From e2213b08ab03f2067c19afa7511b0bc989d700f4 Mon Sep 17 00:00:00 2001
From: Alexandre CATTEAU <alexandre.catteau@gmail.com>
Date: Sun, 4 Jun 2023 10:55:59 +0200
Subject: [PATCH] Change entirely the way to manage resolv.conf

---
 README.md                               |  2 +-
 install.sh                              |  4 ++--
 set-dns.sh                              | 15 +++++++++++++++
 set-resolv-conf.sh                      | 20 --------------------
 systemd-templates/set-ip-routes.service |  3 ++-
 unset-dns.sh                            | 10 ++++++++++
 6 files changed, 30 insertions(+), 24 deletions(-)
 create mode 100755 set-dns.sh
 delete mode 100755 set-resolv-conf.sh
 create mode 100755 unset-dns.sh

diff --git a/README.md b/README.md
index b1581d4..eabde47 100644
--- a/README.md
+++ b/README.md
@@ -7,11 +7,11 @@ This repository contains setup or configuration files for [LibreELEC](https://li
 https://wiki.libreelec.tv/configuration/wireguard for reference)
 
 ### Files
-* `set-resolv-conf.sh` moves last DNS entry up in `/etc/resolv.conf` (is called after VPN initialization)
 * `variables.conf.template` contains examples variables definitions, and should be copied locally to `variables.conf`
   (with any required modifications).
 * `systemd-templates/` contains Systemd units templates for detecting VPN connection, and apply routes and DNS
   modifications.
+* `set-dns.sh` sets the VPN DNS to `resolv.conf`, and `unset-dns.sh` restores the previous `resolv.conf`.
 #### Installation
 * `install.sh` script copies Systemd templates to their destination, and enables trigger (Systemd path).
 
diff --git a/install.sh b/install.sh
index 4c04306..2db79ef 100755
--- a/install.sh
+++ b/install.sh
@@ -17,8 +17,8 @@ cp $run_directory/systemd-templates/set-ip-routes.path /storage/.config/system.d
 
 echo "Reloading Systemd..."
 systemctl daemon-reload
-echo "Enabling path unit (not starting it, either do it manually or reboot)..."
-systemctl enable set-ip-routes.path
+#echo "Enabling path unit (not starting it, either do it manually or reboot)..."
+#systemctl enable set-ip-routes.path
 
 echo "Finished install. Exiting..."
 exit 0
diff --git a/set-dns.sh b/set-dns.sh
new file mode 100755
index 0000000..95fba0b
--- /dev/null
+++ b/set-dns.sh
@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+
+run_directory=$(dirname $(readlink -f "$0"))
+
+source "$run_directory/variables.conf"
+
+# count lines in resolv.conf
+lines=$(cat /run/libreelec/resolv.conf | wc -l)
+# count number of 'nameserver' entries
+count=$(grep -c 'nameserver' /run/libreelec/resolv.conf)
+
+cp /run/libreelec/resolv.conf /run/libreelec/resolv.conf.bck
+sed -i "$((lines - count + 1))s/^/nameserver $dns_server\n/" /run/libreelec/resolv.conf
+
+exit 0
diff --git a/set-resolv-conf.sh b/set-resolv-conf.sh
deleted file mode 100755
index ce8ae36..0000000
--- a/set-resolv-conf.sh
+++ /dev/null
@@ -1,20 +0,0 @@
-#!/usr/bin/env bash
-
-# TODO review entirely:
-# * use DNS variable to set the first nameserver line
-# * add an "ExecStop" to service, and a script to remove that first line
-
-# count lines in resolv.conf
-lines=$(cat /run/libreelec/resolv.conf | wc -l)
-# count number of 'nameserver' entries
-count=$(grep -c 'nameserver' /run/libreelec/resolv.conf)
-
-# move last entry to top
-i=$((0))
-while [ $((count)) -gt 1 ]; do
-  sed -i -n "$((lines - i - 1)){h;n;G};p" /run/libreelec/resolv.conf
-  count=$((count - 1))
-  i=$((i + 1))
-done
-
-exit 0
diff --git a/systemd-templates/set-ip-routes.service b/systemd-templates/set-ip-routes.service
index bea75fb..c1a2ef5 100644
--- a/systemd-templates/set-ip-routes.service
+++ b/systemd-templates/set-ip-routes.service
@@ -7,4 +7,5 @@ RemainAfterExit=yes
 ExecStart=/usr/sbin/ip route del default dev wg0
 ExecStart=/usr/sbin/ip route add PH_DNS dev wg0
 ExecStart=/usr/sbin/ip route add PH_NETWORK dev wg0
-ExecStart=/usr/bin/bash /storage/libreelec-conf/set-resolv-conf.sh
+ExecStart=/usr/bin/bash /storage/libreelec-conf/set-dns.sh
+ExecStop=/usr/bin/bash /storage/libreelec-conf/unset-dns.sh
diff --git a/unset-dns.sh b/unset-dns.sh
new file mode 100755
index 0000000..a9e3aa6
--- /dev/null
+++ b/unset-dns.sh
@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+
+run_directory=$(dirname $(readlink -f "$0"))
+
+source "$run_directory/variables.conf"
+
+rm /run/libreelec/resolv.conf
+mv /run/libreelec/resolv.conf.bck /run/libreelec/resolv.conf
+
+exit 0