Linux Calling...

Thursday, January 12, 2017

VirtualBox Copy/Paste not working?

Open the settings (Host Key (usually right ctrl) + s) > Advanced > Shared Clipboard > Enable

Fire the below command and restart the VM

sudo apt-get install virtualbox-guest-dkms

Hope this helps!

Saturday, July 23, 2016

Installing Nagios Core without "root" permission

Complete guide to install Nagios in Linux without "root" permission

1) Installing HTTPD

# All the installation will be done under /home/maximus/tools

wget http://www-eu.apache.org/dist//httpd/httpd-2.4.23.tar.gz
wget http://www-eu.apache.org/dist//apr/apr-util-1.5.4.tar.gz
wget http://www-eu.apache.org/dist//apr/apr-1.5.2.tar.gz

tar -xzvf httpd-2.4.23.tar.gz
tar -xzvf apr-1.5.2.tar.gz
tar -xzvf apr-util-1.5.4.tar.gz

cp -r apr-1.5.2 httpd-2.4.23/srclib/apr
cp -r apr-util-1.5.4 httpd-2.4.23/srclib/apr-util
cd httpd-2.4.23
./configure --prefix=/home/maximus/tools -with-included-apr
make
make install

2) Install PHP

wget http://php.net/get/php-7.0.9.tar.gz
tar -xzvf php-7.0.9.tar.gz
cd php-7.0.9
./configure --prefix=/home/maximus/tools --with-apxs2=/home/maximus/tools/bin/apxs --with-config-file-path=/home/maximus/tools/conf/
make
make install
cp php.ini-development /home/maximus/tools/conf/php.ini

# Add the following lines in /home/maximus/tools/conf/httpd.conf to enable PHP and CGI,
# and to change the default HTTP port no

Listen 5555
LoadModule cgid_module modules/mod_cgid.so
LoadModule php7_module modules/libphp7.so
<FilesMatch \.php$>
SetHandler application/x-httpd-php
</FilesMatch>

3) Install GD

wget http://www.boutell.com/gd/http/gd-2.0.33.tar.gz
tar -xzvf gd-2.0.33.tar.gz
cd gd-2.0.33
./configure --prefix=/home/maximus/tools/
make
make install

4) Install Nagios

wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.1.1.tar.gz
tar -xzvf nagios-4.1.1.tar.gz
cd nagios-4.1.1

# maximus is a non-previliged user. eng is the group which maximus belongs to.
# Feel free to change it as per your needs
./configure --prefix=/home/maximus/tools/nagios --with-cgiurl=/nagios/cgi-bin --with-htmurl=/nagios/ --with-nagios-user=maximus --with-nagios-group=eng --with-command-group=eng --with-gd-lib=/home/maximus/tools/lib --with-gd-inc=/home/maximus/tools/include --with-httpd-conf=/home/maximus/tools/conf
make all
make install

# In the Makefile (in current directory) add the entry DESTDIR=/home/maximus/tools/
# and the execute the next command
make install-init
# Now remove the entry which we just added
make install-commandmode
make install-config
make install-webconf
cp -R contrib/eventhandlers/ /home/maximus/tools/nagios/libexec/

# Provide a password for the user nagiosadmin (you can chose your own username).
# You will be using this login to the Nagios Core Web
cd /home/maximus/tools/nagios/etc/
htpasswd -c htpasswd.users nagiosadmin

# Add the following line to /home/maximus/tools/conf/httpd.conf

Include conf/nagios.conf

5) Install the Nagios Core Plugins

wget http://www.nagios-plugins.org/download/nagios-plugins-2.1.1.tar.gz
tar -xzvf nagios-plugins-2.1.1.tar.gz
cd nagios-plugins-2.1.1
./configure --with-nagios-user=maximus --with-nagios-group=eng --prefix=/home/maximus/tools/nagios/
make
make install

To start the all the services
/home/maximus/tools/bin/apachectl start
/home/maximus/tools/etc/rc.d/init.d/nagios start

To stop the all the services
/home/maximus/tools/bin/apachectl stop
/home/maximus/tools/etc/rc.d/init.d/nagios stop

Web Address
http://localhost:5555/nagios/index.php

Hope this helps!!

Sunday, March 20, 2016

HC-SR04 with Raspberry Pi - Distance

HC-SR04 (Ultrasonic Module) interfacing with Raspberry Pi for distance calculation.

Will provide the schematics soon.

/*
 * HC-SR04 <> RPi
 * To calculate the distance
 * Using the libbcm2835 library
 * Author : Ahamed EN (ahamed.en@gmail.com)
 * 20-March-2016
 */
#include <bcm2835.h>
#include <stdio.h>
#include <sys/time.h>

/* We will be using
 * Pin#16 (GPIO23) as Trigger
 * Pin#18 (GPIO24) for Echo
 */
#define TRIGGER RPI_GPIO_P1_16
#define ECHO    RPI_GPIO_P1_18

int main(int argc, char **argv)
{

    if (!bcm2835_init())
        return 1;

    struct timeval start, end;
    float duration;

    bcm2835_gpio_fsel(TRIGGER, BCM2835_GPIO_FSEL_OUTP);
    bcm2835_gpio_fsel(ECHO, BCM2835_GPIO_FSEL_INPT);

    bcm2835_gpio_write(TRIGGER, LOW);
    bcm2835_gpio_write(ECHO, LOW);
    bcm2835_delay(2);

    bcm2835_gpio_write(TRIGGER, HIGH);
    usleep(10); /* As per the HC-SR04 manual */
    bcm2835_gpio_write(TRIGGER, LOW);

    /* Wait until we get a HIGH */
    while(!bcm2835_gpio_lev(ECHO));
    gettimeofday(&start, NULL);

    /* Wait until we get a LOW */
    while(bcm2835_gpio_lev(ECHO));
    gettimeofday(&end, NULL);

    /*
     * speed = distance/time
     * speed = 340m/s = 34300cm/s (speed of sound)
     *
     * 34300 = distance/time
     *
     * distance = time/2 * 34300 (time/2 because what we got is the time
     *                              for to and fro)
     */

    duration = (end.tv_sec - start.tv_sec) * 1000.0;
    duration += (end.tv_usec - start.tv_usec) / 1000.0;
    duration = duration/1000; /* to seconds */

    float distance = duration/2 * 34300;

    printf("Disatnce : %f cm\n", distance);

    bcm2835_delay(500);
    bcm2835_close();
    return 0;
}

Interfacing SIM800 module with Raspberry Pi via Serial Interface C program

Interfacing SIM800 module with R-Pi via Serial Interface using C program. Following program sends an SMS to the specified mobile number.

This program uses the normal C routines

R-Pi SIM800

Pin#06(GND) -------- GND
Pin#08(TXD0) -------- Rx
Pin#10(RXD0) -------- Tx

root@raspberrypi:~/sim# gcc send.c -o send_sms

root@raspberrypi:~/sim# ./send_sms
Writing to Port : AT
Read from port  : ATOK
Writing to Port : AT+CMGF=1
Read from port  : AT+CMGF=1OK
Writing to Port : AT+CNMI=2,1,0,0,0
Read from port  : AT+CNMI=2,1,0,0,0OK
Writing to Port : AT+CMGS="9535213788"
Read from port  : AT+CMGS="9535213788">
Writing to Port : PI_SIM800_TESTING

The received SMS

/*
 * SIM800 <> Raspberry Pi - Serial Interface
 * To send a SMS using SIM800 module via RPi
 * Author : Ahamed EN (ahamed.en@gmail.com)
 * Date : 20 March 2016
 */

#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <termios.h>

/* This is R-Pi default serial port */
#define DEFAULT_PI_SERIAL_PORT "/dev/ttyAMA0"

typedef enum _mode_t{
    RW,
    WO,
    RO
}sim_mode_t;

static inline void error(char *err)
{
    printf("Error : %s\n", err);
}

#define ERROR(err) { printf("[%s %d] ", __func__, __LINE__); error(err); }

int open_serial_dev(char *serial_dev)
{

    if(!serial_dev){
        ERROR("serial_dev in NULL");
        return -1;
    }

    int fd;

    fd = open(serial_dev, O_RDWR | O_NOCTTY | O_NDELAY);
    if(fd < 0){
        ERROR("Could not open the serial device");
        return -1;
    }
    return fd;

}

/* To initialize the serial port via termios */
int serial_init(int fd)
{

    struct termios termios;
    int ret = 0;

    ret = tcgetattr (fd, &termios);
    if(ret < 0){
        ERROR("tcgetattr failed");
        return -1;
    }

    cfsetispeed(&termios, B9600);
    cfsetospeed(&termios, B9600);

    termios.c_iflag &= ~(IXANY | IXON | IXOFF);
    termios.c_lflag &= ~(ICANON | ECHO);
    termios.c_cflag |= (CLOCAL | CREAD);

    termios.c_cc[VMIN]  = 1;
    termios.c_cc[VTIME] = 10;

    ret = tcsetattr (fd, TCSANOW, &termios);
    if(ret < 0){
        ERROR("tcsetattr failed");
        return -1;
    }


    return 0;
}

void set_cmd(char *cmd, char *cmd_str)
{
    memset(cmd, 0, sizeof(cmd));
    strcpy(cmd, cmd_str);
}

int read_port(int fd, int ret)
{
    int rv = 0;
    int i = 0;
    char buf[64];
    if(ret){
        rv = read(fd, &buf, sizeof(buf));
        printf("Read from port\t: ");
        for(i=0; i<rv; i++){
            if(buf[i] == '\n' || buf[i] == '\r') continue;
            printf("%c", buf[i]);
        }
        printf("\n");
    }
    return rv;
}

int write_port(int fd, char *cmd, int len)
{
    if(fd < 0){
        ERROR("Invalid fd");
        return -1;
    }

    printf("Writing to Port\t: %s", cmd);

    int ret = 0;
    ret = write(fd, cmd, len);
    if(ret <= 0){
        ERROR("write failed");
    }
    return ret;

}

/* Function to write and read from the port */
void set_get_cmd(int fd, sim_mode_t mode, char *cmd_str)
{
    int ret;
    char cmd[64];
    set_cmd(cmd, cmd_str);
    ret = write_port(fd, cmd, strlen(cmd));
    usleep (100000);
    if(mode == WO){
        return;
    }
    read_port(fd, ret);
    return;

}

int main(int argc, char **argv)
{

    char *serial_dev = DEFAULT_PI_SERIAL_PORT;
    int ret = 0;
    int fd;


    if(argv[1]){
        serial_dev = argv[1];
    }

    fd = open_serial_dev(serial_dev);
    if(fd < 0){
        ERROR("Exiting");
        return -1;
    }

    ret = serial_init(fd);
    if(ret < 0){
        ERROR("Exiting");
        return -1;
    }

    /* Check the SIM800 Data sheet for the commands */

    set_get_cmd(fd, RW, "AT\r\n");
    set_get_cmd(fd, RW, "AT+CMGF=1\r\n");
    set_get_cmd(fd, RW, "AT+CNMI=2,1,0,0,0\r\n");

    /* Specify the 10 digit mobile # here */
    set_get_cmd(fd, RW, "AT+CMGS=\"9535213788\"\r\n");

    /* Following is your text message */
    set_get_cmd(fd, WO, "PI_SIM800_TESTING\r\n");

    set_get_cmd(fd, WO, "\x1A");

    printf("\n");

    return 0;

}

Monday, June 1, 2015

Guide to Linux Driver

/dev/hello_world: A Simple Introduction to Device Drivers under Linux - O'Reilly Media

Thursday, May 28, 2015

CCIE Data Center :: Nexus :: FabricPath Overview

Tuesday, May 26, 2015

Multicast Part 1 - Intro

Python Series

Monday, May 25, 2015

Introduction to Cloud Overlay Networks - VXLAN

CCNP Tutorial: GRE Tunnels

Tuesday, June 3, 2014

Merge Sort

Merge sort is one of the efficient sorting algorithms compared to other sorts as Insertion, Selection or Bubble Sort. The algorithm is divide and conquer. We divide the array into 2, sort the 2 arrays and then merge them to form the final result. This is of course a recursive technique. As you can see in the below code, the function merge_sort() is called recursively.
The time complexity is O(nlogn).
In this example, the array is self populated with random values with the help of srand() series of functions after taking the size of the array from the user.

#include "stdio.h"
#include "stdlib.h"
#include "string.h"
#include "time.h"

typedef enum _return_type
{
  ERROR,
  SUCCESS
}return_type_t;

#define NULL_CHECK(x) { if(!x) return ERROR; }

static int merge(int *a1, int n1, int *a2, int n2, int *a)
{

  int i=0, j=0, k=0;

  while(i<n1 && j<n2){
    if(a1[i] <= a2[j]){
      a[k] = a1[i];
      i++;
    }
    else{
      a[k] = a2[j];
      j++;
    }
    k++;
  }

  while(i<n1){
    a[k] = a1[i];
    i++;
    k++;
  }

  while(j<n2){
    a[k] = a2[j];
    j++;
    k++;
  }
  return SUCCESS;
}

static int merge_sort(int *a, int m)
{
  int *a1, *a2;
  int n1, n2;

  if(m<2) return SUCCESS;

  n1 = m >> 1;
  n2 = m - n1;

  a1 = malloc(sizeof(int) * n1);
  NULL_CHECK(a1);
  a2 = malloc(sizeof(int) * n2);
  NULL_CHECK(a2);

  int i=0;
  for(i=0; i<n1; i++)
    a1[i] = a[i];

  for(i=0; i<n2; i++)
    a2[i] = a[i+n1];

  merge_sort(a1, n1);
  merge_sort(a2, n2);

  merge(a1, n1, a2, n2, a);
  free(a1);
  free(a2);

  return 0;

}

static void display(int *a, int n)
{
  int i;
  for(i=0; i<n; i++){
    printf("%d ", a[i]);
  }
  printf("\n");
  return;
}

int main(int argc, char **argv)
{
  int *a;
  int i,n,num;

  scanf("%d", &n);
  a = malloc(sizeof(int) * n);
  NULL_CHECK(a);

  srand ( time(NULL) );

  for(i=0; i<n; i++){
    num = rand() %1000 + 1;
    a[i] = num;
  }

  //display(a, n);
  merge_sort(a, n);
  //display(a, n);

  free(a);
  return 0;
}

Monday, April 14, 2014

Squid HTTPS/SSL Proxy

A customer was reporting poor performance with one of the product I am working on when he routes the traffic via squid proxy. What is a proxy? Why Squid? Just google it :). Let's get down to business.

Below is the topology. This is a basic setup so that you can get started.

All the machines here are running Kali Linux.

root@maximus:~# uname -a
Linux maximus 3.12-kali1-686-pae #1 SMP Debian 3.12.6-2kali1 (2014-01-06) i686 GNU/Linux

Important while installing the Squid Proxy
Try to get the source file and compile it. While configuring, make sure to give the following switches to ensure SSL is supported.

--enable-ssl --enable-ssl-crtd --enable-icap-client --with-default-user=squid

--with-default-user
You can specify any user you want, just make sure after the installation is done, that user is created and necessary permissions are given. Mainly "that user" will require permission to write to the log directories which is by default /var/logs/

Follow these to get the Squid Proxy installed

wget http://www.squid-cache.org/Versions/v3/3.4/squid-3.4.4.tar.gz
tar -xzvf squid-3.4.4.tar.gz
cd squid-3.4.4
./configure --prefix=/ --enable-icap-client --enable-ssl --enable-ssl-crtd --with-default-user=squid
make
make install

Once done, execute squid -v and squid -h to ensure we have ssl enabled and also to know the path of the configuration file

root@maximus-neptune-21:~# squid -v
Squid Cache: Version 3.4.4
configure options:  '--enable-ssl' '--enable-icap-client' '--enable-ssl-crtd' '--with-default-user=squid' '--prefix=/' --enable-ltdl-convenience

root@maximus-neptune-21:~# squid -h
Usage: squid [-cdhvzCFNRVYX] [-s | -l facility] [-f config-file] [-[au] port] [-k signal]
       -a port   Specify HTTP port number (default: 3128).
       -d level  Write debugging to stderr also.
       -f file   Use given config-file instead of
                 /etc/squid.conf
       -h        Print help message.

We are good to go!

This is what happens when the client tries to connect to the proxy server.

Client tries to connect to the proxy server via https://172.20.73.172:3128
The proxy server, intercepts this and establishes a secure connection between the Client and itself. Then the proxy server creates another secure back-end connection to the actual server.

Though this is transparent mode, you can see that it is not "entirely" transparent to the the client. The reason I am connecting to the proxy server and port explicitly is because I didn't want the readers to get confused with the iptables. This is known as ssl-bump or man in the middle. The original connection from the client is intercepted by the proxy server. So, if anyone hacks into the proxy server, he can get all the data easily. Like, I have already said, this is only for lab testing purpose.

Below is the minimal configuration file /etc/squid.conf

visible_hostname maximus-neptune-21

# This acl will allow anyone. Add the required acl's you want to restrict the access.
acl EVERYONE src all

# This is to tell the Proxy that do not cache the pages. This is not generally used.
cache deny all

# This is where the acl is getting into action
http_access allow EVERYONE
http_access deny all

# 3128 is the https port squid proxy will listen to. You need to generate the key and certificate, these are used to create a secure connection with the client. I am using SSLv3 and hence version=3
https_port 3128 intercept ssl-bump cert=/etc/squid/ssl/public.pem key=/etc/squid/ssl/private.pem version=3

# This is where we specify the server list. I am using SSLv3 and hence sslversion=3
cache_peer 100.1.1.11 parent 443 0 no-query originserver ssl sslversion=3 ssloptions=NO_SSLv2,NO_TLSv1_1,NO_TLSv1_2

# I had some issues with the CA, hence disabled the verification. I don't recommend you do this if it a live environment.
sslproxy_cert_error allow all
sslproxy_flags DONT_VERIFY_PEER,NO_DEFAULT_CA

# This will ensure that the connection is send/created to the actual server.
never_direct allow all

Start the Squid Proxy in foreground mode with certain debug level enabled. This will help in finding any configuration syntax errors or any handshake failures etc

squid -NCd1

Check /var/logs/access.log for more debugging information.

For more information, please check http://www.squid-cache.org/
Reference : http://www.squid-cache.org/

Friday, February 21, 2014

Convert UTC Date to Seconds

One of the primary ways used to compare dates is to convert the date to seconds and then do the comparison. The GNU date has an option +%s to convert the given date to seconds since epoch. But sometimes GNU date is not available in all the systems and they can't install it due to restrictions in the working environment. The next option is to use strftime() of gawk or perl. The same issue may exist with gawk/perl also, i.e. they may not have the required libs or things of that sort.

The following script which I call utc_to_sec will convert the given UTC date to seconds using the basic arithmetic.

#!/bin/bash
# utc_to_sec v1.0
# Script to convert time to seconds
# TZ should be UTC
#
# ./utc_to_sec 2014-02-20  01:42:02
# 1392860522

EXE=${0#*/}
usage()
{
  echo -e "\nConvert date to seconds since epoch"
  echo "  Usage : $EXE yyyy-mm-dd hh:mm:ss"
  echo -e "  ** TZ default UTC **\n"
  exit
}

do_everything()
{
  echo $1 $2 | awk '

    BEGIN{
      year=hh=1; mon=mm=2; day=ss=3
      m_lo[4]=m_lo[6]=m_lo[9]=m_lo[11]=1
      m_hi[1]=m_hi[3]=m_hi[5]=m_hi[7]=m_hi[8]=m_hi[10]=m_hi[12]=1
    }

    function no_of_days_in_year(input)
    {
      leap=0
      if ( input%4 == 0 ){
        if ( input%100 == 0 ){
          if ( input%400 == 0 ){
            leap=1
          }
        }
        else{
          leap=1
        }
      }

      return (365+leap)
    }

    function no_of_days_in_month(in_mon, in_year)
    {
      if(m_hi[in_mon]) val=31
      else if(m_lo[in_mon]) val=30
      else {
        val= no_of_days_in_year(in_year)>365?29:28
      }
      return val
    }

    function validate(a_date, a_time)
    {
      if( a_date[year]<1970 || a_date[mon]<=0 || a_date[mon]>12 ||
          a_date[day]<=0 || a_date[day]>31 ||
          ( m_lo[a_date[mon]] && (a_date[day]>30) ) ||
          ( a_date[mon]==2 && a_date[day]>29 ) ||
          a_time[hh]<0 || a_time[hh]>23  ||
          a_time[mm]<0 || a_time[mm]>=60 ||
          a_time[ss]<0 || a_time[ss]>=60 ){
        print -1
        exit
      }
      if(no_of_days_in_year(a_date[year])<=365 && a_date[mon]==2 && a_date[day]>28){
        print -2
        exit
      }
    }

    END{
      split($1, a_date, /-/)
      split($2, a_time, /:/)
      validate(a_date, a_time)

      #no of days in a year
      for(i=1970; i<a_date[year]; i++)
        sum_days+=no_of_days_in_year(i)

      for(i=1; i<a_date[mon]; i++)
        sum_days+=no_of_days_in_month(i, a_date[year])

      sum_days=sum_days+a_date[day]-1
      seconds = (sum_days*24*60*60) + (a_time[hh] * 3600) + (a_time[mm] * 60) + a_time[ss]
      print seconds
    }
  '
}

( [[ $# -ne 2 ]] ) && usage
seconds=$( do_everything $* )
[[ ${seconds:-0} -lt 0 ]] && echo "Invalid data..." && usage
echo $seconds

Output

root@maximus:~/scripts# ./utc_to_sec 2037-12-31 23:59:59
2145916799
root@maximus:~/scripts# date +%s -d "2037-12-31 23:59:59 UTC"
2145916799
root@maximus:~/scripts# ./utc_to_sec 2014-02-19 12:13:56
1392812036
root@maximus:~/scripts# date +%s -d " 2014-02-19 12:13:56 UTC"
1392812036
root@maximus:~/scripts# ./utc_to_sec 1970-01-01 00:00:00
0
root@maximus:~/scripts# date +%s -d "1970-01-01 00:00:00 UTC"
0
root@maximus:~/scripts# date +%s -d "1990-01-01 23:40:44 UTC"
631237244
root@maximus:~/scripts# ./utc_to_sec 1990-01-01 23:40:44
631237244

Execution time

root@maximus:~/scripts# time date +%s -d "2037-12-31 23:59:59 UTC"
2145916799

real    0m0.010s
user    0m0.004s
sys     0m0.008s

root@maximus:~/scripts# time ./utc_to_sec 2037-12-31 23:59:59
2145916799

real    0m0.023s
user    0m0.012s
sys     0m0.004s

HTH

Wednesday, January 29, 2014

Determining IP address range from Subnet/CIDR

Script to find the IP address range from the given Subnet.

There are few functions which can be reused like
1. Convert IP to Decimal ip_to_int()
2. Convert Decimal to IP int_to_ip()
3. Netmask to CIDR to_cidr()

#!/bin/bash
# http://linuxcalling.blogspot.in/
# Script to find the IP address range
# Script : ip_range
# Usage  : ip_range <IP> <Subnet> [0|1 print range]
# Ahamed (ahamed.en@gmail.com)

usage()
{
  EXE=${0#*/}
  echo "Usage: $EXE <IP> <Subnet> [0|1]<print range>"
  echo "   eg: To display the IP address range"
  echo "       $EXE 192.168.1.1 255.255.140.0"
  echo "   eg: To display the IP address range with entire range"
  echo "       $EXE 192.168.1.1 255.255.140.0 1"
  exit
}

[ $# -lt 2 ] && usage

echo $1 $2 $3 | awk '

  BEGIN{
    BITS=8
    mask_add[0]=valid_subnet[0]=0
    for(i=BITS-1;i>=0;i--){
      k=or(k,lshift(1,i))
      mask_add[k]=BITS-i
      valid_subnet[BITS-i]=k
    }
  }
  function validate_subnet(input)
  {
    split(input, oc, ".")

    if(oc[4] > oc[3] || oc[3] > oc[2] || oc[2] > oc[1]){
        print "Invalid Subnet: ",input
        exit
    }
    for(j=1; j<=BITS/2; j++){
      for(i=0;i<=BITS;i++){
        if(!xor(oc[j],valid_subnet[i])){
          break;
        }
        err++
      }
      if(err == (BITS+1)){
        print "Invalid Subnet: ",input
        exit
      }
      err=0
    }
  }

  function to_cidr(input)
  {
    split(input, oc, ".")
    ret=mask_add[oc[1]]+mask_add[oc[2]]+mask_add[oc[3]]+mask_add[oc[4]]
    return ret
  }

  function ip_to_int(input)
  {

    split(input, oc, ".")
    ip_int=(oc[1]*(256^3))+(oc[2]*(256^2))+(oc[3]*(256))+(oc[4])
    return ip_int

  }

  function int_to_ip(input)
  {
    str=""
    num=input
    for(i=3;i>=0;i--){
      octet = int (num / (256 ^ i))
      str= i==0?str octet:str octet "."
      num -= (octet * 256 ^ i)
    }
    return str
  }
  {
    ip=$1
    mask=$2
    range=$3

    validate_subnet(mask)

    cidr=to_cidr(mask)
    diff=32-cidr
    no_of_ip=2^diff

    ip_int=ip_to_int(ip)
    ip_mask=and(ip_int, (2^32 - 2^diff))

    ip_start=ip_mask
    ip_end=ip_mask+no_of_ip-1

    print "No of IPs\t"(no_of_ip-2)
    print "First IP\t" int_to_ip(ip_start+1)
    print "Last IP\t\t" int_to_ip(ip_end-1)
    print "Subnet\t\t" int_to_ip(ip_mask)
    print "Broadcast\t" int_to_ip(ip_end)

    if(range){
      print "\nIP address range -- START --\n"
      curr=ip_start
      i=0
      while(curr<=ip_end){
        printf int_to_ip(curr)"\t"
        if(j++%4 == 0) printf "\n"
        curr+=1
      }
      print "\nIP address range -- END --"
    }
  } '

Script Usage

[root@maximus] → ./ip_range 192.168.1.1 255.255.255.224
No of IPs       30
First IP        192.168.1.1
Last IP         192.168.1.30
Subnet          192.168.1.0
Broadcast       192.168.1.31


[root@maximus] → ./ip_range 192.168.1.1 255.255.255.224 1
No of IPs       30
First IP        192.168.1.1
Last IP         192.168.1.30
Subnet          192.168.1.0
Broadcast       192.168.1.31

IP address range -- START --

192.168.1.0     192.168.1.1     192.168.1.2     192.168.1.3
192.168.1.4     192.168.1.5     192.168.1.6     192.168.1.7
192.168.1.8     192.168.1.9     192.168.1.10    192.168.1.11
192.168.1.12    192.168.1.13    192.168.1.14    192.168.1.15
192.168.1.16    192.168.1.17    192.168.1.18    192.168.1.19
192.168.1.20    192.168.1.21    192.168.1.22    192.168.1.23
192.168.1.24    192.168.1.25    192.168.1.26    192.168.1.27
192.168.1.28    192.168.1.29    192.168.1.30    192.168.1.31

IP address range -- END --

[root@maximus] → ./ip_range 192.168.1.1 255.255.0.0
No of IPs       65534
First IP        192.168.0.1
Last IP         192.168.255.254
Subnet          192.168.0.0
Broadcast       192.168.255.255

Thursday, September 26, 2013

cURL HTTP Pipelining

One of my friend asked me if there was a tool to send pipelined http request from linux command line. Thanks to cURL libcurl, I developed a small tool to do the same. Have put in some basic validations and some restrictions like the maximum no of pipeline request is 32 etc

/* 
 * Ahamed 
 * Using cURL libcurl
 *
 * For sending pipelined http requests
 * Usage : ./send_pipelined_http <no of pipelined requests> <http://x.x.x.x>
 * Some basic validations added.
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>

static void usage();

#define ERR_LEN 512
#define MIN_URL_LEN 14
#define MAX_URL_LEN 32 
#define MIN_PIPELINE_REQ 1
#define MAX_PIPELINE_REQ 32
#define err(x, y) {printf("\nError: %s...\nExiting...\n", x); if(y)exit(0); usage();}

static unsigned int pipeline_req;
static char url[MAX_URL_LEN];
static char err_str[ERR_LEN];

static void handle_curl_error(CURLcode ret, char *func)
{
  if(ret != CURLE_OK){
    fprintf(stderr, "%s() failed: %s\n", func,
            curl_multi_strerror(ret));
  }
  return;
}

static void usage()
{
  printf("\nDeveloped by Ahamed using cURL API via libcurl\n");
  printf("Usage : ./send_pipelined_http <no of req> <http://x.x.x.x>\n");
  printf("        Pipeline Request - Min %d : Max : %d\n", 
                  MIN_PIPELINE_REQ, MAX_PIPELINE_REQ);
  printf("        Hostname not supported yet. Please provide IP address.\n");
  printf("        URL - Min Length %d : Max Length : %d\n\n", 
                  MIN_URL_LEN, MAX_URL_LEN);
  exit(0);
}

static void parse_args(int argc, char **argv)
{

  if(argc <= 2)
    err("Insufficient arguments", 0);

  if(!argv)
    err("Something unexpected happened", 1);

  pipeline_req = atol(argv[1]);
  if(pipeline_req > MAX_PIPELINE_REQ || pipeline_req < MIN_PIPELINE_REQ)
    err("Invalid Pipeline Request", 0);
  
  if(strlen(argv[2]) > MAX_URL_LEN || strlen(argv[2]) < MIN_URL_LEN)
    err("Invalid URL length", 0);

  strncpy(url, argv[2], MAX_URL_LEN);
  
  return;
}
 
int main(int argc, char **argv)
{

  int i=0;
  parse_args(argc, argv);

  CURLM *m_curl;
  CURLMcode res;

  m_curl = curl_multi_init();
  curl_multi_setopt(m_curl, CURLMOPT_PIPELINING, 1L);

  CURL *curl[MAX_PIPELINE_REQ];
  for(i=0; i<pipeline_req; i++){

    curl[i] = curl_easy_init();
    if(!curl[i])
      err("Something went wrong", 0);

    res = curl_easy_setopt(curl[i], CURLOPT_URL, url);
    handle_curl_error(res, "curl_easy_setopt");

    res = curl_easy_setopt(curl[i], CURLOPT_FOLLOWLOCATION, 1L);
    handle_curl_error(res, "curl_easy_setopt");

    res = curl_multi_add_handle(m_curl, curl[i]);
    handle_curl_error(res, "curl_multi_add_handle");
  }

  int ret = 1;
  do {
    res = curl_multi_perform(m_curl, &ret);
  } while(ret);

  handle_curl_error(res, (char*)__FUNCTION__);

  for(i=0; i<pipeline_req; i++){
    curl_multi_remove_handle(m_curl, curl[i]); 
    curl_easy_cleanup(curl[i]);
  }
  curl_multi_cleanup(m_curl);

  return 0;
}

root@Imperfecto_maximuS> gcc send_pipelined_http.c -lcurl -o send_pipelined_http
root@Imperfecto_maximuS> ./send_pipelined_http

Error: Insufficient arguments...
Exiting...

Developed by Ahamed(ahamed.en@gmail.com) using cURL API via libcurl
Usage : ./send_pipelined_http <no of req> <http://x.x.x.x>
        Pipeline Request - Min 1 : Max : 32
        Hostname not supported yet. Please provide IP address.
        URL - Min Length 14 : Max Length : 32

root@Imperfecto_maximuS>  ./send_pipelined_http 3 http://11.1.1.99
<html><body><h1>This is sample page</h1>\0<p>for testing created...</p></body></html>
<html><body><h1>This is sample page</h1>\0<p>for testing created...</p></body></html>
<html><body><h1>This is sample page</h1>\0<p>for testing created...</p></body></html>

Wednesday, May 1, 2013

To find if the nth bit is set

Following from the previous example, this is to find if the nth bit is set or not. Of course, ensure the second argument i.e. bit_pos is send correctly, have sufficient checks for that. Again, here the assumption is bit_pos starts from 0 to 31 for 32 bit integer.

#include "stdio.h"
#include "limits.h"

static unsigned short is_set(unsigned int x,
                        unsigned short bit_pos)
{
        return !!((1<<bit_pos) & x);
}


int main(int argc, char **argv)
{

        /* 0x1000 = 0000 0000 0000 0000 0001 0000 0000 0000
                                           |
                                          12th Bit
        */
        printf("0x%08x - %d \n", 0x1000, is_set(0x1000, 12));
        printf("0x%08x - %d \n", 0x1000, is_set(0x1000, 13));


        return 0;
}

[root@Imperfecto_1 ~]# gcc -g run.c && ./a.out
0x00001000 - 1
0x00001000 - 0

Finding MSB and LSB

How to find if the MSB or the LSB is set?

#include "stdio.h"
#include "limits.h"

/* This creates a 32 bit value with only MSB set
 * 1 << 31 times produces 10000000000000000000000000000000 i.e. 0x80000000
 * And then we AND it with x which will either yield 0x80000000 or 0x0
 * !!(0x80000000) = 1 and !!(0x0) = 0
 */
static unsigned short is_set_MSB(unsigned int x)
{
        return !!((1<<(sizeof(unsigned int) * CHAR_BIT - 1)) & x);
}

/* This is straight forward, x & 1 will either yield 1 or 0 directly.
 */
static unsigned short is_set_LSB(int x)
{
        return (x & 1);
}

int main(int argc, char **argv)
{

        printf("%08x - %d \n", 0xffffffff, is_set_LSB(0xffffffff));
        printf("%08x - %d \n", 0xfffffff0, is_set_LSB(0xfffffff0));
        printf("%08x - %d \n", 0xffffffff, is_set_MSB(0xffffffff));
        printf("%08x - %d \n", 0x0fffffff, is_set_MSB(0x0fffffff));

        return 0;
}

[root@Imperfecto_1 ~]# gcc -g run.c && ./a.out
ffffffff - 1
fffffff0 - 0
ffffffff - 1
0fffffff - 0

Swap without using a third variable

We know how to swap 2 values using a third temp variable. This is how you do it without using a third variable.

#include "stdio.h"

static void swap(int *x, int *y)
{
        *x = *x + *y;
        *y = *x - *y;
        *x = *x - *y;
        return;
}

static void swap_xor(int *x, int *y)
{
        *x = *x ^ *y;
        *y = *x ^ *y;
        *x = *x ^ *y;
        return;
}

int main(int argc, char **argv)
{

        int x = 10, y = 20;
        printf("1> %d %d\n", x, y);
        swap(&x, &y);
        printf("2> %d %d\n", x, y);
        swap_xor(&x, &y);
        printf("3> %d %d\n", x, y);

        return 0;
}

[root@Imperfecto_1 ~]# gcc -g run.c && ./a.out
1> 10 20
2> 20 10
3> 10 20

Print bits in an Integer

How to print bits in an integer? There are many ways to do this, I mean logically. I have 2 functions here, one recursive and the other one using a loop.

#include "stdio.h"
#include "stdlib.h"
#include "string.h"
#include "limits.h"

/* This function prints the bits in a recursive mode
 * It takes out the bits from right side i.e. 0, 1, 2
 * and prints, this being recursive will print the
 * output in reverse order which will be finally
 * the correct order
 */
static void recurse_bits(int x, int *size)
{
        int bit = x & 0x1;
        if((*size)--){
                recurse_bits(x>>=1, size);
                printf("%d ", bit);
        }
}

/* This function prints the bit by taking it from the left
 * side, i.e. 31, 30 etc and printing it right away
 */
static void print_bits(unsigned int x, int *size)
{
        unsigned short bits = *size;
        unsigned int mask = 0x1 << (bits-1);
        while(bits--){
                printf("%d ", !!(x & mask));
                x<<=1;
        }
        return;
}

int main(int argc, char **argv)
{

        int size = sizeof(unsigned int) * CHAR_BIT;
        int val = 9;

        print_bits(val, &size);
        printf("\n");

        recurse_bits(val, &size);
        printf("\n");

        return 0;
}

[root@Imperfecto_1 ~]# gcc -g run.c && ./a.out
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1

Monday, April 29, 2013

The lshw command

The lshw command lists the hardware information in your system. I came across this because I was having issues with wifi connectivity in Ubuntu 12.04. It just keeps disconnecting after a while and connects back. So, wanted to check the wifi card on and look for possible solutions.

root@Imperfecto_:~# lshw
imperfecto_               
    description: Desktop Computer
    product: Parrot ()
    vendor: GOOGLE
    version: 1.0
    serial: 123456789
    width: 64 bits
    capabilities: smbios-2.7 dmi-2.7 vsyscall32
    configuration: boot=normal chassis=desktop
  *-core
       description: Motherboard
       physical id: 0

and so on...

And I was interested in my wifi card, so I gave it some filters

root@Imperfecto_:~# lshw -C network
  *-network               
       description: Wireless interface
       product: AR9462 Wireless Network Adapter
       vendor: Atheros Communications Inc.
       physical id: 0
       bus info: pci@0000:01:00.0
       logical name: wlan0
       version: 01

and so on...