28/09/2009

resolv.conf options rotate and discovery of ISP DNS issue

Lately I somehow bumped on the manpage of resolv.conf. While reading it I saw the following really nice option:

rotate               sets  RES_ROTATE  in _res.options, which causes round robin selection of name‐
                     servers from among those listed.  This has the effect of spreading  the  query
                     load  among  all  listed servers, rather than having all clients try the first
                     listed server first every time.

Since then my /etc/resolv.conf on both Gentoo and Debian looks like that:
nameserver 194.177.210.10
nameserver 194.177.210.210
nameserver 194.177.210.211
options rotate

(I prefer using GrNET‘s DNS servers than any others in Greece, especially for my laptop configuration. Since they allow recursion I can use them to avoid lousy DNS services provided by lousy DSL routers regardless of the ISP I am currently using, when I am “mobile” with my laptop.)

While using the following config I issued a ping command on a teminal and a tcpdump command on another to see what was actually happening. The result looked like this:
root@lola:~# tcpdump -ni eth1 port 53
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 96 bytes
11:20:46.405694 IP 192.168.1.65.55154 > 194.177.210.210.53: 39212+ A? ntua.gr. (25)
11:20:46.444266 IP 194.177.210.210.53 > 192.168.1.65.55154: 39212* 1/5/8 A 147.102.222.210 (319)
11:20:46.484490 IP 192.168.1.65.56152 > 194.177.210.211.53: 50452+ PTR? 210.222.102.147.in-addr.arpa. (46)
11:20:46.584171 IP 194.177.210.211.53 > 192.168.1.65.56152: 50452 ServFail 0/0/0 (46)
11:20:46.584449 IP 192.168.1.65.58597 > 194.177.210.10.53: 50452+ PTR? 210.222.102.147.in-addr.arpa. (46)
11:20:46.624179 IP 194.177.210.10.53 > 192.168.1.65.58597: 50452 1/7/6 (357)
11:20:47.484420 IP 192.168.1.65.32818 > 194.177.210.10.53: 33179+ PTR? 210.222.102.147.in-addr.arpa. (46)
11:20:47.524176 IP 194.177.210.10.53 > 192.168.1.65.32818: 33179 1/7/6 (357)
11:20:48.484483 IP 192.168.1.65.57670 > 194.177.210.210.53: 21949+ PTR? 210.222.102.147.in-addr.arpa. (46)
11:20:48.524184 IP 194.177.210.210.53 > 192.168.1.65.57670: 21949 1/3/6 (271)
11:20:49.487610 IP 192.168.1.65.48966 > 194.177.210.211.53: 8619+ PTR? 210.222.102.147.in-addr.arpa. (46)
11:20:49.534204 IP 194.177.210.211.53 > 192.168.1.65.48966: 8619 ServFail 0/0/0 (46)
11:20:49.534429 IP 192.168.1.65.49421 > 194.177.210.10.53: 8619+ PTR? 210.222.102.147.in-addr.arpa. (46)
11:20:49.574138 IP 194.177.210.10.53 > 192.168.1.65.49421: 8619 1/7/6 (357)
11:20:50.494537 IP 192.168.1.65.52525 > 194.177.210.10.53: 3415+ PTR? 210.222.102.147.in-addr.arpa. (46)
11:20:50.534145 IP 194.177.210.10.53 > 192.168.1.65.52525: 3415 1/7/6 (357)
11:20:51.494552 IP 192.168.1.65.40400 > 194.177.210.210.53: 4504+ PTR? 210.222.102.147.in-addr.arpa. (46)
11:20:51.534205 IP 194.177.210.210.53 > 192.168.1.65.40400: 4504 1/3/6 (271)
11:20:52.494554 IP 192.168.1.65.42385 > 194.177.210.211.53: 48450+ PTR? 210.222.102.147.in-addr.arpa. (46)
11:20:52.544197 IP 194.177.210.211.53 > 192.168.1.65.42385: 48450 ServFail 0/0/0 (46)
11:20:52.544409 IP 192.168.1.65.43773 > 194.177.210.10.53: 48450+ PTR? 210.222.102.147.in-addr.arpa. (46)
11:20:52.584232 IP 194.177.210.10.53 > 192.168.1.65.43773: 48450 1/7/6 (357)

People who are used to reading tcpdump output will immediately point out the ServFail entries of the log. Server 194.177.210.211 refused to provide proper results for the PTR query of 210.222.102.147.in-addr.arpa.

Further investigation of the problem:

root@lola:~# dig ptr 210.222.102.147.in-addr.arpa @194.177.210.210
;; QUESTION SECTION:
;210.222.102.147.in-addr.arpa.  IN  PTR
;; ANSWER SECTION:
210.222.102.147.in-addr.arpa. 66841 IN  PTR achilles.noc.ntua.gr.

root@lola:~# dig ptr 210.222.102.147.in-addr.arpa @194.177.210.211
;; QUESTION SECTION:
;210.222.102.147.in-addr.arpa.  IN  PTR

root@lola:~# dig ptr 210.222.102.147.in-addr.arpa @194.177.210.10
;; QUESTION SECTION:
;210.222.102.147.in-addr.arpa.  IN  PTR
;; ANSWER SECTION:
210.222.102.147.in-addr.arpa. 86115 IN  PTR achilles.noc.ntua.gr.

It was obvious that 2 out of 3 DNS servers responded as they should and the other did not.

What I did was to notify a friend working as an administrator there (GrNET) and let him know of the problem. After some investigation, he later on told me that the problem was related to dnssec issues. Possibly a configuration error on RIPE‘s side. As far as I know they had to temporarily disable dnssec on the 147.102 zone…I am not aware whether they fixed the problem (using dnssec) yet though.

I am really glad they acted as fast as possible regarding the solution of the problem 🙂

* Filed by kargig at 21:31 under Linux
Tags: , , , , , , ,
* 3 Comments | 18,915 views

16/09/2009

Uzbl to you too!

I’ve been trying uzbl for the last few days and I am pretty much impressed on how useful such a small application can be in certain usage cases!

I installed it on my Debian testing using the following blog post: Installing uzbl on Debian Squeeze .
Be sure to make install else you’ll have no config and uzbl will be unusable!!!

The first place I used it was for the urlLauncher plugin of urxvt. On my .Xdefaults I have the following piece of code:
urxvt.perl-ext-common: default,matcher,-option-popup,-selection-popup,-realine
urxvt.matcher.button: 1
urxvt.urlLauncher: /usr/local/bin/urxvt-url.sh

and my /usr/local/bin/urxvt-url.sh contains:
#!/bin/sh
uzbl "$1"

Now every url on the console get’s highlighted and I can open it with uzbl. And that means opening really fast!

Example:
urxvt terminal (tabbed by fluxbox) with some urls highlighted by the perl matcher plugin of urxvt:
urxvt-url-highlight

left clicking on one of the urls opens it with uzbl:
uzbl-window

Apart from that, I’ve started using uzbl to open links on instant messengers, IRC clients and in every other place that people send me simple links to check out or I need a fast browser instance. Some people might say that it looks like links2 graphical mode, but it’s NOT like opening urls with “links -G” because uzbl is based on webkit and that means it can deal with javascript, java, flash, whatever…

I just love the way you can keybind all the actions you want on it…on the example config that comes with it, you quit the browser by typing ZZ…how great is that ? 😀

Some usage tips
1) Tabbed behavior (if you have fluxbox):
In ~/.config/uzbl/config add
bind t _ = spawn uzbl --uri %s
and in ~/.fluxbox/apps add the [group] tag before the [app] tag for uzbl like that:

[group]
 [app] (name=uzbl) (class=Uzbl)
  [Workspace]   {0} 
  [Head]    {0} 
  [Dimensions]  {800 1284}
  [Position]    (UPPERLEFT) {0 0}
  [Maximized]   {yes}
  [Jump]    {yes}
  [Close]   {yes}
[end]

Now the command t www.google.com inside uzbl, will open a new tabbed window of uzbl with www.google.com loaded in it.

2) Close uzbl window with ctrl+w
In ~/.config/uzbl/config add:

bind     ctrl+v ctrl+w    = exit

(press ctrl+v ctrl+w one after the other and you will get something like ^W in the file)

P.S. If you are a person that just came from the point and click windows world to the beautiful world of linux, or you are a person that loves bloated desktop managers like KDE/gnome/etc or bloated applications like firefox/iceweasel/konqueror don’t even think of installing it. You’ll never understand its value…
P.S.2. If Richard Stallman decided to browse the web and had an internet connection uzbl would probably be his browser of choice 😛

* Filed by kargig at 17:15 under Linux
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* 7 Comments | 15,073 views

12/09/2009

Playing with Synergy on Gentoo and Debian

I currently have Gentoo/x86 on my desktop system and Debian/testing on my laptop. I wanted a way to be able to use the laptop’s trackpad to control the cursor on the desktop or to use the desktop’s mouse to control the cursos on the laptop. Thankfully I was able to do that with Synergy.

On Gentoo:
# emerge x11-misc/synergy
On Debian:
# aptitude install synergy

My config is pretty simple. That’s Debian’s (hostname lola) /etc/synergy.conf:

section: screens
    lola:
    athlios:
end

section: links
    lola:
        right = athlios
    athlios:
        left  = lola
end

section: aliases
    lola:
        mac 
end

When I want to control athlios (desktop) from lola (laptop), I start synergys on lola, ssh to athlios and start synergyc lola. That’s it, I can then control desktop’s mouse and keyboard from laptop’s touchpad and keyboard. When I move the lola’s cursor far to the right, the cursor starts moving on the desktop. Then if I start typing on the laptop’s keyboard I am actually typing on the desktop. Moving the cursor far to the left of the desktop’s monitor, the cursor starts moving again on the laptop.

A problem that I faced was that some keys (Left and Down arrow) stop repeating if you press them continuously when you start synergyc. The solution is posted on the synergy article on gentoo wiki. You just have to type: xset r 113 (left arrow) and xset r 116 (down arrow) to activate them, then move your mouse to the synergy server and back to the synergy client. If you try typing on the machine where the synergy client has started using its keyboard you will see that repeating doesn’t work at all. Just type xset r to get it back working if you need it.

For people having more than one machine on their desk, synergy is a real salvation in order to stop switching keyboards and mice all the time.

* Filed by kargig at 15:25 under Linux
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* 3 Comments | 11,767 views