OVMS3-idf/examples/wifi/simple_sniffer/README.md
morris 900b69a33e example: add console command for wifi sniffer
1. add mount/unmount command
2. add sniffer command, supporting options
3. make pcap a component
2018-10-19 11:51:56 +08:00

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# Simple Sniffer Example
(See the README.md file in the upper level 'examples' directory for more information about examples.)
## Overview
This example demonstrates basic usage of wifi sniffer mode by saving packets into SD card with pcap format. Go to wikipedia for more information about [pcap](https://en.wikipedia.org/wiki/Pcap).
This example is based on esp-idf's console component. For more information about console you should read this [guide](https://docs.espressif.com/projects/esp-idf/en/latest/api-guides/console.html).
## How to use example
### Hardware Required
To run this example, you should have one ESP32 dev board integrated with a SD card slot (e.g ESP32-WROVER Kit) or just connect ESP32-DevKitC to a SD card breakout board.
### Configure the project
Enter `make menuconfig` if you are using GNU Make based build system or enter `idf.py menuconfig` if you are using CMake based build system. Then go into `Example Configuration` menu.
- Check `Store command history in flash` if you want to save command history into flash (recommend).
- Set the mount point in your filesystem, for example, `/sdcard` if you want to store pcap file into SD card.
- Set the length of sniffer work queue.
- Set the stack size of the sniffer task.
- Set the priority of the sniffer task.
- Set the max number of packets to store in a single pcap file. The number of packets usually will be very large, so we just truncate them into multiple files. You should set a threshold value here.
### Build and Flash
Enter `make -j4 flash monitor` if you are using GNU Make based build system or enter `idf.py build flash monitor` if you' are using CMake based build system.
(To exit the serial monitor, type ``Ctrl-]``.)
See the [Getting Started Guide](https://docs.espressif.com/projects/esp-idf/en/latest/get-started/index.html) for full steps to configure and use ESP-IDF to build projects.
## Example Output
### `sniffer` Command Usage
> sniffer [-f <file>][-i ] [-F <mgmt|data|ctrl|misc|mpdu|ampdu>]... [-c <channel>][--stop]
> Capture specific packet and store in pcap format
> -f, --file=<file> name of the file storing the packets in pcap format
> -i, --interface=<wlan> which interface to capture packet
> -F, --filter=<mgmt|data|ctrl|misc|mpdu|ampdu> filter parameters
> -c, --channel=<channel> communication channel to use
> --stop stop running sniffer
The `sniffer` command support some important options as follow:
* `-f`: Specify the name of file who will store the packets, default value is `sniffer`, and the resulting file name will be like “snifferX.pcap”, here X shows the files order.
* `-i`: Specify the interface to sniffer packets, currently only support `wlan`
* `-c` :Specify the channel to sniffer packet
* `-F`: Specify the filter condition, currently only support following filter conditions, you can select any number of them
* mgmt: Management packets
* data: Data packets
* ctrl: Control packets
* misc: Other packets
* mpdu: MPDU packets
* ampdu: AMPDU packets
* `--stop`: Stop sniffer job
### Mount SD Card
```bash
=======================================================
| Steps to sniffer WiFi packets |
| |
| 1. Enter 'help' to check all commands' usage |
| 2. Enter 'mount <device>' to mount filesystem |
| 3. Enter 'sniffer' to start capture packets |
| 4. Enter 'unmount <device>' to unmount filesystem |
| |
=======================================================
esp32> mount sd
I (158912) example: Initializing SD card
I (158912) example: Using SDMMC peripheral
I (158912) gpio: GPIO[13]| InputEn: 0| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0
Name: SA16G
Type: SDHC/SDXC
Speed: 20 MHz
Size: 14832MB
```
### Start Sniffer
```bash
esp32> sniffer -f sniffer-example -i wlan -c 2
I (36200) cmd_sniffer: Start WiFi Promicuous Mode
I (36270) phy: phy_version: 4000, b6198fa, Sep 3 2018, 15:11:06, 0, 0
I (36270) wifi: ic_enable_sniffer
I (36290) pcap: Store packets to file: /sdcard/sniffer-example0.pcap
I (103810) pcap: Close Pcap file OK
I (103830) pcap: Store packets to file: /sdcard/sniffer-example1.pcap
I (177300) pcap: Close Pcap file OK
I (177320) pcap: Store packets to file: /sdcard/sniffer-example2.pcap
esp32> sniffer --stop
I (212250) wifi: ic_disable_sniffer
I (212250) wifi: flush txq
I (212250) wifi: stop sw txq
I (212260) wifi: lmac stop hw txq
I (212340) pcap: Close Pcap file OK
I (212340) cmd_sniffer: Sniffer Stopped
```
### Unmount SD Card
```bash
esp32> unmount sd
I (248800) example: Card unmounted
```
### Open PCap File in Wireshark
![sniffer-example0.pcap](sniffer-example0-pcap.png)
## Troubleshooting
- Make sure you have pluged in your SD card and mount it into filesystem before doing sniffer work or you will get error message like “Create file /sdcard/sniffer0.pcap failed”.
- To protect the SD card, we recommand you to execute command `unmount sd` before you plug out your SD card.
(For any technical queries, please open an [issue](https://github.com/espressif/esp-idf/issues) on GitHub. We will get back to you as soon as possible.)