netdev - Re: [PATCH net-next 8/9] net: hns3: add support for queue bonding mode of flow director

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Message-ID: <20210317182828.70fcc61d@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 17 Mar 2021 18:28:28 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Huazhong Tan <tanhuazhong@...wei.com>,
        Alexander Duyck <alexander.duyck@...il.com>
Cc:     <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <salil.mehta@...wei.com>, <yisen.zhuang@...wei.com>,
        <huangdaode@...wei.com>, <linuxarm@...neuler.org>,
        <linuxarm@...wei.com>, Jian Shen <shenjian15@...wei.com>
Subject: Re: [PATCH net-next 8/9] net: hns3: add support for queue bonding
 mode of flow director

On Thu, 18 Mar 2021 09:02:54 +0800 Huazhong Tan wrote:
> On 2021/3/16 4:04, Jakub Kicinski wrote:
> > On Mon, 15 Mar 2021 20:23:50 +0800 Huazhong Tan wrote:  
> >> From: Jian Shen <shenjian15@...wei.com>
> >>
> >> For device version V3, it supports queue bonding, which can
> >> identify the tuple information of TCP stream, and create flow
> >> director rules automatically, in order to keep the tx and rx
> >> packets are in the same queue pair. The driver set FD_ADD
> >> field of TX BD for TCP SYN packet, and set FD_DEL filed for
> >> TCP FIN or RST packet. The hardware create or remove a fd rule
> >> according to the TX BD, and it also support to age-out a rule
> >> if not hit for a long time.
> >>
> >> The queue bonding mode is default to be disabled, and can be
> >> enabled/disabled with ethtool priv-flags command.  
> > This seems like fairly well defined behavior, IMHO we should have a full
> > device feature for it, rather than a private flag.  
> 
> Should we add a NETIF_F_NTUPLE_HW feature for it?

It'd be better to keep the configuration close to the existing RFS
config, no? Perhaps a new file under

  /sys/class/net/$dev/queues/rx-$id/

to enable the feature would be more appropriate?

Otherwise I'd call it something like NETIF_F_RFS_AUTO ?

Alex, any thoughts? IIRC Intel HW had a similar feature?

> > Does the device need to be able to parse the frame fully for this
> > mechanism to work? Will it work even if the TCP segment is encapsulated
> > in a custom tunnel?  
> 
> no, custom tunnel is not supported.

Hm, okay, it's just queue mapping, if device gets it wrong not the end
of the world (provided security boundaries are preserved).