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 | ||
5c05803a SE |
40 | IEEE80211_RADIOTAP_MCS_SGI: use short guard interval |
41 | IEEE80211_RADIOTAP_MCS_BW_40: send in HT40 mode | |
dfdfc2be SE |
42 | |
43 | * IEEE80211_RADIOTAP_DATA_RETRIES | |
44 | ||
45 | number of retries when either IEEE80211_RADIOTAP_RATE or | |
46 | IEEE80211_RADIOTAP_MCS was used | |
47 | ||
646e76bb LB |
48 | * IEEE80211_RADIOTAP_VHT |
49 | ||
50 | VHT mcs and number of streams used in the transmission (only for devices | |
51 | without own rate control). Also other fields are parsed | |
52 | ||
53 | flags field | |
54 | IEEE80211_RADIOTAP_VHT_FLAG_SGI: use short guard interval | |
55 | ||
56 | bandwidth field | |
57 | 1: send using 40MHz channel width | |
58 | 4: send using 80MHz channel width | |
59 | 11: send using 160MHz channel width | |
60 | ||
58d4185e JB |
61 | The injection code can also skip all other currently defined radiotap fields |
62 | facilitating replay of captured radiotap headers directly. | |
08d1f215 | 63 | |
de2b3e86 | 64 | Here is an example valid radiotap header defining some parameters |
08d1f215 AG |
65 | |
66 | 0x00, 0x00, // <-- radiotap version | |
67 | 0x0b, 0x00, // <- radiotap header length | |
68 | 0x04, 0x0c, 0x00, 0x00, // <-- bitmap | |
69 | 0x6c, // <-- rate | |
70 | 0x0c, //<-- tx power | |
71 | 0x01 //<-- antenna | |
72 | ||
73 | The ieee80211 header follows immediately afterwards, looking for example like | |
74 | this: | |
75 | ||
76 | 0x08, 0x01, 0x00, 0x00, | |
77 | 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, | |
78 | 0x13, 0x22, 0x33, 0x44, 0x55, 0x66, | |
79 | 0x13, 0x22, 0x33, 0x44, 0x55, 0x66, | |
80 | 0x10, 0x86 | |
81 | ||
82 | Then lastly there is the payload. | |
83 | ||
84 | After composing the packet contents, it is sent by send()-ing it to a logical | |
85 | mac80211 interface that is in Monitor mode. Libpcap can also be used, | |
86 | (which is easier than doing the work to bind the socket to the right | |
87 | interface), along the following lines: | |
88 | ||
89 | ppcap = pcap_open_live(szInterfaceName, 800, 1, 20, szErrbuf); | |
90 | ... | |
91 | r = pcap_inject(ppcap, u8aSendBuffer, nLength); | |
92 | ||
de2b3e86 | 93 | You can also find a link to a complete inject application here: |
08d1f215 | 94 | |
de2b3e86 | 95 | http://wireless.kernel.org/en/users/Documentation/packetspammer |
08d1f215 AG |
96 | |
97 | Andy Green <andy@warmcat.com> |