Support extended packet number cipher suites (802.1AEbw) frames handling.
This does not include the needed netlink patches.
* Added xpn boolean field to `struct macsec_secy`.
* Added ssci field to `struct_macsec_tx_sa` (802.1AE figure 10-5).
* Added ssci field to `struct_macsec_rx_sa` (802.1AE figure 10-5).
* Added salt field to `struct macsec_key` (802.1AE 10.7 NOTE 1).
* Created pn_t type for easy access to lower and upper halves.
* Created salt_t type for easy access to the "ssci" and "pn" parts.
* Created `macsec_fill_iv_xpn` function to create IV in XPN mode.
* Support in PN recovery and preliminary replay check in XPN mode.
In addition, according to IEEE 802.1AEbw figure 10-5, the PN of incoming
frame can be 0 when XPN cipher suite is used, so fixed the function
`macsec_validate_skb` to fail on PN=0 only if XPN is off.
Signed-off-by: Era Mayflower <mayflowerera@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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