David Ahern [off-list ref] writes:

On 6/23/26 9:05 PM, Avinash Duduskar wrote:

quoted

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 89b36de5fdbb..e00f0392e728 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h

@@ -3532,6 +3532,29 @@ union bpf_attr {
  *			Use the mark present in *params*->mark for the fib lookup.
  *			This option should not be used with BPF_FIB_LOOKUP_DIRECT,
  *			as it only has meaning for full lookups.
+ *		**BPF_FIB_LOOKUP_VLAN**

This flag should not be needed. Patches for vlan support were never
submitted (I have them in some old branch). Since the vlan params are
initialized to 0, no new flag should be needed. Besides, these are
output parameters.

There's no enforcement from the kernel side of the parameters being
zero, though? So we do need the flag for feature detection; unless we
expect applications to do that out of band? But then we'd need a
mechanism to do that which could be... the presence of the flag in the
ENUM (and thus in BTF)? :)

-Toke