Re: [PATCH net-next v4 2/3] virtio_net: add optional flow dissection in virtio_net_hdr_to_skb

From: Jason Wang <jasowang@redhat.com>
To: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	Tanner Love <tannerlove.kernel@gmail.com>,
	Network Development <netdev@vger.kernel.org>,
	David Miller <davem@davemloft.net>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Eric Dumazet <edumazet@google.com>,
	Petar Penkov <ppenkov@google.com>,
	Jakub Kicinski <kuba@kernel.org>,
	"Michael S . Tsirkin" <mst@redhat.com>,
	Tanner Love <tannerlove@google.com>
Subject: Re: [PATCH net-next v4 2/3] virtio_net: add optional flow dissection in virtio_net_hdr_to_skb
Date: Tue, 22 Jun 2021 10:37:33 +0800	[thread overview]
Message-ID: <67aa8472-bb3d-8186-35f1-ec6682fa8602@redhat.com> (raw)
In-Reply-To: <CA+FuTSekbW9PG_QbA2T6tG6Go2-CGRn9gYyJWUY38Nqz6EqaoA@mail.gmail.com>

在 2021/6/21 下午9:18, Willem de Bruijn 写道:
>>>> 2) use some general fields instead of virtio-net specific fields, e.g
>>>> using device header instead of vnet header in the flow keys strcuture
>>> Can you give an example of what would be in the device header?
>>>
>>> Specific for GSO, we have two sets of constants: VIRTIO_NET_HDR_GSO_..
>>> and SKB_GSO_.. Is the suggestion to replace the current use of the
>>> first in field flow_keys->virtio_net_hdr.gso_type with the second in
>>> flow_keys->gso_type?
>>
>> No, I meant using a general fields like flow_keys->device_hdr. And use
>> bpf helpers to access the field.
> What would be in this device_hdr field, and what would the bpf helpers
> access? I don't fully follow what this is if not vnet_hdr.

For virtio-net, it should be just vnet_hdr. Maybe "device_hdr" is not 
accurate, "packet_hdr" should be better.

This allows the field to be reused by other type of userspace injected 
packet, like tun packet info.

Bpf helpers could be used to access the packet header in this case.

Thanks

>