Attempt to compare rwlock and LMDB internal locking mechanism.

The benchmark first writes 1000 key/values (actually, the same key is
re-used) in LMDB and read it 1000 times. Then it does the same thing
using concurrency, on a 16 cores machine, with the following
configurations:

- 32 threads (29 readers and 3 writer)
- 8 threads (6 readers and 2 writer)
- 8 threads (8 readers and 0 writer)

See [3] for LMDB internal locking result and [4] for rwlock result.

What the result seems to say is that LMDB internal locking mechanism
is doing way better (100x) when there are lot of concurrency
involved. I'm kinda surprised by such factor and tried various things
in case I've done something wrong, but eventually always end up with
similar difference. The only explanation I have is that LMDB actually
does uses an userspace RCU mechanism internally, so readers are never
blocked.

Using rwlock would block the readers while a writer lock is
alive. LMDB doc seems to say [1] that if we use our own
synchronization mechanism, we should only have one writer at the time,
and hold a write lock from the beginning of the transaction up to the
commit/revert (I tried holding a read lock on a write transaction then
upgrade to a write lock only at commit time... but of course I end up
in lot of odd crashes). I think this explain the massive congestion
when using 32 threads, as lot of readers are waiting.

When there is no thread congestion (the 2 later configuration with 8
threads) using the rwlock actually seems a little bit faster (same
order of magnitude though). I guess this might be explained by the
fact that, while LMDB doesn't lock readers, there is still a quick
lock-unlock to maintains a reader table (and eventually free unused
old versions once a writer commit). [2]

[1] http://www.lmdb.tech/doc/group__mdb.html#:~:text=must%20ensure%20that%20no%20readers%20are%20using%20old%20transactions%20while%20a%20writer%20is%20active

[2] http://www.lmdb.tech/doc/group__readers.html

[3] two runs using LMDB internal locking (HEAD~2)

    sequential writes and read
    avg write 0.005878 ms
    avg read 0.001640 ms
    concurrent 29 readers and 3 writers
    avg write 0.746217 ms
    avg read 6.644507 ms
    concurrent 6 readers and 2 writers
    avg write 0.077576 ms
    avg read 0.177316 ms
    concurrent 8 readers and 0 writer
    avg write 0.000000 ms
    avg read 0.273563 ms

    sequential writes and read
    avg write 0.005799 ms
    avg read 0.001656 ms
    concurrent 29 readers and 3 writers
    avg write 0.737782 ms
    avg read 6.616162 ms
    concurrent 6 readers and 2 writers
    avg write 0.075893 ms
    avg read 0.178631 ms
    concurrent 8 readers and 0 writer
    avg write 0.000000 ms
    avg read 0.303209 ms

[4] two runs using rwlock (HEAD~1)

    sequential writes and read
    avg write 0.005931 ms
    avg read 0.001658 ms
    concurrent 29 readers and 3 writers
    avg write 17.249417 ms
    avg read 163.805094 ms
    concurrent 6 readers and 2 writers
    avg write 0.040559 ms
    avg read 0.168439 ms
    concurrent 8 readers and 0 writer
    avg write 0.000000 ms
    avg read 0.200699 ms

    sequential writes and read
    avg write 0.007423 ms
    avg read 0.001656 ms
    concurrent 29 readers and 3 writers
    avg write 20.312584 ms
    avg read 190.565366 ms
    concurrent 6 readers and 2 writers
    avg write 0.026039 ms
    avg read 0.147365 ms
    concurrent 8 readers and 0 writer
    avg write 0.000000 ms
    avg read 0.174471 ms

.gitlab-ci.yml

@@ -1029,13 +1029,12 @@ unit:gcc:ossl3:amd64:
       artifacts: true
 
 # Jobs for regular GCC builds on Debian "sid" (amd64)
-# Also tests configration option: --without-lmdb.
 
 gcc:sid:amd64:
   variables:
     CC: gcc
     CFLAGS: "${CFLAGS_COMMON} -O3"
-    EXTRA_CONFIGURE: "--with-libidn2 --without-lmdb ${WITH_READLINE}"
+    EXTRA_CONFIGURE: "--with-libidn2 ${WITH_READLINE}"
     RUN_MAKE_INSTALL: 1
   <<: *debian_sid_amd64_image
   <<: *build_job
@@ -1056,14 +1055,13 @@ unit:gcc:sid:amd64:
       artifacts: true
 
 # Job for out-of-tree GCC build on Debian 12 "bookworm" (amd64)
-# Also tests configration option: --with-lmdb.
 
 gcc:out-of-tree:
   variables:
     CC: gcc
     CFLAGS: "${CFLAGS_COMMON} -Og"
     CONFIGURE: "${CI_PROJECT_DIR}/configure"
-    EXTRA_CONFIGURE: "--with-libidn2 --with-lmdb"
+    EXTRA_CONFIGURE: "--with-libidn2"
     RUN_MAKE_INSTALL: 1
     OUT_OF_TREE_WORKSPACE: workspace
   <<: *base_image

bin/named/config.c

@@ -159,11 +159,9 @@ options {\n\
 	fetch-quota-params 100 0.1 0.3 0.7;\n\
 	fetches-per-server 0;\n\
 	fetches-per-zone 0;\n\
-	lame-ttl 0;\n"
-#ifdef HAVE_LMDB
-			    "	lmdb-mapsize 32M;\n"
-#endif /* ifdef HAVE_LMDB */
-			    "	max-cache-size 90%;\n\
+	lame-ttl 0;\n\
+        lmdb-mapsize 32M;\n\
+        max-cache-size 90%;\n\
 	max-cache-ttl 604800; /* 1 week */\n\
 	max-clients-per-query 100;\n\
 	max-ncache-ttl 10800; /* 3 hours */\n\

bin/named/server.c

@@ -45,6 +45,7 @@
 #include <isc/httpd.h>
 #include <isc/job.h>
 #include <isc/lex.h>
+#include <isc/lmdb.h>
 #include <isc/loop.h>
 #include <isc/meminfo.h>
 #include <isc/netmgr.h>
@@ -140,15 +141,6 @@
 #include <named/smf_globals.h>
 #endif /* ifdef HAVE_LIBSCF */
 
-#ifdef HAVE_LMDB
-#include <lmdb.h>
-#define configure_newzones configure_newzones_db
-#define dumpzone	   dumpzone_db
-#else /* HAVE_LMDB */
-#define configure_newzones configure_newzones_file
-#define dumpzone	   dumpzone_file
-#endif /* HAVE_LMDB */
-
 #ifndef SIZE_MAX
 #define SIZE_MAX ((size_t)-1)
 #endif /* ifndef SIZE_MAX */
@@ -503,7 +495,6 @@ putuint8(isc_buffer_t **b, uint8_t val);
 static isc_result_t
 putnull(isc_buffer_t **b);
 
-#ifdef HAVE_LMDB
 static isc_result_t
 nzd_writable(dns_view_t *view);
 
@@ -518,10 +509,6 @@ nzd_env_close(dns_view_t *view);
 
 static isc_result_t
 nzd_close(MDB_txn **txnp, bool commit);
-#else  /* ifdef HAVE_LMDB */
-static isc_result_t
-nzf_append(dns_view_t *view, const cfg_obj_t *zconfig);
-#endif /* ifdef HAVE_LMDB */
 
 static isc_result_t
 load_nzf(dns_view_t *view, ns_cfgctx_t *nzcfg);
@@ -7361,7 +7348,6 @@ setup_newzones(dns_view_t *view, cfg_obj_t *config, cfg_obj_t *vconfig,
 		dns_view_setnewzonedir(view, dir);
 	}
 
-#ifdef HAVE_LMDB
 	result = named_config_get(maps, "lmdb-mapsize", &obj);
 	if (result == ISC_R_SUCCESS && obj != NULL) {
 		mapsize = cfg_obj_asuint64(obj);
@@ -7381,9 +7367,6 @@ setup_newzones(dns_view_t *view, cfg_obj_t *config, cfg_obj_t *vconfig,
 			return ISC_R_FAILURE;
 		}
 	}
-#else  /* ifdef HAVE_LMDB */
-	UNUSED(obj);
-#endif /* HAVE_LMDB */
 
 	/*
 	 * A non-empty catalog-zones statement implies allow-new-zones
@@ -7478,54 +7461,6 @@ configure_zone_setviewcommit(isc_result_t result, const cfg_obj_t *zconfig,
 	dns_view_detach(&pview);
 }
 
-#ifndef HAVE_LMDB
-
-static isc_result_t
-configure_newzones(dns_view_t *view, cfg_obj_t *config, cfg_obj_t *vconfig,
-		   cfg_aclconfctx_t *actx) {
-	isc_result_t result;
-	ns_cfgctx_t *nzctx;
-	const cfg_obj_t *zonelist;
-	const cfg_listelt_t *element;
-
-	nzctx = view->new_zone_config;
-	if (nzctx == NULL || nzctx->nzf_config == NULL) {
-		return ISC_R_SUCCESS;
-	}
-
-	isc_log_write(NAMED_LOGCATEGORY_GENERAL, NAMED_LOGMODULE_SERVER,
-		      ISC_LOG_INFO, "loading additional zones for view '%s'",
-		      view->name);
-
-	zonelist = NULL;
-	cfg_map_get(nzctx->nzf_config, "zone", &zonelist);
-
-	for (element = cfg_list_first(zonelist); element != NULL;
-	     element = cfg_list_next(element))
-	{
-		const cfg_obj_t *zconfig = cfg_listelt_value(element);
-		CHECK(configure_zone(config, zconfig, vconfig, view,
-				     &named_g_server->viewlist,
-				     &named_g_server->kasplist,
-				     &named_g_server->keystorelist, actx, true,
-				     false, false, false));
-	}
-
-	result = ISC_R_SUCCESS;
-
-cleanup:
-	for (element = cfg_list_first(zonelist); element != NULL;
-	     element = cfg_list_next(element))
-	{
-		const cfg_obj_t *zconfig = cfg_listelt_value(element);
-		configure_zone_setviewcommit(result, zconfig, view);
-	}
-
-	return result;
-}
-
-#else /* HAVE_LMDB */
-
 static isc_result_t
 data_to_cfg(dns_view_t *view, MDB_val *key, MDB_val *data, isc_buffer_t **text,
 	    cfg_obj_t **zoneconfig) {
@@ -7823,8 +7758,6 @@ cleanup:
 	return result;
 }
 
-#endif /* HAVE_LMDB */
-
 static isc_result_t
 load_configuration(const char *filename, named_server_t *server,
 		   bool first_time) {
@@ -8832,12 +8765,11 @@ load_configuration(const char *filename, named_server_t *server,
 		server->sctx->tkeyctx = tkeyctx;
 	}
 
-#ifdef HAVE_LMDB
 	/*
-	 * If we're using LMDB, we may have created newzones databases
-	 * as root, making it impossible to reopen them later after
-	 * switching to a new userid. We close them now, and reopen
-	 * after relinquishing privileges them.
+	 * We may have created newzones LMDB databases as root, making
+	 * it impossible to reopen them later after switching to a new
+	 * userid. We close them now, and reopen after relinquishing
+	 * privileges them.
 	 */
 	if (first_time) {
 		for (dns_view_t *view = ISC_LIST_HEAD(server->viewlist);
@@ -8846,7 +8778,6 @@ load_configuration(const char *filename, named_server_t *server,
 			nzd_env_close(view);
 		}
 	}
-#endif /* HAVE_LMDB */
 
 	/*
 	 * Switch to the effective UID for setting up files.
@@ -8868,7 +8799,6 @@ load_configuration(const char *filename, named_server_t *server,
 		goto cleanup_cachelist;
 	}
 
-#ifdef HAVE_LMDB
 	/*
 	 * Reopen NZD databases.
 	 */
@@ -8879,7 +8809,6 @@ load_configuration(const char *filename, named_server_t *server,
 			nzd_env_reopen(view);
 		}
 	}
-#endif /* HAVE_LMDB */
 
 	/*
 	 * Configure the logging system.
@@ -12345,163 +12274,6 @@ named_smf_add_message(isc_buffer_t **text) {
 }
 #endif /* HAVE_LIBSCF */
 
-#ifndef HAVE_LMDB
-
-/*
- * Emit a comment at the top of the nzf file containing the viewname
- * Expects the fp to already be open for writing
- */
-#define HEADER1 "# New zone file for view: "
-#define HEADER2                                                     \
-	"\n# This file contains configuration for zones added by\n" \
-	"# the 'rndc addzone' command. DO NOT EDIT BY HAND.\n"
-static isc_result_t
-add_comment(FILE *fp, const char *viewname) {
-	isc_result_t result;
-	CHECK(isc_stdio_write(HEADER1, sizeof(HEADER1) - 1, 1, fp, NULL));
-	CHECK(isc_stdio_write(viewname, strlen(viewname), 1, fp, NULL));
-	CHECK(isc_stdio_write(HEADER2, sizeof(HEADER2) - 1, 1, fp, NULL));
-cleanup:
-	return result;
-}
-
-static void
-dumpzone(void *arg, const char *buf, int len) {
-	FILE *fp = arg;
-
-	(void)isc_stdio_write(buf, len, 1, fp, NULL);
-}
-
-static isc_result_t
-nzf_append(dns_view_t *view, const cfg_obj_t *zconfig) {
-	isc_result_t result;
-	off_t offset;
-	FILE *fp = NULL;
-	bool offsetok = false;
-
-	LOCK(&view->new_zone_lock);
-
-	CHECK(isc_stdio_open(view->new_zone_file, "a", &fp));
-	CHECK(isc_stdio_seek(fp, 0, SEEK_END));
-
-	CHECK(isc_stdio_tell(fp, &offset));
-	offsetok = true;
-	if (offset == 0) {
-		CHECK(add_comment(fp, view->name));
-	}
-
-	CHECK(isc_stdio_write("zone ", 5, 1, fp, NULL));
-	cfg_printx(zconfig, CFG_PRINTER_ONELINE, dumpzone, fp);
-	CHECK(isc_stdio_write(";\n", 2, 1, fp, NULL));
-	CHECK(isc_stdio_flush(fp));
-	result = isc_stdio_close(fp);
-	fp = NULL;
-
-cleanup:
-	if (fp != NULL) {
-		(void)isc_stdio_close(fp);
-		if (offsetok) {
-			isc_result_t result2;
-
-			result2 = isc_file_truncate(view->new_zone_file,
-						    offset);
-			if (result2 != ISC_R_SUCCESS) {
-				isc_log_write(NAMED_LOGCATEGORY_GENERAL,
-					      NAMED_LOGMODULE_SERVER,
-					      ISC_LOG_ERROR,
-					      "Error truncating NZF file '%s' "
-					      "during rollback from append: "
-					      "%s",
-					      view->new_zone_file,
-					      isc_result_totext(result2));
-			}
-		}
-	}
-	UNLOCK(&view->new_zone_lock);
-	return result;
-}
-
-static isc_result_t
-nzf_writeconf(const cfg_obj_t *config, dns_view_t *view) {
-	const cfg_obj_t *zl = NULL;
-	cfg_list_t *list;
-	const cfg_listelt_t *elt;
-
-	FILE *fp = NULL;
-	char tmp[1024];
-	isc_result_t result;
-
-	result = isc_file_template(view->new_zone_file, "nzf-XXXXXXXX", tmp,
-				   sizeof(tmp));
-	if (result == ISC_R_SUCCESS) {
-		result = isc_file_openunique(tmp, &fp);
-	}
-	if (result != ISC_R_SUCCESS) {
-		return result;
-	}
-
-	cfg_map_get(config, "zone", &zl);
-	if (!cfg_obj_islist(zl)) {
-		CHECK(ISC_R_FAILURE);
-	}
-
-	list = UNCONST(&zl->value.list);
-
-	CHECK(add_comment(fp, view->name)); /* force a comment */
-
-	for (elt = ISC_LIST_HEAD(*list); elt != NULL;
-	     elt = ISC_LIST_NEXT(elt, link))
-	{
-		const cfg_obj_t *zconfig = cfg_listelt_value(elt);
-
-		CHECK(isc_stdio_write("zone ", 5, 1, fp, NULL));
-		cfg_printx(zconfig, CFG_PRINTER_ONELINE, dumpzone, fp);
-		CHECK(isc_stdio_write(";\n", 2, 1, fp, NULL));
-	}
-
-	CHECK(isc_stdio_flush(fp));
-	result = isc_stdio_close(fp);
-	fp = NULL;
-	if (result != ISC_R_SUCCESS) {
-		goto cleanup;
-	}
-	CHECK(isc_file_rename(tmp, view->new_zone_file));
-	return result;
-
-cleanup:
-	if (fp != NULL) {
-		(void)isc_stdio_close(fp);
-	}
-	(void)isc_file_remove(tmp);
-	return result;
-}
-
-static isc_result_t
-load_nzf(dns_view_t *view, ns_cfgctx_t *nzcfg) {
-	isc_result_t result;
-
-	/* The new zone file may not exist. That is OK. */
-	if (!isc_file_exists(view->new_zone_file)) {
-		return ISC_R_SUCCESS;
-	}
-
-	/*
-	 * Parse the configuration in the NZF file.  This may be called in
-	 * multiple views, so we reset the parser each time.
-	 */
-	cfg_parser_reset(named_g_addparser);
-	result = cfg_parse_file(named_g_addparser, view->new_zone_file,
-				&cfg_type_addzoneconf, &nzcfg->nzf_config);
-	if (result != ISC_R_SUCCESS) {
-		isc_log_write(NAMED_LOGCATEGORY_GENERAL, NAMED_LOGMODULE_SERVER,
-			      ISC_LOG_ERROR, "Error parsing NZF file '%s': %s",
-			      view->new_zone_file, isc_result_totext(result));
-	}
-
-	return result;
-}
-#else  /* HAVE_LMDB */
-
 static void
 nzd_setkey(MDB_val *key, dns_name_t *name, char *namebuf, size_t buflen) {
 	dns_fixedname_t fixed;
@@ -12983,7 +12755,6 @@ cleanup:
 
 	return result;
 }
-#endif /* HAVE_LMDB */
 
 static isc_result_t
 newzone_parse(named_server_t *server, char *command, dns_view_t **viewp,
@@ -13168,21 +12939,14 @@ cleanup:
 
 static isc_result_t
 do_addzone(named_server_t *server, ns_cfgctx_t *cfg, dns_view_t *view,
-	   dns_name_t *name, cfg_obj_t *zoneconf, const cfg_obj_t *zoneobj,
-	   bool redirect, isc_buffer_t **text) {
+	   dns_name_t *name, const cfg_obj_t *zoneobj, bool redirect,
+	   isc_buffer_t **text) {
 	isc_result_t result, tresult;
 	dns_zone_t *zone = NULL;
-#ifndef HAVE_LMDB
-	FILE *fp = NULL;
-	bool cleanup_config = false;
-#else /* HAVE_LMDB */
 	MDB_txn *txn = NULL;
 	MDB_dbi dbi;
 	bool locked = false;
 
-	UNUSED(zoneconf);
-#endif
-
 	/* Zone shouldn't already exist */
 	if (redirect) {
 		result = (view->redirect == NULL) ? ISC_R_NOTFOUND
@@ -13198,24 +12962,6 @@ do_addzone(named_server_t *server, ns_cfgctx_t *cfg, dns_view_t *view,
 	}
 
 	isc_loopmgr_pause(named_g_loopmgr);
-
-#ifndef HAVE_LMDB
-	/*
-	 * Make sure we can open the configuration save file
-	 */
-	result = isc_stdio_open(view->new_zone_file, "a", &fp);
-	if (result != ISC_R_SUCCESS) {
-		isc_loopmgr_resume(named_g_loopmgr);
-		TCHECK(putstr(text, "unable to create '"));
-		TCHECK(putstr(text, view->new_zone_file));
-		TCHECK(putstr(text, "': "));
-		TCHECK(putstr(text, isc_result_totext(result)));
-		goto cleanup;
-	}
-
-	(void)isc_stdio_close(fp);
-	fp = NULL;
-#else  /* HAVE_LMDB */
 	LOCK(&view->new_zone_lock);
 	locked = true;
 	/* Make sure we can open the NZD database */
@@ -13228,7 +12974,6 @@ do_addzone(named_server_t *server, ns_cfgctx_t *cfg, dns_view_t *view,
 		result = ISC_R_FAILURE;
 		goto cleanup;
 	}
-#endif /* HAVE_LMDB */
 
 	/* Mark view unfrozen and configure zone */
 	dns_view_thaw(view);
@@ -13263,22 +13008,6 @@ do_addzone(named_server_t *server, ns_cfgctx_t *cfg, dns_view_t *view,
 		}
 	}
 
-#ifndef HAVE_LMDB
-	/*
-	 * If there wasn't a previous newzone config, just save the one
-	 * we've created. If there was a previous one, merge the new
-	 * zone into it.
-	 */
-	if (cfg->nzf_config == NULL) {
-		cfg_obj_attach(zoneconf, &cfg->nzf_config);
-	} else {
-		cfg_obj_t *z = UNCONST(zoneobj);
-		CHECK(cfg_parser_mapadd(cfg->add_parser, cfg->nzf_config, z,
-					"zone"));
-	}
-	cleanup_config = true;
-#endif /* HAVE_LMDB */
-
 	/*
 	 * Load the zone from the master file.  If this fails, we'll
 	 * need to undo the configuration we've done already.
@@ -13307,34 +13036,17 @@ do_addzone(named_server_t *server, ns_cfgctx_t *cfg, dns_view_t *view,
 	/* Flag the zone as having been added at runtime */
 	dns_zone_setadded(zone, true);
 
-#ifdef HAVE_LMDB
 	/* Save the new zone configuration into the NZD */
 	CHECK(nzd_open(view, 0, &txn, &dbi));
 	CHECK(nzd_save(&txn, dbi, zone, zoneobj));
-#else  /* ifdef HAVE_LMDB */
-	/* Append the zone configuration to the NZF */
-	result = nzf_append(view, zoneobj);
-#endif /* HAVE_LMDB */
 
 cleanup:
-
-#ifndef HAVE_LMDB
-	if (fp != NULL) {
-		(void)isc_stdio_close(fp);
-	}
-	if (result != ISC_R_SUCCESS && cleanup_config) {
-		tresult = delete_zoneconf(view, cfg->add_parser,
-					  cfg->nzf_config, name, NULL);
-		RUNTIME_CHECK(tresult == ISC_R_SUCCESS);
-	}
-#else  /* HAVE_LMDB */
 	if (txn != NULL) {
 		(void)nzd_close(&txn, false);
 	}
 	if (locked) {
 		UNLOCK(&view->new_zone_lock);
 	}
-#endif /* HAVE_LMDB */
 
 	if (zone != NULL) {
 		dns_zone_detach(&zone);
@@ -13350,14 +13062,9 @@ do_modzone(named_server_t *server, ns_cfgctx_t *cfg, dns_view_t *view,
 	isc_result_t result, tresult;
 	dns_zone_t *zone = NULL;
 	bool added;
-#ifndef HAVE_LMDB
-	FILE *fp = NULL;
-	cfg_obj_t *z;
-#else  /* HAVE_LMDB */
 	MDB_txn *txn = NULL;
 	MDB_dbi dbi;
 	bool locked = false;
-#endif /* HAVE_LMDB */
 
 	/* Zone must already exist */
 	if (redirect) {
@@ -13377,30 +13084,8 @@ do_modzone(named_server_t *server, ns_cfgctx_t *cfg, dns_view_t *view,
 	added = dns_zone_getadded(zone);
 	dns_zone_detach(&zone);
 
-#ifndef HAVE_LMDB
-	cfg = (ns_cfgctx_t *)view->new_zone_config;
-	if (cfg == NULL) {
-		TCHECK(putstr(text, "new zone config is not set"));
-		CHECK(ISC_R_FAILURE);
-	}
-#endif /* ifndef HAVE_LMDB */
-
 	isc_loopmgr_pause(named_g_loopmgr);
 
-#ifndef HAVE_LMDB
-	/* Make sure we can open the configuration save file */
-	result = isc_stdio_open(view->new_zone_file, "a", &fp);
-	if (result != ISC_R_SUCCESS) {
-		TCHECK(putstr(text, "unable to open '"));
-		TCHECK(putstr(text, view->new_zone_file));
-		TCHECK(putstr(text, "': "));
-		TCHECK(putstr(text, isc_result_totext(result)));
-		isc_loopmgr_resume(named_g_loopmgr);
-		goto cleanup;
-	}
-	(void)isc_stdio_close(fp);
-	fp = NULL;
-#else  /* HAVE_LMDB */
 	LOCK(&view->new_zone_lock);
 	locked = true;
 	/* Make sure we can open the NZD database */
@@ -13413,7 +13098,6 @@ do_modzone(named_server_t *server, ns_cfgctx_t *cfg, dns_view_t *view,
 		isc_loopmgr_resume(named_g_loopmgr);
 		goto cleanup;
 	}
-#endif /* HAVE_LMDB */
 
 	/* Reconfigure the zone */
 	dns_view_thaw(view);
@@ -13441,21 +13125,6 @@ do_modzone(named_server_t *server, ns_cfgctx_t *cfg, dns_view_t *view,
 		CHECK(dns_view_findzone(view, name, DNS_ZTFIND_EXACT, &zone));
 	}
 
-#ifndef HAVE_LMDB
-	/* Remove old zone from configuration (and NZF file if applicable) */
-	if (added) {
-		result = delete_zoneconf(view, cfg->add_parser, cfg->nzf_config,
-					 dns_zone_getorigin(zone),
-					 nzf_writeconf);
-		if (result != ISC_R_SUCCESS) {
-			TCHECK(putstr(text, "former zone configuration "
-					    "not deleted: "));
-			TCHECK(putstr(text, isc_result_totext(result)));
-			goto cleanup;
-		}
-	}
-#endif /* HAVE_LMDB */
-
 	if (!added) {
 		if (cfg->vconfig == NULL) {
 			result = delete_zoneconf(
@@ -13512,24 +13181,9 @@ do_modzone(named_server_t *server, ns_cfgctx_t *cfg, dns_view_t *view,
 		goto cleanup;
 	}
 
-#ifndef HAVE_LMDB
-	/* Store the new zone configuration; also in NZF if applicable */
-	z = UNCONST(zoneobj);
-	CHECK(cfg_parser_mapadd(cfg->add_parser, cfg->nzf_config, z, "zone"));
-#endif /* HAVE_LMDB */
-
 	if (added) {
-#ifdef HAVE_LMDB
 		CHECK(nzd_open(view, 0, &txn, &dbi));
 		CHECK(nzd_save(&txn, dbi, zone, zoneobj));
-#else  /* ifdef HAVE_LMDB */
-		result = nzf_append(view, zoneobj);
-		if (result != ISC_R_SUCCESS) {
-			TCHECK(putstr(text, "\nNew zone config not saved: "));
-			TCHECK(putstr(text, isc_result_totext(result)));
-			goto cleanup;
-		}
-#endif /* HAVE_LMDB */
 
 		TCHECK(putstr(text, "zone '"));
 		TCHECK(putstr(text, zname));
@@ -13543,18 +13197,12 @@ do_modzone(named_server_t *server, ns_cfgctx_t *cfg, dns_view_t *view,
 
 cleanup:
 
-#ifndef HAVE_LMDB
-	if (fp != NULL) {
-		(void)isc_stdio_close(fp);
-	}
-#else  /* HAVE_LMDB */
 	if (txn != NULL) {
 		(void)nzd_close(&txn, false);
 	}
 	if (locked) {
 		UNLOCK(&view->new_zone_lock);
 	}
-#endif /* HAVE_LMDB */
 
 	if (zone != NULL) {
 		dns_zone_detach(&zone);
@@ -13594,12 +13242,7 @@ named_server_changezone(named_server_t *server, char *command,
 			    &redirect, text));
 
 	/* Are we accepting new zones in this view? */
-#ifdef HAVE_LMDB
-	if (view->new_zone_db == NULL)
-#else  /* ifdef HAVE_LMDB */
-	if (view->new_zone_file == NULL)
-#endif /* HAVE_LMDB */
-	{
+	if (view->new_zone_db == NULL) {
 		(void)putstr(text, "Not allowing new zones in view '");
 		(void)putstr(text, view->name);
 		(void)putstr(text, "'");
@@ -13629,8 +13272,8 @@ named_server_changezone(named_server_t *server, char *command,
 	}
 
 	if (addzone) {
-		CHECK(do_addzone(server, cfg, view, dnsname, zoneconf, zoneobj,
-				 redirect, text));
+		CHECK(do_addzone(server, cfg, view, dnsname, zoneobj, redirect,
+				 text));
 	} else {
 		CHECK(do_modzone(server, cfg, view, dnsname, zonename, zoneobj,
 				 redirect, text));
@@ -13693,10 +13336,8 @@ rmzone(void *arg) {
 	dns_db_t *dbp = NULL;
 	bool added;
 	isc_result_t result;
-#ifdef HAVE_LMDB
 	MDB_txn *txn = NULL;
 	MDB_dbi dbi;
-#endif /* ifdef HAVE_LMDB */
 
 	REQUIRE(dz != NULL);
 
@@ -13718,7 +13359,6 @@ rmzone(void *arg) {
 	catz = dns_zone_get_parentcatz(zone);
 
 	if (added && catz == NULL && cfg != NULL) {
-#ifdef HAVE_LMDB
 		/* Make sure we can open the NZD database */
 		LOCK(&view->new_zone_lock);
 		result = nzd_open(view, 0, &txn, &dbi);
@@ -13742,17 +13382,6 @@ rmzone(void *arg) {
 			(void)nzd_close(&txn, false);
 		}
 		UNLOCK(&view->new_zone_lock);
-#else  /* ifdef HAVE_LMDB */
-		result = delete_zoneconf(view, cfg->add_parser, cfg->nzf_config,
-					 dns_zone_getorigin(zone),
-					 nzf_writeconf);
-		if (result != ISC_R_SUCCESS) {
-			isc_log_write(NAMED_LOGCATEGORY_GENERAL,
-				      NAMED_LOGMODULE_SERVER, ISC_LOG_ERROR,
-				      "unable to delete zone configuration: %s",
-				      isc_result_totext(result));
-		}
-#endif /* HAVE_LMDB */
 	}
 
 	if (!added && cfg != NULL) {
@@ -14061,9 +13690,7 @@ named_server_showzone(named_server_t *server, isc_lex_t *lex,
 	dns_view_t *view = NULL;
 	dns_zone_t *zone = NULL;
 	ns_cfgctx_t *cfg = NULL;
-#ifdef HAVE_LMDB
 	cfg_obj_t *nzconfig = NULL;
-#endif /* HAVE_LMDB */
 	bool added, redirect;
 	ns_dzarg_t dzarg;
 
@@ -14103,12 +13730,6 @@ named_server_showzone(named_server_t *server, isc_lex_t *lex,
 						     redirect);
 	}
 
-#ifndef HAVE_LMDB
-	if (zconfig == NULL && cfg->nzf_config != NULL) {
-		zconfig = find_name_in_list_from_map(cfg->nzf_config, "zone",
-						     zonename, redirect);
-	}
-#else  /* HAVE_LMDB */
 	if (zconfig == NULL) {
 		const cfg_obj_t *zlist = NULL;
 		CHECK(get_newzone_config(view, zonename, &nzconfig));
@@ -14119,7 +13740,6 @@ named_server_showzone(named_server_t *server, isc_lex_t *lex,
 
 		zconfig = cfg_listelt_value(cfg_list_first(zlist));
 	}
-#endif /* HAVE_LMDB */
 
 	if (zconfig == NULL) {
 		CHECK(ISC_R_NOTFOUND);
@@ -14137,11 +13757,10 @@ named_server_showzone(named_server_t *server, isc_lex_t *lex,
 	result = ISC_R_SUCCESS;
 
 cleanup:
-#ifdef HAVE_LMDB
 	if (nzconfig != NULL) {
 		cfg_obj_destroy(named_g_addparser, &nzconfig);
 	}
-#endif /* HAVE_LMDB */
+
 	if (isc_buffer_usedlength(*text) > 0) {
 		(void)putnull(text);
 	}

bin/rndc/rndc.rst

@@ -133,14 +133,13 @@ Currently supported commands are:
    string specified on the command line is the zone configuration text
    that would ordinarily be placed in :iscman:`named.conf`.
 
-   The configuration is saved in a file called ``viewname.nzf`` (or, if
-   :iscman:`named` is compiled with liblmdb, an LMDB database file called
-   ``viewname.nzd``). ``viewname`` is the name of the view, unless the view
-   name contains characters that are incompatible with use as a file
-   name, in which case a cryptographic hash of the view name is used
-   instead. When :iscman:`named` is restarted, the file is loaded into
-   the view configuration so that zones that were added can persist
-   after a restart.
+   The configuration is saved in an LMDB database called
+   ``viewname.nzf``. ``viewname`` is the name of the view, unless the
+   view name contains characters that are incompatible with use as a
+   file name, in which case a cryptographic hash of the view name is
+   used instead. When :iscman:`named` is restarted, the file is loaded
+   into the view configuration so that zones that were added can
+   persist after a restart.
 
    This sample ``addzone`` command adds the zone ``example.com`` to
    the default view:

bin/tests/system/addzone/tests.sh

@@ -36,8 +36,8 @@ n=$((n + 1))
 if [ $ret != 0 ]; then echo_i "failed"; fi
 status=$((status + ret))
 
-# When LMDB support is compiled in, this tests that migration from
-# NZF to NZD occurs during named startup
+# This tests that migration from NZF to NZD occurs during named
+# startup
 echo_i "checking previously added zone ($n)"
 ret=0
 $DIG $DIGOPTS @10.53.0.2 a.previous.example a >dig.out.ns2.$n || ret=1
@@ -47,13 +47,11 @@ n=$((n + 1))
 if [ $ret != 0 ]; then echo_i "failed"; fi
 status=$((status + ret))
 
-if $FEATURETEST --with-lmdb; then
-  echo_i "checking that existing NZF file was renamed after migration ($n)"
-  [ -e ns2/3bf305731dd26307.nzf~ ] || ret=1
-  n=$((n + 1))
-  if [ $ret != 0 ]; then echo_i "failed"; fi
-  status=$((status + ret))
-fi
+echo_i "checking that existing NZF file was renamed after migration ($n)"
+[ -e ns2/3bf305731dd26307.nzf~ ] || ret=1
+n=$((n + 1))
+if [ $ret != 0 ]; then echo_i "failed"; fi
+status=$((status + ret))
 
 echo_i "adding new zone ($n)"
 ret=0
@@ -126,16 +124,6 @@ n=$((n + 1))
 if [ $ret != 0 ]; then echo_i "failed"; fi
 status=$((status + ret))
 
-if ! $FEATURETEST --with-lmdb; then
-  echo_i "verifying no comments in NZF file ($n)"
-  ret=0
-  hcount=$(grep "^# New zone file for view: _default" ns2/3bf305731dd26307.nzf | wc -l)
-  [ $hcount -eq 0 ] || ret=1
-  n=$((n + 1))
-  if [ $ret != 0 ]; then echo_i "failed"; fi
-  status=$((status + ret))
-fi
-
 echo_i "checking rndc showzone with previously added zone ($n)"
 ret=0
 $RNDCCMD 10.53.0.2 showzone previous.example >rndc.out.ns2.$n
@@ -145,13 +133,11 @@ n=$((n + 1))
 if [ $ret != 0 ]; then echo_i "failed"; fi
 status=$((status + ret))
 
-if $FEATURETEST --with-lmdb; then
-  echo_i "checking zone is present in NZD ($n)"
-  ret=0
-  $NZD2NZF ns2/_default.nzd | grep previous.example >/dev/null || ret=1
-  if [ $ret != 0 ]; then echo_i "failed"; fi
-  status=$((status + ret))
-fi
+echo_i "checking zone is present in NZD ($n)"
+ret=0
+$NZD2NZF ns2/_default.nzd | grep previous.example >/dev/null || ret=1
+if [ $ret != 0 ]; then echo_i "failed"; fi
+status=$((status + ret))
 
 echo_i "deleting previously added zone ($n)"
 ret=0
@@ -171,22 +157,10 @@ check_nzd2nzf() (
     && ! grep previous.example nzd2nzf.out.$n >/dev/null
 )
 
-if $FEATURETEST --with-lmdb; then
-  echo_i "checking zone was deleted from NZD ($n)"
-  retry_quiet 10 check_nzd2nzf || ret=1
-  if [ $ret != 0 ]; then echo_i "failed"; fi
-  status=$((status + ret))
-fi
-
-if ! $FEATURETEST --with-lmdb; then
-  echo_i "checking NZF file now has comment ($n)"
-  ret=0
-  hcount=$(grep "^# New zone file for view: _default" ns2/3bf305731dd26307.nzf | wc -l)
-  [ $hcount -eq 1 ] || ret=1
-  n=$((n + 1))
-  if [ $ret != 0 ]; then echo_i "failed"; fi
-  status=$((status + ret))
-fi
+echo_i "checking zone was deleted from NZD ($n)"
+retry_quiet 10 check_nzd2nzf || ret=1
+if [ $ret != 0 ]; then echo_i "failed"; fi
+status=$((status + ret))
 
 echo_i "deleting newly added zone added.example ($n)"
 ret=0
@@ -508,24 +482,12 @@ n=$((n + 1))
 if [ $ret != 0 ]; then echo_i "failed"; fi
 status=$((status + ret))
 
-if ! $FEATURETEST --with-lmdb; then
-  echo_i "checking new NZF file has comment ($n)"
-  ret=0
-  hcount=$(grep "^# New zone file for view: external" ns2/external.nzf | wc -l)
-  [ $hcount -eq 1 ] || ret=1
-  n=$((n + 1))
-  if [ $ret != 0 ]; then echo_i "failed"; fi
-  status=$((status + ret))
-fi
-
-if $FEATURETEST --with-lmdb; then
-  echo_i "verifying added.example in external view created an external.nzd DB ($n)"
-  ret=0
-  [ -e ns2/external.nzd ] || ret=1
-  n=$((n + 1))
-  if [ $ret != 0 ]; then echo_i "failed"; fi
-  status=$((status + ret))
-fi
+echo_i "verifying added.example in external view created an external.nzd DB ($n)"
+ret=0
+[ -e ns2/external.nzd ] || ret=1
+n=$((n + 1))
+if [ $ret != 0 ]; then echo_i "failed"; fi
+status=$((status + ret))
 
 echo_i "checking rndc reload causes named to reload the external view's new zone config ($n)"
 ret=0
@@ -544,11 +506,7 @@ status=$((status + ret))
 
 echo_i "checking rndc showzone with newly added zone ($n)"
 _check_rndc_showzone_newly_added() (
-  if ! $FEATURETEST --with-lmdb; then
-    expected='zone "added.example" in external { type primary; file "added.db"; };'
-  else
-    expected='zone "added.example" { type primary; file "added.db"; };'
-  fi
+  expected='zone "added.example" { type primary; file "added.db"; };'
   $RNDCCMD 10.53.0.2 showzone added.example in external >rndc.out.ns2.$n 2>/dev/null \
     && [ "$(cat rndc.out.ns2.$n)" = "$expected" ]
 )
@@ -651,13 +609,8 @@ n=$((n + 1))
 if [ $ret != 0 ]; then echo_i "failed"; fi
 status=$((status + ret))
 
-if $FEATURETEST --with-lmdb; then
-  echo_i "checking NZD file was created in new-zones-directory ($n)"
-  expect=ns2/new-zones/directory.nzd
-else
-  echo_i "checking NZF file was created in new-zones-directory ($n)"
-  expect=ns2/new-zones/directory.nzf
-fi
+echo_i "checking NZD file was created in new-zones-directory ($n)"
+expect=ns2/new-zones/directory.nzd
 $RNDCCMD 10.53.0.2 sync 'added.example IN directory' 2>&1 | sed 's/^/I:ns2 /'
 sleep 2
 [ -e "$expect" ] || ret=1
@@ -693,19 +646,6 @@ n=$((n + 1))
 if [ $ret != 0 ]; then echo_i "failed"; fi
 status=$((status + ret))
 
-if ! $FEATURETEST --with-lmdb; then
-  echo_i "check that addzone is fully reversed on failure (--with-lmdb=no) ($n)"
-  ret=0
-  $RNDCCMD 10.53.0.3 addzone "test1.baz" '{ type primary; file "e.db"; };' >/dev/null 2>&1 || ret=1
-  $RNDCCMD 10.53.0.3 addzone "test2.baz" '{ type primary; file "dne.db"; };' >/dev/null 2>&1 && ret=1
-  $RNDCCMD 10.53.0.3 addzone "test3.baz" '{ type primary; file "e.db"; };' >/dev/null 2>&1 || ret=1
-  $RNDCCMD 10.53.0.3 delzone "test3.baz" >/dev/null 2>&1 || ret=1
-  grep test2.baz ns3/_default.nzf >/dev/null && ret=1
-  n=$((n + 1))
-  if [ $ret != 0 ]; then echo_i "failed"; fi
-  status=$((status + ret))
-fi
-
 _check_version_bind() (
   $DIG $DIGOPTS @10.53.0.3 version.bind txt ch >dig.out.test$n \
     && grep "status: NOERROR" dig.out.test$n >/dev/null

bin/tests/system/feature-test.c

@@ -54,7 +54,6 @@ usage(void) {
 	fprintf(stderr, "\t--tsan\n");
 	fprintf(stderr, "\t--with-dlz-filesystem\n");
 	fprintf(stderr, "\t--with-libidn2\n");
-	fprintf(stderr, "\t--with-lmdb\n");
 	fprintf(stderr, "\t--with-libnghttp2\n");
 	fprintf(stderr, "\t--with-zlib\n");
 }
@@ -238,14 +237,6 @@ main(int argc, char **argv) {
 #endif /* ifdef HAVE_LIBIDN2 */
 	}
 
-	if (strcmp(argv[1], "--with-lmdb") == 0) {
-#ifdef HAVE_LMDB
-		return 0;
-#else  /* ifdef HAVE_LMDB */
-		return 1;
-#endif /* ifdef HAVE_LMDB */
-	}
-
 	if (strcmp(argv[1], "--with-libnghttp2") == 0) {
 #ifdef HAVE_LIBNGHTTP2
 		return 0;

bin/tests/system/nzd2nzf/prereq.sh

@@ -13,8 +13,5 @@
 
 . ../conf.sh
 
-$FEATURETEST --with-lmdb || {
-  echo_i "This test requires LMDB support." >&2
-  exit 255
-}
+$FEATURETEST
 exit 0

bin/tools/Makefile.am

@@ -2,18 +2,21 @@ include $(top_srcdir)/Makefile.top
 
 AM_CPPFLAGS +=			\
 	$(LIBISC_CFLAGS)	\
-	$(LIBDNS_CFLAGS)
+	$(LIBDNS_CFLAGS)	\
+	$(LMDB_CFLAGS)
 
 LDADD +=			\
 	$(LIBDNS_LIBS)		\
-	$(LIBISC_LIBS)
+	$(LIBISC_LIBS)		\
+	$(LMDB_LIBS)
 
 bin_PROGRAMS =			\
 	arpaname		\
 	mdig			\
 	named-journalprint	\
 	named-rrchecker		\
-	nsec3hash
+	nsec3hash		\
+	named-nzd2nzf
 
 arpaname_LDADD =		\
 	$(LIBISC_LIBS)
@@ -32,17 +35,3 @@ dnstap_read_LDADD =		\
 	$(LIBISC_LIBS)		\
 	$(DNSTAP_LIBS)
 endif
-
-if HAVE_LMDB
-bin_PROGRAMS +=			\
-	named-nzd2nzf
-
-named_nzd2nzf_CPPFLAGS =		\
-	$(AM_CPPFLAGS)		\
-	$(LMDB_CFLAGS)
-
-named_nzd2nzf_LDADD =		\
-	$(LIBISC_LIBS)		\
-	$(LMDB_LIBS)
-
-endif

bin/tools/named-nzd2nzf.c

@@ -11,14 +11,11 @@
  * information regarding copyright ownership.
  */
 
-#ifndef HAVE_LMDB
-#error This program requires the LMDB library.
-#endif /* ifndef HAVE_LMDB */
-
-#include <lmdb.h>
 #include <stdio.h>
 #include <stdlib.h>
 
+#include <isc/lmdb.h>
+
 #include <dns/view.h>
 
 int

configure.ac

@@ -749,43 +749,13 @@ AC_SUBST([KRB5_CFLAGS])
 AC_SUBST([KRB5_LIBS])
 
 #
-# was --with-lmdb specified?
+# LMDB is mandatory
 #
+PKG_CHECK_MODULES([LMDB], [lmdb])
+AX_SAVE_FLAGS([lmdb])
 
-# [pairwise: --with-lmdb=auto, --with-lmdb=yes, --without-lmdb]
-AC_ARG_WITH([lmdb],
-	    [AS_HELP_STRING([--with-lmdb=@<:@PATH@:>@],
-			    [use LMDB library @<:@default=auto@:>@, optionally specify the prefix for lmdb library])],
-	    [:],
-	    [with_lmdb="auto"])
-
-ac_lib_lmdb_found=no
-AS_CASE([$with_lmdb],
-	[no],[],
-	[auto|yes], [PKG_CHECK_MODULES([LMDB], [lmdb],
-				       [ac_lib_lmdb_found=yes],
-				       [for ac_lib_lmdb_path in /usr /usr/local /opt /opt/local; do
-						AX_LIB_LMDB([$ac_lib_lmdb_path],
-							    [ac_lib_lmdb_found=yes
-							     break])
-					done
-				       ])],
-	[AX_LIB_LMDB([$with_lmdb],[ac_lib_lmdb_found=yes])])
-
-# don't fail when in automatic mode
-AS_IF([test "$with_lmdb" = "auto" && test "$ac_lib_lmdb_found" = "no"],
-      [with_lmdb=no])
-
-# hard fail when LMDB requested, but not found
-AS_IF([test "$with_lmdb" != "no" && test "$ac_lib_lmdb_found" != "yes"],
-      [AC_MSG_ERROR([LMDB requested, but not found])])
-
-AS_IF([test "$ac_lib_lmdb_found" = "yes"],
-      [AC_DEFINE([HAVE_LMDB], [1], [Use lmdb library])])
-
-AC_SUBST([LMDB_CFLAGS])
-AC_SUBST([LMDB_LIBS])
-AM_CONDITIONAL([HAVE_LMDB], [test -n "$LMDB_LIBS"])
+CFLAGS="$CFLAGS $LMDB_CFLAGS"
+LIBS="$LIBS $LMDB_LIBS"
 
 #
 # was --with-libxml2 specified?
@@ -1512,7 +1482,7 @@ report() {
 	test -z "$LIBXML2_LIBS" || echo "    XML statistics (--with-libxml2)"
 	test -z "$JSON_C_LIBS" || echo "    JSON statistics (--with-json-c): $JSON_C_CFLAGS $JSON_C_LIBS"
 	test -z "$ZLIB_LIBS" || echo "    HTTP zlib compression (--with-zlib)"
-	test -z "$LMDB_LIBS" || echo "    LMDB database to store configuration for 'addzone' zones (--with-lmdb)"
+	test -z "$LMDB_LIBS" || echo "    LMDB database"
 	test -z "$LIBIDN2_LIBS" || echo "    IDN support (--with-libidn2)"
     fi
 
@@ -1574,7 +1544,7 @@ report() {
     test -z "$LIBXML2_LIBS" && echo "    XML statistics (--with-libxml2)"
     test -z "$JSON_C_LIBS" && echo "    JSON statistics (--with-json-c)"
     test -z "$ZLIB_LIBS" && echo "    HTTP zlib compression (--with-zlib)"
-    test -z "$LMDB_LIBS" && echo "    LMDB database to store configuration for 'addzone' zones (--with-lmdb)"
+    test -z "$LMDB_LIBS" && echo "    LMDB database"
     test -z "$LIBIDN2_LIBS" && echo "    IDN support (--with-libidn2)"
 
     echo "-------------------------------------------------------------------------------"

doc/arm/build.inc.rst

@@ -116,11 +116,6 @@ be linked against ``zlib`` (https://zlib.net/). If this is installed in
 a nonstandard location, specify the prefix using
 ``--with-zlib=/prefix``.
 
-To support storing configuration data for runtime-added zones in an LMDB
-database, the server must be linked with ``liblmdb``
-(https://github.com/LMDB/lmdb). If this is installed in a nonstandard
-location, specify the prefix using ``--with-lmdb=/prefix``.
-
 To support MaxMind GeoIP2 location-based ACLs, the server must be linked
 with ``libmaxminddb`` (https://maxmind.github.io/libmaxminddb/). This is
 turned on by default if the library is found; if the library is

doc/arm/reference.rst

@@ -1360,12 +1360,11 @@ default is used.
    :tags: server
    :short: Sets a maximum size for the memory map of the new-zone database in LMDB database format.
 
-   When :iscman:`named` is built with liblmdb, this option sets a maximum size
-   for the memory map of the new-zone database (NZD) in LMDB database
-   format. This database is used to store configuration information for
-   zones added using :option:`rndc addzone`. Note that this is not the NZD
-   database file size, but the largest size that the database may grow
-   to.
+   This option sets a maximum size for the memory map of the new-zone
+   database (NZD) in LMDB database format. This database is used to
+   store configuration information for zones added using :option:`rndc
+   addzone`. Note that this is not the NZD database file size, but the
+   largest size that the database may grow to.
 
    Because the database file is memory-mapped, its size is limited by
    the address space of the :iscman:`named` process. The default of 32 megabytes
@@ -1994,17 +1993,15 @@ Boolean Options
 
    Newly added zones' configuration parameters are stored so that they
    can persist after the server is restarted. The configuration
-   information is saved in a file called ``viewname.nzf`` (or, if
-   :iscman:`named` is compiled with liblmdb, in an LMDB database file called
-   ``viewname.nzd``). "viewname" is the name of the view, unless the view
-   name contains characters that are incompatible with use as a file
-   name, in which case a cryptographic hash of the view name is used
-   instead.
+   information is saved in an LMDB database file called
+   ``viewname.nzf``. "viewname" is the name of the view, unless the
+   view name contains characters that are incompatible with use as a
+   file name, in which case a cryptographic hash of the view name is
+   used instead.
 
-   Configurations for zones added at runtime are stored either in
-   a new-zone file (NZF) or a new-zone database (NZD), depending on
-   whether :iscman:`named` was linked with liblmdb at compile time. See
-   :ref:`man_rndc` for further details about :option:`rndc addzone`.
+   Configurations for zones added at runtime are stored either in a
+   new-zone database (NZD). See :ref:`man_rndc` for further details
+   about :option:`rndc addzone`.
 
 .. namedconf:statement:: auth-nxdomain
    :tags: query

doc/dev/cfgmgr.md

@@ -0,0 +1,173 @@
+<!--
+Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+
+SPDX-License-Identifier: MPL-2.0
+
+This Source Code Form is subject to the terms of the Mozilla Public
+License, v. 2.0.  If a copy of the MPL was not distributed with this
+file, you can obtain one at https://mozilla.org/MPL/2.0/.
+
+See the COPYRIGHT file distributed with this work for additional
+information regarding copyright ownership.
+-->
+
+## cfgmgr
+
+### Concepts
+
+cfgmgr is a library to (in-memory) store and to interact with
+configuration data in a hierarchical way. A configuration clause can
+be seen as a "box" holding properties accessible by name. A property
+can be of various types (boolean, unsigned integer, string, sockaddr,
+etc.) as well as a clause, making possible to have nested
+clauses. Furthermore, a clause can be repeated: it is possible to have
+several clauses of the same name (or "several instances") at the same
+level (i.e. in the same parent clause).
+
+### API
+
+Public API usage and concepts are documented in
+lib/isc/include/isc/cfgmgr.h. The API is thread-safe and transaction
+based. In order to access to a clause, it must be opened (which starts
+a read or read-write transaction) and eventually closed (which commit
+the transaction, if read-write). Changes made during a transaction are
+visible by the current thread only. Opening nested clauses doesn't
+create sub-transactions: there is only one transaction at the time for
+a given thread opening a top-level clause.
+
+### Implementation
+
+cfgmgr is essentially a wrapper abstracting LMDB, which is providing
+the storage, thread-safe and transactional access. Because LMDB also
+write data on disk and cfgmgr intents to be in-memory only, the LMDB
+files are immediately deleted during the initialization of cfgmgr.
+
+#### Nested and repeatable clauses
+
+LDBM itself is "flat": it stores key-values associations. In order to
+model nested clauses, cfgmgr dynamically build the key for each value
+using a namespace dot based notation. For example:
+
+```
+foo {
+    bar {
+    	gee: 55;
+    };
+    baz: "abc";
+};
+```
+
+is implemented with the following key-values:
+
+```
+foo.XXX.bar.YYY.gee: 55
+foo.XXX.baz: "abc"
+```
+
+The "XXX" and "YYY" are random numbers identifying a specific clause
+instance. Let's make the configuration a bit more complex:
+
+```
+foo {
+    bar {
+    	gee: 55;
+    };
+    bar {
+    	gee: 234;
+    };
+    baz: "abc";
+};
+```
+
+This is implemented with the following key-values:
+
+```
+foo.XXX.bar.YYY.gee: 55
+foo.XXX.bar.ZZZ.gee: 234
+foo.XXX.baz: "abc"
+```
+
+This makes it easy to differentiate between the two instances of the
+"bar" clause: one is "bar.YYY" while the other is "bar.ZZZ".
+
+The reason a number is used (instead of a name or something else) is
+because LMDB sort the key in a lexicographical way. Also, given a key,
+LMDB is able to give the first key which is equal or bigger. This is
+the crux of how cfgmgr can jump to the next instance of a same clause
+(function `isc_cfgmgr_nextclause`) in one lookup. It takes the key of
+the current clause, increments it by one (which is way simpler than
+incrementing a "string by one"), and asks LMDB to give it back the
+next key equal or bigger than the new one. Example:
+
+- current clause is `foo.1234`
+- cfgmgr then creates the key prefix `foo.1235.`
+- LMDB gives the first key bigger or equals to `foo.1235.`
+
+No matter what's inside `foo.1234` (so no matter the keys starting by
+`foo.1234.`, LMDB returns the first key starting by _at least_
+`foo.1235`, which would be the first key of the next instance of the
+same clause. (If there is no other "foo" clause, nothing is found).
+
+### List properties
+
+named configuration format supports properties holding a list of
+values. cfgmgr approach to implement lists uses the fact that LMDB
+allows duplicate keys and it stores a newly duplicated key after the
+previous ones. A clause "foo" with a property "bar" holding a list of
+integers is implemented by cfgmgr in the following way in LMDB:
+
+```
+foo.XXX.bar: 23
+foo.XXX.bar: 43
+```
+
+(Note there would be another way as LMDB enables to store several
+values for a given key, but it's not flexible enough for cfgmgr: it
+requires providing ahead the size used by all the values. It means
+that adding a new list element would require to allocate a buffer of
+the existing size plus the size of the new element, delete the
+existing key-value from LMDB, and add it again. Dup keys seems to be a
+better fit here.)
+
+### Inheritance (proposal/speculative)
+
+Some named configuration clauses have a concept of inheritance. For
+instance, if a looked-up property is not found in a "view" clause, the
+property will be looked-up in the "options" clause. cfgmgr currently
+doesn't support inheritance, so the following is an API/implementation
+proposal to support-ish it:
+
+- a new API `isc_cfgmgr_fallback("A")` could be called while a clause
+  "B" is opened. Then, cfgmgr would know that if a looked-up property
+  of a clause "B" is not found, then it would internally and
+  synchronously try to lookup the same property from within the clause
+  "A". So this can be seen as "B inherits A properties" from the
+  caller perspective. This API could be used once-per clause (no
+  "multiple inheritance"), and it would be possible to break this
+  relation if needed by calling `isc_cfgmgr_fallback(NULL)`.
+
+- internally, `isc_cfgmgr_fallback` would create a new LMDB key-value
+  `B.0.fallback: "A"`. So when cfgmgr opens a clause it can figure out
+  if it needs to lookup for another clause in case a looked-up
+  property is not found.
+
+- From performance perspective in would make one extra LMDB lookup
+  only if a property name is not found for a clause "B" (so this is
+  likely acceptable). (And of course one extra lookup when opening a
+  clause to find the "clausename.0.fallback" key, but again, that's
+  acceptable.)
+
+- limitation 1: if "B" has multiple instances, only the first instance
+  values would be used. (Which I think is fine for named use case:
+  "options" is not a repeatable clause).
+
+- limitation 2: There won't be any check to make sure "A" actually
+  exists when `isc_cfgmgr_fallback` is called, so can be done at any
+  tine even if "A" doesn't exists yet. It makes initialization time
+  order-independent (so actually not really a limitation), and more
+  importantly it avoids falling into a rabbit hole, for instance, to
+  make sure that if we delete "A" it would remove all the
+  `"other-clause-names.0.fallback: "A"` keys. This is actually the
+  reason I want to call it "fallback" in the API and not
+  "inheritance". It's basically just a "second-chance" if a value is
+  not found, but nothing more.

doc/man/Makefile.am

@@ -100,6 +100,7 @@ man_MANS =				\
 	named-checkzone.1		\
 	named-compilezone.1		\
 	named-journalprint.1		\
+	named-nzd2nzf.1			\
 	named.8				\
 	nsec3hash.1			\
 	rndc-confgen.8			\
@@ -111,11 +112,6 @@ man_MANS +=				\
 	dnstap-read.1
 endif HAVE_DNSTAP
 
-if HAVE_LMDB
-man_MANS +=				\
-	named-nzd2nzf.1
-endif HAVE_LMDB
-
 MANPAGES_IN =				\
 	$(man_MANS:=in)			\
 	dnstap-read.1in			\

doc/misc/options

@@ -165,7 +165,7 @@ options {
 	lame-ttl <duration>;
 	listen-on [ port <integer> ] [ proxy <string> ] [ tls <string> ] [ http <string> ] { <address_match_element>; ... }; // may occur multiple times
 	listen-on-v6 [ port <integer> ] [ proxy <string> ] [ tls <string> ] [ http <string> ] { <address_match_element>; ... }; // may occur multiple times
-	lmdb-mapsize <sizeval>; // optional (only available if configured)
+	lmdb-mapsize <sizeval>;
 	managed-keys-directory <quoted_string>;
 	masterfile-format ( raw | text );
 	masterfile-style ( full | relative );
@@ -449,7 +449,7 @@ view <string> [ <class> ] {
 	}; // may occur multiple times
 	key-directory <quoted_string>;
 	lame-ttl <duration>;
-	lmdb-mapsize <sizeval>; // optional (only available if configured)
+	lmdb-mapsize <sizeval>;
 	masterfile-format ( raw | text );
 	masterfile-style ( full | relative );
 	match-clients { <address_match_element>; ... };

lib/dns/Makefile.am

@@ -267,6 +267,7 @@ libdns_la_CPPFLAGS =		\
 	$(LIBISC_CFLAGS)	\
 	$(LIBURCU_CFLAGS)	\
 	$(LIBUV_CFLAGS)		\
+	$(LMDB_CFLAGS)		\
 	$(OPENSSL_CFLAGS)
 
 libdns_la_LDFLAGS =		\
@@ -277,6 +278,7 @@ libdns_la_LIBADD =		\
 	$(LIBISC_LIBS)		\
 	$(LIBURCU_LIBS)		\
 	$(LIBUV_LIBS)		\
+	$(LMDB_LIBS)		\
 	$(OPENSSL_LIBS)
 
 if HAVE_JSON_C
@@ -326,11 +328,6 @@ libdns_la_CPPFLAGS += $(DNSTAP_CFLAGS)
 libdns_la_LIBADD += $(DNSTAP_LIBS)
 endif
 
-if HAVE_LMDB
-libdns_la_CPPFLAGS += $(LMDB_CFLAGS)
-libdns_la_LIBADD += $(LMDB_LIBS)
-endif
-
 if !HAVE_SYSTEMTAP
 DTRACE_DEPS = libdns_la-xfrin.lo
 DTRACE_OBJS = .libs/libdns_la-xfrin.$(OBJEXT)

lib/dns/include/dns/view.h

@@ -249,19 +249,6 @@ struct dns_view {
 #define DNS_VIEWATTR_ADBSHUTDOWN 0x02
 #define DNS_VIEWATTR_REQSHUTDOWN 0x04
 
-#ifdef HAVE_LMDB
-#define DNS_LMDB_COMMON_FLAGS (MDB_CREATE | MDB_NOSUBDIR | MDB_NOLOCK)
-#ifndef __OpenBSD__
-#define DNS_LMDB_FLAGS (DNS_LMDB_COMMON_FLAGS)
-#else /* __OpenBSD__ */
-/*
- * OpenBSD does not have a unified buffer cache, which requires both reads and
- * writes to be performed using mmap().
- */
-#define DNS_LMDB_FLAGS (DNS_LMDB_COMMON_FLAGS | MDB_WRITEMAP)
-#endif /* __OpenBSD__ */
-#endif /* HAVE_LMDB */
-
 isc_result_t
 dns_view_create(isc_mem_t *mctx, isc_loopmgr_t *loopmgr,
 		dns_dispatchmgr_t *dispmgr, dns_rdataclass_t rdclass,

lib/dns/view.c

@@ -17,15 +17,12 @@
 #include <limits.h>
 #include <stdbool.h>
 
-#ifdef HAVE_LMDB
-#include <lmdb.h>
-#endif /* ifdef HAVE_LMDB */
-
 #include <isc/atomic.h>
 #include <isc/dir.h>
 #include <isc/file.h>
 #include <isc/hash.h>
 #include <isc/lex.h>
+#include <isc/lmdb.h>
 #include <isc/md.h>
 #include <isc/result.h>
 #include <isc/stats.h>
@@ -392,7 +389,6 @@ destroy(dns_view_t *view) {
 		isc_mem_free(view->mctx, view->new_zone_dir);
 		view->new_zone_dir = NULL;
 	}
-#ifdef HAVE_LMDB
 	if (view->new_zone_dbenv != NULL) {
 		mdb_env_close((MDB_env *)view->new_zone_dbenv);
 		view->new_zone_dbenv = NULL;
@@ -401,7 +397,6 @@ destroy(dns_view_t *view) {
 		isc_mem_free(view->mctx, view->new_zone_db);
 		view->new_zone_db = NULL;
 	}
-#endif /* HAVE_LMDB */
 	dns_fwdtable_destroy(&view->fwdtable);
 	dns_aclenv_detach(&view->aclenv);
 	if (view->failcache != NULL) {
@@ -1787,14 +1782,8 @@ dns_view_setnewzones(dns_view_t *view, bool allow, void *cfgctx,
 		     void (*cfg_destroy)(void **), uint64_t mapsize) {
 	isc_result_t result = ISC_R_SUCCESS;
 	char buffer[1024];
-#ifdef HAVE_LMDB
 	MDB_env *env = NULL;
 	int status;
-#endif /* ifdef HAVE_LMDB */
-
-#ifndef HAVE_LMDB
-	UNUSED(mapsize);
-#endif /* ifndef HAVE_LMDB */
 
 	REQUIRE(DNS_VIEW_VALID(view));
 	REQUIRE((cfgctx != NULL && cfg_destroy != NULL) || !allow);
@@ -1804,7 +1793,6 @@ dns_view_setnewzones(dns_view_t *view, bool allow, void *cfgctx,
 		view->new_zone_file = NULL;
 	}
 
-#ifdef HAVE_LMDB
 	if (view->new_zone_dbenv != NULL) {
 		mdb_env_close((MDB_env *)view->new_zone_dbenv);
 		view->new_zone_dbenv = NULL;
@@ -1814,7 +1802,6 @@ dns_view_setnewzones(dns_view_t *view, bool allow, void *cfgctx,
 		isc_mem_free(view->mctx, view->new_zone_db);
 		view->new_zone_db = NULL;
 	}
-#endif /* HAVE_LMDB */
 
 	if (view->new_zone_config != NULL) {
 		view->cfg_destroy(&view->new_zone_config);
@@ -1830,7 +1817,6 @@ dns_view_setnewzones(dns_view_t *view, bool allow, void *cfgctx,
 
 	view->new_zone_file = isc_mem_strdup(view->mctx, buffer);
 
-#ifdef HAVE_LMDB
 	CHECK(nz_legacy(view->new_zone_dir, view->name, "nzd", buffer,
 			sizeof(buffer)));
 
@@ -1866,7 +1852,6 @@ dns_view_setnewzones(dns_view_t *view, bool allow, void *cfgctx,
 
 	view->new_zone_dbenv = env;
 	env = NULL;
-#endif /* HAVE_LMDB */
 
 	view->new_zone_config = cfgctx;
 	view->cfg_destroy = cfg_destroy;
@@ -1878,7 +1863,6 @@ cleanup:
 			view->new_zone_file = NULL;
 		}
 
-#ifdef HAVE_LMDB
 		if (view->new_zone_db != NULL) {
 			isc_mem_free(view->mctx, view->new_zone_db);
 			view->new_zone_db = NULL;
@@ -1886,7 +1870,7 @@ cleanup:
 		if (env != NULL) {
 			mdb_env_close(env);
 		}
-#endif /* HAVE_LMDB */
+
 		view->new_zone_config = NULL;
 		view->cfg_destroy = NULL;
 	}

lib/isc/Makefile.am

@@ -14,6 +14,7 @@ libisc_la_HEADERS =			\
 	include/isc/base32.h		\
 	include/isc/base64.h		\
 	include/isc/buffer.h		\
+	include/isc/cfgmgr.h		\
 	include/isc/commandline.h	\
 	include/isc/condition.h		\
 	include/isc/counter.h		\
@@ -44,6 +45,7 @@ libisc_la_HEADERS =			\
 	include/isc/lang.h		\
 	include/isc/lex.h		\
 	include/isc/list.h		\
+	include/isc/lmdb.h		\
 	include/isc/log.h		\
 	include/isc/loop.h		\
 	include/isc/magic.h		\
@@ -122,6 +124,7 @@ libisc_la_SOURCES =		\
 	backtrace.c		\
 	base32.c		\
 	base64.c		\
+	cfgmgr.c		\
 	commandline.c		\
 	condition.c		\
 	counter.c		\
@@ -214,6 +217,7 @@ libisc_la_CPPFLAGS =		\
 	$(AM_CPPFLAGS)		\
 	$(LIBISC_CFLAGS)	\
 	$(LIBUV_CFLAGS)		\
+	$(LMDB_CFLAGS)		\
 	$(OPENSSL_CFLAGS)	\
 	$(ZLIB_CFLAGS)
 
@@ -223,6 +227,7 @@ libisc_la_LDFLAGS =		\
 
 libisc_la_LIBADD =		\
 	$(LIBUV_LIBS)		\
+	$(LMDB_LIBS)		\
 	$(OPENSSL_LIBS)		\
 	$(ZLIB_LIBS)
 

lib/isc/cfgmgr.c

@@ -0,0 +1,765 @@
+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, you can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <isc/cfgmgr.h>
+#include <isc/list.h>
+#include <isc/lmdb.h>
+#include <isc/mem.h>
+#include <isc/random.h>
+#include <isc/rwlock.h>
+#include <isc/thread.h>
+#include <isc/util.h>
+
+/*
+ * See MDB_MAXKEYSIZE documentation, but not accessible as defined in
+ * internal implementation. Having key with longer size won't work
+ * with LMDB. The value is 511 by default.
+ */
+#define BUFLEN 511
+
+typedef struct openedclause openedclause_t;
+struct openedclause {
+	char *name;
+	uint32_t id;
+	ISC_LINK(openedclause_t) link;
+};
+typedef ISC_LIST(openedclause_t) openedclauses_t;
+
+typedef struct {
+	openedclauses_t openedclauses;
+	char *prefix;
+	char *buffer;
+	MDB_cursor *cursor;
+	MDB_txn *txn;
+	bool readonly;
+} context_t;
+
+static isc_rwlock_t isc__cfgmgr_lock;
+static isc_mem_t *isc__cfgmgr_mctx = NULL;
+static MDB_env *isc__cfgmgr_env = NULL;
+static thread_local context_t isc__cfgmgr_ctx =
+	(context_t){ .openedclauses = ISC_LIST_INITIALIZER,
+		     .prefix = NULL,
+		     .buffer = NULL,
+		     .cursor = NULL,
+		     .txn = NULL,
+		     .readonly = false };
+
+static unsigned long
+isc__cfgmgr_parseid(const char *dbkey) {
+	uint32_t id = 0;
+	size_t idstarts;
+	size_t idends;
+	size_t keylen;
+
+	REQUIRE(isc__cfgmgr_ctx.buffer != NULL);
+	REQUIRE(dbkey != NULL);
+
+	/*
+	 * starts checking after the prefix dot delimiter, i.e.  if
+	 * prefix is "foo" then the key will be "foo.1235..." so the
+	 * start of the id (character 1) is at character index 4
+	 */
+	idstarts = strlen(isc__cfgmgr_ctx.buffer);
+	INSIST(idstarts > 0 && isc__cfgmgr_ctx.buffer[idstarts - 1] == '.');
+	idends = idstarts;
+
+	/*
+	 * Cutting the key form the dot after the identifier
+	 */
+	keylen = strlen(dbkey);
+	REQUIRE(keylen > idends);
+	while (dbkey[idends] != '.') {
+		idends++;
+		INSIST(keylen > idends);
+	}
+
+	/*
+	 * strtoul stops as soon as it doesn't encounter a non-digit
+	 * number, so no need to get an extra buffer, copy the dbkey
+	 * and add a null byte after the last digit.
+	 */
+	id = strtoul(dbkey + idstarts, NULL, 10);
+	ENSURE(id > 0);
+	return id;
+}
+
+isc_result_t
+isc_cfgmgr_init(isc_mem_t *mctx, const char *dbpath) {
+	int result = ISC_R_SUCCESS;
+	char dbname[BUFLEN];
+	char dblockname[BUFLEN];
+	uint32_t random;
+
+	REQUIRE(ISC_LIST_EMPTY(isc__cfgmgr_ctx.openedclauses));
+	REQUIRE(isc__cfgmgr_ctx.prefix == NULL);
+	REQUIRE(isc__cfgmgr_ctx.buffer == NULL);
+	REQUIRE(isc__cfgmgr_ctx.cursor == NULL);
+	REQUIRE(isc__cfgmgr_ctx.txn == NULL);
+	REQUIRE(isc__cfgmgr_mctx == NULL);
+	REQUIRE(isc__cfgmgr_env == NULL);
+	REQUIRE(mctx != NULL);
+	REQUIRE(dbpath != NULL);
+
+	isc_rwlock_init(&isc__cfgmgr_lock);
+
+	isc_mem_attach(mctx, &isc__cfgmgr_mctx);
+	INSIST(isc__cfgmgr_mctx != NULL);
+
+	result = mdb_env_create(&isc__cfgmgr_env);
+	if (result != 0) {
+		result = ISC_R_FAILURE;
+		goto cleanup;
+	}
+
+	INSIST(isc__cfgmgr_env != NULL);
+	random = isc_random32();
+
+	/*
+	 * Because LMDB also create a <dbname>-lock file, we also need
+	 * to build it (even if not passed to LMDB itself) so we can
+	 * immediately delete it
+	 */
+	REQUIRE(snprintf(dbname, BUFLEN, "%s-%" PRIu32, dbpath, random) <
+		BUFLEN);
+	REQUIRE(snprintf(dblockname, BUFLEN, "%s-%" PRIu32 "-lock", dbpath,
+			 random) < BUFLEN);
+
+	/*
+	 * Using MDB_NOSYNC as it avoids force disk flush after a
+	 * transaction. It's quicker and in our case we don't need it
+	 * as we delete the only link to the inode right away (so disk
+	 * corruption doesn't matter: as soon as the process is dead,
+	 * the disk data is dead as well)
+	 */
+	result = mdb_env_open(isc__cfgmgr_env, dbname,
+			      MDB_NOSYNC | MDB_NOSUBDIR | MDB_NOLOCK, 0600);
+	if (result != 0) {
+		result = ISC_R_FAILURE;
+		goto cleanup;
+	}
+
+	remove(dbname);
+	remove(dblockname);
+
+	goto out;
+
+cleanup:
+	if (isc__cfgmgr_env != NULL) {
+		mdb_env_close(isc__cfgmgr_env);
+		isc__cfgmgr_env = NULL;
+	}
+
+out:
+	return result;
+}
+
+void
+isc_cfgmgr_deinit(void) {
+	/*
+	 * Well, I'm on the fence about those context checks for the
+	 * deinit function: it's good to have, but because the context
+	 * data is thread specific, it doesn't means there isn't a
+	 * thread somewhere which haven't released its opened clauses
+	 * and not the one calling isc_cfgmgr_deinit, then we'll leak
+	 * those - even if unlikely as this function should be call
+	 * late in shutdown flow. (That said it's just an extra clue,
+	 * because destroying the context will assert anyway, as some
+	 * memory would not be released yet).
+	 */
+	REQUIRE(ISC_LIST_EMPTY(isc__cfgmgr_ctx.openedclauses));
+	REQUIRE(isc__cfgmgr_ctx.prefix == NULL);
+	REQUIRE(isc__cfgmgr_ctx.buffer == NULL);
+	REQUIRE(isc__cfgmgr_ctx.cursor == NULL);
+	REQUIRE(isc__cfgmgr_ctx.txn == NULL);
+	REQUIRE(isc__cfgmgr_mctx != NULL);
+	REQUIRE(isc__cfgmgr_env != NULL);
+	mdb_env_close(isc__cfgmgr_env);
+	isc__cfgmgr_env = NULL;
+	isc_mem_detach(&isc__cfgmgr_mctx);
+	INSIST(isc__cfgmgr_mctx == NULL);
+}
+
+static void
+isc__cfgmgr_buildkey(const char *name, bool trailingdot) {
+	size_t written;
+	const char *prefix = "";
+	const char *dot = trailingdot ? "." : "";
+
+	REQUIRE(name != NULL);
+	REQUIRE(isc__cfgmgr_ctx.buffer != NULL);
+	REQUIRE(isc__cfgmgr_ctx.prefix != NULL);
+
+	if (ISC_LIST_EMPTY(isc__cfgmgr_ctx.openedclauses) == false) {
+		prefix = isc__cfgmgr_ctx.prefix;
+	}
+
+	written = snprintf(isc__cfgmgr_ctx.buffer, BUFLEN, "%s%s%s", prefix,
+			   name, dot);
+	INSIST(written <= BUFLEN);
+}
+
+static isc_result_t
+isc__cfgmgr_findclause(const char *name, unsigned long *id) {
+	isc_result_t result = ISC_R_SUCCESS;
+	MDB_val dbkey;
+	size_t dotpos = 0;
+
+	REQUIRE(name != NULL);
+
+	isc__cfgmgr_buildkey(name, true);
+	dotpos = strlen(isc__cfgmgr_ctx.buffer) - 1;
+	dbkey = (MDB_val){ .mv_size = strlen(isc__cfgmgr_ctx.buffer) + 1,
+			   .mv_data = (char *)isc__cfgmgr_ctx.buffer };
+
+	/*
+	 * Let's use LMDB prefix search because the first clause
+	 * key/val won't just have the "name.id" prefix, but also the
+	 * id and the first property name (so "name.id.prop").
+	 */
+	if (mdb_cursor_get(isc__cfgmgr_ctx.cursor, &dbkey, NULL,
+			   MDB_SET_RANGE) != 0)
+	{
+		result = ISC_R_NOTFOUND;
+		goto out;
+	}
+
+	/*
+	 * LMDB found a key which starts by "prefix", so let's make
+	 * sure it's actually the same prefix by checking the found
+	 * key has an immediate leading dot
+	 */
+	if (dbkey.mv_size <= dotpos || ((char *)dbkey.mv_data)[dotpos] != '.') {
+		result = ISC_R_NOTFOUND;
+		goto out;
+	}
+
+	/*
+	 * We found the clause. Let's extract its ID
+	 */
+	*id = isc__cfgmgr_parseid(dbkey.mv_data);
+
+out:
+	return result;
+}
+
+static void
+isc__cfgmgr_updateprefix(void) {
+	size_t written = 0;
+
+	REQUIRE(isc__cfgmgr_ctx.prefix != NULL);
+
+	if (ISC_LIST_EMPTY(isc__cfgmgr_ctx.openedclauses)) {
+		return;
+	}
+
+	for (openedclause_t *clause =
+		     ISC_LIST_TAIL(isc__cfgmgr_ctx.openedclauses);
+	     clause != NULL; clause = ISC_LIST_PREV(clause, link))
+	{
+		written += snprintf(isc__cfgmgr_ctx.prefix + written,
+				    BUFLEN - written, "%s.%" PRIu32 ".",
+				    clause->name, clause->id);
+		INSIST(written <= BUFLEN);
+	}
+}
+
+static void
+isc__cfgmgr_pushclause(const char *name, unsigned long id) {
+	openedclause_t *clause = isc_mem_get(isc__cfgmgr_mctx, sizeof(*clause));
+
+	*clause = (openedclause_t){
+		.name = isc_mem_allocate(isc__cfgmgr_mctx, strlen(name) + 1),
+		.id = id,
+		.link = ISC_LINK_INITIALIZER,
+	};
+	strcpy(clause->name, name);
+	ENSURE(clause->id > 0);
+	ISC_LIST_PREPEND(isc__cfgmgr_ctx.openedclauses, clause, link);
+	isc__cfgmgr_updateprefix();
+}
+
+static void
+isc__cfgmgr_freectx(void) {
+	REQUIRE(isc__cfgmgr_ctx.buffer != NULL &&
+		isc__cfgmgr_ctx.prefix != NULL);
+
+	isc_mem_free(isc__cfgmgr_mctx, isc__cfgmgr_ctx.buffer);
+	isc_mem_free(isc__cfgmgr_mctx, isc__cfgmgr_ctx.prefix);
+	isc__cfgmgr_ctx.txn = NULL;
+	isc__cfgmgr_ctx.cursor = NULL;
+}
+
+static isc_result_t
+isc__cfgmgr_starttransaction(bool readonly) {
+	MDB_dbi dbi;
+
+	isc_rwlock_lock(&isc__cfgmgr_lock,
+			readonly ? isc_rwlocktype_read : isc_rwlocktype_write);
+
+	if (mdb_txn_begin(isc__cfgmgr_env, NULL, readonly ? MDB_RDONLY : 0,
+			  &isc__cfgmgr_ctx.txn) != 0)
+	{
+		goto failure;
+	}
+	INSIST(isc__cfgmgr_ctx.txn != NULL);
+
+	if (mdb_dbi_open(isc__cfgmgr_ctx.txn, NULL, MDB_CREATE | MDB_DUPSORT,
+			 &dbi) != 0)
+	{
+		goto failure;
+	}
+
+	if (mdb_cursor_open(isc__cfgmgr_ctx.txn, dbi,
+			    &isc__cfgmgr_ctx.cursor) != 0)
+	{
+		goto failure;
+	}
+	INSIST(isc__cfgmgr_ctx.cursor != NULL);
+	isc__cfgmgr_ctx.readonly = readonly;
+	isc__cfgmgr_ctx.buffer = isc_mem_allocate(isc__cfgmgr_mctx, BUFLEN);
+	isc__cfgmgr_ctx.prefix = isc_mem_allocate(isc__cfgmgr_mctx, BUFLEN);
+
+	return ISC_R_SUCCESS;
+
+failure:
+	if (isc__cfgmgr_ctx.txn) {
+		mdb_txn_abort(isc__cfgmgr_ctx.txn);
+		isc__cfgmgr_freectx();
+		isc_rwlock_unlock(&isc__cfgmgr_lock,
+				  isc__cfgmgr_ctx.readonly
+					  ? isc_rwlocktype_read
+					  : isc_rwlocktype_write);
+	}
+	ENSURE(isc__cfgmgr_ctx.buffer == NULL &&
+	       isc__cfgmgr_ctx.prefix == NULL);
+
+	return ISC_R_FAILURE;
+}
+
+static isc_result_t
+isc__cfgmgr_opentoplevel(const char *name, bool readonly) {
+	isc_result_t result = ISC_R_SUCCESS;
+	unsigned long id = 0;
+
+	REQUIRE(isc__cfgmgr_env != NULL);
+	REQUIRE(name != NULL);
+	REQUIRE(ISC_LIST_EMPTY(isc__cfgmgr_ctx.openedclauses));
+	REQUIRE(isc__cfgmgr_ctx.prefix == NULL);
+	REQUIRE(isc__cfgmgr_ctx.buffer == NULL);
+	REQUIRE(isc__cfgmgr_ctx.txn == NULL);
+	REQUIRE(isc__cfgmgr_ctx.cursor == NULL);
+
+	/*
+	 * We're opening a clause at top-level, so let's start a
+	 * transaction
+	 */
+	result = isc__cfgmgr_starttransaction(readonly);
+	if (result != ISC_R_SUCCESS) {
+		goto cleanup;
+	}
+
+	/*
+	 * Now let's try to find the clause...
+	 */
+	result = isc__cfgmgr_findclause(name, &id);
+	if (result != ISC_R_SUCCESS) {
+		goto cleanup;
+	}
+
+	/*
+	 * The clause is found, let's enqueue the clause in
+	 * context. the clause is now opened
+	 */
+	isc__cfgmgr_pushclause(name, id);
+	goto out;
+
+cleanup:
+	if (isc__cfgmgr_ctx.txn) {
+		mdb_cursor_close(isc__cfgmgr_ctx.cursor);
+		mdb_txn_abort(isc__cfgmgr_ctx.txn);
+		isc__cfgmgr_freectx();
+		isc_rwlock_unlock(&isc__cfgmgr_lock,
+				  isc__cfgmgr_ctx.readonly
+					  ? isc_rwlocktype_read
+					  : isc_rwlocktype_write);
+	}
+
+out:
+	return result;
+}
+
+static isc_result_t
+isc__cfgmgr_opennested(const char *name) {
+	isc_result_t result = ISC_R_SUCCESS;
+	unsigned long id = 0;
+
+	REQUIRE(isc__cfgmgr_env != NULL);
+	REQUIRE(name != NULL);
+	REQUIRE(ISC_LIST_EMPTY(isc__cfgmgr_ctx.openedclauses) == false);
+	REQUIRE(isc__cfgmgr_ctx.prefix != NULL);
+	REQUIRE(isc__cfgmgr_ctx.buffer != NULL);
+	REQUIRE(isc__cfgmgr_ctx.txn != NULL);
+	REQUIRE(isc__cfgmgr_ctx.cursor != NULL);
+
+	result = isc__cfgmgr_findclause(name, &id);
+	if (result != ISC_R_SUCCESS) {
+		goto out;
+	}
+
+	isc__cfgmgr_pushclause(name, id);
+
+out:
+	return result;
+}
+
+isc_result_t
+isc_cfgmgr_openrw(const char *name) {
+	return isc__cfgmgr_opentoplevel(name, false);
+}
+
+isc_result_t
+isc_cfgmgr_open(const char *name) {
+	if (ISC_LIST_EMPTY(isc__cfgmgr_ctx.openedclauses)) {
+		return isc__cfgmgr_opentoplevel(name, true);
+	}
+
+	return isc__cfgmgr_opennested(name);
+}
+
+static void
+popclause(void) {
+	openedclause_t *clause = ISC_LIST_HEAD(isc__cfgmgr_ctx.openedclauses);
+
+	ISC_LIST_UNLINK(isc__cfgmgr_ctx.openedclauses, clause, link);
+	isc_mem_free(isc__cfgmgr_mctx, clause->name);
+	isc_mem_put(isc__cfgmgr_mctx, clause, sizeof(*clause));
+	isc__cfgmgr_updateprefix();
+}
+
+isc_result_t
+isc_cfgmgr_close(void) {
+	isc_result_t result = ISC_R_SUCCESS;
+
+	REQUIRE(isc__cfgmgr_env != NULL);
+	REQUIRE(ISC_LIST_EMPTY(isc__cfgmgr_ctx.openedclauses) == false);
+	REQUIRE(isc__cfgmgr_ctx.prefix != NULL);
+	REQUIRE(isc__cfgmgr_ctx.buffer != NULL);
+	REQUIRE(isc__cfgmgr_ctx.txn != NULL);
+	REQUIRE(isc__cfgmgr_ctx.cursor != NULL);
+
+	popclause();
+	if (ISC_LIST_EMPTY(isc__cfgmgr_ctx.openedclauses)) {
+		mdb_cursor_close(isc__cfgmgr_ctx.cursor);
+
+		if (mdb_txn_commit(isc__cfgmgr_ctx.txn) != 0) {
+			result = ISC_R_FAILURE;
+		}
+
+		isc__cfgmgr_freectx();
+		isc_rwlock_unlock(&isc__cfgmgr_lock,
+				  isc__cfgmgr_ctx.readonly
+					  ? isc_rwlocktype_read
+					  : isc_rwlocktype_write);
+	}
+
+	return result;
+}
+
+isc_result_t
+isc_cfgmgr_delclause(void) {
+	MDB_val dbkey;
+
+	REQUIRE(isc__cfgmgr_env != NULL);
+	REQUIRE(ISC_LIST_EMPTY(isc__cfgmgr_ctx.openedclauses) == false);
+	REQUIRE(isc__cfgmgr_ctx.prefix != NULL);
+	REQUIRE(isc__cfgmgr_ctx.buffer != NULL);
+	REQUIRE(isc__cfgmgr_ctx.txn != NULL);
+	REQUIRE(isc__cfgmgr_ctx.cursor != NULL);
+	REQUIRE(isc__cfgmgr_ctx.readonly == false);
+
+	dbkey = (MDB_val){ .mv_size = strlen(isc__cfgmgr_ctx.prefix) + 1,
+			   .mv_data = isc__cfgmgr_ctx.prefix };
+	do {
+		/*
+		 * even though the key is modified by mdb_cursor_get
+		 * on each run (and is the exact current key) we're
+		 * good: MDB_SET_RANGE of the current key will point
+		 * to the next one with the same prefix as soon it
+		 * gets deleted
+		 */
+		int mdbres = mdb_cursor_get(isc__cfgmgr_ctx.cursor, &dbkey,
+					    NULL, MDB_SET_RANGE);
+		if (mdbres == MDB_NOTFOUND) {
+			break;
+		}
+
+		if (strncmp(isc__cfgmgr_ctx.prefix, dbkey.mv_data,
+			    strlen(isc__cfgmgr_ctx.prefix)) != 0)
+		{
+			break;
+		}
+
+		/*
+		 * NDB_NODUPDATA not strictly needed here, but we
+		 * avoid extra iterations if there are lists in the
+		 * clause
+		 */
+		REQUIRE(mdb_cursor_del(isc__cfgmgr_ctx.cursor, MDB_NODUPDATA) ==
+			0);
+	} while (1);
+
+	return isc_cfgmgr_close();
+}
+
+isc_result_t
+isc_cfgmgr_newclause(const char *name) {
+	isc_result_t result = ISC_R_SUCCESS;
+
+	REQUIRE(name != NULL);
+	REQUIRE(isc__cfgmgr_env != NULL);
+
+	if (isc__cfgmgr_ctx.txn == NULL || isc__cfgmgr_ctx.cursor == NULL) {
+		REQUIRE(isc__cfgmgr_ctx.prefix == NULL);
+		REQUIRE(isc__cfgmgr_ctx.buffer == NULL);
+		REQUIRE(isc__cfgmgr_ctx.txn == NULL);
+		REQUIRE(isc__cfgmgr_ctx.cursor == NULL);
+		result = isc__cfgmgr_starttransaction(false);
+	}
+
+	if (result == ISC_R_SUCCESS) {
+		INSIST(isc__cfgmgr_ctx.txn != NULL);
+		INSIST(isc__cfgmgr_ctx.buffer != NULL);
+		INSIST(isc__cfgmgr_ctx.cursor != NULL);
+		INSIST(isc__cfgmgr_ctx.readonly == false);
+		isc__cfgmgr_pushclause(name, isc_random32());
+		INSIST(isc__cfgmgr_ctx.prefix != NULL);
+	}
+
+	return result;
+}
+
+isc_result_t
+isc_cfgmgr_nextclause(void) {
+	isc_result_t result = ISC_R_SUCCESS;
+	MDB_val dbkey;
+	uint32_t id;
+	size_t idstarts = 0;
+	size_t written = 0;
+
+	REQUIRE(isc__cfgmgr_env != NULL);
+	REQUIRE(ISC_LIST_EMPTY(isc__cfgmgr_ctx.openedclauses) == false);
+	REQUIRE(isc__cfgmgr_ctx.prefix != NULL);
+	REQUIRE(isc__cfgmgr_ctx.buffer != NULL);
+	REQUIRE(isc__cfgmgr_ctx.txn != NULL);
+	REQUIRE(isc__cfgmgr_ctx.cursor != NULL);
+
+	/*
+	 * Let's pick the very next id (even if doesn't exists) of the
+	 * current clause
+	 */
+	id = ISC_LIST_HEAD(isc__cfgmgr_ctx.openedclauses)->id + 1;
+
+	/*
+	 * Variant of updateprefix, but this time we put a incremented
+	 * key for the currently opened clause. We also keep track of
+	 * when the current clause id starts.
+	 */
+	for (openedclause_t *clause =
+		     ISC_LIST_TAIL(isc__cfgmgr_ctx.openedclauses);
+	     clause != NULL; clause = ISC_LIST_PREV(clause, link))
+	{
+		bool last = ISC_LIST_PREV(clause, link) == NULL;
+
+		if (last) {
+			idstarts = written + strlen(clause->name) + 1;
+		}
+		written += snprintf(isc__cfgmgr_ctx.buffer + written,
+				    BUFLEN - written, "%s.%" PRIu32 ".",
+				    clause->name, last ? id : clause->id);
+		INSIST(written <= BUFLEN);
+	}
+	INSIST(idstarts > 0);
+	dbkey = (MDB_val){ .mv_size = strlen(isc__cfgmgr_ctx.buffer) + 1,
+			   .mv_data = isc__cfgmgr_ctx.buffer };
+
+	/*
+	 * Looking for similar prefix name but with a bigger
+	 * id. Thanks for LMDB sort and MDB_SET_RANGE, we'll bump to
+	 * the first key/val of the next clause of the same type
+	 */
+	if (mdb_cursor_get(isc__cfgmgr_ctx.cursor, &dbkey, NULL,
+			   MDB_SET_RANGE) != 0)
+	{
+		result = ISC_R_NOMORE;
+		goto out;
+	}
+
+	/*
+	 * Let's check if next found clause is same name
+	 */
+	REQUIRE(idstarts < BUFLEN);
+	if (strncmp(isc__cfgmgr_ctx.buffer, dbkey.mv_data, idstarts) != 0) {
+		result = ISC_R_NOMORE;
+		goto out;
+	}
+
+	/*
+	 * Gets the actual id of the next clause (so let's get rid of
+	 * the fake id part from the prefix). Instead of pop/push a
+	 * new clause, let's simply replace the id and update the
+	 * prefix.
+	 */
+	isc__cfgmgr_ctx.buffer[idstarts] = 0;
+	ISC_LIST_HEAD(isc__cfgmgr_ctx.openedclauses)->id =
+		isc__cfgmgr_parseid(dbkey.mv_data);
+	isc__cfgmgr_updateprefix();
+
+out:
+	return result;
+}
+
+static isc_result_t
+isc__cfgmgr_getval(const char *name, isc_cfgmgr_val_t *value) {
+	isc_result_t result = ISC_R_SUCCESS;
+	MDB_val dbkey;
+	MDB_val dbval;
+	const int opt = name == NULL ? MDB_NEXT_DUP : MDB_SET;
+
+	REQUIRE(isc__cfgmgr_env != NULL);
+	REQUIRE(ISC_LIST_EMPTY(isc__cfgmgr_ctx.openedclauses) == false);
+	REQUIRE(isc__cfgmgr_ctx.prefix != NULL);
+	REQUIRE(isc__cfgmgr_ctx.buffer != NULL);
+	REQUIRE(isc__cfgmgr_ctx.txn != NULL);
+	REQUIRE(isc__cfgmgr_ctx.cursor != NULL);
+	REQUIRE(value != NULL);
+
+	if (name != NULL) {
+		isc__cfgmgr_buildkey(name, false);
+	}
+	dbkey = (MDB_val){
+		.mv_size = name == NULL ? 0
+					: strlen(isc__cfgmgr_ctx.buffer) + 1,
+		.mv_data = name == NULL ? NULL : isc__cfgmgr_ctx.buffer
+	};
+	if (mdb_cursor_get(isc__cfgmgr_ctx.cursor, &dbkey, &dbval, opt) != 0) {
+		result = opt == MDB_NEXT_DUP ? ISC_R_NOMORE : ISC_R_NOTFOUND;
+		goto out;
+	}
+
+	memcpy(value, dbval.mv_data, sizeof(*value));
+	if (value->type == ISC_CFGMGR_STRING) {
+		value->string = ((char *)dbval.mv_data) + sizeof(value->type);
+	}
+	INSIST(value->type != ISC_CFGMGR_UNDEFINED);
+
+out:
+	return result;
+}
+
+isc_result_t
+isc_cfgmgr_getval(const char *name, isc_cfgmgr_val_t *value) {
+	return isc__cfgmgr_getval(name, value);
+}
+
+isc_result_t
+isc_cfgmgr_getnextlistval(isc_cfgmgr_val_t *value) {
+	return isc__cfgmgr_getval(NULL, value);
+}
+
+static isc_result_t
+isc__cfgmgr_setval(const char *name, const isc_cfgmgr_val_t *value, bool list) {
+	isc_result_t result = ISC_R_SUCCESS;
+	MDB_val dbkey;
+	MDB_val dbval;
+
+	REQUIRE(isc__cfgmgr_env != NULL);
+	REQUIRE(ISC_LIST_EMPTY(isc__cfgmgr_ctx.openedclauses) == false);
+	REQUIRE(isc__cfgmgr_ctx.prefix != NULL);
+	REQUIRE(isc__cfgmgr_ctx.buffer != NULL);
+	REQUIRE(isc__cfgmgr_ctx.txn != NULL);
+	REQUIRE(isc__cfgmgr_ctx.cursor != NULL);
+	REQUIRE(isc__cfgmgr_ctx.readonly == false);
+	REQUIRE(name != NULL);
+	REQUIRE((value != NULL && value->type != ISC_CFGMGR_UNDEFINED) ||
+		(value == NULL && list == false));
+
+	isc__cfgmgr_buildkey(name, false);
+	dbkey = (MDB_val){ .mv_size = strlen(isc__cfgmgr_ctx.buffer) + 1,
+			   .mv_data = isc__cfgmgr_ctx.buffer };
+	if (value == NULL) {
+		if (mdb_cursor_get(isc__cfgmgr_ctx.cursor, &dbkey, NULL,
+				   MDB_SET) == MDB_NOTFOUND)
+		{
+			result = ISC_R_NOTFOUND;
+			goto out;
+		}
+
+		REQUIRE(mdb_cursor_del(isc__cfgmgr_ctx.cursor, MDB_NODUPDATA) ==
+			0);
+		goto out;
+	}
+
+	if (value->type == ISC_CFGMGR_STRING) {
+		dbval.mv_size = sizeof(*value) + strlen(value->string) + 1;
+		dbval.mv_data = isc_mem_allocate(isc__cfgmgr_mctx,
+						 dbval.mv_size);
+		memcpy(dbval.mv_data, value, sizeof(value->type));
+		strcpy(((char *)dbval.mv_data) + sizeof(value->type),
+		       value->string);
+	} else {
+		dbval = (MDB_val){ .mv_size = sizeof(*value),
+				   /*
+				    * LMDB won't modify the mv_data buffer but
+				    * its API is designed w/o the const buffer.
+				    */
+				   .mv_data = (void *)value };
+	}
+
+	if (list == false) {
+		/*
+		 * Can't use MDB_NOOVERWRITE as it would override the
+		 * data if the key/value already exists. Making a
+		 * value copy ahead just in case is likely more
+		 * expensive than an extra lookup
+		 */
+		if (mdb_cursor_get(isc__cfgmgr_ctx.cursor, &dbkey, NULL,
+				   MDB_SET) != MDB_NOTFOUND)
+		{
+			REQUIRE(mdb_cursor_del(isc__cfgmgr_ctx.cursor, 0) == 0);
+		}
+	}
+
+	REQUIRE(mdb_cursor_put(isc__cfgmgr_ctx.cursor, &dbkey, &dbval, 0) == 0);
+
+	if (value->type == ISC_CFGMGR_STRING) {
+		isc_mem_free(isc__cfgmgr_mctx, dbval.mv_data);
+	}
+
+out:
+	return result;
+}
+
+isc_result_t
+isc_cfgmgr_setval(const char *name, const isc_cfgmgr_val_t *value) {
+	return isc__cfgmgr_setval(name, value, false);
+}
+
+isc_result_t
+isc_cfgmgr_setnextlistval(const char *name, const isc_cfgmgr_val_t *value) {
+	return isc__cfgmgr_setval(name, value, true);
+}

lib/isc/include/isc/cfgmgr.h

@@ -0,0 +1,181 @@
+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, you can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+#pragma once
+
+#include <isc/sockaddr.h>
+#include <isc/types.h>
+
+/*
+ * Supported data types for read/write operations from/to cfgmgr.
+ */
+typedef enum isc_cfgmgr_type {
+	ISC_CFGMGR_UNDEFINED = 0,
+	ISC_CFGMGR_STRING,
+	ISC_CFGMGR_BOOLEAN,
+	ISC_CFGMGR_NONE,
+	ISC_CFGMGR_SOCKADDR,
+	ISC_CFGMGR_UINT32
+} isc_cfgmgr_type_t;
+
+/*
+ * Generic value holding the actual value and type value for
+ * read/write from/to cfgmgr.
+ *
+ * cfgmgr_type_t::NONE doesn't have associated value,
+ */
+typedef struct isc_cfgmgr_val {
+	isc_cfgmgr_type_t type;
+	union {
+		const char    *string;
+		bool	       boolean;
+		isc_sockaddr_t sockaddr;
+		uint32_t       uint32;
+	};
+} isc_cfgmgr_val_t;
+
+/*
+ * Get the property "name" in the opened clause into the caller
+ * allocated "value" and returns ISC_R_SUCCESS. Returns ISC_R_NOTFOUND
+ * and "*value" is not mutated if "name" is not found. Changes being
+ * made by other threads aren't visible until the clause (and its
+ * parent, if nested) is closed. If "name" is a list property, get its
+ * head.
+ */
+isc_result_t
+isc_cfgmgr_getval(const char *name, isc_cfgmgr_val_t *value);
+
+/*
+ * Write "value" into the property "name" in the opened clause and
+ * returns ISC_R_SUCCESS. If the property already exists, it is
+ * overridden and even if the type is different. If "value" is NULL
+ * and the property exists, it will be deleted (applies for list
+ * properties as well), otherwise, it returns ISC_R_NOTFOUND. Changes
+ * being made can be visible only by the current thread until the
+ * clause (and its parent, if nested) is closed.
+ */
+isc_result_t
+isc_cfgmgr_setval(const char *name, const isc_cfgmgr_val_t *value);
+
+/*
+ * Same as isc_cfgmgr_getval but applies for elements after the head
+ * of a list property. The head is read using isc_cfgmgr_getval as any
+ * other value, then subsequents calls to isc_cfgmgr_getnextlistval
+ * will get the next elements in the list. When the end of the list is
+ * reached, ISC_R_NOMORE is returned. Calls to
+ * isc_cfgmgr_getnextlistval name has to be made in immediate sequence
+ * (without intermediate isc_cfgmgr_{set,get}val calls) to retrieve
+ * each list element.
+ */
+isc_result_t
+isc_cfgmgr_getnextlistval(isc_cfgmgr_val_t *value);
+
+/*
+ * Same as isc_cfgmgr_setval but applies for a list property. Writes
+ * by appending "*value" at the end of the list property "name" in the
+ * opened clause and returns ISC_R_SUCCESS. If "name" property wasn't
+ * existing before (or wasn't a list) it's overriden. It is not
+ * possible to delete individual list element, only the whole list can
+ * be removed using isc_cfgmgr_setval.
+ */
+isc_result_t
+isc_cfgmgr_setnextlistval(const char *name, const isc_cfgmgr_val_t *value);
+
+/*
+ * If the opened clause is a repeatable clause (i.e. view, acl, etc.),
+ * internally closes the opened clause and open the next clause of the
+ * same type and returns ISC_R_SUCCESS. When there is no next clause
+ * of the same type, ISC_R_NOMORE is returned.
+ */
+isc_result_t
+isc_cfgmgr_nextclause(void);
+
+/*
+ * If used at top-level, create and open as read-write a new clause
+ * "name". If used inside an opened parent clause, then the parent (or
+ * parent or the parent, recursively) clause must have been opened
+ * read-write (so using isc_cfgmgr_openrw or isc_cfgmgr_newclause).
+ *
+ * Returns ISC_R_SUCCESS or ISC_R_FAILURE if there is no transaction
+ * and it fails creating one. Note that in order to have the new
+ * clause actually written in cfgmgr, at least one property needs to
+ * be set to that clause.
+ */
+isc_result_t
+isc_cfgmgr_newclause(const char *name);
+
+/*
+ * Delete and close the opened clause. (And thus all its properties,
+ * including nested clauses). If the clause was nested, the currently
+ * opened clause is now the parent clause. Otherwise, no clause is
+ * opened. Returns ISC_R_SUCCESS.
+ */
+isc_result_t
+isc_cfgmgr_delclause(void);
+
+/*
+ * Close the currently opened clause and returns ISC_R_SUCCESS. If the
+ * closed clause was nested, the currently opened clause is now the
+ * parent clause. If top-level clause was opened with
+ * isc_cfgmgr_openrw or isc_cfgmgr_newclause, closing the top-level
+ * clause will applies all modifications done inside the clause (and
+ * inside the nested clauses). If something is going wrong while
+ * writing the modifications ISC_R_FAILURE is returned and all
+ * modification made are discarded.
+ */
+isc_result_t
+isc_cfgmgr_close(void);
+
+/*
+ * Open the top-level clause "name" for reading and writing and
+ * returns ISC_R_SUCCESS. If the clause "name" is not found, returns
+ * ISC_R_NOTFOUND. If there is an issue creating a transaction, it
+ * returns ISC_R_FAILURE.
+ *
+ * This call will block if another thread has already a clause opened
+ * for reading and writting. Use isc_cfgmgr_openro for reading only.
+ */
+isc_result_t
+isc_cfgmgr_openrw(const char *name);
+
+/*
+ * Open the clause "name" and returns ISC_R_SUCCES or ISC_R_NOTFOUND
+ * is the clause is not found. Two possible cases:
+ *
+ * - if called at top-level, it open the top-level clause as read
+ *   only. Returns ISC_R_FAILURE if there is an issue creating the
+ *   transaction.
+ *
+ * - if called form within an opened clause, it open it with the same
+ *   access than the already opened clause.
+ */
+isc_result_t
+isc_cfgmgr_open(const char *name);
+
+/*
+ * Initialize cfgmgr. Must be called before any other function. It is
+ * possible to re-initialize cfgmgr only after calling
+ * isc_cfgmgr_deinit (this drops all the data written in
+ * cfgmgr). Returns ISC_R_SUCCESS or ISC_R_FAILURE if there is an
+ * issue initializing the internal database.
+ */
+isc_result_t
+isc_cfgmgr_init(isc_mem_t *mctx, const char *dbpath);
+
+/*
+ * Destroy all cfgmgr data and free memory. Must be called only after
+ * isc_cfgmgr_init and no function must be called after that one
+ * (except isc_cfgmgr_init to re-initialize cfgmgr again).
+ */
+void
+isc_cfgmgr_deinit(void);

lib/isc/include/isc/lmdb.h

@@ -0,0 +1,27 @@
+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, you can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+#pragma once
+
+#include <lmdb.h>
+
+#define DNS_LMDB_COMMON_FLAGS (MDB_NOSUBDIR | MDB_NOLOCK)
+#ifndef __OpenBSD__
+#define DNS_LMDB_FLAGS (DNS_LMDB_COMMON_FLAGS)
+#else /* __OpenBSD__ */
+/*
+ * OpenBSD does not have a unified buffer cache, which requires both reads and
+ * writes to be performed using mmap().
+ */
+#define DNS_LMDB_FLAGS (DNS_LMDB_COMMON_FLAGS | MDB_WRITEMAP)
+#endif /* __OpenBSD__ */

lib/isccfg/namedconf.c

@@ -2061,11 +2061,7 @@ static cfg_clausedef_t view_clauses[] = {
 	{ "ipv4only-server", &cfg_type_astring, 0 },
 	{ "ixfr-from-differences", &cfg_type_ixfrdifftype, 0 },
 	{ "lame-ttl", &cfg_type_duration, 0 },
-#ifdef HAVE_LMDB
-	{ "lmdb-mapsize", &cfg_type_sizeval, CFG_CLAUSEFLAG_OPTIONAL },
-#else  /* ifdef HAVE_LMDB */
-	{ "lmdb-mapsize", &cfg_type_sizeval, CFG_CLAUSEFLAG_NOTCONFIGURED },
-#endif /* ifdef HAVE_LMDB */
+	{ "lmdb-mapsize", &cfg_type_sizeval, 0 },
 	{ "max-acache-size", NULL, CFG_CLAUSEFLAG_ANCIENT },
 	{ "max-cache-size", &cfg_type_sizeorpercent, 0 },
 	{ "max-cache-ttl", &cfg_type_duration, 0 },

tests/isc/Makefile.am

@@ -15,6 +15,7 @@ check_PROGRAMS =	\
 	ascii_test	\
 	async_test	\
 	buffer_test	\
+	cfgmgr_test	\
 	counter_test	\
 	dnsstream_utils_test \
 	errno_test	\