Forwards varlink messages to remote http (https) server. 

The listener is interface agnostic. The remote service is solely responsible
for implementing the appropriate varlink interfaces, including the standard 
interface (org.varlink.service) used for introspection.

  Usage: altlink [--cacert file] [--bearer token] remote target

  Required positional arguments
    remote string
      Remote (http) endpoint receiving forwarded varlink messages.
    target string
      Socket (unix) to serve locally.

  Optional arguments
    --cacert string
      Use the specified CA certificate, must be in PEM format.
    --bearer string
      Use the specified http/bearer authentication token.
      Set to @ to read from BEARER environment variable.

  Usage: altlink [--cacert file] [--bearer token] remote target

  Required positional arguments
    remote string
      Remote (http) endpoint receiving forwarded varlink messages.
    target string
      Socket (unix) to serve locally.

  Optional arguments
    --cacert string
      Use the specified CA certificate, must be in PEM format.
    --bearer string
      Use the specified http/bearer authentication token.
      Set to @ to read from BEARER environment variable.

  Optional arguments (experimental)
    --cache
      Cache requests (and responses).
    --cache-entry-expire time.Duration
      Cache entry expiration time (default 8s).
    --cache-evict-period time.Duration
      Cache eviction period (default 16s).      

Features

  - Listening on local unix socket and forwarding varlink messages.
  - The forwarded messages are sent verbatim as application/json payloads to
    remote HTTP endpoint over POST.

  - Support for self-signed cerificates.
  - Support for http/bearer authentication.

Examples

  The examples are to be used in conjunction with the example server. 
  Its setup is detailed below and should be performed first.

    # Start the altlink client.
    ./build/altlink \
      --bearer 9W4qlFTUloXHCrIO --cacert example/ssl.ca/CA.crt \
      https://localhost:8443/varlink /tmp/test.sock

    # Probe request/reply functionality using varlinkctl (no replies)
    varlinkctl call /tmp/test.sock example.Ping '' --oneway

    # Probe request/reply functionality using varlinkctl (single reply)
    varlinkctl call /tmp/test.sock example.Ping '{ "ping": 5 }'

    # Probe request/reply functionality using varlinkctl (multiple replies)
    varlinkctl call /tmp/test.sock example.Ping '{ "ping": 5 }' --more

Using the example server

  The server requires deno to run. 
  It has no external dependencies otherwise.

    # It is necessary to create the ssl certificates first.
    mkdir -p example/ssl.ca example/ssl.https
    openssl req -x509 \
      -new -newkey rsa:4096 -days 16 -nodes \
      -keyout example/ssl.ca/CA.key -out example/ssl.ca/CA.crt \
      -subj "/CN=XY-CA" \
      -addext "keyUsage = critical, keyCertSign, cRLSign" \
      -addext "basicConstraints = critical, CA:TRUE"
    openssl req \
      -CA example/ssl.ca/CA.crt -CAkey example/ssl.ca/CA.key \
      -newkey rsa:4096 -days 16 -nodes \
      -keyout example/ssl.https/server.key -out example/ssl.https/server.crt \
      -subj "/CN=XY-SERVER" \
      -addext "subjectAltName=IP:127.0.0.1,DNS:localhost" \
      -addext "keyUsage = critical, keyEncipherment, keyAgreement" \
      -addext "basicConstraints = critical, CA:FALSE" \
      -addext "extendedKeyUsage = critical, serverAuth"

    # Run the server 
    deno --allow-net --allow-read example/server.mjs

  Please note the server does not implement the org.varlink.service interface.