Hi all,

I'm running on OpenWRT (SNAPSHOT r23935+13-c1206675a4) which has installed
dnsmasq 2.89 and my client is a macbook running MacOS 12.3.1 and I recently
switched from a single dnsmasq instance to a multi-instance dnsmasq setup
(because i wanted a different subdomain name given for the different
networks i have dnsmasq listen on and that was the approach suggested in
openwrt forum),

But when i performed this change, i found out (after many days of
troubleshooting) that the dhcp response no longer contained a subnet-mask
field (which was causing my client to use the default /16 for a classful
CIDR of that address space, which caused connectivity issues that were
hilariously baffling at first).

Is there some bug here, or am I doing something wrong?

Attaching both the single-instance dnsmasq.conf (working) and the DHCPOFFER
response as well as the offending instance in the multi-instance
dnsmasq.conf (broken) and the DHCPOFFER response, where the subnet-mask
option is omitted (despite me attempting to add it as an extra DHCPOPTION
#1 even!)

Any advice or anything else to look at?

Warm regards,
Aleks
13:44:46.064691 60:38:e0:xx:xx:10 > 8c:ae:4c:xx:xx:20, ethertype IPv4 (0x0800), 
length 373: (tos 0xc0, ttl 64, id 39706, offset 0, flags [none], proto UDP 
(17), length 359)
    172.22.20.1.67 > 172.22.20.20.68: [udp sum ok] BOOTP/DHCP, Reply, length 
331, xid 0x8d7469d9, Flags [none] (0x0000)
          Your-IP 172.22.20.20
          Server-IP 172.22.20.1
          Client-Ethernet-Address 8c:ae:4c:xx:xx:20
          Vendor-rfc1048 Extensions
            Magic Cookie 0x63825363
            DHCP-Message Option 53, length 1: Offer
            Server-ID Option 54, length 4: 172.22.20.1
            Lease-Time Option 51, length 4: 120
            RN Option 58, length 4: 60
            RB Option 59, length 4: 105
            BR Option 28, length 4: 172.22.20.255
            Default-Gateway Option 3, length 4: 172.22.20.1
            Domain-Name-Server Option 6, length 4: 172.22.20.1
            T119 Option 119, length 25: 3.108.97.110.4.104.111....
            Domain-Name Option 15, length 16: "lan.home.my.domain"
            END Option 255, length 0
root@router-main:/etc/config# ls -l /tmp/etc/dnsmasq.conf.*
-rw-r--r--    1 root     root          1107 Sep 19 10:48 
/tmp/etc/dnsmasq.conf.home_dns
-rw-r--r--    1 root     root          1110 Sep 19 10:48 
/tmp/etc/dnsmasq.conf.lan_dns
-rw-r--r--    1 root     root          1004 Sep 19 10:48 
/tmp/etc/dnsmasq.conf.mgmt_dns
root@router-main:/etc/config# cat /tmp/etc/dnsmasq.conf.lan_dns
# auto-generated config file from /etc/config/dhcp
conf-file=/etc/dnsmasq.conf
dhcp-authoritative
domain-needed
localise-queries
read-ethers
enable-ubus=dnsmasq.lan_dns
expand-hosts
bind-dynamic
local-service
cache-size=1000
domain=lan.home.my.domain
local=/lan.home.my.domain/
server=208.67.222.222
server=208.67.220.220
interface=br-lan.2220
except-interface=lo
addn-hosts=/tmp/hosts
dhcp-leasefile=/tmp/dhcp.leases.lan
resolv-file=/tmp/resolv.conf.d/resolv.conf.auto
stop-dns-rebind
rebind-localhost-ok
rebind-domain-ok=/my.domain/
dhcp-broadcast=tag:needs-broadcast
conf-dir=/tmp/dnsmasq.d
user=dnsmasq
group=dnsmasq

dhcp-host=8C:AE:4C:xx:xx:20,172.22.20.20,aleksWorkMBP-docked,2m

dhcp-ignore-names=tag:dhcp_bogus_hostname
conf-file=/usr/share/dnsmasq/dhcpbogushostname.conf

bogus-priv
conf-file=/usr/share/dnsmasq/rfc6761.conf
dhcp-range=set:lan,172.22.20.100,172.22.20.249,255.255.255.0,2m
dhcp-option=lan,1,255.255.255.0
dhcp-option=lan,15,lan.home.my.domain
dhcp-option=lan,119,lan.home.my.domain,mgmt.home.my.domain
dhcp-option-force=lan,1


## note the other two dnsmasq.conf look the same except lan.home.my.domain is
##   replaced with wifi.home.my.domain and mgmt.home.my.domain
## and networks there are 172.20.20.0/23 and 172.22.22.20/30 respectively
13:47:22.335169 60:38:e0:xx:xx:10 > 8c:ae:4c:xx:xx:20, ethertype IPv4 (0x0800), 
length 342: (tos 0xc0, ttl 64, id 8592, offset 0, flags [none], proto UDP (17), 
length 328)
    172.22.20.1.67 > 172.22.20.20.68: [udp sum ok] BOOTP/DHCP, Reply, length 
300, xid 0x8d7469db, secs 35, Flags [none] (0x0000)
          Your-IP 172.22.20.20
          Server-IP 172.22.20.1
          Client-Ethernet-Address 8c:ae:4c:xx:xx:20
          Vendor-rfc1048 Extensions
            Magic Cookie 0x63825363
            DHCP-Message Option 53, length 1: Offer
            Server-ID Option 54, length 4: 172.22.20.1
            Lease-Time Option 51, length 4: 43200
            RN Option 58, length 4: 21600
            RB Option 59, length 4: 37800
            Subnet-Mask Option 1, length 4: 255.255.255.0
            BR Option 28, length 4: 172.22.20.255
            Default-Gateway Option 3, length 4: 172.22.20.1
            Domain-Name-Server Option 6, length 4: 172.22.20.1
            Domain-Name Option 15, length 3: "lan"
            END Option 255, length 0
            PAD Option 0, length 0, occurs 3
root@router-main:/tmp/etc# cat dnsmasq.conf.cfg01411c
# auto-generated config file from /etc/config/dhcp
conf-file=/etc/dnsmasq.conf
dhcp-authoritative
domain-needed
localise-queries
read-ethers
enable-ubus=dnsmasq
expand-hosts
bind-dynamic
local-service
cache-size=1000
edns-packet-max=1232
domain=lan
local=/lan/
interface=br-lan.2222
interface=br-lan.2220
interface=br-lan.2020
addn-hosts=/tmp/hosts
dhcp-leasefile=/tmp/dhcp.leases
resolv-file=/tmp/resolv.conf.d/resolv.conf.auto
stop-dns-rebind
rebind-localhost-ok
dhcp-broadcast=tag:needs-broadcast
conf-dir=/tmp/dnsmasq.d
user=dnsmasq
group=dnsmasq

dhcp-host=8C:AE:4C:XX:XX:20,172.22.20.21,aleksWorkMBP-docked

dhcp-ignore-names=tag:dhcp_bogus_hostname
conf-file=/usr/share/dnsmasq/dhcpbogushostname.conf

bogus-priv
conf-file=/usr/share/dnsmasq/rfc6761.conf
no-dhcp-interface=pppoe-wan
dhcp-range=set:mgmt,172.22.22.21,172.22.22.21,255.255.255.252,12h
dhcp-range=set:lan,172.22.20.100,172.22.20.249,255.255.255.0,12h
dhcp-range=set:home,172.20.20.100,172.20.20.249,255.255.254.0,12h
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