extension header type. The key_flush_sad() now will send SADB_EXPIRE
message when HARD lifetime expires. This is required by RFC 2367 and some
keying daemons rely on these messages. HARD lifetime messages have
precedence over SOFT lifetime messages, so now they will be checked first.
Also now SADB_EXPIRE messages will be send even the SA has not been used,
because keying daemons might want to rekey such SA.
PR: 200282, 200283
Submitted by: Tobias Brunner <tobias at strongswan dot org>
MFC after: 2 weeks
a7c61420ed