Radiotap injection for Monitor Mode

Index: wireless-dev/include/net/cfg80211.h
===================================================================
@@ -74,6 +74,44 @@ struct key_params {
 	u32 cipher;
 };
 
+
+/* Radiotap header iteration
+ *   implemented in net/wireless/radiotap.c
+ *   docs in Documentation/networking/radiotap-headers.txt
+ */
+/**
+ * struct ieee80211_radiotap_iterator - tracks walk thru present radiotap args
+ * @rtheader: pointer to the radiotap header we are walking through
+ * @max_length: length of radiotap header in cpu byte ordering
+ * @this_arg_index: IEEE80211_RADIOTAP_... index of current arg
+ * @this_arg: pointer to current radiotap arg
+ * @arg_index: internal next argument index
+ * @arg: internal next argument pointer
+ * @next_bitmap: internal pointer to next present u32
+ * @bitmap_shifter: internal shifter for curr u32 bitmap, b0 set == arg present
+ */
+
+struct ieee80211_radiotap_iterator {
+	struct ieee80211_radiotap_header *rtheader;
+	int max_length;
+	int this_arg_index;
+	u8 *this_arg;
+
+	int arg_index;
+	u8 *arg;
+	__le32 *next_bitmap;
+	u32 bitmap_shifter;
+};
+
+extern int ieee80211_radiotap_iterator_init(
+   struct ieee80211_radiotap_iterator *iterator,
+   struct ieee80211_radiotap_header *radiotap_header,
+   int max_length);
+
+extern int ieee80211_radiotap_iterator_next(
+   struct ieee80211_radiotap_iterator *iterator);
+
+
 /* from net/wireless.h */
 struct wiphy;
 

243 lines not on this page · raw message

Index: wireless-dev/net/mac80211/ieee80211.c
===================================================================
@@ -1118,7 +1118,132 @@ ieee80211_tx_h_ps_buf(struct ieee80211_t
 }
 
 
-static void inline
+/*
+ * deal with packet injection down monitor interface
+ * with Radiotap Header -- only called for monitor mode interface
+ */
+
+static ieee80211_txrx_result
+__ieee80211_parse_tx_radiotap(
+	struct ieee80211_txrx_data *tx,
+	struct sk_buff *skb, struct ieee80211_tx_control *control)
+{
+	/*
+	 * this is the moment to interpret and discard the radiotap header that
+	 * must be at the start of the packet injected in Monitor mode
+	 *
+	 * Need to take some care with endian-ness since radiotap
+	 * args are little-endian
+	 */
+
+	struct ieee80211_radiotap_iterator iterator;
+	struct ieee80211_radiotap_header *rthdr =
+		(struct ieee80211_radiotap_header *) skb->data;
+	struct ieee80211_hw_mode *mode = tx->local->hw.conf.mode;
+	int ret = ieee80211_radiotap_iterator_init(&iterator, rthdr, skb->len);
+
+	/*
+	 * default control situation for all injected packets
+	 * FIXME: this does not suit all usage cases, expand to allow control
+	 */
+
+	control->retry_limit = 1; /* no retry */
+	control->key_idx = -1; /* no encryption key */
+	control->flags &= ~(IEEE80211_TXCTL_USE_RTS_CTS |
+			    IEEE80211_TXCTL_USE_CTS_PROTECT);
+	control->flags |= IEEE80211_TXCTL_DO_NOT_ENCRYPT |
+			  IEEE80211_TXCTL_NO_ACK;
+	control->antenna_sel_tx = 0; /* default to default antenna */
+
+	/*
+	 * for every radiotap entry that is present
+	 * (ieee80211_radiotap_iterator_next returns -ENOENT when no more
+	 * entries present, or -EINVAL on error)
+	 */
+
+	while (!ret) {
+		int i, target_rate;
+
+	 	ret = ieee80211_radiotap_iterator_next(&iterator);
+
+		if (ret)
+			continue;
+
+		/* see if this argument is something we can use */
+		switch (iterator.this_arg_index) {
+		case IEEE80211_RADIOTAP_RATE:
+			/*
+			 * radiotap rate u8 is in 500kbps units eg, 0x02=1Mbps
+			 * ieee80211 rate int is in 100kbps units eg, 0x0a=1Mbps
+			 */
+			target_rate = (*iterator.this_arg) * 5;
+			for (i = 0; i < mode->num_rates; i++) {
+				struct ieee80211_rate *r = &mode->rates[i];
+
+				if (r->rate > target_rate)
+					continue;
+
+				control->rate = r;
+
+				if (r->flags & IEEE80211_RATE_PREAMBLE2)
+					control->tx_rate = r->val2;
+				else
+					control->tx_rate = r->val;
+
+				/* end on exact match */
+				if (r->rate == target_rate)
+					i = mode->num_rates;
+			}
+			break;
+
+		case IEEE80211_RADIOTAP_ANTENNA:
+			/*
+			 * radiotap uses 0 for 1st ant, mac80211 is 1 for
+			 * 1st ant
+			 */
+			control->antenna_sel_tx = (*iterator.this_arg) + 1;
+			break;
+
+		case IEEE80211_RADIOTAP_DBM_TX_POWER:
+			control->power_level = *iterator.this_arg;
+			break;
+
+		case IEEE80211_RADIOTAP_FLAGS:
+			if (*iterator.this_arg & IEEE80211_RADIOTAP_F_FCS) {
+				/*
+				 * this indicates that the skb we have been
+				 * handed has the 32-bit FCS CRC at the end...
+				 * we should react to that by snipping it off
+				 * because it will be recomputed and added
+				 * on transmission
+				 */
+				if (skb->len < (iterator.max_length + FCS_LEN))
+					return TXRX_DROP;
+
+				skb_trim(skb, skb->len - FCS_LEN);
+			}
+			break;
+
+		default:
+			break;
+		}
+	}
+
+	if (ret != -ENOENT) /* ie, if we didn't simply run out of fields */
+		return TXRX_DROP;
+
+	/*
+	 * remove the radiotap header
+	 * iterator->max_length was sanity-checked against
+	 * skb->len by iterator init
+	 */
+	skb_pull(skb, iterator.max_length);
+
+	return TXRX_CONTINUE;
+}
+
+
+static ieee80211_txrx_result inline
 __ieee80211_tx_prepare(struct ieee80211_txrx_data *tx,
 		       struct sk_buff *skb,
 		       struct net_device *dev,

@@ -1126,6 +1251,9 @@ __ieee80211_tx_prepare(struct ieee80211_
 {
 	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
+	struct ieee80211_sub_if_data *sdata;
+	ieee80211_txrx_result res = TXRX_CONTINUE;
+
 	int hdrlen;
 
 	memset(tx, 0, sizeof(*tx));

@@ -1135,7 +1263,32 @@ __ieee80211_tx_prepare(struct ieee80211_
 	tx->sdata = IEEE80211_DEV_TO_SUB_IF(dev);
 	tx->sta = sta_info_get(local, hdr->addr1);
 	tx->fc = le16_to_cpu(hdr->frame_control);
+
+	/*
+	 * set defaults for things that can be set by
+	 * injected radiotap headers
+	 */
 	control->power_level = local->hw.conf.power_level;
+	control->antenna_sel_tx = local->hw.conf.antenna_sel_tx;
+	if (local->sta_antenna_sel != STA_ANTENNA_SEL_AUTO && tx->sta)
+		control->antenna_sel_tx = tx->sta->antenna_sel_tx;
+
+	/* process and remove the injection radiotap header */
+	sdata = IEEE80211_DEV_TO_SUB_IF(dev);
+	if (unlikely(sdata->type == IEEE80211_IF_TYPE_MNTR)) {
+		if (__ieee80211_parse_tx_radiotap(tx, skb, control) ==
+								TXRX_DROP) {
+			return TXRX_DROP;
+		}
+		/*
+		 * we removed the radiotap header after this point,
+		 * we filled control with what we could use
+		 * set to the actual ieee header now
+		 */
+		hdr = (struct ieee80211_hdr *) skb->data;
+		res = TXRX_QUEUED; /* indication it was monitor packet */
+	}
+
 	tx->u.tx.control = control;
 	tx->u.tx.unicast = !is_multicast_ether_addr(hdr->addr1);
 	if (is_multicast_ether_addr(hdr->addr1))

@@ -1152,9 +1305,6 @@ __ieee80211_tx_prepare(struct ieee80211_
 		control->flags |= IEEE80211_TXCTL_CLEAR_DST_MASK;
 		tx->sta->clear_dst_mask = 0;
 	}
-	control->antenna_sel_tx = local->hw.conf.antenna_sel_tx;
-	if (local->sta_antenna_sel != STA_ANTENNA_SEL_AUTO && tx->sta)
-		control->antenna_sel_tx = tx->sta->antenna_sel_tx;
 	hdrlen = ieee80211_get_hdrlen(tx->fc);
 	if (skb->len > hdrlen + sizeof(rfc1042_header) + 2) {
 		u8 *pos = &skb->data[hdrlen + sizeof(rfc1042_header)];

@@ -1162,6 +1312,7 @@ __ieee80211_tx_prepare(struct ieee80211_
 	}
 	control->flags |= IEEE80211_TXCTL_FIRST_FRAGMENT;
 
+	return res;
 }
 
 static int inline is_ieee80211_device(struct net_device *dev,

@@ -1274,7 +1425,7 @@ static int ieee80211_tx(struct net_devic
 	struct sta_info *sta;
 	ieee80211_tx_handler *handler;
 	struct ieee80211_txrx_data tx;
-	ieee80211_txrx_result res = TXRX_DROP;
+	ieee80211_txrx_result res = TXRX_DROP, res_prepare;
 	int ret, i;
 
 	WARN_ON(__ieee80211_queue_pending(local, control->queue));

@@ -1284,15 +1435,26 @@ static int ieee80211_tx(struct net_devic
 		return 0;
 	}
 
-	__ieee80211_tx_prepare(&tx, skb, dev, control);
+	res_prepare = __ieee80211_tx_prepare(&tx, skb, dev, control);
+
+	if (res_prepare == TXRX_DROP) {
+		dev_kfree_skb(skb);
+		return 0;
+	}
+
 	sta = tx.sta;
 	tx.u.tx.mgmt_interface = mgmt;
 	tx.u.tx.mode = local->hw.conf.mode;
 
-	for (handler = local->tx_handlers; *handler != NULL; handler++) {
-		res = (*handler)(&tx);
-		if (res != TXRX_CONTINUE)
-			break;
+	if (res_prepare == TXRX_QUEUED) { /* if it was an injected packet */
+		res = TXRX_CONTINUE;
+	} else {
+		for (handler = local->tx_handlers; *handler != NULL;
+		     handler++) {
+			res = (*handler)(&tx);
+			if (res != TXRX_CONTINUE)
+				break;
+		}
 	}
 
 	skb = tx.skb; /* handlers are allowed to change skb */

@@ -1531,6 +1693,49 @@ static int ieee80211_subif_start_xmit(st
 		goto fail;
 	}
 
+	if (unlikely(sdata->type == IEEE80211_IF_TYPE_MNTR)) {
+		struct ieee80211_radiotap_header * prthdr =
+			(struct ieee80211_radiotap_header *)skb->data;
+
+		/*
+		 * there must be a radiotap header at the
+		 * start in this case
+		 */
+		if (unlikely(prthdr->it_version)) {
+			/* only version 0 is supported  */
+			ret = 0;
+			goto fail;
+		}
+
+		skb->dev = local->mdev;
+
+		pkt_data = (struct ieee80211_tx_packet_data *)skb->cb;
+		memset(pkt_data, 0, sizeof(*pkt_data));
+		pkt_data->ifindex = sdata->dev->ifindex;
+		pkt_data->mgmt_iface = 0;
+		pkt_data->do_not_encrypt = 1;
+
+		/* above needed because we set skb device to master */
+
+		/*
+		 * fix up the pointers accounting for the radiotap
+		 * header still being in there.  We are being given
+		 * a precooked IEEE80211 header so no need for
+		 * normal processing
+		 */
+		skb_set_mac_header(skb, prthdr->it_len);
+		skb_set_network_header(skb, prthdr->it_len + sizeof(hdr));
+		skb_set_transport_header(skb, prthdr->it_len + sizeof(hdr));
+
+		/*
+		 * pass the radiotap header up to
+		 * the next stage intact
+		 */
+		dev_queue_xmit(skb);
+
+		return 0;
+	}
+
 	nh_pos = skb_network_header(skb) - skb->data;
 	h_pos = skb_transport_header(skb) - skb->data;
 

index 5f2bf3e..023aa18 100644
@@ -1164,7 +1164,7 @@ __ieee80211_parse_tx_radiotap(
 	while (!ret) {
 		int i, target_rate;
 
-	 	ret = ieee80211_radiotap_iterator_next(&iterator);
+		ret = ieee80211_radiotap_iterator_next(&iterator);
 
 		if (ret)
 			continue;

@@ -1694,8 +1694,9 @@ static int ieee80211_subif_start_xmit(struct sk_buff *skb,
 	}
 
 	if (unlikely(sdata->type == IEEE80211_IF_TYPE_MNTR)) {
-		struct ieee80211_radiotap_header * prthdr =
+		struct ieee80211_radiotap_header *prthdr =
 			(struct ieee80211_radiotap_header *)skb->data;
+		u16 len;
 
 		/*
 		 * there must be a radiotap header at the

@@ -1723,9 +1724,10 @@ static int ieee80211_subif_start_xmit(struct sk_buff *skb,
 		 * a precooked IEEE80211 header so no need for
 		 * normal processing
 		 */
-		skb_set_mac_header(skb, prthdr->it_len);
-		skb_set_network_header(skb, prthdr->it_len + sizeof(hdr));
-		skb_set_transport_header(skb, prthdr->it_len + sizeof(hdr));
+		len = le16_to_cpu(prthdr->it_len);
+		skb_set_mac_header(skb, len);
+		skb_set_network_header(skb, len + sizeof(hdr));
+		skb_set_transport_header(skb, len + sizeof(hdr));
 
 		/*
 		 * pass the radiotap header up to

index 1b4a7be..091f234 100644
@@ -60,12 +60,12 @@ int ieee80211_radiotap_iterator_init(
 	iterator->arg_index = 0;
 	iterator->bitmap_shifter = le32_to_cpu(radiotap_header->it_present);
 	iterator->arg = (u8 *)radiotap_header + sizeof(*radiotap_header);
-	iterator->this_arg = 0;
+	iterator->this_arg = NULL;
 
 	/* find payload start allowing for extended bitmap(s) */
 
 	if (unlikely(iterator->bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT))) {
-		while (le32_to_cpu(*(u32 *)iterator->arg) &
+		while (le32_to_cpu(*(__le32 *)iterator->arg) &
 				   (1<<IEEE80211_RADIOTAP_EXT)) {
 			iterator->arg += sizeof(u32);
 

@@ -93,7 +93,6 @@ int ieee80211_radiotap_iterator_init(
 
 	return 0;
 }
-
 EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);
 
 

@@ -239,5 +238,4 @@ int ieee80211_radiotap_iterator_next(
 	/* we don't know how to handle any more args, we're done */
 	return -ENOENT;
 }
-
 EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);