Sniffer Introduction - Espressif ESP8266 Technical Reference

!
14.
14.1. Sniffer Introduction
ESP8266 can enter promiscuous mode (sniffer) and capture IEEE 802.11 packets in the air.
The following HT20 packets are support:
802.11b
•
802.11g
•
802.11n (from MCS0 to MCS7)
•
AMPDU types of packets
•
The following are not supported:
HT40
•
LDPC
•
Although ESP8266 can not completely decipher these kinds of IEEE80211 packets
completely, it can still obtain the length of these special packets.
In summary, while in sniffer mode, ESP8266 can either capture completely the packets or
obtain the length of the packet:
Packets that ESP8266 can decipher completely; ESP8266 returns with the
•
- MAC address of the both side of communication and encryption type and
- the length of entire packet.
Packets that ESP8266 can only partial decipher; ESP8266 returns with
•
- the length of packet.
Structure RxControl and sniffer_buf are used to represent these two kinds of packets.
Structure sniffer_buf contains structure RxControl.
struct RxControl {
signed rssi:8;
unsigned rate:4;
unsigned is_group:1;
unsigned:1;
unsigned sig_mode:2;
packet;
unsigned legacy_length:12; // if not 11n packet, shows length of
packet.
unsigned damatch0:1;
unsigned damatch1:1;
Espressif
Sniffer Introduction
// signal intensity of packet
// 0:is 11n packet; 1:is not 11n
80 86 ! /!
14. Sniffer Introduction
2016.05