View source for OpenWRT notes

==Atheros AR81-Based Products==

===Hardware Comparison===

{| class="wikitable"
|-
! Vendor
! Product
! CPU
! Flash
! RAM
! USB
! OpenWRT info
! Comment
|-
| Linksys
| WRT160NL
| MIPS24Kc AR9132r2 400 MHz
| 8 MB
| 32 MB
| 1
| [http://wiki.openwrt.org/inbox/wrt160nl Wiki], [https://forum.openwrt.org/viewtopic.php?id=20298 Forum]
| 
|-
| TP-Link
| WR-841N(D) v5
| ?
| 4 MB
| 32 MB
| 0
| 
| USB on board but unpopulated, missing DC/DC converter
|-
| TP-Link
| WR-941N(D) v3
| MIPS24Kc AR9132r2 400 MHz
| 4 MB
| 32 MB
| 0
| 
| USB on board but unpopulated, missing DC/DC converter
|}

===Updating firmware with mtd===

The TP-Link devices and the Cisco WRT160NL have the firmware in the '''firmware''' mtd partition.

 mtd -r write openwrt.bin firmware

==Wireless Configuration==

===Install CRDA===

While basic wireless support works with just the wireless driver, you need the [http://linuxwireless.org/en/developers/Regulatory/CRDA regulatory database] to enable all channels that can be legally used in your country. So make sure to install the ''crda'' package.

==IPTables Configuration==

This section is specific to OpenWRT in that the kamikaze standard chains are explained. There must be some document in one of the OpenWRT wikis, but I couldn't easily find it.

In addition, I need EBTables in the picture as well, so a few comments on where you'd add layer 2 rules will be included.

===Call Graph and Custom Rules===

The OpenWRT standard rule set defines a few more or less default actions that you probably will want to keep: do not accept incoming connectins from the WAN interface (except for DHCP/bootp replies), NAT all outgoing traffic, and allow pretty much anything on the LAN interface. If you want to add your own rules to drop or allow additional things, there's a chain specifically for that. To understand which of these chains to add your rules to, look at this call graph. It is helpful to look at one of the EBTables tutorials, for example [http://ebtables.sourceforge.net/br_fw_ia/br_fw_ia.html ebtables/iptables interaction] or this [http://www.frozentux.net/iptables-tutorial/iptables-tutorial.html IPTables howto]. It contains a good overview of how packets traverse the various points.

====''mangle'' Table====
OpenWRT does not add any chains to the mangle table. If you want to add custom rules, you can add them to any of the standard chains (PREROUTING, INPUT, FORWARD, OUTPUT, POSTROUTING).

====''filter'' Table====
The filter table contains rules that determine whether packets are delivered to their intended destination, or blocked.
{| class="wikitable"
|-
! Call Graph
! Applies to packets
|-
| INPUT → input_rule
| Addressed to this host.
|-
| INPUT → input → zone_lan → input_lan
| Addressed to this host, received over the LAN interface.
|-
| INPUT → input → zone_wan → input_wan
| Addressed to this host, received over the WAN interface.
|-
| FORWARD → forwarding_rule
| Addressed to other hosts.
|-
| FORWARD → forward → zone_lan_forward → forwarding_lan
| Addressed to other hosts, received over the LAN interface.
|-
| FORWARD → forward → zone_wan_forward → forwarding_wan
| Addressed to other hosts, received over the WAN interface.
|-
| OUTPUT → output_rule
| Originating from this host.
|}

* The bridge calls the ''filter:FORWARD'' chain for packets traversing the bridge. If you want your wireless devices to be able to talk to the wired ones and vice versa, you need to add a rule to the ''forwarding_rule'' chain, since none of the default rules match those ethernet frames:
 iptables -A forwarding_lan -m physdev --physdev-is-bridged -j ACCEPT

====''nat'' Table====
The nat table contains rules that modify packets before they are routed or received, and modify them after they've been sent or routed. Typically, the MASQUERADE action is used.
{| class="wikitable"
|-
! Call Graph
! Applies to packets
|-
| PREROUTING → zone_wan_prerouting → prerouting_wan
| Just received on the WAN interface.
|-
| PREROUTING → zone_lan_prerouting → prerouting_lan
| Just received on the LAN interface.
|-
| PREROUTING → prerouting_rule
| Just received.
|-
| OUTPUT
| Being transmitted.
|-
| POSTROUTING → postrouting_rule
| About to be transmitted
|-
| POSTROUTING → zone_wan_nat
| About to be transmitted out the WAN interface.
|}

====''raw'' Table====
The raw table is used to mark packets that should not be tracked by the conntrack module.
{| class="wikitable"
|-
! Call Graph
! Applies to packets
|-
| PREROUTING → zone_wan_notrack
| Just received on the WAN interface.
|-
| PREROUTING → zone_lan_notrack
| Just received on the LAN interface.
|-
| OUTPUT
| Being transmitted.
|}

==Web Cam==

Using [http://sourceforge.net/apps/mediawiki/mjpg-streamer/ mjpeg-streamer] and one of the v4l video drivers, you can easily use the router as a surveilance device. For my Logitech camera, I needed:
* kmod-usb-video
* kmod-video-core
* kmod-video-uvc
* mjpg-streamer

The OpenWRT package for mjpg-streamer does not include the HTML files, so getting to see the images requires that you know the snapshot and streaming URLs. I downloaded the source tarball myself, and copied the www files into /tmp/www, and started ''mjpg-streamer'' like this:
 # mjpg_streamer -o "output_http.so -p 8080 -w /tmp/www"

To directly access the image, use /?action=snapshot for a single image, or /?action=stream for an M-JPEG streamed image.  ''mjpg-streamer'' also includes a Java applet to display M-JPEGs, and includes JavaScript to continously reload an image. See the source package for details

==Link List==

Building and installing
* [http://downloads.openwrt.org/snapshots/trunk/ar71xx/ OpenWRT snapshorts for ar71xx platform]
* [http://wiki.openwrt.org/doc/howto/buildroot buildroot instructions]
* [http://downloads.openwrt.org/docs/buildroot-documentation.html (Old) buildroot instructions]
* [http://forum.openwrt.org/viewtopic.php?id=15201 (Newer) trunk build instructions]

Configuration
* [https://forum.openwrt.org/viewtopic.php?id=20063 Configuring a UTMS stick]

Hardware and software alternatives
* [http://wiki.openwrt.org/toh/linksys/wrt160nl WRT160NL: Lots of details and pictures]
* [http://hardware.slashdot.org/comments.pl?sid=1144621&cid=27025553 Slashdot comment with Draft-N routers based on an Atheros solution]
* [http://bsdimp.blogspot.com/2008/12/dlink-dir-615-rev-c1.html Warners blog post about the device and possibly running FreeBSD on it]
* [http://www.nobbi.com/steck_s25.html Siemens S25 serial cable pinout]