netdev - Re: [PATCH net] sch_cake: Interpret fwmark parameter as a bitmask

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Message-Id: <20190315.115738.147858309937637.davem@davemloft.net>
Date:   Fri, 15 Mar 2019 11:57:38 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     toke@...hat.com
Cc:     netdev@...r.kernel.org, cake@...ts.bufferbloat.net, fuller@...f.de
Subject: Re: [PATCH net] sch_cake: Interpret fwmark parameter as a bitmask

From: Toke Høiland-Jørgensen <toke@...hat.com>
Date: Thu, 14 Mar 2019 23:08:22 +0100

> We initially interpreted the fwmark parameter as a flag that simply turned
> on the feature, using the whole skb->mark field as the index into the CAKE
> tin_order array. However, it is quite common for different applications to
> use different parts of the mask field for their own purposes, each using a
> different mask.
> 
> Support this use of subsets of the mark by interpreting the TCA_CAKE_FWMARK
> parameter as a bitmask to apply to the fwmark field when reading it. The
> result will be right-shifted by the number of unset lower bits of the mask
> before looking up the tin.
> 
> In the original commit message we also failed to credit Felix Resch with
> originally suggesting the fwmark feature back in 2017; so the Suggested-By
> in this commit covers the whole fwmark feature.
> 
> Fixes: 0b5c7efdfc6e ("sch_cake: Permit use of connmarks as tin classifiers")
> Suggested-by: Felix Resch <fuller@...f.de>
> Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>

You are lucky you decided to do this before a released kernel had this UAPI
available.

Applied.