lib/protocol, lib/discover, lib/db: Use protocol buffer serialization (fixes #3080)

This changes the BEP protocol to use protocol buffer serialization
instead of XDR, and therefore also the database format. The local
discovery protocol is also updated to be protocol buffer format.

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3276
LGTM: AudriusButkevicius

lib/protocol/hello_test.go

@@ -13,6 +13,53 @@ import (
 
 var spaceRe = regexp.MustCompile(`\s`)
 
+func TestVersion14Hello(t *testing.T) {
+	// Tests that we can send and receive a version 0.14 hello message.
+
+	expected := Hello{
+		DeviceName:    "test device",
+		ClientName:    "syncthing",
+		ClientVersion: "v0.14.5",
+	}
+	msgBuf, err := expected.Marshal()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	hdrBuf := make([]byte, 8)
+	binary.BigEndian.PutUint32(hdrBuf, HelloMessageMagic)
+	binary.BigEndian.PutUint32(hdrBuf[4:], uint32(len(msgBuf)))
+
+	outBuf := new(bytes.Buffer)
+	outBuf.Write(hdrBuf)
+	outBuf.Write(msgBuf)
+
+	inBuf := new(bytes.Buffer)
+
+	conn := &readWriter{outBuf, inBuf}
+
+	send := &Hello{
+		DeviceName:    "this device",
+		ClientName:    "other client",
+		ClientVersion: "v0.14.6",
+	}
+
+	res, err := ExchangeHello(conn, send)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if res.ClientName != expected.ClientName {
+		t.Errorf("incorrect ClientName %q != expected %q", res.ClientName, expected.ClientName)
+	}
+	if res.ClientVersion != expected.ClientVersion {
+		t.Errorf("incorrect ClientVersion %q != expected %q", res.ClientVersion, expected.ClientVersion)
+	}
+	if res.DeviceName != expected.DeviceName {
+		t.Errorf("incorrect DeviceName %q != expected %q", res.DeviceName, expected.DeviceName)
+	}
+}
+
 func TestVersion13Hello(t *testing.T) {
 	// Tests that we can send and receive a version 0.13 hello message.
 
@@ -42,8 +89,8 @@ func TestVersion13Hello(t *testing.T) {
 	}
 
 	res, err := ExchangeHello(conn, send)
-	if err != nil {
-		t.Fatal(err)
+	if err != ErrTooOldVersion13 {
+		t.Errorf("unexpected error %v != ErrTooOldVersion13", err)
 	}
 
 	if res.ClientName != expected.ClientName {
@@ -94,7 +141,7 @@ func TestVersion12Hello(t *testing.T) {
 
 	_, err := ExchangeHello(conn, send)
 	if err != ErrTooOldVersion12 {
-		t.Errorf("unexpected error %v != ErrTooOld", err)
+		t.Errorf("unexpected error %v != ErrTooOldVersion12", err)
 	}
 }