[ovs-dev] [PATCHv5] netdev-afxdp: Enable loading XDP program.

[William Tu]

On Thu, Dec 05, 2019 at 03:32:19PM +0100, Eelco Chaudron wrote:
> 
> 
> On 23 Nov 2019, at 1:26, William Tu wrote:
> 
> >Now netdev-afxdp always forwards all packets to userspace because
> >it is using libbpf's default XDP program, see 'xsk_load_xdp_prog'.
> >There are some cases when users want to keep packets in kernel instead
> >of sending to userspace, for example, management traffic such as SSH
> >should be processed in kernel.
> >
> >The patch enables loading the user-provided XDP program by
> >  $ovs-vsctl -- set int afxdp-p0 options:xdp-obj=<path/to/xdp/obj>
> >
> >So users can implement their filtering logic or traffic steering idea
> >in their XDP program, and rest of the traffic passes to AF_XDP socket
> >handled by OVS.
> 
> Did a quick test (no review) and found that we run into a repeat loop with
> best-effort mode:
> 
> 
> 2019-12-05T14:28:05.687Z|100465|bridge|WARN|could not open network device
> tapVM (No such device)
> 2019-12-05T14:28:05.688Z|100466|netdev_afxdp|ERR|best-effort mode and
> xdp-obj can't be set together
> 2019-12-05T14:28:05.688Z|100467|netdev|WARN|eno1: could not set
> configuration (Invalid argument)
> 2019-12-05T14:28:05.688Z|100468|netdev_afxdp|INFO|eno1: Removing xdp
> program.
> 2019-12-05T14:28:05.689Z|100469|netdev_afxdp|INFO|Removed XDP program ID: 0
> 2019-12-05T14:28:05.691Z|100470|bridge|WARN|could not open network device
> tapVM (No such device)
> 2019-12-05T14:28:05.692Z|100471|netdev_afxdp|ERR|best-effort mode and
> xdp-obj can't be set together
> 2019-12-05T14:28:05.692Z|100472|netdev|WARN|eno1: could not set
> configuration (Invalid argument)
> 2019-12-05T14:28:05.692Z|100473|netdev_afxdp|INFO|eno1: Removing xdp
> program.
> 2019-12-05T14:28:05.693Z|100474|netdev_afxdp|INFO|Removed XDP program ID: 0
> 2019-12-05T14:28:05.695Z|100475|bridge|WARN|could not open network device
> tapVM (No such device)
> 2019-12-05T14:28:05.696Z|100476|netdev_afxdp|ERR|best-effort mode and
> xdp-obj can't be set together
> 2019-12-05T14:28:05.696Z|100477|netdev|WARN|eno1: could not set
> configuration (Invalid argument)
> 2019-12-05T14:28:05.696Z|100478|netdev_afxdp|INFO|eno1: Removing xdp
> program.
> 2019-12-05T14:28:05.697Z|100479|netdev_afxdp|INFO|Removed XDP program ID: 0
> 2019-12-05T14:28:05.699Z|100480|bridge|WARN|could not open network device
> tapVM (No such device)
> 2019-12-05T14:28:05.700Z|100481|netdev_afxdp|ERR|best-effort mode and
> xdp-obj can't be set together
> 2019-12-05T14:28:05.700Z|100482|netdev|WARN|eno1: could not set
> configuration (Invalid argument)
> 2019-12-05T14:28:05.701Z|100483|netdev_afxdp|INFO|eno1: Removing xdp
> program.
> 
> Loop also happens when I configure a non existing object:
> 
> 2019-12-05T14:31:17.562Z|311021|netdev_afxdp|ERR|Invalid xdp-obj
> '/root/af_xdp_kernie.o': No such file or directory.
> 2019-12-05T14:31:17.562Z|311022|netdev|WARN|eno1: could not set
> configuration (Invalid argument)
> 2019-12-05T14:31:17.562Z|311023|netdev_afxdp|INFO|eno1: Removing xdp
> program.
> 2019-12-05T14:31:17.562Z|311024|netdev_afxdp|INFO|Removed XDP program ID: 0
> 2019-12-05T14:31:17.565Z|311025|bridge|WARN|could not open network device
> tapVM (No such device)
> 2019-12-05T14:31:17.566Z|311026|netdev_afxdp|ERR|Invalid xdp-obj
> '/root/af_xdp_kernie.o': No such file or directory.
> 2019-12-05T14:31:17.566Z|311027|netdev|WARN|eno1: could not set
> configuration (Invalid argument)
> 2019-12-05T14:31:17.566Z|311028|netdev_afxdp|INFO|eno1: Removing xdp
> program.
> 2019-12-05T14:31:17.566Z|311029|netdev_afxdp|INFO|Removed XDP program ID: 0
> 2019-12-05T14:31:17.569Z|311030|bridge|WARN|could not open network device
> tapVM (No such device)
> 2019-12-05T14:31:17.570Z|311031|netdev_afxdp|ERR|Invalid xdp-obj
> '/root/af_xdp_kernie.o': No such file or directory.
> 2019-12-05T14:31:17.570Z|311032|netdev|WARN|eno1: could not set
> configuration (Invalid argument)

Hi Eelco,

Thanks for reporting the infinite add/remove issue.
Ilya has a patch fixing it
[PATCH 2/3] netdev-afxdp: Avoid removing of XDP program if not loaded.

In short, the loop is
1) misconfigure netdev-afxdp
2) clean up xdp program using bpf_set_link_xdp_fd, (trigger if-notifier)
3) reconfigure --> goto step 1

Actually 2) is not necessary because xdp program is not loaded.

I will rebase on his fix and send newer version

Thanks
William