xfrm: Guard IPsec anti replay window against replay bitmap

xfrm: Guard IPsec anti replay window against replay bitmap

For legacy IPsec anti replay mechanism:

bitmap in struct xfrm_replay_state could only provide a 32 bits
window size limit in current design, thus user level parameter
sadb_sa_replay should honor this limit, otherwise misleading
outputs("replay=244") by setkey -D will be:

192.168.25.2 192.168.22.2
	esp mode=transport spi=147561170(0x08cb9ad2) reqid=0(0x00000000)
	E: aes-cbc  9a8d7468 7655cf0b 719d27be b0ddaac2
	A: hmac-sha1  2d2115c2 ebf7c126 1c54f186 3b139b58 264a7331
	seq=0x00000000 replay=244 flags=0x00000000 state=mature
	created: Sep 17 14:00:00 2013	current: Sep 17 14:00:22 2013
	diff: 22(s)	hard: 30(s)	soft: 26(s)
	last: Sep 17 14:00:00 2013	hard: 0(s)	soft: 0(s)
	current: 1408(bytes)	hard: 0(bytes)	soft: 0(bytes)
	allocated: 22	hard: 0	soft: 0
	sadb_seq=1 pid=4854 refcnt=0
192.168.22.2 192.168.25.2
	esp mode=transport spi=255302123(0x0f3799eb) reqid=0(0x00000000)
	E: aes-cbc  6485d990 f61a6bd5 e5660252 608ad282
	A: hmac-sha1  0cca811a eb4fa893 c47ae56c 98f6e413 87379a88
	seq=0x00000000 replay=244 flags=0x00000000 state=mature
	created: Sep 17 14:00:00 2013	current: Sep 17 14:00:22 2013
	diff: 22(s)	hard: 30(s)	soft: 26(s)
	last: Sep 17 14:00:00 2013	hard: 0(s)	soft: 0(s)
	current: 1408(bytes)	hard: 0(bytes)	soft: 0(bytes)
	allocated: 22	hard: 0	soft: 0
	sadb_seq=0 pid=4854 refcnt=0

And also, optimizing xfrm_replay_check window checking by setting the
desirable x->props.replay_window with only doing the comparison once
for all when xfrm_state is first born.

Signed-off-by: Fan Du <fan.du@windriver.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>