Table of Contents

OpenWRT on Linksys WRT54G How-to

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Le routeur Linksys WRT54G

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OpenWRT

Installation en 3 étapes

Etape 1

Activation du boot_wait

  1. Il est impératif d'affecter à l'interface Internet du routeur une adresse IP. Le plus simple est encore d'utiliser une adresse quelconque en statique. Attention : il faut renseigner aussi le netmask et la passerelle (gateway).
  2. Il faut ensuite ouvrir la fenêtre Ping (menu Diagnostics) et entrer l'une après l'autre les lignes suivantes en cliquant sur le bouton Ping après chaque entrée :
;cp${IFS}*/*/nvram${IFS}/tmp/n
;*/n${IFS}set${IFS}boot_wait=on
;*/n${IFS}commit
;*/n${IFS}show>tmp/ping.log

Si tout c'est bien passé, l'écran de diagnostic se présente sous la forme suivante et l'option boot_wait apparait à on :

Etape 2

  1. Télécharger la version courante d'OpenWRT.
  2. Utiliser un client TFTP pour télécharger le firmware OpenWRT sur le routeur.
  3. Note Pour une découverte d'OpenWRT, il est prudent de choisir squashfs comme système de fichier. C'est la méthode standard, dixit la doc. officielle.
  4. Une fois le transfert effectué, laissez le routeur booter. Cela peut prendre quelques minutes. Pour suivre la progression du démarrage, surveillez la LED DMZ : elle est allumée durant le boot, éteinte dès que le système est “up”.

Etape 3

  1. Lorsque la phase de boot est terminée, vérifiez que tout c'est bien passé en ouvrant une session telnet sur l'IP 192.168.1.1 (IP utilisée par défaut) :
bash-2.05a$ telnet 192.168.1.1
Trying 192.168.1.1...
Connected to 192.168.1.1.
Escape character is '^]'.
 === IMPORTANT ============================
  Use 'passwd' to set your login password
  this will disable telnet and enable SSH
 ------------------------------------------
 
 
BusyBox v1.00 (2005.09.14-15:55+0000) Built-in shell (ash)
Enter 'help' for a list of built-in commands.
 
  _______                     ________        __
 |       |.-----.-----.-----.|  |  |  |.----.|  |_
 |   -   ||  _  |  -__|     ||  |  |  ||   _||   _|
 |_______||   __|_____|__|__||________||__|  |____|
          |__| W I R E L E S S   F R E E D O M
 WHITE RUSSIAN (RC3) -------------------------------
  * 2 oz Vodka   Mix the Vodka and Kahlua together
  * 1 oz Kahlua  over ice, then float the cream or
  * 1/2oz cream  milk on the top.
 ---------------------------------------------------
root@linksys:/#

Firstboot

root@linksys:/# mount
/dev/root on / type squashfs (ro)
none on /dev type devfs (rw)
none on /proc type proc (rw)
none on /tmp type tmpfs (rw,nosuid,nodev)
none on /dev/pts type devpts (rw)
root@linksys:/etc# mount
/dev/root on /rom type squashfs (ro)
none on /rom/dev type devfs (rw)
none on /rom/tmp type tmpfs (rw,nosuid,nodev)
none on /rom/dev/pts type devpts (rw)
/dev/mtdblock/4 on / type jffs2 (rw)
none on /proc type proc (rw)
none on /dev type devfs (rw)
none on /tmp type ramfs (rw)
root@linksys:/# df -h
Filesystem                Size      Used Available Use% Mounted on
/dev/root                 1.1M      1.1M         0 100% /rom
none                      7.0M      4.0k      7.0M   0% /rom/tmp
/dev/mtdblock/4           2.2M    360.0k      1.8M  16% /

Note La partition /rom est en lecture seule et de type squashfs. Comme nous le constaterons plus loin, de nombreux fichiers de configuration de base du répertoire /etc sont des liens vers des fichiers localisés sur cette partition. De ce fait, ils ne sont pas éditables et il est nécessaire d'effacer le lien et de créer un fichier dans le répertoire /etc pour manipuler les paramètres de certains programmes. 

root@linksys:/# dmesg
CPU revision is: 00029007
Primary instruction cache 8kB, physically tagged, 2-way, linesize 16 bytes.
Primary data cache 4kB, 2-way, linesize 16 bytes.
Linux version 2.4.30 (wbx@ux-2y01) (gcc version 3.4.4) #1 Wed Sep 14 17:49:26 CEST 2005
Setting the PFC value as 0x15
Determined physical RAM map:
 memory: 01000000 @ 00000000 (usable)
On node 0 totalpages: 4096
zone(0): 4096 pages.
zone(1): 0 pages.
zone(2): 0 pages.
Kernel command line: root=/dev/mtdblock2 rootfstype=squashfs,jffs2 init=/etc/preinit noinitrd console=ttyS0,115200
CPU: BCM4712 rev 2 at 216 MHz
Using 108.000 MHz high precision timer.
Calibrating delay loop... 215.44 BogoMIPS
Memory: 14296k/16384k available (1390k kernel code, 2088k reserved, 100k data, 80k init, 0k highmem)
Dentry cache hash table entries: 2048 (order: 2, 16384 bytes)
Inode cache hash table entries: 1024 (order: 1, 8192 bytes)
Mount cache hash table entries: 512 (order: 0, 4096 bytes)
Buffer cache hash table entries: 1024 (order: 0, 4096 bytes)
Page-cache hash table entries: 4096 (order: 2, 16384 bytes)
Checking for 'wait' instruction...  unavailable.
POSIX conformance testing by UNIFIX
PCI: Disabled
PCI: Fixing up bus 0
Linux NET4.0 for Linux 2.4
Based upon Swansea University Computer Society NET3.039
Initializing RT netlink socket
Starting kswapd
devfs: v1.12c (20020818) Richard Gooch (rgooch@atnf.csiro.au)
devfs: boot_options: 0x1
JFFS2 version 2.1. (C) 2001 Red Hat, Inc., designed by Axis Communications AB.
Squashfs 2.1-r2 (released 2004/12/15) (C) 2002-2004 Phillip Lougher
pty: 256 Unix98 ptys configured
Serial driver version 5.05c (2001-07-08) with MANY_PORTS SHARE_IRQ SERIAL_PCI enabled
ttyS00 at 0xb8000300 (irq = 3) is a 16550A
ttyS01 at 0xb8000400 (irq = 0) is a 16550A
Software Watchdog Timer: 0.05, timer margin: 60 sec
Physically mapped flash: Found an alias at 0x400000 for the chip at 0x0
Physically mapped flash: Found an alias at 0x800000 for the chip at 0x0
Physically mapped flash: Found an alias at 0xc00000 for the chip at 0x0
Physically mapped flash: Found an alias at 0x1000000 for the chip at 0x0
Physically mapped flash: Found an alias at 0x1400000 for the chip at 0x0
Physically mapped flash: Found an alias at 0x1800000 for the chip at 0x0
Physically mapped flash: Found an alias at 0x1c00000 for the chip at 0x0
cfi_cmdset_0001: Erase suspend on write enabled
0: offset=0x0,size=0x2000,blocks=8
1: offset=0x10000,size=0x10000,blocks=63
Using word write method
Flash device: 0x400000 at 0x1c000000
Creating 5 MTD partitions on "Physically mapped flash":
0x00000000-0x00040000 : "pmon"
0x00040000-0x003f0000 : "linux"
0x000ba4b0-0x001c0000 : "rootfs"
mtd: partition "rootfs" doesn't start on an erase block boundary -- force read-only
0x003f0000-0x00400000 : "nvram"
0x001c0000-0x003f0000 : "OpenWrt"
Initializing Cryptographic API
NET4: Linux TCP/IP 1.0 for NET4.0
IP Protocols: ICMP, UDP, TCP, IGMP
IP: routing cache hash table of 512 buckets, 4Kbytes
TCP: Hash tables configured (established 1024 bind 2048)
ip_conntrack version 2.1 (5953 buckets, 5953 max) - 320 bytes per conntrack
ip_tables: (C) 2000-2002 Netfilter core team
NET4: Unix domain sockets 1.0/SMP for Linux NET4.0.
NET4: Ethernet Bridge 008 for NET4.0
802.1Q VLAN Support v1.8 Ben Greear <greearb@candelatech.com>
All bugs added by David S. Miller <davem@redhat.com>
VFS: Mounted root (squashfs filesystem) readonly.
Mounted devfs on /dev
Freeing unused kernel memory: 80k freed
Algorithmics/MIPS FPU Emulator v1.5
diag boardtype: 00000708
jffs2.bbc: SIZE compression mode activated.
PCI: Setting latency timer of device 00:02.0 to 64
eth0: Broadcom BCM47xx 10/100 Mbps Ethernet Controller 3.90.23.0
PCI: Setting latency timer of device 00:01.0 to 64
eth1: Broadcom BCM4320 802.11 Wireless Controller 3.90.37.0
device eth0 entered promiscuous mode
vlan0: Setting MAC address to  00 14 bf 2f 48 d6.
VLAN (vlan0):  Underlying device (eth0) has same MAC, not checking promiscious mode.
vlan0: add 01:00:5e:00:00:01 mcast address to master interface
device eth1 entered promiscuous mode
eth1: attempt to add interface with same source address.
br0: port 2(eth1) entering learning state
br0: port 1(vlan0) entering learning state
br0: port 2(eth1) entering forwarding state
br0: topology change detected, propagating
br0: port 1(vlan0) entering forwarding state
br0: topology change detected, propagating
vlan1: Setting MAC address to  00 14 bf 2f 48 d7.
vlan1: add 01:00:5e:00:00:01 mcast address to master interface

Découverte du système

root@linksys:/# uname -a
Linux linksys 2.4.30 #1 Wed Sep 14 17:49:26 CEST 2005 mips unknown

un shell (ash) et les paquetages de base qui permettent d'activer la fonctionnalité AP WiFi : 

root@linksys:/# ipkg list
base-files - 2 - 
base-files-brcm - 1 - 
bridge - 1.0.6-1 - 
busybox - 1.00-2 - 
dnsmasq - 2.22-2 - 
dropbear - 0.45-3 - 
hotplug - 2 - 
ipkg - 0.99.149-2 - 
iptables - 1.3.1-1 - 
kernel - 2.4.30-brcm-2 - 
kmod-brcm-et - 2.4.30-brcm-2 - 
kmod-brcm-wl - 2.4.30-brcm-2 - 
kmod-diag - 2.4.30-brcm-2 - 
kmod-ppp - 2.4.30-brcm-2 - 
kmod-pppoe - 2.4.30-brcm-2 - 
kmod-wlcompat - 2.4.30-brcm-3 - 
libgcc - 3.4.4-2 - 
mtd - 2 - 
nvram - 1 - 
ppp - 2.4.3-6 - 
ppp-mod-pppoe - 2.4.3-6 - 
uclibc - 0.9.27-2 - 
wificonf - 4 - 
wireless-tools - 28.pre7-1 - 
zlib - 1.2.2-2 - 
Successfully terminated.

L'utilitaire ipkg est un gestionnaire de paquetages OpenWRT. L'option list utilisée ci-dessus, comme son nom l'indique, affiche la liste des paquetages installés en standard. Outre l'utilitaire ipkg, on notera la présence du filtre de paquets iptables et de dropbear, un serveur SSH2 pour OpenWRT.

Configuration Réseau

root@linksys:/etc/openvpn# ifconfig
br0       Link encap:Ethernet  HWaddr 00:14:BF:2F:48:D6  
          inet addr:192.168.1.1  Bcast:192.168.1.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:8372 errors:0 dropped:0 overruns:0 frame:0
          TX packets:7629 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:1546676 (1.4 MiB)  TX bytes:1439167 (1.3 MiB)
 
eth0      Link encap:Ethernet  HWaddr 00:14:BF:2F:48:D6  
          UP BROADCAST RUNNING PROMISC MULTICAST  MTU:1500  Metric:1
          RX packets:8372 errors:0 dropped:0 overruns:0 frame:0
          TX packets:7629 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:1730860 (1.6 MiB)  TX bytes:1469683 (1.4 MiB)
          Interrupt:5 Base address:0x2000 
 
eth1      Link encap:Ethernet  HWaddr 00:14:BF:2F:48:D6  
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:11480
          TX packets:375 errors:118 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:30381 (29.6 KiB)
          Interrupt:4 Base address:0x1000 
 
lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:9899 errors:0 dropped:0 overruns:0 frame:0
          TX packets:9899 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:963498 (940.9 KiB)  TX bytes:963498 (940.9 KiB)
 
vlan0     Link encap:Ethernet  HWaddr 00:14:BF:2F:48:D6  
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:8372 errors:0 dropped:0 overruns:0 frame:0
          TX packets:7629 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:1580164 (1.5 MiB)  TX bytes:1469683 (1.4 MiB)
 
vlan1     Link encap:Ethernet  HWaddr 00:14:BF:2F:48:D7  
          inet addr:213.223.10.10  Bcast:213.223.10.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

Gestion de la NVRAM

root@linksys:~# nvram show | grep wl0
wl0_net_mode=mixed
wl0_frameburst=off
wl0_wep_buf=
wl0_akm=
wl0_macmode1=disabled
wl0_infra=1
wl0_country_code=ALL
wl0_wme_sta_be=15 1023 3 0 0 off
wl0_ifname=eth1
wl0_wme_sta_bk=15 1023 7 0 0 off
wl0_mrate=0
wl0_mode=ap
wl0_ap_isolate=0
wl0_gmode=1
wl0_wme_no_ack=off
wl0_wep_last=
wl0_ssid=linksys
wl0_dtim=1
wl0id=0x4320
wl0_key1=
wl0_key2=
wl0_key3=
wl0_key4=
wl0_wme_ap_vi=7 15 1 6016 3008 off
wl0_closed=1
wl0_rate=0
wl0_plcphdr=long
wl0_macmode=disabled
wl0_radioids=BCM2050
wl0_wme_ap_vo=3 7 1 3264 1504 off
wl0gpio2=0
wl0_phytype=g
wl0gpio3=0
wl0_lazywds=1
wl0_afterburner=off
wl0_antdiv=-1
wl0_wpa_psk=
wl0_mac_list=
wl0_unit=0
wl0_net_reauth=36000
wl0_wds=
wl0_mac_deny=
wl0_auth=0
wl0_wme=off
wl0_radius_port=1812
wl0_radius_ipaddr=
wl0_wme_sta_vi=7 15 2 6016 3008 off
wl0_wme_sta_vo=3 7 2 3264 1504 off
wl0_maxassoc=128
wl0_phytypes=g
wl0_wep=disabled
wl0_frag=2346
wl0_country=ALL
wl0_rateset=default
wl0_wep_bit=64
wl0_passphrase=
wl0_rts=2347
wl0_wpa_gtk_rekey=3600
wl0_key=1
wl0_active_mac=
wl0_radio=0
wl0_bcn=100
wl0_hwaddr=00:14:BF:2F:48:D8
wl0_wep_gen=
wl0_gmode_protection=off
wl0_maclist=
wl0_radius_key=
wl0_wme_ap_be=15 63 3 0 0 off
wl0_corerev=7
wl0_channel=11
wl0_wds_timeout=1
wl0_wme_ap_bk=15 1023 7 0 0 off
wl0_auth_mode=none
wl0_crypto=tkip

Pour modifier un paramètre : 

: Exemple : désactiver le wifi
# nvram set wl0_radio=0
: "flasher" la nouvelle valeur
# nvram commit
: Et l'inévitable reboot pour la prise en compte 
: du nouveau paramètre
# reboot

Adieu telnet, bonjour SSH

Installation de paquetages

root@linksys:~# ipkg install libpcap_0.8.3-1_mipsel.ipk 
Installing libpcap (0.8.3-1) to root...
Configuring libpcap
Successfully terminated.
root@linksys:~# ipkg install tcpdump_3.8.3-1_mipsel.ipk 
Installing tcpdump (3.8.3-1) to root...
Configuring tcpdump
Successfully terminated.
root@linksys:~# ls -l /etc
lrwxrwxrwx    1 root     root           15 Jan  1 02:15 banner -> /rom/etc/banner
lrwxrwxrwx    1 root     root           21 Jan  1 02:15 dnsmasq.conf -> /rom/etc/dnsmasq.conf
drwxr-xr-x    1 root     root            0 Jan  1 00:04 dropbear
lrwxrwxrwx    1 root     root           22 Jan  1 02:15 firewall.user -> /rom/etc/firewall.user
lrwxrwxrwx    1 root     root           21 Jan  1 02:15 functions.sh -> /rom/etc/functions.sh
lrwxrwxrwx    1 root     root           14 Jan  1 02:15 group -> /rom/etc/group
lrwxrwxrwx    1 root     root           14 Jan  1 02:15 hosts -> /rom/etc/hosts
drwxr-xr-x    1 root     root            0 Jan  1 02:15 init.d
lrwxrwxrwx    1 root     root           16 Jan  1 02:15 inittab -> /rom/etc/inittab
-rw-r-----    1 root     root          167 Jan  1 01:36 ipkg.conf
lrwxrwxrwx    1 root     root           16 Jan  1 02:15 modules -> /rom/etc/modules
drwxr-xr-x    1 root     root            0 Jan  1 02:15 modules.d
lrwxrwxrwx    1 root     root           24 Jan  1 02:15 nvram.overrides -> /rom/etc/nvram.overrides
-rw-r-----    1 root     root           99 Jan  1 00:01 passwd
-rw-------    1 root     root           74 Aug 13  2005 passwd-
drwxr-xr-x    1 root     root            0 Jan  1 02:15 ppp
lrwxrwxrwx    1 root     root           16 Jan  1 02:15 preinit -> /rom/etc/preinit
lrwxrwxrwx    1 root     root           16 Jan  1 02:15 profile -> /rom/etc/profile
lrwxrwxrwx    1 root     root           18 Jan  1 02:15 protocols -> /rom/etc/protocols
lrwxrwxrwx    1 root     root           20 Jan  1 02:15 resolv.conf -> /rom/etc/resolv.conf
lrwxrwxrwx    1 root     root           15 Jan  1 02:15 shells -> /rom/etc/shells
lrwxrwxrwx    1 root     root           16 Jan  1 02:15 sysconf -> /rom/etc/sysconf
lrwxrwxrwx    1 root     root           20 Jan  1 02:15 sysctl.conf -> /rom/etc/sysctl.conf

Or cette partition de type squashfs est en lecture seule (les plus perspicaces auront deviné que ROM signifie Read Only Memory) : 

root@linksys:~# mount
/dev/root on /rom type squashfs (ro)
none on /rom/dev type devfs (rw)
/dev/mtdblock/4 on / type jffs2 (rw)
none on /proc type proc (rw)
none on /dev type devfs (rw)
none on /tmp type tmpfs (rw,nosuid,nodev)
none on /dev/pts type devpts (rw)
rm /etc/ipkg.conf
cp /rom/etc/ipkg.conf /etc/ipkg.conf

Le fichier est alors créé sur une partition en lecture/écriture et peut être modifié sans problème.

Installation d'une interface graphique

Filtrage réseau

root@point-central:~# more /etc/init.d/S45firewall 
#!/bin/sh
 
## Please make changes in /etc/firewall.user
${FAILSAFE:+exit}
 
. /etc/functions.sh
WAN=$(nvram get wan_ifname)
LAN=$(nvram get lan_ifname)
 
## CLEAR TABLES
for T in filter nat mangle; do
  iptables -t $T -F
  iptables -t $T -X
done
 
iptables -N input_rule
iptables -N output_rule
iptables -N forwarding_rule
 
iptables -t nat -N prerouting_rule
iptables -t nat -N postrouting_rule
 
### INPUT
###  (connections with the router as destination)
 
  # base case
  iptables -P INPUT DROP
  iptables -A INPUT -m state --state INVALID -j DROP
  iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
  iptables -A INPUT -p tcp --tcp-flags SYN SYN --tcp-option \! 2 -j  DROP
 
  #
  # insert accept rule or to jump to new accept-check table here
  #
  iptables -A INPUT -j input_rule
 
  # allow
  iptables -A INPUT -i \! $WAN  -j ACCEPT       # allow from lan/wifi interfaces 
  iptables -A INPUT -p icmp     -j ACCEPT       # allow ICMP
  iptables -A INPUT -p gre      -j ACCEPT       # allow GRE
 
  # reject (what to do with anything not allowed earlier)
  iptables -A INPUT -p tcp -j REJECT --reject-with tcp-reset
  iptables -A INPUT -j REJECT --reject-with icmp-port-unreachable
 
### OUTPUT
### (connections with the router as source)
 
  # base case
  iptables -P OUTPUT DROP
  iptables -A OUTPUT -m state --state INVALID -j DROP
  iptables -A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
 
  #
  # insert accept rule or to jump to new accept-check table here
  #
  iptables -A OUTPUT -j output_rule
 
  # allow
  iptables -A OUTPUT -j ACCEPT          #allow everything out
 
  # reject (what to do with anything not allowed earlier)
  iptables -A OUTPUT -p tcp -j REJECT --reject-with tcp-reset
  iptables -A OUTPUT -j REJECT --reject-with icmp-port-unreachable
 
### FORWARDING
### (connections routed through the router)
 
  # base case
  iptables -P FORWARD DROP 
  iptables -A FORWARD -m state --state INVALID -j DROP
  iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
  iptables -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
 
  #
  # insert accept rule or to jump to new accept-check table here
  #
  iptables -A FORWARD -j forwarding_rule
 
  # allow
  iptables -A FORWARD -i br0 -o br0 -j ACCEPT
  iptables -A FORWARD -i $LAN -o $WAN -j ACCEPT
 
  # reject (what to do with anything not allowed earlier)
  # uses the default -P DROP
 
### MASQ
  iptables -t nat -A PREROUTING -j prerouting_rule
  iptables -t nat -A POSTROUTING -j postrouting_rule
  iptables -t nat -A POSTROUTING -o $WAN -j MASQUERADE
 
## USER RULES
[ -f /etc/firewall.user ] && . /etc/firewall.user

En cas de problème...

En guise de conclusion