mirror of
https://github.com/torvalds/linux.git
synced 2024-12-04 18:13:04 +00:00
5c05803a3e
Not the internal flags but the radiotap flags are parsed when the monitor
injected frames are prepared for transmission. Thus the documentation
should only document these.
Reported-by: Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>
Reported-by: Johannes Berg <johannes@sipsolutions.net>
Fixes: dfdfc2beb0 ("mac80211: Parse legacy and HT rate in injected frames")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
98 lines
3.0 KiB
Plaintext
98 lines
3.0 KiB
Plaintext
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
|
|
|
|
* IEEE80211_RADIOTAP_RATE
|
|
|
|
legacy rate for the transmission (only for devices without own rate control)
|
|
|
|
* IEEE80211_RADIOTAP_MCS
|
|
|
|
HT rate for the transmission (only for devices without own rate control).
|
|
Also some flags are parsed
|
|
|
|
IEEE80211_RADIOTAP_MCS_SGI: use short guard interval
|
|
IEEE80211_RADIOTAP_MCS_BW_40: send in HT40 mode
|
|
|
|
* IEEE80211_RADIOTAP_DATA_RETRIES
|
|
|
|
number of retries when either IEEE80211_RADIOTAP_RATE or
|
|
IEEE80211_RADIOTAP_MCS was used
|
|
|
|
* IEEE80211_RADIOTAP_VHT
|
|
|
|
VHT mcs and number of streams used in the transmission (only for devices
|
|
without own rate control). Also other fields are parsed
|
|
|
|
flags field
|
|
IEEE80211_RADIOTAP_VHT_FLAG_SGI: use short guard interval
|
|
|
|
bandwidth field
|
|
1: send using 40MHz channel width
|
|
4: send using 80MHz channel width
|
|
11: send using 160MHz channel width
|
|
|
|
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>
|