P2P de-centralized layer 3 VPN

 OpenGNB is a de-centralized virtual private network (VPN) to set-up a
 layer 3 network via P2P with the capability of NAT traversal.
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 OpenGNB can add many nodes and LANs together into one big VPN.
 OpenGNB supports public index nodes to forward net packages.
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 OpenGNB support the following platforms:
 Linux, FreeBSD, OpenBSD, and macOS.
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 OpenGNB uses UDP by default. With the software gnb_udp_over_tcp
 installed it can also use TCP.