linux-kernel - Re: Re: [PATCH bpf-next] netkit: Add some ethtool ops to provide information to user

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Message-ID: <bb6c65de-1788-46a4-b913-5b1afa9c5cd7@bytedance.com>
Date:   Thu, 7 Dec 2023 17:56:52 +0800
From:   Feng Zhou <zhoufeng.zf@...edance.com>
To:     Daniel Borkmann <daniel@...earbox.net>,
        Nikolay Aleksandrov <razor@...ckwall.org>, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, yangzhenze@...edance.com,
        wangdongdong.6@...edance.com, tangchen.1@...edance.com
Subject: Re: Re: [PATCH bpf-next] netkit: Add some ethtool ops to provide
 information to user

在 2023/12/6 18:57, Daniel Borkmann 写道:
> On 12/6/23 7:59 AM, Feng Zhou wrote:
>> 在 2023/12/4 23:22, Daniel Borkmann 写道:
>>> Thanks, so the netkit_get_link_ksettings is optional. 
>>
>> Yes, netkit_get_link_ksettings really not necessary, I just added it 
>> in line with veth.
>>
>> I don't quite
>>> follow what you
>>> mean with regards to your business logic in veth to obtain peer 
>>> ifindex. What does
>>> the script do exactly with the peer ifindex (aka /why/ is it needed), 
>>> could you
>>> elaborate some more - it's still somewhat too vague? 🙂 E.g. why it 
>>> does not suffice
>>> to look at the device type or other kind of attributes?
>>
>> The scripting logic of the business colleagues should just be simple 
>> logging records, using ethtool. Then they saw that netkit has this 
>> missing, so raised this requirement, so I sent this patch, wanting to 
>> hear your opinions. If you don't think it's necessary, let the 
>> business colleagues modify it.
> 
> So it is basically only logging the peer_ifindex data from ethtool but 
> nothing
> more is done with it? Meaning, this was raised as a requirement because 
> this was
> missing from the logging data, or was there anything more to it?
> 
> The peer ifindex is already available via IFLA_LINK (which does 
> dev_get_iflink()
> internally to fetch the peer's ifindex). This is also what you see in 
> iproute2:
> 
> # ip l
> [...]
> 163: nk0@nk1: <BROADCAST,MULTICAST,NOARP,M-DOWN> mtu 1500 qdisc noop 
> state DOWN group default qlen 1000
>      link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
> 164: nk1@nk0: <BROADCAST,MULTICAST,NOARP,M-DOWN> mtu 1500 qdisc noop 
> state DOWN group default qlen 1000
>      link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
> [...]
> # ip netns add blue
> # ip link set nk1 netns blue
> # ip l
> [...]
> 163: nk0@...64: <BROADCAST,MULTICAST,NOARP> mtu 1500 qdisc noop state 
> DOWN group default qlen 1000
>      link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff link-netns blue
> [...]
> 
> The `if164` denotes the peer's ifindex and `link-netns blue` provides 
> info on the netns of the peer.
> This is much better and more generic than the ethtool hack. I would 
> suggest changing the logic to
> rather look at data populated by rtnl_fill_link_netnsid() instead.
> 
> Thanks,
> Daniel

Yes, if veth supports ethtool -S to get the function of peer's ifindex, 
it is not necessary for netkit and can be replaced by other ways.