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

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Date:   Tue, 12 Feb 2019 15:03:40 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>
Cc:     Sasha Levin <sashal@...nel.org>, linux-sctp@...r.kernel.org
Subject: Re: [PATCH] inet_diag: fix reporting cgroup classid and fallback to
 priority



On 02/09/2019 02:35 AM, Konstantin Khlebnikov wrote:
> 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.
>

Nice catch Konstantin

Are you planing sending an iproute2/ss patch to output NET_DIAG_CLASS_ID values then ?

Thanks.