[PATCH bpf-next v5 5/8] xdp: Provide extack messages when prog attachment failed

[Maciej Fijalkowski]

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.kicin...@netronome.com>
Signed-off-by: Maciej Fijalkowski <maciej.fijalkow...@intel.com>
---
 net/core/dev.c | 12 +++++++++---
 1 file 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);
-- 
2.16.1