[PATCH] mac80211: Monitor mode radiotap injection docs

Add monitor mode radiotap injection docs.

Signed-off-by: Andy Green <andy@warmcat.com>
Signed-off-by: Jiri Benc <jbenc@suse.cz>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 59 insertions, 0 deletions

diff --git a/Documentation/networking/mac80211-injection.txt b/Documentation/networking/mac80211-injection.txt
new file mode 100644
index 000000000000..53ef7a06f49c
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+++ b/Documentation/networking/mac80211-injection.txt
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+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>