fix: Widen grp data type

ref: #1928

docs/companion_protocol.md

@@ -288,20 +288,20 @@ Bytes 7+: Message Text (UTF-8, variable length)
 **Command Format**:
 ```
 Byte 0: 0x3E
-Byte 1: Data Type (`data_type`)
+Bytes 1-2: Data Type (`data_type`, 16-bit little-endian)
-Byte 2: Channel Index (0-7)
+Byte 3: Channel Index (0-7)
-Bytes 3+: Binary payload bytes (variable length)
+Bytes 4+: Binary payload bytes (variable length)
 ```
 
 **Data Type / Transport Mapping**:
-- `0xFF` (`DATA_TYPE_CUSTOM`) must be used for custom-protocol binary datagrams.
+- `0x0000` is invalid for this command.
-- `0x00` is invalid for this command.
+- `0xFFFF` (`DATA_TYPE_CUSTOM`) is the generic custom-app namespace.
-- Values other than `0xFF` are reserved for official protocol extensions.
+- Other non-zero values can be used as assigned application/community namespaces.
 
 **Note**: Applications that need a timestamp should encode it inside the binary payload.
 
 **Limits**:
-- Maximum payload length is `166` bytes.
+- Maximum payload length is `163` bytes.
 - Larger payloads are rejected with `PACKET_ERROR`.
 
 **Response**: `PACKET_OK` (0x00) on success

docs/faq.md

@@ -386,7 +386,7 @@ https://github.com/meshcore-dev/MeshCore/blob/main/src/Packet.h#L19
     #define PAYLOAD_TYPE_TXT_MSG 0x02 // a plain text message (prefixed with dest/src hashes, MAC) (enc data: timestamp, text)
     #define PAYLOAD_TYPE_ACK 0x03 // a simple ack #define PAYLOAD_TYPE_ADVERT 0x04 // a node advertising its Identity
     #define PAYLOAD_TYPE_GRP_TXT 0x05 // an (unverified) group text message (prefixed with channel hash, MAC) (enc data: timestamp, "name: msg")
-    #define PAYLOAD_TYPE_GRP_DATA 0x06 // an (unverified) group datagram (prefixed with channel hash, MAC) (enc data: timestamp, blob)
+    #define PAYLOAD_TYPE_GRP_DATA 0x06 // an (unverified) group datagram (prefixed with channel hash, MAC) (enc data: data_type, data_len, blob)
     #define PAYLOAD_TYPE_ANON_REQ 0x07 // generic request (prefixed with dest_hash, ephemeral pub_key, MAC) (enc data: ...)
     #define PAYLOAD_TYPE_PATH 0x08 // returned path (prefixed with dest/src hashes, MAC) (enc data: path, extra)
 

examples/companion_radio/MyMesh.cpp

@@ -94,7 +94,7 @@
 #define RESP_ALLOWED_REPEAT_FREQ      26
 #define RESP_CODE_CHANNEL_DATA_RECV   27
 
-#define MAX_CHANNEL_DATA_LENGTH       (MAX_FRAME_SIZE - 8)
+#define MAX_CHANNEL_DATA_LENGTH       (MAX_FRAME_SIZE - 9)
 
 #define SEND_TIMEOUT_BASE_MILLIS        500
 #define FLOOD_SEND_TIMEOUT_FACTOR       16.0f
@@ -569,7 +569,7 @@ void MyMesh::onChannelMessageRecv(const mesh::GroupChannel &channel, mesh::Packe
 #endif
 }
 
-void MyMesh::onChannelDataRecv(const mesh::GroupChannel &channel, mesh::Packet *pkt, uint8_t data_type,
+void MyMesh::onChannelDataRecv(const mesh::GroupChannel &channel, mesh::Packet *pkt, uint16_t data_type,
                                const uint8_t *data, size_t data_len) {
   if (data_len > MAX_CHANNEL_DATA_LENGTH) {
     MESH_DEBUG_PRINTLN("onChannelDataRecv: dropping payload_len=%d exceeds frame limit=%d",
@@ -586,7 +586,8 @@ void MyMesh::onChannelDataRecv(const mesh::GroupChannel &channel, mesh::Packet *
   uint8_t channel_idx = findChannelIdx(channel);
   out_frame[i++] = channel_idx;
   out_frame[i++] = pkt->isRouteFlood() ? pkt->path_len : 0xFF;
-  out_frame[i++] = data_type;
+  out_frame[i++] = (uint8_t)(data_type & 0xFF);
+  out_frame[i++] = (uint8_t)(data_type >> 8);
   out_frame[i++] = (uint8_t)data_len;
 
   int copy_len = (int)data_len;
@@ -1091,8 +1092,13 @@ void MyMesh::handleCmdFrame(size_t len) {
       }
     }
   } else if (cmd_frame[0] == CMD_SEND_CHANNEL_DATA) { // send GroupChannel datagram
+    if (len < 4) {
+      writeErrFrame(ERR_CODE_ILLEGAL_ARG);
+      return;
+    }
     int i = 1;
-    uint8_t data_type = cmd_frame[i++];
+    uint16_t data_type = ((uint16_t)cmd_frame[i]) | (((uint16_t)cmd_frame[i + 1]) << 8);
+    i += 2;
     uint8_t channel_idx = cmd_frame[i++];
     const uint8_t *payload = &cmd_frame[i];
     int payload_len = (len > (size_t)i) ? (int)(len - i) : 0;
@@ -1100,8 +1106,8 @@ void MyMesh::handleCmdFrame(size_t len) {
     ChannelDetails channel;
     if (!getChannel(channel_idx, channel)) {
       writeErrFrame(ERR_CODE_NOT_FOUND); // bad channel_idx
-    } else if (data_type != DATA_TYPE_CUSTOM) {
+    } else if (data_type == 0) {
-      writeErrFrame(ERR_CODE_UNSUPPORTED_CMD);
+      writeErrFrame(ERR_CODE_ILLEGAL_ARG);
     } else if (payload_len > MAX_CHANNEL_DATA_LENGTH) {
       MESH_DEBUG_PRINTLN("CMD_SEND_CHANNEL_DATA payload too long: %d > %d", payload_len, MAX_CHANNEL_DATA_LENGTH);
       writeErrFrame(ERR_CODE_ILLEGAL_ARG);

examples/companion_radio/MyMesh.h

@@ -137,7 +137,7 @@ protected:
                            const uint8_t *sender_prefix, const char *text) override;
   void onChannelMessageRecv(const mesh::GroupChannel &channel, mesh::Packet *pkt, uint32_t timestamp,
                             const char *text) override;
-  void onChannelDataRecv(const mesh::GroupChannel &channel, mesh::Packet *pkt, uint8_t data_type,
+  void onChannelDataRecv(const mesh::GroupChannel &channel, mesh::Packet *pkt, uint16_t data_type,
                          const uint8_t *data, size_t data_len) override;
 
   uint8_t onContactRequest(const ContactInfo &contact, uint32_t sender_timestamp, const uint8_t *data,

src/MeshCore.h

@@ -17,7 +17,7 @@
 #define PATH_HASH_SIZE       1
 
 #define MAX_PACKET_PAYLOAD  184
-#define MAX_GROUP_DATA_LENGTH  (MAX_PACKET_PAYLOAD - CIPHER_BLOCK_SIZE - 2)
+#define MAX_GROUP_DATA_LENGTH  (MAX_PACKET_PAYLOAD - CIPHER_BLOCK_SIZE - 3)
 #define MAX_PATH_SIZE        64
 #define MAX_TRANS_UNIT      255
 

src/Packet.h

@@ -22,7 +22,7 @@ namespace mesh {
 #define PAYLOAD_TYPE_ACK         0x03    // a simple ack
 #define PAYLOAD_TYPE_ADVERT      0x04    // a node advertising its Identity
 #define PAYLOAD_TYPE_GRP_TXT     0x05    // an (unverified) group text message (prefixed with channel hash, MAC) (enc data: timestamp, "name: msg")
-#define PAYLOAD_TYPE_GRP_DATA    0x06    // an (unverified) group datagram (prefixed with channel hash, MAC) (enc data: data_type, data_len, blob)
+#define PAYLOAD_TYPE_GRP_DATA    0x06    // an (unverified) group datagram (prefixed with channel hash, MAC) (enc data: data_type(uint16), data_len, blob)
 #define PAYLOAD_TYPE_ANON_REQ    0x07    // generic request (prefixed with dest_hash, ephemeral pub_key, MAC) (enc data: ...)
 #define PAYLOAD_TYPE_PATH        0x08    // returned path (prefixed with dest/src hashes, MAC) (enc data: path, extra)
 #define PAYLOAD_TYPE_TRACE       0x09    // trace a path, collecting SNI for each hop

src/helpers/BaseChatMesh.cpp

@@ -374,14 +374,14 @@ void BaseChatMesh::onGroupDataRecv(mesh::Packet* packet, uint8_t type, const mes
     // notify UI  of this new message
     onChannelMessageRecv(channel, packet, timestamp, (const char *) &data[5]);  // let UI know
   } else if (type == PAYLOAD_TYPE_GRP_DATA) {
-    if (len < 2) {
+    if (len < 3) {
       MESH_DEBUG_PRINTLN("onGroupDataRecv: dropping short group data payload len=%d", (uint32_t)len);
       return;
     }
 
-    uint8_t data_type = data[0];
+    uint16_t data_type = ((uint16_t)data[0]) | (((uint16_t)data[1]) << 8);
-    uint8_t data_len = data[1];
+    uint8_t data_len = data[2];
-    size_t available_len = len - 2;
+    size_t available_len = len - 3;
 
     if (data_len > available_len) {
       MESH_DEBUG_PRINTLN("onGroupDataRecv: dropping malformed group data type=%d len=%d available=%d",
@@ -389,7 +389,7 @@ void BaseChatMesh::onGroupDataRecv(mesh::Packet* packet, uint8_t type, const mes
       return;
     }
 
-    onChannelDataRecv(channel, packet, data_type, &data[2], data_len);
+    onChannelDataRecv(channel, packet, data_type, &data[3], data_len);
   }
 }
 
@@ -481,7 +481,7 @@ bool BaseChatMesh::sendGroupMessage(uint32_t timestamp, mesh::GroupChannel& chan
   return false;
 }
 
-bool BaseChatMesh::sendGroupData(mesh::GroupChannel& channel, uint8_t data_type, const uint8_t* data, int data_len) {
+bool BaseChatMesh::sendGroupData(mesh::GroupChannel& channel, uint16_t data_type, const uint8_t* data, int data_len) {
   if (data_len < 0) {
     MESH_DEBUG_PRINTLN("sendGroupData: invalid negative data_len=%d", data_len);
     return false;
@@ -491,12 +491,13 @@ bool BaseChatMesh::sendGroupData(mesh::GroupChannel& channel, uint8_t data_type,
     return false;
   }
 
-  uint8_t temp[2 + MAX_GROUP_DATA_LENGTH];
+  uint8_t temp[3 + MAX_GROUP_DATA_LENGTH];
-  temp[0] = data_type;
+  temp[0] = (uint8_t)(data_type & 0xFF);
-  temp[1] = (uint8_t)data_len;
+  temp[1] = (uint8_t)(data_type >> 8);
-  if (data_len > 0) memcpy(&temp[2], data, data_len);
+  temp[2] = (uint8_t)data_len;
+  if (data_len > 0) memcpy(&temp[3], data, data_len);
 
-  auto pkt = createGroupDatagram(PAYLOAD_TYPE_GRP_DATA, channel, temp, 2 + data_len);
+  auto pkt = createGroupDatagram(PAYLOAD_TYPE_GRP_DATA, channel, temp, 3 + data_len);
   if (pkt == NULL) {
     MESH_DEBUG_PRINTLN("sendGroupData: unable to create group datagram, data_len=%d", data_len);
     return false;

src/helpers/BaseChatMesh.h

@@ -111,7 +111,7 @@ protected:
   virtual uint32_t calcDirectTimeoutMillisFor(uint32_t pkt_airtime_millis, uint8_t path_len) const = 0;
   virtual void onSendTimeout() = 0;
   virtual void onChannelMessageRecv(const mesh::GroupChannel& channel, mesh::Packet* pkt, uint32_t timestamp, const char *text) = 0;
-  virtual void onChannelDataRecv(const mesh::GroupChannel& channel, mesh::Packet* pkt, uint8_t data_type,
+  virtual void onChannelDataRecv(const mesh::GroupChannel& channel, mesh::Packet* pkt, uint16_t data_type,
                                  const uint8_t* data, size_t data_len) {}
   virtual uint8_t onContactRequest(const ContactInfo& contact, uint32_t sender_timestamp, const uint8_t* data, uint8_t len, uint8_t* reply) = 0;
   virtual void onContactResponse(const ContactInfo& contact, const uint8_t* data, uint8_t len) = 0;
@@ -150,7 +150,7 @@ public:
   int  sendMessage(const ContactInfo& recipient, uint32_t timestamp, uint8_t attempt, const char* text, uint32_t& expected_ack, uint32_t& est_timeout);
   int  sendCommandData(const ContactInfo& recipient, uint32_t timestamp, uint8_t attempt, const char* text, uint32_t& est_timeout);
   bool sendGroupMessage(uint32_t timestamp, mesh::GroupChannel& channel, const char* sender_name, const char* text, int text_len);
-  bool sendGroupData(mesh::GroupChannel& channel, uint8_t data_type, const uint8_t* data, int data_len);
+  bool sendGroupData(mesh::GroupChannel& channel, uint16_t data_type, const uint8_t* data, int data_len);
   int  sendLogin(const ContactInfo& recipient, const char* password, uint32_t& est_timeout);
   int  sendAnonReq(const ContactInfo& recipient, const uint8_t* data, uint8_t len, uint32_t& tag, uint32_t& est_timeout);
   int  sendRequest(const ContactInfo& recipient, uint8_t req_type, uint32_t& tag, uint32_t& est_timeout);

src/helpers/TxtDataHelpers.h

@@ -3,10 +3,10 @@
 #include <stddef.h>
 #include <stdint.h>
 
-#define TXT_TYPE_PLAIN          0    // a plain text message
+#define TXT_TYPE_PLAIN          0      // a plain text message
-#define TXT_TYPE_CLI_DATA       1    // a CLI command
+#define TXT_TYPE_CLI_DATA       1      // a CLI command
-#define TXT_TYPE_SIGNED_PLAIN   2    // plain text, signed by sender
+#define TXT_TYPE_SIGNED_PLAIN   2      // plain text, signed by sender
-#define DATA_TYPE_CUSTOM        0xFF // custom app binary payload (group/channel datagrams)
+#define DATA_TYPE_CUSTOM        0xFFFF // generic custom app namespace for group/channel datagrams
 
 class StrHelper {
 public: