StrongSwan is an OpenSource IPsec implementation for Linux.

This SlackBuild enables configure options which are known to compile
without issue on a stock Slackware 14.2 system. These options provide
additional functionality and increase this packages ability to
inter operate with various vendor implementations. Unwanted and/or
unnecessary plugins can be disabled a run-time via the 'load' flag in
/etc/strongswan.d/charon/*.conf files.

The following configure options are enabled by default:

    --enable-shared
    --enable-silent-rules
    --enable-openssl
    --enable-unity
    --enable-curl
    --enable-sql
    --enable-sqlite
    --enable-cmd
    --enable-af-alg
    --enable-gcrypt
    --enable-aesni
    --enable-sha3
    --enable-files
    --enable-lookip
    --enable-eap-mschapv2
    --enable-eap-tls
    --enable-eap-ttls
    --enable-eap-radius
    --enable-ext-auth
    --enable-xauth-eap

To disable the above options set the environment variable CONFIG_OPTS
to the empty string when calling this SlackBuild.

Example:
env CONFIG_OPTS=" " sh ./strongswan.SlackBuild

To override the defaults options set CONFIG_OPTS to your desired set
of configure options.

Example:
env CONFIG_OPTS="--enable-openssl --enable-unity" sh ./strongswan.SlackBuild

To add to the default options without overwriting them set the
EXTRA_CONFIG_OPTS environment variable.

Example:
env EXTRA_CONFIG_OPTS="--enable-socket-dynamic --enable-dhcp"  sh ./strongswan.SlackBuild

The list of available options and their descriptions are available here:

https://wiki.strongswan.org/projects/strongswan/wiki/Autoconf