meshtastic: support

protocol/meshtastic/packet.go

@@ -0,0 +1,159 @@
+package meshtastic
+
+import (
+	"encoding/binary"
+	"encoding/json"
+	"errors"
+
+	meshtasticpb "git.maze.io/go/ham/protocol/meshtastic/pb"
+	"google.golang.org/protobuf/proto"
+)
+
+const (
+	minPacketSize  = 4 + 4 + 4 + 1 + 1 + 1 + 1
+	maxPayloadSize = 237
+)
+
+var (
+	// ErrInvalidPacket signals the source buffer does not contain a valid packet.
+	ErrInvalidPacket = errors.New("meshtastic: invalid packet")
+)
+
+type Packet struct {
+	Destination    NodeID               `json:"destination"`
+	Source         NodeID               `json:"source"`
+	ID             uint32               `json:"id"`
+	Flags          uint8                `json:"flags"`
+	ChannelHash    uint8                `json:"channelHash"`
+	NextHop        uint8                `json:"nextHop"`
+	RelayNode      uint8                `json:"relayNode"`
+	PayloadLength  int                  `json:"-"`
+	Payload        [maxPayloadSize]byte `json:"-"`
+	Data           *meshtasticpb.Data   `json:"data,omitempty"`
+	DecodedPayload proto.Message        `json:"decodedPayload,omitempty"`
+	TextPayload    string               `json:"textPayload,omitempty"`
+}
+
+func (packet *Packet) Decode(data []byte) error {
+	if len(data) < minPacketSize {
+		return ErrInvalidPacket
+	}
+	if len(data[16:]) > maxPayloadSize {
+		return ErrInvalidPacket
+	}
+
+	packet.Source = parseNodeID(data[0:])
+	packet.Destination = parseNodeID(data[4:])
+	packet.ID = binary.LittleEndian.Uint32(data[8:])
+	packet.Flags = data[12]
+	packet.ChannelHash = data[13]
+	packet.NextHop = data[14]
+	packet.RelayNode = data[15]
+	packet.PayloadLength = len(data[16:])
+	copy(packet.Payload[:], data[16:])
+	packet.Data = nil
+	packet.DecodedPayload = nil
+	packet.TextPayload = ""
+
+	packet.decodePayloadProtobufs()
+
+	return nil
+}
+
+func (packet *Packet) PayloadBytes() []byte {
+	return packet.Payload[:packet.PayloadLength]
+}
+
+func (packet *Packet) HopLimit() int {
+	return 7
+}
+
+func parseNodeID(data []byte) NodeID {
+	return NodeID(binary.LittleEndian.Uint32(data))
+}
+
+func (packet *Packet) decodePayloadProtobufs() {
+	if packet.PayloadLength == 0 {
+		return
+	}
+
+	decodedData := &meshtasticpb.Data{}
+	if err := proto.Unmarshal(packet.PayloadBytes(), decodedData); err != nil {
+		return
+	}
+
+	packet.Data = decodedData
+
+	decodedPayload, textPayload := decodeDataPayload(decodedData.GetPortnum(), decodedData.GetPayload())
+	packet.DecodedPayload = decodedPayload
+	packet.TextPayload = textPayload
+}
+
+func decodeDataPayload(portNum meshtasticpb.PortNum, payload []byte) (proto.Message, string) {
+	if len(payload) == 0 {
+		return nil, ""
+	}
+
+	textPortNum := map[meshtasticpb.PortNum]struct{}{
+		meshtasticpb.PortNum_TEXT_MESSAGE_APP:            {},
+		meshtasticpb.PortNum_ALERT_APP:                   {},
+		meshtasticpb.PortNum_DETECTION_SENSOR_APP:        {},
+		meshtasticpb.PortNum_REPLY_APP:                   {},
+		meshtasticpb.PortNum_RANGE_TEST_APP:              {},
+		meshtasticpb.PortNum_TEXT_MESSAGE_COMPRESSED_APP: {},
+	}
+	if _, ok := textPortNum[portNum]; ok {
+		return nil, string(payload)
+	}
+
+	var message proto.Message
+	switch portNum {
+	case meshtasticpb.PortNum_REMOTE_HARDWARE_APP:
+		message = &meshtasticpb.HardwareMessage{}
+	case meshtasticpb.PortNum_POSITION_APP:
+		message = &meshtasticpb.Position{}
+	case meshtasticpb.PortNum_NODEINFO_APP:
+		message = &meshtasticpb.User{}
+	case meshtasticpb.PortNum_ROUTING_APP:
+		message = &meshtasticpb.Routing{}
+	case meshtasticpb.PortNum_ADMIN_APP:
+		message = &meshtasticpb.AdminMessage{}
+	case meshtasticpb.PortNum_WAYPOINT_APP:
+		message = &meshtasticpb.Waypoint{}
+	case meshtasticpb.PortNum_KEY_VERIFICATION_APP:
+		message = &meshtasticpb.KeyVerification{}
+	case meshtasticpb.PortNum_PAXCOUNTER_APP:
+		message = &meshtasticpb.Paxcount{}
+	case meshtasticpb.PortNum_STORE_FORWARD_PLUSPLUS_APP:
+		message = &meshtasticpb.StoreForwardPlusPlus{}
+	case meshtasticpb.PortNum_STORE_FORWARD_APP:
+		message = &meshtasticpb.StoreAndForward{}
+	case meshtasticpb.PortNum_TELEMETRY_APP:
+		message = &meshtasticpb.Telemetry{}
+	case meshtasticpb.PortNum_TRACEROUTE_APP:
+		message = &meshtasticpb.RouteDiscovery{}
+	case meshtasticpb.PortNum_NEIGHBORINFO_APP:
+		message = &meshtasticpb.NeighborInfo{}
+	case meshtasticpb.PortNum_NODE_STATUS_APP:
+		message = &meshtasticpb.StatusMessage{}
+	default:
+		return nil, ""
+	}
+
+	if err := proto.Unmarshal(payload, message); err != nil {
+		return nil, ""
+	}
+	return message, ""
+}
+
+// MarshalJSON implements custom JSON marshaling for Packet.
+func (packet *Packet) MarshalJSON() ([]byte, error) {
+	type Alias Packet
+	return json.Marshal(&struct {
+		*Alias
+		Raw []byte `json:"raw"`
+	}{
+		Alias: (*Alias)(packet),
+		Raw:   packet.PayloadBytes(),
+	})
+}