Add support for unix domain socket I2P Tunnels

[dimzon]

Например чтобы хостить eepSite через /var/run/nginx.sock

[agowa]

Hi, is there any update on this one? I'd also be interested in the ability to glue stuff together with i2pd using unix domain sockets.
Additionally to just basic support I.E. address = unix:///path/to/socket.sock, I'd also like to suggest adding user = userNameOrID and group = groupNameOrID. This way i2pd could place sockets into e.g. chroot environments of other services and thereby allow to harden the setup.
Also UDS in general have better performance than loopback tcp/udp. As well as improved security and safeguards against accidental exposure (or forwarding).

See e.g. https://stackoverflow.com/a/29436429 about UDS vs loopback TCP performance.

66% latency reduction and almost 7X more throughput explain why most performance-critical software has their own IPC custom protocol.

TCP average latency: 6 us
UDS average latency: 2 us
PIPE average latency: 2 us
TCP average throughput: 0.253702 million msg/s
UDS average throughput: 1.733874 million msg/s
PIPE average throughput: 1.682796 million msg/s