1*4882a593Smuzhiyun.. SPDX-License-Identifier: GPL-2.0 2*4882a593Smuzhiyun 3*4882a593Smuzhiyun========================================= 4*4882a593SmuzhiyunHow to use packet injection with mac80211 5*4882a593Smuzhiyun========================================= 6*4882a593Smuzhiyun 7*4882a593Smuzhiyunmac80211 now allows arbitrary packets to be injected down any Monitor Mode 8*4882a593Smuzhiyuninterface from userland. The packet you inject needs to be composed in the 9*4882a593Smuzhiyunfollowing format:: 10*4882a593Smuzhiyun 11*4882a593Smuzhiyun [ radiotap header ] 12*4882a593Smuzhiyun [ ieee80211 header ] 13*4882a593Smuzhiyun [ payload ] 14*4882a593Smuzhiyun 15*4882a593SmuzhiyunThe radiotap format is discussed in 16*4882a593Smuzhiyun./Documentation/networking/radiotap-headers.rst. 17*4882a593Smuzhiyun 18*4882a593SmuzhiyunDespite many radiotap parameters being currently defined, most only make sense 19*4882a593Smuzhiyunto appear on received packets. The following information is parsed from the 20*4882a593Smuzhiyunradiotap headers and used to control injection: 21*4882a593Smuzhiyun 22*4882a593Smuzhiyun * IEEE80211_RADIOTAP_FLAGS 23*4882a593Smuzhiyun 24*4882a593Smuzhiyun ========================= =========================================== 25*4882a593Smuzhiyun IEEE80211_RADIOTAP_F_FCS FCS will be removed and recalculated 26*4882a593Smuzhiyun IEEE80211_RADIOTAP_F_WEP frame will be encrypted if key available 27*4882a593Smuzhiyun IEEE80211_RADIOTAP_F_FRAG frame will be fragmented if longer than the 28*4882a593Smuzhiyun current fragmentation threshold. 29*4882a593Smuzhiyun ========================= =========================================== 30*4882a593Smuzhiyun 31*4882a593Smuzhiyun * IEEE80211_RADIOTAP_TX_FLAGS 32*4882a593Smuzhiyun 33*4882a593Smuzhiyun ============================= ======================================== 34*4882a593Smuzhiyun IEEE80211_RADIOTAP_F_TX_NOACK frame should be sent without waiting for 35*4882a593Smuzhiyun an ACK even if it is a unicast frame 36*4882a593Smuzhiyun ============================= ======================================== 37*4882a593Smuzhiyun 38*4882a593Smuzhiyun * IEEE80211_RADIOTAP_RATE 39*4882a593Smuzhiyun 40*4882a593Smuzhiyun legacy rate for the transmission (only for devices without own rate control) 41*4882a593Smuzhiyun 42*4882a593Smuzhiyun * IEEE80211_RADIOTAP_MCS 43*4882a593Smuzhiyun 44*4882a593Smuzhiyun HT rate for the transmission (only for devices without own rate control). 45*4882a593Smuzhiyun Also some flags are parsed 46*4882a593Smuzhiyun 47*4882a593Smuzhiyun ============================ ======================== 48*4882a593Smuzhiyun IEEE80211_RADIOTAP_MCS_SGI use short guard interval 49*4882a593Smuzhiyun IEEE80211_RADIOTAP_MCS_BW_40 send in HT40 mode 50*4882a593Smuzhiyun ============================ ======================== 51*4882a593Smuzhiyun 52*4882a593Smuzhiyun * IEEE80211_RADIOTAP_DATA_RETRIES 53*4882a593Smuzhiyun 54*4882a593Smuzhiyun number of retries when either IEEE80211_RADIOTAP_RATE or 55*4882a593Smuzhiyun IEEE80211_RADIOTAP_MCS was used 56*4882a593Smuzhiyun 57*4882a593Smuzhiyun * IEEE80211_RADIOTAP_VHT 58*4882a593Smuzhiyun 59*4882a593Smuzhiyun VHT mcs and number of streams used in the transmission (only for devices 60*4882a593Smuzhiyun without own rate control). Also other fields are parsed 61*4882a593Smuzhiyun 62*4882a593Smuzhiyun flags field 63*4882a593Smuzhiyun IEEE80211_RADIOTAP_VHT_FLAG_SGI: use short guard interval 64*4882a593Smuzhiyun 65*4882a593Smuzhiyun bandwidth field 66*4882a593Smuzhiyun * 1: send using 40MHz channel width 67*4882a593Smuzhiyun * 4: send using 80MHz channel width 68*4882a593Smuzhiyun * 11: send using 160MHz channel width 69*4882a593Smuzhiyun 70*4882a593SmuzhiyunThe injection code can also skip all other currently defined radiotap fields 71*4882a593Smuzhiyunfacilitating replay of captured radiotap headers directly. 72*4882a593Smuzhiyun 73*4882a593SmuzhiyunHere is an example valid radiotap header defining some parameters:: 74*4882a593Smuzhiyun 75*4882a593Smuzhiyun 0x00, 0x00, // <-- radiotap version 76*4882a593Smuzhiyun 0x0b, 0x00, // <- radiotap header length 77*4882a593Smuzhiyun 0x04, 0x0c, 0x00, 0x00, // <-- bitmap 78*4882a593Smuzhiyun 0x6c, // <-- rate 79*4882a593Smuzhiyun 0x0c, //<-- tx power 80*4882a593Smuzhiyun 0x01 //<-- antenna 81*4882a593Smuzhiyun 82*4882a593SmuzhiyunThe ieee80211 header follows immediately afterwards, looking for example like 83*4882a593Smuzhiyunthis:: 84*4882a593Smuzhiyun 85*4882a593Smuzhiyun 0x08, 0x01, 0x00, 0x00, 86*4882a593Smuzhiyun 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 87*4882a593Smuzhiyun 0x13, 0x22, 0x33, 0x44, 0x55, 0x66, 88*4882a593Smuzhiyun 0x13, 0x22, 0x33, 0x44, 0x55, 0x66, 89*4882a593Smuzhiyun 0x10, 0x86 90*4882a593Smuzhiyun 91*4882a593SmuzhiyunThen lastly there is the payload. 92*4882a593Smuzhiyun 93*4882a593SmuzhiyunAfter composing the packet contents, it is sent by send()-ing it to a logical 94*4882a593Smuzhiyunmac80211 interface that is in Monitor mode. Libpcap can also be used, 95*4882a593Smuzhiyun(which is easier than doing the work to bind the socket to the right 96*4882a593Smuzhiyuninterface), along the following lines::: 97*4882a593Smuzhiyun 98*4882a593Smuzhiyun ppcap = pcap_open_live(szInterfaceName, 800, 1, 20, szErrbuf); 99*4882a593Smuzhiyun ... 100*4882a593Smuzhiyun r = pcap_inject(ppcap, u8aSendBuffer, nLength); 101*4882a593Smuzhiyun 102*4882a593SmuzhiyunYou can also find a link to a complete inject application here: 103*4882a593Smuzhiyun 104*4882a593Smuzhiyunhttps://wireless.wiki.kernel.org/en/users/Documentation/packetspammer 105*4882a593Smuzhiyun 106*4882a593SmuzhiyunAndy Green <andy@warmcat.com> 107