Validate an e1000e NVM Checksum from Userspace

e1000e-nvm-checksum.py

#!/usr/bin/env python3

import argparse
import re
import subprocess
import sys

from numpy import uint16

NEWLINES = re.compile(r'\r?\n', re.I)
WHITESPACE = re.compile(r'\s+', re.I)
ETHTOOL_BYTES = re.compile(r'^0x[a-f0-9]+:\s+((?:[a-f0-9]{2}\s*)+)$', re.I)


def bytes_to_words(bytearr):
    """Convert a series of bytes into little-endian 16-bit unsigned integers."""
    return [(bytearr[i + 1] << 8) | bytearr[i] for i in range(0, len(bytearr), 2)]


def validate_checksum(words):
    """Validates the NVM checksum to equal 0xBABA."""
    checksum = uint16(words).sum(dtype=uint16)

    return checksum == 0xbaba


def load_bytes(device):
    """Loads bytes 0x00-0x80 from the given ethernet device."""
    p = subprocess.Popen(["ethtool", "-e", device, "offset", "0x00", "length", "0x80"],
        stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    stdout, stderr = p.communicate()

    if p.returncode != 0:
        fail("Unable to execute ethtool: {}".format(stderr))

    bytearr = []

    for line in NEWLINES.split(stdout.decode('utf-8')):
        if ETHTOOL_BYTES.match(line):
            # we have a good line, stash all of its bytes in bytearr
            bytearr.extend(filter(lambda s: len(s.strip()) > 0, WHITESPACE.split(ETHTOOL_BYTES.match(line).group(1))))

    # convert them to integers
    return list(map(lambda s: int(s, 16), bytearr))


def fail(message, rc=1):
    """Emit a message to stderr and exit with a given return code."""
    sys.stderr.write("{}\n".format(message))
    sys.stderr.flush()
    sys.exit(rc)


def main():
    """Main entry point to the script."""
    parser = argparse.ArgumentParser(description="Validates an e1000e card's NVM checksum using ethtool.")
    parser.add_argument('device', help="The ethernet device name to validate.")
    args = parser.parse_args()

    byte_values = load_bytes(args.device)
    word_values = bytes_to_words(byte_values)
    checksum = hex(word_values[-1])

    if validate_checksum(word_values):
        print("SUCCESS: Your NVM Checksum is computed as equal to 0xbaba.")
    else:
        fail("FAILED: Your NVM Checksum for {} is invalid.".format(args.device))


if __name__ == "__main__":
    main()