uapi: bpf.h update from upstream

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 1840da8d109c8b1a5b7254903a329bbd2e05ef58..b1aba6af430af01d4a34fab8838e2650f6d18081 100644 (file)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3850,7 +3850,7 @@ union bpf_attr {
  *
  * long bpf_check_mtu(void *ctx, u32 ifindex, u32 *mtu_len, s32 len_diff, u64 flags)
  *     Description
- *             Check ctx packet size against exceeding MTU of net device (based
+ *             Check packet size against exceeding MTU of net device (based
  *             on *ifindex*).  This helper will likely be used in combination
  *             with helpers that adjust/change the packet size.
  *
@@ -3867,6 +3867,14 @@ union bpf_attr {
  *             against the current net device.  This is practical if this isn't
  *             used prior to redirect.
  *
+ *             On input *mtu_len* must be a valid pointer, else verifier will
+ *             reject BPF program.  If the value *mtu_len* is initialized to
+ *             zero then the ctx packet size is use.  When value *mtu_len* is
+ *             provided as input this specify the L3 length that the MTU check
+ *             is done against. Remember XDP and TC length operate at L2, but
+ *             this value is L3 as this correlate to MTU and IP-header tot_len
+ *             values which are L3 (similar behavior as bpf_fib_lookup).
+ *
  *             The Linux kernel route table can configure MTUs on a more
  *             specific per route level, which is not provided by this helper.
  *             For route level MTU checks use the **bpf_fib_lookup**\ ()
@@ -3891,11 +3899,9 @@ union bpf_attr {
  *
  *             On return *mtu_len* pointer contains the MTU value of the net
  *             device.  Remember the net device configured MTU is the L3 size,
- *             which is returned here and XDP and TX length operate at L2.
+ *             which is returned here and XDP and TC length operate at L2.
  *             Helper take this into account for you, but remember when using
- *             MTU value in your BPF-code.  On input *mtu_len* must be a valid
- *             pointer and be initialized (to zero), else verifier will reject
- *             BPF program.
+ *             MTU value in your BPF-code.
  *
  *     Return
  *             * 0 on success, and populate MTU value in *mtu_len* pointer.