DNS Resolver

jbc

I am probably misguided, admittedly, I am not an expect on these matters,
but what is the problem with dnscrypt used in conjuction with DNSSEC,
as far as I see, they solve different issues…

Look at #3: What about DNSSEC? Does this eliminate the need for DNSSEC?

https://www.opendns.com/about/innovations/dnscrypt/

And again, I actually don't want to use opendns, but dnscrypt.eu.

doktornotor

@dstroot:

@ doktornotor: "If you want DNSSEC, do not use OpenDNS."

OK - do you have a recommendation what to use?

If you are using the DNS censorship features from OpenDNS, I have no suggestions. :P Unbound is just fine as DNSSEC-validating recursive resolver, without any need for forwarding anywhere.

@jbc:

but what is the problem with dnscrypt used in conjuction with DNSSEC,
Look at #3: What about DNSSEC? Does this eliminate the need for DNSSEC?
https://www.opendns.com/about/innovations/dnscrypt/

You cannot use OpenDNS servers for DNSSEC validation. They don't validate anything.


>nslookup www.dnssec-failed.org 8.8.4.4
Server:  google-public-dns-b.google.com
Address:  8.8.4.4

*** google-public-dns-b.google.com can't find www.dnssec-failed.org: Server failed

>nslookup www.dnssec-failed.org 208.67.222.222
Server:  resolver1.opendns.com
Address:  208.67.222.222

Non-authoritative answer:
Name:    www.dnssec-failed.org
Addresses:  68.87.109.242
          69.252.193.191

jbc

@doktornotor:

I see, thank you for clearing that up :)

edit:
Incase someone stumbles across this, here is a list of free dnscrypt servers;
Column 8 notes if they support DNSSEC or not.

https://github.com/jedisct1/dnscrypt-proxy/blob/master/dnscrypt-resolvers.csv

mir

For a censor free and no logging DNS service which supports DNSSEC I can recommend this:
http://www.censurfridns.dk/

dstroot

Maybe everyone already knows this but there is not a whole lot of config advice I can find here. So I thought I'd share what I have figured out.

It seems you should really only use DNDSEC if you are using unbound as a recursive resolver (which is pretty slow if you are hitting a site for a first time). Otherwise all is good.

Otherwise turn DNSSEC off if you you are just using it as a forwarder because it's unlikely to be doing anything with OpenDNS (particularly with Google DNS since that seems to cause issues with unbound if you have it on).

From this site: https://calomel.org/unbound_dns.html


  # If you use forward-zone below to query the Google DNS servers you MUST comment out 
  # this option or all DNS queries will fail:
  # auto-trust-anchor-file: "/var/unbound/etc/root.key"

In either configuration, recursive or forwarder, it will cache DNS entries so subsequent requests are very fast.

Hope this helps someone.

cmb

@dstroot:

It seems you should really only use DNDSEC if you are using unbound as a recursive resolver (which is pretty slow if you are hitting a site for a first time). Otherwise all is good.

Otherwise turn DNSSEC off if you you are just using it as a forwarder because it's unlikely to be doing anything with OpenDNS (particularly with Google DNS since that seems to cause issues with unbound if you have it on).

Only use it in forwarder mode if your configured servers for forwarding support DNSSEC. Google's public DNS is fine there, OpenDNS apparently isn't.

In many situations there won't be much if any difference in query response time between recursive and forwarder. Depends on how much latency between you and that domain's NSes, how much latency there is between you and your forwarders, and whether or not the forwarders have it cached.

cmb

@cmb:

@NobodyHere:

We're running the December 10th build. I can confirm issues with a new WAN address breaking unbound. When our PPPoE WAN link gets a new IP address, the resolver will reply with internal IPs set via DHCP clientIDs, but any external DNS lookup made via a system on the LAN fails.

DNS resolving on the firewall continues to work, so it's clearly an issue with unbound.

https://redmine.pfsense.org/issues/4095

The above referenced issue should be fixed. Those who were seeing that, please try on the 31st or newer snapshot.

firewalluser

Since going with the new resolver (unbound) instead of the forwarder, I've noticed periods of non responsiveness occurring where I cant access pf from within the lan, but I also notice a large number of firewall log entries for port 53.

A typical entry would look like
Jan 1 22:48:56 Direction=OUT WAN my ip address:random port 78.151.235.3:53 UDP

but to various ip addresses, not just 78.151.235.3 in this example. When this happens I will typically see 75-100 entries per second which amounts to a DDOS of sorts on a slow ADSL home connection.

As resolver is running in default mode, is this normal or to be expected behaviour, and if so, could resolver become a cause for concern for those using pfsense on a variable ip adsl connection aka a typical home connection?

pfsense is running on a dual nic Intel NUC 847 http://www.intel.com/content/www/us/en/nuc/nuc-kit-dccp847dye.html with 8Gb of Ram and a 128Gb msata ssd, so performance shouldnt be too bad I would have thought.

So is there something I can do to avoid these periods of unresponsiveness, perhaps go back to the forwarder maybe, or change a setting or two?

TIA.

markuhde

@cmb:

@cmb:

@NobodyHere:

We're running the December 10th build. I can confirm issues with a new WAN address breaking unbound. When our PPPoE WAN link gets a new IP address, the resolver will reply with internal IPs set via DHCP clientIDs, but any external DNS lookup made via a system on the LAN fails.

DNS resolving on the firewall continues to work, so it's clearly an issue with unbound.

https://redmine.pfsense.org/issues/4095

The above referenced issue should be fixed. Those who were seeing that, please try on the 31st or newer snapshot.

I just discovered this issue, or one similar to it, today - the hard way. Unbound failing on a machine with a PPPoE link randomly, but DNS still working on the firewall - just not for any client. Build is 2.2-RC (i386)
built on Thu Jan 01 06:14:04 CST 2015
FreeBSD 10.1-RELEASE-p3

I went back to dnsmasq for now.

q54e3w

Im not sure if this is a real issue or if its particular to my setup but I was having trouble starting DNS Resolver. To maximise my 10be throughput I use a high kern.ipc.maxsockbuf

kern.ipc.maxsockbuf: 33554432

the so-rcvbuf is derived from this value so in my case, 'so-rcvbuf: 31m' which caused unbound to fail to launch with the following errors

Jan 4 08:47:06 php-fpm[6441]: /status_services.php: The command '/usr/local/sbin/unbound -c /var/unbound/unbound.conf' returned exit code '1', the output was '[1420361226] unbound[24922:0] debug: creating udp4 socket 192.168.50.1 53 [1420361226] unbound[24922:0] error: setsockopt(..., SO_RCVBUF, ...) failed: No buffer space available [1420361226] unbound[24922:0] fatal error: could not open ports'

adding an advanced option

so-rcvbuf: 8m

to reduce this 31m down to 8m allows unbound to start correctly.

phil.davis

@irj972:

Im not sure if this is a real issue or if its particular to my setup but I was having trouble starting DNS Resolver. To maximise my 10be throughput I use a high kern.ipc.maxsockbuf
kern.ipc.maxsockbuf: 33554432
the so-rcvbuf is derived from this value so in my case, 'so-rcvbuf: 31m' which caused unbound to fail to launch with the following errors
Jan 4 08:47:06 php-fpm[6441]: /status_services.php: The command '/usr/local/sbin/unbound -c /var/unbound/unbound.conf' returned exit code '1', the output was '[1420361226] unbound[24922:0] debug: creating udp4 socket 192.168.50.1 53 [1420361226] unbound[24922:0] error: setsockopt(..., SO_RCVBUF, ...) failed: No buffer space available [1420361226] unbound[24922:0] fatal error: could not open ports'
adding an advanced option
so-rcvbuf: 8m
to reduce this 31m down to 8m allows unbound to start correctly.

The unbound docs I have found all are giving 8m as the example for a busy system, so maybe there is something in the unbound compile or FreeBSD that is limiting that socket option to 8m anyway.
I made this pull request to limit the calculation to 8m : https://github.com/pfsense/pfsense/pull/1420
That might be a practical fix here to protect people like you who have set kern.ipc.maxsockbuf high for other reasons.

wagonza

Hrmm I have seen values as high as 32M. So further investigation as to why it failed will need to be done.
I will see what I can do to replicate.

raab

Not sure if it's been mentioned, on a dual wan setup when one WAN link fails over to the secondary WAN link, DNS lookups start to fail on client devices.

When I set outgoing to WAN1 and WAN2 it works fine, rather than the default ALL:

markuhde

THAT may have been the cause of the behaviour I saw that forced me to go back to dnsmasq.

markuhde

@markuhde:

THAT may have been the cause of the behaviour I saw that forced me to go back to dnsmasq.

UPDATE - no that wasn't it, as I already had it set to only allow out over the two interfaces that exist. One of the interfaces is a PPPoE.

wagonza

@irj972:

Im not sure if this is a real issue or if its particular to my setup but I was having trouble starting DNS Resolver. To maximise my 10be throughput I use a high kern.ipc.maxsockbuf
kern.ipc.maxsockbuf: 33554432

Setting kern.ipc.maxsockbuf = 37748736 (36MB) allows Unbound to start, so adding a 4MB buffer to the optimise code section caters for this. As kern.ipc.maxsockbuf increases this buffer grows. Needing more than 32m points towards moving the service off onto its own box.

wagonza

@markuhde:

@markuhde:

THAT may have been the cause of the behaviour I saw that forced me to go back to dnsmasq.

UPDATE - no that wasn't it, as I already had it set to only allow out over the two interfaces that exist. One of the interfaces is a PPPoE.

So what happened in your setup then?

cmb

@wagonza:

@markuhde:

@markuhde:

THAT may have been the cause of the behaviour I saw that forced me to go back to dnsmasq.

UPDATE - no that wasn't it, as I already had it set to only allow out over the two interfaces that exist. One of the interfaces is a PPPoE.

So what happened in your setup then?

I'm guessing what happens in that circumstance is he has it doing recursion, which leaves all DNS traffic following the default route, and when the default route is unreachable then nothing will resolve. In that case, enabling default gateway switching is probably the best bet. Alternatively, forwarder mode would be an option as well, specifying at least one DNS server under System>General Setup for each WAN.

raab

edit: nvm

markuhde

@cmb:

@wagonza:

@markuhde:

@markuhde:

THAT may have been the cause of the behaviour I saw that forced me to go back to dnsmasq.

UPDATE - no that wasn't it, as I already had it set to only allow out over the two interfaces that exist. One of the interfaces is a PPPoE.

So what happened in your setup then?

I'm guessing what happens in that circumstance is he has it doing recursion, which leaves all DNS traffic following the default route, and when the default route is unreachable then nothing will resolve. In that case, enabling default gateway switching is probably the best bet. Alternatively, forwarder mode would be an option as well, specifying at least one DNS server under System>General Setup for each WAN.

Correct, but as far as I know it was the second WAN (the PPPoE one) going down (or changing IPs), not the primary WAN, that killed resolution. Also, why would it still answer queries from localhost but not from machines on the network?