[Buildroot] Recommended way to auto-reconnect wifi?

[Peter Seiderer]

Hello Jeremy, Nicolas,

On Wed, 22 Sep 2021 10:19:27 +0200, Nicolas Cavallari <nicolas.cavallari at green-communications.fr> wrote:

> On 22/09/2021 02:16, Jeremy Fleischman wrote:
> > I've been happily using buildroot for a growing number of Raspberry PIs at
> > home. However, I've noticed that whenever our wifi cuts out, they do not
> > reconnect when it comes back.
> >
> > I've got them configured using BusyBox init + mdev + ifupdown +
> > wpa_supplicant. I've skimmed through /etc/inittab, and I think I understand
> > how everything is wired together:
> >
> >    - /etc/init.d/S10mdev: mdev starts up, and asynchronously starts
> > discovering devices.
> >    - /etc/init.d/S40network: This runs /sbin/ifup -a. I think this runs
> > while mdev is still discovering devices, which is fine, because there's a
> > wait-delay configured in /etc/network/interfaces:
> >
> > # cat /etc/network/interfaces
> > auto lo
> > iface lo inet loopback
> >
> > auto wlan0
> > iface wlan0 inet dhcp
> >      hostname thermometer
> >      pre-up wpa_supplicant -D nl80211 -i wlan0 -c /etc/wpa_supplicant.conf -B
> >      post-down killall -q wpa_supplicant
> >      *wait-delay 15*
> >
> > iface default inet dhcp
> >
> > As far as I can tell, this all only ever happens at startup, and there
> > isn't any mechanism that would attempt to reconnect to a wifi network after
> > a disconnect. I've done some googling, and here's what I've learned:
> >
> >    - I'm pretty sure that wpa_supplicant is not supposed to handle this.
> >    - It looks like some people write scripts to handle this for themselves.
> > See this SO answer <https://raspberrypi.stackexchange.com/a/5121> and
> > this dweeber/WiFi_Check
> > repo <https://github.com/dweeber/WiFi_Check>.
> >
> > Am I correct that this is something I should fix by adding some sort of
> > background/cron process to do something like the WiFi_Check script above?
> > Or is this something buildroot does have baked in support for, and I just
> > haven't found it yet?
>
> Buildroot has nothing out of the box for this, short of
> NetworkManager/connman or the likes.
>
> In your case, wpasupplicant should reconnect automatically if it is
> disconnected, but the busybox DHCP client, udhcpc  won't retry
> indefinitely by default. If you use a custom busybox configuration, you
> can modify CONFIG_IFUPDOWN_UDHCPC_CMD_OPTIONS to make udhcpc go into
> background and retry indefinitely.

Alternatively use the following patch [1] to change the ifupdown-scripts...,
or do a complete change away from wpasupplicant and use iwd (see [2])
providing AutoConnect and DHCP...

Regards,
Peter

[1] https://patchwork.ozlabs.org/project/buildroot/patch/20210216202022.27264-1-ps.report@gmx.net/
[2] https://iwd.wiki.kernel.org/start


>
> Also, note that you can copy the Debian ifupdown scripts into your image
> and then use the Debian's wpa-* options in /etc/network/interface. You
> will have to tweak them a bit because buildroot install wpasupplicant in
> /usr/sbin instead of /sbin.
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