Dnsmasq respawning, xrx200 errors, and openwrt 21.02.0

Had an odd problem last night, dnsmasq stopped giving out addresses via dhcp - its never done this before, and only recently updated to 21.02.0.

The only error given in the log is daemon.err dnsmasq[5643]: failed to load names from /tmp/hosts/dhcp.cfg01411c: Permission denied where that file is rw by root only, and it exists.

The only other error is the very strange kern.warn kernel: [ 5626.058224] enter showtime, cell rate: 0 - 2094, 1 - 2094, xdata addr: 0xa1cf0000 - a google search don't show this as connected. Its an error that only happens on xrx200 devices, and quite often with plus.net - both of which apply to me.

Anyway strange with with dnsmasq, is after a few hours it settled down, and started giving out ip numbers. The ADSL line kept on going up and down over night.

Anyone any ideas?

It shouldn't be root-only.
Dnsmasq is supposed to run under a restricted user.
You haven't altered the init script, have you?

Now that dhcp is working again. The file is still rw for root only, and as its in /tmp its a file that is created on the fly - and by the date on the file, it must been soon after poweron. No I've changed no scripts - only removed /etc/modules.d/ipt-nat - as I do firewall via nftables.

Do you know which script creates the file?

The exact config location and processing method depends on your firmware version and settings:

It looks like this for me:

# ls -a -l /tmp/hosts
drwxr-xr-x    2 root     root            80 Sep 11 07:32 .
drwxrwxrwt   21 root     root           600 Sep 11 09:35 ..
-rw-r--r--    1 root     root            51 Sep 10 16:28 dhcp.dnsmasq
-rw-r--r--    1 root     root             0 Sep 11 07:32 odhcpd

# ps | grep -e [d]nsmasq -e [o]dhcpd
 2097 dnsmasq   2316 S    /usr/sbin/dnsmasq -C /var/etc/dnsmasq.conf.dnsmasq -k -x /var/run/dnsmasq/dnsmasq.dnsmasq.pid
 2348 root      1068 S    /usr/sbin/odhcpd

# ubus call system board
	"kernel": "5.4.143",
	"hostname": "openwrt1",
	"system": "Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz",
	"model": "QEMU Standard PC (i440FX + PIIX, 1996)",
	"board_name": "qemu-standard-pc-i440fx-piix-1996",
	"release": {
		"distribution": "OpenWrt",
		"version": "21.02.0",
		"revision": "r16279-5cc0535800",
		"target": "x86/64",
		"description": "OpenWrt 21.02.0 r16279-5cc0535800"