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xfrm: reduce struct sec_path size

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The mentioned struct has an hole and uses unnecessary wide type to
store MAC length and indexes of very small arrays.

It's also embedded into the skb_extensions, and the latter, due
to recent CAN changes, may exceeds the 192 bytes mark (3 cachelines
on x86_64 arch) on some reasonable configurations.

Reordering and the sec_path fields, shrinking xfrm_offload.orig_mac_len
to 16 bits and xfrm_offload.{len,olen,verified_cnt} to u8, we can save
16 bytes and keep skb_extensions size under control.

Before:

struct sec_path {
	int                        len;
	int                        olen;
	int                        verified_cnt;

	/* XXX 4 bytes hole, try to pack */$
	struct xfrm_state *        xvec[6];
	struct xfrm_offload ovec[1];

	/* size: 88, cachelines: 2, members: 5 */
	/* sum members: 84, holes: 1, sum holes: 4 */
	/* last cacheline: 24 bytes */
};

After:

struct sec_path {
	struct xfrm_state *        xvec[6];
	struct xfrm_offload        ovec[1];
	/* typedef u8 -> __u8 */ unsigned char              len;
	/* typedef u8 -> __u8 */ unsigned char              olen;
	/* typedef u8 -> __u8 */ unsigned char              verified_cnt;

	/* size: 72, cachelines: 2, members: 5 */
	/* padding: 1 */
	/* last cacheline: 8 bytes */
};

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Steffen Klassert <steffen.klassert@secunet.com>
Link: https://patch.msgid.link/83846bd2e3fa08899bd0162e41bfadfec95e82ef.1770398071.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Paolo Abeni 2026-02-06 18:14:36 +01:00 • committed by Jakub Kicinski
parent e72d4c537f
commit dc010e1b4b
1 changed files with 5 additions and 5 deletions
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10
include/net/xfrm.h
View file

@ -1156,19 +1156,19 @@ struct xfrm_offload {
#define CRYPTO_INVALID_PROTOCOL 128
/* Used to keep whole l2 header for transport mode GRO */
__u32 orig_mac_len;
__u16 orig_mac_len;
__u8 proto;
__u8 inner_ipproto;
};
struct sec_path {
int len;
int olen;
int verified_cnt;
struct xfrm_state *xvec[XFRM_MAX_DEPTH];
struct xfrm_offload ovec[XFRM_MAX_OFFLOAD_DEPTH];
u8 len;
u8 olen;
u8 verified_cnt;
};
struct sec_path *secpath_set(struct sk_buff *skb);