Add PTR and NS Records to DNS Resolver possible?

Selo

I can tell this:

we are working on this issue with 2 experienced engineers. We have setup the 4 records as requested by the mobility print software.
nslookup confirms the 4 records are active and correct. After checking the records with the mobility software, we keep getting an error on the PTR records.
Fortunately we have an active Papercut license (it is a new install with 150 users), we created a support ticket…hope to get quick response.
If anyone has fixed this PTR issue, I would really like to see the DNS entries...
We also suggested a change to the mobility print client: a possibility to enter an ip-address instead of using the autodiscover option...

kolpinkb

Posting my named.conf file shortly for bind. Just obfuscating the IPs and domains.

Also, tech support was kind enough a few weeks ago to spend 2-3 hours on the phone with me to try an figure out the problem with unbound. I found something in Mobility Print's log files that may be of use.

Hold tight.

johnpoz

From what I recall the client was not looking for what they said to create on their website.. But I can till you for fact is that unbound can create PTR records…

Here is simple PTR query for IP on unbound... Answers just fine...


> dig -x 192.168.9.8

; <<>> DiG 9.11.2 <<>> -x 192.168.9.8
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 37198
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;8.9.168.192.in-addr.arpa.      IN      PTR

;; ANSWER SECTION:
8.9.168.192.in-addr.arpa. 1635  IN      PTR     Storage.local.lan.

;; Query time: 9 msec
;; SERVER: 192.168.3.10#53(192.168.3.10)
;; WHEN: Tue Jan 16 11:31:45 Central Standard Time 2018
;; MSG SIZE  rcvd: 84

What exactly is going to be queried and what should be the answer and we can validate whatever that something is can be entered into unbound. But 100% for sure unbound can answer for a PTR query.

Selo

OK, let´s wait for the named.conf file thehammer86 was going to post…
Also curious about this: "I found something in Mobility Print's log files that may be of use."

johnpoz

I played with this for a bit - I could never get the client to actually do a ptr query like they said it should.. Their docs from what I remember are not very clear. My trial ran out and attempted to run the mobility client on the same box the server was run on.

I could try to setup it up again on some other machines - But once we know what actual query be it PTR or some other we can work out how to setup (if possible) for unbound to respond. What I can tell you for 100% fact is the unbound can respond with a PTR… And NS records, so there is something missing in the puzzle here.

kolpinkb

Here's the relevent config from a bare-metal machine I installed bind9 on. Please make sure the domain and search list your dhcp server is handing out matches your domain for the mobility print entries. Three different files below:
/etc/bind/named.conf

options {
directory "/etc/bind";
pid-file "/var/run/bind/run/named.pid /var/run/named.pid /var/run/named/named.pid /var/run/bind/run/named/named.pid";
forwarders {
208.67.220.220;
208.67.222.222;
2620:0:ccd::2;
2620:0:ccc::2;
};
forward first;
allow-query {
192.168.0.0/16;
};
};

zone "." {
type hint;
file "/etc/bind/db.cache";
};

zone "168.192.in-addr.arpa" {
type master;
file "/var/lib/bind/192.168.rev";
};
key rndc-key {
algorithm hmac-md5;
secret "XXXXXXXXXXXXXXXXXXXXXX==";
};
controls {
inet 127.0.0.1 port 953 allow { 127.0.0.1; } keys { rndc-key; };
};
zone "example.com" {
type master;
file "/var/lib/bind/example.com.hosts";
};

/var/lib/bind/192.168.rev

168.192.in-addr.arpa. IN SOA cloud1.example.com. admin.example.com. (
1513635071
10800
3600
604800
38400 )
168.192.in-addr.arpa. IN NS cloud1.example.com.
3.71.168.192.in-addr.arpa. IN PTR cloud5.example.com.

/var/lib/bind/example.com.hosts

$ttl 38400
example.com. IN SOA cloud1.example.com. admin.example.com. (
1513706509
10800
3600
604800
38400 )
example.com. IN NS cloud1.example.com.
cloud5.example.com. IN A 192.168.71.3
cloud1.example.com. IN A 192.168.71.4
pc-printer-discovery.example.com. IN NS cloud5.example.com.
b._dns-sd._udp.example.com. IN PTR pc-printer-discovery.example.com.
lb._dns-sd._udp.example.com. IN PTR pc-printer-discovery.example.com.

johnpoz

Problem with that config is that your SOA for example.com is cloud1.example.com

But I take it cloud5 is the mobility server but its a example.com domain ns, so do cloud1 and cloud5 the NS for example.com have the same records?

What does pc-printer-discovery.example.com. actually resolve too? Since from your config I should be able to answer either cloud1 the SOA for example.com or cloud5 for this A record.

kolpinkb

Both PaperCutNG and the MobilityPrint Server are on the same machine (cloud5). I can't seem to track down the log entry from MobilityPrint but its starting to come back to me now. Something about the log error hinted at a permission issue with Unbound. Because Unbound is set up as an authoritative name server for example.com, it didn't like cloud5.example.com being an authoritative name server for the subdomain pc-printer-discovery.example.com.

Does that help?

I coundn't get any further with unbound so that's why I ditched it and went to bind.

johnpoz

and when you do a query for pc-printer-discovery.example.com, is this a A record query TXT, SRV what?

Seems pretty pointless to set it up that way.. Why could you not just setup pc-printer-discovery.example.com to be resolved by unbound directly? Be it A record or TXT or SRV, etc. Seems stupid to do it that way.. I see no point to it.

Actually goes against dns practice to delegate like that. Why sure pc-printer-discovery.example.com could be sub domain and delegated to a different NS. you would then look fror something like host.pc-printer-discovery.example.com in the subdomain.

Unbound is not actually meant to be an authoritative NS.. So that is prob why there are some issues - but you could for sure just put in the entry for pc-printer-discovery.example.com directly in unbound so it could resolve it without having to delegate that to cloud5..

Unbound is a validating, recursive, and caching DNS resolver. It is not actually meant to be an authoritative NS… While it can answer specific records, from a local database - it has issues with cnames as well, etc. Since its not actual designed to be an authoritative NS.

But if the client wants to do a PTR query and then a query for that fqdn that is returned it for sure could answer a A, TXT, SRV record etc... for the actual fqdn that gets queried.

Selo

I just got feedback from Papercut support:

"
(PaperCut)

I apologize but presently we don't have a documented method to set up the DNS records for Mobility Print using Unbound with PFSense. However, I do want to point out that other customers with PFsense routers that want to use DNS Discovery for Mobility Print have reached out to us to see if this is something that can be achieved. I previously created a to-do item in our feature tracking system for our developers to take a look at whether this is feasible. I have also linked this support ticket to the feature request so that we can notify you by email in the future if this is something we are able to document. I can't say when we would be able to answer this however.

In the short term I would also like to point out that there are several other methods for setting up Mobility Print, even for environments with multiple subnets and VLANs. For example, you can connect multiple network interfaces to your Mobility Print server and allow it to broadcast mDNS to advertise printers to clients in each network. Alternatively if your router supports Bonjour Forwarding, then you could set it up to allow mDNS traffic to pass from your server VLAN to your client VLANs.

Let me know if you have any questions at all or if you would like to discuss some of the alternate methods I mentioned above.

"

johnpoz

You could most likely just use the avahi package with pfsense.. It does mDNS/DNS-SD

Derelict

DNS Resolver Custom Options:

server:
local-zone: "example.com." transparent
local-data: "b.dns-sd._udp IN PTR pc-printer-discovery.example.com."
local-data: "lb.dns-sd._udp IN PTR pc-printer-discovery.example.com."
local-data: "pc-printer-discovery.example.com. IN NS print-server-host.example.com."
local-data: "print-server-host.example.com. IN A 192.168.224.17"

Test queries:

[2.4.2-RELEASE][root@pfSense-b.example.com]/var/unbound: dig +short +search +domain=example.com @localhost PTR b.dns-sd._udp
pc-printer-discovery.example.com.
[2.4.2-RELEASE][root@pfSense-b.example.com]/var/unbound: dig +short +search +domain=example.com @localhost PTR lb.dns-sd._udp
pc-printer-discovery.example.com.
[2.4.2-RELEASE][root@pfSense-b.example.com]/var/unbound: dig +short +search +domain=example.com @localhost NS pc-printer-discovery
print-server-host.example.com.
[2.4.2-RELEASE][root@pfSense-b.example.com]/var/unbound: dig +short +search +domain=example.com @localhost A print-server-host
192.168.224.17

From there it is up to the client to ask the DNS server on the mobility print server at 192.168.224.17 whatever it needs to ask about the pc-printer-discovery zone.

It looks to me like this should work. It implies the client is pointed EXCLUSIVELY at unbound (and/or a similarly-configured server) and has a correct search domain set for "example.com".

I did not try to get a Mobility Print environment working.

Derelict

Note that unbound agrees with my prior assessment of the wackiness of the name-keyed PTR records. They have a local-data-ptr option for setting PTR records:

local-data-ptr: "IPaddr name"
Configure local data shorthand for a PTR record with the reversed
IPv4 or IPv6 address and the host name. For example "192.0.2.4
www.example.com". TTL can be inserted like this: "2001:DB8::4
7200 www.example.com"

If you try something like:

local-data-ptr: "b.dns-sd._udp pc-printer-discovery.example.com."

It barfs with:

The generated config file cannot be parsed by unbound. Please correct the following errors:
[1516213033] unbound-checkconf[27521:0] error: syntax error: cannot parse address: b.dns-sd._udp pc-printer-discovery.example.com.
/var/unbound/test/unbound.conf:86: error: local-data-ptr could not be reversed
read /var/unbound/test/unbound.conf failed: 1 errors in configuration file

johnpoz

Where the problem is I do not believe the client follows through with looking up pc-printer-discovery.example.com.

When NS is authoritative its different - same issue with a cname in unbound. You can for sure put in a cname record.. But it doesn't follow through and finish, its up the client to follow the query when the not using authoritative ns, etc.

If the client actually does a query for pc-printer-discovery.example.com. you could just put that record in unbound directly..

Derelict

It looks to me like pc-printer-discovery.example.com is a subdomain. Those records/that zone will be found on the mobility print server itself.

At least that's what it looks like to me.

I am really not in the mood to install it and see.

It looks like the above config is what is necessary to get the records papercut say need to be there in there.

johnpoz

"It looks like the above config is what is necessary to get the records papercut say need to be there in there."

Yeah went through that while back - doesn't work, because yes pc-printer-discovery.example.com is a subdomain delegation… Its hokey setup to be sure.. Trying to put these records into unbound make no sense at all.. The whole thing is designed for the authoritative NS for the domain in question which is not what unbound running on pfsense is

http://www.dns-sd.org/serverstaticsetup.html

You really should be able to get away with a domain override for the domain

_dns-sd._udp.example.com

Point _dns-sd._udp.example.com via NS record to the mobility print server let the client do whatever it wants via a domain override.

I would think it just much easier to setup avahi..

If user really wants to use this setup and run it on pfsense, then they should be using the bind package that gives them full authoritative nameserver software on pfsense - with a gui to boot to manage ;)

kolpinkb

Unfortunately, I already tried avahi. The mobility app under android and windows returns an error that I haven't been able to sort out with the Paperacut team.

Derelict

Then pcap the DNS traffic and see where the breakdown is.

johnpoz

Can for sure make unbound answer pretty much anything that gets queried for.. But its not going to do some of the stuff an actual authoritative NS does for a zone its authoritative for, etc.

If you do a sniff and see what is queried - pretty freaking sure can make unbound answer with the answer you want for the specific query and type.

Selo

I can confirm Avahi is not working. Just tested it.
The mobility print setup does not find any printers in another VLAN.