Merge branch '1862-insist-in-query-c' into 'main'

Fix assertion failure when server is under load and root zone is not yet loaded.

Closes #1862

See merge request isc-projects/bind9!3572

CHANGES

@@ -1,3 +1,6 @@
+5454.	[bug]		Address a startup crash happening when server is
+			under load and root zone is not yet loaded. [GL #1862]
+
 5453.	[bug]		`named` would crash on shutdown when new `rndc`
 			connection is received at the same time as
 			shutting down. [GL #1747]

doc/notes/notes-current.rst

@@ -65,3 +65,6 @@ Bug Fixes
 
 - ``named`` would crash on shutdown when new ``rndc`` connection is received at
   the same time as shutting down. [GL #1747]
+
+- Fix assertion failure when server is under load and root zone is not yet
+  loaded. [GL #1862]

lib/dns/resolver.c

@@ -4397,6 +4397,15 @@ resume_qmin(isc_task_t *task, isc_event_t *event) {
 				      fctx->now, findoptions, true, true,
 				      &fctx->nameservers, NULL);
 
+	/*
+	 * DNS_R_NXDOMAIN here means we have not loaded the root zone mirror
+	 * yet - but DNS_R_NXDOMAIN is not a valid return value when doing
+	 * recursion, we need to patch it.
+	 */
+	if (result == DNS_R_NXDOMAIN) {
+		result = DNS_R_SERVFAIL;
+	}
+
 	if (result != ISC_R_SUCCESS) {
 		fctx_done(fctx, result, __LINE__);
 		goto cleanup;