[MAC80211]: allow drivers to indicate failed FCS/PLCP checksum

This patch allows drivers to indicate bad FCS/PLCP CRC to the stack and
have the stack drop packets like that except for monitor interfaces.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Michael Wu <flamingice@sourmilk.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 35 insertions, 3 deletions

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 947f3c820e42..7d9dc20ee42f 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -235,6 +235,10 @@ struct ieee80211_tx_control {
  * @RX_FLAG_IV_STRIPPED: The IV/ICV are stripped from this frame.
  *      If this flag is set, the stack cannot do any replay detection
  *      hence the driver or hardware will have to do that.
+ * @RX_FLAG_FAILED_FCS_CRC: Set this flag if the FCS check failed on
+ *      the frame.
+ * @RX_FLAG_FAILED_PLCP_CRC: Set this flag if the PCLP check failed on
+ *      the frame.
  */
 enum mac80211_rx_flags {
         RX_FLAG_MMIC_ERROR      = 1<<0,
@@ -242,6 +246,8 @@ enum mac80211_rx_flags {
         RX_FLAG_RADIOTAP        = 1<<2,
         RX_FLAG_MMIC_STRIPPED   = 1<<3,
         RX_FLAG_IV_STRIPPED     = 1<<4,
+        RX_FLAG_FAILED_FCS_CRC  = 1<<5,
+        RX_FLAG_FAILED_PLCP_CRC = 1<<6,
 };
 
 /**
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index e9dcc6229c3c..cf2a72f89d68 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -145,6 +145,8 @@ ieee80211_rx_monitor(struct net_device *dev, struct sk_buff *skb,
                 __le16 chan_freq;
                 __le16 chan_flags;
                 u8 antsignal;
+                u8 padding_for_rxflags;
+                __le16 rx_flags;
         } __attribute__ ((packed)) *rthdr;
 
         skb->dev = dev;
@@ -167,12 +169,21 @@ ieee80211_rx_monitor(struct net_device *dev, struct sk_buff *skb,
                 cpu_to_le32((1 << IEEE80211_RADIOTAP_FLAGS) |
                             (1 << IEEE80211_RADIOTAP_RATE) |
                             (1 << IEEE80211_RADIOTAP_CHANNEL) |
-                            (1 << IEEE80211_RADIOTAP_DB_ANTSIGNAL));
+                            (1 << IEEE80211_RADIOTAP_DB_ANTSIGNAL) |
+                            (1 << IEEE80211_RADIOTAP_RX_FLAGS));
         rthdr->flags = local->hw.flags & IEEE80211_HW_RX_INCLUDES_FCS ?
                        IEEE80211_RADIOTAP_F_FCS : 0;
+
+        /* FIXME: when radiotap gets a 'bad PLCP' flag use it here */
+        rthdr->rx_flags = 0;
+        if (status->flag &
+            (RX_FLAG_FAILED_FCS_CRC | RX_FLAG_FAILED_PLCP_CRC))
+                rthdr->rx_flags |= cpu_to_le16(IEEE80211_RADIOTAP_F_RX_BADFCS);
+
         rate = ieee80211_get_rate(local, status->phymode, status->rate);
         if (rate)
                 rthdr->rate = rate->rate / 5;
+
         rthdr->chan_freq = cpu_to_le16(status->freq);
         rthdr->chan_flags =
                 status->phymode == MODE_IEEE80211A ?
@@ -200,6 +211,15 @@ ieee80211_rx_h_monitor(struct ieee80211_txrx_data *rx)
                 return TXRX_QUEUED;
         }
 
+        /*
+         * Drop frames with failed FCS/PLCP checksums here, they are only
+         * relevant for monitor mode, the rest of the stack should never
+         * see them.
+         */
+        if (rx->u.rx.status->flag &
+            (RX_FLAG_FAILED_FCS_CRC | RX_FLAG_FAILED_PLCP_CRC))
+                return TXRX_DROP;
+
         if (rx->u.rx.status->flag & RX_FLAG_RADIOTAP)
                 skb_pull(rx->skb, ieee80211_get_radiotap_len(rx->skb->data));
 
@@ -1360,6 +1380,7 @@ void __ieee80211_rx(struct ieee80211_hw *hw, struct sk_buff *skb,
         struct ieee80211_sub_if_data *prev = NULL;
         struct sk_buff *skb_new;
         u8 *bssid;
+        int bogon;
 
         if (status->flag & RX_FLAG_RADIOTAP) {
                 radiotap_len = ieee80211_get_radiotap_len(skb->data);
@@ -1380,10 +1401,15 @@ void __ieee80211_rx(struct ieee80211_hw *hw, struct sk_buff *skb,
         rx.u.rx.status = status;
         rx.fc = skb->len >= 2 ? le16_to_cpu(hdr->frame_control) : 0;
         type = rx.fc & IEEE80211_FCTL_FTYPE;
-        if (type == IEEE80211_FTYPE_DATA || type == IEEE80211_FTYPE_MGMT)
+
+        bogon = status->flag & (RX_FLAG_FAILED_FCS_CRC |
+                                RX_FLAG_FAILED_PLCP_CRC);
+
+        if (!bogon && (type == IEEE80211_FTYPE_DATA ||
+                       type == IEEE80211_FTYPE_MGMT))
                 local->dot11ReceivedFragmentCount++;
 
-        if (skb->len >= 16) {
+        if (!bogon && skb->len >= 16) {
                 sta = rx.sta = sta_info_get(local, hdr->addr2);
                 if (sta) {
                         rx.dev = rx.sta->dev;