[PATCH iwinfo] nl80211: restore iterating over all devices in nl80211_phy2ifname()

[Christian Marangi]

On Mon, Jan 30, 2023 at 07:57:57PM +0100, Andre Heider wrote:
> This reverts to the earlier behaviour, because:
> * phys can be renamed, which breaks hardcoding "phy%d"
> * /sys/class/ieee80211/*/device can return networks of other phys,
>   since "device" is a symlink which can have multiple phys
> 
> The earlier behaviour fixes both points.
> 
> Fixes: 6194aaf0 "nl80211: simplify iterating over phy's devices"
> Fixes: #11902
> Signed-off-by: Andre Heider <a.heider at gmail.com>
> Tested-by: Olcay Korkmaz <nuke_mania at hotmail.com>

I remember we had some good stats of the timing improvement of
6194aaf05244241d2f51c471a43584f8d80b64ce. Does this reintroduce the
additional slowdown? Should we add this as a fallback if the interface
is not found using the expected way?

> ---
>  iwinfo_nl80211.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/iwinfo_nl80211.c b/iwinfo_nl80211.c
> index 5bc2f51..50bb8f0 100644
> --- a/iwinfo_nl80211.c
> +++ b/iwinfo_nl80211.c
> @@ -825,13 +825,15 @@ static char * nl80211_phy2ifname(const char *ifname)
>  
>  	memset(nif, 0, sizeof(nif));
>  
> -	snprintf(buffer, sizeof(buffer),
> -	         "/sys/class/ieee80211/phy%d/device/net", phyidx);
> -
> -	if ((d = opendir(buffer)) != NULL)
> +	if ((d = opendir("/sys/class/net")) != NULL)
>  	{
>  		while ((e = readdir(d)) != NULL)
>  		{
> +			snprintf(buffer, sizeof(buffer),
> +			         "/sys/class/net/%s/phy80211/index", e->d_name);
> +			if (nl80211_readint(buffer) != phyidx)
> +				continue;
> +
>  			snprintf(buffer, sizeof(buffer),
>  			         "/sys/class/net/%s/ifindex", e->d_name);
>  			cifidx = nl80211_readint(buffer);
> -- 
> 2.39.0
> 
> 
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