Building OpenWRT with Nix (discuss on 35C3?)

Mic92 · December 29, 2018, 9:09am

You might have found that one already: https://github.com/nix-community/nix-environments/tree/master/envs/openwrt
This provides the environment for building openwrt. The first thing you would need to do is packaging their SDK, which is basically the build toolchain that includes all their compiler, linker and other build-tools. I see several options there in increasing order of difficulty

Download & Patchelf their SDK (take a look at our android infrastructure: Mobile updates by svanderburg · Pull Request #50596 · NixOS/nixpkgs · GitHub)
Use our pkgsCross to emulate their SDK with our build tools (don’t forgot that we use cc-wrappers, so use the unwrapped compilers).
Try to build the SDK (I had problems with NixOS doing that, they had a few shebangs, but something forced me to use buildFHSUserEnv but I no longer remember the exact issues)

From their one could make use of their data structures to import their checksums into nix with by sourcing their checksums with make and to download them with fetchurl:

github.com

openwrt/packages/blob/2dcbb6f240482c1782ca95078673ff8fc089f9e6/net/freeradius3/Makefile#L16


      
          #
          
          
include $(TOPDIR)/rules.mk
          
          
PKG_NAME:=freeradius3
          PKG_VERSION:=release_3_0_17
          PKG_RELEASE:=2
          
          
PKG_SOURCE:=$(PKG_VERSION).tar.gz
          PKG_SOURCE_URL:=https://github.com/FreeRADIUS/freeradius-server/archive
          PKG_HASH:=5b2382f08c0d9d064298281c1fb8348fc13df76550ce7a5cfc47ea91361fad91
          
          
PKG_MAINTAINER:=Lucile Quirion <lucile.quirion@savoirfairelinux.com>
          PKG_LICENSE:=GPL-2.0
          PKG_LICENSE_FILES:=COPYRIGHT LICENSE
          
          
PKG_BUILD_DIR:=$(BUILD_DIR)/freeradius-server-$(PKG_VERSION)
          PKG_FIXUP:=autoreconf
          
          
PKG_CONFIG_DEPENDS := \
            FREERADIUS3_OPENSSL \

If you can extract the packages that a particular openwrt config tries to build then you could make sure to download all sources ahead of time and maybe split each package into its own derivation followed by a final image building step.
The openwrt buildsystem is stupid but quiet effective at hiding useful error message from the user, to debug it is useful to remove some 2>/dev/null redirections from their Makefiles or use something like sysdig -c stderr. I am also on 35c3 and also abradar is. I am not so much interested in pulling that exact project of as this is quiet a lot of work I would rather like to put into improving our cross-compiling infrastructure, but I would be at the assembly, if you want to discuss some details.