cfg80211: allow drivers to support random MAC addresses for scan

Add the necessary feature flags and a scan flag to support using
random MAC addresses for scan while unassociated.

The configuration for this supports an arbitrary MAC address
value and mask, so that any kind of configuration (e.g. fixed
OUI or full 46-bit random) can be requested. Full 46-bit random
is the default when no other configuration is passed.

Also add a small helper function to use the addr/mask correctly.

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

1 files changed, 83 insertions, 3 deletions

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 3ec7dc5..dd5a827 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -395,6 +395,7 @@ static const struct nla_policy nl80211_policy[NUM_NL80211_ATTR] = {
 	[NL80211_ATTR_USER_PRIO] = { .type = NLA_U8 },
 	[NL80211_ATTR_ADMITTED_TIME] = { .type = NLA_U16 },
 	[NL80211_ATTR_SMPS_MODE] = { .type = NLA_U8 },
+	[NL80211_ATTR_MAC_MASK] = { .len = ETH_ALEN },
 };
 
 /* policy for the key attributes */
@@ -5481,6 +5482,43 @@ static int validate_scan_freqs(struct nlattr *freqs)
 	return n_channels;
 }
 
+static int nl80211_parse_random_mac(struct nlattr **attrs,
+				    u8 *mac_addr, u8 *mac_addr_mask)
+{
+	int i;
+
+	if (!attrs[NL80211_ATTR_MAC] && !attrs[NL80211_ATTR_MAC_MASK]) {
+		memset(mac_addr, 0, ETH_ALEN);
+		memset(mac_addr_mask, 0, ETH_ALEN);
+		mac_addr[0] = 0x2;
+		mac_addr_mask[0] = 0x3;
+
+		return 0;
+	}
+
+	/* need both or none */
+	if (!attrs[NL80211_ATTR_MAC] || !attrs[NL80211_ATTR_MAC_MASK])
+		return -EINVAL;
+
+	memcpy(mac_addr, nla_data(attrs[NL80211_ATTR_MAC]), ETH_ALEN);
+	memcpy(mac_addr_mask, nla_data(attrs[NL80211_ATTR_MAC_MASK]), ETH_ALEN);
+
+	/* don't allow or configure an mcast address */
+	if (!is_multicast_ether_addr(mac_addr_mask) ||
+	    is_multicast_ether_addr(mac_addr))
+		return -EINVAL;
+
+	/*
+	 * allow users to pass a MAC address that has bits set outside
+	 * of the mask, but don't bother drivers with having to deal
+	 * with such bits
+	 */
+	for (i = 0; i < ETH_ALEN; i++)
+		mac_addr[i] &= mac_addr_mask[i];
+
+	return 0;
+}
+
 static int nl80211_trigger_scan(struct sk_buff *skb, struct genl_info *info)
 {
 	struct cfg80211_registered_device *rdev = info->user_ptr[0];
@@ -5658,6 +5696,25 @@ static int nl80211_trigger_scan(struct sk_buff *skb, struct genl_info *info)
 			err = -EOPNOTSUPP;
 			goto out_free;
 		}
+
+		if (request->flags & NL80211_SCAN_FLAG_RANDOM_ADDR) {
+			if (!(wiphy->features &
+					NL80211_FEATURE_SCAN_RANDOM_MAC_ADDR)) {
+				err = -EOPNOTSUPP;
+				goto out_free;
+			}
+
+			if (wdev->current_bss) {
+				err = -EOPNOTSUPP;
+				goto out_free;
+			}
+
+			err = nl80211_parse_random_mac(info->attrs,
+						       request->mac_addr,
+						       request->mac_addr_mask);
+			if (err)
+				goto out_free;
+		}
 	}
 
 	request->no_cck =
@@ -5685,7 +5742,7 @@ static int nl80211_trigger_scan(struct sk_buff *skb, struct genl_info *info)
 }
 
 static struct cfg80211_sched_scan_request *
-nl80211_parse_sched_scan(struct wiphy *wiphy,
+nl80211_parse_sched_scan(struct wiphy *wiphy, struct wireless_dev *wdev,
 			 struct nlattr **attrs)
 {
 	struct cfg80211_sched_scan_request *request;
@@ -5934,6 +5991,28 @@ nl80211_parse_sched_scan(struct wiphy *wiphy,
 			err = -EOPNOTSUPP;
 			goto out_free;
 		}
+
+		if (request->flags & NL80211_SCAN_FLAG_RANDOM_ADDR) {
+			u32 flg = NL80211_FEATURE_SCHED_SCAN_RANDOM_MAC_ADDR;
+
+			if (!wdev) /* must be net-detect */
+				flg = NL80211_FEATURE_ND_RANDOM_MAC_ADDR;
+
+			if (!(wiphy->features & flg)) {
+				err = -EOPNOTSUPP;
+				goto out_free;
+			}
+
+			if (wdev && wdev->current_bss) {
+				err = -EOPNOTSUPP;
+				goto out_free;
+			}
+
+			err = nl80211_parse_random_mac(attrs, request->mac_addr,
+						       request->mac_addr_mask);
+			if (err)
+				goto out_free;
+		}
 	}
 
 	request->interval = interval;
@@ -5951,6 +6030,7 @@ static int nl80211_start_sched_scan(struct sk_buff *skb,
 {
 	struct cfg80211_registered_device *rdev = info->user_ptr[0];
 	struct net_device *dev = info->user_ptr[1];
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
 	int err;
 
 	if (!(rdev->wiphy.flags & WIPHY_FLAG_SUPPORTS_SCHED_SCAN) ||
@@ -5960,7 +6040,7 @@ static int nl80211_start_sched_scan(struct sk_buff *skb,
 	if (rdev->sched_scan_req)
 		return -EINPROGRESS;
 
-	rdev->sched_scan_req = nl80211_parse_sched_scan(&rdev->wiphy,
+	rdev->sched_scan_req = nl80211_parse_sched_scan(&rdev->wiphy, wdev,
 							info->attrs);
 	err = PTR_ERR_OR_ZERO(rdev->sched_scan_req);
 	if (err)
@@ -8721,7 +8801,7 @@ static int nl80211_parse_wowlan_nd(struct cfg80211_registered_device *rdev,
 	if (err)
 		goto out;
 
-	trig->nd_config = nl80211_parse_sched_scan(&rdev->wiphy, tb);
+	trig->nd_config = nl80211_parse_sched_scan(&rdev->wiphy, NULL, tb);
 	err = PTR_ERR_OR_ZERO(trig->nd_config);
 	if (err)
 		trig->nd_config = NULL;