Add throughput field for ServiceMeshMetric (#51)

diff --git a/service-mesh-probe/service-mesh.proto b/service-mesh-probe/service-mesh.proto
index 5f09a06..0e0325e 100644
--- a/service-mesh-probe/service-mesh.proto
+++ b/service-mesh-probe/service-mesh.proto
@@ -56,6 +56,9 @@
     // The sidecar/proxy internal error code, the value bases on the implementation.
     // The envoy internal error codes are listed here, https://www.envoyproxy.io/docs/envoy/latest/api-v2/data/accesslog/v2/accesslog.proto#data-accesslog-v2-responseflags
     string internalErrorCode = 14;
+
+    // The tcp detail of the mesh metrics if it's a TCP metrics, otherwise should be empty.
+    TCPInfo tcp = 15;
 }
 
 enum Protocol {
@@ -64,5 +67,12 @@
     TCP = 2;
 }
 
+message TCPInfo {
+    // The received data in bytes
+    int64 receivedBytes = 1;
+    // The sent data in bytes
+    int64 sentBytes = 2;
+}
+
 message MeshProbeDownstream {
 }