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

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Message-ID: <20191003054053.GI2279@nanopsycho>
Date:   Thu, 3 Oct 2019 07:40:53 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     David Ahern <dsahern@...il.com>
Cc:     Roopa Prabhu <roopa@...ulusnetworks.com>,
        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

Thu, Oct 03, 2019 at 04:34:22AM CEST, dsahern@...il.com wrote:
>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.

"In addition, the fact that a route resides in hardware does
not necessarily mean that the traffic is offloaded."