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Openwrt Build

Requirements

Make sure you have the prereq pkgs for the Openwrt Image Builder

To use this part of the git repo you will need the following pkgs:

  • git >= 1.8.2
  • git-lfs
  • gomplate >= 3.11.0
  • Docker (Optional)
  • Nixpkgs (Optional)

Gomplate

Installation of gomplate is a little bit tricky since it doesnt come in a .deb:

sudo -i
cd /usr/local/bin/
curl -O https://github.com/hairyhenderson/gomplate/releases/download/<version>/gomplate_linux-amd64 -L
mv gomplate_linux-amd64 gomplate

Docker

You can build these openwrt images inside a docker container. This makes it easy to has a consistent build environment for all members of the tech team.

To start building:

# Make sure to mount the git root inside this container
docker run -v $(git rev-parse --show-toplevel):/home/openwrt/scale-network --rm -it sarcasticadmin/openwrt-build@sha256:3fab43fea9e698bade514af0b84192ec447708c8f24d7c5a5e383464e9c44922  /bin/bash
cd /home/openwrt/scale-network

There is no latest tag so make sure to specify the version (short commit hash) The docker mount only works in linux, on OSX you'll get: "Build dependency: OpenWrt can only be built on a case-sensitive filesystem"

Then continue onto whichever image you'd like to build.

Build

Image No Templates

Build are done per arch with TARGET environment variable (defaults to TARGET=ar71xx:

cd ./openwrt
make build-img

This requires an internet connection since it downloads the Openwrt src github.com and uses some openwrt mirrors.

You will find the images in ./build/source-<commit>/bin/targets/<target>/generic/ The *sysupgrade.bin and *factory.img files match the AP models

Image with Templates

To get the configuration thats used at scale the templates need to be baked into the image.

Copy over the default secrets:

cp ./facts/secrets/openwrt-example.yaml ./facts/secrets/openwrt.yaml

If needed update the defaults in openwrt.yaml to represent actual values

Generate and update the root password hash in openwrt.yaml:

openssl passwd -1 secretpassword

Compile the templates:

cd ./openwrt/
make templates

This will populate the templates with the necessary values and prep them in the build dir. To validate the templates check: ./openwrt/build/source-/files/

Now build the image:

make build-img

This will populate the templates with the necessary values and include them into the Openwrt build

Misc

Adding new packages

common.config

Leverage the existing diffconfig via the Makefile:

TARGET=x86 make config menuconfig

This assumes the additional packages are common to all architectures if not change TARGET to specific board arch

Save pkgs back to common.config with diffconfig using the Makefile and then copy them to the commonconfig:

TARGET=x86 make commonconfig

At which point you should have a diff in git which can then be tested against a new build of the img

mt7622-generic.config

Will use mt7622 as an example but this will work for any other arch we support:

TARGET=mt7622 make config menuconfig

After adding the specific mt7622 arch packages:

TARGET=mt7622 make targetconfig

Update openwrt/opkg

To bump the Makefile to reference the current upstream master branches

make bump

After bumping the version of openwrt/opkg make sure to ensure that the configs are still generated cleanly (no diff)

TARGET=x86 make config menuconfig

Ensure the selections in menuconfig are what your expecting

If it looks good save them back to config/ using:

TARGET=x86 make commonconfig targetconfig

This generates the diff of the base config, then we split it out into the common components and last its arch target configs

Repeat this for TARGET=ar71xx and TARGET=mt7622

TARGET=mt7622 make config menuconfig
TARGET=mt7622 make targetconfig

commonconfig is only generated on x86

Commit the results that are generated. You can ensure that the config options are stable by repeating the process. You should not get a diff.

Build Identity

Depending on the SCaLE conference number, the WPS LED will be ON for even years and OFF for odd years.

NOTE: This depends on the SCaLE conference number from facts.yaml not the year since the build would drift based on when it was built.

Notes

Issues

  1. When iterating on new packages there have been times were the existing config is stale and needs to be completely blown away and regenerated off of master then reconfigured with menuconfig. This is just something to be aware of since its come up during the development of this image.

SSH

  1. /root - Must be permissions 755 (or less perm) or ssh-key auth wont work
  2. openssh needs to have both /etc/passwd and /etc/hosts to allow ssh login

Useful commands

To check which vlans are loaded onto a switch:

swconfig dev switch0 show

Check to see the status of the wifi radios:

wifi status

Make

Troubleshooting

build fails

There are many different packages in the openwrt and the open pkgs repo. Some of the requirements for the build system differ based on upstream changes to both repos. Its best to check the log to see if there was a dependency missed due to these changes. This is also something to account for when bumping the based build system (ubuntu 16.04 vs ubuntu 18.04)

mkhash

If early in the build you recieve bin/mkhash: No such file or directory. Check to make sure that the mkhash binary is linked against the right linker/loader. In some cases you could have mkhash that was build inside or outside of the environment and its unable to the expected loader.

$ file ./staging_dir/host/bin/mkhash
+ file ./staging_dir/host/bin/mkhash
./staging_dir/host/bin/mkhash: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /nix/store/9bh3986bpragfjmr32gay8p95k91q4gy-glibc-2.33-47/lib/ld-linux-x86-64.so.2, for GNU/Linu
x 2.6.32, with debug_info, not stripped

Note: mkhash will exist but be unable to run and fail with the following No such file or directory

make clean-all and rerun inside the local environment should fix it

Config generation process

Assuming we are starting from no existing .config. Lets generate the x86 config first since its the most generic (no specific drivers or modules):

cd <build source>
rm -f *.config

If you already have a true common config (meaning no specific arch or arch packages inside) you can copy it in:

cp $(git root)/openwrt/configs/common.config ./.config

Or create a new one:

make defconfig

Set target to x86/generic

Install only packages which are utilities and non arch specific things. We dont want the hardware packages to pollute the common.config. When youve got all of it selected you can then create the common.config

./scripts/diffconfig.sh | tee .diffconfig | grep -v CONFIG_TARGET > $(git root)/openwrt/configs/common.config

comm -23 <(sort ./.diffconfig) <(sort $(git root)/openwrt/configs/common.config) > $(git root)/openwrt/configs/x86-generic.config

Now we have the common.config and x86-generic.config. To add in a specific board:

cd <build source>
cat $(git root)/openwrt/configs/common.config > ./.config
cat $(git root)/openwrt/configs/x86_generic.config >> ./.config

Run make menuconfig and change the arch from x86 to target arch:

./scripts/diffconfig.sh | tee .diffconfig | grep -v CONFIG_TARGET > $(git root)/openwrt/configs/common.config

comm -23 <(sort ./.diffconfig) <(sort $(git root)/openwrt/configs/common.config) > $(git root)/openwrt/configs/mt7622-generic.config

Assuming mt7622 is our target arch

Thats it now you should have a generic config and a arch specific config going forward. The majority of these steps are taken care of by the Makefile in the openwrt dir but in the cases where we need to start fresh this has been time consuming to recall.