Remove check for presence of PACKET_TAG_IPSEC_PENDING_TDB and
PACKET_TAG_IPSEC_OUT_CRYPTO_NEEDED mbuf tags. They aren't used in FreeBSD.

Instead check presence of PACKET_TAG_IPSEC_OUT_DONE mbuf tag. If it
is found, bypass security policy lookup as described in the comment.

PACKET_TAG_IPSEC_OUT_DONE tag added to mbuf when IPSEC code finishes
ESP/AH processing. Since it was already finished, this means the security
policy placed in the tdb_ident was already checked. And there is no reason
to check it again here.

Obtained from:	Yandex LLC
Sponsored by:	Yandex LLC
Remove PACKET_TAG_IPSEC_IN_DONE mbuf tag lookup and usage of its
security policy. The changed block of code in ip*_ipsec_input() is
called when packet has ESP/AH header. Presence of
PACKET_TAG_IPSEC_IN_DONE mbuf tag in the same time means that
packet was already handled by IPSEC and reinjected in the netisr,
and it has another ESP/AH headers (encrypted twice?).
Since it was already processed by IPSEC code, the AH/ESP headers
was already stripped (and probably outer IP header was stripped too)
and security policy from the tdb_ident was applied to those headers.
It is incorrect to apply this security policy to current headers.

Also make ip_ipsec_input() prototype similar to ip6_ipsec_input().

Obtained from:	Yandex LLC
Sponsored by:	Yandex LLC
Move ip_ipsec_fwd() from ip_input() into ip_forward().

Remove check for presence PACKET_TAG_IPSEC_IN_DONE mbuf tag from
ip_ipsec_fwd(). PACKET_TAG_IPSEC_IN_DONE tag means that packet is
already handled by IPSEC code. This means that before IPSEC processing
it was destined to our address and security policy was checked in
the ip_ipsec_input(). After IPSEC processing packet has new IP
addresses and destination address isn't our own. So, anyway we can't
check security policy from the mbuf tag, because it corresponds
to different addresses.

We should check security policy that corresponds to packet
attributes in both cases - when it has a mbuf tag and when it has not.

Obtained from:	Yandex LLC
Sponsored by:	Yandex LLC
Merge remote-tracking branch 'freebsd/master' into hardened/current/master