Ikke's Blog

I've been playing with creating GTK+ widgets using Cairo lately. As I had to write some text for some bloody Word-task (university stuff) I started writing a widget for an "OXO" game, and make a little tutorial on how to make something alike. The task is done (I even had to remove some parts of the text :(), the tutorial isn't finished yet as there are some issues left with the widget.

Anyway, writing 2D drawing code using Cairo is really fun. Sometimes you need some maths to get some tasks done, but it's fun to experiment and the possibilities are almost endless.

Here's a little sample of what I got now, click on the image for a full-scale screenshot:

Some parts of the "logics" inside the widget are still buggy (-> the code to check whether a move is a winning one or not).

I start to get rid of the spammers on my blog. There's still some comment- and trackback-spam, but at least most spambots can't leech several gigabytes of my bandwith anymore. There are still requests done, but they get a 300byte answer, or even less.
One issue left: if I get 2 identical requests (same HTTP_REQUEST, HTTP_REFERER etc), one using HTTP/1.0 and one using HTTP/1.1, my mod_rewrite rules generate another response: 403 (5 bytes) when using HTTP/1.0, 301 (352 bytes) when using HTTP/1.1:

216.195.35.XX - - [16/Dec/2005:14:24:58 +0100] "GET /index.php/all?skin=stockholm HTTP/1.1" 403 5 "http://spamhost/" "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.0.3705; .NET CLR 1.1.4322)"
216.195.35.XX - - [16/Dec/2005:14:25:05 +0100] "GET /index.php/all?skin=stockholm HTTP/1.1" 301 352 "http://spamhost/" "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.0.3705; .NET CLR 1.1.4322)"

Can anyone explain me what causes this?

Thanks to RubenV who helped me out when creating the mod_rewrite rules :)

Ikke • Technology, Linux, Desktop, Coding Corner 1 comment

Sigh. Luckily we got Nat ;-)
I still got my lockups on high IO load, or my mouse starting to go all over the screen and generating random clicks while doing so on high load, after which I get warnings in dmesg the psmouse driver lost ticks. Guess what part of my machine's stack causes that B-)

Ikke • Linux, Desktop Leave a comment

Although I'm not a big Ubuntu lover, this is most certainly a good thing.
Who doesn't know the "Metro"? :-)

[edit] Looks like Peter saw it too ;-)

Ikke • Linux 4 comments

After my previous article on Valgrind I started using it more and more, and discovered another nice feature of it. Just check this sample:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

#define MESSAGE "test"

int main(int argc, char *argv[]) {
        char *t = NULL;

        /* Hey, everyone makes mistakes */
        t = (char *)malloc(strlen("" MESSAGE) * sizeof(char));
        assert(t != NULL);
        strcpy(t, "" MESSAGE);

        printf("%s\n", t);

        free(t);

        return 0;
}

Compiling and running looks ok:

$ gcc -g -Wall -Werror -o test2 test2.c
$ ./test2
test

But luckily there's Valgrind to tell us the code is horribly wrong:

$ valgrind --tool=memcheck ./test2
==13483== Memcheck, a memory error detector for x86-linux.
==13483== Copyright (C) 2002-2004, and GNU GPL'd, by Julian Seward et al.
==13483== Using valgrind-2.2.0, a program supervision framework for x86-linux.
==13483== Copyright (C) 2000-2004, and GNU GPL'd, by Julian Seward et al.
==13483== For more details, rerun with: -v
==13483==
==13483== Invalid write of size 1
==13483==    at 0x1B906485: strcpy (mac_replace_strmem.c:199)
==13483==    by 0x80484B2: main (test2.c:14)
==13483==  Address 0x1BA5C02C is 0 bytes after a block of size 4 alloc'd
==13483==    at 0x1B906B82: malloc (vg_replace_malloc.c:131)
==13483==    by 0x8048472: main (test2.c:12)
==13483==
==13483== Invalid read of size 1
==13483==    at 0x1B968B6B: _IO_vfprintf (in /lib/tls/libc-2.3.5.so)
==13483==    by 0x1B96DF36: _IO_printf (in /lib/tls/libc-2.3.5.so)
==13483==    by 0x1B93DF36: __libc_start_main (in /lib/tls/libc-2.3.5.so)
==13483==  Address 0x1BA5C02C is 0 bytes after a block of size 4 alloc'd
==13483==    at 0x1B906B82: malloc (vg_replace_malloc.c:131)
==13483==    by 0x8048472: main (test2.c:12)
test
==13483==
==13483== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 13 from 1)
==13483== malloc/free: in use at exit: 0 bytes in 0 blocks.
==13483== malloc/free: 1 allocs, 1 frees, 4 bytes allocated.
==13483== For a detailed leak analysis,  rerun with: --leak-check=yes
==13483== For counts of detected errors, rerun with: -v

This should be fairly self-explaining... I guess most C programmers forgot to allocate strlen(msg)+1 (the end '\0') at least once in their life...

By the way: hello Planet Grep :-)

Ikke • Coding Corner 5 comments

Lately I've been working on the new webserver machine for VTK. Today I configured mod_security for Apache2, partially by using the rules one can find on gotroot.com.
On the site a little script is provided to update the rules automagicly (in a cronjob or something alike), but when I started using the script I didn't like it for several reasons.
So I decided to rewrite it to suit my needs. You can find my enhanced version here.

The machine now also runs PHP4 and PHP5 side by side thanks to this great documentation (and the Gentoo PHP herd developers, obviously). PHP4 as an Apache module (because this is the "default", so it must run as efficient as possible), PHP5 using the CGI interface for all .php5 files.
We can't make "the big switch" to a PHP5-only server due to our bloody PhpBB forum which is not PHP5 compatible. And as our forum is one of the biggest PHP consumers on the server, I don't want to run PHP4 as CGI and only run the forum this way.

[edit]
I enhanced the script a little more, here's a diff:

--- update_mod_security_rules.sh        2005-12-02 14:46:02.000000000 +0100
+++ update_rules_v2.sh  2005-12-04 14:34:33.000000000 +0100
@@ -15,6 +15,7 @@
 APACHESTART="/etc/init.d/apache2 restart"
 MODSECPATH="/etc/modsecurity"
 APACHEPID="/var/run/apache2.pid"
+APACHECTL="/usr/sbin/apache2ctl"

 #Modules
 #If you want the "exclude" rules, they should be the first entry in the list
@@ -59,10 +60,21 @@

 echo "Make sure you got \"Include ${MODSECPATH}/all.conf\" somewhere in your Apache config"

+${APACHECTL} configtest > /dev/null 2>&1
+if [ ! "x$?" = "x0" ]; then
+        echo
+        echo "There's something wrong in Apache's configuration:"
+        echo
+        ${APACHECTL} configtest
+        echo
+        echo "Exiting, not restarting Apache"
+        exit 1
+fi
+
 # try restart
 if [ "$UPDATED" -gt "0" ]; then
         echo -n "Restarting apache: "
-        /bin/kill -HUP ${PID} 2>/dev/null
+        ${APACHECTL} graceful
         # did it work?
         if `/bin/kill -CHLD ${PID} >/dev/null 2>&1`; then
                 echo "ok."

The script

Ikke • Technology, Linux, Networks 2 comments