On Wed, 2009-02-04 at 16:08 +0100, Samuel Ortiz wrote:
> From: Samuel Ortiz <samuel.ortiz@xxxxxxxxx>
>
> In very dense environment, the scan result buffer can get really large, mostly
> due to the addition of proprietary IEs. iwlist fails, typically warning about:
> "print_scanning_info: Allocation failed". wpa_supplicant fails as well, after
> reallocating the scan result buffer several times, up to 132 Kbytes:
> [snip]
> Scan results did not fit - trying larger buffer (131072 bytes)
> ioctl[SIOCGIWSCAN]: Argument list too long
>
> By adding a mac80211 module parameter, we can filter the scan results and keep
> only the ones userspace currently worries about, i.e. WPA1, WPA2, WMM and WPS.
>
> To activate this feature, 1 has to be written to
> /sys/module/mac80211/parameters/ieee80211_scan_ie_filter
NAK. Use cfg80211. Module parameters are the wrong way to work around
API limitations; the API gets fixed or replaced instead. Furthermore,
the stack/drivers should *NOT* be filtering scan results at all. That's
the job of the userspace program requesting the results; otherwise
passive listeners will get only filtered results, and not the complete
scan list.
Dan
> Signed-off-by: Samuel Ortiz <samuel.ortiz@xxxxxxxxx>
> ---
> net/mac80211/ieee80211_i.h | 1
> net/mac80211/scan.c | 65 ++++++++++++++++++++++++++++++---------------
> net/mac80211/util.c | 40 +++++++++++++++++++++++++++
> 3 files changed, 85 insertions(+), 21 deletions(-)
>
> Index: wireless-testing/net/mac80211/scan.c
> ===================================================================
> --- wireless-testing.orig/net/mac80211/scan.c 2009-01-28 11:37:55.000000000 +0100
> +++ wireless-testing/net/mac80211/scan.c 2009-01-28 17:32:48.000000000 +0100
> @@ -31,6 +31,11 @@
> #define IEEE80211_CHANNEL_TIME (HZ / 33)
> #define IEEE80211_PASSIVE_CHANNEL_TIME (HZ / 5)
>
> +static int ieee80211_scan_ie_filter;
> +module_param(ieee80211_scan_ie_filter, bool, 0644);
> +MODULE_PARM_DESC(ieee80211_scan_ie_filter,
> + "Filter IEs from scan results");
> +
> void ieee80211_rx_bss_list_init(struct ieee80211_local *local)
> {
> spin_lock_init(&local->bss_lock);
> @@ -725,33 +730,51 @@ static void ieee80211_scan_add_ies(struc
> if (bss == NULL || bss->ies == NULL)
> return;
>
> - /*
> - * If needed, fragment the IEs buffer (at IE boundaries) into short
> - * enough fragments to fit into IW_GENERIC_IE_MAX octet messages.
> - */
> pos = bss->ies;
> end = pos + bss->ies_len;
>
> - while (end - pos > IW_GENERIC_IE_MAX) {
> - next = pos + 2 + pos[1];
> - while (next + 2 + next[1] - pos < IW_GENERIC_IE_MAX)
> - next = next + 2 + next[1];
> + if (ieee80211_scan_ie_filter) {
> + while (pos - end) {
> + next = pos + 2 + pos[1];
> + if (ieee80211_filter_ie(pos)) {
> + memset(&iwe, 0, sizeof(iwe));
> + iwe.cmd = IWEVGENIE;
> + iwe.u.data.length = next - pos;
> + *current_ev =
> + iwe_stream_add_point(info, *current_ev,
> + end_buf, &iwe,
> + pos);
> + }
> + pos = next;
> + }
> + } else {
> + /*
> + * If needed, fragment the IEs buffer (at IE boundaries) into
> + * short enough fragments to fit into IW_GENERIC_IE_MAX octet
> + * messages.
> + */
> +
> + while (end - pos > IW_GENERIC_IE_MAX) {
> + next = pos + 2 + pos[1];
> + while (next + 2 + next[1] - pos < IW_GENERIC_IE_MAX)
> + next = next + 2 + next[1];
>
> - memset(&iwe, 0, sizeof(iwe));
> - iwe.cmd = IWEVGENIE;
> - iwe.u.data.length = next - pos;
> - *current_ev = iwe_stream_add_point(info, *current_ev,
> - end_buf, &iwe, pos);
> + memset(&iwe, 0, sizeof(iwe));
> + iwe.cmd = IWEVGENIE;
> + iwe.u.data.length = next - pos;
> + *current_ev = iwe_stream_add_point(info, *current_ev,
> + end_buf, &iwe, pos);
>
> - pos = next;
> - }
> + pos = next;
> + }
>
> - if (end > pos) {
> - memset(&iwe, 0, sizeof(iwe));
> - iwe.cmd = IWEVGENIE;
> - iwe.u.data.length = end - pos;
> - *current_ev = iwe_stream_add_point(info, *current_ev,
> - end_buf, &iwe, pos);
> + if (end > pos) {
> + memset(&iwe, 0, sizeof(iwe));
> + iwe.cmd = IWEVGENIE;
> + iwe.u.data.length = end - pos;
> + *current_ev = iwe_stream_add_point(info, *current_ev,
> + end_buf, &iwe, pos);
> + }
> }
> }
>
> Index: wireless-testing/net/mac80211/util.c
> ===================================================================
> --- wireless-testing.orig/net/mac80211/util.c 2009-01-28 11:37:41.000000000 +0100
> +++ wireless-testing/net/mac80211/util.c 2009-01-28 15:57:03.000000000 +0100
> @@ -675,6 +675,46 @@ void ieee802_11_parse_elems(u8 *start, s
> }
> }
>
> +/*
> + * ieee80211_filter_ie() tries to keep only the relevant IEs for
> + * userspace (mostly hostap code).
> + */
> +int ieee80211_filter_ie(u8 *ie)
> +{
> + u8 id, ie_len, *pos;
> + u8 microsoft_oui[4] = {0x00, 0x50, 0xf2};
> + u8 wpa2_oui[3] = {0x00, 0x0f, 0xac};
> +
> + pos = ie;
> + id = *pos++;
> + ie_len = *pos++;
> +
> + switch (id) {
> + case WLAN_EID_RSN:
> + /* WPA2 */
> + if (ie_len >= 3 &&
> + !memcmp(pos, wpa2_oui, 3))
> + return 1;
> +
> + return 0;
> +
> + case WLAN_EID_VENDOR_SPECIFIC:
> + /* We're trying to catch WPA1, WMM and WPS IEs. */
> + if (ie_len >= 3 &&
> + !memcmp(pos, microsoft_oui, 3)) {
> + if ((pos[3] == 1) || /* WPA1 */
> + (pos[3] == 2) || /* WMM */
> + (pos[3] == 4)) /* WPS */
> + return 1;
> + }
> +
> + return 0;
> +
> + default:
> + return 0;
> + }
> +}
> +
> void ieee80211_set_wmm_default(struct ieee80211_sub_if_data *sdata)
> {
> struct ieee80211_local *local = sdata->local;
> Index: wireless-testing/net/mac80211/ieee80211_i.h
> ===================================================================
> --- wireless-testing.orig/net/mac80211/ieee80211_i.h 2009-01-28 11:37:41.000000000 +0100
> +++ wireless-testing/net/mac80211/ieee80211_i.h 2009-01-28 13:49:17.000000000 +0100
> @@ -1028,6 +1028,7 @@ void ieee80211_tx_skb(struct ieee80211_s
> int encrypt);
> void ieee802_11_parse_elems(u8 *start, size_t len,
> struct ieee802_11_elems *elems);
> +int ieee80211_filter_ie(u8 *ie);
> int ieee80211_set_freq(struct ieee80211_sub_if_data *sdata, int freq);
> u32 ieee80211_mandatory_rates(struct ieee80211_local *local,
> enum ieee80211_band band);
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