1EXTCAP(4) EXTCAP(4)
2
6 extcap - The extcap interface
7
9 The extcap interface is a versatile plugin interface that allows
10 external binaries to act as capture interfaces directly in Wireshark.
11 It is used in scenarios, where the source of the capture is not a
12 traditional capture model (live capture from an interface, from a pipe,
13 from a file, etc). The typical example is connecting esoteric hardware
14 of some kind to the main Wireshark application.
15 Without extcap, a capture can always be achieved by directly writing to
17 a capture file:
18 the-esoteric-binary --the-strange-flag --interface=stream1 --file dumpfile.pcap &
20 wireshark dumpfile.pcap
21 but the extcap interface allows for such a connection to be easily
23 established and configured using the Wireshark GUI.
24 The extcap subsystem is made of multiple extcap binaries that are
26 automatically called by the GUI in a row. In the following chapters we
27 will refer to them as "the extcaps".
28 Extcaps may be any binary or script within the extcap directory. Please
30 note, that scripts need to be executable without prefacing a script
31 interpreter before the call.
32 WINDOWS USERS: Because of restrictions directly calling the script may
34 not always work. In such a case, a batch file may be provided, which
35 then in turn executes the script. Please refer to doc/extcap_example.py
36 for more information.
37 When Wireshark launches an extcap, it automatically adds its
39 installation path (normally C:\Program Files\Wireshark\) to the DLL
40 search path so that the extcap library dependencies can be found (it is
41 not designed to be launched by hand). This is done on purpose. There
42 should only be extcap programs (executables, Python scripts, ...) in
43 the extcap folder to reduce the startup time and not have Wireshark
44 trying to execute other file types.
45
47 Grammar elements:
48 arg (options)
50 argument for CLI calling
51 number
53 Reference # of argument for other values, display order
54 call
56 Literal argument to call (--call=...)
57 display
59 Displayed name
60 default
62 Default value, in proper form for type
63 range
65 Range of valid values for UI checking (min,max) in proper form
66 type
68 Argument type for UI filtering for raw, or UI type for selector:
70 integer
72 unsigned
73 long (may include scientific / special notation)
74 float
75 selector (display selector table, all values as strings)
76 boolean (display checkbox)
77 radio (display group of radio buttons with provided values, all values as strings)
78 fileselect (display a dialog to select a file from the filesystem, value as string)
79 multicheck (display a textbox for selecting multiple options, values as strings)
80 password (display a textbox with masked text)
81 timestamp (display a calendar)
82 value (options)
84 Values for argument selection
86 arg Argument # this value applies to
87
89 Example 1:
90 arg {number=0}{call=--channel}{display=Wi-Fi Channel}{type=integer}{required=true}
92 arg {number=1}{call=--chanflags}{display=Channel Flags}{type=radio}
93 arg {number=2}{call=--interface}{display=Interface}{type=selector}
94 value {arg=0}{range=1,11}
95 value {arg=1}{value=ht40p}{display=HT40+}
96 value {arg=1}{value=ht40m}{display=HT40-}
97 value {arg=1}{value=ht20}{display=HT20}
98 value {arg=2}{value=wlan0}{display=wlan0}
99 Example 2:
101 arg {number=0}{call=--usbdevice}{USB Device}{type=selector}
103 value {arg=0}{call=/dev/sysfs/usb/foo/123}{display=Ubertooth One sn 1234}
104 value {arg=0}{call=/dev/sysfs/usb/foo/456}{display=Ubertooth One sn 8901}
105 Example 3:
107 arg {number=0}{call=--usbdevice}{USB Device}{type=selector}
109 arg {number=1}{call=--server}{display=IP address for log server}{type=string}{validation=(?:\d{1,3}\.){3}\d{1,3}}
110 flag {failure=Permission denied opening Ubertooth device}
111 Example 4:
113 arg {number=0}{call=--username}{display=Username}{type=string}
115 arg {number=1}{call=--password}{display=Password}{type=password}
116 Example 5:
118 arg {number=0}{call=--start}{display=Start Time}{type=timestamp}
120 arg {number=1}{call=--end}{display=End Time}{type=timestamp}
121
123 • If you’re running Wireshark as root, we can’t save you.
124 • Dumpcap retains suid/setgid and group execute permissions for users
126 in the “wireshark” group only.
127 • Third-party capture programs run with whatever privileges they’re
129 installed with.
130 • If an attacker can write to a system binary directory, it’s game
132 over.
133 • You can find your local extcap directory in About › Folders.
135
137 wireshark(1), tshark(1), dumpcap(1), androiddump(1), sshdump(1),
138 randpktdump(1)
139
141 Extcap is feature of Wireshark. The latest version of Wireshark can be
142 found at https://www.wireshark.org.
143 HTML versions of the Wireshark project man pages are available at
145 https://www.wireshark.org/docs/man-pages.
146 2022-12-08 EXTCAP(4)