From: Colin Vidal <colin@isc.org>
Date: Mon, 19 Jan 2026 14:52:30 +0000 (+0100)
Subject: resolver: add comment when recursing
X-Git-Tag: v9.21.18~20^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bc1a66a1d0cef854120189ea8542a4b01f556738;p=thirdparty%2Fbind9.git

resolver: add comment when recursing

When a fetch result gets a delegation, `rctx_referral()` sets the
`rctx->get_nameserver = true`, which tells the resolver to retry another
server, not because of an error with the current server, but simply to
follow the delegation.

Update the comment of `rctx_nextserver()` which is quite confusing here
(as it's not immediately obvious from the code how we recurse when
getting a delegation back from a query).

Also add a log line, which helps figuring out this is happening.
---

diff --git a/lib/dns/resolver.c b/lib/dns/resolver.c
index e68686b4ebf..919e518ac96 100644
--- a/lib/dns/resolver.c
+++ b/lib/dns/resolver.c
@@ -9179,6 +9179,9 @@ again:
  * rctx_nextserver():
  * We found something wrong with the remote server, but it may be
  * useful to try another one.
+ * Or nothing is wrong, but the server returned a referral
+ * (rctx->get_nameservers has been set by rctx_referral()) so we need to try
+ * again with a new zonecut.
  */
 static void
 rctx_nextserver(respctx_t *rctx, dns_message_t *message,
@@ -9398,6 +9401,7 @@ rctx_done(respctx_t *rctx, isc_result_t result) {
 
 	if (rctx->next_server) {
 		UNLOCK(&fctx->lock);
+		FCTXTRACE("nextserver");
 		rctx_nextserver(rctx, message, addrinfo, result);
 	} else if (rctx->resend) {
 		UNLOCK(&fctx->lock);