netdev - Re: [PATCH net-next v2 0/7] ipv4: Control SKB reprioritization after forwarding

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Date:   Wed, 01 Aug 2018 09:52:54 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     petrm@...lanox.com
Cc:     netdev@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kselftest@...r.kernel.org, corbet@....net, jiri@...lanox.com,
        idosch@...lanox.com, kuznet@....inr.ac.ru, yoshfuji@...ux-ipv6.org,
        shuah@...nel.org, nikolay@...ulusnetworks.com, dsahern@...il.com
Subject: Re: [PATCH net-next v2 0/7] ipv4: Control SKB reprioritization
 after forwarding

From: Petr Machata <petrm@...lanox.com>
Date: Wed, 01 Aug 2018 00:35:53 +0200

> After IPv4 packets are forwarded, the priority of the corresponding SKB
> is updated according to the TOS field of IPv4 header. This overrides any
> prioritization done earlier by e.g. an skbedit action or ingress-qos-map
> defined at a vlan device.
> 
> Such overriding may not always be desirable. Even if the packet ends up
> being routed, which implies this is an L3 network node, an administrator
> may wish to preserve whatever prioritization was done earlier on in the
> pipeline.
> 
> Therefore this patch set introduces a sysctl that controls this
> behavior, net.ipv4.ip_forward_update_priority. It's value is 1 by
> default to preserve the current behavior.
> 
> All of the above is implemented in patch #1.
> 
> Value changes prompt a new NETEVENT_IPV4_FWD_UPDATE_PRIORITY_UPDATE
> notification, so that the drivers can hook up whatever logic may depend
> on this value. That is implemented in patch #2.
> 
> In patches #3 and #4, mlxsw is adapted to recognize the sysctl. On
> initialization, the RGCR register that handles router configuration is
> set in accordance with the sysctl. The new notification is listened to
> and RGCR is reconfigured as necessary.
> 
> In patches #5 to #7, a selftest is added to verify that mlxsw reflects
> the sysctl value as necessary. The test is expressed in terms of the
> recently-introduced ieee_setapp support, and works by observing how DSCP
> value gets rewritten depending on packet priority. For this reason, the
> test is added to the subdirectory drivers/net/mlxsw. Even though it's
> not particularly specific to mlxsw, it's not suitable for running on
> soft devices (which don't support the ieee_setapp et.al.).
 ...

Series applied, thank you.