monitor 模式是什么？

数据包通过无线电信号来传输，monitor模式下的网卡可以接收所有它可以接收的无线电信号并进行解析，不仅仅限于它所在的无线局域网。

那么ubuntu下的网卡的monitor模式如何开启呢？

第一步

首先使用命令查看当前的无线网卡支持哪些mode：

iw list

命令结果为 supported interface modes 有两个：

managed

monitor

Wiphy phy1

max # scan SSIDs: 4

max scan IEs length: 2257 bytes

Retry short limit: 7

Retry long limit: 4

Coverage class: 0 (up to 0m)

Supported Ciphers:

* WEP40 (00-0f-ac:1)

* WEP104 (00-0f-ac:5)

* TKIP (00-0f-ac:2)

* CCMP (00-0f-ac:4)

* 00-0f-ac:10

* GCMP (00-0f-ac:8)

* 00-0f-ac:9

Available Antennas: TX 0 RX 0

Supported interface modes:

* managed

* monitor

Band 1:

Capabilities: 0x172

HT20/HT40

Static SM Power Save

RX Greenfield

RX HT20 SGI

RX HT40 SGI

RX STBC 1-stream

Max AMSDU length: 3839 bytes

No DSSS/CCK HT40

Maximum RX AMPDU length 65535 bytes (exponent: 0x003)

Minimum RX AMPDU time spacing: 2 usec (0x04)

HT TX/RX MCS rate indexes supported: 0-7, 32

Bitrates (non-HT):

* 1.0 Mbps (short preamble supported)

* 2.0 Mbps (short preamble supported)

* 5.5 Mbps (short preamble supported)

* 11.0 Mbps (short preamble supported)

* 6.0 Mbps

* 9.0 Mbps

* 12.0 Mbps

* 18.0 Mbps

* 24.0 Mbps

* 36.0 Mbps

* 48.0 Mbps

* 54.0 Mbps

Frequencies:

* 2412 MHz [1] (20.0 dBm)

* 2417 MHz [2] (20.0 dBm)

* 2422 MHz [3] (20.0 dBm)

* 2427 MHz [4] (20.0 dBm)

* 2432 MHz [5] (20.0 dBm)

* 2437 MHz [6] (20.0 dBm)

* 2442 MHz [7] (20.0 dBm)

* 2447 MHz [8] (20.0 dBm)

* 2452 MHz [9] (20.0 dBm)

* 2457 MHz [10] (20.0 dBm)

* 2462 MHz [11] (20.0 dBm)

* 2467 MHz [12] (20.0 dBm) (no IR)

* 2472 MHz [13] (20.0 dBm)

Supported commands:

* new_interface

* set_interface

* new_key

* start_ap

* new_station

* new_mpath

* set_mesh_config

* set_bss

* authenticate

* associate

* deauthenticate

* disassociate

* join_ibss

* join_mesh

* set_tx_bitrate_mask

* frame

* frame_wait_cancel

* set_wiphy_netns

* set_channel

* set_wds_peer

* probe_client

* set_noack_map

* register_beacons

* start_p2p_device

* set_mcast_rate

* Unknown command (104)

* connect

* disconnect

Supported TX frame types:

* IBSS: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0

* managed: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0

* AP: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0

* AP/VLAN: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0

* mesh point: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0

* P2P-client: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0

* P2P-GO: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0

* P2P-device: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0

Supported RX frame types:

* IBSS: 0x40 0xb0 0xc0 0xd0

* managed: 0x40 0xd0

* AP: 0x00 0x20 0x40 0xa0 0xb0 0xc0 0xd0

* AP/VLAN: 0x00 0x20 0x40 0xa0 0xb0 0xc0 0xd0

* mesh point: 0xb0 0xc0 0xd0

* P2P-client: 0x40 0xd0

* P2P-GO: 0x00 0x20 0x40 0xa0 0xb0 0xc0 0xd0

* P2P-device: 0x40 0xd0

software interface modes (can always be added):

* monitor

interface combinations are not supported

HT Capability overrides:

* MCS: ff ff ff ff ff ff ff ff ff ff

* maximum A-MSDU length

* supported channel width

* short GI for 40 MHz

* max A-MPDU length exponent

* min MPDU start spacing

Device supports TX status socket option.

Device supports HT-IBSS.

Device supports SAE with AUTHENTICATE command

Device supports low priority scan.

Device supports scan flush.

Device supports AP scan.

Device supports per-vif TX power setting

Driver supports a userspace MPM

Device supports active monitor (which will ACK incoming frames)

第二步

使用 iwconfig 可以查看网卡信息，其中可以看到我的网卡目前的模式是managed(而且名字很奇怪，不知道是否和使用虚拟机有关)

ens33     no wireless extensions.

lo        no wireless extensions.

wlx30b49e22ab5b  IEEE 802.11bgn  ESSID:off/any

Mode:Managed  Access Point: Not-Associated   Tx-Power=20 dBm

Retry short limit:7   RTS thr:off   Fragment thr:off

Power Management:off

第三步

关闭这个无线网卡，然后将模式改为monitor，(不关闭则无法更改mode)

sudo ifdown (your device name)

这个我遇到了第一个问题，就是使用设备名无法识别，于是我选择从GUI中关闭。

成功的关闭后，就可以执行下一个命令:

sudo iwconfig wlx30b49e22ab5b mode moniter

然后我使用命令 sudo ifconfig (your device name)up 开启设备，返现不成功！返回为：

SIOCSIFFLAGS: Operation not possible due to RF-kill

这是因为你的网卡 是 Soft-blocking，我直接写出适合我的解决方法，原文中要重启电脑，但是我没有重启之前就成功了。

sudo rfkill unblock wifi

sudo rfkill unblock all

然后上一个设置mode的命令就可以成功的执行了

第四步

此时使用命令：

sudo ifconfig (your device name)up

可以成功的开启网卡

再一次使用 iwconfig 命令查看的时候，发现:

ens33     no wireless extensions.

lo        no wireless extensions.

wlx30b49e22ab5b  IEEE 802.11bgn  Mode:Monitor  Frequency:2.412 GHz  Tx-Power=20 dBm

Retry short limit:7   RTS thr:off   Fragment thr:off

Power Management:off

网卡的模式已经变成了 Monitor 模式！

使用wireshark检测，使用此接口成功抓包！