3 files changed, 66 insertions, 14 deletions

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index b1d18d967d8c..38c980612518 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -308,6 +308,8 @@ struct ieee80211_if_managed {
         int auth_alg; /* currently used IEEE 802.11 authentication algorithm */
         int auth_transaction;
 
+        u32 beacon_crc;
+
         enum {
                 IEEE80211_MFP_DISABLED,
                 IEEE80211_MFP_OPTIONAL,
@@ -1085,6 +1087,9 @@ void ieee80211_tx_skb(struct ieee80211_sub_if_data *sdata, struct sk_buff *skb,
                       int encrypt);
 void ieee802_11_parse_elems(u8 *start, size_t len,
                             struct ieee802_11_elems *elems);
+u32 ieee802_11_parse_elems_crc(u8 *start, size_t len,
+                               struct ieee802_11_elems *elems,
+                               u64 filter, u32 crc);
 int ieee80211_set_freq(struct ieee80211_sub_if_data *sdata, int freq);
 u32 ieee80211_mandatory_rates(struct ieee80211_local *local,
                               enum ieee80211_band band);
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index c39a214e7ad0..7a8d4c494246 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -18,6 +18,7 @@
 #include <linux/etherdevice.h>
 #include <linux/rtnetlink.h>
 #include <linux/pm_qos_params.h>
+#include <linux/crc32.h>
 #include <net/mac80211.h>
 #include <asm/unaligned.h>
 
@@ -1752,46 +1753,73 @@ static void ieee80211_rx_mgmt_probe_resp(struct ieee80211_sub_if_data *sdata,
                 ifmgd->flags &= ~IEEE80211_STA_PROBEREQ_POLL;
 }
 
+/*
+ * This is the canonical list of information elements we care about,
+ * the filter code also gives us all changes to the Microsoft OUI
+ * (00:50:F2) vendor IE which is used for WMM which we need to track.
+ *
+ * We implement beacon filtering in software since that means we can
+ * avoid processing the frame here and in cfg80211, and userspace
+ * will not be able to tell whether the hardware supports it or not.
+ *
+ * XXX: This list needs to be dynamic -- userspace needs to be able to
+ *      add items it requires. It also needs to be able to tell us to
+ *      look out for other vendor IEs.
+ */
+static const u64 care_about_ies =
+        BIT(WLAN_EID_COUNTRY) |
+        BIT(WLAN_EID_ERP_INFO) |
+        BIT(WLAN_EID_CHANNEL_SWITCH) |
+        BIT(WLAN_EID_PWR_CONSTRAINT) |
+        BIT(WLAN_EID_HT_CAPABILITY) |
+        BIT(WLAN_EID_HT_INFORMATION);
+
 static void ieee80211_rx_mgmt_beacon(struct ieee80211_sub_if_data *sdata,
                                      struct ieee80211_mgmt *mgmt,
                                      size_t len,
                                      struct ieee80211_rx_status *rx_status)
 {
-        struct ieee80211_if_managed *ifmgd;
+        struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
         size_t baselen;
         struct ieee802_11_elems elems;
         struct ieee80211_local *local = sdata->local;
         u32 changed = 0;
-        bool erp_valid, directed_tim;
+        bool erp_valid, directed_tim = false;
         u8 erp_value = 0;
+        u32 ncrc;
 
         /* Process beacon from the current BSS */
         baselen = (u8 *) mgmt->u.beacon.variable - (u8 *) mgmt;
         if (baselen > len)
                 return;
 
-        ieee802_11_parse_elems(mgmt->u.beacon.variable, len - baselen, &elems);
-
-        ieee80211_rx_bss_info(sdata, mgmt, len, rx_status, &elems, true);
-
-        if (sdata->vif.type != NL80211_IFTYPE_STATION)
+        if (rx_status->freq != local->hw.conf.channel->center_freq)
                 return;
 
-        ifmgd = &sdata->u.mgd;
-
         if (!(ifmgd->flags & IEEE80211_STA_ASSOCIATED) ||
             memcmp(ifmgd->bssid, mgmt->bssid, ETH_ALEN) != 0)
                 return;
 
-        if (rx_status->freq != local->hw.conf.channel->center_freq)
+        ncrc = crc32_be(0, (void *)&mgmt->u.beacon.beacon_int, 4);
+        ncrc = ieee802_11_parse_elems_crc(mgmt->u.beacon.variable,
+                                          len - baselen, &elems,
+                                          care_about_ies, ncrc);
+
+        if (local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK)
+                directed_tim = ieee80211_check_tim(&elems, ifmgd->aid);
+
+        ncrc = crc32_be(ncrc, (void *)&directed_tim, sizeof(directed_tim));
+
+        if (ncrc == ifmgd->beacon_crc)
                 return;
+        ifmgd->beacon_crc = ncrc;
+
+        ieee80211_rx_bss_info(sdata, mgmt, len, rx_status, &elems, true);
 
         ieee80211_sta_wmm_params(local, ifmgd, elems.wmm_param,
                                  elems.wmm_param_len);
 
         if (local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK) {
-                directed_tim = ieee80211_check_tim(&elems, ifmgd->aid);
-
                 if (directed_tim) {
                         if (local->hw.conf.dynamic_ps_timeout > 0) {
                                 local->hw.conf.flags &= ~IEEE80211_CONF_PS;
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index b361e2acfce9..3dd490fa4b68 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -20,6 +20,7 @@
 #include <linux/if_arp.h>
 #include <linux/wireless.h>
 #include <linux/bitmap.h>
+#include <linux/crc32.h>
 #include <net/net_namespace.h>
 #include <net/cfg80211.h>
 #include <net/rtnetlink.h>
@@ -537,8 +538,16 @@ EXPORT_SYMBOL_GPL(ieee80211_iterate_active_interfaces_atomic);
 void ieee802_11_parse_elems(u8 *start, size_t len,
                             struct ieee802_11_elems *elems)
 {
+        ieee802_11_parse_elems_crc(start, len, elems, 0, 0);
+}
+
+u32 ieee802_11_parse_elems_crc(u8 *start, size_t len,
+                               struct ieee802_11_elems *elems,
+                               u64 filter, u32 crc)
+{
         size_t left = len;
         u8 *pos = start;
+        bool calc_crc = filter != 0;
 
         memset(elems, 0, sizeof(*elems));
         elems->ie_start = start;
@@ -552,7 +561,10 @@ void ieee802_11_parse_elems(u8 *start, size_t len,
                 left -= 2;
 
                 if (elen > left)
-                        return;
+                        break;
+
+                if (calc_crc && id < 64 && (filter & BIT(id)))
+                        crc = crc32_be(crc, pos - 2, elen + 2);
 
                 switch (id) {
                 case WLAN_EID_SSID:
@@ -587,15 +599,20 @@ void ieee802_11_parse_elems(u8 *start, size_t len,
                         elems->challenge = pos;
                         elems->challenge_len = elen;
                         break;
-                case WLAN_EID_WPA:
+                case WLAN_EID_VENDOR_SPECIFIC:
                         if (elen >= 4 && pos[0] == 0x00 && pos[1] == 0x50 &&
                             pos[2] == 0xf2) {
                                 /* Microsoft OUI (00:50:F2) */
+
+                                if (calc_crc)
+                                        crc = crc32_be(crc, pos - 2, elen + 2);
+
                                 if (pos[3] == 1) {
                                         /* OUI Type 1 - WPA IE */
                                         elems->wpa = pos;
                                         elems->wpa_len = elen;
                                 } else if (elen >= 5 && pos[3] == 2) {
+                                        /* OUI Type 2 - WMM IE */
                                         if (pos[4] == 0) {
                                                 elems->wmm_info = pos;
                                                 elems->wmm_info_len = elen;
@@ -680,6 +697,8 @@ void ieee802_11_parse_elems(u8 *start, size_t len,
                 left -= elen;
                 pos += elen;
         }
+
+        return crc;
 }
 
 void ieee80211_set_wmm_default(struct ieee80211_sub_if_data *sdata)