[Dnsmasq-discuss] make synth-domain a authoritative response

Markus Hartung

2018-03-04 22:39:09 UTC

Hello guys,

I have my own domain and have a Hurricane Electric ipv6 block.

I get working reverse-lookups for my hosts that dnsmasq knows about.
DHCP, RA, hard-coded etc.

However I want non-existing hosts to get a generated hostname using the
synth-domain option.
The reason is that I want to have working hostnames for the temporary
IPv6-addresses my hosts uses.

I'm using this config:
synth-domain=hartmark.se,2001:470:28:6ac::/64,dynamic-

And a lookup on a IPv6-address using localhost gives me this response:

======================================
$ dig -x 2001:470:28:6ac:a634:d9ff:fe7e:6c5a

; <<>> DiG 9.10.3-P4-Ubuntu <<>> -x 2001:470:28:6ac:a634:d9ff:fe7e:6c5a
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 27613
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;a.5.c.6.e.7.e.f.f.f.9.d.4.3.6.a.c.a.6.0.8.2.0.0.0.7.4.0.1.0.0.2.ip6.arpa.
IN PTR

;; ANSWER SECTION:
a.5.c.6.e.7.e.f.f.f.9.d.4.3.6.a.c.a.6.0.8.2.0.0.0.7.4.0.1.0.0.2.ip6.arpa.
300 IN PTR dynamic-2001-470-28-6ac-a634-d9ff-fe7e-6c5a.hartmark.se.

;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Sun Mar 04 23:05:20 CET 2018
;; MSG SIZEÂ rcvd: 170
======================================

As you can see I get the expected dynamic-xxx.hartmark.se hostname.

And if I ask on my dns-server's IPv4 address I get same result, however
I I ask on my IPv6-address I get this result:
======================================
dig -x 2001:470:28:6ac:a634:d9ff:fe7e:6c5a @ns1.hartmark.se

; <<>> DiG 9.10.3-P4-Ubuntu <<>> -x 2001:470:28:6ac:a634:d9ff:fe7e:6c5a
@ns1.hartmark.se
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 58272
;; flags: qr aa rd ad; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;a.5.c.6.e.7.e.f.f.f.9.d.4.3.6.a.c.a.6.0.8.2.0.0.0.7.4.0.1.0.0.2.ip6.arpa.
IN PTR

;; AUTHORITY SECTION:
c.a.6.0.8.2.0.0.0.7.4.0.1.0.0.2.ip6.arpa. 300 IN SOA ns1.hartmark.se.
hostmaster.hartmark.se. 1520127368 1200 180 1209600 300

;; Query time: 0 msec
;; SERVER: 2001:470:28:6ac::2#53(2001:470:28:6ac::2)
;; WHEN: Sun Mar 04 23:14:50 CET 2018
;; MSG SIZEÂ rcvd: 214
======================================

I'm no DNS-ninja but it seems the IPv6 response is NXDOMAIN and the IPv4
response have NOERROR. The curious thing is that they are both flagged
with aa (/AA/ = Authoritative Answer).

dnsmasq for IPv4 and IPv6 is the same process on the machine:
tcpÂ Â Â Â Â Â Â 0Â Â Â Â Â 0 0.0.0.0:53 0.0.0.0:*Â Â Â Â Â Â Â Â Â Â Â Â Â Â LISTENÂ Â Â Â Â
18236/dnsmasq
tcp6Â Â Â Â Â Â 0Â Â Â Â Â 0 :::53 :::*Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â LISTENÂ Â Â Â Â 18236/dnsmasq
udpÂ Â Â Â Â Â Â 0Â Â Â Â Â 0 0.0.0.0:53 0.0.0.0:*Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
18236/dnsmasq
udp6Â Â Â Â Â Â 0Â Â Â Â Â 0 :::53 :::*Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 18236/dnsmasq

Is there anything I have missed?
ns1.hartmark.se is the delegated authority for the /64 from Hurricane
Electric.

$ dnsmasq -version
Dnsmasq version 2.78Â Copyright (c) 2000-2017 Simon Kelley
Compile time options: IPv6 GNU-getopt DBus i18n IDN DHCP DHCPv6 no-Lua
TFTP conntrack ipset auth DNSSEC loop-detect inotify

Running on a ubuntu 17.10.

BR,
/ Harre