[GitHub/mt8127/android_kernel_alcatel_ttab.git] / Documentation / networking / mac80211-injection.txt

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 many radiotap parameters being currently defined, most only make sense
to appear on received packets.  The following information is parsed from the
radiotap headers and used to control injection:

 * IEEE80211_RADIOTAP_FLAGS

   IEEE80211_RADIOTAP_F_FCS: FCS will be removed and recalculated
   IEEE80211_RADIOTAP_F_WEP: frame will be encrypted if key available
   IEEE80211_RADIOTAP_F_FRAG: frame will be fragmented if longer than the
			      current fragmentation threshold.

 * IEEE80211_RADIOTAP_TX_FLAGS

   IEEE80211_RADIOTAP_F_TX_NOACK: frame should be sent without waiting for
				  an ACK even if it is a unicast frame

The injection code can also skip all other currently defined radiotap fields
facilitating replay of captured radiotap headers directly.

Here is an example valid radiotap header defining some 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 a link to a complete inject application here:

http://wireless.kernel.org/en/users/Documentation/packetspammer

Andy Green <andy@warmcat.com>
Commit	Line	Data
08d1f215 AG	1	How to use packet injection with mac80211
	2	=========================================
	3
	4	mac80211 now allows arbitrary packets to be injected down any Monitor Mode
	5	interface from userland. The packet you inject needs to be composed in the
	6	following format:
	7
	8	[ radiotap header ]
	9	[ ieee80211 header ]
	10	[ payload ]
	11
	12	The radiotap format is discussed in
	13	./Documentation/networking/radiotap-headers.txt.
	14
de2b3e86	15	Despite many radiotap parameters being currently defined, most only make sense
58d4185e JB	16	to appear on received packets. The following information is parsed from the
58d4185e JB	17	radiotap headers and used to control injection:
08d1f215	18
58d4185e JB	19	* IEEE80211_RADIOTAP_FLAGS
	20
	21	IEEE80211_RADIOTAP_F_FCS: FCS will be removed and recalculated
	22	IEEE80211_RADIOTAP_F_WEP: frame will be encrypted if key available
	23	IEEE80211_RADIOTAP_F_FRAG: frame will be fragmented if longer than the
de2b3e86 JB	24	current fragmentation threshold.
de2b3e86 JB	25
d9cd48f9 HS	26	* IEEE80211_RADIOTAP_TX_FLAGS
	27
	28	IEEE80211_RADIOTAP_F_TX_NOACK: frame should be sent without waiting for
	29	an ACK even if it is a unicast frame
58d4185e JB	30
	31	The injection code can also skip all other currently defined radiotap fields
	32	facilitating replay of captured radiotap headers directly.
08d1f215	33
de2b3e86	34	Here is an example valid radiotap header defining some parameters
08d1f215 AG	35
	36	0x00, 0x00, // <-- radiotap version
	37	0x0b, 0x00, // <- radiotap header length
	38	0x04, 0x0c, 0x00, 0x00, // <-- bitmap
	39	0x6c, // <-- rate
	40	0x0c, //<-- tx power
	41	0x01 //<-- antenna
	42
	43	The ieee80211 header follows immediately afterwards, looking for example like
	44	this:
	45
	46	0x08, 0x01, 0x00, 0x00,
	47	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
	48	0x13, 0x22, 0x33, 0x44, 0x55, 0x66,
	49	0x13, 0x22, 0x33, 0x44, 0x55, 0x66,
	50	0x10, 0x86
	51
	52	Then lastly there is the payload.
	53
	54	After composing the packet contents, it is sent by send()-ing it to a logical
	55	mac80211 interface that is in Monitor mode. Libpcap can also be used,
	56	(which is easier than doing the work to bind the socket to the right
	57	interface), along the following lines:
	58
	59	ppcap = pcap_open_live(szInterfaceName, 800, 1, 20, szErrbuf);
	60	...
	61	r = pcap_inject(ppcap, u8aSendBuffer, nLength);
	62
de2b3e86	63	You can also find a link to a complete inject application here:
08d1f215	64
de2b3e86	65	http://wireless.kernel.org/en/users/Documentation/packetspammer
08d1f215 AG	66
08d1f215 AG	67	Andy Green <andy@warmcat.com>