feat(ns-storage): persist DHCP leases

Store dnsmasq DHCP leases on /mnt/data when storage is
available and keep /tmp/dhcp.leases as the compatibility
path for existing readers.

Switch back to /tmp before storage removal and restart
victoria-metrics around fstab changes so the data mount
can be released cleanly.

Assisted-by: Copilot:gpt-5.4

Author: gsanchietti

packages/ns-api/README.md

@@ -2847,6 +2847,10 @@ List active DHCPv4 leases:
 api-cli ns.dhcp list-active-leases
 ```
 
+The method reads the dnsmasq lease file configured in
+`dhcp.ns_dnsmasq.leasefile` and falls back to `/tmp/dhcp.leases` when the
+option is unset.
+
 Response example:
 ```json
 {

packages/ns-api/files/ns.dhcp

@@ -10,6 +10,7 @@
 import sys
 import json
 import ipaddress
+import os
 import subprocess
 from euci import EUci
 from nethsec import utils, objects
@@ -221,7 +222,11 @@ def list_active_leases():
         if 'mac' in ldata and 'ip' in ldata:
             static_leases.append(ldata['mac'].lower())
 
-    with open("/tmp/dhcp.leases", "r") as fp:
+    leasefile = u.get('dhcp', 'ns_dnsmasq', 'dhcp', 'leasefile', default='/tmp/dhcp.leases')
+    if not os.path.exists(leasefile):
+        return ret
+
+    with open(leasefile, "r") as fp:
         for line in fp.readlines():
             tmp = line.split(" ")
             hostname = tmp[3]

packages/ns-api/files/ns.ha

@@ -83,6 +83,9 @@ def get_device_from_ip(uci, ipaddr):
             return (n, uci.get('network', n, 'device', default=None))
     return (None, None)
 
+def get_dhcp_leasefile(uci):
+    return uci.get('dhcp', 'ns_dnsmasq', 'dhcp', 'leasefile', default='/tmp/dhcp.leases')
+
 def get_main_vrrp_interface(uci):
     for section in utils.get_all_by_type(uci, 'keepalived', 'ipaddress'):
         if uci.get('keepalived', section, 'name', default=None) != 'lan_ha':
@@ -444,7 +447,7 @@ def init_local(role, primary_node_ip, backup_node_ip, virtual_ip, lan_interface,
         '/etc/adblock',
         '/etc/banip',
         '/etc/netifyd',
-        '/tmp/dhcp.leases',
+        get_dhcp_leasefile(u),
         '/var/ns-snort',
         '/tmp/banIP-backup',
         '/tmp/adblock-Backup'

packages/ns-storage/Makefile

@@ -6,7 +6,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=ns-storage
-PKG_VERSION:=1.0.1
+PKG_VERSION:=1.0.2
 PKG_RELEASE:=1
 
 PKG_BUILD_DIR:=$(BUILD_DIR)/ns-storage-$(PKG_VERSION)
@@ -62,6 +62,7 @@ define Package/ns-storage/install
 	$(INSTALL_BIN) ./files/ns-storage-setup-partition $(1)/usr/libexec
 	$(INSTALL_BIN) ./files/ns-storage-setup-disk $(1)/usr/libexec
 	$(INSTALL_BIN) ./files/ns-storage-has-free-space $(1)/usr/libexec
+	$(INSTALL_BIN) ./files/ns-storage-dhcp-leases $(1)/usr/libexec
 	$(INSTALL_BIN) ./files/remove-storage $(1)/usr/sbin
 	$(INSTALL_BIN) ./files/rotate-messages $(1)/usr/sbin
 	$(INSTALL_BIN) ./files/sync-data $(1)/usr/sbin

packages/ns-storage/README.md

@@ -10,6 +10,7 @@ Features:
 
 - device initialization and mounting
 - rsyslog configuration
+- dnsmasq DHCP lease persistence on mounted storage
 - logrotate for extra log files
 - customizable cron job to sync data once a day
 
@@ -66,8 +67,9 @@ add-storage /dev/sda
 The script will mount the storage at `/mnt/data` and configure
 the system as follow:
 
-- rsyslog will write logs also inside `/mnt/data/logs/messages` file
-- logrotate will rotate `/mnt/data/logs/messages` once a week (see `/etc/logrotate/data.conf` for more info)
+- rsyslog will write logs also inside `/mnt/data/log/messages` file
+- logrotate will rotate `/mnt/data/log/messages` once a week (see `/etc/logrotate/data.conf` for more info)
+- dnsmasq will store DHCP leases inside `/mnt/data/dnsmasq/dhcp.leases`; `/tmp/dhcp.leases` remains available as a compatibility symlink while the storage is mounted
 
 ### Storage status alert
 
@@ -91,3 +93,6 @@ To remove the data storage and restore in-memory log retention only, execute:
 ```
 remove-storage
 ```
+
+The `remove-storage` script switches dnsmasq back to `/tmp/dhcp.leases` before
+unmounting `/mnt/data`.

packages/ns-storage/files/add-storage

@@ -48,3 +48,6 @@ crontab -l | grep -q '/usr/sbin/sync-data' || echo '40 1 * * * /usr/sbin/sync-da
 
 # check for existing OpenVPN RW connection records in /var and merge them into storage if needed
 /usr/libexec/ns-openvpn/openvpn-merge-connections-db
+
+# Setup persistent dnsmasq leases file
+/usr/libexec/ns-storage-dhcp-leases

packages/ns-storage/files/ns-storage-check.init

@@ -26,6 +26,8 @@ storage_check()
     uci set rsyslog.ns_data.destination="/mnt/data/log/messages"
     uci commit rsyslog
   fi
+
+  /usr/libexec/ns-storage-dhcp-leases
 }
 
 boot()

packages/ns-storage/files/ns-storage-dhcp-leases

@@ -0,0 +1,49 @@
+#!/bin/sh
+#
+# Copyright (C) 2026 Nethesis S.r.l.
+# SPDX-License-Identifier: GPL-2.0-only
+#
+
+# This script is used to move the dnsmasq leases file between the storage and the tmpfs,
+# depending on the storage availability.
+
+TMP_LEASEFILE=/tmp/dhcp.leases
+STORAGE_TARGET=/mnt/data
+STORAGE_DIR=${STORAGE_TARGET}/dnsmasq
+STORAGE_LEASEFILE=${STORAGE_DIR}/dhcp.leases
+
+is_storage_mounted()
+{
+	awk -v target="${STORAGE_TARGET}" '$2 == target {found=1} END {exit !found}' /proc/mounts
+}
+
+get_current_leasefile()
+{
+	current="$(uci -q get dhcp.ns_dnsmasq.leasefile)"
+	if [ -n "${current}" ]; then
+		printf '%s\n' "${current}"
+	else
+		printf '%s\n' "${TMP_LEASEFILE}"
+	fi
+}
+
+current_leasefile="$(get_current_leasefile)"
+if is_storage_mounted; then
+	target_leasefile="${STORAGE_LEASEFILE}"
+else
+	target_leasefile="${TMP_LEASEFILE}"
+fi
+
+if  [ "${current_leasefile}" != "${target_leasefile}" ]; then
+	if [ "${current_leasefile}" = "${STORAGE_LEASEFILE}" ]; then
+		# From storage to tmp
+		cp -af "${STORAGE_LEASEFILE}" "${TMP_LEASEFILE}" || :
+	else
+		# From tmp to storage
+		mkdir -p "${STORAGE_DIR}"
+		cp -af "${TMP_LEASEFILE}" "${STORAGE_LEASEFILE}" || :
+	fi
+	uci set dhcp.ns_dnsmasq.leasefile="$target_leasefile"
+	uci commit dhcp
+	reload_config
+fi

packages/ns-storage/files/remove-storage

@@ -34,3 +34,6 @@ rm -rf /mnt/data
 if [ "$rom_disk" == "$data_disk" ]; then
     parted "/dev/${data_disk}" rm 3
 fi
+
+# Restore dnsmasq to /tmp before the storage disappears.
+/usr/libexec/ns-storage-dhcp-leases