- Support upgrading to Libreswan 4.9.
- Compilation of Libreswan 4.9 on Ubuntu 18.04 requires newer
versions of NSS packages. They are installed in a similar way
as apply_ubuntu1804_nss_fix in ikev2setup.sh.
Ref: https://github.com/libreswan/libreswan/issues/892
- Improve security by removing support for modp1536 (DH group 5),
which is less secure and rarely used by VPN clients. To do this,
we specify modp2048 on the "ike=" line in ipsec.conf.
- Improve security by removing support for modp1024 (DH group 2),
which is less secure and no longer enabled in Libreswan by default.
- The native VPN client on Android devices uses modp1024 for the
IPsec/L2TP and IPsec/XAuth ("Cisco IPsec") modes. After this change,
Android users should instead connect using IKEv2 mode (recommended).
- Instead of finding the server's public IP, use the IP address
on the default route if it is not a private IP. This makes VPN
setup slightly faster by skipping IP detection.
- Add a fallback URL for finding the server's public IP.
- Cleanup
