From 96a587bba9afec5efa0ea0685d29bcf6ee4a44b8 Mon Sep 17 00:00:00 2001
From: Mike Degatano <michael.degatano@gmail.com>
Date: Fri, 4 Mar 2022 04:22:17 -0500
Subject: [PATCH] Return noerror if any answers found (A or AAAA) (#81)

---
 plugins/mdns/mdns.go      | 10 ++++++----
 plugins/mdns/mdns_test.go |  2 ++
 plugins/mdns/setup.go     |  4 ++--
 3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/plugins/mdns/mdns.go b/plugins/mdns/mdns.go
index c4d28bc..f05e36b 100644
--- a/plugins/mdns/mdns.go
+++ b/plugins/mdns/mdns.go
@@ -34,8 +34,12 @@ func (m MDNS) AddARecord(msg *dns.Msg, state *request.Request, name string, addr
 	// Add A and AAAA record for name (if it exists) to msg.
 	// A records need to be returned in A queries, this function
 	// provides common code for doing so.
+	// Success is always returned if any answers found, even if they don't match question type
+	// A noerror on A and nxdomain on AAAA (or vice versa) breaks some clients (musl)
+	if len(addresses) == 0 {
+		return false
+	}
 
-	resolved := false
 	ifc_index := 0
 	for i := 0; i < len(addresses); i++ {
 		addr := addresses[i]
@@ -55,15 +59,13 @@ func (m MDNS) AddARecord(msg *dns.Msg, state *request.Request, name string, addr
 			} else {
 				msg.Answer = append(msg.Answer, &dns.A{Hdr: aheader, A: ip})
 			}
-			resolved = true
 
 		} else if addr.V1 == syscall.AF_INET6 && state.QType() == dns.TypeAAAA {
 			aaaaheader := dns.RR_Header{Name: name, Rrtype: dns.TypeAAAA, Class: dns.ClassINET, Ttl: 60}
 			msg.Answer = append(msg.Answer, &dns.AAAA{Hdr: aaaaheader, AAAA: ip})
-			resolved = true
 		}
 	}
-	return resolved
+	return true
 }
 
 func (m MDNS) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
diff --git a/plugins/mdns/mdns_test.go b/plugins/mdns/mdns_test.go
index 4d95399..1fa89b6 100644
--- a/plugins/mdns/mdns_test.go
+++ b/plugins/mdns/mdns_test.go
@@ -91,6 +91,8 @@ func TestAddARecord(t *testing.T) {
 			"myservice.local	60	IN	A	192.168.1.1",
 			"myservice.local	60	IN	A	10.1.1.1",
 		}, true},
+		{"success on AAAA if only A found", "mymachine.local", dns.TypeAAAA, nilResponseWriter{}, 1, ipv4, []string{}, true},
+		{"success on A if only AAAA found", "mymachine.local", dns.TypeA, nilResponseWriter{}, 1, ipv6, []string{}, true},
 	}
 	for _, tc := range testCases {
 		m := MDNS{nil, nil, tc.ifc}
diff --git a/plugins/mdns/setup.go b/plugins/mdns/setup.go
index d407027..ca260fc 100644
--- a/plugins/mdns/setup.go
+++ b/plugins/mdns/setup.go
@@ -21,12 +21,12 @@ func setup(c *caddy.Controller) error {
 	var m MDNS
 	conn, err := dbus.ConnectSystemBus()
 	if err != nil {
-		log.Error("could not connect to systemd resolver due to %s", err)
+		log.Error("could not connect to systemd resolver due to: ", err)
 		log.Error("mdns and llmnr urls will not resolve in without this")
 
 		m = MDNS{
 			Resolver: nil,
-			Ifc: 0,
+			Ifc:      0,
 		}
 	} else {
 		bus_object := conn.Object("org.freedesktop.resolve1", "/org/freedesktop/resolve1")