=begin man

=encoding utf8

=end man

=head1 NAME

extcap - The extcap interface

=head1 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 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/extcap_example.py 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.


=head1 GRAMMAR ELEMENTS

Grammar elements:

=over 4

=item arg (options)

argument for CLI calling

=item number

Reference # of argument for other values, display order

=item call

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

=item display

Displayed name

=item default

Default value, in proper form for type

=item range

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

=item 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)
    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)

=item value (options)

    Values for argument selection
    arg     Argument # this value applies to

=back

=head1 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}

=head1 Security awareness

=over 4

=item - Users running wireshark as root, we can't save you

=item - Dumpcap retains suid/setgid and group+x permissions to allow users in wireshark group only

=item - Third-party capture programs run w/ whatever privs they're installed with

=item - If an attacker can write to a system binary directory, we're game over anyhow

=item - Reference the folders tab in the wireshark->about information, to see from which directory extcap is being run

=back

=head1 SEE ALSO

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

=head1 NOTES

B<Extcap> is feature of B<Wireshark>.  The latest version
of B<Wireshark> can be found at L<https://www.wireshark.org>.

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