nameserver.go: refactor requiresRRUpdate and add basic tests

go.mod

@@ -3,6 +3,7 @@ module git.preisner.eu/preisi/dyndns-server
 go 1.16
 
 require (
+	github.com/foxcpp/go-mockdns v0.0.0-20210729171921-fb145fc6f897
 	github.com/google/go-cmp v0.5.6
 	github.com/pelletier/go-toml v1.9.3
 	golang.org/x/crypto v0.0.0-20210711020723-a769d52b0f97

go.sum

@@ -1,14 +1,34 @@
+github.com/foxcpp/go-mockdns v0.0.0-20210729171921-fb145fc6f897 h1:E52jfcE64UG42SwLmrW0QByONfGynWuzBvm86BoB9z8=
+github.com/foxcpp/go-mockdns v0.0.0-20210729171921-fb145fc6f897/go.mod h1:lgRN6+KxQBawyIghpnl5CezHFGS9VLzvtVlwxvzXTQ4=
 github.com/google/go-cmp v0.5.6 h1:BKbKCqvP6I+rmFHt06ZmyQtvB8xAkWdhFyr0ZUNZcxQ=
 github.com/google/go-cmp v0.5.6/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/miekg/dns v1.1.25 h1:dFwPR6SfLtrSwgDcIq2bcU/gVutB4sNApq2HBdqcakg=
+github.com/miekg/dns v1.1.25/go.mod h1:bPDLeHnStXmXAq1m/Ch/hvfNHr14JKNPMBo3VZKjuso=
 github.com/pelletier/go-toml v1.9.3 h1:zeC5b1GviRUyKYd6OJPvBU/mcVDVoL1OhT17FCt5dSQ=
 github.com/pelletier/go-toml v1.9.3/go.mod h1:u1nR/EPcESfeI/szUZKdtJ0xRNbUoANCkoOuaOx1Y+c=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20190923035154-9ee001bba392/go.mod h1:/lpIB1dKB+9EgE3H3cr1v9wB50oz8l4C4h62xy7jSTY=
 golang.org/x/crypto v0.0.0-20210711020723-a769d52b0f97 h1:/UOmuWzQfxxo9UtlXMwuQU8CMgg1eZXqTRwkSQJWKOI=
 golang.org/x/crypto v0.0.0-20210711020723-a769d52b0f97/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20190923162816-aa69164e4478/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20210226172049-e18ecbb05110 h1:qWPm9rbaAMKs8Bq/9LRpbMqxWRVUAQwMI9fVrssnTfw=
 golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58 h1:8gQV6CLnAEikrhgkHFbMAEhagSSnXWGV915qUMm9mrU=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190922100055-0a153f010e69/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20190924154521-2837fb4f24fe/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1 h1:SrN+KX8Art/Sf4HNj6Zcz06G7VEz+7w9tdXTPOZ7+l4=
 golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
+golang.org/x/tools v0.0.0-20190907020128-2ca718005c18/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

nameserver.go

@@ -28,10 +28,19 @@ func getResolver(nameserver string) *net.Resolver {
 	}
 }
 
-func requiresRRUpdate(record string, addr net.IP, resolver *net.Resolver) bool {
+// FIXME: mockdns.Resolver from foxccp/go-mockdns, which is used for testing,
+// does not implement the complete net.Resolver interface. Thus, we need to
+// define a more minimalistic resolver interface compatible with both
+// net.Resolver and mockdns.Resolver to avoid compiler errors.
+// Maybe there is a better way to circumvent this though.
+type localResolver interface {
+	LookupHost(context.Context, string) ([]string, error)
+}
+
+func requiresRRUpdate(record string, addr net.IP, resolver localResolver) bool {
 	// TODO: the context could be replaced in order to allow cancelling the dns
 	// query if the user disconnects prematurely
-	addrs, err := resolver.LookupIP(context.Background(), "ip", record)
+	addrs, err := resolver.LookupHost(context.Background(), record)
 	if err != nil {
 		log.Printf("dns lookup failed: %s", err)
 		// enforce update, it's better than not trying at all
@@ -40,7 +49,7 @@ func requiresRRUpdate(record string, addr net.IP, resolver *net.Resolver) bool {
 
 	// check if the current ip matches
 	for _, ip := range addrs {
-		if ip.Equal(addr) {
+		if addr.Equal(net.ParseIP(ip)) {
 			// the ip seems to be still up-to-date -> no update required
 			return false
 		}

nameserver_test.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"net"
+	"testing"
+
+	"github.com/foxcpp/go-mockdns"
+)
+
+func TestRequiresRRUpdate(t *testing.T) {
+	tests := []struct {
+		name   string
+		record string
+		addr   net.IP
+		expRes bool
+	}{
+		{
+			"nonexistent record",
+			"invalid.example.org",
+			net.ParseIP("1.1.1.1"),
+			true,
+		},
+		{
+			"ipv4 update required",
+			"ipv4.example.org",
+			net.ParseIP("1.1.1.1"),
+			true,
+		},
+		{
+			"ipv4 up to date",
+			"ipv4.example.org",
+			net.ParseIP("2.2.2.2"),
+			false,
+		},
+		{
+			"ipv6 up to date",
+			"ipv6.example.org",
+			net.ParseIP("1:1:1:1:1:1:1:1"),
+			true,
+		},
+		{
+			"ipv6 up to date",
+			"ipv6.example.org",
+			net.ParseIP("2:2:2:2:2:2:2:2"),
+			false,
+		},
+	}
+
+	// setup mock resolver
+	resolver := mockdns.Resolver{
+		Zones: map[string]mockdns.Zone{
+			"ipv4.example.org.": {
+				A: []string{"2.2.2.2"},
+			},
+			"ipv6.example.org.": {
+				AAAA: []string{"2:2:2:2:2:2:2:2"},
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		res := requiresRRUpdate(tc.record, tc.addr, &resolver)
+
+		if tc.expRes != res {
+			t.Errorf("%s: has=%v, wanted=%v", tc.name, res, tc.expRes)
+		}
+	}
+}