[ovs-discuss] [dpdk-ovs] dpdkvhost port not handling arp response from kvm guest

[Loftus, Ciara]

> Hi,
> 
> I would like to bring up my kvm guest with dpdk vhost interface. Before
> I run qemu, I have added
> dpdkvhost interface in ovs bridge, so as to attach with qemu later (wrt
> INSTALL.DPDK.md).
> 
> Once I created dpdkvhost interface, I noticed that dpdkvhost0 was in
> LINK_DOWN (I think it is
> expected as the device does not exist yet).
Correct.

> 
> ovs-master# ovs-vsctl add-port br0 dpdkvhost0 -- set Interface
> dpdkvhost0 type=dpdkvhost
> 
> ovs-master# ovs-ofctl show br0
> 
> OFPT_FEATURES_REPLY (xid=0x2): dpid:000090e2ba1524ac
> n_tables:254, n_buffers:256
> capabilities: FLOW_STATS TABLE_STATS PORT_STATS QUEUE_STATS
> ARP_MATCH_IP
> actions: output enqueue set_vlan_vid set_vlan_pcp strip_vlan mod_dl_src
> mod_dl_dst mod_nw_src mod_nw_dst mod_nw_tos mod_tp_src
> mod_tp_dst
>   1(dpdk0): addr:90:e2:ba:15:24:ac
>       config:     0
>       state:      0
>       current:    10GB-FD
>       supported:  10MB-HD 100MB-HD 1GB-HD COPPER AUTO_NEG
> AUTO_PAUSE
>       speed: 10000 Mbps now, 1000 Mbps max
>   2(dpdkvhost0): addr:00:00:00:00:00:00
>       config:     PORT_DOWN
>       state:      LINK_DOWN                 <<<<<<
>       speed: 0 Mbps now, 0 Mbps max
>   LOCAL(br0): addr:90:e2:ba:15:24:ac
>       config:     0
>       state:      0
>       current:    10MB-FD COPPER
>       speed: 10 Mbps now, 0 Mbps max
> 
>  From ovs-vswitchd.log (with debug info):
> 
> 2015-06-02T14:49:38.149Z|00464|bridge|INFO|bridge br0: added interface
> dpdkvhost0 on port 2
> 2015-06-
> 02T14:49:38.149Z|00465|netlink_socket|DBG|nl_sock_transact_multiple__
> (Success): nl(len:52, type=37(family-defined), flags=1[REQUEST], seq=1a,
> pid=4294962434
> 2015-06-02T14:49:38.149Z|00466|netlink_socket|DBG|nl_sock_recv__
> (Success): nl(len:72, type=2(error), flags=0, seq=1a, pid=4294962434
> error(-2(No such file or directory), in-reply-to(nl(len:52,
> type=37(family-defined), flags=1[REQUEST], seq=1a, pid=4294962434))
> 2015-06-02T14:49:38.149Z|00467|netlink_socket|DBG|received NAK error=0
> (No such file or directory)
> 
> Then I brought up qemu kvm, but still the state of dpdkvhost0 remains
> same. Networking params I used in qemu are:
LINK_DOWN here is still normal behaviour. Since you can see the ARP request on the port, it is safe to assume the port is up.

> 
>       -netdev
> tap,id=hostnet2,script=no,downscript=no,ifname=dpdkvhost0,vhost=on
>       -device
> virtio-net-
> pci,netdev=hostnet2,csum=off,gso=off,guest_tso4=off,guest_tso6=off,gues
> t_ecn=off,id=net2,mac=52:54:00:a3:a3:5d,ioeventfd=on
> 
>       -object
> memory-backend-file,id=mem,size=4096M,mem-
> path=/dev/hugepages,share=on
> -numa node,memdev=mem -mem-prealloc
> 
> Am I missing something here ?
These parameters look ok, although I'm not sure if the ioeventfd=on parameter is needed.

> 
> dpdk0 port is Intel 82599 10Gbps NIC bound on igb_uio driver. VM could
> recieve arp req from remote system (on dpdk0 port), but VM's arp
> response does not seem to cross ovs.
> I did not see any arp response reportedly logged by vswitchd even with
> debug info turned on, or may be that ovs is dropping them internally ?.
> Or, Should dpdkvhost0 be internal port (tap) here for ovs to handle arp
> response from VM ?
This shouldn't be necessary.

> 
> from ovs-ofctl dump-flows:
> NXST_FLOW reply (xid=0x4):
>   cookie=0x0, duration=47.090s, table=0, n_packets=59, n_bytes=3741,
> idle_age=1, in_port=1 actions=output:2
>   cookie=0x0, duration=42.129s, table=0, n_packets=0, n_bytes=0,
> idle_age=42, in_port=2 actions=output:1
> 
> This is blocking the connection to get established with VM (from remote
> system talking through dpdk0).
> 
> My env info:
> Ubuntu 14.10
> ovs-vsctl (Open vSwitch) 2.3.90
> Compiled May 19 2015 04:27:58
> DB Schema 7.12.1
> dpdk-2.0.0
> 
> Any help/pointer to further diagnose is greatly appreciated.

I've created a similar setup on a Fedora system and I unfortunately I cannot reproduce. I have one bridge, with 1 x dpdkport and 1 x dpdkvhost port, and the same flows; in_port=1,output:2 & in_port=2,output:1
I'm using a traffic generator to simulate the ARP request.
On my guest, I bring up the dpdkvhost Ethernet device, assign it an IP address, and "arp -s <IP of sender of ARP req> <MAC of sender of ARP req>"
When I send the ARP req, I see the response going through the switch and back to the traffic generator.

Potentially there is an issue with your OS, I had a quick look and found a post in the discuss archive about a potential problem with Debian/Ubuntu systems and how they handle ARP packets with OVS: http://openvswitch.org/pipermail/discuss/2012-May/007348.html
It is quite old however so I'm not sure if the issue still exists, or if this is relevant to your set up.

> 
> --
> Regards,
> Gowrishankar M