netdev - Re: [RFC PATCH net-next 12/15] ipv4: Add "in hardware" indication to routes

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Message-ID: <1eea9e93-dbd9-8b50-9bf1-f8f6c6842dcc@gmail.com>
Date:   Wed, 2 Oct 2019 20:34:22 -0600
From:   David Ahern <dsahern@...il.com>
To:     Jiri Pirko <jiri@...nulli.us>,
        Roopa Prabhu <roopa@...ulusnetworks.com>
Cc:     Ido Schimmel <idosch@...sch.org>, netdev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jiri Pirko <jiri@...lanox.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        mlxsw <mlxsw@...lanox.com>, Ido Schimmel <idosch@...lanox.com>
Subject: Re: [RFC PATCH net-next 12/15] ipv4: Add "in hardware" indication to
 routes

On 10/2/19 12:21 PM, Jiri Pirko wrote:
>>> This patch adds an "in hardware" indication to IPv4 routes, so that
>>> users will have better visibility into the offload process. In the
>>> future IPv6 will be extended with this indication as well.
>>>
>>> 'struct fib_alias' is extended with a new field that indicates if
>>> the route resides in hardware or not. Note that the new field is added
>>> in the 6 bytes hole and therefore the struct still fits in a single
>>> cache line [1].
>>>
>>> Capable drivers are expected to invoke fib_alias_in_hw_{set,clear}()
>>> with the route's key in order to set / clear the "in hardware
>>> indication".
>>>
>>> The new indication is dumped to user space via a new flag (i.e.,
>>> 'RTM_F_IN_HW') in the 'rtm_flags' field in the ancillary header.
>>>
>>
>> nice series Ido. why not call this RTM_F_OFFLOAD to keep it consistent
>> with the nexthop offload indication ?.
> 
> See the second paragraph of this description.

I read it multiple times. It does not explain why RTM_F_OFFLOAD is not
used. Unless there is good reason RTM_F_OFFLOAD should be the name for
consistency with all of the other OFFLOAD flags. I realize rtm_flags is
overloaded and the lower 8 bits contains RTNH_F flags, but that can be
managed with good documentation - that RTNH_F is for the nexthop and
RTM_F is for the prefix.