rrset) {
|
||||||
|
- qctx->client->nodetach = true;
|
||||||
|
- }
|
||||||
|
nodetach = qctx->client->nodetach;
|
||||||
|
query_send(qctx->client);
|
||||||
|
|
||||||
|
--
|
||||||
|
2.40.1
|
||||||
|
|
||||||
Loading…
Reference in new issue