recipes-connectivity/mctp-controller-init/mctp-controller-init-usb/init-mctp-usb-endpoint.sh

#!/bin/bash

# TODO: Remove this once mctp-controller-init-v2 is enabled on a platform.

# Redirect all stdout and stderr to systemd-cat, which logs to journalctl.
# We can filter the messages with `journalctl -f -t usb_mctp_init`
exec > >(systemd-cat -t "usb_mctp_init") 2>&1

echo "Device found at (DEVPATH): ${DEVPATH}"

EID_OFFSET=100
EID_END=254

# The EID for the USB-MCTP interface.
# This value is an input from the udev rule.
LOCAL_EID=$1

# if the provided LOCAL_EID is missing or invalid, generate a EID
if [ -z "${LOCAL_EID}" ] || ! [[ "${LOCAL_EID}" =~ ^[0-9]+$ ]] || \
   [ "${LOCAL_EID}" -lt ${EID_OFFSET} ] || [ "${LOCAL_EID}" -gt ${EID_END} ]; then

    if [ -z "${LOCAL_EID}" ]; then
        echo "Missing EID input parameter. Generating a random EID." >&2
    else
        echo "Invalid EID: '${LOCAL_EID}'. Must be an integer between" \
             "'${EID_OFFSET}' and '${EID_END}'. Generating a random EID." >&2
    fi

    #
    # Generate a unique ID for the local interface. This method could lead to
    # overlapping values. A better way to do this would be to track both
    # ADD/REMOVE events and keep track of a list of used EIDs and assign an new
    # EID. But this requires a extra config and file read locking. For now this
    # is the simplest way.
    #
    # We should always try to pass a valid EID from a platform specific config.
    #
    HASH_HEX=$(echo -n "${DEVPATH}" | md5sum | cut -d ' ' -f 1)
    HASH_HEX_SHORT=$(echo -n "${HASH_HEX}" | cut -c 1-8)
    HASH_DEC=$(( 0x${HASH_HEX_SHORT} ))
    RANGE_SIZE=$(( ${EID_END} - ${EID_OFFSET} ))
    LOCAL_EID=$(( (${HASH_DEC} % ${RANGE_SIZE}) + ${EID_OFFSET} ))
fi

echo "  Using LOCAL_EID: ${LOCAL_EID}"

# Function to get the interface name.
# Returns the interface name if found, otherwise an empty string.
get_iface_name() {
    local sysfs_net_path=$1
    local iface_name=""

    if [ -d "${sysfs_net_path}" ]; then
        # Find the first directory inside the 'net' path.
        # This loop is a safe way to get the name.
        for iface_path in "${sysfs_net_path}"/*;
        do
            if [ -e "${iface_path}" ]; then
                # The interface name is the directory's basename
                iface_name=$(basename "${iface_path}")
                break # Exit loop after finding the first interface
            fi
        done
    fi
    echo "${iface_name}"
}

# The full sysfs path to the USB interface's 'net' subdirectory
SYSFS_NET_PATH="/sys${DEVPATH}/net"

IFACE_NAME=$(get_iface_name "${SYSFS_NET_PATH}")

if [ -z "${IFACE_NAME}" ]; then
    echo "No network interface found. Directory '${SYSFS_NET_PATH}'" \
         "does not exist." >&2
    exit 4
fi

echo "Successfully found network interface: ${IFACE_NAME}"

mctp link set "${IFACE_NAME}" up
mctp addr add "${LOCAL_EID}" dev "${IFACE_NAME}"