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Diffstat (limited to 'Documentation/networking/mac80211-injection.txt')
| -rw-r--r-- | Documentation/networking/mac80211-injection.txt | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/Documentation/networking/mac80211-injection.txt b/Documentation/networking/mac80211-injection.txt new file mode 100644 index 000000000..3a930072b --- /dev/null +++ b/Documentation/networking/mac80211-injection.txt @@ -0,0 +1,67 @@ +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 + +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> |