On 02/01/2019 10:47 PM, Jakub Kicinski wrote:
> On Fri, 1 Feb 2019 22:43:39 +0100, Daniel Borkmann wrote:
>> On 02/01/2019 01:19 AM, Maciej Fijalkowski wrote:
>>> Since we have a dedicated netlink attributes for xdp setup on a
>>> particular interface, it is now possible to retrieve the program id that
>>> is currently attached to the interface. The use case is targeted for
>>> sample xdp programs, which will store the program id just after loading
>>> bpf program onto iface. On shutdown, the sample will make sure that it
>>> can unload the program by querying again the iface and verifying that
>>> both program id's matches.
>>>
>>> Signed-off-by: Maciej Fijalkowski <maciej.fijalkow...@intel.com>
>>> Reviewed-by: Jakub Kicinski <jakub.kicin...@netronome.com>
>> [...]
>>> +int bpf_get_link_xdp_id(int ifindex, __u32 *prog_id, __u32 flags)
>>> +{
>>> + struct xdp_id_md xdp_id = {};
>>> + int sock, ret;
>>> + __u32 nl_pid;
>>> + __u32 mask;
>>> +
>>> + if (flags & ~XDP_FLAGS_MASK)
>>> + return -EINVAL;
>>> +
>>> + /* Check whether the single {HW,DRV,SKB} mode is set */
>>> + flags &= (XDP_FLAGS_SKB_MODE | XDP_FLAGS_DRV_MODE | XDP_FLAGS_HW_MODE);
>>> + mask = flags - 1;
>>> + if (flags && flags & mask)
>>> + return -EINVAL;
>>> +
>>> + sock = libbpf_netlink_open(&nl_pid);
>>> + if (sock < 0)
>>> + return sock;
>>> +
>>> + xdp_id.ifindex = ifindex;
>>> + xdp_id.flags = flags;
>>> +
>>> + ret = libbpf_nl_get_link(sock, nl_pid, get_xdp_id, &xdp_id);
>>> + if (!ret)
>>> + *prog_id = xdp_id.id;
>>> +
>>> + close(sock);
>>> + return ret;
>>> +}
>>
>> Btw, is anyone going to follow-up on XDP_ATTACHED_MULTI support as well
>> later on?
>
> I haven't tested to be honest, but I think Maciek got that right -
> get_xdp_id_attr() should return IFLA_XDP_PROG_ID or a mode-specific
> attr based on flags. And there is a check that only flag is set.
>
> Or do you mean retrieving all program ids with one dump?
Yeah was thinking about the latter, but agree it's fine and probably
cleaner this way here.
