From 7b69dfebb595fe08bc1fcf52234880da79d4e1aa Mon Sep 17 00:00:00 2001
From: Uladzimir Trehubenka <utrehubenka@infoblox.com>
Date: Tue, 1 Oct 2019 15:22:42 +0300
Subject: [PATCH] plugin/file: fix panic in miekg/dns.CompareDomainName()
 (#3337)

Signed-off-by: utrehubenka <utrehubenka@infoblox.com>
---
 plugin/file/lookup.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/plugin/file/lookup.go b/plugin/file/lookup.go
index 15ea096bb..3d8d899df 100644
--- a/plugin/file/lookup.go
+++ b/plugin/file/lookup.go
@@ -372,7 +372,7 @@ func (z *Zone) additionalProcessing(answer []dns.RR, do bool) (extra []dns.RR) {
 		case *dns.MX:
 			name = x.Mx
 		}
-		if !dns.IsSubDomain(z.origin, name) {
+		if len(name) == 0 || !dns.IsSubDomain(z.origin, name) {
 			continue
 		}