Bug or feature? \00 in hostnames?

RouterOS General
1

I am currently observing strange behaviour on RouterOS (v.6.20).

Every linux based host has \00 in their hostname.
Windows Machines doesnt have it.
[admin@kari-crs] > /ip dhcp-server lease print
Flags: X - disabled, R - radius, D - dynamic, B - blocked

ADDRESS MAC-ADDRESS HOST-NAME SERVER RATE-LIMIT STATUS

0 192.168.1.2 60:A4:4C:8E:9C:90 dhcp-server1 bound
1 192.168.1.10 00:11:32:28:9D:E7 Syno\00 dhcp-server1 bound
2 192.168.1.16 00:90:A9:69:B3:40 WDTVLive\00 dhcp-server1 bound
3 192.168.1.17 00:E0:36:EF:EE:D6 dhcp-server1
4 D 192.168.1.251 60:45:BD:EC:54:98 Surface-RT dhcp-server1 bound
5 D 192.168.1.250 EC:F3:5B:50:EA:C4 Etzi-Lumia dhcp-server1 bound
6 D 192.168.1.248 84:3A:4B:47:BD:68 MSA-4000237 dhcp-server1 bound
7 192.168.1.15 00:02:9B:CA:88:93 dhcp-server1 boundIn a result, every Static DNS (for any Linux/BSD host), generated by the script has an whitespace between Hostname and domain, so they wont resolve. :frowning:
Of course I could trim that "\00" in the script, but I would like to understand why it does that in a first place. :wink:

2

I see it with a Synology NAS as well. Don’t recall if I saw it with Ubuntu Linux clients. I suspect that the host-name is the client identifier (option) which I don’t think is a NULL terminated string. Chances are that the DHCP client is broken on embedded Linux devices.

3

check settings on these devices, i have linux boxes running and have never seen trailing \00 for hostnames.

Check if /etc/hostname and /etc/hosts have newline at the end of the configuration file.

4

On mine the hostname file looks okay:

[duck] Matt>od -c hostname
0000000   d   s   1   1   0   j  \n
0000007




[duck] Matt>od -c hosts
0000000   1   2   7   .   0   .   0   .   1  \t   l   o   c   a   l   h
0000020   o   s   t  \n   1   9   2   .   1   6   8   .   1   4   4   .
0000040   8  \t   d   s   1   1   0   j  \n  \n  \n  \n  \n  \n  \n  \n
0000060  \n  \n  \n  \n  \n  \n  \n  \n  \n  \n  \n  \n  \n  \n  \n  \n
*
0000260  \n  \n  \n  \n  \n  \n  \n  \n
0000270
5

On WD TV you cannot check anything as you dont have SSH access at all or any other way to access config files.
On Synology, I will check later…but I really doubt that I find anything abnormal.

Anyway, it doesnt occure on any other router, verified with couple ones.
DD-WRT and OpenWRT, both show hostnames as they should be… :wink:

Same here… :unamused:

6

I had a Qnap NAS (with original firmware) which gave the same result. I can’t recall the hostname file, but the trailing \00 was only with ROS, not with OpenWRT.

It was annoying, because my dhcp lease-script set static dns names on ROS.

Now the NAS is on Debian and the problem is gone. :slight_smile:

7

Well that is my actual problem with this..

And it doesnt occure on any other Router, regardless of OS…at least so far I havent found any that behaves the same way.
Tried OpenWRT, DD-WRT, Tomato, AsusWRT, IOS, JunOS, etc…

8

http://marc.info/?l=dhcp-client&m=95071885113737&w=2

https://www.isc.org/wp-content/uploads/2013/06/References.html#anchor12