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Commit | Line | Data |
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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 | ||
15 | Despite 13 radiotap argument types are 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 | 19 | * IEEE80211_RADIOTAP_RATE |
08d1f215 | 20 | |
58d4185e | 21 | rate in 500kbps units, automatic if invalid or not present |
08d1f215 | 22 | |
58d4185e JB |
23 | |
24 | * IEEE80211_RADIOTAP_ANTENNA | |
25 | ||
26 | antenna to use, automatic if not present | |
27 | ||
28 | ||
29 | * IEEE80211_RADIOTAP_DBM_TX_POWER | |
30 | ||
31 | transmit power in dBm, automatic if not present | |
32 | ||
33 | ||
34 | * IEEE80211_RADIOTAP_FLAGS | |
35 | ||
36 | IEEE80211_RADIOTAP_F_FCS: FCS will be removed and recalculated | |
37 | IEEE80211_RADIOTAP_F_WEP: frame will be encrypted if key available | |
38 | IEEE80211_RADIOTAP_F_FRAG: frame will be fragmented if longer than the | |
39 | current fragmentation threshold. Note that | |
40 | this flag is only reliable when software | |
41 | fragmentation is enabled) | |
42 | ||
43 | The injection code can also skip all other currently defined radiotap fields | |
44 | facilitating replay of captured radiotap headers directly. | |
08d1f215 AG |
45 | |
46 | Here is an example valid radiotap header defining these three parameters | |
47 | ||
48 | 0x00, 0x00, // <-- radiotap version | |
49 | 0x0b, 0x00, // <- radiotap header length | |
50 | 0x04, 0x0c, 0x00, 0x00, // <-- bitmap | |
51 | 0x6c, // <-- rate | |
52 | 0x0c, //<-- tx power | |
53 | 0x01 //<-- antenna | |
54 | ||
55 | The ieee80211 header follows immediately afterwards, looking for example like | |
56 | this: | |
57 | ||
58 | 0x08, 0x01, 0x00, 0x00, | |
59 | 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, | |
60 | 0x13, 0x22, 0x33, 0x44, 0x55, 0x66, | |
61 | 0x13, 0x22, 0x33, 0x44, 0x55, 0x66, | |
62 | 0x10, 0x86 | |
63 | ||
64 | Then lastly there is the payload. | |
65 | ||
66 | After composing the packet contents, it is sent by send()-ing it to a logical | |
67 | mac80211 interface that is in Monitor mode. Libpcap can also be used, | |
68 | (which is easier than doing the work to bind the socket to the right | |
69 | interface), along the following lines: | |
70 | ||
71 | ppcap = pcap_open_live(szInterfaceName, 800, 1, 20, szErrbuf); | |
72 | ... | |
73 | r = pcap_inject(ppcap, u8aSendBuffer, nLength); | |
74 | ||
75 | You can also find sources for a complete inject test applet here: | |
76 | ||
77 | http://penumbra.warmcat.com/_twk/tiki-index.php?page=packetspammer | |
78 | ||
79 | Andy Green <andy@warmcat.com> |