netdev - Re: Virtio_net support vxlan encapsulation package TSO offload discuss

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Date:   Tue, 8 Nov 2016 11:58:26 +0000
From:   "Zhangming (James, Euler)" <james.zhangming@...wei.com>
To:     Jason Wang <jasowang@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "Michael S. Tsirkin" <mst@...hat.com>,
        Vlad Yasevic <vyasevic@...hat.com>
Subject: Re: Virtio_net support vxlan encapsulation package TSO offload
 discuss

On 2016年11月08日 19:17, Jason Wang wrote:

>On 2016年11月08日 19:13, Jason Wang wrote:
>> Cc Michael
>>
>> On 2016年11月08日 16:34, Zhangming (James, Euler) wrote:
>>>
>>> In container scenario, OVS is installed in the Virtual machine, and 
>>> all the containers connected to the OVS will communicated through 
>>> VXLAN encapsulation.
>>>
>>> By now, virtio_net does not support TSO offload for VXLAN 
>>> encapsulated TSO package. In this condition, the performance is not 
>>> good, sender is bottleneck
>>>
>>> I googled this scenario, but I didn’t find any information. Will 
>>> virtio_net support VXLAN encapsulation package TSO offload later?
>>>
>>
> >Yes and for both sender and receiver.
>>
>>> My idea is virtio_net open encapsulated TSO offload, and transport 
>>> encapsulation info to TUN, TUN will parse the info and build skb with 
>>> encapsulation info.
>>>
>>> OVS or kernel on the host should be modified to support this. Using 
>>> this method, the TCP performance aremore than 2x as before.
>>>
>>> Any advice and suggestions for this idea or new idea will be greatly 
>>> appreciated!
>>>
>>> Best regards,
>>>
>>>    James zhang
>>>
>>
>> Sounds very good. And we may also need features bits
>> (VIRTIO_NET_F_GUEST|HOST_GSO_X) for this.
>>
>> This is in fact one of items in networking todo list. (See 
>> http://www.linux-kvm.org/page/NetworkingTodo). While at it, we'd 
>> better support not only VXLAN but also other tunnels.
>
>Cc Vlad who is working on extending virtio-net headers.
>
>>
>> We can start with the spec work, or if you've already had some bits 
>> you can post them as RFC for early review.
>>
>> Thanks

Below is my demo code
Virtio_net.c
static int virtnet_probe(struct virtio_device *vdev), add belows codes:
        if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF) ||				// avoid gso segment, it should be negotiation later, because in the demo I reuse num_buffers.
            virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) {
                dev->hw_enc_features |= NETIF_F_TSO;
                dev->hw_enc_features |= NETIF_F_ALL_CSUM;
                dev->hw_enc_features |= NETIF_F_GSO_UDP_TUNNEL;
                dev->hw_enc_features |= NETIF_F_GSO_UDP_TUNNEL_CSUM;
                dev->hw_enc_features |= NETIF_F_GSO_TUNNEL_REMCSUM;

                dev->features |= NETIF_F_GSO_UDP_TUNNEL;
                dev->features |= NETIF_F_GSO_UDP_TUNNEL_CSUM;
                dev->features |= NETIF_F_GSO_TUNNEL_REMCSUM;
        }

static int xmit_skb(struct send_queue *sq, struct sk_buff *skb), add below to pieces of codes

                if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL)
                        hdr->hdr.gso_type |= VIRTIO_NET_HDR_GSO_TUNNEL;
                if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL_CSUM)
                        hdr->hdr.gso_type |= VIRTIO_NET_HDR_GSO_TUNNEL_CSUM;
                if (skb_shinfo(skb)->gso_type & SKB_GSO_TUNNEL_REMCSUM)
                        hdr->hdr.gso_type |= VIRTIO_NET_HDR_GSO_TUNNEL_REMCSUM;

        if (skb->encapsulation && skb_is_gso(skb)) {
                inner_mac_len = skb_inner_network_header(skb) - skb_inner_mac_header(skb);
                tnl_len = skb_inner_mac_header(skb) - skb_mac_header(skb);
                if ( !(inner_mac_len >> DATA_LEN_SHIFT) && !(tnl_len >> DATA_LEN_SHIFT) ) {
                        hdr->hdr.flags |= VIRTIO_NET_HDR_F_ENCAPSULATION;
                        hdr->num_buffers = (__virtio16)((inner_mac_len << DATA_LEN_SHIFT) | tnl_len);		//we reuse num_buffers for simple , we should add extend member for later.
                }  else
                        hdr->num_buffers = 0;
        }

Tun.c 
                if (memcpy_fromiovecend((void *)&hdr, iv, offset, tun->vnet_hdr_sz))		//read header with negotiation length
                        return -EFAULT;

                if (hdr.gso_type & VIRTIO_NET_HDR_GSO_TUNNEL)					//set tunnel gso info
                        skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL;
                if (hdr.gso_type & VIRTIO_NET_HDR_GSO_TUNNEL_CSUM)
                        skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL_CSUM;
                if (hdr.gso_type & VIRTIO_NET_HDR_GSO_TUNNEL_REMCSUM)
                        skb_shinfo(skb)->gso_type |= SKB_GSO_TUNNEL_REMCSUM;

        if (hdr.flags & VIRTIO_NET_HDR_F_ENCAPSULATION) {						//read tunnel info from header and set to built skb.
                tnl_len = tun16_to_cpu(tun, hdr.num_buffers) & TUN_TNL_LEN_MASK;
                payload_mac_len = tun16_to_cpu(tun, hdr.num_buffers) >> TUN_DATA_LEN_SHIFT;
                mac_len = skb_network_header(skb) - skb_mac_header(skb);
                skb_set_inner_mac_header(skb, tnl_len - mac_len);
                skb_set_inner_network_header(skb, tnl_len + payload_mac_len - mac_len);
                skb->encapsulation = 1;
        }