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>

1 files changed, 30 insertions, 5 deletions

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) {