[openwrt/openwrt] dnsmasq: fix start if dhcp-range is not correct

[LEDE Commits]

hauke pushed a commit to openwrt/openwrt.git, branch main:
https://git.openwrt.org/ae198c6ba08542d7eaca41103ee86d6794039ffc

commit ae198c6ba08542d7eaca41103ee86d6794039ffc
Author: Florian Eckert <fe at dev.tdt.de>
AuthorDate: Tue Apr 29 15:26:36 2025 +0200

    dnsmasq: fix start if dhcp-range is not correct
    
    If the uci 'dhcp' configuration for the dhcp leases is incorrect then
    the call to 'ipclac' fails. However, the problem is that the dnsmasq
    configuration option 'dhcp-range' is still written for this uci section
    even though the information generated by ipcalc is incorrect or not set.
    
    Due to the incorrectly generated configuration for dnsmasq, the service
    cannot start.
    
    To prevent an incorrect configuration from being written to the configuration,
    a check is now made beforehand to ensure that the required variables are
    present and valid. If the configuration is incorrect, a message is emitted
    to the log that this configuration section is incorrect and this uci
    configuration section is omitted.
    
    Signed-off-by: Florian Eckert <fe at dev.tdt.de>
    Link: https://github.com/openwrt/openwrt/pull/18641
    Signed-off-by: Hauke Mehrtens <hauke at hauke-m.de>
---
 package/network/services/dnsmasq/Makefile           |  2 +-
 package/network/services/dnsmasq/files/dnsmasq.init | 18 ++++++++++++++----
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/package/network/services/dnsmasq/Makefile b/package/network/services/dnsmasq/Makefile
index 5290f1e468..6b9853e5ff 100644
--- a/package/network/services/dnsmasq/Makefile
+++ b/package/network/services/dnsmasq/Makefile
@@ -10,7 +10,7 @@ include $(TOPDIR)/rules.mk
 PKG_NAME:=dnsmasq
 PKG_UPSTREAM_VERSION:=2.91
 PKG_VERSION:=$(subst test,~~test,$(subst rc,~rc,$(PKG_UPSTREAM_VERSION)))
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_UPSTREAM_VERSION).tar.xz
 PKG_SOURCE_URL:=https://thekelleys.org.uk/dnsmasq/
diff --git a/package/network/services/dnsmasq/files/dnsmasq.init b/package/network/services/dnsmasq/files/dnsmasq.init
index 8258bcc3f4..a0a644fcbd 100755
--- a/package/network/services/dnsmasq/files/dnsmasq.init
+++ b/package/network/services/dnsmasq/files/dnsmasq.init
@@ -597,10 +597,20 @@ dhcp_add() {
 	nettag="${networkid:+set:${networkid},}"
 
 	# make sure the DHCP range is not empty
-	if [ "$dhcpv4" != "disabled" ] && ipcalc "$ipaddr/$prefix_or_netmask" "$start" "$limit" ; then
-		[ "$dynamicdhcpv4" = "0" ] && END="static"
-
-		xappend "--dhcp-range=$tags$nettag$START,$END,$NETMASK,$leasetime${options:+ $options}"
+	if [ "$dhcpv4" != "disabled" ]; then
+		unset START
+		unset END
+		unset NETMASK
+		ipcalc "$ipaddr/$prefix_or_netmask" "$start" "$limit"
+
+		if [ -z "$START" ] || [ -z "$END" ] || [ -z "$NETMASK" ]; then
+			logger -t dnsmasq \
+				"unable to set dhcp-range for dhcp uci config section '$cfg'" \
+				"on interface '$ifname', please check your config"
+		else
+			[ "$dynamicdhcpv4" = "0" ] && END="static"
+			xappend "--dhcp-range=$tags$nettag$START,$END,$NETMASK,$leasetime${options:+ $options}"
+		fi
 	fi
 
 	if [ "$dynamicdhcpv6" = "0" ] ; then