Upgrading TP-Link Archer C7 AC1750 to use with OpenWRT

Why OpenWRT?

One of my home access points is TP-Link Archer C7. I purchased it to get all benefits of the 5Ghz 802.11ac standard for the laptop and 2.4Ghz band for the older devices. However, it was never working for me well:

  • In 5Ghz band Apple devices were working very unstable
  • Sometime i had to reboot router because of wifi stability issues. After reboot it was working until next issue. There are no debug options/logs in the native firmware.
  • Device was spamming network with STP packets and some other data, no way to disable.
  • After upgrading to the new firmware versions i had to reconfigure it completely. And in fact difference between regullary updated versions was minimal
  • Native firmware configurable only via web interface, probably backdoors are included :)

So i decided to reflash it to the OpenWRT and found, that i am “happy” owner of the TP-Link Archer C7v1, with AR1A (v1) variant of QCA9880 chip, not supported in the open source ath10k driver. So there is no way to use 5Ghz with OpenWRT at all. Only good thing that 5Ghz chip is not soldered on the board, but connected to the PCIe mini card socket. So i decided to replace it.

Router upgrade

  • I been able to find on the eBay Compex WLE900VX Atheros QCA9880 card. It supports 802.11AC 1.3Gbps 3×3 MIMO 5ghz and is supported by ath10k driver.
  • Before replacing WIFI card you should install OpenWRT or device wont boot at all. I used OpenWRT CC 15.05 for the Archer C7 V1.X, upgrade was done via web interface
  • After OpenWRT is up and running – turn off device and replace WiFi card. Be careful with pigtails, it is very easy to damage them.
  • OpenWRT recognized this card without any additional packages and now working well. You may also want to use alternate firmware from Candela Technologies, there are some reports that it works better then one from vendor.


  • Hardware NAT is not supported. I am not using NAT on it, so i dont really care. Probably on speeds up to 300Mbit it does not matter.
  • Device has only 8Mb of flash. It is enough for the OpenWRT installation (including Luci). There are also 2 USB2 ports, so its easy to extend storage size if needed.


So far everything works great. It is too early to say if stability issues are gone or not, but at least i am now able to do full debug and tuning if needed. I am planning to benchmark router later.

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Lets encrypt!

Some time ago i subscribed to the Lets Encrypt beta participation program. Let’s Encrypt is a free, automated, and open certificate authority (CA), run for the public’s benefit.
Yesterday i finally get an email, telling that my requested domains (smartmontools.org/www.smartmontools.org) are white-listed. So i decided to give it a try.


To use Lets Encrypt! service you will have to install ACME protocol client. ACME (Automatic Certificate Management Environment) is a protocol to automate all operations with PKI certificates. Current implementation is written on Python language and available on the github repository. You could find a lot of information about it usage in the online manual. I was trying to run it on the CentOS 6.7 and installation failed because of old (2.6) Python version. However, after some research, i been able to find a pull request with a patch for the 2.6 support. Hopefully it will go into mainline at some point, because py26 is still widely used. After this i been able to complete installation with letsencrypt-auto.


Lets Encrypt require you to verify that you own requested domain, as most other CA do. However with ACME this cold be done 100% automatically. There are different options on how to do this, initially i tried --standalone option. With it letsencrypt client creates standalone webserver for the authentication. However if you already have web server on port 80 you will have to stop it when client is running. It was working for me, but it requires short downtime, so i decided to look on other options. After all i found webroot authenticator, which allows to just create some files in the web root and later automatically removes them. To automate the process i created configuration file /etc/letsencrypt/cli.ini:

# This is an example of the kind of things you can do in a configuration file.
# All flags used by the client can be configured here. Run Let's Encrypt with
# "--help" to learn more about the available options.

# Use a 2048 or 4096 bit RSA key
rsa-key-size = 2048

# Use production server
server =  https://acme-v01.api.letsencrypt.org/directory

# Uncomment and update to register with the specified e-mail address
email = nospam@example.com

# Uncomment to use a text interface instead of ncurses
text = True

# Uncomment to use the standalone authenticator on port 443
# authenticator = standalone
# standalone-supported-challenges = dvsni

# Uncomment to use the webroot authenticator. Replace webroot-path with the
# path to the public_html / webroot folder being served by your web server.
authenticator = webroot
webroot-path = /var/www/html/smartmontools/static

# automatically agree with license
agree-dev-preview = True

# renew certificate if it is already exists
renew-by-default = True

I also had to make sure that nginx can provide required files to the remote, so i added such lines in my nginx site configuration:

    location /.well-known/acme-challenge/ {
        alias /var/www/html/smartmontools/static/.well-known/acme-challenge/;

To use certificates in nginx i added path to the new certificates and key to the configuration:

    ssl_certificate /etc/letsencrypt/live/smartmontools.org/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/smartmontools.org/privkey.pem;

Now to re-new my certificates i just need to run

./letsencrypt-auto -d smartmontools.org -d www.smartmontools.org certonly

command and it will do the job. Also dont forget to reload nginx service if certificates are already configured.


LetsEncrypt certificates will expire in a 90 days, so it is recommended to renew them every 60 days. Also it is very recommended to setup nagios check to send an alert if expiration time is less then one week. In the feature i would also try to use ACME client on the OpenWRT box, but hopefully there will be some more suitable alternative for the embedded hardware. Finally i would recommend to test your web server SSL configuration with SSL Server Test from SSL Labs.

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Smartmontools daily builds

Sometime i need to audit some servers and often smartmontools is very old, not installed at all (and repositories are broken) or not working for some reasons. Thats one of the reasons why http://builds.smartmontools.org was created. You can download latest SVN builds for the following systems:

  • Darwin (OSX) package, Mach-O universal binary with 2 architectures: i386+x86_64
  • Win32 installer (32 and 64 bit)
  • Linux: i686,x86_64,static and dynamic
  • Source code

Service is now in “experimental” status, please report any issues with it here or on https://smartmontools.org.

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LXC on OpenWRT/Turris presentation

Slides from my presentation @ Turris Evening by cz.nic about LXC in OpenWRT/Turris. Video will follow soon, if you are interested.


Update: video from the presentation:

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Monitoring WAN status on OpenWRT using Alarm Pinger


I am connected to the Internet using wireless link which is sometime not very stable. I decided to monitor status of the link to make sure that I am aware of the problem. Initially i tried to monitor link with Monit or Nagios + fping, but results were not very good, this software is not designed for continues monitoring with very small interval. So I decided to find some alternatives.

About Alarm Pinger

I was using Alarm Pinger (apinger) with pfSense distribution — it was used to monitor WAN links to switch between them if needed.

Alarm Pinger (apinger) is a little tool which monitors various IP devices by simple ICMP echo requests. There are various other tools, that can do this, but most of them are shell or perl scripts, spawning many processes, thus much CPU-expensive, especially when one wants continuous monitoring and fast response on target failure. Alarm Pinger is a single program written in C, so it doesn’t need much CPU power even when monitoring many targets with frequent probes. Alarm Pinger supports both IPv4 and IPv6.

This tool supports multiply monitoring targets, external scripts, email notification, daemon mode. Only problem was that tool was not available as OpenWRT package. So i decided to port it.

OpenWRT port

After few tests I found, that code can be compiled with only few minor patches (autoconf related). You can grab Makefile for package from this pull request. Hopefully it will be integrated in the official packages feed soon. Update: port merged.
Port provides init.d script and sample configuration. In the feature I am also planning to make Luci integration to show link status from the web interface.

To buid package on Turris I would recommend to use my turris buildroot docker image.

## Service configuration

I am using very simple configuration to monitor status of the Wireless link using pings to the ISP gateway:

# we need to use root because "rainbow" tool fails to work from other uid. 
user "root"
group "root"

# status file with link quality information
status {
    file "/tmp/apinger.status"
    interval 1s
# command to run, with alarm type and reason
# if used with multiply targets %t needs to be added
alarm default {
    command on "/root/gateway.sh %A %r"
    command off "/root/gateway.sh %A %r"
# This alarm will be fired when target doesn't respond for 30 seconds.
alarm down "down" {
    time 30s
# This alarm will be fired when responses are delayed more than 80ms
# it will be canceled, when the delay drops below 50ms
alarm delay "delay" {
    delay_low 50ms
    delay_high 80ms
# This alarm will be fired when packet loss goes over 5%
# it will be canceled, when the loss drops below 3%
alarm loss "loss" {
    percent_low 3
    percent_high 5
target default {
    interval 1s
    avg_delay_samples 10
    avg_loss_samples 50
    avg_loss_delay_samples 20
    alarms "down","delay","loss"
# ISP Gateway host to monitor. You can define many targets in case of MultiWAN. 
target "" {
    description "ISP Gateway"

Also I am using simple script to change WAN LED color in case of problems:


DEF_COLOR=33FF33 # see https://gitlab.labs.nic.cz/turris/rainbow/blob/master/turris.c

logger "event: $@"
# read data from status file
STATUS=`grep  "Active alarms:" /tmp/apinger.status`

case "$@" in
"delay ALARM")
  touch /tmp/apinger.delay.flag
"delay alarm canceled")
  rm -f /tmp/apinger.delay.flag
"down ALARM")
  touch /tmp/apinger.down.flag
"down alarm canceled")
  rm -f /tmp/apinger.down.flag
"loss ALARM")
  touch /tmp/apinger.loss.flag
"loss alarm canceled")
  rm -f /tmp/apinger.loss.flag
# link is down
if [ -e /tmp/apinger.down.flag ]; then
# loss or delay
if [ -e /tmp/apinger.loss.flag -o -e /tmp/apinger.delay.flag ]; then
# no active alarms found

This works pretty good – if line is down – WAN color is red, if it is unstable or congested – yellow. We can also monitor link status manually:

root@turris:~# cat /tmp/apinger.status
Fri Apr 10 12:39:24 2015

Description: ISP Gateway
Last reply received: #2876 Fri Apr 10 12:39:23 2015
Average delay: 3.247ms
Average packet loss: 0.0%
Active alarms: None
Received packets buffer: ################################################## ###################.


I am planning to extend functionality of the script with some cool features:

  • Integrate with Luci to show status in the web interface.
  • Add support for the failover switch to the LTE channel if link is down (and LTE dongle connected).
  • Enable rrdtools support provided by apinger.
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How to watch youtube live stream using VLC (or other players)

I like to watch @hromadske.tv, which using Youtube to distribute live stream over Internet. I don`t like browser as player, because of many reasons, including:

  1. Stream will die if i need to restart/quit browser
  2. Google like to play with it (html5/swf changes, etc) and sometime it stops working or works buggy
  3. Sometime it is automatically switching to the 720p or 1080p and utilizing too much bandwidth without real need.
  4. VLC and other players supports Remote Control, advanced audio/video control, etc.

To watch live stream in VLC we will need to get stream format first. I am doing this using youtube-dl tool:
bash-3.2$ youtube-dl --list-formats https://www.youtube.com/watch?v=oHZKYHCDy9Q
oHZKYHCDy9Q: Downloading webpage
oHZKYHCDy9Q: Extracting video information
oHZKYHCDy9Q: Downloading formats manifest
oHZKYHCDy9Q: Downloading DASH manifest
[info] Available formats for oHZKYHCDy9Q:
format code extension resolution note
140 m4a audio only DASH audio 144k , m4a_dash container, aac @128k (48000Hz)
141 m4a audio only DASH audio 272k , m4a_dash container, aac @256k (48000Hz)
160 mp4 256x144 DASH video 124k , 15fps, video only
133 mp4 426x240 DASH video 258k , 30fps, video only
134 mp4 640x360 DASH video 616k , 30fps, video only
135 mp4 854x480 DASH video 1116k , 30fps, video only
136 mp4 1280x720 DASH video 2216k , 30fps, video only
137 mp4 1920x1080 DASH video 4141k , 30fps, video only
151 mp4 72p HLS
132 mp4 240p HLS
92 mp4 240p HLS
93 mp4 360p HLS
94 mp4 480p HLS
95 mp4 720p HLS
96 mp4 1080p HLS (best)

I found that HLS format works well with VLC. I will choose 480p (format 94) to use with VLC. It is possible to get URL using this command:
youtube-dl -f 94 -g https://www.youtube.com/watch?v=oHZKYHCDy9Q

Resulted URL can be played by VLC, ffplay from ffmpeg or QuickTime player. Also you can send it directly this way:
vlc youtube-dl -f 94 -g https://www.youtube.com/watch?v=oHZKYHCDy9Q

How to access Integrated Management Module on IBM System x3650 M3 server under FreeBSD

IBM System x3650 M3 server provides nice looking Integrated Management Module (IMM) GUI/CLI which can be accessed remotely (using dedicated network interface) or directly from host. In this short article I will describe how to do this from FreeBSD host machine.All tests were done with FreeBSD 10.1-RELEASE-p6 using GENERIC kernel.

  1. We will need to find virtual network card provided by IMM (RNDISCDC ETHER IBM):
    root@host /root]# usbconfig
    ugen0.1: <UHCI root HUB Intel> at usbus0, cfg=0 md=HOST spd=FULL (12Mbps) pwr=SAVE (0mA)
    ugen2.1: <EHCI root HUB Intel> at usbus2, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=SAVE (0mA)
    ugen1.1: <UHCI root HUB Intel> at usbus1, cfg=0 md=HOST spd=FULL (12Mbps) pwr=SAVE (0mA)
    ugen4.1: <UHCI root HUB Intel> at usbus4, cfg=0 md=HOST spd=FULL (12Mbps) pwr=SAVE (0mA)
    ugen3.1: <UHCI root HUB Intel> at usbus3, cfg=0 md=HOST spd=FULL (12Mbps) pwr=SAVE (0mA)
    ugen6.1: <EHCI root HUB Intel> at usbus6, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=SAVE (0mA)
    ugen5.1: <UHCI root HUB Intel> at usbus5, cfg=0 md=HOST spd=FULL (12Mbps) pwr=SAVE (0mA)
    ugen3.2: <RNDISCDC ETHER IBM> at usbus3, cfg=1 md=HOST spd=FULL (12Mbps) pwr=ON (100mA)
    In our case it is ugen3.2.
  2. This USB device supports 2 USB configuration – default (and active on boot) – RNDIS or alternate – CDC. FreeBSD works fine with CDC, so we need to switch this USB device to it:
    root@host /root]# usbconfig -d ugen3.2 set_config 1
    After this device should be detected by FreeBSD and dmesg should contain something like this:
    umodem0: at uhub4, port 2, addr 2 (disconnected)
    cdce0: on usbus3
    ue0: on cdce0
    ue0: Ethernet address: e6:1f:13:5e:ab:cd
  3. Now only thing left is to run dhclient on the new network interface:
    [root@host /root]# dhclient ue0
    DHCPREQUEST on ue0 to port 67
    DHCPACK from
    bound to -- renewal in 300 seconds.

    Here we can see that address of the IMM is We can use it to connect with telnet or https to get IMM interface.
  4. Username should be admin, and password could be changed using “ipmitool” utility:
    [root@host /root]# ipmitool user set password 2

Thats it :) Using IMM you can manage your hardware, monitor server and do many other interesting things.

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Asterisk g729 codec for the OpenWRT.

Today OpenWRT telephony maintainers committed codec_g729 to the feed. I am already using this package on my home router and it works pretty well. Binary packages should be available soon.

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Digium, WTF?

Today i visited Asterisk community forums and got this:

You have been permanently banned from this board.
Please contact the Board Administrator for more information.
A ban has been issued on your username.

My last post was a answer in thread were someone was asking for g.729 codec for the ARM platform. I proposed to test my patch for the bcg729 codec and was permanently banned with all my posts deleted :)

Just in case:

  1. I am not implementing g.729 functionality and using open-source GPLv2 project bcg729 available in the net.
  2. You might have to pay royalty fees to the G.729 patent holders for using their algorithm.
  3. The G.729 codec from Digium is supported for use only on Linux x86 and x86_64 environments.

I already wrote mail to the board administrator, but i think they are just banning everyone with non-blob g.729 implementation. I would recommend them to spend some time for porting their solution to more platforms instead :)

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Using g.729 codec with Asterisk on Raspberry Pi (or other ARM device)

I decided to build home PBX based on Asterisk VoIP server running on my Raspberry Pi device. One of the reasons for this was ability to build cheap GSM gate for home use using chan_dongle. But one of the problems i have found was lack of g.729 codec for the Asterisk on ARM.

On Intel platform it is possible to use codecs from asterisk.hosting.lv or to buy commercial codec from Digium. Unfortunately its not the case for the ARM. So i decided to see if it possible to port some existing g.729 codec.

Project asterisk-g72x is only Open Source g.729 for Asterisk implementation i am aware of. Internally it is using 2 libraries:

  • IPP from Intel
  • Or ITU based reference code.

It is not possible to compile recent IPP versions on ARM and a lot of ASM code making porting of it problematic. ITU g.729 code is on a plain C, but is painfully slow. It compiles on ARM, but performance is terrible. Asterisk eating 100% of CPU on recoding and drops frames. So it was not an option. So i decided to find alternative codec. In the net i found 2 Open Source projects with g.729 implementation suitable for ARM

  1. Experimental version of G.729 codec for ARM device. It seems to be ITU source code with ARM assembler code for some operations.This code also using many global variables so is not ready for multi-thread software like asterisk without additional changes. Also there are issues open from 2011 without any reaction from developers.
  2. Bcg729. It is a software G729A encoder and decoder library written in C, developed by Belledonne Communications, the company supporting the Linphone project. It was written from scratch and is NOT a derivative work of ITU reference source code in any kind.

BCG 729 also supports concurrent channel encoding/decoding for multi-call applications such as Asterisk. I was able to adopt bcg729 for use with asterisk-g72x project, instead of slow ITU code. If you want to test it – use my BitBucker fork. I will post benchmarks later, but now i see about 15-20% CPU load on g.729 encoding with Asterisk, so it should be able to support 4-5 concurrent channels in time.

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