[RFC] hostapd: DFS - handle running out of DFS channels

[Petko Bordjukov]

Hello,

Is there a reason why merging this would be a bad idea? I think it is a 
neat functionality to have.

Regards,
P.

On  Fri Oct 9 05:58:34 PDT 2015 Zefir Kurtisi wrote:

> In scenarios where only DFS channels are available (e.g. outdoor,
> special countrycodes), hostapd must be able to handle situations
> where all are unavailable.
>
> The two possibilities to get there are
> 1) while operating on the last available DFS channel a radar is
>    detected
> 2) hostapd is started while all channels are unavailable
>
> In both cases, hostapd instead of terminating should better
> wait for the NOPs to pass and re-try operation after the CAC.
>
> This patch attempts to provide this feature with minimal modifi-
> cation of the existing DFS framework. It uses the condition
> (iface->state == HAPD_IFACE_DFS && !iface->cac_started)
> as NOP mode signature to retry operation from within
> hostapd_dfs_nop_finished().
>
> Signed-off-by: Zefir Kurtisi <zefir.kurtisi at neratec.com>
> ---
>  src/ap/dfs.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/src/ap/dfs.c b/src/ap/dfs.c
> index 7273caa..7e9acfd 100644
> --- a/src/ap/dfs.c
> +++ b/src/ap/dfs.c
> @@ -660,13 +660,14 @@ int hostapd_handle_dfs(struct hostapd_iface *iface)
>  	}
>
>  	iface->cac_started = 0;
> +	hostapd_set_state(iface, HAPD_IFACE_DFS);
>
>  	do {
>  		/* Get start (first) channel for current configuration */
>  		start_chan_idx = dfs_get_start_chan_idx(iface,
>  							&start_chan_idx1);
>  		if (start_chan_idx == -1)
> -			return -1;
> +			return 0;
>
>  		/* Get number of used channels, depend on width */
>  		n_chans = dfs_get_used_n_chans(iface, &n_chans1);
> @@ -704,7 +705,7 @@ int hostapd_handle_dfs(struct hostapd_iface *iface)
>  							skip_radar);
>  			if (!channel) {
>  				wpa_printf(MSG_ERROR, "could not get valid channel");
> -				return -1;
> +				return 0;
>  			}
>
>  			iface->freq = channel->freq;
> @@ -716,7 +717,6 @@ int hostapd_handle_dfs(struct hostapd_iface *iface)
>  	} while (res);
>
>  	/* Finally start CAC */
> -	hostapd_set_state(iface, HAPD_IFACE_DFS);
>  	wpa_printf(MSG_DEBUG, "DFS start CAC on %d MHz", iface->freq);
>  	wpa_msg(iface->bss[0]->msg_ctx, MSG_INFO, DFS_EVENT_CAC_START
>  		"freq=%d chan=%d sec_chan=%d, width=%d, seg0=%d, seg1=%d, cac_time=%ds",
> @@ -793,7 +793,6 @@ static int hostapd_dfs_start_channel_switch_cac(struct hostapd_iface *iface)
>
>  	if (!channel) {
>  		wpa_printf(MSG_ERROR, "No valid channel available");
> -		hostapd_setup_interface_complete(iface, err);
>  		return err;
>  	}
>
> @@ -858,8 +857,8 @@ static int hostapd_dfs_start_channel_switch(struct hostapd_iface *iface)
>  						&vht_oper_centr_freq_seg1_idx,
>  						skip_radar);
>  		if (!channel) {
> -			/* FIXME: Wait for channel(s) to become available */
> -			hostapd_disable_iface(iface);
> +			wpa_printf(MSG_INFO, "%s: no DFS channels left, "
> +				   "waiting for NOP to finish", __func__);
>  			return err;
>  		}
>
> @@ -982,6 +981,9 @@ int hostapd_dfs_nop_finished(struct hostapd_iface *iface, int freq,
>  	/* TODO add correct implementation here */
>  	set_dfs_state(iface, freq, ht_enabled, chan_offset, chan_width,
>  		      cf1, cf2, HOSTAPD_CHAN_DFS_USABLE);
> +
> +	if (iface->state == HAPD_IFACE_DFS && !iface->cac_started)
> +		hostapd_handle_dfs(iface);
>  	return 0;
>  }
>
> --
> 2.5.0