[Dnsmasq-discuss] dnsmasq to provide public DNS service

Albert ARIBAUD albert.aribaud at free.fr
Fri Jul 8 17:49:53 BST 2016


Hi Tong,

Le Thu, 7 Jul 2016 13:06:42 +0000 (UTC)
T o n g <mlist4suntong at yahoo.com> a écrit:

> On Thu, 07 Jul 2016 12:33:53 +0200, Albert ARIBAUD wrote:
> 
> > To determine which variant of netcat is present on these machines,
> > if any, could you run the following command, once on the dedicated
> > server, and once on the machine you are using to access the server:
> > 
> > 	netcat -h
> > 
> > ... and copy-paste both outputs in your reply?  
> 
> Both machines are running the latest Ubuntu. I.e., the output are the 
> same for both of them.
> 
> $ lsb_release -a
> No LSB modules are available.
> Distributor ID: Ubuntu
> Description:    Ubuntu 16.04 LTS
> Release:        16.04
> Codename:       xenial
> 
> $ apt-cache policy netcat-openbsd
> netcat-openbsd:
>   Installed: 1.105-7ubuntu1
>   Candidate: 1.105-7ubuntu1
>   Version table:
>  *** 1.105-7ubuntu1 500
>         500 http://archive.ubuntu.com/ubuntu xenial/main amd64
> Packages 100 /var/lib/dpkg/status
> 
> $ netcat -h
> OpenBSD netcat (Debian patchlevel 1.105-7ubuntu1)
> ...
> 
> > Once we have netcat available on both ends, we will be able to
> > mimic DNS exchanges between the machines but without dnsmasq being
> > involved;  
> 
> The connect is not the problem. I've stopped dnsmasq temporarily and 
> start SSH listening to port 53 and I was able to connect from home. 

The SSH test only proves you can access the box on TCP port 22
(assuming you're usign the defaults) from your home; this does not prove
anything regarding TCP port 53 or UDP port 53, which are what DNS uses.

So:

1. Open a terminal and start an SSH session to your box. In this
   session, disable dnsmasq then run

	netcat -u -l -p 53

3. On your home machine open one terminal and run

	netcat -u xyz 53

   where xyz should be replaced with the public IP of your box.

4. Type some text then hit the Enter key on your home machine.
   Does your box display the text?

5. Type some other text then hit the Enter key in the shell to your box.
   Does the netcat running locally  display the text?

Amicalement,
-- 
Albert.



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