Fixes issue #15446

Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>

chacha20policy1305 is also an AEAD cipher, and hence does not
permit a hash algorithm.

Fixes issue #15397.

Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>

Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>

A subshell caused by $(...) can't persistently modify globals as a
side-effect.

Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>

Derived from the ipsec initd script, with the following changes:

(1) various code improvements, corrections (get rid of left/right
    updown scripts, since there's only one), etc;
(2) add reauth and fragmentation parameters;
(3) add x.509 certificate-based authentication;

and other minor changes.

Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>