Libreswan is an open-source implementation of the IPsec and IKE protocols, which are used for secure Virtual Private Network (VPN) communications. Based on the FreeS/WAN project, Libreswan continues to offer robust and secure IPsec-based VPN solutions for Linux systems. It is widely used to establish secure site-to-site and remote-access VPNs, with strong support for IKEv1 and IKEv2 standards.

Features of Libreswan:

• Support for both IKEv1 and IKEv2 protocols.
• Integration with the Linux kernel’s IPsec stack (NETKEY).
• Robust support for X.509 certificates, Pre-Shared Keys (PSKs), and smartcards.
• Secure NAT traversal and Dead Peer Detection (DPD).
• Works seamlessly with systemd, SELinux, and modern Linux distributions.

To check LibreSwan version:

$ ipsec --version

Disclaimer: Libreswan is distributed under the GNU General Public License (GPL). It is provided "as is," without any warranty, express or implied. Users are responsible for correct configuration and compliance with security policies.