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fix: Align channel data framing

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ref: #1928
This commit is contained in:
Janez T
2026-03-18 20:14:22 +01:00
parent a21b83b127
commit f25d7a882a
5 changed files with 63 additions and 56 deletions
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42
docs/companion_protocol.md
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@@ -303,7 +303,7 @@ Bytes 7+: Binary payload bytes (variable length)
- Values other than `0xFF` are reserved for official protocol extensions.
**Limits**:
- Maximum payload length is `163` bytes (`MAX_GROUP_DATA_LENGTH`).
- Maximum payload length is `160` bytes.
- Larger payloads are rejected with `PACKET_ERROR` / `ERR_CODE_ILLEGAL_ARG`.
**Response**: `PACKET_OK` (0x00) on success
@@ -326,7 +326,7 @@ Byte 0: 0x0A
**Response**:
- `PACKET_CHANNEL_MSG_RECV` (0x08) or `PACKET_CHANNEL_MSG_RECV_V3` (0x11) for channel messages
- `PACKET_CHANNEL_DATA_RECV` (0x1B) or `PACKET_CHANNEL_DATA_RECV_V3` (0x1C) for channel data
- `PACKET_CHANNEL_DATA_RECV` (0x1B) for channel data
- `PACKET_CONTACT_MSG_RECV` (0x07) or `PACKET_CONTACT_MSG_RECV_V3` (0x10) for contact messages
- `PACKET_NO_MORE_MSGS` (0x0A) if no messages available
@@ -397,8 +397,7 @@ Messages are received via the TX characteristic (notifications). The device send
- `PACKET_CHANNEL_MSG_RECV_V3` (0x11) - Version 3 with SNR
2. **Channel Data**:
- `PACKET_CHANNEL_DATA_RECV` (0x1B) - Standard format
- `PACKET_CHANNEL_DATA_RECV_V3` (0x1C) - Version 3 with SNR
- `PACKET_CHANNEL_DATA_RECV` (0x1B) - Includes SNR and reserved bytes
3. **Contact Messages**:
- `PACKET_CONTACT_MSG_RECV` (0x07) - Standard format
@@ -502,26 +501,17 @@ Bytes 11+: Payload bytes
### Channel Data Format
**Standard Format** (`PACKET_CHANNEL_DATA_RECV`, 0x1B):
**Format** (`PACKET_CHANNEL_DATA_RECV`, 0x1B):
```
Byte 0: 0x1B (packet type)
Byte 1: Channel Index (0-7)
Byte 2: Path Length
Byte 3: Data Type
Bytes 4-7: Timestamp (32-bit little-endian)
Bytes 8+: Payload bytes
```
**V3 Format** (`PACKET_CHANNEL_DATA_RECV_V3`, 0x1C):
```
Byte 0: 0x1C (packet type)
Byte 1: SNR (signed byte, multiplied by 4)
Bytes 2-3: Reserved
Byte 4: Channel Index (0-7)
Byte 5: Path Length
Byte 6: Data Type
Bytes 7-10: Timestamp (32-bit little-endian)
Bytes 11+: Payload bytes
Byte 7: Data Length
Bytes 8-11: Timestamp (32-bit little-endian)
Bytes 12+: Payload bytes
```
**Parsing Pseudocode**:
@@ -529,9 +519,10 @@ Bytes 11+: Payload bytes
def parse_channel_frame(data):
packet_type = data[0]
offset = 1
snr = None
# Check for V3 format
if packet_type in (0x11, 0x1C): # V3
# Formats with explicit SNR/reserved bytes
if packet_type in (0x11, 0x1B):
snr_byte = data[offset]
snr = ((snr_byte if snr_byte < 128 else snr_byte - 256) / 4.0)
offset += 3 # Skip SNR + reserved
@@ -539,8 +530,10 @@ def parse_channel_frame(data):
channel_idx = data[offset]
path_len = data[offset + 1]
item_type = data[offset + 2]
timestamp = int.from_bytes(data[offset+3:offset+7], 'little')
payload = data[offset+7:]
data_len = data[offset + 3] if packet_type == 0x1B else None
timestamp = int.from_bytes(data[offset+4:offset+8], 'little') if packet_type == 0x1B else int.from_bytes(data[offset+3:offset+7], 'little')
payload_offset = offset + 8 if packet_type == 0x1B else offset + 7
payload = data[payload_offset:payload_offset + data_len] if packet_type == 0x1B else data[payload_offset:]
is_text = packet_type in (0x08, 0x11)
if is_text and item_type == 0:
message = payload.decode('utf-8')
@@ -553,7 +546,7 @@ def parse_channel_frame(data):
'timestamp': timestamp,
'payload': payload,
'message': message,
'snr': snr if packet_type in (0x11, 0x1C) else None
'snr': snr
}
```
@@ -590,8 +583,7 @@ Use `CMD_SEND_CHANNEL_TXT_MSG` for plain text, and `CMD_SEND_CHANNEL_DATA` for b
| 0x10 | PACKET_CONTACT_MSG_RECV_V3 | Contact message (V3 with SNR) |
| 0x11 | PACKET_CHANNEL_MSG_RECV_V3 | Channel message (V3 with SNR) |
| 0x12 | PACKET_CHANNEL_INFO | Channel information |
| 0x1B | PACKET_CHANNEL_DATA_RECV | Channel data (standard) |
| 0x1C | PACKET_CHANNEL_DATA_RECV_V3| Channel data (V3 with SNR) |
| 0x1B | PACKET_CHANNEL_DATA_RECV | Channel data (includes SNR) |
| 0x80 | PACKET_ADVERTISEMENT | Advertisement packet |
| 0x82 | PACKET_ACK | Acknowledgment |
| 0x83 | PACKET_MESSAGES_WAITING | Messages waiting notification |
@@ -892,7 +884,7 @@ def on_notification_received(data):
packet_type = data[0]
if packet_type in (PACKET_CHANNEL_MSG_RECV, PACKET_CHANNEL_MSG_RECV_V3,
PACKET_CHANNEL_DATA_RECV, PACKET_CHANNEL_DATA_RECV_V3):
PACKET_CHANNEL_DATA_RECV):
message = parse_channel_frame(data)
handle_channel_message(message)
elif packet_type == PACKET_MESSAGES_WAITING:

33
examples/companion_radio/MyMesh.cpp
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@@ -93,7 +93,8 @@
#define RESP_CODE_AUTOADD_CONFIG 25
#define RESP_ALLOWED_REPEAT_FREQ 26
#define RESP_CODE_CHANNEL_DATA_RECV 27
#define RESP_CODE_CHANNEL_DATA_RECV_V3 28
#define MAX_CHANNEL_DATA_LENGTH (MAX_FRAME_SIZE - 12)
#define SEND_TIMEOUT_BASE_MILLIS 500
#define FLOOD_SEND_TIMEOUT_FACTOR 16.0f
@@ -208,7 +209,7 @@ void MyMesh::updateContactFromFrame(ContactInfo &contact, uint32_t& last_mod, co
bool MyMesh::Frame::isChannelMsg() const {
return buf[0] == RESP_CODE_CHANNEL_MSG_RECV || buf[0] == RESP_CODE_CHANNEL_MSG_RECV_V3 ||
buf[0] == RESP_CODE_CHANNEL_DATA_RECV || buf[0] == RESP_CODE_CHANNEL_DATA_RECV_V3;
buf[0] == RESP_CODE_CHANNEL_DATA_RECV;
}
void MyMesh::addToOfflineQueue(const uint8_t frame[], int len) {
@@ -570,28 +571,26 @@ void MyMesh::onChannelMessageRecv(const mesh::GroupChannel &channel, mesh::Packe
void MyMesh::onChannelDataRecv(const mesh::GroupChannel &channel, mesh::Packet *pkt, uint32_t timestamp, uint8_t data_type,
const uint8_t *data, size_t data_len) {
int i = 0;
if (app_target_ver >= 3) {
out_frame[i++] = RESP_CODE_CHANNEL_DATA_RECV_V3;
out_frame[i++] = (int8_t)(pkt->getSNR() * 4);
out_frame[i++] = 0; // reserved1
out_frame[i++] = 0; // reserved2
} else {
out_frame[i++] = RESP_CODE_CHANNEL_DATA_RECV;
if (data_len > MAX_CHANNEL_DATA_LENGTH) {
MESH_DEBUG_PRINTLN("onChannelDataRecv: dropping payload_len=%d exceeds frame limit=%d",
(uint32_t)data_len, (uint32_t)MAX_CHANNEL_DATA_LENGTH);
return;
}
int i = 0;
out_frame[i++] = RESP_CODE_CHANNEL_DATA_RECV;
out_frame[i++] = (int8_t)(pkt->getSNR() * 4);
out_frame[i++] = 0; // reserved1
out_frame[i++] = 0; // reserved2
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_len;
memcpy(&out_frame[i], &timestamp, 4);
i += 4;
size_t available = MAX_FRAME_SIZE - i;
if (data_len > available) {
MESH_DEBUG_PRINTLN("onChannelDataRecv(): payload_len=%d exceeds frame space=%d, truncating", (uint32_t)data_len, (uint32_t)available);
data_len = available;
}
int copy_len = (int)data_len;
if (copy_len > 0) {
memcpy(&out_frame[i], data, copy_len);
@@ -1108,8 +1107,8 @@ void MyMesh::handleCmdFrame(size_t len) {
writeErrFrame(ERR_CODE_NOT_FOUND); // bad channel_idx
} else if (data_type != DATA_TYPE_CUSTOM) {
writeErrFrame(ERR_CODE_UNSUPPORTED_CMD);
} else if (payload_len > MAX_GROUP_DATA_LENGTH) {
MESH_DEBUG_PRINTLN("CMD_SEND_CHANNEL_DATA payload too long: %d > %d", payload_len, MAX_GROUP_DATA_LENGTH);
} 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);
} else if (sendGroupData(msg_timestamp, channel.channel, data_type, payload, payload_len)) {
writeOKFrame();

2
src/MeshCore.h
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@@ -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 - 5)
#define MAX_GROUP_DATA_LENGTH (MAX_PACKET_PAYLOAD - CIPHER_BLOCK_SIZE - 6)
#define MAX_PATH_SIZE 64
#define MAX_TRANS_UNIT 255

2
src/Packet.h
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@@ -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: timestamp, blob)
#define PAYLOAD_TYPE_GRP_DATA 0x06 // an (unverified) group datagram (prefixed with channel hash, MAC) (enc data: timestamp, 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)
#define PAYLOAD_TYPE_TRACE 0x09 // trace a path, collecting SNI for each hop

40
src/helpers/BaseChatMesh.cpp
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@@ -353,15 +353,15 @@ int BaseChatMesh::searchChannelsByHash(const uint8_t* hash, mesh::GroupChannel d
#endif
void BaseChatMesh::onGroupDataRecv(mesh::Packet* packet, uint8_t type, const mesh::GroupChannel& channel, uint8_t* data, size_t len) {
if (len < 5) {
MESH_DEBUG_PRINTLN("onGroupDataRecv: dropping short group payload len=%d", (uint32_t)len);
return;
}
uint8_t data_type = data[4];
if (type == PAYLOAD_TYPE_GRP_TXT) {
if ((data_type >> 2) != 0) {
MESH_DEBUG_PRINTLN("onGroupDataRecv: dropping unsupported group text type=%d", (uint32_t)data_type);
if (len < 5) {
MESH_DEBUG_PRINTLN("onGroupDataRecv: dropping short group text payload len=%d", (uint32_t)len);
return;
}
uint8_t txt_type = data[4];
if ((txt_type >> 2) != 0) {
MESH_DEBUG_PRINTLN("onGroupDataRecv: dropping unsupported group text type=%d", (uint32_t)txt_type);
return;
}
@@ -374,9 +374,24 @@ 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 < 6) {
MESH_DEBUG_PRINTLN("onGroupDataRecv: dropping short group data payload len=%d", (uint32_t)len);
return;
}
uint32_t timestamp;
memcpy(&timestamp, data, 4);
onChannelDataRecv(channel, packet, timestamp, data_type, &data[5], len - 5);
uint8_t data_type = data[4];
uint8_t data_len = data[5];
size_t available_len = len - 6;
if (data_len > available_len) {
MESH_DEBUG_PRINTLN("onGroupDataRecv: dropping malformed group data type=%d len=%d available=%d",
(uint32_t)data_type, (uint32_t)data_len, (uint32_t)available_len);
return;
}
onChannelDataRecv(channel, packet, timestamp, data_type, &data[6], data_len);
}
}
@@ -478,12 +493,13 @@ bool BaseChatMesh::sendGroupData(uint32_t timestamp, mesh::GroupChannel& channel
return false;
}
uint8_t temp[5 + MAX_GROUP_DATA_LENGTH];
uint8_t temp[6 + MAX_GROUP_DATA_LENGTH];
memcpy(temp, &timestamp, 4);
temp[4] = data_type;
if (data_len > 0) memcpy(&temp[5], data, data_len);
temp[5] = (uint8_t)data_len;
if (data_len > 0) memcpy(&temp[6], data, data_len);
auto pkt = createGroupDatagram(PAYLOAD_TYPE_GRP_DATA, channel, temp, 5 + data_len);
auto pkt = createGroupDatagram(PAYLOAD_TYPE_GRP_DATA, channel, temp, 6 + data_len);
if (pkt == NULL) {
MESH_DEBUG_PRINTLN("sendGroupData: unable to create group datagram, data_len=%d", data_len);
return false;