forked from osmocom/wireshark
![Guy Harris](/assets/img/avatar_default.png)
Boolean value that's true if any of the bits in question are set and false if none of them are, not to an integer or slice value with the only the bits set in both values set. svn path=/trunk/; revision=14033
387 lines
13 KiB
Text
387 lines
13 KiB
Text
=head1 NAME
|
|
|
|
ethereal-filter - Ethereal filter syntax and reference
|
|
|
|
=head1 SYNOPSYS
|
|
|
|
B<ethereal> [other options]
|
|
S<[ B<-R> "filter expression" ]>
|
|
|
|
B<tethereal> [other options]
|
|
S<[ B<-R> "filter expression" ]>
|
|
|
|
=head1 DESCRIPTION
|
|
|
|
B<Ethereal> and B<Tethereal> 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 B<Ethereal>). This
|
|
manual page describes their syntax and provides a comprehensive reference of
|
|
filter fields.
|
|
|
|
=head1 FILTER SYNTAX
|
|
|
|
=head2 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 IPX protocol, the
|
|
filter would be "ipx" (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.
|
|
|
|
Note: all protocol and field names that are available in B<Ethereal> and
|
|
B<Tethereal> filters are listed in the B<FILTER PROTOCOL REFERENCE> (see
|
|
below).
|
|
|
|
=head2 Comparison operators
|
|
|
|
Fields can also be compared against values. The comparison operators
|
|
can be expressed either through C-like symbols or through English-like
|
|
abbreviations:
|
|
|
|
eq, == Equal
|
|
ne, != Not Equal
|
|
gt, > Greater Than
|
|
lt, < Less Than
|
|
ge, >= Greater than or Equal to
|
|
le, <= Less than or Equal to
|
|
|
|
=head2 Search and match operators
|
|
|
|
Additional operators exist expressed only in English, not punctuation:
|
|
|
|
contains Does the protocol, field or slice contain a value
|
|
matches Does the text string match the given Perl regular expression
|
|
|
|
The "contains" operator allows a filter to search for a sequence of
|
|
characters or bytes. For example, to search for a given HTTP
|
|
URL in a capture, the following filter can be used:
|
|
|
|
http contains "http://www.ethereal.com"
|
|
|
|
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 B<(?>optionB<)> construct. For instance, B<(?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
|
|
B<http://www.perldoc.com/perl5.8.0/pod/perlre.html>).
|
|
|
|
Note: the "matches" operator is only available if B<Ethereal> or B<Tethereal>
|
|
have been compiled with the PCRE library. This can be checked by running:
|
|
|
|
ethereal -v
|
|
tethereal -v
|
|
|
|
or selecting the "About Ethereal" item from the "Help" menu in B<Ethereal>.
|
|
|
|
=head2 Protocol field types
|
|
|
|
Each protocol field is typed. The types are:
|
|
|
|
Unsigned integer (8-bit, 16-bit, 24-bit, or 32-bit)
|
|
Signed integer (8-bit, 16-bit, 24-bit, or 32-bit)
|
|
Boolean
|
|
Ethernet address (6 bytes)
|
|
Byte array
|
|
IPv4 address
|
|
IPv6 address
|
|
IPX network number
|
|
Text string
|
|
Double-precision floating point number
|
|
|
|
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".
|
|
|
|
=head2 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 B<Ethereal> or B<Tethereal>.
|
|
|
|
token[0:5] ne 0.0.0.1.1
|
|
llc[0] eq aa
|
|
frame[100-199] contains "ethereal"
|
|
|
|
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 B<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
|
|
|
|
You can concatenate slices 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.
|
|
|
|
=head2 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"
|
|
|
|
=head2 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
|
|
|
|
=head2 Logical expressions
|
|
|
|
Tests can be combined using logical expressions.
|
|
These too are expressable 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 "ethereal"
|
|
(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 B<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 implict
|
|
"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
|
|
B<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 occuring fields was discussed.
|
|
|
|
=head1 FILTER PROTOCOL REFERENCE
|
|
|
|
Each entry below provides an abbreviated protocol or field name. Every
|
|
one of these fields can be used in a display filter. The type of the
|
|
field is also given.
|
|
|
|
=insert_dfilter_table
|
|
|
|
=head1 NOTES
|
|
|
|
The B<ethereal-filters> manpage is part of the B<Ethereal> distribution.
|
|
The latest version of B<Ethereal> can be found at
|
|
B<http://www.ethereal.com>.
|
|
|
|
Regular expressions in the "matches" operator are provided with B<libpcre>,
|
|
the Perl-Compatible Regular Expressions library: see B<http://www.pcre.org/>.
|
|
|
|
This manpage does not describe the capture filter syntax, which is
|
|
different. See the tcpdump(8) manpage for a description of capture
|
|
filters. Microsoft Windows versions use WinPcap from
|
|
B<http://winpcap.polito.it/> for which the capture filter syntax is described
|
|
in B<http://winpcap.polito.it/docs/man/html/group__language.html>.
|
|
|
|
=head1 SEE ALSO
|
|
|
|
I<ethereal(1)>, I<tethereal(1)>, I<editcap(1)>, I<tcpdump(8)>, I<pcap(3)>
|
|
|
|
=head1 AUTHORS
|
|
|
|
See the list of authors in the B<Ethereal> man page for a list of authors of
|
|
that code.
|