Re: [PATCH RFC 0/4] net: add bpfilter

On Mon, Feb 19, 2018 at 06:09:39PM +0100, Phil Sutter wrote:

What puzzles me about your argumentation is that you seem to propose for
the kernel to cover up flaws in userspace. Spinning this concept further
would mean that if there would be an old bug in iproute2 we should think
of adding a workaround to rtnetlink interface in kernel because
containers will keep the old iproute2 binary? Or am I (hopefully) just
missing your point?

Actually, that's what we already do. This is from rtnl_dump_ifinfo():

	/* A hack to preserve kernel<->userspace interface.
	 * The correct header is ifinfomsg. It is consistent with rtnl_getlink.
	 * However, before Linux v3.9 the code here assumed rtgenmsg and that's
	 * what iproute2 < v3.9.0 used.
	 * We can detect the old iproute2. Even including the IFLA_EXT_MASK
	 * attribute, its netlink message is shorter than struct ifinfomsg.
	 */

(There are, in fact, even current tools using rtgenmsg but that's
another story.)

Michal Kubecek