From ee62891f744b74939ab66c3153a906f6ae026f93 Mon Sep 17 00:00:00 2001
From: Jason Separovic <jason.separovic@nokia.com>
Date: Thu, 8 Dec 2022 21:55:33 -0800
Subject: [PATCH] add post script functionality

---
 README.md            | 15 +++++++++++++++
 rootfs/entrypoint.sh | 21 +++++++++++++++++++--
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 267fd6f..544bbc8 100644
--- a/README.md
+++ b/README.md
@@ -259,6 +259,21 @@ Examples:
 
 Additional details are available from [`ssh_config(5)`](https://linux.die.net/man/5/ssh_config)
 
+#### SSH_POST_SCRIPT
+
+When set, SSH_POST_SCRIPT will be the location of a shell script to execute after starting autossh.
+This is useful to send some details to the server about the autossh client.
+For example, if a random port is used, then it's useful for the server to know who is on this port.
+SSH_TUNNEL_PORT can be used in the post script like so:
+```
+FILE=/tmp/autossh.${SSH_CLIENT_ID}
+echo "${SSH_TUNNEL_PORT}" > ${FILE}
+scp ${FILE} ${SSH_REMOTE_USER}@${SSH_REMOTE_HOST}:/tmp
+```
+In this example SSH_CLIENT_ID is set to some identifier that represents the client and the port is 
+set in a file. This could be useful when you have multiple client connections and you need to know 
+on the server which client to connect to. Mount the shell script in a docker volume.
+
 #### Additional Environment variables
 
 - [`autossh(1)`](https://linux.die.net/man/1/autossh)
diff --git a/rootfs/entrypoint.sh b/rootfs/entrypoint.sh
index 24ad65f..28b481f 100755
--- a/rootfs/entrypoint.sh
+++ b/rootfs/entrypoint.sh
@@ -62,5 +62,22 @@ COMMAND="autossh "\
 
 echo "[INFO ] # ${COMMAND}"
 
-# Run command
-exec ${COMMAND}
+# Run autossh command in background and save pid
+exec ${COMMAND} &
+pid=$!
+sleep 1
+
+# Export the Tunnel Port for post script to use
+export SSH_TUNNEL_PORT=${SSH_TUNNEL_PORT}
+
+if [[ -e /proc/$pid ]] && [[ -n "${SSH_POST_SCRIPT}" ]]; then
+  if [[ -f "${SSH_POST_SCRIPT}" ]]; then
+    # Execute Post Script
+    echo "[INFO ] Executing ${SSH_POST_SCRIPT}"
+    /bin/sh "${SSH_POST_SCRIPT}"
+  else
+    echo "[WARN ] ${SSH_POST_SCRIPT} was not found"
+  fi
+fi
+
+wait $pid