wireshark/doc/extcap.adoc

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= extcap(4)
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== NAME

extcap - The extcap interface

== DESCRIPTION

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 USERS: 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/extcap_example.py for more information.

When Wireshark launches an extcap, it automatically adds its installation path (normally _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 (executables, Python scripts, ...) in the extcap folder to reduce the startup time and not have Wireshark trying to execute other file types.

== GRAMMAR ELEMENTS

Grammar elements:

arg (options)::
argument for CLI calling

number::
Reference # of argument for other values, display order

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

display::
Displayed name

default::
Default value, in proper form for type

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

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

    integer
    unsigned
    long (may include scientific / special notation)
    float
    selector (display selector table, all values as strings)
    editselector (selector table which can be overridden, 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
--

== EXAMPLES

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 {number=1}{call=--password}{display=Password}{type=password}

Example 5:

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

== Security Considerations

- If you're running Wireshark as root, we can't save you.
- Dumpcap retains suid/setgid and group execute permissions for users in the “wireshark” group only.
- Third-party capture programs run with whatever privileges they're installed with.
- If an attacker can write to a system binary directory, it's game over.
- You can find your local extcap directory in menu:About[Folders].

== SEE ALSO

xref:wireshark.html[wireshark](1), xref:tshark.html[tshark](1), xref:dumpcap.html[dumpcap](1), xref:androiddump.html[androiddump](1), xref:sshdump.html[sshdump](1), xref:randpktdump.html[randpktdump](1)

== NOTES

*Extcap* is feature of *Wireshark*.
The latest version of *Wireshark* can be found at https://www.wireshark.org.

HTML versions of the Wireshark project man pages are available at
https://www.wireshark.org/docs/man-pages.