netdev - Re: XDP_TX for virtio_net not working in recent kernel?

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Date:   Tue, 10 Apr 2018 12:17:15 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Kimitoshi Takahashi <ktaka@....ac.jp>
Cc:     xdp-newbies@...r.kernel.org, jasowang@...hat.com,
        netdev@...r.kernel.org
Subject: Re: XDP_TX for virtio_net not working in recent kernel?

[ +jason +netdev ]

On 04/10/2018 12:49 AM, Kimitoshi Takahashi wrote:
> Hello,
> 
> I'm totally newbie.
> 
> I want to try some examples under the samples/bpf of the kernel tree using the virtio_net driver in kvm, in order to get familiar with the XDP. However, it seems to me that for kernels newer than linux-4.15, the xdp2 and xdp_tx_tunnel are not working in the case of virtio_net.
> 
> Can somebody help me out to make them working?
> 
> 
> 1) For linux-4.11.12, linux-4.12.14, and linux-4.14.31, xdp2 and xdp_tx_tunnel are working.
> 
> [xdp2]
> 10.0.0.27# ./xdp2 2 (or ./xdp -N 2)
> 
> 10.0.0.254# hping3 10.0.0.27 -p 5000 -2
> 
> 10.0.0.254# tcpdump -nei kbr0 udp port 5000
> 06:18:37.677070 2e:c9:83:fb:5b:f3 > 52:54:00:11:00:1b, ethertype IPv4 (0x0800), length 42: 10.0.0.254.2982 > 10.0.0.27.5000: UDP, length 0
> 06:18:37.677265 52:54:00:11:00:1b > 2e:c9:83:fb:5b:f3, ethertype IPv4 (0x0800), length 42: 10.0.0.254.2982 > 10.0.0.27.5000: UDP, length 0
> 
> I can see the UDP packets with MAC addresses swapped.
> 
> [xdp_tx_tunnel]
> 
> 10.0.0.254# telnet 10.1.2.1 80
> 
> 10.0.0.27# ./xdp_tx_iptunnel -i 2 -a 10.1.2.1 -p 80 -s 10.0.0.27 -d 10.0.0.24 -m 52:54:00:11:00:18
> 
> 10.0.0.24# tcpdump -nei any proto 4
> 22:08:20.510354  In 52:54:00:11:00:1b ethertype IPv4 (0x0800), length 96: 10.0.0.27 > 10.0.0.24: 10.0.0.254.60826 > 10.1.2.1.80: Flags [S], seq 3224377720, win 29200, options [mss 1460,sackOK,TS val 217801953 ecr 0,nop,wscale 7], length 0 (ipip-proto-4)
> 
> I can see the encapsulated SYN packet that is forwarded by the 10.0.0.27.
> 
> 2) For linux-4.15, linux-4.15.5, linux-4.15.13 and linux-4.16.1, xdp2 and xdp_tx_tunnel are NOT working.
> 
> [xdp2]
> 10.0.0.27# ./xdp2 -N 2
> 
> 10.0.0.254# hping3 10.0.0.27 -p 5000 -2
> 
> 10.0.0.254# tcpdump -nei br0 udp port 5000
> 06:45:34.810046 2e:c9:83:fb:5b:f3 > 52:54:00:11:00:1b, ethertype IPv4 (0x0800), length 42: 10.0.0.254.2346 > 10.0.0.27.5000: UDP, length 0
> 06:45:35.810176 2e:c9:83:fb:5b:f3 > 52:54:00:11:00:1b, ethertype IPv4 (0x0800), length 42: 10.0.0.254.2347 > 10.0.0.27.5000: UDP, length 0
> 
> Only the outgoing packets can be seen.
> 
> [xdp_tx_tunnel]
> 
> 10.0.0.254# telnet 10.1.2.1 80
> 
> 10.0.0.27# ./xdp_tx_iptunnel -i 2 -a 10.1.2.1 -p 80 -s 10.0.0.27 -d 10.0.0.24 -m 52:54:00:11:00:18
> 
> 10.0.0.24# tcpdump -nei any proto 4
> 
> I can NOT see the encapsulated SYN packet that is forwarded by the 10.0.0.27.
> 
> 
> -- 
> Sincerely,
> Takahashi Kimitoshi