Re: [Dnsmasq-discuss] Finding actual DNS server used

[Albert ARIBAUD]

Hi Weedy,

Le Sun, 15 Jan 2017 17:23:18 -0500
Weedy  a écrit:

> >> http://www.thekelleys.org.uk/dnsmasq/docs/dnsmasq-man.html#lbAG
> >>
> >> An API of sorts was added some time last year  
> >
> > I've gone through the NOTES section you are referring to, but I
> > don't see exactly which API you are referring to. Could you provide
> > more precise indications?  
> 
> I was talking about "statistics are also available in the DNS as
> answers to queries of class CHAOS and type TXT in domain bind". Which
> is why I said API of sorts.

Hey, it does indeed work!

$ dig +short chaos txt servers.bind
"fe80:::::%enp4s0#53 144 0" "192.168.x.x#53 126 0"

> You already went into detail on DBus control, that would be considered
> a more legit API

I would not say one is 'more legit' than the other, as both are
legitimate uses of valid protocol features; and yours has the advantage
that it's easier to parse.

Thanks!

Amicalement,
-- 
Albert.

___
Dnsmasq-discuss mailing list
Dnsmasq-discuss@lists.thekelleys.org.uk
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

Re: [Dnsmasq-discuss] Finding actual DNS server used

[Weedy]

On 15 January 2017 at 17:15, Albert ARIBAUD  wrote:
> Hi Weedy,
>
> Le Sun, 15 Jan 2017 17:04:37 -0500
> Weedy  a écrit:
>
>> On 15 January 2017 at 03:21, Albert ARIBAUD 
>> wrote:
>> > Hi Chris,
>> >
>> > Le Sat, 14 Jan 2017 19:27:28 +
>> > Chris Green  a écrit:
>> >
>> > (re getting dnsmasq to say which upstream servers it uses)
>> >
>> >> Why is is so difficult to provide this information?  At the very
>> >> least it would provide a confidence check that all is working as
>> >> intended. It might very well help if something isn't working too.
>> >
>> > It is not difficult at all to get this information. It's just that
>> > dnsmasq does not provide any "API" to get it, because it's easy to
>> > get it  otherwise for diagnosis purposes.
>>
>> http://www.thekelleys.org.uk/dnsmasq/docs/dnsmasq-man.html#lbAG
>>
>> An API of sorts was added some time last year
>
> I've gone through the NOTES section you are referring to, but I don't
> see exactly which API you are referring to. Could you provide more
> precise indications?

I was talking about "statistics are also available in the DNS as
answers to queries of class CHAOS and type TXT in domain bind". Which
is why I said API of sorts.

You already went into detail on DBus control, that would be considered
a more legit API

___
Dnsmasq-discuss mailing list
Dnsmasq-discuss@lists.thekelleys.org.uk
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

Re: [Dnsmasq-discuss] Finding actual DNS server used

[Weedy]

On 14 January 2017 at 07:40, Lars Noodén  wrote:
> How can I get an already running instance of Dnsmasq to tell which DNS
> servers it is using to resolve new queries upstream?

It's in the man page. Also I think we added special TXT or something
queries last year.

Sun Jan 15 15:01:00 2017 cron.info crond[976]: USER root pid 9833 cmd
killall -USR1 dnsmasq
Sun Jan 15 15:01:00 2017 daemon.info dnsmasq[2350]: time 1484510460
Sun Jan 15 15:01:00 2017 daemon.info dnsmasq[2350]: cache size 4096,
0/3244 cache insertions re-used unexpired cache entries.
Sun Jan 15 15:01:00 2017 daemon.info dnsmasq[2350]: queries forwarded
1565, queries answered locally 16006
Sun Jan 15 15:01:00 2017 daemon.info dnsmasq[2350]: server
66.163.0.161#53: queries sent 882, retried or failed 9
Sun Jan 15 15:01:00 2017 daemon.info dnsmasq[2350]: server
208.72.120.204#53: queries sent 903, retried or failed 8
Sun Jan 15 15:01:00 2017 daemon.info dnsmasq[2350]: server
205.151.222.251#53: queries sent 316, retried or failed 0
Sun Jan 15 15:01:00 2017 daemon.info dnsmasq[2350]: server
216.254.141.2#53: queries sent 325, retried or failed 4
Sun Jan 15 15:01:00 2017 daemon.info dnsmasq[2350]: server 8.8.4.4#53:
queries sent 328, retried or failed 2
Sun Jan 15 15:01:00 2017 daemon.info dnsmasq[2350]: server
206.248.154.170#53: queries sent 330, retried or failed 0
Sun Jan 15 15:01:00 2017 daemon.info dnsmasq[2350]: server
206.248.154.22#53: queries sent 365, retried or failed 6

Why is the thread 20 replies long without answering the original question

___
Dnsmasq-discuss mailing list
Dnsmasq-discuss@lists.thekelleys.org.uk
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

Re: [Dnsmasq-discuss] Finding actual DNS server used

[Weedy]

On 15 January 2017 at 03:21, Albert ARIBAUD  wrote:
> Hi Chris,
>
> Le Sat, 14 Jan 2017 19:27:28 +
> Chris Green  a écrit:
>
> (re getting dnsmasq to say which upstream servers it uses)
>
>> Why is is so difficult to provide this information?  At the very least
>> it would provide a confidence check that all is working as intended.
>> It might very well help if something isn't working too.
>
> It is not difficult at all to get this information. It's just that
> dnsmasq does not provide any "API" to get it, because it's easy to get
> it  otherwise for diagnosis purposes.

http://www.thekelleys.org.uk/dnsmasq/docs/dnsmasq-man.html#lbAG

An API of sorts was added some time last year

___
Dnsmasq-discuss mailing list
Dnsmasq-discuss@lists.thekelleys.org.uk
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

Re: [Dnsmasq-discuss] Finding actual DNS server used

[Albert ARIBAUD]

Hi Chris,

Le Sun, 15 Jan 2017 20:31:28 +
Chris Green  a écrit:

> On Sun, Jan 15, 2017 at 04:54:11PM +0100, Albert ARIBAUD wrote:
> > Bonjour,
> > 
> > Le Sun, 15 Jan 2017 12:36:47 +
> > Chris Green  a écrit:
> >   
> > > On Sun, Jan 15, 2017 at 12:14:42PM +0100, Albert ARIBAUD wrote:  
> > > > > > - read the configuration file(s) dnsmasq uses and find
> > > > > > "server=" lines in it, and read the /etc/resolv* tree, if
> > > > > > dnsmasq uses them, and that will give the list of servers
> > > > > > dnmasq uses at any point in time.
> > > > > >   
> > > > > There aren't any! These are systems where dnsmasq is run by
> > > > > Network Manager rather than directly, thus there is no spcific
> > > > > dnsmasq configuration file.
> > > > 
> > > > ... and then the configuration is known from the dnsmasq process
> > > > command line. So let me amend my statement above: "... read the
> > > > configuration options, from the dnsmasq process command line if
> > > > it contains any, and from the configuration file or files if
> > > > applicable".   
> > > chris@t430$ ps -ef | grep dnsmasq
> > > nobody1579  1031  0 Jan14 ?
> > > 00:00:01 /usr/sbin/dnsmasq --no-resolv --keep-in-foreground
> > > --no-hosts --bind-interfaces
> > > --pid-file=/var/run/NetworkManager/dnsmasq.pid
> > > --listen-address=127.0.1.1 --cache-size=0 --conf-file=/dev/null
> > > --proxy-dnssec
> > > --enable-dbus=org.freedesktop.NetworkManager.dnsmasq
> > > --conf-dir=/etc/NetworkManager/dnsmasq.d chris@t430$ 
> > > 
> > > 
> > > ... and there's nothing in /etc/NetworkManager/dnsmasq.d  
> > 
> > Then Network Manager sets the DNS via DBus, as the configuration
> > (on command line) allows it. You can most probably find which DNS
> > servers are set by spying on DBus, using dbus-monitor. You can even
> > set up a bash script which shows a list of them in real time.
> >   
> Is there any description anywhere of how to do this?

A ready-made solution with zero effort? Non, there is none.

A solution with some effort? In my case, 10 minutes of searching how to
filter dbus-monitor by interface, starting with near-zero knowledge of
DBus, and strictly zero knowledge of dbus-monitor, and ending up with
the following proof-of-concept running on my machine:

1. Run this command in a shell:

sudo dbus-monitor --system \
"interface=org.freedesktop.NetworkManager.dnsmasq"

(your interface may not be the same. Run

dbus-send --system --dest=org.freedesktop.DBus
--type=method_call --print-reply /org/freedesktop/DBus
org.freedesktop.DBus.ListNames | grep dnsmasq

and you'll know the interface to use.

2. Force a connection renewal through Network Manager (or by unplugging
   and replugging the client's RJ45 if that's how it gets network
   access).

3. See the dbus-monitor running in the shell display dumps of the
   SetServersEx method calls, complete with server IPs as arguments.

If you want to automate that, you'll need to do some parsing. Or maybe
use Python, which provides a dbus module; this should make extracting
the method arguments easier.

Amicalement,
-- 
Albert.

___
Dnsmasq-discuss mailing list
Dnsmasq-discuss@lists.thekelleys.org.uk
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

Re: [Dnsmasq-discuss] Finding actual DNS server used

[Chris Green]

On Sun, Jan 15, 2017 at 04:54:11PM +0100, Albert ARIBAUD wrote:
> Bonjour,
> 
> Le Sun, 15 Jan 2017 12:36:47 +
> Chris Green  a écrit:
> 
> > On Sun, Jan 15, 2017 at 12:14:42PM +0100, Albert ARIBAUD wrote:
> > > > > - read the configuration file(s) dnsmasq uses and find "server="
> > > > >   lines in it, and read the /etc/resolv* tree, if dnsmasq uses
> > > > > them, and that will give the list of servers dnmasq uses at any
> > > > > point in time.
> > > > > 
> > > > There aren't any! These are systems where dnsmasq is run by
> > > > Network Manager rather than directly, thus there is no spcific
> > > > dnsmasq configuration file.  
> > > 
> > > ... and then the configuration is known from the dnsmasq process
> > > command line. So let me amend my statement above: "... read the
> > > configuration options, from the dnsmasq process command line if it
> > > contains any, and from the configuration file or files if
> > > applicable". 
> > chris@t430$ ps -ef | grep dnsmasq
> > nobody1579  1031  0 Jan14 ?00:00:01 /usr/sbin/dnsmasq
> > --no-resolv --keep-in-foreground --no-hosts --bind-interfaces
> > --pid-file=/var/run/NetworkManager/dnsmasq.pid
> > --listen-address=127.0.1.1 --cache-size=0 --conf-file=/dev/null
> > --proxy-dnssec
> > --enable-dbus=org.freedesktop.NetworkManager.dnsmasq
> > --conf-dir=/etc/NetworkManager/dnsmasq.d chris@t430$ 
> > 
> > 
> > ... and there's nothing in /etc/NetworkManager/dnsmasq.d
> 
> Then Network Manager sets the DNS via DBus, as the configuration
> (on command line) allows it. You can most probably find which DNS
> servers are set by spying on DBus, using dbus-monitor. You can even set
> up a bash script which shows a list of them in real time.
> 
Is there any description anywhere of how to do this?

-- 
Chris Green

___
Dnsmasq-discuss mailing list
Dnsmasq-discuss@lists.thekelleys.org.uk
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

Re: [Dnsmasq-discuss] Finding actual DNS server used

[Albert ARIBAUD]

Bonjour,

Le Sun, 15 Jan 2017 12:36:47 +
Chris Green  a écrit:

> On Sun, Jan 15, 2017 at 12:14:42PM +0100, Albert ARIBAUD wrote:
> > > > - read the configuration file(s) dnsmasq uses and find "server="
> > > >   lines in it, and read the /etc/resolv* tree, if dnsmasq uses
> > > > them, and that will give the list of servers dnmasq uses at any
> > > > point in time.
> > > > 
> > > There aren't any! These are systems where dnsmasq is run by
> > > Network Manager rather than directly, thus there is no spcific
> > > dnsmasq configuration file.  
> > 
> > ... and then the configuration is known from the dnsmasq process
> > command line. So let me amend my statement above: "... read the
> > configuration options, from the dnsmasq process command line if it
> > contains any, and from the configuration file or files if
> > applicable". 
> chris@t430$ ps -ef | grep dnsmasq
> nobody1579  1031  0 Jan14 ?00:00:01 /usr/sbin/dnsmasq
> --no-resolv --keep-in-foreground --no-hosts --bind-interfaces
> --pid-file=/var/run/NetworkManager/dnsmasq.pid
> --listen-address=127.0.1.1 --cache-size=0 --conf-file=/dev/null
> --proxy-dnssec
> --enable-dbus=org.freedesktop.NetworkManager.dnsmasq
> --conf-dir=/etc/NetworkManager/dnsmasq.d chris@t430$ 
> 
> 
> ... and there's nothing in /etc/NetworkManager/dnsmasq.d

Then Network Manager sets the DNS via DBus, as the configuration
(on command line) allows it. You can most probably find which DNS
servers are set by spying on DBus, using dbus-monitor. You can even set
up a bash script which shows a list of them in real time.

Amicalement,
-- 
Albert.

___
Dnsmasq-discuss mailing list
Dnsmasq-discuss@lists.thekelleys.org.uk
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

Re: [Dnsmasq-discuss] Finding actual DNS server used

[Chris Green]

On Sun, Jan 15, 2017 at 12:14:42PM +0100, Albert ARIBAUD wrote:
> > > - read the configuration file(s) dnsmasq uses and find "server="
> > >   lines in it, and read the /etc/resolv* tree, if dnsmasq uses them,
> > >   and that will give the list of servers dnmasq uses at any point in
> > >   time.
> > >   
> > There aren't any! These are systems where dnsmasq is run by Network
> > Manager rather than directly, thus there is no spcific dnsmasq
> > configuration file.
> 
> ... and then the configuration is known from the dnsmasq process command
> line. So let me amend my statement above: "... read the configuration
> options, from the dnsmasq process command line if it contains any, and
> from the configuration file or files if applicable".
> 
chris@t430$ ps -ef | grep dnsmasq
nobody1579  1031  0 Jan14 ?00:00:01 /usr/sbin/dnsmasq
--no-resolv --keep-in-foreground --no-hosts --bind-interfaces
--pid-file=/var/run/NetworkManager/dnsmasq.pid
--listen-address=127.0.1.1 --cache-size=0 --conf-file=/dev/null
--proxy-dnssec --enable-dbus=org.freedesktop.NetworkManager.dnsmasq
--conf-dir=/etc/NetworkManager/dnsmasq.d
chris@t430$ 


... and there's nothing in /etc/NetworkManager/dnsmasq.d

-- 
Chris Green

___
Dnsmasq-discuss mailing list
Dnsmasq-discuss@lists.thekelleys.org.uk
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

Re: [Dnsmasq-discuss] Finding actual DNS server used

[Chris Green]

On Sat, Jan 14, 2017 at 05:43:38PM -0500, Jim Alles wrote:
>As far as the desktop OS, a user can override the DNS entries that DHCP
>provides.

Not easily on most modern systems.  This is really where we came in!

All my xubuntu Linux boxes have the following in /etc/resolv.conf :-

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by 
resolvconf(8)
# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 127.0.1.1
search zbmc.eu

I.e. the nameserver is 'me' and somewhere in the guts of the Network
Manager and dnsmasq configuration is something that specifies the
upstream server.

It's definitely *not* trivial to change the DNS being used.

-- 
Chris Green

___
Dnsmasq-discuss mailing list
Dnsmasq-discuss@lists.thekelleys.org.uk
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

Re: [Dnsmasq-discuss] Finding actual DNS server used

[Albert ARIBAUD]

Le Sun, 15 Jan 2017 09:58:38 +0100
Albert ARIBAUD  a écrit:

> Speaking of which, my first hunch re your problem is that it's not a
> dnsmasq problem, but a problem with the client's networking
> configuration. I suspect it connects through some VPN and gets an
> additional (or replacement) DNS, and that at some point the VPN
> connection goes bad and the client reverts (in part or in full) to its
> original DNS.

... or it could be that the VPN connection still runs OK but your
client screwed up its DNS setup upon renewal of its local DHCP lease.

Amicalement,
-- 
Albert.

___
Dnsmasq-discuss mailing list
Dnsmasq-discuss@lists.thekelleys.org.uk
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

Re: [Dnsmasq-discuss] Finding actual DNS server used

[Albert ARIBAUD]

Hi Lars,

Le Sun, 15 Jan 2017 10:21:01 +0200
Lars Noodén  a écrit:

> On 01/15/2017 09:55 AM, Albert ARIBAUD wrote:
> > Hi Lars,
> > 
> > Le Sat, 14 Jan 2017 20:18:13 +0200
> > Lars Noodén  a écrit:
> >...  
> >>  Because it's not my system and it is remote, I
> >> have to go step by step, slowly.  
> > 
> > ... Do you mean that you have good control of the remote system but
> > have to go there physically to run tests, or that you do not have
> > control of the system and must ask someone else to perform tests
> > there? This makes a difference in the way you can run your tests  
> 
> I have to describe the steps in e-mail and they are then carried out
> on site by a non-technical person.

Argh.

> >> Since everything on that system, in
> >> regards to DNS, is going via Dnsmasq, I'd like to see what it has
> >> loaded and is using.  
> > 
> > This bring me back to your description of the bug above: "somewhere
> > early on the DNS fails". What do you mean with that? Did you check
> > that the client keeps sinding DNS requests to your dnsmasq?  
> 
> The client application (Blink) will apparently default to Google's DNS
> if it cannot connect to the server right away.  What's happening is
> that half the time DNS replies, half the time it times out.  Thus the
> client can start to register with the SIP server, but then fails to
> publish its presence or be able to initiate a call.
> 
> > ... Or is
> > it that they come back from your dnsmasq with an error code for
> > domains which you know your dns should resolve properly?  
> 
> It seems to be this -- sometimes.
> 
> So is the short answer that there's no direct or easy way to poll a
> running Dnsmasq instance and see what it's pointing to?  If so, then
> I'll not bother the list more with this issue.  However, may I put in
> a feature request if there is a wish list?

See my other replies, but I'll make the main suggestion: the way to get
the info you want (and more, which might be useful for your diagnostics)
is to run tcpdump on the dnsmasq host on the "any' interface (or run
two tcpdumps, one on the interface used to talk to the client, one on
the interface used to talk to the Internet) with a capture filter set
for DHCP and DNS protocols, and write the capture into a file (or two,
if running two tcpdump instances). Then if you have two captures you
can use Wireshark's mergecap tool to merge them into a single one. Last,
you open the single capture file in Wireshark and see:

- whether your client was sent out a DHCP reply configuring DNS servers

- which DNS requests your client sent to dnsmasq

- which DNS requests your dnsmasq sent to which upstream server

- which DNS replies your dnsmasq received from which upstream server

- which DNS replies your client received from dnsmasq

That's the info you're asking for (of course, I assume you have control
of the host running dnsmasq) and much more. The method can be useful
for diagnosing other network or protocol issues as well.

Speaking of which, my first hunch re your problem is that it's not a
dnsmasq problem, but a problem with the client's networking
configuration. I suspect it connects through some VPN and gets an
additional (or replacement) DNS, and that at some point the VPN
connection goes bad and the client reverts (in part or in full) to its
original DNS.

In any case, the test above will give you a hint about that too: if you
see that the client stops sending requests at some point, you can
pretty much conclude it stopped using your dnsmasq as its DNS (you can
even know when it last did, and compare that with logs from the client
if you can get the non-tech person to do it.

BTW: I suspect there is no way to get the non-tech person to install a
remote access client (even ssh would be enough) and also no way for
you to get root privileges on it?

> Regards,
> /Lars

Amicalement,
-- 
Albert.

___
Dnsmasq-discuss mailing list
Dnsmasq-discuss@lists.thekelleys.org.uk
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

Re: [Dnsmasq-discuss] Finding actual DNS server used

[Lars Noodén]

On 01/15/2017 09:55 AM, Albert ARIBAUD wrote:
> Hi Lars,
> 
> Le Sat, 14 Jan 2017 20:18:13 +0200
> Lars Noodén  a écrit:
>...
>>  Because it's not my system and it is remote, I
>> have to go step by step, slowly.
> 
> ... Do you mean that you have good control of the remote system but
> have to go there physically to run tests, or that you do not have
> control of the system and must ask someone else to perform tests there?
> This makes a difference in the way you can run your tests

I have to describe the steps in e-mail and they are then carried out on
site by a non-technical person.

>> Since everything on that system, in
>> regards to DNS, is going via Dnsmasq, I'd like to see what it has
>> loaded and is using.
> 
> This bring me back to your description of the bug above: "somewhere
> early on the DNS fails". What do you mean with that? Did you check
> that the client keeps sinding DNS requests to your dnsmasq?

The client application (Blink) will apparently default to Google's DNS
if it cannot connect to the server right away.  What's happening is that
half the time DNS replies, half the time it times out.  Thus the client
can start to register with the SIP server, but then fails to publish its
presence or be able to initiate a call.

> ... Or is
> it that they come back from your dnsmasq with an error code for domains
> which you know your dns should resolve properly?

It seems to be this -- sometimes.

So is the short answer that there's no direct or easy way to poll a
running Dnsmasq instance and see what it's pointing to?  If so, then
I'll not bother the list more with this issue.  However, may I put in a
feature request if there is a wish list?

Regards,
/Lars

___
Dnsmasq-discuss mailing list
Dnsmasq-discuss@lists.thekelleys.org.uk
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

Re: [Dnsmasq-discuss] Finding actual DNS server used

[Albert ARIBAUD]

Hi Chris,

Le Sat, 14 Jan 2017 19:27:28 +
Chris Green  a écrit:

(re getting dnsmasq to say which upstream servers it uses)

> Why is is so difficult to provide this information?  At the very least
> it would provide a confidence check that all is working as intended.
> It might very well help if something isn't working too.

It is not difficult at all to get this information. It's just that
dnsmasq does not provide any "API" to get it, because it's easy to get
it  otherwise for diagnosis purposes.

For diagnosis, the operator can:

- read the configuration file(s) dnsmasq uses and find "server="
  lines in it, and read the /etc/resolv* tree, if dnsmasq uses them,
  and that will give the list of servers dnmasq uses at any point in
  time.

- log DNS queries, which will give the additional info about
  which client actually queried dnsmasq, which queries were cached vs
  sent upstream (to which server), and what the answer was.

- run tcpdump or wireshark on the dnsmasq host or on the DNS client (or
  both for troubleshooting e.g. timing-related issues). This will give
  a full view of DNS exchanges on the considerd machine, to the last
  bit, litterally.

So, from a diagnosis point of view, pulling the actual list of servers
from a running dnsmasq is not that much of a need.

I don't mean to say that such an "API" would be unneeded for other
requirements than network troubleshooting, and if it existed, I would
use and suggest it for troubleshooting too; but here, I mean to say
that helping solving Lars' problem does not require such an "API".

I feel that Lars' question was more "How can I troubleshoot my possibly
dnsmasq-related issue?" rather than "How can I find which servers my
dnsmasq uses?", and for this, we have the means above, which emcompass
the one Lars asks for and go well beyond -- plus, the first step to
troubleshooting an issue is to get the situation as precise as
possible, possibly ignoring the initially assumed cause (here the list
of upstream servers may be actually correct and the issue may be on the
client side, so the "API" question should be set aside, and getting a
more precise view of the issue should come first).

> For example if my machine can't connect to another machine on the LAN
> but can see the outside world it suggests it's getting DNS from
> something other than my Pi DNS server.  If I could check what DNS it
> is using then it would confirm that either it has got it's DNS set up
> from somewhere else or that it has got the right DNS (the Pi) but that
> the Pi is set up wrong somehow.

This case can be tested (and boy do I know it) with the host command on
the client as Jim suggested (although I personally use dig).

Amicalement,
-- 
Albert.

___
Dnsmasq-discuss mailing list
Dnsmasq-discuss@lists.thekelleys.org.uk
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

Re: [Dnsmasq-discuss] Finding actual DNS server used

[Jim Alles]

Lars,

On Sat, Jan 14, 2017 at 7:40 AM, Lars Noodén  wrote:

> How can I get an already running instance of Dnsmasq to tell which DNS
> servers it is using to resolve new queries upstream?
>
> ​I am not sure that is the most reliable way to get the information you
are looking for.​ Any client App can try to use whatever DNS server it
wants to resolve names. That isn't polite, but it happens a lot with
smartphones, and IoT in general.

As far as the desktop OS, a user can override the DNS entries that DHCP
provides.

I lock my network clients into OpenDNS by using dnsmasq on my router
(Untangle's NGFW) pointed to their servers, and the firewall to block any
other attempts besides dnsmasq. The firewall then provides a handy log of
attempts to bypass my wishes.

Another way to see what is going on, is to run wireshark and filter for UDP
port 53.

dnsmasq can't know about things going around it.

Peace,

Jim A.
___
Dnsmasq-discuss mailing list
Dnsmasq-discuss@lists.thekelleys.org.uk
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

Re: [Dnsmasq-discuss] Finding actual DNS server used

[Chris Green]

On Sat, Jan 14, 2017 at 07:29:47PM +0100, Albert ARIBAUD wrote:
> Hi again Chris,
> 
> Le Sat, 14 Jan 2017 16:06:39 +
> Chris Green  a écrit:
> 
> > On Sat, Jan 14, 2017 at 03:40:52PM +0100, Albert ARIBAUD wrote:
> > > > I've not spotted anything in the manual page that stands out for
> > > > that purpose.  
> > > 
> > > There is not much point for it, is there? I mean, if dnsmasq has
> > > upstream servers (possibly per request domain) and acts as a local
> > > server, it is so that DNS clients on the LAN do *not* have to know
> > > these upstream servers.
> > > 
> > > Or maybe I am missing something. What is your use case?
> > >   
> > Well for one it's useful to be able to check whether dnsmasq is using
> > a sensible DNS server.  
> 
> Whatever server dnsmasq uses, it does so because its configuration
> tells it to. The servers in this configuration are there either
> because they were put in there by the dnamasq host admin (e.g., for
> handling unqualified names as LAN names), or because the host has one
> or more interfaces on which it is a DHCP client, not server, and the
> actual DHCP server announces a DNS server which e.g. the Network
> Manager added to the dnsmasq config. Do you see another case?
> 
Yes, so I want to check that the DNS server I *think* it should be
using from the configuration or DHCP is *actually* what it's using.


> > On my home LAN I have a full dnsmasq running on a Raspberry Pi and
> > point all the other systems at that for DNS.  The other systems
> > include a number of xubuntu Linux systems which run the 'local only'
> > dnsmasq which is run automatically by Network Manager.
> 
> Pretty much the same here on the very machine I am typing on right
> now except my LAN's dnsmasq does not run on a RPi. :)
> 
> > Thus in my case, to prove that everything is working as intended, I'd
> > like to be able to see that all systems (except the Raspberry Pi) are
> > using the Raspberry Pi as their DNS server.  In addition I might also
> > want to check what upstream servers the Pi is using.
> 
> I don't understand your problem... The local dnsmasq on my Xubuntu
> machine takes its servers from its only source of DNS server IPs: the
> DHCP (and RA) info it receives from my LAN's dnsmasq, and I control that
> (as you control that on your RPi's dnsmasq), therefore I *know* which
> DNS servers my Xubuntu machine can use.
> 
If it's working right and as you expected, yes.  However it could be,
for example, that your desktop machine is getting the wrong DHCP
server (I have routers that might, if misconfigured, provide DHCP).


> Why do you think any of your Xubuntu machine would use a DNS server it
> was not provided through DHCP or RA ?
> 
I don't, but it *might* not have used the DHCP server I thought it did.


Why is is so difficult to provide this information?  At the very least
it would provide a confidence check that all is working as intended.
It might very well help if something isn't working too.

For example if my machine can't connect to another machine on the LAN
but can see the outside world it suggests it's getting DNS from
something other than my Pi DNS server.  If I could check what DNS it
is using then it would confirm that either it has got it's DNS set up
from somewhere else or that it has got the right DNS (the Pi) but that
the Pi is set up wrong somehow.

-- 
Chris Green

___
Dnsmasq-discuss mailing list
Dnsmasq-discuss@lists.thekelleys.org.uk
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

Re: [Dnsmasq-discuss] Finding actual DNS server used

[Albert ARIBAUD]

Hi again Chris,

Le Sat, 14 Jan 2017 16:06:39 +
Chris Green  a écrit:

> On Sat, Jan 14, 2017 at 03:40:52PM +0100, Albert ARIBAUD wrote:
> > > I've not spotted anything in the manual page that stands out for
> > > that purpose.  
> > 
> > There is not much point for it, is there? I mean, if dnsmasq has
> > upstream servers (possibly per request domain) and acts as a local
> > server, it is so that DNS clients on the LAN do *not* have to know
> > these upstream servers.
> > 
> > Or maybe I am missing something. What is your use case?
> >   
> Well for one it's useful to be able to check whether dnsmasq is using
> a sensible DNS server.  

Whatever server dnsmasq uses, it does so because its configuration
tells it to. The servers in this configuration are there either
because they were put in there by the dnamasq host admin (e.g., for
handling unqualified names as LAN names), or because the host has one
or more interfaces on which it is a DHCP client, not server, and the
actual DHCP server announces a DNS server which e.g. the Network
Manager added to the dnsmasq config. Do you see another case?

> On my home LAN I have a full dnsmasq running on a Raspberry Pi and
> point all the other systems at that for DNS.  The other systems
> include a number of xubuntu Linux systems which run the 'local only'
> dnsmasq which is run automatically by Network Manager.

Pretty much the same here on the very machine I am typing on right
now except my LAN's dnsmasq does not run on a RPi. :)

> Thus in my case, to prove that everything is working as intended, I'd
> like to be able to see that all systems (except the Raspberry Pi) are
> using the Raspberry Pi as their DNS server.  In addition I might also
> want to check what upstream servers the Pi is using.

I don't understand your problem... The local dnsmasq on my Xubuntu
machine takes its servers from its only source of DNS server IPs: the
DHCP (and RA) info it receives from my LAN's dnsmasq, and I control that
(as you control that on your RPi's dnsmasq), therefore I *know* which
DNS servers my Xubuntu machine can use.

Why do you think any of your Xubuntu machine would use a DNS server it
was not provided through DHCP or RA ?

Amicalement,
-- 
Albert.

___
Dnsmasq-discuss mailing list
Dnsmasq-discuss@lists.thekelleys.org.uk
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

Re: [Dnsmasq-discuss] Finding actual DNS server used

[Lars Noodén]

On 01/14/2017 06:06 PM, Chris Green wrote:
> On Sat, Jan 14, 2017 at 03:40:52PM +0100, Albert ARIBAUD wrote:
[snip]
>> Or maybe I am missing something. What is your use case?
>>
> Well for one it's useful to be able to check whether dnsmasq is using
> a sensible DNS server.  
[snip]

That's what I'm aiming for.  There is an application on a remote
computer that is failing because it appears to initially get a working
nameserver but then somewhere early on the DNS fails.  I think it would
help the diagnosis to see which nameservers dnsmasq is actually calling
or caching.  Because it's not my system and it is remote, I have to go
step by step, slowly.  Since everything on that system, in regards to
DNS, is going via Dnsmasq, I'd like to see what it has loaded and is using.

Regards,
Lars


___
Dnsmasq-discuss mailing list
Dnsmasq-discuss@lists.thekelleys.org.uk
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

Re: [Dnsmasq-discuss] Finding actual DNS server used

[Chris Green]

On Sat, Jan 14, 2017 at 03:40:52PM +0100, Albert ARIBAUD wrote:
> > I've not spotted anything in the manual page that stands out for that
> > purpose.
> 
> There is not much point for it, is there? I mean, if dnsmasq has
> upstream servers (possibly per request domain) and acts as a local
> server, it is so that DNS clients on the LAN do *not* have to know
> these upstream servers.
> 
> Or maybe I am missing something. What is your use case?
> 
Well for one it's useful to be able to check whether dnsmasq is using
a sensible DNS server.  

On my home LAN I have a full dnsmasq running on a Raspberry Pi and
point all the other systems at that for DNS.  The other systems
include a number of xubuntu Linux systems which run the 'local only'
dnsmasq which is run automatically by Network Manager.

Thus in my case, to prove that everything is working as intended, I'd
like to be able to see that all systems (except the Raspberry Pi) are
using the Raspberry Pi as their DNS server.  In addition I might also
want to check what upstream servers the Pi is using.

-- 
Chris Green

___
Dnsmasq-discuss mailing list
Dnsmasq-discuss@lists.thekelleys.org.uk
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

Re: [Dnsmasq-discuss] Finding actual DNS server used

[Albert ARIBAUD]

Hi Lars,

Le Sat, 14 Jan 2017 14:40:14 +0200
Lars Noodén  a écrit:

> How can I get an already running instance of Dnsmasq to tell which DNS
> servers it is using to resolve new queries upstream?
> 
> Specifically how can this be done in distros like Ubuntu and Linux
> Mint, which have setups like this::
> 
> # cat /etc/resolv.conf
> # Dynamic resolv.conf(5) file for glibc resolver(3) generated by
> resolvconf(8)
> # DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE
> OVERWRITTEN nameserver 127.0.1.1
> 
> 
> # ps auxw |grep dnsmasq
> nobody2711  0.0  0.0  31028  3276 ?S13:27   0:00
> /usr/sbin/dnsmasq --no-resolv --keep-in-foreground --no-hosts
> --bind-interfaces
> --pid-file=/run/sendsigs.omit.d/network-manager.dnsmasq.pid
> --listen-address=127.0.1.1
> --conf-file=/var/run/NetworkManager/dnsmasq.conf --cache-size=0
> --proxy-dnssec --enable-dbus=org.freedesktop.NetworkManager.dnsmasq
> --conf-dir=/etc/NetworkManager/dnsmasq.d
> 
> I've not spotted anything in the manual page that stands out for that
> purpose.

There is not much point for it, is there? I mean, if dnsmasq has
upstream servers (possibly per request domain) and acts as a local
server, it is so that DNS clients on the LAN do *not* have to know
these upstream servers.

Or maybe I am missing something. What is your use case?

> Regards,
> Lars

Amicalement,
-- 
Albert.

___
Dnsmasq-discuss mailing list
Dnsmasq-discuss@lists.thekelleys.org.uk
http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss