From: Vladimír Čunát <vladimir.cunat@nic.cz>
Date: Tue, 7 Jul 2026 13:00:52 +0000 (+0200)
Subject: lib/cache/cdb: deal with LMDB 1.0.0 switching format
X-Git-Tag: v5.7.8~2^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7362e1c3;p=thirdparty%2Fknot-resolver.git

lib/cache/cdb: deal with LMDB 1.0.0 switching format

1.0.0 also regresses in properties of mdb_drop()
(which will be fixed in 1.0.1 reportedly),
but with kresd 5.x this doesn't seem to cause issues.
---

diff --git a/NEWS b/NEWS
index 70313a13b..9acfc0a80 100644
--- a/NEWS
+++ b/NEWS
@@ -5,6 +5,10 @@ Bugfixes
 --------
 - cache: avoid excessive logging introduced in the last release (!1871)
 
+Improvements
+------------
+- cache: deal with LMDB 1.0.0 switching format (!1872)
+
 
 Knot Resolver 5.7.7 (2026-07-22)
 ================================
diff --git a/lib/cache/cdb_lmdb.c b/lib/cache/cdb_lmdb.c
index 80c73729e..f2c87253a 100644
--- a/lib/cache/cdb_lmdb.c
+++ b/lib/cache/cdb_lmdb.c
@@ -425,6 +425,17 @@ static int cdb_init(kr_cdb_pt *db, struct kr_cdb_stats *stats,
 		return kr_error(ENOMEM);
 	}
 	int ret = cdb_open_env(env, opts->path, opts->maxsize, stats);
+	/* Uh, LMDB 1.0 is incompatible with LMDB 0.y.  Hack-retry. */
+	if (abs(ret) == abs(MDB_INVALID)) {
+		kr_log_error(CACHE, "found incompatible data after LMDB version change, probably; "
+	       			"clearing and retrying\n");
+		auto_free char *mdb_datafile = kr_strcatdup(2, opts->path, "/data.mdb");
+		auto_free char *mdb_lockfile = kr_strcatdup(2, opts->path, "/lock.mdb");
+		unlink(mdb_datafile); /* we ignore errors; e.g. either might not exist */
+		unlink(mdb_lockfile);
+
+		ret = cdb_open_env(env, opts->path, opts->maxsize, stats);
+	}
 	if (ret != 0) {
 		free(env);
 		return ret;