From ca8d04a8ff951896578c1f1026a014955a0b40a7 Mon Sep 17 00:00:00 2001
From: Simon Kelley <simon@thekelleys.org.uk>
Date: Mon, 9 Oct 2023 21:15:13 +0100
Subject: [PATCH] Cache zero-TTL DNS replies when stale-caching is enabled.

---
 src/cache.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/cache.c b/src/cache.c
index 1c0e250..9f64a05 100644
--- a/src/cache.c
+++ b/src/cache.c
@@ -629,8 +629,8 @@ static struct crec *really_insert(char *name, union all_addr *addr, unsigned sho
   if (insert_error)
     return NULL;
 
-  /* we don't cache zero-TTL records. */
-  if (ttl == 0)
+  /* we don't cache zero-TTL records unless we're doing stale-caching. */
+  if (daemon->cache_max_expiry == 0 && ttl == 0)
     {
       insert_error = 1;
       return NULL;