mac80211: support radiotap vendor namespace RX data

In some cases, in particular for experimentation, it
can be useful to be able to add vendor namespace data
to received frames in addition to the normal radiotap
data.

Allow doing this through mac80211 by adding fields to
the RX status descriptor that describe the data while
the data itself is prepended to the frame.

Also add some example code to hwsim, but don't enable
it because it doesn't use a proper OUI identifier.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/mac80211_hwsim.c

@@ -751,7 +751,11 @@ static bool mac80211_hwsim_tx_frame_no_nl(struct ieee80211_hw *hw,
 				continue;
 		}
 
-		nskb = skb_copy(skb, GFP_ATOMIC);
+		/*
+		 * reserve some space for our vendor and the normal
+		 * radiotap header, since we're copying anyway
+		 */
+		nskb = skb_copy_expand(skb, 64, 0, GFP_ATOMIC);
 		if (nskb == NULL)
 			continue;
 
@@ -769,6 +773,33 @@ static bool mac80211_hwsim_tx_frame_no_nl(struct ieee80211_hw *hw,
 				(data->tsf_offset - data2->tsf_offset) +
 				24 * 8 * 10 / txrate->bitrate);
 
+#if 0
+		/*
+		 * Don't enable this code by default as the OUI 00:00:00
+		 * is registered to Xerox so we shouldn't use it here, it
+		 * might find its way into pcap files.
+		 * Note that this code requires the headroom in the SKB
+		 * that was allocated earlier.
+		 */
+		rx_status.vendor_radiotap_oui[0] = 0x00;
+		rx_status.vendor_radiotap_oui[1] = 0x00;
+		rx_status.vendor_radiotap_oui[2] = 0x00;
+		rx_status.vendor_radiotap_subns = 127;
+		/*
+		 * Radiotap vendor namespaces can (and should) also be
+		 * split into fields by using the standard radiotap
+		 * presence bitmap mechanism. Use just BIT(0) here for
+		 * the presence bitmap.
+		 */
+		rx_status.vendor_radiotap_bitmap = BIT(0);
+		/* We have 8 bytes of (dummy) data */
+		rx_status.vendor_radiotap_len = 8;
+		/* For testing, also require it to be aligned */
+		rx_status.vendor_radiotap_align = 8;
+		/* push the data */
+		memcpy(skb_push(nskb, 8), "ABCDEFGH", 8);
+#endif
+
 		memcpy(IEEE80211_SKB_RXCB(nskb), &rx_status, sizeof(rx_status));
 		ieee80211_rx_irqsafe(data2->hw, nskb);
 	}

include/net/mac80211.h

@@ -789,12 +789,21 @@ enum mac80211_rx_flags {
  * @ampdu_reference: A-MPDU reference number, must be a different value for
  *	each A-MPDU but the same for each subframe within one A-MPDU
  * @ampdu_delimiter_crc: A-MPDU delimiter CRC
+ * @vendor_radiotap_bitmap: radiotap vendor namespace presence bitmap
+ * @vendor_radiotap_len: radiotap vendor namespace length
+ * @vendor_radiotap_align: radiotap vendor namespace alignment. Note
+ *	that the actual data must be at the start of the SKB data
+ *	already.
+ * @vendor_radiotap_oui: radiotap vendor namespace OUI
+ * @vendor_radiotap_subns: radiotap vendor sub namespace
  */
 struct ieee80211_rx_status {
 	u64 mactime;
 	u32 device_timestamp;
 	u32 ampdu_reference;
 	u32 flag;
+	u32 vendor_radiotap_bitmap;
+	u16 vendor_radiotap_len;
 	u16 freq;
 	u8 rate_idx;
 	u8 rx_flags;
@@ -802,6 +811,9 @@ struct ieee80211_rx_status {
 	u8 antenna;
 	s8 signal;
 	u8 ampdu_delimiter_crc;
+	u8 vendor_radiotap_align;
+	u8 vendor_radiotap_oui[3];
+	u8 vendor_radiotap_subns;
 };
 
 /**

net/mac80211/rx.c

@@ -40,6 +40,8 @@
 static struct sk_buff *remove_monitor_info(struct ieee80211_local *local,
 					   struct sk_buff *skb)
 {
+	struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
+
 	if (local->hw.flags & IEEE80211_HW_RX_INCLUDES_FCS) {
 		if (likely(skb->len > FCS_LEN))
 			__pskb_trim(skb, skb->len - FCS_LEN);
@@ -51,6 +53,9 @@ static struct sk_buff *remove_monitor_info(struct ieee80211_local *local,
 		}
 	}
 
+	if (status->vendor_radiotap_len)
+		__pskb_pull(skb, status->vendor_radiotap_len);
+
 	return skb;
 }
 
@@ -73,32 +78,48 @@ static inline int should_drop_frame(struct sk_buff *skb, int present_fcs_len)
 }
 
 static int
-ieee80211_rx_radiotap_len(struct ieee80211_local *local,
-			  struct ieee80211_rx_status *status)
+ieee80211_rx_radiotap_space(struct ieee80211_local *local,
+			    struct ieee80211_rx_status *status)
 {
 	int len;
 
 	/* always present fields */
 	len = sizeof(struct ieee80211_radiotap_header) + 9;
 
-	if (ieee80211_have_rx_timestamp(status))
+	/* allocate extra bitmap */
+	if (status->vendor_radiotap_len)
+		len += 4;
+
+	if (ieee80211_have_rx_timestamp(status)) {
+		len = ALIGN(len, 8);
 		len += 8;
+	}
 	if (local->hw.flags & IEEE80211_HW_SIGNAL_DBM)
 		len += 1;
 
-	if (len & 1) /* padding for RX_FLAGS if necessary */
-		len++;
+	/* padding for RX_FLAGS if necessary */
+	len = ALIGN(len, 2);
 
 	if (status->flag & RX_FLAG_HT) /* HT info */
 		len += 3;
 
 	if (status->flag & RX_FLAG_AMPDU_DETAILS) {
-		/* padding */
-		while (len & 3)
-			len++;
+		len = ALIGN(len, 4);
 		len += 8;
 	}
 
+	if (status->vendor_radiotap_len) {
+		if (WARN_ON_ONCE(status->vendor_radiotap_align == 0))
+			status->vendor_radiotap_align = 1;
+		/* align standard part of vendor namespace */
+		len = ALIGN(len, 2);
+		/* allocate standard part of vendor namespace */
+		len += 6;
+		/* align vendor-defined part */
+		len = ALIGN(len, status->vendor_radiotap_align);
+		/* vendor-defined part is already in skb */
+	}
+
 	return len;
 }
 
@@ -132,14 +153,25 @@ ieee80211_add_rx_radiotap_header(struct ieee80211_local *local,
 			    (1 << IEEE80211_RADIOTAP_CHANNEL) |
 			    (1 << IEEE80211_RADIOTAP_ANTENNA) |
 			    (1 << IEEE80211_RADIOTAP_RX_FLAGS));
-	rthdr->it_len = cpu_to_le16(rtap_len);
+	rthdr->it_len = cpu_to_le16(rtap_len + status->vendor_radiotap_len);
 
 	pos = (unsigned char *)(rthdr + 1);
 
+	if (status->vendor_radiotap_len) {
+		rthdr->it_present |=
+			cpu_to_le32(BIT(IEEE80211_RADIOTAP_VENDOR_NAMESPACE)) |
+			cpu_to_le32(BIT(IEEE80211_RADIOTAP_EXT));
+		put_unaligned_le32(status->vendor_radiotap_bitmap, pos);
+		pos += 4;
+	}
+
 	/* the order of the following fields is important */
 
 	/* IEEE80211_RADIOTAP_TSFT */
 	if (ieee80211_have_rx_timestamp(status)) {
+		/* padding */
+		while ((pos - (u8 *)rthdr) & 7)
+			*pos++ = 0;
 		put_unaligned_le64(
 			ieee80211_calculate_rx_timestamp(local, status,
 							 mpdulen, 0),
@@ -211,7 +243,7 @@ ieee80211_add_rx_radiotap_header(struct ieee80211_local *local,
 	/* IEEE80211_RADIOTAP_RX_FLAGS */
 	/* ensure 2 byte alignment for the 2 byte field as required */
 	if ((pos - (u8 *)rthdr) & 1)
-		pos++;
+		*pos++ = 0;
 	if (status->flag & RX_FLAG_FAILED_PLCP_CRC)
 		rx_flags |= IEEE80211_RADIOTAP_F_RX_BADPLCP;
 	put_unaligned_le16(rx_flags, pos);
@@ -261,6 +293,21 @@ ieee80211_add_rx_radiotap_header(struct ieee80211_local *local,
 			*pos++ = 0;
 		*pos++ = 0;
 	}
+
+	if (status->vendor_radiotap_len) {
+		/* ensure 2 byte alignment for the vendor field as required */
+		if ((pos - (u8 *)rthdr) & 1)
+			*pos++ = 0;
+		*pos++ = status->vendor_radiotap_oui[0];
+		*pos++ = status->vendor_radiotap_oui[1];
+		*pos++ = status->vendor_radiotap_oui[2];
+		*pos++ = status->vendor_radiotap_subns;
+		put_unaligned_le16(status->vendor_radiotap_len, pos);
+		pos += 2;
+		/* align the actual payload as requested */
+		while ((pos - (u8 *)rthdr) & (status->vendor_radiotap_align - 1))
+			*pos++ = 0;
+	}
 }
 
 /*
@@ -289,7 +336,7 @@ ieee80211_rx_monitor(struct ieee80211_local *local, struct sk_buff *origskb,
 	 */
 
 	/* room for the radiotap header based on driver features */
-	needed_headroom = ieee80211_rx_radiotap_len(local, status);
+	needed_headroom = ieee80211_rx_radiotap_space(local, status);
 
 	if (local->hw.flags & IEEE80211_HW_RX_INCLUDES_FCS)
 		present_fcs_len = FCS_LEN;
@@ -2593,7 +2640,7 @@ static void ieee80211_rx_cooked_monitor(struct ieee80211_rx_data *rx,
 		goto out_free_skb;
 
 	/* room for the radiotap header based on driver features */
-	needed_headroom = ieee80211_rx_radiotap_len(local, status);
+	needed_headroom = ieee80211_rx_radiotap_space(local, status);
 
 	if (skb_headroom(skb) < needed_headroom &&
 	    pskb_expand_head(skb, needed_headroom, 0, GFP_ATOMIC))