def genlmsg_attrlen(gnlh, hdrlen):
return genlmsg_len(gnlh) - NLMSG_ALIGN(hdrlen)<EOL>
Return length of message attributes.

    https://github.com/thom311/libnl/blob/libnl3_2_25/lib/genl/genl.c#L302

    Positional arguments:
    gnlh -- Generic Netlink message header (genlmsghdr class instance).
    hdrlen -- length of user header (integer).

    Returns:
    Length of the message section containing attributes in number of bytes.