Fix #104: Display correct protocol name in logs

- Add protocol field to http2Interop struct to track actual protocol
- Use stored protocol name instead of hardcoded 'grpc' in output
- Now http2 mode shows 'http2:' prefix and grpc mode shows 'grpc:' prefix
- Move grpcHeaderLen constant to grpc.go to avoid duplication

protocol/grpc.go

@@ -8,6 +8,8 @@ import (
 	"google.golang.org/protobuf/encoding/protowire"
 )
 
+const grpcHeaderLen = 5
+
 type grpcExplainer struct{}
 
 func (g *grpcExplainer) explain(b []byte) string {

protocol/http2.go

@@ -18,7 +18,6 @@ const (
 	http2HeaderLen          = 9
 	http2Preface            = "PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n"
 	http2SettingsPayloadLen = 6
-	grpcHeaderLen           = 5
 )
 
 type (
@@ -28,6 +27,7 @@ type (
 
 	http2Interop struct {
 		explainer dataExplainer
+		protocol  string
 	}
 )
 
@@ -44,8 +44,12 @@ func (i *http2Interop) Dump(r io.Reader, source string, id int, quiet bool) {
 			var index int
 			for index < n {
 				frameInfo, moreInfo, offset := i.explain(data[index:n])
+				protocol := i.protocol
+				if len(protocol) == 0 {
+					protocol = http2Protocol
+				}
 				buf.WriteString(fmt.Sprintf("%s%s%s\n",
-					color.HiBlueString("%s:(", grpcProtocol),
+					color.HiBlueString("%s:(", protocol),
 					color.HiYellowString(frameInfo),
 					color.HiBlueString(")")))
 				end := index + offset

protocol/interop.go

@@ -35,9 +35,12 @@ func CreateInterop(protocol string) Interop {
 	case grpcProtocol:
 		return &http2Interop{
 			explainer: new(grpcExplainer),
+			protocol:  grpcProtocol,
 		}
 	case http2Protocol:
-		return new(http2Interop)
+		return &http2Interop{
+			protocol: http2Protocol,
+		}
 	case redisProtocol:
 		return new(redisInterop)
 	case mongoProtocol: