bpf: Clarify error expectations from bpf_clone_redirect

Commit 151e887d8ff9 ("veth: Fixing transmit return status for dropped packets") exposed the fact that bpf_clone_redirect is capable of returning raw NET_XMIT_XXX return codes. This is in the conflict with its UAPI doc which says the following: "0 on success, or a negative error in case of failure." Update the UAPI to reflect the fact that bpf_clone_redirect can return positive error numbers, but don't explicitly define their meaning. Reported-by: Daniel Borkmann <[email protected]> Signed-off-by: Stanislav Fomichev <[email protected]> Signed-off-by: Daniel Borkmann <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
libbpf · Sep 11, 2023 · 99b26e3 · 99b26e3
1 parent 3338490
commit 99b26e3
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
@@ -1969,7 +1969,9 @@ union bpf_attr {
  * 		performed again, if the helper is used in combination with
  * 		direct packet access.
  * 	Return
- * 		0 on success, or a negative error in case of failure.
+ * 		0 on success, or a negative error in case of failure. Positive
+ * 		error indicates a potential drop or congestion in the target
+ * 		device. The particular positive error codes are not defined.
  *
  * u64 bpf_get_current_pid_tgid(void)
  * 	Description