netdev - Re: [PATCH 0/3] Add NETIF_F_HW

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Date:   Sat, 24 Aug 2019 09:42:05 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Horatiu Vultur <horatiu.vultur@...rochip.com>,
        roopa@...ulusnetworks.com, nikolay@...ulusnetworks.com,
        davem@...emloft.net, UNGLinuxDriver@...rochip.com,
        alexandre.belloni@...tlin.com, allan.nielsen@...rochip.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        bridge@...ts.linux-foundation.org
Subject: Re: [PATCH 0/3] Add NETIF_F_HW_BRIDGE feature

Sat, Aug 24, 2019 at 01:25:02AM CEST, f.fainelli@...il.com wrote:
>On 8/22/19 12:07 PM, Horatiu Vultur wrote:
>> Current implementation of the SW bridge is setting the interfaces in
>> promisc mode when they are added to bridge if learning of the frames is
>> enabled.
>> In case of Ocelot which has HW capabilities to switch frames, it is not
>> needed to set the ports in promisc mode because the HW already capable of
>> doing that. Therefore add NETIF_F_HW_BRIDGE feature to indicate that the
>> HW has bridge capabilities. Therefore the SW bridge doesn't need to set
>> the ports in promisc mode to do the switching.
>
>Then do not do anything when the ndo_set_rx_mode() for the ocelot
>network device is called and indicates that IFF_PROMISC is set and that
>your network port is a bridge port member. That is what mlxsw does AFAICT.

Correct.

>
>As other pointed out, the Linux bridge implements a software bridge by
>default, and because it needs to operate on a wide variety of network
>devices, all with different capabilities, the easiest way to make sure
>that all management (IGMP, BPDU, etc. ) as well as non-management
>traffic can make it to the bridge ports, is to put the network devices
>in promiscuous mode. If this is suboptimal for you, you can take
>shortcuts in your driver that do not hinder the overall functionality.
>
>> This optimization takes places only if all the interfaces that are part
>> of the bridge have this flag and have the same network driver.
>> 
>> If the bridge interfaces is added in promisc mode then also the ports part
>> of the bridge are set in promisc mode.
>> 
>> Horatiu Vultur (3):
>>   net: Add HW_BRIDGE offload feature
>>   net: mscc: Use NETIF_F_HW_BRIDGE
>>   net: mscc: Implement promisc mode.
>> 
>>  drivers/net/ethernet/mscc/ocelot.c | 26 ++++++++++++++++++++++++--
>>  include/linux/netdev_features.h    |  3 +++
>>  net/bridge/br_if.c                 | 29 ++++++++++++++++++++++++++++-
>>  net/core/ethtool.c                 |  1 +
>>  4 files changed, 56 insertions(+), 3 deletions(-)
>> 
>
>
>-- 
>Florian