[ovs-discuss] Why OVS behaves difference between ovs-vswitchd and ovs-vswitchd-dpdk?

Mon Jun 7 10:47:16 UTC 2021

> 2021年6月4日 下午11:21，Ben Pfaff <blp at ovn.org> 写道：
> 
> On Fri, Jun 04, 2021 at 02:11:23PM +0800, Harry Lee wrote:
>> Hello,
>> 
>> My server is running debian testing. I install two ovs version through apt:
>> 
>> ```
>> openvswitch-switch/testing,unstable,now 2.15.0+ds1-2 amd64 [installed]
>>  Open vSwitch switch implementations
>> 
>> openvswitch-switch-dpdk/testing,unstable,now 2.15.0+ds1-2 amd64 [installed]
>>  DPDK enabled Open vSwitch switch implementation
>> ```
>> 
>> Then I found something  difference between them.
>> 
>> Here's my experience:
>> 
>> ```
>> # switch ovs version to ovs-vswitchd
>> update-alternatives --set ovs-vswitchd /usr/lib/openvswitch-common/ovs-vswitchd
>> /etc/init.d/openvswitch-switch restart
>> ip addr add 10.90.67.148/25 dev br0
>> ping 10.90.67.129  # network is ok
>> 
>> # switch ovs version to ovs-vswitchd-dpdk
>> update-alternatives --set ovs-vswitchd /usr/lib/openvswitch-switch-dpdk/ovs-vswitchd-dpdk
>> /etc/init.d/openvswitch-switch restart
>> ip addr add 10.90.67.148/25 dev br0
>> ping 10.90.67.129  # unreachable
>> ```
>> 
>> The same configuration, using ovs-vswitchd was reachable while using ovs-vswitchd-dpdk was unreachable.
>> 
>> Then I used `tcpdump br0` to checkout if there are packets from br0, and I found some ARP packets:
>> 
>> ```
>> root at debian:~# tcpdump -i br0 -nnn
>> tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
>> listening on br0, link-type EN10MB (Ethernet), snapshot length 262144 bytes
>> 02:14:27.010265 ARP, Request who-has 10.90.67.129 tell 10.90.67.148, length 28
>> 02:14:28.034127 ARP, Request who-has 10.90.67.129 tell 10.90.67.148, length 28
>> 02:14:29.058128 ARP, Request who-has 10.90.67.129 tell 10.90.67.148, length 28
>> ```
>> 
>> But when I ran `ovs-ofctl dump-flows br0`, I saw n_packets is 0:
>> 
>> ```
>> root at debian:~# ovs-ofctl dump-flows br0
>> cookie=0x0, duration=1016.243s, table=0, n_packets=0, n_bytes=0, priority=0 actions=NORMAL
>> ```
>> 
>> Why does ovs-vswitchd-dpdk ignore the packet from br0? Does it need additional configuration?
> 
> Did you configure the dpdk version to use DPDK devices and the userspace
> datapath?  If you didn't, then these two versions of OVS were using the
> same code in the same way, so it's puzzling why there would have been
> any difference.

Did you mean `ovs-vsctl --no-wait set Open_vSwitch . other_config:dpdk-init=false` ?

I had set it to false and restart, but no matter I set it true or set it false, the results were the same.

By the way, I found some warning in log:

Also some logs in dmesg:

```
[321931.322617] openvswitch: netlink: Flow key attr not present in new flow.
[321931.322691] openvswitch: netlink: Flow key attr not present in new flow.
[321931.323034] openvswitch: netlink: Flow key attr not present in new flow.
[321931.323118] openvswitch: netlink: Flow key attr not present in new flow.
```