net: make vlan_get_tag() return -ENODATA instead of -EINVAL

__vlan_hwaccel_get_tag() is used in veth XDP hints implementation,
its return value (-EINVAL if skb is not VLAN tagged) is passed to bpf code,
but XDP hints specification requires drivers to return -ENODATA, if a hint
cannot be provided for a particular packet.

Solve this inconsistency by changing error return value of
__vlan_hwaccel_get_tag() from -EINVAL to -ENODATA, do the same thing to
__vlan_get_tag(), because this function is supposed to follow the same
convention. This, in turn, makes -ENODATA the only non-zero value
vlan_get_tag() can return. We can do this with no side effects, because
none of the users of the 3 above-mentioned functions rely on the exact
value.

Suggested-by: Jesper Dangaard Brouer <jbrouer@redhat.com>
Acked-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
Link: https://lore.kernel.org/r/20231205210847.28460-14-larysa.zaremba@intel.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h
index 3028af87716e291cafcb4d67d89bc810344c9554..c1645c86eed9693454398f566a446b6dc6fa37f4 100644 (file)
--- a/include/linux/if_vlan.h
+++ b/include/linux/if_vlan.h
@@ -540,7 +540,7 @@ static inline int __vlan_get_tag(const struct sk_buff *skb, u16 *vlan_tci)
        struct vlan_ethhdr *veth = skb_vlan_eth_hdr(skb);
 
        if (!eth_type_vlan(veth->h_vlan_proto))
-               return -EINVAL;
+               return -ENODATA;
 
        *vlan_tci = ntohs(veth->h_vlan_TCI);
        return 0;
@@ -561,7 +561,7 @@ static inline int __vlan_hwaccel_get_tag(const struct sk_buff *skb,
                return 0;
        } else {
                *vlan_tci = 0;
-               return -EINVAL;
+               return -ENODATA;
        }
 }