Sacando partido a 'La Fonera'
Configuración: Repetidor / Punto de Acceso / Tarjeta inalámbrica (script bridge)

Este script bridge debe ser copiado al directorio /etc de la fonera, hacerlo ejecutable con chmod +x /etc/bridge e intentar lanzarlo a mano para ver si todo va bien. Si todo funciona como se esperaba entonces la fonera repetirá la señal de un Punto de acceso cercano. Adicionalmente a este script /etc/bridge, existe unos ficheros de configuración adicionales que deberías de descargar y ajustar a tus necesiddades. Estos scripts son /etc/dnsmasq_repeater-br0.conf, /etc/dnsmasq_repeater-ath0.conf, /etc/dnsmasq_repeater-eth0.conf y por último el más importante /etc/config/bridge.conf el cual controla toda la parametrización sobre que red se quiere repetir, si se desea hacer broadcast en abierto o con wpa2, etc.

Si tras ejecutar a mano el script /etc/bridge todo funciona como uno espera, entonces se podría añadir al arranque automático de tu fonera copiando o enlazando el ejecutable así: ln /etc/bridge /etc/init.d/S98ponte2 y listo. NOTA: durante las pruebas no se recomienda hacer esto, pues en caso de no enlazar con ningún punto de acceso, no podremos entrar a nuestra fonera con facilidad.
Si esto ocurriese, podríamos intentar entrar poniéndonos una ip fija como por ejemplo 169.254.255.2 y máscara 255.255.255.0 (o úna máscara de tipo B si se prefiere) y tratar de entrar a la IP que la fonera siempre mantiene en la 169.254.255.1.

Si se pretende enlazar a un punto de acceso con autenticación WPA-PSK, también debes de descargar e instalar los paquetes wpa_supplicant y libopenssl.
(La instalación es tan simple como hacer un 'ipkg install wpa_supplicant.ipk' y un 'ipkg install libopenssl.ipk')

La descarga de todos estos ficheros de configuración junto con el script /etc/bridge puedes realizarla desde esta página: aquí

download /etc/bridge

#!/bin/sh
# /etc/bridge
#****************************************************************************
#.-  20070320 version
#.-  Script modified by Victor Escudero <Linux.RuleThemAll(at)yahoo(dot)es> ,
#.-  based on the excellent work of Antonio Anselmi (http://www.blogin.it)
#.-
#****************************************************************************

#----------------------------------------------------------------------------
# setup_env.  Function that setups environment
setup_env () {
# Set the default values of all environment variables here
logDir=/var/log
tmpDir=/tmp
acl_list=/etc/acl_list.conf
myself=`basename $0`
logFile=$logDir/$myself.log
datevar=$(date)
IWCONFIG=/usr/sbin/iwconfig
IFCONFIG=/sbin/ifconfig
WLANCONFIG=/usr/sbin/wlanconfig
IWPRIV=/usr/sbin/iwpriv
NETFILTER=/usr/sbin/iptables
ROUTE=/sbin/route
#.-
showresults=0
#.-
rm -f /tmp/results
#
echo "$datevar: start" >> $logFile
if [ -f /etc/config/bridge.conf ]; then
        . /etc/config/bridge.conf
else
        echo "/etc/config/bridge.conf not found"
        echo "/etc/config/bridge.conf not found" >> $logFile
        echo "stop and exit" >> $logFile
        exit 1
fi

# ip_forward is enabled by default in fonera configuration
# echo 1 > /proc/sys/net/ipv4/ip_forward

# stop daemons
local web=httpd
local cron=crond
local dns=dnsmasq
#.-
local wpasupplicant=wpa_supplicant
local hostap=hostapd
#.-

# If you are not willing to use the web interface, you might want to uncomment this lines
#if [ ! -z "$( pidof $web )" ]; then
#  kill $(pidof $web) > /dev/null
#fi

if [ ! -z "$( pidof $cron )" ]; then
  kill $(pidof $cron) > /dev/null
fi
if [ ! -z "$( pidof $dns )" ]; then
  kill $(pidof $dns) >> /dev/null
fi
killall -9 udhcpc > /dev/null

#.- If you've run this script before maybe wpa_supplicant could be running
if [ ! -z "$( pidof $wpasupplicant )" ]; then
  kill $(pidof $wpasupplicant) >> /dev/null
fi

#.- Maybe hostapd is running because of Whisher signal
if [ ! -z "$( pidof $hostap )" ]; then
  kill $(pidof $hostap) >> /dev/null
fi

# flush_netfilter tables
$NETFILTER -F
$NETFILTER -P INPUT ACCEPT
$NETFILTER -P OUTPUT ACCEPT
$NETFILTER -P FORWARD ACCEPT
$NETFILTER -t nat -F
echo "netfilter tables flushed" >> $logFile
} # setup_env


#-------------------------------------------------------------------------------
# hardening Function that sets some TCP/IP parameters
hardening () {
if [ $khard == 1 ]; then
  # Disable tcp_sack support
  echo "0" > /proc/sys/net/ipv4/tcp_sack
  # Disable TCP window_scaling
  echo "0" > /proc/sys/net/ipv4/tcp_window_scaling
  # Disable source routing
  echo "0" > /proc/sys/net/ipv4/conf/all/accept_source_route
  echo "0" > /proc/sys/net/ipv4/conf/lo/accept_source_route
  echo "0" > /proc/sys/net/ipv4/conf/eth0/accept_source_route
  echo "0" > /proc/sys/net/ipv4/conf/ath0/accept_source_route
  echo "0" > /proc/sys/net/ipv4/conf/ath1/accept_source_route
  echo "0" > /proc/sys/net/ipv4/conf/default/accept_source_route
  # Enable TCP SYN Cookie potection
  echo "1" > /proc/sys/net/ipv4/tcp_syncookies
  # No ICMP Redirect
  echo "0" > /proc/sys/net/ipv4/conf/all/accept_redirects
  echo "0" > /proc/sys/net/ipv4/conf/lo/accept_redirects
  echo "0" > /proc/sys/net/ipv4/conf/eth0/accept_redirects
  echo "0" > /proc/sys/net/ipv4/conf/ath0/accept_redirects
  echo "0" > /proc/sys/net/ipv4/conf/ath1/accept_redirects
  echo "0" > /proc/sys/net/ipv4/conf/default/accept_redirects
  # Enable IP spoofing protection
  echo "1" > /proc/sys/net/ipv4/conf/all/rp_filter
  echo "1" > /proc/sys/net/ipv4/conf/lo/rp_filter
  echo "1" > /proc/sys/net/ipv4/conf/eth0/rp_filter
  echo "1" > /proc/sys/net/ipv4/conf/ath0/rp_filter
  echo "1" > /proc/sys/net/ipv4/conf/ath1/rp_filter
  echo "1" > /proc/sys/net/ipv4/conf/default/rp_filter
  echo "fonera hardened" >> $logFile
fi

if [ $klog == 1 ]; then
  echo "1" > /proc/sys/net/ipv4/conf/all/log_martians = 1
  echo "1" > /proc/sys/net/ipv4/conf/lo/log_martians = 1
  echo "1" > /proc/sys/net/ipv4/conf/eth0/log_martians = 1
  echo "1" > /proc/sys/net/ipv4/conf/ath0/log_martians = 1
  echo "1" > /proc/sys/net/ipv4/conf/ath1/log_martians = 1
  echo "1" > /proc/sys/net/ipv4/conf/default/log_martians = 1
  echo "logging malicious packests activated" >> $logFile
fi
} # hardening


#-------------------------------------------------------------------------------
create_AP () {
# bring up first (!) VAP ath0 as Access Point
$WLANCONFIG ath0 destroy
$WLANCONFIG ath0 create wlandev wifi0 wlanmode ap
echo "created VAP ath0 as AP" >> $logFile
} # create_AP


#-------------------------------------------------------------------------------
create_STA () {
# bring up VAP ath1 as station managed (no hardware beacon timers)
$WLANCONFIG ath1 destroy
$WLANCONFIG ath1 create wlandev wifi0 wlanmode sta nosbeacon
echo "created VAP ath1 as station" >> $logFile
} # create_STA

#-------------------------------------------------------------------------------
create_MONITOR () {
# bring up VAP ath2 in monitor mode
  $IFCONFIG ath2 >/dev/null 2>&1     # Test if ath2 exist from a previous run
if [ $? == 0 ]; then
  $WLANCONFIG ath2 destroy
fi
  case $kheaders in
    11) # Only 802.11 headers
    echo '801' > /proc/sys/net/ath0/dev_type
    ;;
    2) # Prism2 headers
    echo '802' > /proc/sys/net/ath0/dev_type
    ;;
    3) # Radiotap headers
    echo '803' > /proc/sys/net/ath0/dev_type
    ;;
    4) # Atheros Descriptors
    echo '804' > /proc/sys/net/ath0/dev_type
    ;;
  esac
  $WLANCONFIG ath2 create wlandev wifi0 wlanmode monitor
  $IFCONFIG ath2 up
  echo "created VAP ath2 as monitor" >> $logFile
} # create_MONITOR

#-------------------------------------------------------------------------------
# catchExternalESSID. Function that sets our ESSID as relay of the external AP
catchExternalESSID() {
  $IWCONFIG ath1 | grep ESSID > /tmp/bridge_tmp
  INI=32
  FIN=$(cat /tmp/bridge_tmp | wc -c)
  : $((FIN = $FIN - 4))
  SSID_ath0=$(cut /tmp/bridge_tmp -c $INI-$FIN)
  SSID_ath0="relay_$SSID_ath0"
} # catchExternalESSID

#-------------------------------------------------------------------------------
# setup_wpa_ath0. Function that sets wpa/wpa2 encryption on ath0 (our AP)
setup_wpa_ath0 () {

if [ ! -z "$( pidof hostapd )" ]; then
  kill $(pidof hostapd) >> /dev/null
fi

cat > /tmp/hostapd_repeater.conf <<EOF
interface=ath0
driver=madwifi
debug=0
eapol_key_index_workaround=1
wpa=$wpamode
wpa_pairwise=$wpapairwise
wpa_passphrase=$wpapassphrase
wpa_group_rekey=3600
EOF

hostapd -B /tmp/hostapd_repeater.conf
}

#-------------------------------------------------------------------------------
# setup_AP. Function that setup ath0 as an Access Point
setup_AP () {

# wireless mode
case $wMode in
  0) $IWPRIV ath0 mode auto ;;
  1) $IWPRIV ath0 mode 11a  ;;
  2) $IWPRIV ath0 mode 11b  ;;
  3) $IWPRIV ath0 mode 11g  ;;
  4) $IWPRIV ath0 mode fh   ;;
  5) $IWPRIV ath0 mode 11adt/111at ;;
  6) $IWPRIV ath0 mode 11gdt/11gt  ;;
  7) $IWPRIV ath0 mode 11ast ;;
esac

if [ $kssid == 1 ]; then
  catchExternalESSID
fi

$IWCONFIG ath0 essid "$SSID_ath0"

echo "setting AP essid to ath0: $SSID_ath0"
# WEP key
case $kwep in
  1) #WEP key as ASCII string
     $IWCONFIG ath0 key s:$WepKeyAscii_ath0
     echo "ath0 ascii WEP key: "$WepKeyAscii_ath0 >> $logFile
  ;;
  2) #targeted external AP via WEP key in hex
     $IWCONFIG ath0 key $WepKeyHex_ath0
     echo "ath0 hex WEP key: "$WepKeyHex_ath0 >> $logFile
  ;;
esac

if [ $ath0_authmode == 2 ]; then
  $IWPRIV ath0 authmode $ath0_authmode
fi

if [ $kwpa == 1 ]; then
  setup_wpa_ath0
fi

# enable 802.11 SSID broadcasting on ath0
$IWPRIV ath0 hide_ssid 0
if [ $hideSSID == 1 ]; then
  $IWPRIV ath0 hide_ssid 1
fi

# ACL management
case $aclMode in
  1) # only allow MACSs in the ACL list
  $IWPRIV ath0 maccmd 3
  $IWPRIV ath0 maccmd 1
  for i in $(cat $acl_list); do
    $IWPRIV ath0 addmac $i
  done
  ;;
  2) # only deny MACs in the ACL list
  $IWPRIV ath0 maccmd 3
  $IWPRIV ath0 maccmd 2
  for i in $(cat $acl_list); do
    $IWPRIV ath0 addmac $i
  done
  ;;
  *) # no ACL checking is performed
  $IWPRIV ath0 maccmd 0
  ;;
esac

} # setup_AP

#-------------------------------------------------------------------------------
# setup_STA. Function that setup ath1 as repeater
setup_STA () {

  case $ath1_mode in

  2) #targeted external AP by SSID
  $IWCONFIG ath1 mode managed essid $TargetSsid
  echo "ath1 via SSID: "$TargetSsid >> $logFile
  ;;

  3) #targeted external AP by MAC
  $IWCONFIG ath1 mode managed ap $TargetMac
  echo "ath1 via MAC: "$TargetMac >> $logFile
  ;;

  4) #targeted external AP via WPA-PSK
  $IWCONFIG ath1 mode managed essid $TargetWpa
#.-  $IFCONFIG ath1 $IP_ath1 netmask $MASK_ath1 up
  $IFCONFIG ath1 up
  #.- You must let wpa_supplicant do its job in the background
  wpa_supplicant -iath1 -c/etc/wpa_supplicant.conf -B
  echo "ath1 interface via WPA PSK" >> $logFile
  ;;

  5) #targeted external AP via WEP (ascii key)
    if [ $WepKeyAscii_ath1 ]; then
      $IWCONFIG ath1 key "s:$WepKeyAscii_ath1"
      else
      echo "error: ascii WEP key not configured" >> $logFile
      exit 1
    fi
  ;;
  6) #targeted external AP via WEP (hex key)
    if [ $WepKeyHex_ath1 ]; then
      $IWCONFIG ath1 key "$WepKeyHex_ath1"
      else
      echo "error: WEP hex key not configured" >> $logFile
      exit 1
    fi
  ;;

esac

if [ $ath1_mode == 5 ] || [ $ath1_mode == 6 ] ; then
  # We look for target ssid or AP
  if [ $TargetWepSsid ]; then
    $IWCONFIG ath1 mode managed essid $TargetWepSsid
    else
    if [ $TargetWepMac ]; then
      $IWCONFIG ath1 mode managed ap $TargetWepMac
      else
      echo "No target AP for WEP, we will scan the strongest AP" >> $logFile
    fi
  fi
  if [ $ath1_authmode == 2 ]; then
        $IWPRIV ath1 authmode $ath1_authmode
  fi
  echo "ath1 interface via WEP" >> $logFile
fi

# IP config for ath1
if [ $ath1_mode == 1 ] || [ $ath1_dhcp == 1 ] ; then
  # Dyanamic IP configuration
  echo "waiting 5 seconds to let dhcp gathers info from the AP through ath1 ..."
  /sbin/udhcpc -b -i ath1 >> $logFile
  sleep 5
  $IWCONFIG ath1 | grep ESSID | awk '"external AP " {print $4}' >> $logFile
  echo "ath1 interface via external dhcp" >> $logFile
  else
  # static IP configuration
  $IFCONFIG ath1 $IP_ath1 netmask $MASK_ath1 up
  $ROUTE del default
  $ROUTE add default gw $DFGW
  echo "nameserver " $NAMESERVER1  > /etc/resolv.conf
  echo "nameserver " $NAMESERVER2 >> /etc/resolv.conf
  echo "nameserver " $NAMESERVER3 >> /etc/resolv.conf
fi
#
$NETFILTER -t nat -A POSTROUTING -o ath1 -j MASQUERADE
} # setup_STA


#-------------------------------------------------------------------------------
# setup_2ifaces. Function that sets up 2 IP interface (eth0 and ath0)
setup_2ifaces () {

  $IFCONFIG br0 >/dev/null 2>&1     # Test if br0 exist from a previous run
  if [ $? == 0 ]; then
        $IFCONFIG br0 down
        brctl delbr br0
  fi
  # static eth0 IP configuration
  $IFCONFIG eth0 $IP_eth0 netmask $MASK_eth0 up
  echo "eth0 interface: "$IP_eth0/$MASK_eth0 >> $logFile

  # static ath0 IP configuration
  $IFCONFIG ath0 $IP_ath0 netmask $MASK_ath0 up
  echo "ath0 interface: "$IP_ath0/$MASK_ath0 >> $logFile
} # setup_2ifaces


#-------------------------------------------------------------------------------
# setup_bridge. Function that setup a bridge between eth0 and ath0
setup_bridge () {
  $IFCONFIG br0 >/dev/null 2>&1    # Test if br0 exist from a previous running
  if [ $? == 0 ]; then
        $IFCONFIG br0 down
        brctl delbr br0
  fi
  $IFCONFIG eth0 0.0.0.0 up
  $IFCONFIG ath0 0.0.0.0 up
  # bring up a bridge called br0
  brctl addbr br0
  brctl addif br0 eth0
  brctl addif br0 ath0
  # static br0 IP configuration
  $IFCONFIG br0 $IP_br0 netmask $MASK_br0 up
  echo "br0 interface: "$IP_br0/$MASK_br0 >> $logFile
} # setup bridge


#-------------------------------------------------------------------------------
# std_routing. Standard routing
std_routing () {
# forwarding between the subnets
echo 1 > /proc/sys/net/ipv4/ip_forward
$NETFILTER -t nat -A POSTROUTING -o ath1 -j MASQUERADE

# support for p2p
if [ $btorrent == 1 ]; then
  BTports="6890 6891 6892 6893 6894 6895 6896 6897 6898 6899"
  for pt in $BTports; do
    $NETFILTER -t nat -A PREROUTING -i ath1 -p tcp --dport $pt -j DNAT --to $IP_client_btorrent:$pt
  done
fi
if [ $xmule == 1 ]; then
  echo "32752" > /proc/sys/net/ipv4/netfilter/ip_conntrack_max
  $NETFILTER -t nat -A PREROUTING -i ath1 -p tcp --dport 4662 -j DNAT --to $IP_client_xmule:4662
  $NETFILTER -t nat -A PREROUTING -i ath1 -p udp --dport 4672 -j DNAT --to $IP_client_xmule:4672
fi
} # std_routing


#-------------------------------------------------------------------------------
# main
#-------------------------------------------------------------------------------
clear
# learn environment
setup_env

# WIRELESS setup:
# create ath0 as Access Point
   create_AP
   setup_AP
if ! [ $only_AP == 1 ]; then
  # create ath1 as Station
  create_STA
  setup_STA
fi
setup_AP        # Maybe in the first run we did not knew the right essid

# IP (ath0 and eth0) setup:
# two separated interfaces (ath0+eth0) or a bridge (br0)
if [ $bridge_mode == 1 ]; then
  setup_bridge
  $NETFILTER -t nat -A POSTROUTING -o br0 -j MASQUERADE
else
  setup_2ifaces
  $NETFILTER -t nat -A POSTROUTING -o eth0 -j MASQUERADE
  $NETFILTER -t nat -A POSTROUTING -o ath0 -j MASQUERADE
fi

# create ath2 as monitor, but only after the other interfaces are
# up and if the variable ModeMonitor=1

if [ $modeMonitor == 1 ]; then
  create_MONITOR
fi

# hardening some TCP/IP parameters
hardening
# and setting some netfilter rules
std_routing

# start DHCP
if [ $kdhcp == 1 ]; then
  # /usr/sbin/dnsmasq -a $IP_dhcp
  if [ $bridge_mode == 1 ]; then
     /usr/sbin/dnsmasq --interface=br0 -C /etc/dnsmasq_repeater-br0.conf
  else
     /usr/sbin/dnsmasq --interface=eth0 -C /etc/dnsmasq_repeater-eth0.conf
     /usr/sbin/dnsmasq --interface=ath0 -C /etc/dnsmasq_repeater-ath0.conf
  fi
fi

# so, show results
$IWCONFIG > /tmp/results
$IFCONFIG >> /tmp/results
clear
if [ $showresults == 1 ]; then
        /bin/more /tmp/results
fi
exit 0
# Enjoy your Fonera !!

Configuración: leer la página sobre la configuración de /etc/config/bridge.conf y los scripts para dnsmasq aquí