Mailinglist Archive: opensuse (1420 mails)

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Re: [opensuse] optimizing resolv.conf
On 1/4/2014 7:24 AM, Per Jessen wrote:
If you want to be certain 'nscd' is doing the caching, stop it, then
repeat the exercise and notice outgoing DNS traffic on every ping
command.

Yes, this test pretty well proves it.
Interestingly enough, these dns hits do not show up in anything output by nscd
-g
and I suspect that command only shows those things that are relative to files
(passwd, groups, hosts). Nothing specific to dns requests via gethostbyaddr
seems
to be output.

One very telling inidcation is the Chrome Browser running on any machine that
accesses
the network via the box running nscd.

The option in Chrome named
"Use a prediction service to help complete searches and URLs typed in the
address bar"
can flood the network with dns requests if nscd is off.

If you turn off nscd, then call up any web site, and simply erase (backspace)
nodes
of the address, you will see a storm of dns requests.

Example: open your suggested site: www.dns24.ch and you actually arrive at
http://www.dns24.ch/home/welcome
Back space over the trailing "e" causes another dns request.
Backspace over the m and another dns hit is made.

(Someone run over and bitchslap Google for me, m'kay?).

Turn on nscd on the gateway box and those all disappear.






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