Parse ClientPollRequest version in DecodeClientPollRequest

Instead of IPC.ClientOffers.  This makes things consistent with
EncodeClientPollRequest which adds the version while serializing.

common/messages/client.go

@@ -4,13 +4,14 @@
 package messages
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
 
 	"git.torproject.org/pluggable-transports/snowflake.git/v2/common/nat"
 )
 
-const ClientVersion = "1.0"
+const ClientVersion1_0 = "1.0"
 
 /* Client--Broker protocol v1.x specification:
 
@@ -49,24 +50,41 @@ for the error.
 */
 
 type ClientPollRequest struct {
-	Offer string `json:"offer"`
-	NAT   string `json:"nat"`
+	Offer   string `json:"offer"`
+	NAT     string `json:"nat"`
+	Version string `json:"-"`
 }
 
 // Encodes a poll message from a snowflake client
 func (req *ClientPollRequest) EncodeClientPollRequest() ([]byte, error) {
+	if req.Version != ClientVersion1_0 {
+		return nil, fmt.Errorf("unsupported message version")
+	}
 	body, err := json.Marshal(req)
 	if err != nil {
 		return nil, err
 	}
-	return append([]byte(ClientVersion+"\n"), body...), nil
+	return append([]byte(req.Version+"\n"), body...), nil
 }
 
 // Decodes a poll message from a snowflake client
 func DecodeClientPollRequest(data []byte) (*ClientPollRequest, error) {
+	parts := bytes.SplitN(data, []byte("\n"), 2)
+
+	if len(parts) < 2 {
+		// no version number found
+		return nil, fmt.Errorf("unsupported message version")
+	}
+
 	var message ClientPollRequest
 
-	err := json.Unmarshal(data, &message)
+	if string(parts[0]) == ClientVersion1_0 {
+		message.Version = ClientVersion1_0
+	} else {
+		return nil, fmt.Errorf("unsupported message version")
+	}
+
+	err := json.Unmarshal(parts[1], &message)
 	if err != nil {
 		return nil, err
 	}

common/messages/messages_test.go

@@ -1,7 +1,6 @@
 package messages
 
 import (
-	"bytes"
 	"encoding/json"
 	"fmt"
 	"testing"
@@ -286,14 +285,16 @@ func TestDecodeClientPollRequest(t *testing.T) {
 				//version 1.0 client message
 				"unknown",
 				"fake",
-				`{"nat":"unknown","offer":"fake"}`,
+				`1.0
+{"nat":"unknown","offer":"fake"}`,
 				nil,
 			},
 			{
 				//version 1.0 client message
 				"unknown",
 				"fake",
-				`{"offer":"fake"}`,
+				`1.0
+{"offer":"fake"}`,
 				nil,
 			},
 			{
@@ -307,16 +308,17 @@ func TestDecodeClientPollRequest(t *testing.T) {
 				//no offer
 				"",
 				"",
-				`{"nat":"unknown"}`,
+				`1.0
+{"nat":"unknown"}`,
 				fmt.Errorf(""),
 			},
 		} {
 			req, err := DecodeClientPollRequest([]byte(test.data))
+			So(err, ShouldHaveSameTypeAs, test.err)
 			if test.err == nil {
 				So(req.NAT, ShouldResemble, test.natType)
 				So(req.Offer, ShouldResemble, test.offer)
 			}
-			So(err, ShouldHaveSameTypeAs, test.err)
 		}
 
 	})
@@ -325,15 +327,12 @@ func TestDecodeClientPollRequest(t *testing.T) {
 func TestEncodeClientPollRequests(t *testing.T) {
 	Convey("Context", t, func() {
 		req1 := &ClientPollRequest{
-			NAT:   "unknown",
-			Offer: "fake",
+			NAT:     "unknown",
+			Offer:   "fake",
+			Version: ClientVersion1_0,
 		}
 		b, err := req1.EncodeClientPollRequest()
 		So(err, ShouldEqual, nil)
-		fmt.Println(string(b))
-		parts := bytes.SplitN(b, []byte("\n"), 2)
-		So(string(parts[0]), ShouldEqual, "1.0")
-		b = parts[1]
 		req2, err := DecodeClientPollRequest(b)
 		So(err, ShouldEqual, nil)
 		So(req2, ShouldResemble, req1)