1EXTCAP(4) The Wireshark Network Analyzer EXTCAP(4)
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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 app.
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 USER: 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 (c:\Program Files\Wireshark\) to the DLL search path
40 so that the extcap library dependencies can be found (it is not
41 designed to be launched by hand). This is done on purpose. There
42 should only be extcap programs (executable, python scripts, ...) in the
43 extcap folder to reduce the startup time and not have Wireshark trying
44 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:
69 integer
71 unsigned
72 long (may include scientific / special notation)
73 float
74 selector (display selector table, all values as strings)
75 boolean (display checkbox)
76 radio (display group of radio buttons with provided values, all values as strings)
77 fileselect (display a dialog to select a file from the filesystem, value as string)
78 multicheck (display a textbox for selecting multiple options, values as strings)
79 password (display a textbox with masked text)
80 timestamp (display a calendar)
81 value (options)
83 Values for argument selection
84 arg Argument # this value applies to
85
87 Example 1:
88 arg {number=0}{call=--channel}{display=Wi-Fi Channel}{type=integer}{required=true}
90 arg {number=1}{call=--chanflags}{display=Channel Flags}{type=radio}
91 arg {number=2}{call=--interface}{display=Interface}{type=selector}
92 value {arg=0}{range=1,11}
93 value {arg=1}{value=ht40p}{display=HT40+}
94 value {arg=1}{value=ht40m}{display=HT40-}
95 value {arg=1}{value=ht20}{display=HT20}
96 value {arg=2}{value=wlan0}{display=wlan0}
97 Example 2:
99 arg {number=0}{call=--usbdevice}{USB Device}{type=selector}
101 value {arg=0}{call=/dev/sysfs/usb/foo/123}{display=Ubertooth One sn 1234}
102 value {arg=0}{call=/dev/sysfs/usb/foo/456}{display=Ubertooth One sn 8901}
103 Example 3:
105 arg {number=0}{call=--usbdevice}{USB Device}{type=selector}
107 arg {number=1}{call=--server}{display=IP address for log server}{type=string}{validation=(?:\d{1,3}\.){3}\d{1,3}}
108 flag {failure=Permission denied opening Ubertooth device}
109 Example 4:
111 arg {number=0}{call=--username}{display=Username}{type=string}
112 arg {number=1}{call=--password}{display=Password}{type=password}
113 Example 5:
115 arg {number=0}{call=--start}{display=Start Time}{type=timestamp}
116 arg {number=1}{call=--end}{display=End Time}{type=timestamp}
117
119 - Users running wireshark as root, we can't save you
120 - Dumpcap retains suid/setgid and group+x permissions to allow users in
121 wireshark group only
122 - Third-party capture programs run w/ whatever privs they're installed
123 with
124 - If an attacker can write to a system binary directory, we're game
125 over anyhow
126 - Reference the folders tab in the wireshark->about information, to see
127 from which directory extcap is being run
128
130 wireshark(1), tshark(1), dumpcap(1), androiddump(1), sshdump(1),
131 randpktdump(1)
132
134 Extcap is feature of Wireshark. The latest version of Wireshark can be
135 found at <https://www.wireshark.org>.
136 HTML versions of the Wireshark project man pages are available at:
138 <https://www.wireshark.org/docs/man-pages>.
1393.2.3 2020-04-13 EXTCAP(4)