Use ipsec6_in_reject() to simplify ip6_ipsec_fwd() and ip6_ipsec_input().
ipsec6_in_reject() does the same things, also it counts policy violation
errors.

Do IPSEC check in the ip6_forward() after addresses checks.
Also use ip6_ipsec_fwd() to make code similar to IPv4 implementation.

Obtained from: Yandex LLC
Sponsored by: Yandex LLC