[Dnsmasq-discuss] Regarding: dnsmasq "dynamic-hosts" ignores /16 IPv4 addresses on interfaces entirely

Sun Oct 9 18:39:34 UTC 2022

Sooo, it turns out "Reply" does not seem to work, at least not with my E-Mail client to send the reply to the mailing list. Sorry about that.

Either way, manually sending it to the actual list:

Sure, makes sense. Especially as this problem is way more complex than I initially anticipated and I no longer understand why dnsmasq acts like it does.

With the following configuration (localise queries is enabled and the configuration is identical between the below 3 test cases):

dynamic-host=ntp.foxden.network,0.0.0.123,br-lan.1
dynamic-host=ntp.foxden.network,0.0.0.123,br-lan.2
dynamic-host=ntp.foxden.network,0.0.0.123,br-lan.3
dynamic-host=ntp.foxden.network,0.0.0.123,br-lan.4
dynamic-host=ntp.foxden.network,0.0.0.123,br-lan.5
dynamic-host=ntp.foxden.network,0.0.0.123,br-lan.6

The below 10.2.0.1 and 10.2.0.53 IPs are assigned via VRRP (by keepalived)
As can be seen, the setup only works if keepalived assigns /24 addresses for reasons I do not understand.

First, the working setup with /24 (correctly gives 10.2.0.123):

server# ip -4 addr show dev br-lan.2
14: br-lan.2 at br-lan: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc noqueue state UP group default qlen 1000
inet 10.2.1.1/16 brd 10.2.255.255 scope global br-lan.2
valid_lft forever preferred_lft forever
inet 10.2.0.1/24 scope global br-lan.2
valid_lft forever preferred_lft forever
inet 10.2.0.53/24 scope global secondary br-lan.2
valid_lft forever preferred_lft forever

client$ dig ntp.foxden.network @10.2.1.1

; <<>> DiG 9.10.6 <<>> ntp.foxden.network @10.2.1.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 57054
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;ntp.foxden.network. IN A

;; ANSWER SECTION:
ntp.foxden.network. 0 IN A 10.2.0.123

;; Query time: 0 msec
;; SERVER: 10.2.1.1#53(10.2.1.1)
;; WHEN: Sun Oct 09 11:31:08 PDT 2022
;; MSG SIZE rcvd: 63

SERVER logs:
Sun Oct 9 11:31:08 2022 daemon.info dnsmasq[1]: query[A] ntp.foxden.network from 10.2.10.4
Sun Oct 9 11:31:08 2022 daemon.info dnsmasq[1]: config ntp.foxden.network is 10.2.0.123

Non-working setup with /32:

server# ip -4 addr show dev br-lan.2
14: br-lan.2 at br-lan: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc noqueue state UP group default qlen 1000
inet 10.2.1.1/16 brd 10.2.255.255 scope global br-lan.2
valid_lft forever preferred_lft forever
inet 10.2.0.1/32 scope global br-lan.2
valid_lft forever preferred_lft forever
inet 10.2.0.53/32 scope global br-lan.2
valid_lft forever preferred_lft forever

client$ dig ntp.foxden.network @10.2.1.1

; <<>> DiG 9.10.6 <<>> ntp.foxden.network @10.2.1.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 16255
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;ntp.foxden.network. IN A

;; ANSWER SECTION:
ntp.foxden.network. 0 IN A 10.2.0.53
ntp.foxden.network. 0 IN A 10.2.0.1

;; Query time: 0 msec
;; SERVER: 10.2.1.1#53(10.2.1.1)
;; WHEN: Sun Oct 09 11:29:26 PDT 2022
;; MSG SIZE rcvd: 79

SERVER logs:
Sun Oct 9 11:29:26 2022 daemon.info dnsmasq[1]: query[A] ntp.foxden.network from 10.2.10.4
Sun Oct 9 11:29:26 2022 daemon.info dnsmasq[1]: config ntp.foxden.network is 10.2.0.53
Sun Oct 9 11:29:26 2022 daemon.info dnsmasq[1]: config ntp.foxden.network is 10.2.0.1

Non-working setup with /16:

server# ip -4 addr show dev br-lan.2
14: br-lan.2 at br-lan: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc noqueue state UP group default qlen 1000
inet 10.2.1.1/16 brd 10.2.255.255 scope global br-lan.2
valid_lft forever preferred_lft forever
inet 10.2.0.1/16 scope global secondary br-lan.2
valid_lft forever preferred_lft forever
inet 10.2.0.53/16 scope global secondary br-lan.2
valid_lft forever preferred_lft forever

client$ dig ntp.foxden.network @10.2.1.1

; <<>> DiG 9.10.6 <<>> ntp.foxden.network @10.2.1.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 15647
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;ntp.foxden.network. IN A

;; Query time: 0 msec
;; SERVER: 10.2.1.1#53(10.2.1.1)
;; WHEN: Sun Oct 09 11:33:20 PDT 2022
;; MSG SIZE rcvd: 47

SERVER logs:
Sun Oct 9 11:33:20 2022 daemon.info dnsmasq[1]: query[A] ntp.foxden.network from 10.2.10.4
Sun Oct 9 11:33:20 2022 daemon.info dnsmasq[1]: config ntp.foxden.network is NODATA-IPv4

On Sun, Oct 9, 2022, at 01:07, Geert Stappers wrote:
> On Sat, Oct 08, 2022 at 06:48:03PM -0700, Mark Dietzer wrote:
> > It seems dnsmasq does not work with  ....
>      ....
> > 
> > Sorry if this reads a bit weirdly,
> > this is my first time ever posting on a mailing list.
> 
> We all start as beginner.
> No need to say sorry for that.
> 
> That you are not aware of an archive of the mailinglist
>  https://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/
> and missed
>  https://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2022q4/016606.html
> is something you have to deal with.
> 
> 
> No hard feelings, welcome to the dnsmasq mailinglist.
>  
> 
> > Regards,
> > Mark "Doridian" Dietzer
> 
> Groeten
> Geert Stappers
> -- 
> Silence is hard to parse
> 