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Is it possible to attach a IE field to my wifi hotspot so that it appear in the iwlist output of other machine scanning it?

Example:

  • I choose 1234567891011121314151617181920 to be the additional field for my wifi hotspot (MAC address 11:22:33:44:55:66)

  • Users scanning my wifi hotspot with command iwlist wlan0 scan, should give the output:

      wlan0  Scan completed :
       Cell 01 - Address: 11:22:33:44:55:66
      [...]
      IE: Unknown 1234567891011121314151617181920
      [...]
    
  • This would all depend on what wifi-hotspot you have, as it is this that is being configured. (This does not seem to be a Unix question. If it is then please clarify.) – ctrl-alt-delor Dec 31 '16 at 17:30
  • What does your hotspot run on (software and what access do you have)? Unless you have full access because e.g. you set it up yourself I don't think this question belongs here. – phk Dec 31 '16 at 17:40
4

IE stands for Information Element. They are transmitted as part of the beacon frames and carry all kinds of information such as SSID, supported rates, etc.

Information element                        Element ID    Length (in octets)
---------------------------------------------------------------------------
SSID (see 7.3.2.1)                         0             2 to 34
Supported rates (see 7.3.2.2)              1             3 to 10
FH Parameter Set (see 7.3.2.3)             2             7
DS Parameter Set (see 7.3.2.4)             3             3
CF Parameter Set (see 7.3.2.5)             4             8
TIM (see 7.3.2.6)                          5             6 to 256
IBSS Parameter Set (see 7.3.2.7)           6             4
Country (see 7.3.2.9)                      7             8 to 256
Hopping Pattern Parameters (see 7.3.2.10)  8             4
Hopping Pattern Table (see 7.3.2.11)       9             6 to 256
Request (see 7.3.2.12)                     10            2 to 256
BSS Load (see 7.3.2.28)                    11            7
EDCA Parameter Set (see 7.3.2.29)          12            20
TSPEC (see 7.3.2.30)                       13            57
TCLAS (see 7.3.2.31)                       14            2 to 257
Schedule (see 7.3.2.34)                    15            16
Challenge text (see 7.3.2.8)               16            3 to 255
Reserved                                   17–31
Power Constraint (see 7.3.2.15)            32            3
Power Capability (see 7.3.2.16)            33            4
TPC Request (see 7.3.2.17)                 34            2
TPC Report (see 7.3.2.18)                  35            4
Supported Channels (see 7.3.2.19)          36            4 to 256
Channel Switch Announcement (see 7.3.2.20) 37            5
Measurement Request (see 7.3.2.21)         38            5 to 16
Measurement Report (see 7.3.2.22)          39            5 to 24
Quiet (see 7.3.2.23)                       40            8
IBSS DFS (see 7.3.2.24)                    41            10 to 255
ERP Information (see 7.3.2.13)             42            3
TS Delay (see 7.3.2.32)                    43            6
TCLAS Processing (see 7.3.2.33)            44            3
Reserved                                   45
QoS Capability (see 7.3.2.35)              46            3
Reserved                                   47
RSN (see 7.3.2.25)                         48            36 to 256
Reserved                                   49
Extended Supported Rates (see 7.3.2.14)    50            3 to 257
Reserved                                   51–126
Extended Capabilities                      127           2 to 257
Reserved                                   128–220
Vendor Specific (see 7.3.2.26)             221           3 to 257
Reserved                                   222–255

Some of these information elements are vendor specific, meaning they will probably be ignored by other vendors. Reserved means it may have a standard meaning in the future, in fact some of them already have. (I'm looking at an old standard.) You can configure them in hostapd.conf

# Additional vendor specific elements for Beacon and Probe Response frames
# This parameter can be used to add additional vendor specific element(s) into
# the end of the Beacon and Probe Response frames. The format for these
# element(s) is a hexdump of the raw information elements (id+len+payload for
# one or more elements)
vendor_elements=dd0411223301

The hex data is the of the following structure:

Vendor Specific Information Element Format

The Element ID shall be dd, OUI is a 3-byte number allocated by IEEE, but the good news is iwlist displays all of them as unknown, except WPA (0050f2) and WPA2 (000fac).

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