[PATCH] wpa_supplicant: Work around odd driver-reported ssid lengths

Pedro Ramalhais ramalhais at serrado.net
Thu Jan 12 11:54:31 EST 2006

On Thu, 2006-01-12 at 11:30 -0500, Dan Williams wrote:
> Hi,
> At least the atmel and airo drivers do odd, technically incorrect,
> things in their SIOCGIWESSID:
>         memcpy(extra, status_rid.SSID, status_rid.SSIDlen);
>         extra[status_rid.SSIDlen] = '\0';
>         /* If none, we may want to get the one that was set */
>         /* Push it out ! */
>         dwrq->length = status_rid.SSIDlen + 1;
> Atmel does roughly the same thing.  They both append a '\0' to the end,
> and push that to userspace.  I'm unsure whether or not NULL is a legal
> character in an SSID, but these drivers do it.
> wpa_supplicant does not handle it; in the wpa_supplicant_get_ssid()
> function, it compares the internal SSID from the config file to the
> value returned by the driver.  If the lengths of the two do not match,
> no wpa_ssid structure is returned.  In this odd case, then lengths do
> not match, but the AP is clearly the correct AP to use.
> Patch attached.  It checks if the last byte of the SSID reported by the
> driver is NULL, and if so, decrements the driver-reported length.  I
> think this is an acceptable solution.
> Thanks,
> Dan

AFAIK an ESSID is a length of bytes and 0 ('\0' or NULL) is a valid
byte. The problem is that some applications use (or used) the ESSID
directly to print it, and so, they rely on having a 0 at the end of the
string. I'm not sure how wireless tools handles it, and i don't know if
it does it in the correct way.
Pedro Ramalhais <ramalhais at serrado.net>

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