[PATCH bpf-next 2/3] net: skbuff: reorder bytes 2 and 3 of the bitfield

Jakub Kicinski
2023-03-08T00:32:25Z

BPF needs to know the offsets of fields it tries to access.
Zero-length fields are added to make offsetof() work.
This unfortunately partitions the bitfield (fields across
the zero-length members can't be coalesced).

Reorder bytes 2 and 3, BPF needs to know the offset of fields
previously in byte 3 and some fields in byte 2 should really
be optional.

The two bytes are always in the same cacheline so it should
not matter.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
include/linux/skbuff.h | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 004009b3930f..c4122797d465 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -945,16 +945,6 @@ struct sk_buff {
__u8 ip_summed:2;
__u8 ooo_okay:1;

- __u8 l4_hash:1;
- __u8 sw_hash:1;
- __u8 wifi_acked_valid:1;
- __u8 wifi_acked:1;
- __u8 no_fcs:1;
- /* Indicates the inner headers are valid in the skbuff. */
- __u8 encapsulation:1;
- __u8 encap_hdr_csum:1;
- __u8 csum_valid:1;
-
/* private: */
__u8 __mono_tc_offset[0];
/* public: */
@@ -967,6 +957,16 @@ struct sk_buff {
__u8 tc_skip_classify:1;
__u8 tc_at_ingress:1; /* See TC_AT_INGRESS_MASK */
#endif
+
+ __u8 l4_hash:1;
+ __u8 sw_hash:1;
+ __u8 wifi_acked_valid:1;
+ __u8 wifi_acked:1;
+ __u8 no_fcs:1;
+ /* Indicates the inner headers are valid in the skbuff. */
+ __u8 encapsulation:1;
+ __u8 encap_hdr_csum:1;
+ __u8 csum_valid:1;
#ifdef CONFIG_IPV6_NDISC_NODETYPE
__u8 ndisc_nodetype:2;
#endif
--
2.39.2