Re: [PATCH] inet_diag: fix reporting cgroup classid and fallback to priority

From: Konstantin Khlebnikov
Date: Wed Feb 13 2019 - 07:28:33 EST

On 12.02.2019 21:37, David Miller wrote:
From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Date: Sat, 09 Feb 2019 13:35:52 +0300

Field idiag_ext in struct inet_diag_req_v2 used as bitmap of requested
extensions has only 8 bits. Thus extensions starting from DCTCPINFO
cannot be requested directly. Some of them included into response
unconditionally or hook into some of lower 8 bits.

Extension INET_DIAG_CLASS_ID has not way to request from the beginning.

This patch bundle it with INET_DIAG_TCLASS (ipv6 tos), fixes space
reservation, and documents behavior for other extensions.

Also this patch adds fallback to reporting socket priority. This filed
is more widely used for traffic classification because ipv4 sockets
automatically maps TOS to priority and default qdisc pfifo_fast knows
about that. But priority could be changed via setsockopt SO_PRIORITY so
INET_DIAG_TOS isn't enough for predicting class.

Also cgroup2 obsoletes net_cls classid (it always zero), but we cannot
reuse this field for reporting cgroup2 id because it is 64-bit (ino+gen).

So, after this patch INET_DIAG_CLASS_ID will report socket priority
for most common setup when net_cls isn't set and/or cgroup2 in use.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Fixes: 0888e372c37f ("net: inet: diag: expose sockets cgroup classid")

Applied, and queued up for -stable.

Please always put the Fixes: tag first in the list of tags. I fixed
it up for you this time.

Ok. Never heard about that rule, doesn't complain about that too.