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SOCKET-ACTIVATION.md

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Socket Activation

Ghostunnel supports socket activation via both systemd (on Linux) and launchd (on macOS). Socket activation is support for the --listen and --status flags, and can be used by passing an address of the form systemd:<name> or launchd:<name>, where <name> should be the name of the socket as defined in your systemd/launchd configuration.

launchd

A launchd plist to launch ghostunnel in server mode on :8081, listening for status connections on :8082, and forwarding connections to :8083 could look like this:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
  <dict>
    <key>Label</key>
    <string>com.square.ghostunnel</string>
    <key>ProgramArguments</key>
    <array>
      <string>/usr/bin/ghostunnel</string>
      <string>server</string>
      <string>--keystore</string>
      <string>/etc/ghostunnel/server-keystore.p12</string>
      <string>--cacert</string>
      <string>/etc/ghostunnel/cacert.pem</string>
      <string>--target</string>
      <string>localhost:8083</string>
      <string>--listen</string>
      <string>launchd:Listener</string>
      <string>--status</string>
      <string>launchd:Status</string>
      <string>--allow-cn</string>
      <string>client</string>
    </array>
    <key>StandardOutPath</key>
    <string>/var/log/ghostunnel.out.log</string>
    <key>StandardErrorPath</key>
    <string>/var/log/ghostunnel.err.log</string>
    <key>Sockets</key>
    <dict>
      <key>Listener</key>
      <dict>
        <key>SockServiceName</key>
        <string>8081</string>
        <key>SockType</key>
        <string>stream</string>
        <key>SockFamily</key>
        <string>IPv4</string>
      </dict>
      <key>Status</key>
      <dict>
        <key>SockServiceName</key>
        <string>8082</string>
        <key>SockType</key>
        <string>stream</string>
        <key>SockFamily</key>
        <string>IPv4</string>
      </dict>
    </dict>
  </dict>
</plist>

Note that in the launchd case both SockType and SockFamily need to be defined for each socket. If for example the family were to be left out, launchd would open two sockets (IPv4 and IPv6) for the given key (like Listener) and pass them to ghostunnel which is not currently supported.

systemd

A systemd unit for a ghostunnel.socket for listening on *:8443 could look like this:

[Unit]
Description=Ghostunnel Socket
PartOf=ghostunnel.service

[Socket]
FileDescriptorName=ghostunnel
ListenStream=0.0.0.0:8443

[Install]
WantedBy=sockets.target

With a corresponding ghostunel.service to forward to localhost:8080 could look like this:

[Unit]
Description=Ghostunnel
After=network.target ghostunnel.socket
Requires=ghostunnel.socket

[Service]
Type=simple
ExecStart=/etc/cron/bin/ghostunnel server --listen=systemd:ghostunnel --target=localhost:8080 --keystore=/etc/ghostunnel/server-keystore.p12 --cacert /etc/ghostunnel/cacert.pem --allow-cn client

[Install]
WantedBy=default.target

Note that the FileDescriptorName in ghostunnel.socket matches the name passed to --listen. If multiple sockets are needed, e.g. for a status port, the name can be used to distinguish the listening and status sockets.