From a78bc9450b3653f3c68f6a858514744acc7f3b2f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ma=C3=ABl=20Gramain?= <mael@enpls.org>
Date: Sat, 19 Aug 2023 23:38:21 +0200
Subject: [PATCH] upload script

---
 autogre.sh | 128 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 128 insertions(+)
 create mode 100755 autogre.sh

diff --git a/autogre.sh b/autogre.sh
new file mode 100755
index 0000000..db33c3f
--- /dev/null
+++ b/autogre.sh
@@ -0,0 +1,128 @@
+#!/bin/bash 
+
+# This script is used to automatically generate the GRE tunnel between two hosts based on FQDN
+
+# CONSTANTS
+# If not defined in the environment, the following variables will be used
+
+if [[ -z $GRE_TUNNEL_NAME ]]; then
+    GRE_TUNNEL_NAME="gre1"
+    GRE_TUNNEL_NAME="gre1"
+    GRE_LOCAL_IP="45.13.XX.XX"
+    GRE_LAN_IP_4="192.168.100.1/24"
+    GRE_LAN_IP_6="2a0e:fd45:2a0c::1/64"
+fi
+
+FQDN=$1 # The remote host FQDN
+
+# FUNCTIONS
+function usage() {
+    echo "Usage: $0 <remote_host_fqdn>"
+    exit 1
+}
+
+function check_root() {
+    if [[ $EUID -ne 0 ]]; then
+        echo "This script must be run as root"
+        exit 1
+    fi
+}
+
+
+function check_fqdn() {
+    if [[ -z $FQDN ]]; then
+        echo "Please provide the remote host FQDN"
+        usage
+    fi
+}
+
+function get_current_ip() {
+    # Get the dst IP on the GRE tunnel
+    CURRENT_IP=$(ip addr show $GRE_TUNNEL_NAME | grep -Po 'peer \K[\d.]+')
+    if [[ -z $CURRENT_IP ]]; then
+        echo "GRE tunnel is down or not configured"
+        # Create the GRE tunnel
+        CURRENT_IP=""
+    fi
+}
+
+function get_remote_ip() {
+    # Get the remote IP on the GRE tunnel
+    REMOTE_IP=$(dig +short $FQDN | tail -n1)
+    if [[ -z $REMOTE_IP ]]; then
+        echo "Failed to resolve the remote host FQDN ($FQDN)"
+        exit 1 
+    fi
+}
+
+function check_gre_tunnel() {
+    # Check if the GRE tunnel is up
+    if [[ -z $CURRENT_IP ]]; then
+        echo "GRE tunnel is down or not configured"
+        # Return 1 to indicate that the GRE tunnel is down
+        return 1
+    fi
+}
+
+function configure_gre_tunnel() {
+    # Configure the GRE tunnel
+    # Delete the GRE tunnel if it exists
+    echo "LOG - $(date) - REMOTE IP: $REMOTE_IP"
+    echo "ip link del $GRE_TUNNEL_NAME"
+    ip link del $GRE_TUNNEL_NAME
+    # Create the GRE tunnel
+    echo "ip link add $GRE_TUNNEL_NAME type gre remote $REMOTE_IP local $GRE_LOCAL_IP ttl 255"
+    ip link add $GRE_TUNNEL_NAME type gre remote $REMOTE_IP local $GRE_LOCAL_IP ttl 255
+    echo "ip link set $GRE_TUNNEL_NAME up"
+    ip link set $GRE_TUNNEL_NAME up
+    echo "ip addr add  $GRE_LAN_IP_4 dev $GRE_TUNNEL_NAME"
+    ip addr add  $GRE_LAN_IP_4 dev $GRE_TUNNEL_NAME
+    echo "ip addr add  $GRE_LAN_IP_6 dev $GRE_TUNNEL_NAME"
+    ip addr add  $GRE_LAN_IP_6 dev $GRE_TUNNEL_NAME
+}
+
+function check_remote_ip() {
+    # Check if the remote IP is the same as the one configured on the GRE tunnel
+    if [[ $REMOTE_IP == $CURRENT_IP ]]; then
+        echo "GRE tunnel is already configured with the right remote IP"
+        # Return 0 to indicate that the GRE tunnel is already configured
+        exit 0
+    else
+        echo "GRE tunnel is configured with the wrong remote IP"
+        configure_gre_tunnel
+        echo "Updated GRE tunnel with the right remote IP"
+        exit 0        
+    fi
+}
+
+# MAIN
+function main() {
+    check_root
+    check_fqdn
+
+    echo "LOG - $(date) - Starting autogre.sh"
+    echo "LOG - $(date) - FQDN: $FQDN"
+    echo "LOG - $(date) - GRE_TUNNEL_NAME: $GRE_TUNNEL_NAME"
+    echo "LOG - $(date) - GRE_LOCAL_IP: $GRE_LOCAL_IP"
+    echo "LOG - $(date) - GRE_LAN_IP_4: $GRE_LAN_IP_4"
+    echo "LOG - $(date) - GRE_LAN_IP_6: $GRE_LAN_IP_6"
+
+    echo "LOG - $(date) - Checking if the GRE tunnel is configured"
+    get_current_ip
+
+    echo "LOG - $(date) - Checking if the remote IP is the same as the one configured on the GRE tunnel"
+    get_remote_ip
+
+    echo "LOG - $(date) - Checking if the GRE tunnel is up"
+    if check_gre_tunnel ; then
+        echo "LOG - $(date) - GRE tunnel is up"
+        check_remote_ip
+        echo "LOG - $(date) - GRE tunnel is configured with the right remote IP"
+    else
+        echo "LOG - $(date) - GRE tunnel is down"
+        configure_gre_tunnel
+        echo "LOG - $(date) - Updated GRE tunnel with the right remote IP"
+    fi
+}
+
+main