avoid returning stale ServFail response

Close AdguardTeam#436. Signed-off-by: Jay <BusyJay@users.noreply.github.com>
BusyJay · Feb 12, 2025 · 8fb6266 · 8fb6266
1 parent 1177916
commit 8fb6266
Showing 1 changed file with 6 additions and 0 deletions.
diff --git a/proxy/cache.go b/proxy/cache.go
@@ -141,6 +141,12 @@ func (c *cache) unpackItem(data []byte, req *dns.Msg) (ci *cacheItem, expired bo
 		return nil, expired
 	}
 
+	// Don't return expired ServFail response from cache, otherwise it may stop
+	// future refresh.
+	if m.Rcode == dns.RcodeServerFailure && expired {
+		return nil, expired
+	}
+
 	res := (&dns.Msg{}).SetRcode(req, m.Rcode)
 	res.AuthenticatedData = m.AuthenticatedData
 	res.RecursionAvailable = m.RecursionAvailable