Re: ifconfig reporting SIOCSIFMEDIA Device not configured error

On Thursday, July 21, 2022 5:05:19 PM EDT you wrote:
> Hi all,
> 
> I am setting up a device driver in monitor mode, but appear to be getting an
> `ifconfig` error that I do not understand.
> 
> Specifically, when I set my device to be in monitor mode, I receive this
> error:
> 
> ```
> $ ifconfig wlan create wlandev athn0 mode monitor
> ifconfig: SIOCSIFMEDIA (media): Device not configured
> ```
> 
> This creates a `wlan0` interface, but `ifconfig` reports this error. What
> might be causing this? I am certain I am missing a step in the ic_vap_create
> or ic_ioctl handlers or something related, but what might that be?
> 
> I searched for SIOCSIFMEDIA in the kernel source of drivers I know, but do
> not see anything that looks relevant. I could back out from the ifconfig
> source to figure out the exact cause, but that might take a while and was
> hoping someone here could/would shortcut that research.
> 
> For context my WIP code is located here (https://github.com/khanzf/freebsd/
> tree/ar9271/sys/dev/athn). This is an attempt to port OpenBSD's athn,
> currently focusing on the USB driver.
> 
> Thank you.
> 
> - Farhan

I was wrong, I have not been able to solve this problem after a few days.

I gather that the error condition begins after I create the VAP, which I do 
via:

# ifconfig wlan create wlandev athn0 mode monitor
ifconfig: SIOCSIFMEDIA (media): Device not configured

The error condition seems to begin in ifmedia_ioctl() in:
/usr/src/sys/net/if_media.c, specifically the ifmedia_match function fails. 
This is here:
https://github.com/freebsd/freebsd-src/blob/main/sys/net/if_media.c#L227

I enabled the printf debugging message here:
```
printf("ifmedia_ioctl: no media found for %#010x mask %#010x\n", newmedia, 
ifm->ifm_mask);
```

And then I receive this kernel message:
ifmedia_ioctl: no media found for 0xffffffff mask 0000000000

I do not understand what this means. Why is newmedia set to 0xffffffff and 
ifm->ifm_mask set to 0000000000? What am I am missing such that this error is 
happening? I searched through /usr/src/sys/dev/usb/wlan and only see one usage 
of `struct ifreq`.

Please help, stuck :/

- Farhan