Remote Shell Protobufs (#892)

* Add initial dmshell
* Remove unused code
* Internally use RemoteShell
* Formatting fix
* Clarify comment for REMOTE_SHELL_APP

Co-authored-by: Thomas Göttgens <tgoettgens@gmail.com>

Author: jp-bennett

meshtastic/mesh.options

@@ -74,6 +74,8 @@
 *StoreForwardPlusPlus.root_hash max_size:32
 *StoreForwardPlusPlus.message max_size:240
 
+*RemoteShell.payload max_size:200
+
 *StatusMessage.status max_size:80
 
 # MyMessage.name         max_size:40 

meshtastic/mesh.proto

@@ -1288,6 +1288,76 @@ message StoreForwardPlusPlus {
   uint32 chain_count = 10;
 }
 
+/*
+ * The actual over-the-mesh message doing RemoteShell
+ */
+message RemoteShell {
+  /*
+   * Frame op code for PTY session control and stream transport.
+   *
+   * Values 1-63 are client->server requests.
+   * Values 64-127 are server->client responses/events.
+   */
+  enum OpCode {
+    OP_UNSET = 0;
+
+    // Client -> server
+    OPEN = 1;
+    INPUT = 2;
+    RESIZE = 3;
+    CLOSE = 4;
+    PING = 5;
+    ACK = 6;
+
+    // Server -> client
+    OPEN_OK = 64;
+    OUTPUT = 65;
+    CLOSED = 66;
+    ERROR = 67;
+    PONG = 68;
+  }
+
+  /*
+   * Structured frame operation.
+   */
+  OpCode op = 1;
+
+  /*
+   * Logical PTY session identifier.
+   */
+  uint32 session_id = 2;
+
+  /*
+   * Monotonic sequence number for this frame.
+   */
+  uint32 seq = 3;
+
+  /*
+   * Cumulative ack sequence number.
+   */
+  uint32 ack_seq = 4;
+
+  /*
+   * Opaque bytes payload for INPUT/OUTPUT/ERROR and other frame bodies.
+   */
+  bytes payload = 5;
+
+  /*
+   * Terminal size columns used for OPEN/RESIZE signaling.
+   */
+  uint32 cols = 6;
+
+  /*
+   * Terminal size rows used for OPEN/RESIZE signaling.
+   */
+  uint32 rows = 7;
+
+  /*
+   * Bit flags for protocol extensions.
+   */
+  uint32 flags = 8;
+}
+
 /*
  * Waypoint message, used to share arbitrary locations across the mesh
  */

meshtastic/portnums.proto

@@ -115,6 +115,11 @@ enum PortNum {
    */
   KEY_VERIFICATION_APP = 12;
 
+  /*
+   * Module/port for handling primitive remote shell access.
+   */
+  REMOTE_SHELL_APP = 13;
+
   /*
    * Provides a 'ping' service that replies to any packet it receives.
    * Also serves as a small example module.