[PATCH 0/5] Try #6: Radiotap on Monitor Mode interfaces for rx and tx

[PATCH 0/5] Try #6: Radiotap on Monitor Mode interfaces for rx and tx

[andy]

Hi folks -

This set of patches change the Monitor Mode wireless interfaces to use radiotap
both for monitoring and for packet injection.  The monitoring side is done by a patch
from Michael Wu.  Tcpdump knows how to handle the result.

For injecting packets, the you issue a packet using libpcap or a SOCK_PACKET
socket down an interface to the wireless device that is in Monitor Mode.  The packet
has a normal radiotap header prepended to the IEEE80211 header.  The radiotap header
is variable length depending on what the user wants to specify, currently the
transmit rate, power and antenna can be specified using normal radiotap semantics.
Any other entries are skipped.

The radiotap parser is broken out into its own file under cfg80211.

A usermode app packetspammer is available from here

http://penumbra.warmcat.com/_twk/tiki-index.php?page=packetspammer

which allows easy injection of these packets from the commandline.  At the moment it
loops issuing packets at a variety of rates which can be seen from another
machine's monitor mode interface on the same channel.  There are instructions for
build and using it on the page above.

Currently it has been tested for both rx and tx using zd1211rw-mac80211.

The patches should be based against yesterday's wireless-dev.

I also added some documentation files which explains how to use the injection
functionality and radiotap header notes.
-- 

[PATCH 1/5] mac80211:Change Radiotap to little-endian (Pavel Roskin)

[andy]

Meddled with by Andy Green since signed-off: made it apply to current
wireless-dev, took out comments for radiotap types not in current wireless-dev

Document that all fields must be little endian.  Use annotated types
even in the comments.  Consistently use shorter type names (u8, s8). 
Realign the comments.

Signed-off-by: Pavel Roskin <proski@gnu.org>
diff --git a/include/net/ieee80211_radiotap.h b/include/net/ieee80211_radiotap.h
index 429b738..7dbf9fb 100644
--- a/include/net/ieee80211_radiotap.h
+++ b/include/net/ieee80211_radiotap.h
@@ -66,7 +66,9 @@
  */
 #define IEEE80211_RADIOTAP_HDRLEN	64
 
-/* The radio capture header precedes the 802.11 header. */
+/* The radio capture header precedes the 802.11 header.
+ * All data in the header is little endian on all platforms.
+ */
 struct ieee80211_radiotap_header {
 	u8 it_version;		/* Version 0. Only increases
 				 * for drastic changes,
@@ -74,12 +76,12 @@ struct ieee80211_radiotap_header {
 				 * new fields does not count.
 				 */
 	u8 it_pad;
-	u16 it_len;		/* length of the whole
+	__le16 it_len;		/* length of the whole
 				 * header in bytes, including
 				 * it_version, it_pad,
 				 * it_len, and data fields.
 				 */
-	u32 it_present;		/* A bitmap telling which
+	__le32 it_present;	/* A bitmap telling which
 				 * fields are present. Set bit 31
 				 * (0x80000000) to extend the
 				 * bitmap by another 32 bits.
@@ -91,84 +93,84 @@ struct ieee80211_radiotap_header {
 /* Name                                 Data type       Units
  * ----                                 ---------       -----
  *
- * IEEE80211_RADIOTAP_TSFT              u64       microseconds
+ * IEEE80211_RADIOTAP_TSFT              __le64          microseconds
  *
  *      Value in microseconds of the MAC's 64-bit 802.11 Time
  *      Synchronization Function timer when the first bit of the
  *      MPDU arrived at the MAC. For received frames, only.
  *
- * IEEE80211_RADIOTAP_CHANNEL           2 x u16   MHz, bitmap
+ * IEEE80211_RADIOTAP_CHANNEL           2 x __le16      MHz, bitmap
  *
  *      Tx/Rx frequency in MHz, followed by flags (see below).
  *
- * IEEE80211_RADIOTAP_FHSS              u16       see below
+ * IEEE80211_RADIOTAP_FHSS              __le16          see below
  *
  *      For frequency-hopping radios, the hop set (first byte)
  *      and pattern (second byte).
  *
- * IEEE80211_RADIOTAP_RATE              u8        500kb/s
+ * IEEE80211_RADIOTAP_RATE              u8              500kb/s
  *
  *      Tx/Rx data rate
  *
- * IEEE80211_RADIOTAP_DBM_ANTSIGNAL     int8_t          decibels from
+ * IEEE80211_RADIOTAP_DBM_ANTSIGNAL     s8              decibels from
  *                                                      one milliwatt (dBm)
  *
  *      RF signal power at the antenna, decibel difference from
  *      one milliwatt.
  *
- * IEEE80211_RADIOTAP_DBM_ANTNOISE      int8_t          decibels from
+ * IEEE80211_RADIOTAP_DBM_ANTNOISE      s8              decibels from
  *                                                      one milliwatt (dBm)
  *
  *      RF noise power at the antenna, decibel difference from one
  *      milliwatt.
  *
- * IEEE80211_RADIOTAP_DB_ANTSIGNAL      u8        decibel (dB)
+ * IEEE80211_RADIOTAP_DB_ANTSIGNAL      u8              decibel (dB)
  *
  *      RF signal power at the antenna, decibel difference from an
  *      arbitrary, fixed reference.
  *
- * IEEE80211_RADIOTAP_DB_ANTNOISE       u8        decibel (dB)
+ * IEEE80211_RADIOTAP_DB_ANTNOISE       u8              decibel (dB)
  *
  *      RF noise power at the antenna, decibel difference from an
  *      arbitrary, fixed reference point.
  *
- * IEEE80211_RADIOTAP_LOCK_QUALITY      u16       unitless
+ * IEEE80211_RADIOTAP_LOCK_QUALITY      __le16          unitless
  *
  *      Quality of Barker code lock. Unitless. Monotonically
  *      nondecreasing with "better" lock strength. Called "Signal
  *      Quality" in datasheets.  (Is there a standard way to measure
  *      this?)
  *
- * IEEE80211_RADIOTAP_TX_ATTENUATION    u16       unitless
+ * IEEE80211_RADIOTAP_TX_ATTENUATION    __le16          unitless
  *
  *      Transmit power expressed as unitless distance from max
  *      power set at factory calibration.  0 is max power.
  *      Monotonically nondecreasing with lower power levels.
  *
- * IEEE80211_RADIOTAP_DB_TX_ATTENUATION u16       decibels (dB)
+ * IEEE80211_RADIOTAP_DB_TX_ATTENUATION __le16          decibels (dB)
  *
  *      Transmit power expressed as decibel distance from max power
  *      set at factory calibration.  0 is max power.  Monotonically
  *      nondecreasing with lower power levels.
  *
- * IEEE80211_RADIOTAP_DBM_TX_POWER      int8_t          decibels from
+ * IEEE80211_RADIOTAP_DBM_TX_POWER      s8              decibels from
  *                                                      one milliwatt (dBm)
  *
  *      Transmit power expressed as dBm (decibels from a 1 milliwatt
  *      reference). This is the absolute power level measured at
  *      the antenna port.
  *
- * IEEE80211_RADIOTAP_FLAGS             u8        bitmap
+ * IEEE80211_RADIOTAP_FLAGS             u8              bitmap
  *
  *      Properties of transmitted and received frames. See flags
  *      defined below.
  *
- * IEEE80211_RADIOTAP_ANTENNA           u8        antenna index
+ * IEEE80211_RADIOTAP_ANTENNA           u8              antenna index
  *
  *      Unitless indication of the Rx/Tx antenna for this packet.
  *      The first antenna is antenna 0.
  *
- * IEEE80211_RADIOTAP_FCS           	u32       data
+ * IEEE80211_RADIOTAP_FCS           	__le32          data
  *
  *	FCS from frame in network byte order.
  */

-- 

[PATCH 2/5] mac80211: Add radiotap support for Monitor mode RX

[andy]

Try #2
 - Fix radiotap bitmap generation (Andy Green)
 - Fix radiotap padding (Michael Wu)

From: Michael Wu <flamingice@sourmilk.net>

---

 include/net/mac80211.h         |    3 ++
 net/mac80211/ieee80211.c       |   67 +++++++++++++++++++++++++++++++++-------
 net/mac80211/ieee80211_iface.c |    2 +
 3 files changed, 59 insertions(+), 13 deletions(-)

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 916b21b..27cffdc 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -518,6 +518,9 @@ struct ieee80211_hw {
 	 * normal operation. */
 #define IEEE80211_HW_MONITOR_DURING_OPER (1<<9)
 
+	/* Driver supports radiotap. */
+#define IEEE80211_HW_RADIOTAP_SUPPORTED (1<<10)
+
 	/* please fill this gap when adding new flags */
 
 	/* calculate Michael MIC for an MSDU when doing hwcrypto */
diff --git a/net/mac80211/ieee80211.c b/net/mac80211/ieee80211.c
index 0b7cb35..6bffc29 100644
--- a/net/mac80211/ieee80211.c
+++ b/net/mac80211/ieee80211.c
@@ -8,6 +8,7 @@
  */
 
 #include <net/mac80211.h>
+#include <net/ieee80211_radiotap.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/netdevice.h>
@@ -286,6 +287,14 @@ int ieee80211_get_hdrlen_from_skb(const struct sk_buff *skb)
 }
 EXPORT_SYMBOL(ieee80211_get_hdrlen_from_skb);
 
+static int ieee80211_get_radiotap_len(struct sk_buff *skb)
+{
+	struct ieee80211_radiotap_header *hdr =
+		(struct ieee80211_radiotap_header *) skb->data;
+
+	return le16_to_cpu(hdr->it_len);
+}
+
 #ifdef CONFIG_MAC80211_LOWTX_FRAME_DUMP
 static void ieee80211_dump_frame(const char *ifname, const char *title,
 				 const struct sk_buff *skb)
@@ -2741,26 +2750,48 @@ ieee80211_rx_monitor(struct net_device *dev, struct sk_buff *skb,
 		     struct ieee80211_rx_status *status)
 {
 	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
-	struct ieee80211_frame_info *fi;
 	struct ieee80211_sub_if_data *sdata;
-	const size_t hlen = sizeof(struct ieee80211_frame_info)
-				- sizeof(fi->msg_type);
+	struct ieee80211_rtap_hdr {
+		struct ieee80211_radiotap_header hdr;
+		u8 flags;
+		u8 rate;
+		__le16 chan_freq;
+		__le16 chan_flags;
+		u8 antsignal;
+	} __attribute__ ((packed)) *rthdr;
 
 	skb->dev = dev;
 
 	sdata = IEEE80211_DEV_TO_SUB_IF(dev);
 
-	if (skb_headroom(skb) < hlen) {
-		I802_DEBUG_INC(local->rx_expand_skb_head);
-		if (pskb_expand_head(skb, hlen, 0, GFP_ATOMIC)) {
-			dev_kfree_skb(skb);
-			return;
+	if (!(local->hw.flags & IEEE80211_HW_RADIOTAP_SUPPORTED)) {
+		if (skb_headroom(skb) < sizeof(*rthdr)) {
+			I802_DEBUG_INC(local->rx_expand_skb_head);
+			if (pskb_expand_head(skb, sizeof(*rthdr), 0, GFP_ATOMIC)) {
+				dev_kfree_skb(skb);
+				return;
+			}
 		}
-	}
 
-	fi = (struct ieee80211_frame_info *) skb_push(skb, hlen);
+		rthdr = (struct ieee80211_rtap_hdr *) skb_push(skb, sizeof(*rthdr));
+		memset(rthdr, 0, sizeof(*rthdr));
+		rthdr->hdr.it_len = cpu_to_le16(sizeof(*rthdr));
+		rthdr->hdr.it_present =
+			cpu_to_le32((1 << IEEE80211_RADIOTAP_FLAGS) |
+				    (1 << IEEE80211_RADIOTAP_RATE) |
+				    (1 << IEEE80211_RADIOTAP_CHANNEL) |
+				    (1 << IEEE80211_RADIOTAP_DB_ANTSIGNAL));
+		rthdr->flags = local->hw.flags & IEEE80211_HW_RX_INCLUDES_FCS ?
+			       IEEE80211_RADIOTAP_F_FCS : 0;
+		rthdr->rate = status->rate / 5;
+		rthdr->chan_freq = cpu_to_le16(status->freq);
+		rthdr->chan_flags =
+			status->phymode == MODE_IEEE80211A ?
+			cpu_to_le16(IEEE80211_CHAN_OFDM | IEEE80211_CHAN_5GHZ) :
+			cpu_to_le16(IEEE80211_CHAN_DYN | IEEE80211_CHAN_2GHZ);
+		rthdr->antsignal = status->ssi;
+	}
 
-	ieee80211_fill_frame_info(local, fi, status);
 	sdata->stats.rx_packets++;
 	sdata->stats.rx_bytes += skb->len;
 
@@ -3164,6 +3195,10 @@ ieee80211_rx_h_monitor(struct ieee80211_txrx_data *rx)
 		return TXRX_QUEUED;
 	}
 
+	if (rx->local->monitors &&
+	    rx->local->hw.flags & IEEE80211_HW_RADIOTAP_SUPPORTED)
+		skb_pull(rx->skb, ieee80211_get_radiotap_len(rx->skb));
+
 	return TXRX_CONTINUE;
 }
 
@@ -3731,6 +3766,13 @@ void __ieee80211_rx(struct ieee80211_hw *hw, struct sk_buff *skb,
 	struct ieee80211_txrx_data rx;
 	u16 type;
 	int multicast;
+	int radiotap_len = 0;
+
+	if (local->monitors &&
+	    local->hw.flags & IEEE80211_HW_RADIOTAP_SUPPORTED) {
+		radiotap_len = ieee80211_get_radiotap_len(skb);
+		skb_pull(skb, radiotap_len);
+	}
 
 	hdr = (struct ieee80211_hdr *) skb->data;
 	memset(&rx, 0, sizeof(rx));
@@ -3767,6 +3809,7 @@ void __ieee80211_rx(struct ieee80211_hw *hw, struct sk_buff *skb,
 		goto end;
 	skb = rx.skb;
 
+	skb_push(skb, radiotap_len);
 	if (sta && !sta->assoc_ap && !(sta->flags & WLAN_STA_WDS) &&
 	    !local->iff_promiscs && !multicast) {
 		rx.u.rx.ra_match = 1;
@@ -3775,7 +3818,7 @@ void __ieee80211_rx(struct ieee80211_hw *hw, struct sk_buff *skb,
 	} else {
 		struct ieee80211_sub_if_data *prev = NULL;
 		struct sk_buff *skb_new;
-		u8 *bssid = ieee80211_get_bssid(hdr, skb->len);
+		u8 *bssid = ieee80211_get_bssid(hdr, skb->len - radiotap_len);
 
 		list_for_each_entry(sdata, &local->sub_if_list, list) {
 			rx.u.rx.ra_match = 1;
diff --git a/net/mac80211/ieee80211_iface.c b/net/mac80211/ieee80211_iface.c
index 3e0b4fa..51197b1 100644
--- a/net/mac80211/ieee80211_iface.c
+++ b/net/mac80211/ieee80211_iface.c
@@ -199,7 +199,7 @@ void ieee80211_if_set_type(struct net_device *dev, int type)
 		break;
 	}
 	case IEEE80211_IF_TYPE_MNTR:
-		dev->type = ARPHRD_IEEE80211_PRISM;
+		dev->type = ARPHRD_IEEE80211_RADIOTAP;
 		break;
 	default:
 		printk(KERN_WARNING "%s: %s: Unknown interface type 0x%x",

-- 

[PATCH 3/5] mac80211: Monitor mode radiotap injection docs

[andy]

From: Andy Green <andy@warmcat.com>


diff --git a/Documentation/networking/mac80211-injection.txt b/Documentation/networking/mac80211-injection.txt
new file mode 100644
index 0000000..53ef7a0
--- /dev/null
+++ b/Documentation/networking/mac80211-injection.txt
@@ -0,0 +1,59 @@
+How to use packet injection with mac80211
+=========================================
+
+mac80211 now allows arbitrary packets to be injected down any Monitor Mode
+interface from userland.  The packet you inject needs to be composed in the
+following format:
+
+ [ radiotap header  ]
+ [ ieee80211 header ]
+ [ payload ]
+
+The radiotap format is discussed in
+./Documentation/networking/radiotap-headers.txt.
+
+Despite 13 radiotap argument types are currently defined, most only make sense
+to appear on received packets.  Currently three kinds of argument are used by
+the injection code, although it knows to skip any other arguments that are
+present (facilitating replay of captured radiotap headers directly):
+
+ - IEEE80211_RADIOTAP_RATE - u8 arg in 500kbps units (0x02 --> 1Mbps)
+
+ - IEEE80211_RADIOTAP_ANTENNA - u8 arg, 0x00 = ant1, 0x01 = ant2
+
+ - IEEE80211_RADIOTAP_DBM_TX_POWER - u8 arg, dBm
+
+Here is an example valid radiotap header defining these three parameters
+
+	0x00, 0x00, // <-- radiotap version
+	0x0b, 0x00, // <- radiotap header length
+	0x04, 0x0c, 0x00, 0x00, // <-- bitmap
+	0x6c, // <-- rate
+	0x0c, //<-- tx power
+	0x01 //<-- antenna
+
+The ieee80211 header follows immediately afterwards, looking for example like
+this:
+
+	0x08, 0x01, 0x00, 0x00,
+	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+	0x13, 0x22, 0x33, 0x44, 0x55, 0x66,
+	0x13, 0x22, 0x33, 0x44, 0x55, 0x66,
+	0x10, 0x86
+
+Then lastly there is the payload.
+
+After composing the packet contents, it is sent by send()-ing it to a logical
+mac80211 interface that is in Monitor mode.  Libpcap can also be used,
+(which is easier than doing the work to bind the socket to the right
+interface), along the following lines:
+
+	ppcap = pcap_open_live(szInterfaceName, 800, 1, 20, szErrbuf);
+...
+	r = pcap_inject(ppcap, u8aSendBuffer, nLength);
+
+You can also find sources for a complete inject test applet here:
+
+http://penumbra.warmcat.com/_twk/tiki-index.php?page=packetspammer
+
+Andy Green <andy@warmcat.com>
diff --git a/Documentation/networking/radiotap-headers.txt b/Documentation/networking/radiotap-headers.txt
new file mode 100644
index 0000000..0d2207a
--- /dev/null
+++ b/Documentation/networking/radiotap-headers.txt
@@ -0,0 +1,79 @@
+How to use radiotap headers
+===========================
+
+Pointer to the radiotap include file
+------------------------------------
+
+Radiotap headers are variable-length and extensible, you can get most of the
+information you need to know on them from:
+
+./include/net/ieee80211_radiotap.h
+
+This document gives an overview and warns on some corner cases.
+
+
+Structure of the header
+-----------------------
+
+There is a fixed portion at the start which contains a u32 bitmap that defines
+if the possible argument associated with that bit is present or not.  So if b0
+of the it_present member of ieee80211_radiotap_header is set, it means that
+the header for argument index 0 (IEEE80211_RADIOTAP_TSFT) is present in the
+argument area.
+
+   < 8-byte ieee80211_radiotap_header >
+   [ <possible argument bitmap extensions ... > ]
+   [ <argument> ... ]
+
+At the moment there are only 13 possible argument indexes defined, but in case
+we run out of space in the u32 it_present member, it is defined that b31 set
+indicates that there is another u32 bitmap following (shown as "possible
+argument bitmap extensions..." above), and the start of the arguments is moved
+forward 4 bytes each time.
+
+Note also that the it_len member __le16 is set to the total number of bytes
+covered by the ieee80211_radiotap_header and any arguments following.
+
+
+Requirements for arguments
+--------------------------
+
+After the fixed part of the header, the arguments follow for each argument
+index whose matching bit is set in the it_present member of
+ieee80211_radiotap_header.
+
+ - the arguments are all stored little-endian!
+
+ - the argument payload for a given argument index has a fixed size.  So
+   IEEE80211_RADIOTAP_TSFT being present always indicates an 8-byte argument is
+   present.  See the comments in ./include/net/ieee80211_radiotap.h for a nice
+   breakdown of all the argument sizes
+
+ - the arguments must be aligned to a boundary of the argument size using
+   padding.  So a u16 argument must start on the next u16 boundary if it isn't
+   already on one, a u32 must start on the next u32 boundary and so on.
+
+ - "alignment" is relative to the start of the ieee80211_radiotap_header, ie,
+   the first byte of the radiotap header.  The absolute alignment of that first
+   byte isn't defined.  So even if the whole radiotap header is starting at, eg,
+   address 0x00000003, still the first byte of the radiotap header is treated as
+   0 for alignment purposes.
+
+ - The arguments for a given argument index can be a compound of multiple types
+   together.  For example IEEE80211_RADIOTAP_CHANNEL has an argument payload
+   consisting of two u16s of total length 4.  When this happens, the padding
+   rule is applied dealing with a u16, NOT dealing with a 4-byte single entity.
+
+
+Example valid radiotap header
+-----------------------------
+
+	0x00, 0x00, // <-- radiotap version + pad byte
+	0x0b, 0x00, // <- radiotap header length
+	0x04, 0x0c, 0x00, 0x00, // <-- bitmap
+	0x6c, // <-- rate (in 500kHz units)
+	0x0c, //<-- tx power
+	0x01 //<-- antenna
+
+
+Andy Green <andy@warmcat.com>

-- 

[PATCH 4/5] cfg80211:Radiotap parser

[andy]

From: Andy Green <andy@warmcat.com>

Try #1
 - Based on Johannes Berg's comments, broke out the radiotap parsing into
   its own file as part of cfg80211
 - From same comments, added mask constant for b31 of arg presence bitfield
   to ieee80211_radiotap.h
 - Fixed subtle but nasty bug with alignment: args in the radiotap area are
   aligned *relative to the start of the header* now.  The header is not
   guaranteed to align to anything (it is randomly in an skb data area).

===================================================

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 47e4544..098d4b6 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -74,6 +74,41 @@ struct key_params {
 	u32 cipher;
 };
 
+
+/* Radiotap header iteration
+ *   implemented in net/wireless/radiotap.c
+ *
+ * call __ieee80211_radiotap_iterator_init() to init the opaque iterator
+ * (no need to init anything in there beforehand)
+ * then loop calling __ieee80211_radiotap_iterator_next()... it returns -1
+ * if there are no more args in the header, or the next argument type index
+ * that is present.  The iterator's this_arg member points to the start of the
+ * argument associated with the current argument type that is present,
+ * which can be found in the iterator's this_arg_index member.
+ */
+
+struct ieee80211_radiotap_iterator {
+	struct ieee80211_radiotap_header *rtheader;
+	int max_length; /* copy of max length we can scan over */
+	int this_arg_index; /* IEEE80211_RADIOTAP_* index for caller */
+	u8 * this_arg; /* current arg start position, caller can change */
+
+	int arg_index; /* internal: arg index b0 of bitmap_shifter represents */
+	u8 * arg; /* internal: points to the next arg start position */
+	__le32 *next_bitmap; /* internal */
+	u32 bitmap_shifter; /* internal */
+};
+
+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;
 
diff --git a/include/net/ieee80211_radiotap.h b/include/net/ieee80211_radiotap.h
index 7dbf9fb..b73c665 100644
--- a/include/net/ieee80211_radiotap.h
+++ b/include/net/ieee80211_radiotap.h
@@ -59,6 +59,9 @@
  * use sufficiently weaselly language ("is a monotonically nondecreasing
  * function of...") that I cannot set false expectations for lawyerly
  * readers.
+ *
+ * All arguments and fields in the struct at the start are
+ * Little-endian
  */
 
 /* XXX tcpdump/libpcap do not tolerate variable-length headers,
@@ -90,6 +93,8 @@ struct ieee80211_radiotap_header {
 				 */
 };
 
+#define IEEE80211_RADIOTAP_PRESENT_EXTEND_MASK 0x80000000
+
 /* Name                                 Data type       Units
  * ----                                 ---------       -----
  *
@@ -230,4 +235,7 @@ enum ieee80211_radiotap_type {
 	(((x) == 14) ? 2484 : ((x) * 5) + 2407) : \
 	((x) + 1000) * 5)
 
-#endif				/* IEEE80211_RADIOTAP_H */
+#endif
+
+
+/* IEEE80211_RADIOTAP_H */
diff --git a/net/wireless/Makefile b/net/wireless/Makefile
index 507a028..26f815a 100644
--- a/net/wireless/Makefile
+++ b/net/wireless/Makefile
@@ -1,6 +1,6 @@
 obj-$(CONFIG_CFG80211) += cfg80211.o
 
-cfg80211-y += core.o sysfs.o
+cfg80211-y += core.o sysfs.o radiotap.o
 cfg80211-$(CONFIG_NL80211) += nl80211.o
 cfg80211-$(CONFIG_CFG80211_WEXT_COMPAT) += wext-compat.o
 
diff --git a/net/wireless/radiotap.c b/net/wireless/radiotap.c
new file mode 100644
index 0000000..2275e8e
--- /dev/null
+++ b/net/wireless/radiotap.c
@@ -0,0 +1,213 @@
+/*
+ * Radiotap parser
+ *
+ * Copyright 2007		Andy Green <andy@warmcat.com>
+ */
+
+#include <linux/if.h>
+#include <linux/err.h>
+#include <linux/mutex.h>
+#include <linux/device.h>
+#include <net/genetlink.h>
+#include <net/cfg80211.h>
+#include <net/wireless.h>
+#include "nl80211.h"
+#include "core.h"
+#include <net/ieee80211_radiotap.h>
+
+
+/**
+ * ieee80211_radiotap_iterator_init - radiotap parser iterator initialization
+ * @iterator: radiotap_iterator to initialize
+ * @radiotap_header: radiotap header to parse
+ * @max_length: total length we can parse into (eg, whole packet length)
+ *
+ * Returns: 0 on success or negative if sanity check fails
+ *
+ * This function initializes an opaque iterator struct which can then
+ * be passed to ieee80211_radiotap_iterator_next() to visit every radiotap
+ * argument which is present in the header.  It knows about extended
+ * present headers and handles them.
+ */
+
+int ieee80211_radiotap_iterator_init(
+   struct ieee80211_radiotap_iterator * iterator,
+   struct ieee80211_radiotap_header * radiotap_header,
+   int max_length)
+{
+
+	/* Linux only supports version 0 radiotap format */
+
+	if (radiotap_header->it_version)
+		return -EINVAL;
+
+	/* sanity check for allowed length and radiotap length field */
+
+	if (max_length < (le16_to_cpu(radiotap_header->it_len)))
+		return -EINVAL;
+
+	iterator->rtheader = radiotap_header;
+	iterator->max_length = le16_to_cpu(radiotap_header->it_len);
+	iterator->arg_index = 0;
+	iterator->bitmap_shifter = le32_to_cpu(radiotap_header->it_present);
+	iterator->arg = ((u8 *)radiotap_header) +
+			sizeof(struct ieee80211_radiotap_header);
+	iterator->this_arg = 0;
+
+	/* find payload start allowing for extended bitmap(s) */
+
+	if (iterator->bitmap_shifter & IEEE80211_RADIOTAP_PRESENT_EXTEND_MASK) {
+		while (le32_to_cpu(*((u32 *)iterator->arg)) &
+		       IEEE80211_RADIOTAP_PRESENT_EXTEND_MASK)
+			iterator->arg += sizeof(u32);
+		iterator->arg += sizeof(u32);
+	}
+
+	/* we are all initialized happily */
+
+	return 0;
+}
+
+EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);
+
+
+/**
+ * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
+ * @iterator: radiotap_iterator to move to next arg (if any)
+ *
+ * Returns: next present arg index on success or negative if no more or error
+ *
+ * This function returns the next radiotap arg index (IEEE80211_RADIOTAP_*)
+ * and sets iterator->this_arg to point to the payload for the arg.  It takes
+ * care of alignment handling and extended present fields.  interator->this_arg
+ * can be changed by the caller.  The args pointed to are in little-endian
+ * format.
+ */
+
+int ieee80211_radiotap_iterator_next(
+   struct ieee80211_radiotap_iterator * iterator)
+{
+
+	/* small length lookup table for all radiotap types we heard of
+	 * starting from b0 in the bitmap, so we can walk the payload
+	 * area of the radiotap header
+	 *
+	 * There is a requirement to pad args, so that args
+	 * of a given length must begin at a boundary of that length
+	 * -- but note that compound args are allowed (eg, 2 x u16
+	 * for IEEE80211_RADIOTAP_CHANNEL) so total arg length is not
+	 * a reliable indicator of alignment requirement.
+	 *
+	 * upper nybble: content alignment for arg
+	 * lower nybble: content length for arg
+	 */
+
+	static const u8 rt_sizes[] = {
+		[IEEE80211_RADIOTAP_TSFT] = 0x88,
+		[IEEE80211_RADIOTAP_FLAGS] = 0x11,
+		[IEEE80211_RADIOTAP_RATE] = 0x11,
+		[IEEE80211_RADIOTAP_CHANNEL] = 0x24,
+		[IEEE80211_RADIOTAP_FHSS] = 0x22,
+		[IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = 0x11,
+		[IEEE80211_RADIOTAP_DBM_ANTNOISE] = 0x11,
+		[IEEE80211_RADIOTAP_LOCK_QUALITY] = 0x22,
+		[IEEE80211_RADIOTAP_TX_ATTENUATION] = 0x22,
+		[IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = 0x22,
+		[IEEE80211_RADIOTAP_DBM_TX_POWER] = 0x11,
+		[IEEE80211_RADIOTAP_ANTENNA] = 0x11,
+		[IEEE80211_RADIOTAP_DB_ANTSIGNAL] = 0x11,
+		[IEEE80211_RADIOTAP_DB_ANTNOISE] = 0x11
+		/* add more here as they are defined in
+		 * include/net/ieee80211_radiotap.h
+		 */
+	};
+
+	/* for every radiotap entry we can at
+	 * least skip (by knowing the length)...
+	 */
+
+	while (iterator->arg_index < sizeof(rt_sizes)) {
+		int hit=0;
+
+		if (!(iterator->bitmap_shifter & 1))
+			goto next_entry; /* arg not present */
+
+		/* arg is present, account for alignment padding
+		 *  8-bit args can be at any alignment
+		 * 16-bit args must start on 16-bit boundary
+		 * 32-bit args must start on 32-bit boundary
+		 * 64-bit args must start on 64-bit boundary
+		 *
+		 * note that total arg size can differ from alignment of
+		 * elements inside arg, so we use upper nybble of length
+		 * table to base alignment on
+		 *
+		 * also note: these alignments are ** relative to the
+		 * start of the radiotap header **.  There is no guarantee
+		 * that the radiotap header itself is aligned on any
+		 * kind of boundary.
+		 */
+
+		if ((((int)iterator->arg)-((int)iterator->rtheader)) &
+		    ((rt_sizes[iterator->arg_index] >> 4) - 1))
+			iterator->arg_index +=
+				(rt_sizes[iterator->arg_index] >> 4) -
+				((((int)iterator->arg) -
+				 ((int)iterator->rtheader)) &
+				 ((rt_sizes[iterator->arg_index] >> 4) - 1));
+
+		/* this is what we will return to user, but we need to
+		 * move on first so next call has something fresh to test
+		 */
+
+		iterator->this_arg_index = iterator->arg_index;
+		iterator->this_arg = iterator->arg;
+		hit = 1;
+
+		/* internally move on the size of this arg */
+
+		iterator->arg += rt_sizes[iterator->arg_index] & 0x0f;
+
+		/* check for insanity where we are given a bitmap that
+		 * claims to have more arg content than the length of the
+		 * radiotap section.  We will normally end up equalling this
+		 * max_length on the last arg, never exceeding it.
+		 */
+
+		if((((int)iterator->arg) - ((int)iterator->rtheader)) >
+		    iterator->max_length)
+			return -EINVAL;
+
+	next_entry:
+
+		iterator->arg_index++;
+		if (unlikely((iterator->arg_index & 31) == 0)) {
+			/* completed current u32 bitmap */
+			if (iterator->bitmap_shifter & 1) {
+				/* b31 was set, there is more */
+				/* move to next u32 bitmap */
+				iterator->bitmap_shifter = le32_to_cpu(
+					*iterator->next_bitmap);
+				iterator->next_bitmap++;
+			} else {
+				/* no more bitmaps: end */
+				iterator->arg_index = sizeof(rt_sizes);
+			}
+		} else { /* just try the next bit */
+			iterator->bitmap_shifter >>= 1;
+		}
+
+		/* if we found a valid arg earlier, return it now */
+
+		if (hit)
+			return iterator->this_arg_index;
+
+	}
+
+	/* we don't know how to handle any more args, we're done */
+
+	return -1;
+}
+
+EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);
+

-- 

[PATCH 5/5] mac80211: Monitor mode radiotap-based packet injection

[andy]

From: Andy Green <andy@warmcat.com>

Try #6
 - Accounted for various comments from Johannes Berg
 - Radiotap parsing is moved to cfg80211 as requested in a separate patch

Try #5
 - De-indent last few indented comments

Try #4
 - All from Michael Wu's feedback: further style heresies removed
 - took account of radiotap arg alignment requirement.  n-byte arg must be
   placed on n-byte boundary using padding where necessary

Try #3
 - moved to Michael Wu's method of tracking if we came in on a
   monitor interface by using ifindex
 - removed older proposed monitor interface tracking method and flags
 - style fixes
 - removed duped #include that is present in Michael Wu's patch already

Try #2
 - took Michael Wu's advice about better tools and basing on wireless-dev
 - took Luis Rodriguez's advice about coding style makeover
 - took Pavel Roskin's advice about little-endian radiotap

===================================================

diff --git a/net/mac80211/ieee80211.c b/net/mac80211/ieee80211.c
index e6a0a0e..95b041e 100644
--- a/net/mac80211/ieee80211.c
+++ b/net/mac80211/ieee80211.c
@@ -1070,7 +1070,111 @@ ieee80211_tx_h_ps_buf(struct ieee80211_txrx_data *tx)
 }
 
 
-static void inline
+/* deal with packet injection down monitor interface
+ * with Radiotap Header -- only called for monitor mode interface
+ */
+
+static ieee80211_txrx_result
+__ieee80211_convert_radiotap_to_control_and_remove(
+	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 *hw_mode=tx->local->hw.conf.mode;
+
+	/* this can fail some sanity checks, drop packet if it does so */
+
+	if (ieee80211_radiotap_iterator_init(&iterator, rthdr, skb->len) < 0)
+		return TXRX_DROP;
+
+	/* 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 (returns -ve on end or
+	 * on error)
+	 */
+
+	while (ieee80211_radiotap_iterator_next(&iterator) >= 0) {
+		int i, target_rate;
+
+		/* 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 < hw_mode->num_rates; i++) {
+				struct ieee80211_rate *r = &hw_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 = hw_mode->num_rates;
+
+			}
+			break;
+
+		case IEEE80211_RADIOTAP_ANTENNA:
+			/* radiotap uses 0 for 1st ant,
+			 * mac80211 is 1 for 1st ant
+			 * absence of IEEE80211_RADIOTAP_ANTENNA
+			 * gives default/diversity
+			 */
+			control->antenna_sel_tx = (*iterator.this_arg) + 1;
+			break;
+
+		case IEEE80211_RADIOTAP_DBM_TX_POWER:
+			control->power_level = *iterator.this_arg;
+			break;
+
+		default:
+			break;
+		}
+
+	}
+
+	/* remove the radiotap header
+	 * rthdr->it_len was sanity-checked against skb->len by iterator init
+	 */
+	skb_pull(skb, le16_to_cpu(rthdr->it_len));
+
+	return TXRX_CONTINUE;
+}
+
+
+static ieee80211_txrx_result inline
 __ieee80211_tx_prepare(struct ieee80211_txrx_data *tx,
 		       struct sk_buff *skb,
 		       struct net_device *dev,
@@ -1078,6 +1182,9 @@ __ieee80211_tx_prepare(struct ieee80211_txrx_data *tx,
 {
 	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));
@@ -1087,7 +1194,32 @@ __ieee80211_tx_prepare(struct ieee80211_txrx_data *tx,
 	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_convert_radiotap_to_control_and_remove(
+		    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))
@@ -1104,9 +1236,6 @@ __ieee80211_tx_prepare(struct ieee80211_txrx_data *tx,
 		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)];
@@ -1114,6 +1243,7 @@ __ieee80211_tx_prepare(struct ieee80211_txrx_data *tx,
 	}
 	control->flags |= IEEE80211_TXCTL_FIRST_FRAGMENT;
 
+	return res;
 }
 
 static int inline is_ieee80211_device(struct net_device *dev,
@@ -1221,7 +1351,7 @@ static int ieee80211_tx(struct net_device *dev, struct sk_buff *skb,
 	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));
@@ -1231,15 +1361,26 @@ static int ieee80211_tx(struct net_device *dev, struct sk_buff *skb,
 		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 */
@@ -1473,6 +1614,51 @@ static int ieee80211_subif_start_xmit(struct sk_buff *skb,
 		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(struct ieee80211_tx_packet_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->mac.raw = skb->data+prthdr->it_len;
+		skb->nh.raw = skb->data+prthdr->it_len+
+			sizeof(struct ieee80211_hdr);
+		skb->h.raw = skb->data+prthdr->it_len+
+			sizeof(struct ieee80211_hdr);
+
+		/* pass the radiotap header up to
+		 * the next stage intact
+		 */
+
+		dev_queue_xmit(skb);
+
+		return 0;
+	}
+
 	nh_pos = skb->nh.raw - skb->data;
 	h_pos = skb->h.raw - skb->data;
 

--