Re: [Buildroot] [PATCH 2/4] package/wpa_supplicant: adding ifupdown support

[Nicolas Cavallari <Nicolas.Cavallari@green-communications.fr>]

Hello,

On 27/05/2022 12:33, Angelo Compagnucci wrote:
> Actually, configuring a wifi interface as per "interfaces" man:
> 
> auto wlan0
> iface wlan0 inet dhcp
> wpa-conf /etc/wpa_supplicant.conf
> 
> doesn't work on buildroot because the line wpa-conf is ignored due to
> the lack of a proper ifupdown script to handle the wpa_supplicant
> initialization.
> 
> The provided file is a simplified version based on the one available
> on debian.
> 
> Signed-off-by: Angelo Compagnucci <angelo@amarulasolutions.com>
> ---
>   package/wpa_supplicant/ifupdown.sh       | 71 ++++++++++++++++++++++++
>   package/wpa_supplicant/wpa_supplicant.mk | 10 ++++
>   2 files changed, 81 insertions(+)
>   create mode 100755 package/wpa_supplicant/ifupdown.sh
> 
> diff --git a/package/wpa_supplicant/ifupdown.sh b/package/wpa_supplicant/ifupdown.sh
> new file mode 100755
> index 0000000000..8eecf73436
> --- /dev/null
> +++ b/package/wpa_supplicant/ifupdown.sh
> @@ -0,0 +1,71 @@
> +#!/bin/sh
> +
> +# This file is executed by ifupdown in pre-up, post-up, pre-down and
> +# post-down phases of network interface configuration.

It is also executed for every interface regardless of if wpa-* options are 
specified or not. ifupdown works by turning all options into IF_* environment 
variables and running all hooks with it.

Right now this hook starts wpa_supplicant on every non-lo interface.
It probably needs a if [ -z "$IF_WPA_CONF" ]; then exit 0; fi somewhere.
The earliest the better.

> +
> +WPA_SUP_BIN="/usr/sbin/wpa_supplicant"
> +
> +if [ -n "$IF_WPA_MAINT_DEBUG" ]; then
> +	set -x
> +fi

It is really necessary to support the "wpa-maint-debug yes" 
/etc/network/interfaces option ?  This script is simple enough, unlike Debian's.

> +
> +# quit if we're called for the loopback
> +if [ "$IFACE" = lo ]; then
> +	exit 0
> +fi

Special-casing lo can be removed by filtering on -z IF_WPA_CONF.  Nobody is 
going to specify a wpa-conf on the lo interface, and if they do, they should 
assume the consequences.

> +
> +# allow wpa_supplicant interface to be specified via wpa-iface
> +# useful for starting wpa_supplicant on one interface of a bridge
> +if [ -n "$IF_WPA_IFACE" ]; then
> +	WPA_IFACE="$IF_WPA_IFACE"
> +else
> +	WPA_IFACE="$IFACE"
> +fi
> +
> +WPA_SUP_PIDFILE="/run/wpa_supplicant.${WPA_IFACE}.pid"
> +
> +# quit if executables are not installed
> +if [ ! -x "$WPA_SUP_BIN" ]; then
> +	exit 0
> +fi
> +
> +do_start () {
> +	if [ -n "$IF_WPA_CONF" ] && [ "$IF_WPA_CONF" != "managed" ]; then
> +		if [ ! -s "$IF_WPA_CONF" ]; then
> +			echo "cannot read contents of $IF_WPA_CONF"
> +			exit 1
> +		fi
> +		WPA_SUP_CONF_CTRL_DIR=$(sed -n -e 's/[[:space:]]*#.*//g' -e 's/[[:space:]]\+.*$//g' \
> +			-e 's/^ctrl_interface=\(DIR=\)\?\(.*\)/\2/p' "$IF_WPA_CONF")
> +		if [ -n "$WPA_SUP_CONF_CTRL_DIR" ]; then
> +			WPA_SUP_CONF="-c $IF_WPA_CONF -C $WPA_SUP_CONF_CTRL_DI > +		else
> +			WPA_SUP_CONF="-c $IF_WPA_CONF"
> +		fi
> +	else
> +		# specify the default ctrl_interface
> +		WPA_SUP_CONF="-C $WPA_CTRL_DIR"
> +	fi
> +}

Debian's ifupdown script need wpa_supplicant to have a ctrl_interface because it 
want to use wpa_cli for all the other wpa-* options, and wpa_cli works by 
connecting to a ctrl_interface.

This script does not use wpa_cli so all the ctrl_interface handling can be 
removed, unless you want to implement the other options later.

By the way, "wpa-conf "managed" is mostly used with the other wpa-* options to 
configure the ssid/passphrase within /etc/network/interfaces, which is something 
your script does not support, so you can remove the first 'if'.
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