From a255190005ad6f44a48b3523023415b19aa78a1d Mon Sep 17 00:00:00 2001
From: Knut Ahlers <knut@ahlers.me>
Date: Tue, 30 Jan 2018 17:01:13 +0100
Subject: [PATCH] Force record TTL on alias records

Signed-off-by: Knut Ahlers <knut@ahlers.me>
---
 alias.go | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/alias.go b/alias.go
index f1a9997..3b8db63 100644
--- a/alias.go
+++ b/alias.go
@@ -45,10 +45,14 @@ func (r *ResponseModifier) WriteMsg(res *dns.Msg) error {
 	}
 
 	// Find and delete CNAME record on that zone, storing the canonical name.
-	var cname string
+	var (
+		cname string
+		ttl   uint32
+	)
 	for i, rr := range res.Answer {
 		if rr.Header().Rrtype == dns.TypeCNAME && rr.Header().Name == zone {
 			cname = rr.(*dns.CNAME).Target
+			ttl = rr.(*dns.CNAME).Header().Ttl
 			// Remove the CNAME record
 			res.Answer = append(res.Answer[:i], res.Answer[i+1:]...)
 			break
@@ -59,6 +63,7 @@ func (r *ResponseModifier) WriteMsg(res *dns.Msg) error {
 	for _, rr := range res.Answer {
 		if rr.Header().Name == cname {
 			rr.Header().Name = zone
+			rr.Header().Ttl = ttl
 		}
 	}