+.. SPDX-License-Identifier: GPL-2.0
+
+=========================================
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:
+following format::
[ radiotap header ]
[ ieee80211 header ]
* 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
+ ========================= ===========================================
+ 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
+ ============================= ========================================
+ IEEE80211_RADIOTAP_F_TX_NOACK frame should be sent without waiting for
an ACK even if it is a unicast frame
+ ============================= ========================================
* IEEE80211_RADIOTAP_RATE
HT rate for the transmission (only for devices without own rate control).
Also some flags are parsed
- IEEE80211_RADIOTAP_MCS_SGI: use short guard interval
- IEEE80211_RADIOTAP_MCS_BW_40: send in HT40 mode
+ ============================ ========================
+ IEEE80211_RADIOTAP_MCS_SGI use short guard interval
+ IEEE80211_RADIOTAP_MCS_BW_40 send in HT40 mode
+ ============================ ========================
* IEEE80211_RADIOTAP_DATA_RETRIES
without own rate control). Also other fields are parsed
flags field
- IEEE80211_RADIOTAP_VHT_FLAG_SGI: use short guard interval
+ IEEE80211_RADIOTAP_VHT_FLAG_SGI: use short guard interval
bandwidth field
- 1: send using 40MHz channel width
- 4: send using 80MHz channel width
- 11: send using 160MHz channel width
+ * 1: send using 40MHz channel width
+ * 4: send using 80MHz channel width
+ * 11: send using 160MHz channel width
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
+Here is an example valid radiotap header defining some parameters::
0x00, 0x00, // <-- radiotap version
0x0b, 0x00, // <- radiotap header length
0x01 //<-- antenna
The ieee80211 header follows immediately afterwards, looking for example like
-this:
+this::
0x08, 0x01, 0x00, 0x00,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
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:
+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: