Bluetooth HCI Command Packet AttributeError

[sacca97]

Brief description

When building an HCI Command Packet, trying to access the opcode raises AttributeError.
This causes, among other things, the BluetoothUserSocket send_command to crash.
However, the issue is not present when the packets are received and automatically parsed. Which makes me question if that is the correct way of building the packet.

Scapy version

2.6.1

Python version

3.13

Operating system

Linux 6.14.4

Additional environment information

No response

How to reproduce

(assuming cmd is any valid HCI_Cmd_X),

pkt = HCI_Hdr() / HCI_Command_Hdr() / cmd
print(pkt.opcode)

Actual result

  File "/home/x/Projects/y/z/hci.py", line 18, in send_cmd
    print(pkt.opcode)
          ^^^^^^^^^^
  File "/home/x/Projects/y/.z/lib64/python3.13/site-packages/scapy/packet.py", line 482, in __getattr__
    return self.payload.__getattr__(attr)
           ~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "/home/x/Projects/y/.z/lib64/python3.13/site-packages/scapy/packet.py", line 482, in __getattr__
    return self.payload.__getattr__(attr)
           ~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "/home/x/Projects/y/.z/lib64/python3.13/site-packages/scapy/packet.py", line 482, in __getattr__
    return self.payload.__getattr__(attr)
           ~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "/home/x/Projects/y/.z/lib64/python3.13/site-packages/scapy/packet.py", line 480, in __getattr__
    fld, v = self.getfield_and_val(attr)
             ~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "/home/x/Projects/y/.z/lib64/python3.13/site-packages/scapy/packet.py", line 1886, in getfield_and_val
    raise AttributeError(attr)
AttributeError: opcode

Expected result

To print the actual opcode.

Related resources

No response

[gpotter2]

"opcode" isn't a defined field.
Did you first try

pkt = HCI_Hdr() / HCI_Command_Hdr()
pkt.show()

[sacca97]

@gpotter2 opcode is a property of hci_command_hdr and this issue breaks BluetoothUserSocket send_command function.

def send_command(self, cmd):
        opcode = cmd.opcode
        self.send(cmd)
        while True:
            r = self.recv()
            if r.type == 0x04 and r.code == 0xe and r.opcode == opcode:
                if r.status != 0:
                    raise BluetoothCommandError("Command %x failed with %x" % (opcode, r.status))  # noqa: E501
                return r

[gpotter2]

Sorry about that, I read your issue a bit too quickly.
Does #4754 look good?

[sacca97]

No worries and yep that works.