slt(8) multiplex a port for multiple TLS applications with SNI


slt config-file


slt is a TLS reverse-proxy which allows an administrator to run multiple TLS applications on a single port. slt multiplexes incoming connections by inspecting the Server Name Indication (SNI) extension data and appropriately forwarding the connection to the appropriate upstream server.


Configure slt with a simple YAML file. Specify a bind_addr to instuct slt where it should listen for incoming connections. slt may listen for any number of frontends. Each frontend is identified by the name to match in the SNI data. Each frontend forwards to any number of backends. You may specify each backend with a hash of values. The only required attribute is addr. When more than one backend is enumerated, slt performs simple round-robin load balancing among them.

An example configuration follows for listening on port 443 of all local interfaces multiplexing traffic for two applications, and forwards to a single upstream server on port 1234. forwards to two upstream hosts on different addresses:

bind_addr: ":443"
      - addr: ":1234"
      - addr: ""
      - addr: ""

By default, slt does not terminate any TLS traffic. slt only inspects connections for their SNI data before being forwarded upstream. slt may terminate TLS traffic for any frontend by providing paths to the TLS public certificate and private key files, like so:

    tls_key: /path/to/
    tls_crt: /path/to/

Designate one frontend to be the default in the case that no SNI data is present in the connection like so:

    default: true


Exit status is 0 on success, non-zero on failure.


Source code and documentation
Server Name Indication


Alan Shreve (@inconshreveable)