From ffd25cdb04f6a40bc9b95afd507042717b2f7fc5 Mon Sep 17 00:00:00 2001
From: Jan Tuomi <jan@jantuomi.fi>
Date: Thu, 10 Jul 2025 10:36:10 +0300
Subject: Generate specific dhclient.conf to coerce the ISP to offer the same
 IP

---
 templates/usr_local_bin_gen_dhclient_conf.sh.j2 | 38 +++++++++++++++++++++++++
 1 file changed, 38 insertions(+)
 create mode 100644 templates/usr_local_bin_gen_dhclient_conf.sh.j2

(limited to 'templates/usr_local_bin_gen_dhclient_conf.sh.j2')

diff --git a/templates/usr_local_bin_gen_dhclient_conf.sh.j2 b/templates/usr_local_bin_gen_dhclient_conf.sh.j2
new file mode 100644
index 0000000..8c05f70
--- /dev/null
+++ b/templates/usr_local_bin_gen_dhclient_conf.sh.j2
@@ -0,0 +1,38 @@
+#!/bin/sh
+
+set -eu
+
+IP=$(ifconfig wan0 | awk '/inet / {print $2}' | head -n1)
+HOSTNAME=$(hostname)
+CONFFILE=/etc/dhclient.conf
+NEWFILE=$(mktemp)
+if [ -f "${CONFFILE}" ]; then
+    OLDHASH=$(md5 -q "${CONFFILE}")
+else
+    OLDHASH="doesnotexist"
+fi
+
+cat <<EOF > "${NEWFILE}"
+# This file is generated by $0 periodically.
+# Changes will be overwritten.
+
+interface "wan0" {
+    send host-name "${HOSTNAME}";
+EOF
+
+if [ ! -z "$IP" ]; then
+cat <<EOF >> "${NEWFILE}"
+    send dhcp-requested-address $IP;
+EOF
+fi
+
+echo "}" >> "${NEWFILE}"
+
+mv "${NEWFILE}" "${CONFFILE}"
+
+# If changed, restart dhclient wan0
+md5 -c "${OLDHASH}" "${CONFFILE}" 1>/dev/null 2>/dev/null
+if [ ! "$?" = 0 ]; then
+    echo "Generated ${CONFFILE} has changed, restarting dhclient on wan0 (IP: ${IP})"
+    service dhclient restart wan0
+fi
-- 
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