[strongSwan] configured DH group CURVE_25519 not supported

[Tobias Brunner]

Hi Gyula,

> First, without --disable-curve25519, which means that the plugin is
> enabled (https://wiki.strongswan.org/projects/strongswan/wiki/Autoconf).
> After that, I added --disable-curve25519 to ./configure options.

Also note that you might need to run `make clean` first after you
changed the configure options.  Then make sure the plugin is actually
built, installed, and loaded at runtime (log or `ipsec statusall`).

You can also change the IKE proposal (`ike` keyword in ipsec.conf) so
curve25519 is not used.

Regards,
Tobias