Generate specific dhclient.conf to coerce the ISP to offer the same IP

1 files changed, 38 insertions, 0 deletions

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