xdp: Provide extack messages when prog attachment failed

In order to provide more meaningful messages to user when the process of
loading xdp program onto network interface failed, let's add extack
messages within dev_change_xdp_fd.

Suggested-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 9 insertions, 3 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 8e276e0192a1..bfa4be42afff 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -7983,8 +7983,10 @@ int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
         query = flags & XDP_FLAGS_HW_MODE ? XDP_QUERY_PROG_HW : XDP_QUERY_PROG;
 
         bpf_op = bpf_chk = ops->ndo_bpf;
-        if (!bpf_op && (flags & (XDP_FLAGS_DRV_MODE | XDP_FLAGS_HW_MODE)))
+        if (!bpf_op && (flags & (XDP_FLAGS_DRV_MODE | XDP_FLAGS_HW_MODE))) {
+                NL_SET_ERR_MSG(extack, "underlying driver does not support XDP in native mode");
                 return -EOPNOTSUPP;
+        }
         if (!bpf_op || (flags & XDP_FLAGS_SKB_MODE))
                 bpf_op = generic_xdp_install;
         if (bpf_op == bpf_chk)
@@ -7992,11 +7994,15 @@ int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
 
         if (fd >= 0) {
                 if (__dev_xdp_query(dev, bpf_chk, XDP_QUERY_PROG) ||
-                    __dev_xdp_query(dev, bpf_chk, XDP_QUERY_PROG_HW))
+                    __dev_xdp_query(dev, bpf_chk, XDP_QUERY_PROG_HW)) {
+                        NL_SET_ERR_MSG(extack, "native and generic XDP can't be active at the same time");
                         return -EEXIST;
+                }
                 if ((flags & XDP_FLAGS_UPDATE_IF_NOEXIST) &&
-                    __dev_xdp_query(dev, bpf_op, query))
+                    __dev_xdp_query(dev, bpf_op, query)) {
+                        NL_SET_ERR_MSG(extack, "XDP program already attached");
                         return -EBUSY;
+                }
 
                 prog = bpf_prog_get_type_dev(fd, BPF_PROG_TYPE_XDP,
                                              bpf_op == ops->ndo_bpf);