mctp-dev: MCTP device emulator

mctp-dev is a small Linux application that implements a simple MCTP endpoint device, connected to a usbredir (or serial) session.

Since the qemu emulator can speak usbredir too, this allows us to create a MCTP device that can be connected to a qemu quest, and is intended for testing and development of the guest system's MCTP stack.

The MCTP endpoint implements the MCTP control protocol, allowing device discovery and enumeration. New MCTP-based protocols should be straightforward to add to the mctp-dev framework.

Building

For most systems:

cargo build

mctp-dev uses the usbredir-rs crate, which has a dependency on system C libraries. You may need the libusbredirparser-dev and libusbredirhost-dev packages installed for your distribution.

Running

1. Run qemu with a usbredir connection to a pty:

    qemu-system-arm [...] -chardev pty,id=usbredir -device usb-redir,chardev=usbredir
   

   on starting, qemu will log a message providing a path to the new pty device:

    char device redirected to /dev/pts/0 (label usbredir)
   

2. Run mctp-dev, specifying the pty from above

    $ mctp-dev usb /dev/pts/0
    07:56:14 [INFO] Created MCTP USB transport on /dev/pts/0
    07:56:14 [INFO] MCTP Control Protocol server listening
   

Once the qemu guest is running, you will have an emulated USB device present:

# lsusb
Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 002: ID 0000:0000 mctp-dev MCTP over USB device

Provided you have a kernel with the MCTP-over-USB drivers present, you will also have a MCTP link available:

# mctp link
dev lo index 1 address 00:00:00:00:00:00 net 1 mtu 65536 up
dev mctpusb0 index 6 address none net 1 mtu 68 down

To bring up the link and enumerate the device:

# mctp addr add 8 dev mctpusb0
# mctp link set mctpusb0 up
# systemctl start mctpd
# busctl call \
  au.com.codeconstruct.MCTP1 \
  /au/com/codeconstruct/mctp1/interfaces/mctpusb0 \
  au.com.codeconstruct.MCTP.BusOwner1 \
  SetupEndpoint ay 0
yisb 9 1 "/au/com/codeconstruct/mctp1/networks/1/endpoints/9" true