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) {