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?
