Re: [PATCH v2 2/3] cfg80211: Add support to randomize TA of Public Action frames

[Johannes Berg]

On Mon, 2017-01-09 at 19:53 +0200, Jouni Malinen wrote:
> 
> + if (!wdev->current_bss &&
> + !wiphy_ext_feature_isset(
> + >wiphy,
> + NL80211_EXT_FEATURE_MGMT_TX_RANDOM_TA))
> + return -EINVAL;
> + if (wdev->current_bss &&
> + !wiphy_ext_feature_isset(
> + >wiphy,
> + NL80211_EXT_FEATURE_MGMT_TX_RANDOM_TA_CO
> NNECTED))
> + return -EINVAL;
> + }

This current_bss stuff is going to be somewhat racy, but I guess we can
live with that.

Looks good, but doesn't apply without the first patch.

johannes

[PATCH v2 2/3] cfg80211: Add support to randomize TA of Public Action frames

[Jouni Malinen]

From: vamsi krishna 

Add support to use a random local address (Address 2 = TA in transmit
and the same address in receive functionality) for Public Action frames
in order to improve privacy of WLAN clients. Applications fill the
random transmit address in the frame buffer in the NL80211_CMD_FRAME
command. This can be used only with the drivers that indicate support
for random local address by setting the new
NL80211_EXT_FEATURE_MGMT_TX_RANDOM_TA and/or
NL80211_EXT_FEATURE_MGMT_TX_RANDOM_TA_CONNECTED in ext_features.

The driver needs to configure receive behavior to accept frames to the
specified random address during the time the frame exchange is pending
and such frames need to be acknowledged similarly to frames sent to the
local permanent address when this random address functionality is not
used.

Signed-off-by: vamsi krishna 
Signed-off-by: Jouni Malinen 
---
 include/uapi/linux/nl80211.h |  6 ++
 net/wireless/mlme.c  | 21 +++--
 2 files changed, 25 insertions(+), 2 deletions(-)

v2:
- remove unnecessary NL80211_ATTR_MGMT_TX_RANDOM_SA and allow address
  change based on the driver capability flag without requiring
  explicit per-frame indication from user space
- rename "SA" to "TA" to be more accurate for the RX/ACK purposes

diff --git a/include/uapi/linux/nl80211.h b/include/uapi/linux/nl80211.h
index 4e8bf28..ebed28e 100644
--- a/include/uapi/linux/nl80211.h
+++ b/include/uapi/linux/nl80211.h
@@ -4727,6 +4727,10 @@ enum nl80211_feature_flags {
  * @NL80211_EXT_FEATURE_SCHED_SCAN_RELATIVE_RSSI: The driver supports 
sched_scan
  * for reporting BSSs with better RSSI than the current connected BSS
  * (%NL80211_ATTR_SCHED_SCAN_RELATIVE_RSSI).
+ * @NL80211_EXT_FEATURE_MGMT_TX_RANDOM_TA: This driver supports randomized TA
+ * in @NL80211_CMD_FRAME while not associated.
+ * @NL80211_EXT_FEATURE_MGMT_TX_RANDOM_TA_CONNECTED: This driver supports
+ * randomized TA in @NL80211_CMD_FRAME while associated.
  *
  * @NUM_NL80211_EXT_FEATURES: number of extended features.
  * @MAX_NL80211_EXT_FEATURES: highest extended feature index.
@@ -4743,6 +4747,8 @@ enum nl80211_ext_feature_index {
NL80211_EXT_FEATURE_BEACON_RATE_VHT,
NL80211_EXT_FEATURE_FILS_STA,
NL80211_EXT_FEATURE_SCHED_SCAN_RELATIVE_RSSI,
+   NL80211_EXT_FEATURE_MGMT_TX_RANDOM_TA,
+   NL80211_EXT_FEATURE_MGMT_TX_RANDOM_TA_CONNECTED,
 
/* add new features before the definition below */
NUM_NL80211_EXT_FEATURES,
diff --git a/net/wireless/mlme.c b/net/wireless/mlme.c
index 1c63a77..b876f40 100644
--- a/net/wireless/mlme.c
+++ b/net/wireless/mlme.c
@@ -662,8 +662,25 @@ int cfg80211_mlme_mgmt_tx(struct 
cfg80211_registered_device *rdev,
return err;
}
 
-   if (!ether_addr_equal(mgmt->sa, wdev_address(wdev)))
-   return -EINVAL;
+   if (!ether_addr_equal(mgmt->sa, wdev_address(wdev))) {
+   /* Allow random TA to be used with Public Action frames if the
+* driver has indicated support for this. Otherwise, only allow
+* the local address to be used.
+*/
+   if (!ieee80211_is_action(mgmt->frame_control) ||
+   mgmt->u.action.category != WLAN_CATEGORY_PUBLIC)
+   return -EINVAL;
+   if (!wdev->current_bss &&
+   !wiphy_ext_feature_isset(
+   >wiphy,
+   NL80211_EXT_FEATURE_MGMT_TX_RANDOM_TA))
+   return -EINVAL;
+   if (wdev->current_bss &&
+   !wiphy_ext_feature_isset(
+   >wiphy,
+   NL80211_EXT_FEATURE_MGMT_TX_RANDOM_TA_CONNECTED))
+   return -EINVAL;
+   }
 
/* Transmit the Action frame as requested by user space */
return rdev_mgmt_tx(rdev, wdev, params, cookie);
-- 
2.7.4