resolved: lower SERVFAIL cache timeout from 30s to 10s

Apparently 30s is a bit too long for some cases, see #5552. But not
caching SERVFAIL at all also breaks stuff, see explanation in
201d99584ed7af8078bb243ce2587e5455074713.

Let's try to find some middle ground, by lowering the cache timeout to
10s. This should be ample for the problem
201d99584ed7af8078bb243ce2587e5455074713 attackes, but not as long as
half a miute, as #5552 complains.

Fixes: #5552
(cherry picked from commit 19bcef9dc3fde342f138394333ab04d7e44b7da2)

diff --git a/src/resolve/resolved-dns-cache.c b/src/resolve/resolved-dns-cache.c
index 946889a83444f053943a88782f713e1f93ffebb3..99cee25a2d275606ecd1c9d9541cacffe016945f 100644 (file)
--- a/src/resolve/resolved-dns-cache.c
+++ b/src/resolve/resolved-dns-cache.c
@@ -20,7 +20,7 @@
 
 /* How long to cache strange rcodes, i.e. rcodes != SUCCESS and != NXDOMAIN (specifically: that's only SERVFAIL for
  * now) */
-#define CACHE_TTL_STRANGE_RCODE_USEC (30 * USEC_PER_SEC)
+#define CACHE_TTL_STRANGE_RCODE_USEC (10 * USEC_PER_SEC)
 
 typedef enum DnsCacheItemType DnsCacheItemType;
 typedef struct DnsCacheItem DnsCacheItem;