macsec: Netlink support of XPN cipher suites (IEEE 802.1AEbw)

Netlink support of extended packet number cipher suites,
allows adding and updating XPN macsec interfaces.

Added support in:
    * Creating interfaces with GCM-AES-XPN-128 and GCM-AES-XPN-256 suites.
    * Setting and getting 64bit packet numbers with of SAs.
    * Setting (only on SA creation) and getting ssci of SAs.
    * Setting salt when installing a SAK.

Added 2 cipher suite identifiers according to 802.1AE-2018 table 14-1:
    * MACSEC_CIPHER_ID_GCM_AES_XPN_128
    * MACSEC_CIPHER_ID_GCM_AES_XPN_256

In addition, added 2 new netlink attribute types:
    * MACSEC_SA_ATTR_SSCI
    * MACSEC_SA_ATTR_SALT

Depends on: macsec: Support XPN frame handling - IEEE 802.1AEbw.

Signed-off-by: Era Mayflower <mayflowerera@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/macsec.h b/include/net/macsec.h
index 43cd54e..2e4780d 100644
--- a/include/net/macsec.h
+++ b/include/net/macsec.h
@@ -11,6 +11,9 @@
 #include <uapi/linux/if_link.h>
 #include <uapi/linux/if_macsec.h>
 
+#define MACSEC_DEFAULT_PN_LEN 4
+#define MACSEC_XPN_PN_LEN 8
+
 #define MACSEC_SALT_LEN 12
 #define MACSEC_NUM_AN 4 /* 2 bits for the association number */