NAME¶
wireshark-filter - Wireshark filter syntax and reference
SYNOPSIS¶
wireshark [other options] [
-R "filter expression" ]
tshark [other options] [
-R "filter expression" ]
DESCRIPTION¶
Wireshark and
TShark share a powerful filter engine that helps
remove the noise from a packet trace and lets you see only the packets that
interest you. If a packet meets the requirements expressed in your filter,
then it is displayed in the list of packets. Display filters let you compare
the fields within a protocol against a specific value, compare fields against
fields, and check the existence of specified fields or protocols.
Filters are also used by other features such as statistics generation and packet
list colorization (the latter is only available to
Wireshark). This
manual page describes their syntax. A comprehensive reference of filter fields
can be found within Wireshark and in the display filter reference at
<
http://www.wireshark.org/docs/dfref/>.
FILTER SYNTAX¶
Check whether a field or protocol exists¶
The simplest filter allows you to check for the existence of a protocol or
field. If you want to see all packets which contain the IP protocol, the
filter would be "ip" (without the quotation marks). To see all
packets that contain a Token-Ring RIF field, use "tr.rif".
Think of a protocol or field in a filter as implicitly having the
"exists" operator.
Comparison operators¶
Fields can also be compared against values. The comparison operators can be
expressed either through English-like abbreviations or through C-like symbols:
eq, == Equal
ne, != Not Equal
gt, > Greater Than
lt, < Less Than
ge, >= Greater than or Equal to
le, <= Less than or Equal to
Search and match operators¶
Additional operators exist expressed only in English, not C-like syntax:
contains Does the protocol, field or slice contain a value
matches Does the protocol or text string match the given Perl
regular expression
The "contains" operator allows a filter to search for a sequence of
characters, expressed as a string (quoted or unquoted), or bytes, expressed as
a byte array. For example, to search for a given HTTP URL in a capture, the
following filter can be used:
http contains "http://www.wireshark.org"
The "contains" operator cannot be used on atomic fields, such as
numbers or IP addresses.
The "matches" operator allows a filter to apply to a specified
Perl-compatible regular expression (PCRE). The "matches" operator is
only implemented for protocols and for protocol fields with a text string
representation. For example, to search for a given WAP WSP User-Agent, you can
write:
wsp.user_agent matches "(?i)cldc"
This example shows an interesting PCRE feature: pattern match options have to be
specified with the
(?option
) construct. For instance,
(?i) performs a case-insensitive pattern match. More information on
PCRE can be found in the
pcrepattern(3) man page (Perl Regular
Expressions are explained in <
http://perldoc.perl.org/perlre.html>).
Functions¶
The filter language has the following functions:
upper(string-field) - converts a string field to uppercase
lower(string-field) - converts a string field to lowercase
upper() and
lower() are useful for performing case-insensitive
string comparisons. For example:
upper(ncp.nds_stream_name) contains "MACRO"
lower(mount.dump.hostname) == "angel"
Protocol field types¶
Each protocol field is typed. The types are:
ASN.1 object identifier
Boolean
Character string
Compiled Perl-Compatible Regular Expression (GRegex) object
Date and time
Ethernet or other MAC address
EUI64 address
Floating point (double-precision)
Floating point (single-precision)
Frame number
Globally Unique Identifier
IPv4 address
IPv6 address
IPX network number
Label
Protocol
Sequence of bytes
Signed integer, 1, 2, 3, 4, or 8 bytes
Time offset
Unsigned integer, 1, 2, 3, 4, or 8 bytes
An integer may be expressed in decimal, octal, or hexadecimal notation. The
following three display filters are equivalent:
frame.pkt_len > 10
frame.pkt_len > 012
frame.pkt_len > 0xa
Boolean values are either true or false. In a display filter expression testing
the value of a Boolean field, "true" is expressed as 1 or any other
non-zero value, and "false" is expressed as zero. For example, a
token-ring packet's source route field is Boolean. To find any source-routed
packets, a display filter would be:
tr.sr == 1
Non source-routed packets can be found with:
tr.sr == 0
Ethernet addresses and byte arrays are represented by hex digits. The hex digits
may be separated by colons, periods, or hyphens:
eth.dst eq ff:ff:ff:ff:ff:ff
aim.data == 0.1.0.d
fddi.src == aa-aa-aa-aa-aa-aa
echo.data == 7a
IPv4 addresses can be represented in either dotted decimal notation or by using
the hostname:
ip.dst eq www.mit.edu
ip.src == 192.168.1.1
IPv4 addresses can be compared with the same logical relations as numbers: eq,
ne, gt, ge, lt, and le. The IPv4 address is stored in host order, so you do
not have to worry about the endianness of an IPv4 address when using it in a
display filter.
Classless InterDomain Routing (CIDR) notation can be used to test if an IPv4
address is in a certain subnet. For example, this display filter will find all
packets in the 129.111 Class-B network:
ip.addr == 129.111.0.0/16
Remember, the number after the slash represents the number of bits used to
represent the network. CIDR notation can also be used with hostnames, as in
this example of finding IP addresses on the same Class C network as 'sneezy':
ip.addr eq sneezy/24
The CIDR notation can only be used on IP addresses or hostnames, not in variable
names. So, a display filter like "ip.src/24 == ip.dst/24" is not
valid (yet).
IPX networks are represented by unsigned 32-bit integers. Most likely you will
be using hexadecimal when testing IPX network values:
ipx.src.net == 0xc0a82c00
Strings are enclosed in double quotes:
http.request.method == "POST"
Inside double quotes, you may use a backslash to embed a double quote or an
arbitrary byte represented in either octal or hexadecimal.
browser.comment == "An embedded \" double-quote"
Use of hexadecimal to look for "HEAD":
http.request.method == "\x48EAD"
Use of octal to look for "HEAD":
http.request.method == "\110EAD"
This means that you must escape backslashes with backslashes inside double
quotes.
smb.path contains "\\\\SERVER\\SHARE"
looks for \\SERVER\SHARE in "smb.path".
The slice operator¶
You can take a slice of a field if the field is a text string or a byte array.
For example, you can filter on the vendor portion of an ethernet address (the
first three bytes) like this:
eth.src[0:3] == 00:00:83
Another example is:
http.content_type[0:4] == "text"
You can use the slice operator on a protocol name, too. The "frame"
protocol can be useful, encompassing all the data captured by
Wireshark
or
TShark.
token[0:5] ne 0.0.0.1.1
llc[0] eq aa
frame[100-199] contains "wireshark"
The following syntax governs slices:
[i:j] i = start_offset, j = length
[i-j] i = start_offset, j = end_offset, inclusive.
[i] i = start_offset, length = 1
[:j] start_offset = 0, length = j
[i:] start_offset = i, end_offset = end_of_field
Offsets can be negative, in which case they indicate the offset from the
end of the field. The last byte of the field is at offset -1, the last
but one byte is at offset -2, and so on. Here's how to check the last four
bytes of a frame:
frame[-4:4] == 0.1.2.3
or
frame[-4:] == 0.1.2.3
A slice is always compared against either a string or a byte sequence. As a
special case, when the slice is only 1 byte wide, you can compare it against a
hex integer that 0xff or less (which means it fits inside one byte). This is
not allowed for byte sequences greater than one byte, because then one would
need to specify the endianness of the multi-byte integer. Also, this is not
allowed for decimal numbers, since they would be confused with hex numbers
that are already allowed as byte strings. Neverthelss, single-byte hex
integers can be convienent:
frame[4] == 0xff
Slices can be combined. You can concatenate them using the comma operator:
ftp[1,3-5,9:] == 01:03:04:05:09:0a:0b
This concatenates offset 1, offsets 3-5, and offset 9 to the end of the ftp
data.
Type conversions¶
If a field is a text string or a byte array, it can be expressed in whichever
way is most convenient.
So, for instance, the following filters are equivalent:
http.request.method == "GET"
http.request.method == 47.45.54
A range can also be expressed in either way:
frame[60:2] gt 50.51
frame[60:2] gt "PQ"
Bit field operations¶
It is also possible to define tests with bit field operations. Currently the
following bit field operation is supported:
bitwise_and, & Bitwise AND
The bitwise AND operation allows testing to see if one or more bits are set.
Bitwise AND operates on integer protocol fields and slices.
When testing for TCP SYN packets, you can write:
tcp.flags & 0x02
That expression will match all packets that contain a "tcp.flags"
field with the 0x02 bit, i.e. the SYN bit, set.
Similarly, filtering for all WSP GET and extended GET methods is achieved with:
wsp.pdu_type & 0x40
When using slices, the bit mask must be specified as a byte string, and it must
have the same number of bytes as the slice itself, as in:
ip[42:2] & 40:ff
Logical expressions¶
Tests can be combined using logical expressions. These too are expressible in
C-like syntax or with English-like abbreviations:
and, && Logical AND
or, || Logical OR
not, ! Logical NOT
Expressions can be grouped by parentheses as well. The following are all valid
display filter expressions:
tcp.port == 80 and ip.src == 192.168.2.1
not llc
http and frame[100-199] contains "wireshark"
(ipx.src.net == 0xbad && ipx.src.node == 0.0.0.0.0.1) || ip
Remember that whenever a protocol or field name occurs in an expression, the
"exists" operator is implicitly called. The "exists"
operator has the highest priority. This means that the first filter expression
must be read as "show me the packets for which tcp.port exists and equals
80, and ip.src exists and equals 192.168.2.1". The second filter
expression means "show me the packets where not (llc exists)", or in
other words "where llc does not exist" and hence will match all
packets that do not contain the llc protocol. The third filter expression
includes the constraint that offset 199 in the frame exists, in other words
the length of the frame is at least 200.
A special caveat must be given regarding fields that occur more than once per
packet. "ip.addr" occurs twice per IP packet, once for the source
address, and once for the destination address. Likewise,
"tr.rif.ring" fields can occur more than once per packet. The
following two expressions are not equivalent:
ip.addr ne 192.168.4.1
not ip.addr eq 192.168.4.1
The first filter says "show me packets where an ip.addr exists that does
not equal 192.168.4.1". That is, as long as one ip.addr in the packet
does not equal 192.168.4.1, the packet passes the display filter. The other
ip.addr could equal 192.168.4.1 and the packet would still be displayed. The
second filter says "don't show me any packets that have an ip.addr field
equal to 192.168.4.1". If one ip.addr is 192.168.4.1, the packet does not
pass. If
neither ip.addr field is 192.168.4.1, then the packet is
displayed.
It is easy to think of the 'ne' and 'eq' operators as having an implicit
"exists" modifier when dealing with multiply-recurring fields.
"ip.addr ne 192.168.4.1" can be thought of as "there exists an
ip.addr that does not equal 192.168.4.1". "not ip.addr eq
192.168.4.1" can be thought of as "there does not exist an ip.addr
equal to 192.168.4.1".
Be careful with multiply-recurring fields; they can be confusing.
Care must also be taken when using the display filter to remove noise from the
packet trace. If, for example, you want to filter out all IP multicast packets
to address 224.1.2.3, then using:
ip.dst ne 224.1.2.3
may be too restrictive. Filtering with "ip.dst" selects only those
IP packets that satisfy the rule. Any other packets, including all
non-IP packets, will not be displayed. To display the non-IP packets as well,
you can use one of the following two expressions:
not ip or ip.dst ne 224.1.2.3
not ip.addr eq 224.1.2.3
The first filter uses "not ip" to include all non-IP packets and then
lets "ip.dst ne 224.1.2.3" filter out the unwanted IP packets. The
second filter has already been explained above where filtering with multiply
occurring fields was discussed.
FILTER FIELD REFERENCE¶
The entire list of display filters is too large to list here. You can can find
references and examples at the following locations:
- •
- The online Display Filter Reference:
<http://www.wireshark.org/docs/dfref/>
- •
- Help:Supported Protocols in Wireshark
- •
- "tshark -G fields" on the command line
- •
- The Wireshark wiki: <http://wiki.wireshark.org/DisplayFilters>
NOTES¶
The
wireshark-filters manpage is part of the
Wireshark
distribution. The latest version of
Wireshark can be found at
<
http://www.wireshark.org>.
Regular expressions in the "matches" operator are provided by GRegex
in GLib. See
<
http://developer.gnome.org/glib/2.32/glib-regex-syntax.html/> or
<
http://www.pcre.org/> for more information.
This manpage does not describe the capture filter syntax, which is different.
See the manual page of
pcap-filter(7) or, if that doesn't exist,
tcpdump(8), or, if that doesn't exist,
<
http://wiki.wireshark.org/CaptureFilters> for a description of capture
filters.
SEE ALSO¶
wireshark(1),
tshark(1),
editcap(1),
pcap(3),
pcap-filter(7) or
tcpdump(8) if it doesn't exist.
AUTHORS¶
See the list of authors in the
Wireshark man page for a list of authors
of that code.