support compress for rpc and tun data (#473)

* support compress for rpc and tun data
* add compression layer to easytier-web

easytier/src/proto/common.proto

@@ -20,6 +20,7 @@ message FlagsInConfig {
   bool disable_udp_hole_punching = 13;
   string ipv6_listener = 14;
   bool multi_thread = 15;
+  CompressionAlgoPb data_compress_algo = 16;
 }
 
 message RpcDescriptor {
@@ -32,7 +33,7 @@ message RpcDescriptor {
 }
 
 message RpcRequest {
-  RpcDescriptor descriptor = 1;
+  RpcDescriptor descriptor = 1 [ deprecated = true ];
 
   bytes request = 2;
   int32 timeout_ms = 3;
@@ -45,6 +46,21 @@ message RpcResponse {
   uint64 runtime_us = 3;
 }
 
+enum CompressionAlgoPb {
+  Invalid = 0;
+  None = 1;
+  Zstd = 2;
+}
+
+message RpcCompressionInfo {
+  // use this to compress the content
+  CompressionAlgoPb algo = 1;
+
+  // tell the peer which compression algo is used to compress the next
+  // response/request
+  CompressionAlgoPb accepted_algo = 2;
+}
+
 message RpcPacket {
   uint32 from_peer = 1;
   uint32 to_peer = 2;
@@ -58,6 +74,8 @@ message RpcPacket {
   uint32 piece_idx = 8;
 
   int32 trace_id = 9;
+
+  RpcCompressionInfo compression_info = 10;
 }
 
 message Void {}