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 |
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. |
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 | 30 | |
dfdfc2be SE |
31 | * IEEE80211_RADIOTAP_RATE |
32 | ||
33 | legacy rate for the transmission (only for devices without own rate control) | |
34 | ||
35 | * IEEE80211_RADIOTAP_MCS | |
36 | ||
37 | HT rate for the transmission (only for devices without own rate control). | |
38 | Also some flags are parsed | |
39 | ||
40 | IEEE80211_TX_RC_SHORT_GI: use short guard interval | |
41 | IEEE80211_TX_RC_40_MHZ_WIDTH: send in HT40 mode | |
42 | ||
43 | * IEEE80211_RADIOTAP_DATA_RETRIES | |
44 | ||
45 | number of retries when either IEEE80211_RADIOTAP_RATE or | |
46 | IEEE80211_RADIOTAP_MCS was used | |
47 | ||
58d4185e JB |
48 | The injection code can also skip all other currently defined radiotap fields |
49 | facilitating replay of captured radiotap headers directly. | |
08d1f215 | 50 | |
de2b3e86 | 51 | Here is an example valid radiotap header defining some parameters |
08d1f215 AG |
52 | |
53 | 0x00, 0x00, // <-- radiotap version | |
54 | 0x0b, 0x00, // <- radiotap header length | |
55 | 0x04, 0x0c, 0x00, 0x00, // <-- bitmap | |
56 | 0x6c, // <-- rate | |
57 | 0x0c, //<-- tx power | |
58 | 0x01 //<-- antenna | |
59 | ||
60 | The ieee80211 header follows immediately afterwards, looking for example like | |
61 | this: | |
62 | ||
63 | 0x08, 0x01, 0x00, 0x00, | |
64 | 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, | |
65 | 0x13, 0x22, 0x33, 0x44, 0x55, 0x66, | |
66 | 0x13, 0x22, 0x33, 0x44, 0x55, 0x66, | |
67 | 0x10, 0x86 | |
68 | ||
69 | Then lastly there is the payload. | |
70 | ||
71 | After composing the packet contents, it is sent by send()-ing it to a logical | |
72 | mac80211 interface that is in Monitor mode. Libpcap can also be used, | |
73 | (which is easier than doing the work to bind the socket to the right | |
74 | interface), along the following lines: | |
75 | ||
76 | ppcap = pcap_open_live(szInterfaceName, 800, 1, 20, szErrbuf); | |
77 | ... | |
78 | r = pcap_inject(ppcap, u8aSendBuffer, nLength); | |
79 | ||
de2b3e86 | 80 | You can also find a link to a complete inject application here: |
08d1f215 | 81 | |
de2b3e86 | 82 | http://wireless.kernel.org/en/users/Documentation/packetspammer |
08d1f215 AG |
83 | |
84 | Andy Green <andy@warmcat.com> |