rxrpc: rxgk: Implement connection rekeying

Implement rekeying of connections with the RxGK security class.  This
involves regenerating the keys with a different key number as part of the
input data after a certain amount of time or a certain amount of bytes
encrypted.  Rekeying may be triggered by either end.

The LSW of the key number is inserted into the security-specific field in
the RX header, and we try and expand it to 32-bits to make it last longer.

Signed-off-by: David Howells <dhowells@redhat.com>
3 files changed