projects / deliverable / linux.git / blame
| 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 | ||
| 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> |