netdev - Re: [PATCH net-next v11 1/4] net netlink: Add new type NLA_BITFIELD

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Message-ID: <5a568b1f-a311-f97b-f5d0-5361b33cf6bc@gmail.com>
Date:   Fri, 28 Jul 2017 09:13:22 -0600
From:   David Ahern <dsahern@...il.com>
To:     Jamal Hadi Salim <jhs@...atatu.com>, davem@...emloft.net
Cc:     netdev@...r.kernel.org, jiri@...nulli.us, xiyou.wangcong@...il.com,
        eric.dumazet@...il.com, mrv@...atatu.com,
        simon.horman@...ronome.com, alex.aring@...il.com
Subject: Re: [PATCH net-next v11 1/4] net netlink: Add new type
 NLA_BITFIELD_32

On 7/28/17 9:04 AM, Jamal Hadi Salim wrote:
> 
> Kernel side checking for device ifindex must know what a device
> ifindex means.
> That doesnt disqualify that the generic code checks that it
> is of the same size as a signed 32b, etc. That is generic
> stuff that can be factored out.
> 
> In this case:
> Checking for whether bits selected are in the allowed range
> that the kernel understands, that the bit value are set in
> the right bit position, that the bits set in the correct bit
> value position are also selected in the transaction.
> That is generic code (which the content validation does).

Create a helper function then. It's the validation of attribute content
in 2 places that I object to. 1 attribute is validated in 1 place
(generic infra for this bitfield attribute), the others are validated in
line. Asymmetric validations is not a good design.