From 1292e1a557077b710c9daba33b79da66e4d89de6 Mon Sep 17 00:00:00 2001
From: Simon Kelley <simon@thekelleys.org.uk>
Date: Fri, 25 Oct 2019 17:31:53 +0100
Subject: [PATCH] Don't waste time caching zero-TTL DNS records.

---
 src/cache.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/cache.c b/src/cache.c
index b3ed50b..733e053 100644
--- a/src/cache.c
+++ b/src/cache.c
@@ -499,6 +499,13 @@ static struct crec *really_insert(char *name, union all_addr *addr, unsigned sho
   /* if previous insertion failed give up now. */
   if (insert_error)
     return NULL;
+
+  /* we don't cache zero-TTL records. */
+  if (ttl == 0)
+    {
+      insert_error = 1;
+      return NULL;
+    }
   
   /* First remove any expired entries and entries for the name/address we
      are currently inserting. */