libbpf: Add a support for getting xdp prog id on ifindex

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.fijalkowski@intel.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 931be6f3408cf4d5bba49156377155f809802dbf..43c77e98df6f17f72b6f9fc2b2004a207509f069 100644 (file)
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -317,6 +317,7 @@ LIBBPF_API int bpf_prog_load(const char *file, enum bpf_prog_type type,
                             struct bpf_object **pobj, int *prog_fd);
 
 LIBBPF_API int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags);
+LIBBPF_API int bpf_get_link_xdp_id(int ifindex, __u32 *prog_id, __u32 flags);
 
 enum bpf_perf_event_ret {
        LIBBPF_PERF_EVENT_DONE  = 0,

diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 43ba9bb8d24b2acb433bdb93a39286b9cd8f7fc8..62c680fb13d1bc786a3880b47e37dd78e84ceeff 100644 (file)
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -132,4 +132,5 @@ LIBBPF_0.0.2 {
                bpf_probe_prog_type;
                bpf_map_lookup_elem_flags;
                bpf_object__find_map_fd_by_name;
+               bpf_get_link_xdp_id;
 } LIBBPF_0.0.1;

diff --git a/tools/lib/bpf/netlink.c b/tools/lib/bpf/netlink.c
index 0ce67aea8f3becd560fd4a11b6e51ddd9dac1563..ce3ec81b71c013d6b96c9037631a835f5013fb15 100644 (file)
--- a/tools/lib/bpf/netlink.c
+++ b/tools/lib/bpf/netlink.c
@@ -21,6 +21,12 @@
 typedef int (*__dump_nlmsg_t)(struct nlmsghdr *nlmsg, libbpf_dump_nlmsg_t,
                              void *cookie);
 
+struct xdp_id_md {
+       int ifindex;
+       __u32 flags;
+       __u32 id;
+};
+
 int libbpf_netlink_open(__u32 *nl_pid)
 {
        struct sockaddr_nl sa;
@@ -196,6 +202,85 @@ static int __dump_link_nlmsg(struct nlmsghdr *nlh,
        return dump_link_nlmsg(cookie, ifi, tb);
 }
 
+static unsigned char get_xdp_id_attr(unsigned char mode, __u32 flags)
+{
+       if (mode != XDP_ATTACHED_MULTI)
+               return IFLA_XDP_PROG_ID;
+       if (flags & XDP_FLAGS_DRV_MODE)
+               return IFLA_XDP_DRV_PROG_ID;
+       if (flags & XDP_FLAGS_HW_MODE)
+               return IFLA_XDP_HW_PROG_ID;
+       if (flags & XDP_FLAGS_SKB_MODE)
+               return IFLA_XDP_SKB_PROG_ID;
+
+       return IFLA_XDP_UNSPEC;
+}
+
+static int get_xdp_id(void *cookie, void *msg, struct nlattr **tb)
+{
+       struct nlattr *xdp_tb[IFLA_XDP_MAX + 1];
+       struct xdp_id_md *xdp_id = cookie;
+       struct ifinfomsg *ifinfo = msg;
+       unsigned char mode, xdp_attr;
+       int ret;
+
+       if (xdp_id->ifindex && xdp_id->ifindex != ifinfo->ifi_index)
+               return 0;
+
+       if (!tb[IFLA_XDP])
+               return 0;
+
+       ret = libbpf_nla_parse_nested(xdp_tb, IFLA_XDP_MAX, tb[IFLA_XDP], NULL);
+       if (ret)
+               return ret;
+
+       if (!xdp_tb[IFLA_XDP_ATTACHED])
+               return 0;
+
+       mode = libbpf_nla_getattr_u8(xdp_tb[IFLA_XDP_ATTACHED]);
+       if (mode == XDP_ATTACHED_NONE)
+               return 0;
+
+       xdp_attr = get_xdp_id_attr(mode, xdp_id->flags);
+       if (!xdp_attr || !xdp_tb[xdp_attr])
+               return 0;
+
+       xdp_id->id = libbpf_nla_getattr_u32(xdp_tb[xdp_attr]);
+
+       return 0;
+}
+
+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;
+}
+
 int libbpf_nl_get_link(int sock, unsigned int nl_pid,
                       libbpf_dump_nlmsg_t dump_link_nlmsg, void *cookie)
 {