tinc

Tinc is an open-source virtual private network daemon that creates a mesh VPN, enabling encrypted tunnels between multiple hosts across the internet. Unlike traditional VPNs that rely on a single central server, tinc builds a distributed network where each node can connect to many others, forming a flexible and scalable overlay.

The system uses a public-key infrastructure to establish trust between peers. Each host in a tinc network has a unique name and a certificate, and the relationships between hosts are defined by listing peers in the network configuration. When a new host is added, its certificate and host file are shared with the network, after which traffic can be routed through the new peer. This design supports dynamic membership and partial mesh topologies without requiring a central authority for every connection.

Configuration and operation are organized around a per-net directory, typically under /etc/tinc/<netname>. The net is defined by a tinc.conf file, and the membership of each node is described by host files in a hosts directory. Tinc runs as a daemon (tincd) and provides auxiliary tools for management. Each node can declare which subnets it offers, and the daemon handles the setup of tunnels and routing portions of traffic to the appropriate peers.

Key features include support for IPv4 and IPv6, the ability to route traffic to subnets reachable through other nodes, and encryption of traffic over the tunnels. Tinc is cross-platform, with implementations available for Linux, BSD, macOS, and Windows, and it is distributed under the GNU General Public License. It is commonly used to connect distributed networks, remote offices, or mobile devices into a cohesive VPN mesh.