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.

When built with the nvme-mi feature, the MCTP endpoint also supports the NVMe-MI protocol, emulating a simple MCTP-managed storage device. The NVMe-MI responder implementation is provided by the nvme-mi-dev crate.

We also support a test client for PLDM for File Transfer (type 7). When mctp-dev is assigned an MCTP EID, it will perform PLDM operations to read a file from the bus owner EID.

The PLDM client expects to find the File record as the first PDR entry, and will attempt to transfer the entire file. Upon completion, the file size and sha256 checksum will be printed:

11:06:34 [INFO] Transfer complete. 16384 bytes, sha256 b4d3f1859dc8170c1e1f34b936aff05339a7723b6680894380c23dd84ff7e22b

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.

To incorporate NVMe-MI responder support, add the nvme-mi feature:

cargo build --features nvme-mi

To enable the PLDM File functionality, add the pldm feature:

cargo build --features pldm

Both may be enabled in the same build too:

cargo build --features nvme-mi,pldm

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