Feedback on proposal to stop the DHCPINFORM flooding

[eramoli]

Hi all,

I have for a while been annoyed about all the dnsmasq entries in the daemon.log file and today I think I found a way to reduce them. Windows 7 (and other Microsoft OSs) asks for a proxy using DHCP. The issue is that they do not stop until they have received an answer. Since the B3 do not have such information Windows will ask ask and ask again.

Seraching the Internet suggested that adding <dhcp-option=252,”\n”> to the dnsmasq.conf file would solve the issue. I am now writing a entry for the Wiki and would like someone else to verify the text before I put it up there.

• Does this work for you?
• My thinking was to put it in the new file instead of adding it to the dnsmasq.conf file. Correct approach?
• Can you see any drawbacks with this?

Wiki Entry
Windows among others ask for proxy settings using DHCP. The issue is that they do not stop asking until they have received an answer. This results in that the log contains a lot information about these requests.

Jul 1 06:34:09 MorganB3 dnsmasq-dhcp[1638]: DHCPINFORM(br0) 10.69.10.59 00:23:14:c5:33:fc
Jul 1 06:34:09 MorganB3 dnsmasq-dhcp[1638]: DHCPACK(br0) 10.69.10.59 00:23:14:c5:33:fc MorgansVaioF12Z

This wiki entry describes how to modify the B3 to stop this traffic.
Configuration
No specific configuration information is needed
Packages
No new packages is needed
Setup
Login to the B3 and become the root user

Code: Select all

su

Go the the dnsmasq config directory and create a new file

Code: Select all

cd /etc/dnsmasq.d
touch no_proxy.conf

Add the following text into the file

# This will tell DHCP clients to not ask for proxy information
# Some clients, like Windows 7, will constantly ask if not told NO
dhcp-option=252,"\n"

Restart DNS
We are now completed so let us restart the server

Code: Select all

/etc/init.d/dnsmasq restart

Test
Look at the log, you should only see one more DHCPINFORM entry per computer connected to the B3, then they should stop asking for proxy information.

Code: Select all

tail -f /var/log/daemon.log

[Gordon]

Hi Morgan,

The only Windows I have here is XP and I'm not seeing the issue you report. However I do know that later Windows does behave differently in regards to networking and this very much sounds like it could be "one of those things".

I like your solution - it's simple and it's clean and I'm confident that if the "\n" option value works in your case, it will work for everyone else when using the described method. Good job!

[DanielM]

Works here. I found the lines in my log (both from Windows 7 and Windows XP) but not anymore. Always glad to have solved a problem that I didn't know existed

/Daniel

[eramoli]

Hi,

Thanks Gordon and Daniel. I will then add it to the wiki.

Best Regards,
Morgan

[eramoli]

Now it can be found on this http://wiki.excito.org/wiki/index.php/S ... M_flooding

[johannes]

Thanks, appreciated! Added as a feature request in our tracker, probably to be included in some future release.