openwrt

OpenWRT on a “locked down” TP-Link WR1043ND v3 wireless router

Published by on July 7, 2016 | 4 Responses

It turns out that the brouhaha over certain manufacturers’ reactions to the FCC ruling to prevent 3rd-party software from taking wireless routers out of their approved emissions range is valid. I bought a TP-Link WR1043ND v3 router to compliment the existing v2 router I bought several years ago. I have a point-to-point setup with OpenWRT on both ends. It turns out that TP Link has indeed started locking down their routers to prevent third-party firmware installations. (I had hoped that buying the older V3 would get around this, but apparently not so.) Setting up OpenWRT is now a little bit (but not much) more difficult than it was on these routers.

Fortunately, it seems that TP-Link has only locked down the web interface to prevent third-party firmware installation and downgrading factory firmware. You’ll get an error 18005 if you try this. TFTP still works. In the end, the steps to flash were the following, based on the information at the OpenWRT wiki. You’ll need a Linux machine with DNSMasq installed.

  1. Download the factory OpenWRT trunk image for the WR1043ND v3. Currently as of July 7, 2016: https://downloads.openwrt.org/snapshots/trunk/ar71xx/generic/openwrt-ar71xx-generic-tl-wr1043nd-v3-squashfs-factory.bin
  2. Rename the OpenWRT file to wr1043v3_tp_recovery.bin
  3. Move the file to /tmp
  4. Set your NIC’s address to 192.168.0.66 and hook up the router, but don’t power it on yet.
  5. Use DNSMasq as a quick tftp server with the following command: dnsmasq -d –enable-tftp –tftp-root=/tmp
  6. In another terminal window, use tcpdump to view traffic on your NIC.
  7. Hold down the router’s reset button and power it on.
  8. Hold the reset button until tcpdump shows the file transfer.
  9. Wait 5 minutes

The OpenWRT build doesn’t have the web GUI installed. Fortunately, that’s easy to fix:

  1. Use SSH to log into root@192.168.1.1
  2. Hook the router’s WAN port to a LAN switch (to give it Internet access)
  3. Run opkg update && opkg install luci on the router
  4. Run reboot on the router
  5. Visit 192.168.1.1 and enjoy

Goodbye, Old Router

Published by on July 18, 2015 | Leave a response

I retired my old router a few days ago. (I might’ve cried.) For the past few years my router has been a computer powered by a 900MHz Celeron CPU (512MB RAM, 2x gigabit PCI-X NIC, 2x 100MBit NIC). And it worked great. It used a Compact Flash card as its hard drive via a CF->IDE adapter and could push 300MBit/s across any two interfaces; it used CentOS 6 and packages like dnsmasq to provide various services on the network: dhcp/dhcp6, dns, ntp, etc. I had built the router as a project to learn about Linux and networking, and I had chosen that old computer because it had a serial port for a 28.8k modem.

The problem was, it used a lot of electricity for what it did; my Kill-A-Watt meter reported about 45W idle and 65W when under full load, compared to 5W-10W for modern routers. So I found a Cisco-Linksys WRT160Nv3 router for $5 at a thrift store and slapped OpenWRT on it.

The WRT160Nv3 is at least mostly supported by OpenWRT; I built my own custom image for it as I did for the RouterBoard RB411 awhile back. I’m not confident that the BCM4716B0 Wireless N radio is fully supported; there are several drivers for Broadcom chipsets and since I only needed G speeds (for a guest network), I selected the open-source b43 wireless firmware instead of the proprietary Broadcom wireless driver, out of principle. The Broadcom driver likely supports N speeds. There is a third driver (brcm80211) but I didn’t test it; you might have more luck than I did. You can switch between all of these drivers in the OpenWRT menuconfig system.

I also added some goodies to the image: iftop, tcpdump, and LuCI, the OpenWRT web UI, because it has totally spoiled me rotten. Adding them to the image instead of as modules saves space, which is important because this router has only 4MB flash. I shaved off space by disabling kernel debug symbols and removing a few other things, including opkg and ppp support.

Flashing was a minor challenge because the bootloader’s handling of TFTP flashing is broken. (This makes bricking a little easier, so be careful!) If flashing the OpenWRT from the stock web UI doesn’t work, flashing DD-WRT onto the device and then flashing OpenWRT via DD-WRT’s UI will.

After installing, I set up each port on its own VLAN, one for each subnet, and configured each one so the device would be a drop-in replacement for the Celeron box. It took a day or so of tweaking but I’m finally happy with the configuration. I even have a spare port to spin up whenever I want, although currently it’s disabled.

So how well does it work?

The wireless connection is stable; I can push 16-20Mbit/s through it without issues, which is decent for Wireless G. The device can push about 50-60Mbit/s tops between interfaces before its little 300MHz CPU gets saturated. Considering that my Internet connection is 10Mbit/s max, and the things the other ports are connected to top out about 40-50Mbit/s, it works out. For the price and the amount of electricity the device uses, I couldn’t be happier.

There’s two caveats.

One: whoever designed the case probably didn’t take a course on thermodynamics. There are actual vents, which is nice (two of my older routers have nothing more than tiny slots), but they’re around the edge of this plastic dome that collects heat at the top. Ooops! Wishing I had my Dremel tool still. It hasn’t overheated yet, but just in case I raised it up on two mechanical pencils to allow more airflow.

Two: it’s silent. That’s usually a good thing, except the Celeron router wasn’t; it had a single moving part (the power supply fan) that made a comforting whisper 24/7. I’ve had that sound in my ear for the past 4 years whenever I sleep. Now I have to get used to barking dogs and the garbage truck going past at 3AM–or find something else to make an equivalently soft noise. Preferably a something that doesn’t draw 45W power constantly!

 

Fun With Routers, part 2 – Netgear WNR1000v2 VC + OpenWRT

Published by on March 28, 2015 | 3 Responses

Garage sales. Garage sales are awesome. I picked up a Netgear WNR1000v2 VC router at a garage sale for $5 last year. That’s a bargain, until you realize that this router should’ve retailed for $5. The stock firmware is terribad and limited. A JavaScript bug prevents WPS from being disabled unless you visit the administration page using Internet Explorer. It doesn’t help that some of these units were modified by Comcast to only accept certain firmware updates, and then passed out like candy to clueless Internet subscribers who needed a troublesome device to scream at daily. (As if dealing with Comcast wasn’t bad enough already.)

Enough ranting. Here’s the cool part: OpenWRT didn’t support it at the time. No, wait, that’s not the cool part. The cool part is, I accidentally got a custom build of OpenWRT onto the thing after investing in a USB TTL serial adapter and flailing around with OpenWRT’s source code. Wait, that’s still not the cool part.

I don’t remember how I got it working. It was towards the end of last semester, and last semester was two forevers ago in computer years. I posted on the OpenWRT forum but didn’t get any response, and I didn’t know enough about OpenWRT’s internals to submit a patch, so I slapped my hackish build onto the device and immediately forgot about it.

But! A hardworking developer who goes by the handle SaltwaterC took the time to figure out this pesky little device and made some nice builds and patches. That’s the cool part. Thanks, SaltwaterC!

If you have one of these, don’t throw it out! They actually work great with OpenWRT, especially if you can rescue one from the bargain bin at your local thrift store.

MicroTik Routerboard 411 + OpenWRT: Update

Published by on October 31, 2014 | Leave a response

The ailing Routerboard 411 in one of my previous posts has been sitting in a plastic tub under my bed awaiting replacement capacitors, a sudden level-up in my soldering ability, and a dramatic increase in my level of confidence in not destroying things by jabbing at them with a giant heating element. I still have none of the three; however, one of my friends donated his time and effort and replaced the four dead capacitors for me. (Thanks, Will! I owe you a gift card.)

Now that the capacitors have been replaced, I’ve put OpenWRT on the device for good. The instructions here are dubious. I did things the manual way according to this blog post, starting from the point after I had booted into OpenWRT’s ramdisk image as detailed in my previous post about this router.

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Fun with routers, part 1: MicroTik Routerboard 411 + OpenWRT

Published by on July 11, 2014 | 1 Response
Routerboard running OpenWRT Attitude Adjustment

My father uses a WISP for his Internet access. His equipment malfunctioned recently and a technician came out to examine the antenna. He discovered that the circuitry inside it had failed; instead of throwing it away, he offered it to me.

Meet the MicroTik Routerboard 411.

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