xfrm: Add basic infrastructure to support IPsec extended sequence numbers

This patch adds the struct xfrm_replay_state_esn which will be
used to support IPsec extended sequence numbers and anti replay windows
bigger than 32 packets. Also we add a function that returns the actual
size of the xfrm_replay_state_esn, a xfrm netlink atribute and a xfrm state
flag for the use of extended sequence numbers.

Signed-off-by: Steffen Klassert <[e-mail]>
Acked-by: Herbert Xu <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/linux/xfrm.h

···
 	__u32	bitmap;
 };
 
+struct xfrm_replay_state_esn {
+	unsigned int	bmp_len;
+	__u32		oseq;
+	__u32		seq;
+	__u32		oseq_hi;
+	__u32		seq_hi;
+	__u32		replay_window;
+	__u32		bmp[0];
+};
+
 struct xfrm_algo {
 	char		alg_name[64];
 	unsigned int	alg_key_len;    /* in bits */
···
 	XFRMA_ALG_AUTH_TRUNC,	/* struct xfrm_algo_auth */
 	XFRMA_MARK,		/* struct xfrm_mark */
 	XFRMA_TFCPAD,		/* __u32 */
+	XFRMA_REPLAY_ESN_VAL,	/* struct xfrm_replay_esn */
 	__XFRMA_MAX
 
 #define XFRMA_MAX (__XFRMA_MAX - 1)
···
 #define XFRM_STATE_ICMP		16
 #define XFRM_STATE_AF_UNSPEC	32
 #define XFRM_STATE_ALIGN4	64
+#define XFRM_STATE_ESN		128
 };
 
 struct xfrm_usersa_id {

include/net/xfrm.h

···
 
 	/* State for replay detection */
 	struct xfrm_replay_state replay;
+	struct xfrm_replay_state_esn *replay_esn;
 
 	/* Replay detection state at the time we sent the last notification */
 	struct xfrm_replay_state preplay;
+	struct xfrm_replay_state_esn *preplay_esn;
 
 	/* internal flag that only holds state for delayed aevent at the
 	 * moment
···
 static inline int xfrm_alg_auth_len(const struct xfrm_algo_auth *alg)
 {
 	return sizeof(*alg) + ((alg->alg_key_len + 7) / 8);
+}
+
+static inline int xfrm_replay_state_esn_len(struct xfrm_replay_state_esn *replay_esn)
+{
+	return sizeof(*replay_esn) + replay_esn->bmp_len * sizeof(__u32);
 }
 
 #ifdef CONFIG_XFRM_MIGRATE