Provided by: wireshark-common_3.6.7-1_amd64 bug


       extcap - The extcap interface


       The extcap interface is a versatile plugin interface that allows external binaries to act
       as capture interfaces directly in Wireshark. It is used in scenarios, where the source of
       the capture is not a traditional capture model (live capture from an interface, from a
       pipe, from a file, etc). The typical example is connecting esoteric hardware of some kind
       to the main Wireshark application.

       Without extcap, a capture can always be achieved by directly writing to a capture file:

           the-esoteric-binary --the-strange-flag --interface=stream1 --file dumpfile.pcap &
           wireshark dumpfile.pcap

       but the extcap interface allows for such a connection to be easily established and
       configured using the Wireshark GUI.

       The extcap subsystem is made of multiple extcap binaries that are automatically called by
       the GUI in a row. In the following chapters we will refer to them as "the extcaps".

       Extcaps may be any binary or script within the extcap directory. Please note, that scripts
       need to be executable without prefacing a script interpreter before the call.

       WINDOWS USER: Because of restrictions directly calling the script may not always work. In
       such a case, a batch file may be provided, which then in turn executes the script. Please
       refer to doc/ for more information.

       When Wireshark launches an extcap, it automatically adds its installation path (c:\Program
       Files\Wireshark\) to the DLL search path so that the extcap library dependencies can be
       found (it is not designed to be launched by hand). This is done on purpose. There should
       only be extcap programs (executable, python scripts, ...) in the extcap folder to reduce
       the startup time and not have Wireshark trying to execute other file types.


       Grammar elements:

       arg (options)

           argument for CLI calling


           Reference # of argument for other values, display order


           Literal argument to call (--call=...)


           Displayed name


           Default value, in proper form for type


           Range of valid values for UI checking (min,max) in proper form


           Argument type for UI filtering for raw, or UI type for selector:

               long (may include scientific / special notation)
               selector (display selector table, all values as strings)
               boolean (display checkbox)
               radio (display group of radio buttons with provided values, all values as strings)
               fileselect (display a dialog to select a file from the filesystem, value as string)
               multicheck (display a textbox for selecting multiple options, values as strings)
               password (display a textbox with masked text)
               timestamp (display a calendar)

       value (options)

               Values for argument selection
               arg     Argument # this value applies to


       Example 1:

           arg {number=0}{call=--channel}{display=Wi-Fi Channel}{type=integer}{required=true}
           arg {number=1}{call=--chanflags}{display=Channel Flags}{type=radio}
           arg {number=2}{call=--interface}{display=Interface}{type=selector}
           value {arg=0}{range=1,11}
           value {arg=1}{value=ht40p}{display=HT40+}
           value {arg=1}{value=ht40m}{display=HT40-}
           value {arg=1}{value=ht20}{display=HT20}
           value {arg=2}{value=wlan0}{display=wlan0}

       Example 2:

           arg {number=0}{call=--usbdevice}{USB Device}{type=selector}
           value {arg=0}{call=/dev/sysfs/usb/foo/123}{display=Ubertooth One sn 1234}
           value {arg=0}{call=/dev/sysfs/usb/foo/456}{display=Ubertooth One sn 8901}

       Example 3:

           arg {number=0}{call=--usbdevice}{USB Device}{type=selector}
           arg {number=1}{call=--server}{display=IP address for log server}{type=string}{validation=(?:\d{1,3}\.){3}\d{1,3}}
           flag {failure=Permission denied opening Ubertooth device}

       Example 4: arg {number=0}{call=--username}{display=Username}{type=string} arg

       Example 5: arg {number=0}{call=--start}{display=Start Time}{type=timestamp} arg
       {number=1}{call=--end}{display=End Time}{type=timestamp}


       •   Users running wireshark as root, we can’t save you

       •   Dumpcap retains suid/setgid and group+x permissions to allow users in wireshark group

       •   Third-party capture programs run w/ whatever privs they’re installed with

       •   If an attacker can write to a system binary directory, we’re game over anyhow

       •   Reference the folders tab in the wireshark→about information, to see from which
           directory extcap is being run


       wireshark(1), tshark(1), dumpcap(1), androiddump(1), sshdump(1), randpktdump(1)


       Extcap is feature of Wireshark. The latest version of Wireshark can be found at

       HTML versions of the Wireshark project man pages are available at

                                            2022-07-28                                  EXTCAP(4)