mac80211: support scan features for improved scan privacy

Support the new random SN and minimal probe request contents
scan flags for the case of software scan - for hardware scan
the drivers need to opt in, but may need to do only that,
depending on their implementation.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>

9 files changed, 71 insertions, 24 deletions

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index bdf6fa78d0d2..c4e2f7d2bcb8 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -3486,7 +3486,7 @@ static int ieee80211_probe_client(struct wiphy *wiphy, struct net_device *dev,
         }
 
         local_bh_disable();
-        ieee80211_xmit(sdata, sta, skb);
+        ieee80211_xmit(sdata, sta, skb, 0);
         local_bh_enable();
 
         ret = 0;
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 2851245c569a..a6c12c104c38 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -165,6 +165,7 @@ typedef unsigned __bitwise ieee80211_tx_result;
 #define TX_DROP         ((__force ieee80211_tx_result) 1u)
 #define TX_QUEUED       ((__force ieee80211_tx_result) 2u)
 
+#define IEEE80211_TX_NO_SEQNO           BIT(0)
 #define IEEE80211_TX_UNICAST            BIT(1)
 #define IEEE80211_TX_PS_BUFFERED        BIT(2)
 
@@ -1880,19 +1881,20 @@ void ieee80211_regulatory_limit_wmm_params(struct ieee80211_sub_if_data *sdata,
 void ieee80211_set_wmm_default(struct ieee80211_sub_if_data *sdata,
                                bool bss_notify, bool enable_qos);
 void ieee80211_xmit(struct ieee80211_sub_if_data *sdata,
-                    struct sta_info *sta, struct sk_buff *skb);
+                    struct sta_info *sta, struct sk_buff *skb,
+                    u32 txdata_flags);
 
 void __ieee80211_tx_skb_tid_band(struct ieee80211_sub_if_data *sdata,
                                  struct sk_buff *skb, int tid,
-                                 enum nl80211_band band);
+                                 enum nl80211_band band, u32 txdata_flags);
 
 static inline void
 ieee80211_tx_skb_tid_band(struct ieee80211_sub_if_data *sdata,
                           struct sk_buff *skb, int tid,
-                          enum nl80211_band band)
+                          enum nl80211_band band, u32 txdata_flags)
 {
         rcu_read_lock();
-        __ieee80211_tx_skb_tid_band(sdata, skb, tid, band);
+        __ieee80211_tx_skb_tid_band(sdata, skb, tid, band, txdata_flags);
         rcu_read_unlock();
 }
 
@@ -1910,7 +1912,7 @@ static inline void ieee80211_tx_skb_tid(struct ieee80211_sub_if_data *sdata,
         }
 
         __ieee80211_tx_skb_tid_band(sdata, skb, tid,
-                                    chanctx_conf->def.chan->band);
+                                    chanctx_conf->def.chan->band, 0);
         rcu_read_unlock();
 }
 
@@ -2034,6 +2036,8 @@ void ieee80211_send_deauth_disassoc(struct ieee80211_sub_if_data *sdata,
 
 enum {
         IEEE80211_PROBE_FLAG_DIRECTED           = BIT(0),
+        IEEE80211_PROBE_FLAG_MIN_CONTENT        = BIT(1),
+        IEEE80211_PROBE_FLAG_RANDOM_SN          = BIT(2),
 };
 
 int ieee80211_build_preq_ies(struct ieee80211_local *local, u8 *buffer,
diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index 4d2e797e3f16..a6f8e3a646d4 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -557,10 +557,19 @@ struct ieee80211_hw *ieee80211_alloc_hw_nm(size_t priv_data_len,
         wiphy_ext_feature_set(wiphy,
                               NL80211_EXT_FEATURE_CONTROL_PORT_OVER_NL80211);
 
-        if (!ops->hw_scan)
+        if (!ops->hw_scan) {
                 wiphy->features |= NL80211_FEATURE_LOW_PRIORITY_SCAN |
                                    NL80211_FEATURE_AP_SCAN;
-
+                /*
+                 * if the driver behaves correctly using the probe request
+                 * (template) from mac80211, then both of these should be
+                 * supported even with hw scan - but let drivers opt in.
+                 */
+                wiphy_ext_feature_set(wiphy,
+                                      NL80211_EXT_FEATURE_SCAN_RANDOM_SN);
+                wiphy_ext_feature_set(wiphy,
+                                      NL80211_EXT_FEATURE_SCAN_MIN_PREQ_CONTENT);
+        }
 
         if (!ops->set_key)
                 wiphy->flags |= WIPHY_FLAG_IBSS_RSN;
diff --git a/net/mac80211/offchannel.c b/net/mac80211/offchannel.c
index f1d40b6645ff..8ef4153cd299 100644
--- a/net/mac80211/offchannel.c
+++ b/net/mac80211/offchannel.c
@@ -262,7 +262,7 @@ static void ieee80211_handle_roc_started(struct ieee80211_roc_work *roc,
         if (roc->mgmt_tx_cookie) {
                 if (!WARN_ON(!roc->frame)) {
                         ieee80211_tx_skb_tid_band(roc->sdata, roc->frame, 7,
-                                                  roc->chan->band);
+                                                  roc->chan->band, 0);
                         roc->frame = NULL;
                 }
         } else {
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 0a38cc1cbebc..756ba176db1e 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -3241,7 +3241,7 @@ ieee80211_rx_h_action_return(struct ieee80211_rx_data *rx)
                 }
 
                 __ieee80211_tx_skb_tid_band(rx->sdata, nskb, 7,
-                                            status->band);
+                                            status->band, 0);
         }
         dev_kfree_skb(rx->skb);
         return RX_QUEUED;
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index 03f66f31c5b4..ae77d1c12856 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -20,6 +20,7 @@
 #include <net/sch_generic.h>
 #include <linux/slab.h>
 #include <linux/export.h>
+#include <linux/random.h>
 #include <net/mac80211.h>
 
 #include "ieee80211_i.h"
@@ -293,6 +294,7 @@ static bool ieee80211_prep_hw_scan(struct ieee80211_local *local)
         struct cfg80211_chan_def chandef;
         u8 bands_used = 0;
         int i, ielen, n_chans;
+        u32 flags = 0;
 
         req = rcu_dereference_protected(local->scan_req,
                                         lockdep_is_held(&local->mtx));
@@ -331,12 +333,16 @@ static bool ieee80211_prep_hw_scan(struct ieee80211_local *local)
         local->hw_scan_req->req.n_channels = n_chans;
         ieee80211_prepare_scan_chandef(&chandef, req->scan_width);
 
+        if (req->flags & NL80211_SCAN_FLAG_MIN_PREQ_CONTENT)
+                flags |= IEEE80211_PROBE_FLAG_MIN_CONTENT;
+
         ielen = ieee80211_build_preq_ies(local,
                                          (u8 *)local->hw_scan_req->req.ie,
                                          local->hw_scan_ies_bufsize,
                                          &local->hw_scan_req->ies,
                                          req->ie, req->ie_len,
-                                         bands_used, req->rates, &chandef, 0);
+                                         bands_used, req->rates, &chandef,
+                                         flags);
         local->hw_scan_req->req.ie_len = ielen;
         local->hw_scan_req->req.no_cck = req->no_cck;
         ether_addr_copy(local->hw_scan_req->req.mac_addr, req->mac_addr);
@@ -536,13 +542,24 @@ static void ieee80211_send_scan_probe_req(struct ieee80211_sub_if_data *sdata,
                                           struct ieee80211_channel *channel)
 {
         struct sk_buff *skb;
+        u32 txdata_flags = 0;
 
         skb = ieee80211_build_probe_req(sdata, src, dst, ratemask, channel,
                                         ssid, ssid_len,
                                         ie, ie_len, flags);
+
         if (skb) {
+                if (flags & IEEE80211_PROBE_FLAG_RANDOM_SN) {
+                        struct ieee80211_hdr *hdr = (void *)skb->data;
+                        u16 sn = get_random_u32();
+
+                        txdata_flags |= IEEE80211_TX_NO_SEQNO;
+                        hdr->seq_ctrl =
+                                cpu_to_le16(IEEE80211_SN_TO_SEQ(sn));
+                }
                 IEEE80211_SKB_CB(skb)->flags |= tx_flags;
-                ieee80211_tx_skb_tid_band(sdata, skb, 7, channel->band);
+                ieee80211_tx_skb_tid_band(sdata, skb, 7, channel->band,
+                                          txdata_flags);
         }
 }
 
@@ -553,7 +570,7 @@ static void ieee80211_scan_state_send_probe(struct ieee80211_local *local,
         struct ieee80211_sub_if_data *sdata;
         struct cfg80211_scan_request *scan_req;
         enum nl80211_band band = local->hw.conf.chandef.chan->band;
-        u32 tx_flags;
+        u32 flags = 0, tx_flags;
 
         scan_req = rcu_dereference_protected(local->scan_req,
                                              lockdep_is_held(&local->mtx));
@@ -561,6 +578,10 @@ static void ieee80211_scan_state_send_probe(struct ieee80211_local *local,
         tx_flags = IEEE80211_TX_INTFL_OFFCHAN_TX_OK;
         if (scan_req->no_cck)
                 tx_flags |= IEEE80211_TX_CTL_NO_CCK_RATE;
+        if (scan_req->flags & NL80211_SCAN_FLAG_MIN_PREQ_CONTENT)
+                flags |= IEEE80211_PROBE_FLAG_MIN_CONTENT;
+        if (scan_req->flags & NL80211_SCAN_FLAG_RANDOM_SN)
+                flags |= IEEE80211_PROBE_FLAG_RANDOM_SN;
 
         sdata = rcu_dereference_protected(local->scan_sdata,
                                           lockdep_is_held(&local->mtx));
@@ -570,7 +591,7 @@ static void ieee80211_scan_state_send_probe(struct ieee80211_local *local,
                         sdata, local->scan_addr, scan_req->bssid,
                         scan_req->ssids[i].ssid, scan_req->ssids[i].ssid_len,
                         scan_req->ie, scan_req->ie_len,
-                        scan_req->rates[band], 0,
+                        scan_req->rates[band], flags,
                         tx_flags, local->hw.conf.chandef.chan);
 
         /*
@@ -1159,6 +1180,7 @@ int __ieee80211_request_sched_scan_start(struct ieee80211_sub_if_data *sdata,
         u32 rate_masks[NUM_NL80211_BANDS] = {};
         u8 bands_used = 0;
         u8 *ie;
+        u32 flags = 0;
 
         iebufsz = local->scan_ies_len + req->ie_len;
 
@@ -1175,6 +1197,9 @@ int __ieee80211_request_sched_scan_start(struct ieee80211_sub_if_data *sdata,
                 }
         }
 
+        if (req->flags & NL80211_SCAN_FLAG_MIN_PREQ_CONTENT)
+                flags |= IEEE80211_PROBE_FLAG_MIN_CONTENT;
+
         ie = kzalloc(num_bands * iebufsz, GFP_KERNEL);
         if (!ie) {
                 ret = -ENOMEM;
@@ -1186,7 +1211,7 @@ int __ieee80211_request_sched_scan_start(struct ieee80211_sub_if_data *sdata,
         ieee80211_build_preq_ies(local, ie, num_bands * iebufsz,
                                  &sched_scan_ies, req->ie,
                                  req->ie_len, bands_used, rate_masks, &chandef,
-                                 0);
+                                 flags);
 
         ret = drv_sched_scan_start(local, sdata, req, &sched_scan_ies);
         if (ret == 0) {
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 6428f1ac37b6..aa96fddfbfc2 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -1391,7 +1391,7 @@ static void ieee80211_send_null_response(struct sta_info *sta, int tid,
         }
 
         info->band = chanctx_conf->def.chan->band;
-        ieee80211_xmit(sdata, sta, skb);
+        ieee80211_xmit(sdata, sta, skb, 0);
         rcu_read_unlock();
 }
 
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 44b5dfe8727d..5b93bde248fd 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -825,6 +825,8 @@ ieee80211_tx_h_sequence(struct ieee80211_tx_data *tx)
          */
         if (!ieee80211_is_data_qos(hdr->frame_control) ||
             is_multicast_ether_addr(hdr->addr1)) {
+                if (tx->flags & IEEE80211_TX_NO_SEQNO)
+                        return TX_CONTINUE;
                 /* driver should assign sequence number */
                 info->flags |= IEEE80211_TX_CTL_ASSIGN_SEQ;
                 /* for pure STA mode without beacons, we can do it */
@@ -1854,7 +1856,7 @@ EXPORT_SYMBOL(ieee80211_tx_prepare_skb);
  */
 static bool ieee80211_tx(struct ieee80211_sub_if_data *sdata,
                          struct sta_info *sta, struct sk_buff *skb,
-                         bool txpending)
+                         bool txpending, u32 txdata_flags)
 {
         struct ieee80211_local *local = sdata->local;
         struct ieee80211_tx_data tx;
@@ -1872,6 +1874,8 @@ static bool ieee80211_tx(struct ieee80211_sub_if_data *sdata,
         led_len = skb->len;
         res_prepare = ieee80211_tx_prepare(sdata, &tx, sta, skb);
 
+        tx.flags |= txdata_flags;
+
         if (unlikely(res_prepare == TX_DROP)) {
                 ieee80211_free_txskb(&local->hw, skb);
                 return true;
@@ -1933,7 +1937,8 @@ static int ieee80211_skb_resize(struct ieee80211_sub_if_data *sdata,
 }
 
 void ieee80211_xmit(struct ieee80211_sub_if_data *sdata,
-                    struct sta_info *sta, struct sk_buff *skb)
+                    struct sta_info *sta, struct sk_buff *skb,
+                    u32 txdata_flags)
 {
         struct ieee80211_local *local = sdata->local;
         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
@@ -1968,7 +1973,7 @@ void ieee80211_xmit(struct ieee80211_sub_if_data *sdata,
         }
 
         ieee80211_set_qos_hdr(sdata, skb);
-        ieee80211_tx(sdata, sta, skb, false);
+        ieee80211_tx(sdata, sta, skb, false, txdata_flags);
 }
 
 static bool ieee80211_parse_tx_radiotap(struct ieee80211_local *local,
@@ -2289,7 +2294,7 @@ netdev_tx_t ieee80211_monitor_start_xmit(struct sk_buff *skb,
         if (!ieee80211_parse_tx_radiotap(local, skb))
                 goto fail_rcu;
 
-        ieee80211_xmit(sdata, NULL, skb);
+        ieee80211_xmit(sdata, NULL, skb, 0);
         rcu_read_unlock();
 
         return NETDEV_TX_OK;
@@ -3648,7 +3653,7 @@ void __ieee80211_subif_start_xmit(struct sk_buff *skb,
 
                 ieee80211_tx_stats(dev, skb->len);
 
-                ieee80211_xmit(sdata, sta, skb);
+                ieee80211_xmit(sdata, sta, skb, 0);
         }
         goto out;
  out_free:
@@ -3867,7 +3872,7 @@ static bool ieee80211_tx_pending_skb(struct ieee80211_local *local,
                         return true;
                 }
                 info->band = chanctx_conf->def.chan->band;
-                result = ieee80211_tx(sdata, NULL, skb, true);
+                result = ieee80211_tx(sdata, NULL, skb, true, 0);
         } else {
                 struct sk_buff_head skbs;
 
@@ -4783,7 +4788,7 @@ EXPORT_SYMBOL(ieee80211_unreserve_tid);
 
 void __ieee80211_tx_skb_tid_band(struct ieee80211_sub_if_data *sdata,
                                  struct sk_buff *skb, int tid,
-                                 enum nl80211_band band)
+                                 enum nl80211_band band, u32 txdata_flags)
 {
         int ac = ieee80211_ac_from_tid(tid);
 
@@ -4800,7 +4805,7 @@ void __ieee80211_tx_skb_tid_band(struct ieee80211_sub_if_data *sdata,
          */
         local_bh_disable();
         IEEE80211_SKB_CB(skb)->band = band;
-        ieee80211_xmit(sdata, NULL, skb);
+        ieee80211_xmit(sdata, NULL, skb, txdata_flags);
         local_bh_enable();
 }
 
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 0325133552ad..b744b10465c3 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -1433,6 +1433,9 @@ static int ieee80211_build_preq_ies_band(struct ieee80211_local *local,
                                 chandef->chan->center_freq);
         }
 
+        if (flags & IEEE80211_PROBE_FLAG_MIN_CONTENT)
+                goto done;
+
         /* insert custom IEs that go before HT */
         if (ie && ie_len) {
                 static const u8 before_ht[] = {
@@ -1510,6 +1513,7 @@ static int ieee80211_build_preq_ies_band(struct ieee80211_local *local,
         return pos - buffer;
  out_err:
         WARN_ONCE(1, "not enough space for preq IEs\n");
+ done:
         return pos - buffer;
 }