Don't expire fresh ADB names and entries

The overmem cleaning in ADB could become overzealous and clean fresh ADB
names and entries.  Add a safety check to not clean any ADB names and
entries that are below ADB_CACHE_MINIMUM threshold.

diff --git a/lib/dns/adb.c b/lib/dns/adb.c
index 9032d346025ad675cf9c6395f9b4d1d61a53bb9b..0454105c14d592030a6b2975c5365b61a0f4c0a1 100644 (file)
--- a/lib/dns/adb.c
+++ b/lib/dns/adb.c
@@ -1375,7 +1375,7 @@ get_attached_and_locked_name(dns_adb_t *adb, const dns_name_t *name,
                break;
        case ISC_R_SUCCESS:
                LOCK(&adbname->lock); /* Must be unlocked by the caller */
-               if (adbname->last_used + ADB_STALE_MARGIN <= last_update) {
+               if (adbname->last_used + ADB_CACHE_MINIMUM <= last_update) {
                        adbname->last_used = now;
 
                        ISC_LIST_UNLINK(adb->names_lru, adbname, link);
@@ -1449,7 +1449,7 @@ get_attached_and_locked_entry(dns_adb_t *adb, isc_stdtime_t now,
                        dns_adbentry_detach(&adbentry);
                        goto create;
                }
-               if (adbentry->last_used + ADB_STALE_MARGIN <= last_update) {
+               if (adbentry->last_used + ADB_CACHE_MINIMUM <= last_update) {
                        adbentry->last_used = now;
 
                        ISC_LIST_UNLINK(adb->entries_lru, adbentry, link);
@@ -1708,6 +1708,15 @@ purge_stale_names(dns_adb_t *adb, isc_stdtime_t now) {
                        goto next;
                }
 
+               /*
+                * Make sure that we are not purging ADB names that has been
+                * just created.
+                */
+               if (adbname->last_used + ADB_CACHE_MINIMUM >= now) {
+                       prev = NULL;
+                       goto next;
+               }
+
                if (overmem) {
                        expire_name(adbname, DNS_EVENT_ADBCANCELED, now);
                        removed++;
@@ -1717,13 +1726,14 @@ purge_stale_names(dns_adb_t *adb, isc_stdtime_t now) {
                if (adbname->last_used + ADB_STALE_MARGIN < now) {
                        expire_name(adbname, DNS_EVENT_ADBCANCELED, now);
                        removed++;
+                       goto next;
                }
 
                /*
-                * we won't expire anything on the LRU list as the
+                * We won't expire anything on the LRU list as the
                 * .last_used + ADB_STALE_MARGIN will always be bigger
                 * than `now` for all previous entries, so we just stop
-                * the scanning
+                * the scanning.
                 */
                prev = NULL;
        next:
@@ -1801,6 +1811,15 @@ purge_stale_entries(dns_adb_t *adb, isc_stdtime_t now) {
                        goto next;
                }
 
+               /*
+                * Make sure that we are not purging ADB named that has been
+                * just created.
+                */
+               if (adbentry->last_used + ADB_CACHE_MINIMUM >= now) {
+                       prev = NULL;
+                       goto next;
+               }
+
                if (overmem) {
                        maybe_expire_entry(adbentry, INT_MAX);
                        removed++;
@@ -1814,7 +1833,7 @@ purge_stale_entries(dns_adb_t *adb, isc_stdtime_t now) {
                }
 
                /*
-                * we won't expire anything on the LRU list as the
+                * We won't expire anything on the LRU list as the
                 * .last_used + ADB_STALE_MARGIN will always be bigger
                 * than `now` for all previous entries, so we just stop
                 * the scanning