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

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Date:   Tue, 20 Feb 2018 10:35:41 +0100
From:   Michal Kubecek <mkubecek@...e.cz>
To:     Phil Sutter <phil@....cc>, David Miller <davem@...emloft.net>,
        laforge@...monks.org, fw@...len.de, daniel@...earbox.net,
        netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
        alexei.starovoitov@...il.com
Subject: 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