-.\" @(#) $Header: /tcpdump/master/tcpdump/Attic/tcpdump.1,v 1.109 2001-09-03 21:59:28 guy Exp $ (LBL)
+.\" @(#) $Header: /tcpdump/master/tcpdump/Attic/tcpdump.1,v 1.167.2.10 2005-12-05 20:11:19 guy Exp $ (LBL)
+.\"
+.\" $NetBSD: tcpdump.8,v 1.9 2003/03/31 00:18:17 perry Exp $
.\"
.\" Copyright (c) 1987, 1988, 1989, 1990, 1991, 1992, 1994, 1995, 1996, 1997
.\" The Regents of the University of California. All rights reserved.
.\" WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
.\"
-.TH TCPDUMP 1 "3 January 2001"
+.TH TCPDUMP 1 "18 April 2005"
.SH NAME
tcpdump \- dump traffic on a network
.SH SYNOPSIS
.na
.B tcpdump
[
-.B \-adeflnNOpqRStvxX
+.B \-AdDeflLnNOpqRStuUvxX
] [
.B \-c
.I count
+]
+.br
+.ti +8
+[
+.B \-C
+.I file_size
] [
.B \-F
.I file
.I module
]
[
-.B \-r
-.I file
+.B \-M
+.I secret
]
.br
.ti +8
[
+.B \-r
+.I file
+]
+[
.B \-s
.I snaplen
]
.br
.ti +8
[
+.B \-W
+.I filecount
+]
+.br
+.ti +8
+[
.B \-E
-.I algo:secret
+.I spi@ipaddr algo:secret,...
]
+.br
+.ti +8
+[
+.B \-y
+.I datalinktype
+]
+[
+.B \-Z
+.I user
+]
+.ti +8
[
.I expression
]
.ad
.SH DESCRIPTION
.LP
-\fITcpdump\fP prints out the headers of packets on a network interface
-that match the boolean \fIexpression\fP. It can also be run with the
+\fITcpdump\fP prints out a description of the contents of packets on a
+network interface that match the boolean \fIexpression\fP. It can also
+be run with the
.B \-w
flag, which causes it to save the packet data to a file for later
analysis, and/or with the
-.B \-b
+.B \-r
flag, which causes it to read from a saved packet file rather than to
read packets from a network interface. In all cases, only packets that
match
.I tcpdump
finishes capturing packets, it will report counts of:
.IP
+packets ``captured'' (this is the number of packets that
+.I tcpdump
+has received and processed);
+.IP
packets ``received by filter'' (the meaning of this depends on the OS on
which you're running
.IR tcpdump ,
and possibly on the way the OS was configured - if a filter was
specified on the command line, on some OSes it counts packets regardless
-of whether they were matched by the filter expression, and on other OSes
-it counts only packets that were matched by the filter expression and
-were processed by
+of whether they were matched by the filter expression and, even if they
+were matched by the filter expression, regardless of whether
+.I tcpdump
+has read and processed them yet, on other OSes it counts only packets that were
+matched by the filter expression regardless of whether
+.I tcpdump
+has read and processed them yet, and on other OSes it counts only
+packets that were matched by the filter expression and were processed by
.IR tcpdump );
.IP
packets ``dropped by kernel'' (this is the number of packets that were
is running, if the OS reports that information to applications; if not,
it will be reported as 0).
.LP
-On platforms that support the SIGINFO signal, such as most BSDs, it will
-report those counts when it receives a SIGINFO signal (generated, for
-example, by typing your ``status'' character, typically control-T) and
-will continue capturing packets.
+On platforms that support the SIGINFO signal, such as most BSDs
+(including Mac OS X) and Digital/Tru64 UNIX, it will report those counts
+when it receives a SIGINFO signal (generated, for example, by typing
+your ``status'' character, typically control-T, although on some
+platforms, such as Mac OS X, the ``status'' character is not set by
+default, so you must set it with
+.BR stty (1)
+in order to use it) and will continue capturing packets.
.LP
Reading packets from a network interface may require that you have
special privileges:
be root, or
.I tcpdump
must be installed setuid to root, in order to capture in promiscuous
-mode.
+mode. Note that, on many (perhaps all) interfaces, if you don't capture
+in promiscuous mode, you will not see any outgoing packets, so a capture
+not done in promiscuous mode may not be very useful.
.TP
.B Under HP-UX with DLPI:
You must be root or
.B Under Linux:
You must be root or
.I tcpdump
-must be installed setuid to root.
+must be installed setuid to root (unless your distribution has a kernel
+that supports capability bits such as CAP_NET_RAW and code to allow
+those capability bits to be given to particular accounts and to cause
+those bits to be set on a user's initial processes when they log in, in
+which case you must have CAP_NET_RAW in order to capture and
+CAP_NET_ADMIN to enumerate network devices with, for example, the
+.B \-D
+flag).
.TP
-.B Under Ultrix and Digital UNIX:
-Once the super-user has enabled promiscuous-mode operation using
-.IR pfconfig (8),
-any user may capture network traffic with
+.B Under ULTRIX and Digital UNIX/Tru64 UNIX:
+Any user may capture network traffic with
.IR tcpdump .
+However, no user (not even the super-user) can capture in promiscuous
+mode on an interface unless the super-user has enabled promiscuous-mode
+operation on that interface using
+.IR pfconfig (8),
+and no user (not even the super-user) can capture unicast traffic
+received by or sent by the machine on an interface unless the super-user
+has enabled copy-all-mode operation on that interface using
+.IR pfconfig ,
+so
+.I useful
+packet capture on an interface probably requires that either
+promiscuous-mode or copy-all-mode operation, or both modes of
+operation, be enabled on that interface.
.TP
-.B Under BSD:
+.B Under BSD (this includes Mac OS X):
You must have read access to
.IR /dev/bpf* .
+On BSDs with a devfs (this includes Mac OS X), this might involve more
+than just having somebody with super-user access setting the ownership
+or permissions on the BPF devices - it might involve configuring devfs
+to set the ownership or permissions every time the system is booted,
+if the system even supports that; if it doesn't support that, you might
+have to find some other way to make that happen at boot time.
.LP
Reading a saved packet file doesn't require special privileges.
.SH OPTIONS
.TP
-.B \-a
-Attempt to convert network and broadcast addresses to names.
+.B \-A
+Print each packet (minus its link level header) in ASCII. Handy for
+capturing web pages.
.TP
.B \-c
Exit after receiving \fIcount\fP packets.
.TP
+.B \-C
+Before writing a raw packet to a savefile, check whether the file is
+currently larger than \fIfile_size\fP and, if so, close the current
+savefile and open a new one. Savefiles after the first savefile will
+have the name specified with the
+.B \-w
+flag, with a number after it, starting at 1 and continuing upward.
+The units of \fIfile_size\fP are millions of bytes (1,000,000 bytes,
+not 1,048,576 bytes).
+.TP
.B \-d
Dump the compiled packet-matching code in a human readable form to
standard output and stop.
.B \-ddd
Dump packet-matching code as decimal numbers (preceded with a count).
.TP
+.B \-D
+Print the list of the network interfaces available on the system and on
+which
+.I tcpdump
+can capture packets. For each network interface, a number and an
+interface name, possibly followed by a text description of the
+interface, is printed. The interface name or the number can be supplied
+to the
+.B \-i
+flag to specify an interface on which to capture.
+.IP
+This can be useful on systems that don't have a command to list them
+(e.g., Windows systems, or UNIX systems lacking
+.BR "ifconfig \-a" );
+the number can be useful on Windows 2000 and later systems, where the
+interface name is a somewhat complex string.
+.IP
+The
+.B \-D
+flag will not be supported if
+.I tcpdump
+was built with an older version of
+.I libpcap
+that lacks the
+.B pcap_findalldevs()
+function.
+.TP
.B \-e
Print the link-level header on each dump line.
.TP
.B \-E
-Use \fIalgo:secret\fP for decrypting IPsec ESP packets.
+Use \fIspi@ipaddr algo:secret\fP for decrypting IPsec ESP packets that
+are addressed to \fIaddr\fP and contain Security Parameter Index value
+\fIspi\fP. This combination may be repeated with comma or newline seperation.
+.IP
+Note that setting the secret for IPv4 ESP packets is supported at this time.
+.IP
Algorithms may be
\fBdes-cbc\fP,
\fB3des-cbc\fP,
The default is \fBdes-cbc\fP.
The ability to decrypt packets is only present if \fItcpdump\fP was compiled
with cryptography enabled.
-\fIsecret\fP the ascii text for ESP secret key.
-We cannot take arbitrary binary value at this moment.
+.IP
+\fIsecret\fP is the ASCII text for ESP secret key.
+If preceeded by 0x, then a hex value will be read.
+.IP
The option assumes RFC2406 ESP, not RFC1827 ESP.
The option is only for debugging purposes, and
-the use of this option with truly `secret' key is discouraged.
+the use of this option with a true `secret' key is discouraged.
By presenting IPsec secret key onto command line
you make it visible to others, via
.IR ps (1)
and other occasions.
+.IP
+In addition to the above syntax, the syntax \fIfile name\fP may be used
+to have tcpdump read the provided file in. The file is opened upon
+receiving the first ESP packet, so any special permissions that tcpdump
+may have been given should already have been given up.
.TP
.B \-f
-Print `foreign' internet addresses numerically rather than symbolically
+Print `foreign' IPv4 addresses numerically rather than symbolically
(this option is intended to get around serious brain damage in
-Sun's yp server \(em usually it hangs forever translating non-local
+Sun's NIS server \(em usually it hangs forever translating non-local
internet numbers).
+.IP
+The test for `foreign' IPv4 addresses is done using the IPv4 address and
+netmask of the interface on which capture is being done. If that
+address or netmask are not available, available, either because the
+interface on which capture is being done has no address or netmask or
+because the capture is being done on the Linux "any" interface, which
+can capture on more than one interface, this option will not work
+correctly.
.TP
.B \-F
Use \fIfile\fP as input for the filter expression.
argument of ``any'' can be used to capture packets from all interfaces.
Note that captures on the ``any'' device will not be done in promiscuous
mode.
+.IP
+If the
+.B \-D
+flag is supported, an interface number as printed by that flag can be
+used as the
+.I interface
+argument.
.TP
.B \-l
Make stdout line buffered.
``tcpdump\ \ \-l\ \ |\ \ tee dat'' or
``tcpdump\ \ \-l \ \ > dat\ \ &\ \ tail\ \ \-f\ \ dat''.
.TP
+.B \-L
+List the known data link types for the interface and exit.
+.TP
+.B \-m
+Load SMI MIB module definitions from file \fImodule\fR.
+This option
+can be used several times to load several MIB modules into \fItcpdump\fP.
+.TP
+.B \-M
+Use \fIsecret\fP as a shared secret for validating the digests found in
+TCP segments with the TCP-MD5 option (RFC 2385), if present.
+.TP
.B \-n
Don't convert addresses (i.e., host addresses, port numbers, etc.) to names.
.TP
if you give this flag then \fItcpdump\fP will print ``nic''
instead of ``nic.ddn.mil''.
.TP
-.B \-m
-Load SMI MIB module definitions from file \fImodule\fR.
-This option
-can be used several times to load several MIB modules into \fItcpdump\fP.
-.TP
.B \-O
Do not run the packet-matching code optimizer.
This is useful only
Print less protocol information so output
lines are shorter.
.TP
+.B \-R
+Assume ESP/AH packets to be based on old specification (RFC1825 to RFC1829).
+If specified, \fItcpdump\fP will not print replay prevention field.
+Since there is no protocol version field in ESP/AH specification,
+\fItcpdump\fP cannot deduce the version of ESP/AH protocol.
+.TP
.B \-r
-Read packets from \fIfile\fR (which was created with the -w option).
+Read packets from \fIfile\fR (which was created with the
+.B \-w
+option).
Standard input is used if \fIfile\fR is ``-''.
.TP
+.B \-S
+Print absolute, rather than relative, TCP sequence numbers.
+.TP
.B \-s
Snarf \fIsnaplen\fP bytes of data from each packet rather than the
default of 68 (with SunOS's NIT, the minimum is actually 96).
Force packets selected by "\fIexpression\fP" to be interpreted the
specified \fItype\fR.
Currently known types are
+\fBaodv\fR (Ad-hoc On-demand Distance Vector protocol),
\fBcnfp\fR (Cisco NetFlow protocol),
\fBrpc\fR (Remote Procedure Call),
\fBrtp\fR (Real-Time Applications protocol),
\fBrtcp\fR (Real-Time Applications control protocol),
\fBsnmp\fR (Simple Network Management Protocol),
+\fBtftp\fR (Trivial File Transfer Protocol),
\fBvat\fR (Visual Audio Tool),
and
\fBwb\fR (distributed White Board).
.TP
-.B \-R
-Assume ESP/AH packets to be based on old specification (RFC1825 to RFC1829).
-If specified, \fItcpdump\fP will not print replay prevention field.
-Since there is no protocol version field in ESP/AH specification,
-\fItcpdump\fP cannot deduce the version of ESP/AH protocol.
-.TP
-.B \-S
-Print absolute, rather than relative, TCP sequence numbers.
-.TP
.B \-t
\fIDon't\fP print a timestamp on each dump line.
.TP
.B \-tttt
Print a timestamp in default format proceeded by date on each dump line.
.TP
+.B \-u
+Print undecoded NFS handles.
+.TP
+.B \-U
+Make output saved via the
+.B \-w
+option ``packet-buffered''; i.e., as each packet is saved, it will be
+written to the output file, rather than being written only when the
+output buffer fills.
+.IP
+The
+.B \-U
+flag will not be supported if
+.I tcpdump
+was built with an older version of
+.I libpcap
+that lacks the
+.B pcap_dump_flush()
+function.
+.TP
.B \-v
-(Slightly more) verbose output.
+When parsing and printing, produce (slightly more) verbose output.
For example, the time to live,
identification, total length and options in an IP packet are printed.
Also enables additional packet integrity checks such as verifying the
IP and ICMP header checksum.
+.IP
+When writing to a file with the
+.B \-w
+option, report, every 10 seconds, the number of packets captured.
.TP
.B \-vv
Even more verbose output.
are printed in full.
With
.B \-X
-telnet options are printed in hex as well.
+Telnet options are printed in hex as well.
.TP
.B \-w
Write the raw packets to \fIfile\fR rather than parsing and printing
They can later be printed with the \-r option.
Standard output is used if \fIfile\fR is ``-''.
.TP
+.B \-W
+Used in conjunction with the
+.B \-C
+option, this will limit the number
+of files created to the specified number, and begin overwriting files
+from the beginning, thus creating a 'rotating' buffer.
+In addition, it will name
+the files with enough leading 0s to support the maximum number of
+files, allowing them to sort correctly.
+.TP
.B \-x
-Print each packet (minus its link level header) in hex.
+When parsing and printing,
+in addition to printing the headers of each packet, print the data of
+each packet (minus its link level header) in hex.
The smaller of the entire packet or
.I snaplen
-bytes will be printed.
+bytes will be printed. Note that this is the entire link-layer
+packet, so for link layers that pad (e.g. Ethernet), the padding bytes
+will also be printed when the higher layer packet is shorter than the
+required padding.
+.TP
+.B \-xx
+When parsing and printing,
+in addition to printing the headers of each packet, print the data of
+each packet,
+.I including
+its link level header, in hex.
.TP
.B \-X
-When printing hex, print ascii too.
-Thus if
-.B \-x
-is also set, the packet is printed in hex/ascii.
+When parsing and printing,
+in addition to printing the headers of each packet, print the data of
+each packet (minus its link level header) in hex and ASCII.
This is very handy for analysing new protocols.
-Even if
-.B \-x
-is not also set, some parts of some packets may be printed
-in hex/ascii.
+.TP
+.B \-XX
+When parsing and printing,
+in addition to printing the headers of each packet, print the data of
+each packet,
+.I including
+its link level header, in hex and ASCII.
+.TP
+.B \-y
+Set the data link type to use while capturing packets to \fIdatalinktype\fP.
+.TP
+.B \-Z
+Drops privileges (if root) and changes user ID to
+.I user
+and the group ID to the primary group of
+.IR user .
+.IP
+This behavior can also be enabled by default at compile time.
.IP "\fI expression\fP"
.RS
selects which packets will be dumped.
qualifiers say what kind of thing the id name or number refers to.
Possible types are
.BR host ,
-.B net
+.B net ,
+.B port
and
-.BR port .
-E.g., `host foo', `net 128.3', `port 20'.
+.BR portrange .
+E.g., `host foo', `net 128.3', `port 20', `portrange 6000-6008'.
If there is no type
qualifier,
.B host
there is no dir qualifier,
.B "src or dst"
is assumed.
-For `null' link layers (i.e. point to point protocols such as slip) the
+For some link layers, such as SLIP and the ``cooked'' Linux capture mode
+used for the ``any'' device and for some other device types, the
.B inbound
and
.B outbound
.BR ether ,
.BR fddi ,
.BR tr ,
+.BR wlan ,
.BR ip ,
.BR ip6 ,
.BR arp ,
.B tcp
and
.BR udp .
-E.g., `ether src foo', `arp net 128.3', `tcp port 21'.
+E.g., `ether src foo', `arp net 128.3', `tcp port 21', `udp portrange
+7000-7009'.
If there is
no proto qualifier, all protocols consistent with the type are
assumed.
FDDI headers also contain other fields,
but you cannot name them explicitly in a filter expression.
.LP
-Similarly, `tr' is an alias for `ether'; the previous paragraph's
-statements about FDDI headers also apply to Token Ring headers.]
+Similarly, `tr' and `wlan' are aliases for `ether'; the previous
+paragraph's statements about FDDI headers also apply to Token Ring
+and 802.11 wireless LAN headers. For 802.11 headers, the destination
+address is the DA field and the source address is the SA field; the
+BSSID, RA, and TA fields aren't tested.]
.LP
In addition to the above, there are some special `primitive' keywords
that don't follow the pattern:
True if the IPv4/v6 source field of the packet is \fIhost\fP.
.IP "\fBhost \fIhost\fP
True if either the IPv4/v6 source or destination of the packet is \fIhost\fP.
+.IP
Any of the above host expressions can be prepended with the keywords,
\fBip\fP, \fBarp\fP, \fBrarp\fP, or \fBip6\fP as in:
.in +.5i
If \fIhost\fR is a name with multiple IP addresses, each address will
be checked for a match.
.IP "\fBether dst \fIehost\fP
-True if the ethernet destination address is \fIehost\fP.
+True if the Ethernet destination address is \fIehost\fP.
\fIEhost\fP
may be either a name from /etc/ethers or a number (see
.IR ethers (3N)
for numeric format).
.IP "\fBether src \fIehost\fP
-True if the ethernet source address is \fIehost\fP.
+True if the Ethernet source address is \fIehost\fP.
.IP "\fBether host \fIehost\fP
-True if either the ethernet source or destination address is \fIehost\fP.
+True if either the Ethernet source or destination address is \fIehost\fP.
.IP "\fBgateway\fP \fIhost\fP
True if the packet used \fIhost\fP as a gateway.
-I.e., the ethernet
+I.e., the Ethernet
source or destination address was \fIhost\fP but neither the IP source
nor the IP destination was \fIhost\fP.
\fIHost\fP must be a name and
.IP "\fBdst net \fInet\fR"
True if the IPv4/v6 destination address of the packet has a network
number of \fInet\fP.
-\fINet\fP may be either a name from /etc/networks
-or a network number (see \fInetworks(4)\fP for details).
+\fINet\fP may be either a name from the networks database
+(/etc/networks, etc.) or a network number.
+An IPv4 network number can be written as a dotted quad (e.g., 192.168.1.0),
+dotted triple (e.g., 192.168.1), dotted pair (e.g, 172.16), or single
+number (e.g., 10); the netmask is 255.255.255.255 for a dotted quad
+(which means that it's really a host match), 255.255.255.0 for a dotted
+triple, 255.255.0.0 for a dotted pair, or 255.0.0.0 for a single number.
+An IPv6 network number must be written out fully; the netmask is
+ff:ff:ff:ff:ff:ff:ff:ff, so IPv6 "network" matches are really always
+host matches, and a network match requires a netmask length.
.IP "\fBsrc net \fInet\fR"
True if the IPv4/v6 source address of the packet has a network
number of \fInet\fP.
True if either the IPv4/v6 source or destination address of the packet has a network
number of \fInet\fP.
.IP "\fBnet \fInet\fR \fBmask \fInetmask\fR"
-True if the IP address matches \fInet\fR with the specific \fInetmask\fR.
+True if the IPv4 address matches \fInet\fR with the specific \fInetmask\fR.
May be qualified with \fBsrc\fR or \fBdst\fR.
Note that this syntax is not valid for IPv6 \fInet\fR.
.IP "\fBnet \fInet\fR/\fIlen\fR"
True if the packet has a source port value of \fIport\fP.
.IP "\fBport \fIport\fR"
True if either the source or destination port of the packet is \fIport\fP.
-Any of the above port expressions can be prepended with the keywords,
-\fBtcp\fP or \fBudp\fP, as in:
+.IP "\fBdst portrange \fIport1\fB-\fIport2\fR"
+True if the packet is ip/tcp, ip/udp, ip6/tcp or ip6/udp and has a
+destination port value between \fIport1\fP and \fIport2\fP.
+.I port1
+and
+.I port2
+are interpreted in the same fashion as the
+.I port
+parameter for
+.BR port .
+.IP "\fBsrc portrange \fIport1\fB-\fIport2\fR"
+True if the packet has a source port value between \fIport1\fP and
+\fIport2\fP.
+.IP "\fBportrange \fIport1\fB-\fIport2\fR"
+True if either the source or destination port of the packet is between
+\fIport1\fP and \fIport2\fP.
+.IP
+Any of the above port or port range expressions can be prepended with
+the keywords, \fBtcp\fP or \fBudp\fP, as in:
.in +.5i
.nf
\fBtcp src port \fIport\fR
.fi
.in -.5i
.IP "\fBip proto \fIprotocol\fR"
-True if the packet is an IP packet (see
+True if the packet is an IPv4 packet (see
.IR ip (4P))
of protocol type \fIprotocol\fP.
\fIProtocol\fP can be a number or one of the names
-\fIicmp\fP, \fIicmp6\fP, \fIigmp\fP, \fIigrp\fP, \fIpim\fP, \fIah\fP,
-\fIesp\fP, \fIvrrp\fP, \fIudp\fP, or \fItcp\fP.
-Note that the identifiers \fItcp\fP, \fIudp\fP, and \fIicmp\fP are also
+\fBicmp\fP, \fBicmp6\fP, \fBigmp\fP, \fBigrp\fP, \fBpim\fP, \fBah\fP,
+\fBesp\fP, \fBvrrp\fP, \fBudp\fP, or \fBtcp\fP.
+Note that the identifiers \fBtcp\fP, \fBudp\fP, and \fBicmp\fP are also
keywords and must be escaped via backslash (\\), which is \\\\ in the C-shell.
Note that this primitive does not chase the protocol header chain.
.IP "\fBip6 proto \fIprotocol\fR"
.IP "\fBip protochain \fIprotocol\fR"
Equivalent to \fBip6 protochain \fIprotocol\fR, but this is for IPv4.
.IP "\fBether broadcast\fR"
-True if the packet is an ethernet broadcast packet.
+True if the packet is an Ethernet broadcast packet.
The \fIether\fP
keyword is optional.
.IP "\fBip broadcast\fR"
-True if the packet is an IP broadcast packet.
-It checks for both
-the all-zeroes and all-ones broadcast conventions, and looks up
-the local subnet mask.
+True if the packet is an IPv4 broadcast packet.
+It checks for both the all-zeroes and all-ones broadcast conventions,
+and looks up the subnet mask on the interface on which the capture is
+being done.
+.IP
+If the subnet mask of the interface on which the capture is being done
+is not available, either because the interface on which capture is being
+done has no netmask or because the capture is being done on the Linux
+"any" interface, which can capture on more than one interface, this
+check will not work correctly.
.IP "\fBether multicast\fR"
-True if the packet is an ethernet multicast packet.
-The \fIether\fP
+True if the packet is an Ethernet multicast packet.
+The \fBether\fP
keyword is optional.
This is shorthand for `\fBether[0] & 1 != 0\fP'.
.IP "\fBip multicast\fR"
-True if the packet is an IP multicast packet.
+True if the packet is an IPv4 multicast packet.
.IP "\fBip6 multicast\fR"
True if the packet is an IPv6 multicast packet.
.IP "\fBether proto \fIprotocol\fR"
True if the packet is of ether type \fIprotocol\fR.
\fIProtocol\fP can be a number or one of the names
-\fIip\fP, \fIip6\fP, \fIarp\fP, \fIrarp\fP, \fIatalk\fP, \fIaarp\fP,
-\fIdecnet\fP, \fIsca\fP, \fIlat\fP, \fImopdl\fP, \fImoprc\fP,
-\fIiso\fP, \fIstp\fP, \fIipx\fP, or \fInetbeui\fP.
+\fBip\fP, \fBip6\fP, \fBarp\fP, \fBrarp\fP, \fBatalk\fP, \fBaarp\fP,
+\fBdecnet\fP, \fBsca\fP, \fBlat\fP, \fBmopdl\fP, \fBmoprc\fP,
+\fBiso\fP, \fBstp\fP, \fBipx\fP, or \fBnetbeui\fP.
Note these identifiers are also keywords
and must be escaped via backslash (\\).
.IP
-[In the case of FDDI (e.g., `\fBfddi protocol arp\fR') and Token Ring
-(e.g., `\fBtr protocol arp\fR'), for most of those protocols, the
+[In the case of FDDI (e.g., `\fBfddi protocol arp\fR'), Token Ring
+(e.g., `\fBtr protocol arp\fR'), and IEEE 802.11 wireless LANS (e.g.,
+`\fBwlan protocol arp\fR'), for most of those protocols, the
protocol identification comes from the 802.2 Logical Link Control (LLC)
-header, which is usually layered on top of the FDDI or Token Ring
-header.
+header, which is usually layered on top of the FDDI, Token Ring, or
+802.11 header.
.IP
-When filtering for most protocol identifiers on FDDI or Token Ring,
-\fItcpdump\fR checks only the protocol ID field of an LLC header in
-so-called SNAP format with an Organizational Unit Identifier (OUI) of
+When filtering for most protocol identifiers on FDDI, Token Ring, or
+802.11, \fItcpdump\fR checks only the protocol ID field of an LLC header
+in so-called SNAP format with an Organizational Unit Identifier (OUI) of
0x000000, for encapsulated Ethernet; it doesn't check whether the packet
is in SNAP format with an OUI of 0x000000.
-.IP
-The exceptions are \fIiso\fP, for which it checks the DSAP (Destination
-Service Access Point) and SSAP (Source Service Access Point) fields of
-the LLC header, \fIstp\fP and \fInetbeui\fP, where it checks the DSAP of
-the LLC header, and \fIatalk\fP, where it checks for a SNAP-format
-packet with an OUI of 0x080007 and the Appletalk etype.
+The exceptions are:
+.RS
+.TP
+\fBiso\fP
+\fItcpdump\fR checks the DSAP (Destination Service Access Point) and
+SSAP (Source Service Access Point) fields of the LLC header;
+.TP
+\fBstp\fP and \fBnetbeui\fP
+\fItcpdump\fR checks the DSAP of the LLC header;
+.TP
+\fBatalk\fP
+\fItcpdump\fR checks for a SNAP-format packet with an OUI of 0x080007
+and the AppleTalk etype.
+.RE
.IP
In the case of Ethernet, \fItcpdump\fR checks the Ethernet type field
-for most of those protocols; the exceptions are \fIiso\fP, \fIsap\fP,
-and \fInetbeui\fP, for which it checks for an 802.3 frame and then
-checks the LLC header as it does for FDDI and Token Ring, \fIatalk\fP,
-where it checks both for the Appletalk etype in an Ethernet frame and
-for a SNAP-format packet as it does for FDDI and Token Ring, \fIaarp\fP,
-where it checks for the Appletalk ARP etype in either an Ethernet frame
-or an 802.2 SNAP frame with an OUI of 0x000000, and \fIipx\fP, where it
-checks for the IPX etype in an Ethernet frame, the IPX DSAP in the LLC
-header, the 802.3 with no LLC header encapsulation of IPX, and the IPX
-etype in a SNAP frame.]
+for most of those protocols. The exceptions are:
+.RS
+.TP
+\fBiso\fP, \fBstp\fP, and \fBnetbeui\fP
+\fItcpdump\fR checks for an 802.3 frame and then checks the LLC header as
+it does for FDDI, Token Ring, and 802.11;
+.TP
+\fBatalk\fP
+\fItcpdump\fR checks both for the AppleTalk etype in an Ethernet frame and
+for a SNAP-format packet as it does for FDDI, Token Ring, and 802.11;
+.TP
+\fBaarp\fP
+\fItcpdump\fR checks for the AppleTalk ARP etype in either an Ethernet
+frame or an 802.2 SNAP frame with an OUI of 0x000000;
+.TP
+\fBipx\fP
+\fItcpdump\fR checks for the IPX etype in an Ethernet frame, the IPX
+DSAP in the LLC header, the 802.3-with-no-LLC-header encapsulation of
+IPX, and the IPX etype in a SNAP frame.
+.RE
.IP "\fBdecnet src \fIhost\fR"
True if the DECNET source address is
.IR host ,
which may be an address of the form ``10.123'', or a DECNET host
name.
-[DECNET host name support is only available on Ultrix systems
+[DECNET host name support is only available on ULTRIX systems
that are configured to run DECNET.]
.IP "\fBdecnet dst \fIhost\fR"
True if the DECNET destination address is
.IP "\fBdecnet host \fIhost\fR"
True if either the DECNET source or destination address is
.IR host .
+.IP "\fBifname \fIinterface\fR"
+True if the packet was logged as coming from the specified interface (applies
+only to packets logged by OpenBSD's
+.BR pf (4)).
+.IP "\fBon \fIinterface\fR"
+Synonymous with the
+.B ifname
+modifier.
+.IP "\fBrnr \fInum\fR"
+True if the packet was logged as matching the specified PF rule number
+(applies only to packets logged by OpenBSD's
+.BR pf (4)).
+.IP "\fBrulenum \fInum\fR"
+Synonomous with the
+.B rnr
+modifier.
+.IP "\fBreason \fIcode\fR"
+True if the packet was logged with the specified PF reason code. The known
+codes are:
+.BR match ,
+.BR bad-offset ,
+.BR fragment ,
+.BR short ,
+.BR normalize ,
+and
+.B memory
+(applies only to packets logged by OpenBSD's
+.BR pf (4)).
+.IP "\fBrset \fIname\fR"
+True if the packet was logged as matching the specified PF ruleset
+name of an anchored ruleset (applies only to packets logged by
+.BR pf (4)).
+.IP "\fBruleset \fIname\fR"
+Synonomous with the
+.B rset
+modifier.
+.IP "\fBsrnr \fInum\fR"
+True if the packet was logged as matching the specified PF rule number
+of an anchored ruleset (applies only to packets logged by
+.BR pf (4)).
+.IP "\fBsubrulenum \fInum\fR"
+Synonomous with the
+.B srnr
+modifier.
+.IP "\fBaction \fIact\fR"
+True if PF took the specified action when the packet was logged. Known actions
+are:
+.B pass
+and
+.B block
+(applies only to packets logged by OpenBSD's
+.BR pf (4)).
.IP "\fBip\fR, \fBip6\fR, \fBarp\fR, \fBrarp\fR, \fBatalk\fR, \fBaarp\fR, \fBdecnet\fR, \fBiso\fR, \fBstp\fR, \fBipx\fR, \fInetbeui\fP"
Abbreviations for:
.in +.5i
\fItcpdump\fP does not currently know how to parse these protocols.
.IP "\fBvlan \fI[vlan_id]\fR"
True if the packet is an IEEE 802.1Q VLAN packet.
-If \fI[vlan_id]\fR is specified, only true is the packet has the specified
+If \fI[vlan_id]\fR is specified, only true if the packet has the specified
\fIvlan_id\fR.
Note that the first \fBvlan\fR keyword encountered in \fIexpression\fR
-changes the decoding offsets for the remainder of \fIexpression\fR
-on the assumption that the packet is a VLAN packet.
+changes the decoding offsets for the remainder of \fIexpression\fR on
+the assumption that the packet is a VLAN packet. The \fBvlan
+\fI[vlan_id]\fR expression may be used more than once, to filter on VLAN
+hierarchies. Each use of that expression increments the filter offsets
+by 4.
+.IP
+For example:
+.in +.5i
+.nf
+\fBvlan 100 && vlan 200\fR
+.fi
+.in -.5i
+filters on VLAN 200 encapsulated within VLAN 100, and
+.in +.5i
+.nf
+\fBvlan && vlan 300 && ip\fR
+.fi
+.in -.5i
+filters IPv4 protocols encapsulated in VLAN 300 encapsulated within any
+higher order VLAN.
+.IP "\fBmpls \fI[label_num]\fR"
+True if the packet is an MPLS packet.
+If \fI[label_num]\fR is specified, only true is the packet has the specified
+\fIlabel_num\fR.
+Note that the first \fBmpls\fR keyword encountered in \fIexpression\fR
+changes the decoding offsets for the remainder of \fIexpression\fR on
+the assumption that the packet is a MPLS-encapsulated IP packet. The
+\fBmpls \fI[label_num]\fR expression may be used more than once, to
+filter on MPLS hierarchies. Each use of that expression increments the
+filter offsets by 4.
+.IP
+For example:
+.in +.5i
+.nf
+\fBmpls 100000 && mpls 1024\fR
+.fi
+.in -.5i
+filters packets with an outer label of 100000 and an inner label of
+1024, and
+.in +.5i
+.nf
+\fBmpls && mpls 1024 && host 192.9.200.1\fR
+.fi
+.in -.5i
+filters packets to or from 192.9.200.1 with an inner label of 1024 and
+any outer label.
+.IP \fBpppoed\fP
+True if the packet is a PPP-over-Ethernet Discovery packet (Ethernet
+type 0x8863).
+.IP \fBpppoes\fP
+True if the packet is a PPP-over-Ethernet Session packet (Ethernet
+type 0x8864).
+Note that the first \fBpppoes\fR keyword encountered in \fIexpression\fR
+changes the decoding offsets for the remainder of \fIexpression\fR on
+the assumption that the packet is a PPPoE session packet.
+.IP
+For example:
+.in +.5i
+.nf
+\fBpppoes && ip\fR
+.fi
+.in -.5i
+filters IPv4 protocols encapsulated in PPPoE.
.IP "\fBtcp\fR, \fBudp\fR, \fBicmp\fR"
Abbreviations for:
.in +.5i
.IP "\fBiso proto \fIprotocol\fR"
True if the packet is an OSI packet of protocol type \fIprotocol\fP.
\fIProtocol\fP can be a number or one of the names
-\fIclnp\fP, \fIesis\fP, or \fIisis\fP.
+\fBclnp\fP, \fBesis\fP, or \fBisis\fP.
.IP "\fBclnp\fR, \fBesis\fR, \fBisis\fR"
Abbreviations for:
.in +.5i
.fi
.in -.5i
where \fIp\fR is one of the above protocols.
-Note that \fItcpdump\fR does an incomplete job of parsing these protocols.
+.IP "\fBl1\fR, \fBl2\fR, \fBiih\fR, \fBlsp\fR, \fBsnp\fR, \fBcsnp\fR, \fBpsnp\fR"
+Abbreviations for IS-IS PDU types.
+.IP "\fBvpi\fP \fIn\fR
+True if the packet is an ATM packet, for SunATM on Solaris, with a
+virtual path identifier of
+.IR n .
+.IP "\fBvci\fP \fIn\fR
+True if the packet is an ATM packet, for SunATM on Solaris, with a
+virtual channel identifier of
+.IR n .
+.IP \fBlane\fP
+True if the packet is an ATM packet, for SunATM on Solaris, and is
+an ATM LANE packet.
+Note that the first \fBlane\fR keyword encountered in \fIexpression\fR
+changes the tests done in the remainder of \fIexpression\fR
+on the assumption that the packet is either a LANE emulated Ethernet
+packet or a LANE LE Control packet. If \fBlane\fR isn't specified, the
+tests are done under the assumption that the packet is an
+LLC-encapsulated packet.
+.IP \fBllc\fP
+True if the packet is an ATM packet, for SunATM on Solaris, and is
+an LLC-encapsulated packet.
+.IP \fBoamf4s\fP
+True if the packet is an ATM packet, for SunATM on Solaris, and is
+a segment OAM F4 flow cell (VPI=0 & VCI=3).
+.IP \fBoamf4e\fP
+True if the packet is an ATM packet, for SunATM on Solaris, and is
+an end-to-end OAM F4 flow cell (VPI=0 & VCI=4).
+.IP \fBoamf4\fP
+True if the packet is an ATM packet, for SunATM on Solaris, and is
+a segment or end-to-end OAM F4 flow cell (VPI=0 & (VCI=3 | VCI=4)).
+.IP \fBoam\fP
+True if the packet is an ATM packet, for SunATM on Solaris, and is
+a segment or end-to-end OAM F4 flow cell (VPI=0 & (VCI=3 | VCI=4)).
+.IP \fBmetac\fP
+True if the packet is an ATM packet, for SunATM on Solaris, and is
+on a meta signaling circuit (VPI=0 & VCI=1).
+.IP \fBbcc\fP
+True if the packet is an ATM packet, for SunATM on Solaris, and is
+on a broadcast signaling circuit (VPI=0 & VCI=2).
+.IP \fBsc\fP
+True if the packet is an ATM packet, for SunATM on Solaris, and is
+on a signaling circuit (VPI=0 & VCI=5).
+.IP \fBilmic\fP
+True if the packet is an ATM packet, for SunATM on Solaris, and is
+on an ILMI circuit (VPI=0 & VCI=16).
+.IP \fBconnectmsg\fP
+True if the packet is an ATM packet, for SunATM on Solaris, and is
+on a signaling circuit and is a Q.2931 Setup, Call Proceeding, Connect,
+Connect Ack, Release, or Release Done message.
+.IP \fBmetaconnect\fP
+True if the packet is an ATM packet, for SunATM on Solaris, and is
+on a meta signaling circuit and is a Q.2931 Setup, Call Proceeding, Connect,
+Release, or Release Done message.
.IP "\fIexpr relop expr\fR"
-True if the relation holds, where \fIrelop\fR is one of >, <, >=, <=, =, !=,
-and \fIexpr\fR is an arithmetic expression composed of integer constants
-(expressed in standard C syntax), the normal binary operators
-[+, -, *, /, &, |], a length operator, and special packet data accessors.
+True if the relation holds, where \fIrelop\fR is one of >, <, >=, <=, =,
+!=, and \fIexpr\fR is an arithmetic expression composed of integer
+constants (expressed in standard C syntax), the normal binary operators
+[+, -, *, /, &, |, <<, >>], a length operator, and special packet data
+accessors. Note that all comparisons are unsigned, so that, for example,
+0x80000000 and 0xffffffff are > 0.
To access
data inside the packet, use the following syntax:
.in +.5i
\fIproto\fB [ \fIexpr\fB : \fIsize\fB ]\fR
.fi
.in -.5i
-\fIProto\fR is one of \fBether, fddi, tr,
-ip, arp, rarp, tcp, udp, icmp\fR or \fBip6\fR, and
+\fIProto\fR is one of \fBether, fddi, tr, wlan, ppp, slip, link,
+ip, arp, rarp, tcp, udp, icmp, ip6\fR or \fBradio\fR, and
indicates the protocol layer for the index operation.
+(\fBether, fddi, wlan, tr, ppp, slip\fR and \fBlink\fR all refer to the
+link layer. \fBradio\fR refers to the "radio header" added to some
+802.11 captures.)
Note that \fItcp, udp\fR and other upper-layer protocol types only
apply to IPv4, not IPv6 (this will be fixed in the future).
The byte offset, relative to the indicated protocol layer, is
For example, `\fBether[0] & 1 != 0\fP' catches all multicast traffic.
The expression `\fBip[0] & 0xf != 5\fP'
-catches all IP packets with options.
+catches all IPv4 packets with options.
The expression
`\fBip[6:2] & 0x1fff = 0\fP'
-catches only unfragmented datagrams and frag zero of fragmented datagrams.
+catches only unfragmented IPv4 datagrams and frag zero of fragmented
+IPv4 datagrams.
This check is implicitly applied to the \fBtcp\fP and \fBudp\fP
index operations.
For instance, \fBtcp[0]\fP always means the first
\fBicmp-maskreq\fP, \fBicmp-maskreply\fP.
The following TCP flags field values are available: \fBtcp-fin\fP,
-\fBtcp-syn\fP, \fBtcp-rst\fP, \fBtcp-push\fP, \fBtcp-push\fP,
+\fBtcp-syn\fP, \fBtcp-rst\fP, \fBtcp-push\fP,
\fBtcp-ack\fP, \fBtcp-urg\fP.
.LP
Primitives may be combined using:
.fi
.RE
.LP
+To print all IPv4 HTTP packets to and from port 80, i.e. print only
+packets that contain data, not, for example, SYN and FIN packets and
+ACK-only packets. (IPv6 is left as an exercise for the reader.)
+.RS
+.nf
+.B
+tcpdump 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)'
+.fi
+.RE
+.LP
To print IP packets longer than 576 bytes sent through gateway \fIsnup\fP:
.RS
.nf
.LP
To print IP broadcast or multicast packets that were
.I not
-sent via ethernet broadcast or multicast:
+sent via Ethernet broadcast or multicast:
.RS
.nf
.B
Link Level Headers
.LP
If the '-e' option is given, the link level header is printed out.
-On ethernets, the source and destination addresses, protocol,
+On Ethernets, the source and destination addresses, protocol,
and packet length are printed.
.LP
On FDDI networks, the '-e' option causes \fItcpdump\fP to print
the '-e' option is specified or not, the source routing information is
printed for source-routed packets.
.LP
+On 802.11 networks, the '-e' option causes \fItcpdump\fP to print
+the `frame control' fields, all of the addresses in the 802.11 header,
+and the packet length.
+As on FDDI networks,
+packets are assumed to contain an LLC packet.
+.LP
\fI(N.B.: The following description assumes familiarity with
the SLIP compression algorithm described in RFC-1144.)\fP
.LP
.fi
.RE
The first line says that rtsg sent an arp packet asking
-for the ethernet address of internet host csam.
+for the Ethernet address of internet host csam.
Csam
-replies with its ethernet address (in this example, ethernet addresses
+replies with its Ethernet address (in this example, Ethernet addresses
are in caps and internet addresses in lower case).
.LP
This would look less redundant if we had done \fItcpdump \-n\fP:
.sp .5
.fi
.RE
-For the first packet this says the ethernet source address is RTSG, the
-destination is the ethernet broadcast address, the type field
+For the first packet this says the Ethernet source address is RTSG, the
+destination is the Ethernet broadcast address, the type field
contained hex 0806 (type ETHER_ARP) and the total length was 64 bytes.
.HD
TCP Packets
\fISrc\fP and \fIdst\fP are the source and destination IP
addresses and ports.
\fIFlags\fP are some combination of S (SYN),
-F (FIN), P (PUSH) or R (RST) or a single `.' (no flags).
+F (FIN), P (PUSH), R (RST), W (ECN CWR) or E (ECN-Echo), or a single
+`.' (no flags).
\fIData-seqno\fP describes the portion of sequence space covered
by the data in this packet (see example below).
\fIAck\fP is sequence number of the next data expected the other
.HD
.B Capturing TCP packets with particular flag combinations (SYN-ACK, URG-ACK, etc.)
.PP
-There are 6 bits in the control bits section of the TCP header:
+There are 8 bits in the control bits section of the TCP header:
.IP
-.I URG | ACK | PSH | RST | SYN | FIN
+.I CWR | ECE | URG | ACK | PSH | RST | SYN | FIN
.PP
Let's assume that we want to watch packets used in establishing
a TCP connection.
-----------------------------------------------------------------
| acknowledgment number |
-----------------------------------------------------------------
-| HL | reserved |U|A|P|R|S|F| window size |
+| HL | rsvd |C|E|U|A|P|R|S|F| window size |
-----------------------------------------------------------------
| TCP checksum | urgent pointer |
-----------------------------------------------------------------
.PP
A TCP header usually holds 20 octets of data, unless options are
present.
-The fist line of the graph contains octets 0 - 3, the
+The first line of the graph contains octets 0 - 3, the
second line shows octets 4 - 7 etc.
.PP
Starting to count with 0, the relevant TCP control bits are contained
.nf
0 7| 15| 23| 31
----------------|---------------|---------------|----------------
-| HL | reserved |U|A|P|R|S|F| window size |
+| HL | rsvd |C|E|U|A|P|R|S|F| window size |
----------------|---------------|---------------|----------------
| | 13th octet | | |
.fi
.nf
| |
|---------------|
- | |U|A|P|R|S|F|
+ |C|E|U|A|P|R|S|F|
|---------------|
|7 5 3 0|
.fi
.PP
-We see that this octet contains 2 bits from the reserved field.
-According to RFC 793 this field is reserved for future use and must
-be 0.
-The remaining 6 bits are the TCP control bits we are interested
+These are the TCP control bits we are interested
in.
We have numbered the bits in this octet from 0 to 7, right to
left, so the PSH bit is bit number 3, while the URG bit is number 5.
with the SYN bit set in its header:
.PP
.nf
- | |U|A|P|R|S|F|
+ |C|E|U|A|P|R|S|F|
|---------------|
|0 0 0 0 0 0 1 0|
|---------------|
|7 6 5 4 3 2 1 0|
.fi
.PP
-We already mentioned that bits number 7 and 6 belong to the
-reserved field, so they must must be 0.
Looking at the
control bits section we see that only bit number 1 (SYN) is set.
.PP
with SYN-ACK set arrives:
.PP
.nf
- | |U|A|P|R|S|F|
+ |C|E|U|A|P|R|S|F|
|---------------|
|0 0 0 1 0 0 1 0|
|---------------|
immediately after the `A'.
.LP
A few anomalies are checked and may result in extra fields enclosed in
-square brackets: If a query contains an answer, name server or
-authority section,
+square brackets: If a query contains an answer, authority records or
+additional records section,
.IR ancount ,
.IR nscount ,
or
.fi
.RE
In the first example, \fIhelios\fP responds to query id 3 from \fIh2opolo\fP
-with 3 answer records, 3 name server records and 7 authority records.
+with 3 answer records, 3 name server records and 7 additional records.
The first answer record is type A (address) and its data is internet
address 128.32.137.3.
The total size of the response was 273 bytes,
may take up a page or more, so only use -v if you really want all the
gory details.
-If you are decoding SMB sessions containing unicode strings then you
-may wish to set the environment variable USE_UNICODE to 1.
-A patch to
-auto-detect unicode srings would be welcome.
-
For information on SMB packet formats and what all te fields mean see
-www.cifs.org or the pub/samba/specs/ directory on your favourite
+www.cifs.org or the pub/samba/specs/ directory on your favorite
samba.org mirror site.
The SMB patches were written by Andrew Tridgell
corresponding request, it might not be parsable.
.HD
-KIP Appletalk (DDP in UDP)
+KIP AppleTalk (DDP in UDP)
.LP
-Appletalk DDP packets encapsulated in UDP datagrams are de-encapsulated
+AppleTalk DDP packets encapsulated in UDP datagrams are de-encapsulated
and dumped as DDP packets (i.e., all the UDP header information is
discarded).
The file
.I /etc/atalk.names
-is used to translate appletalk net and node numbers to names.
+is used to translate AppleTalk net and node numbers to names.
Lines in this file have the form
.RS
.nf
.sp .5
.fi
.RE
-The first two lines give the names of appletalk networks.
+The first two lines give the names of AppleTalk networks.
The third
line gives the name of a particular host (a host is distinguished
from a net by the 3rd octet in the number \-
file may contain blank lines or comment lines (lines starting with
a `#').
.LP
-Appletalk addresses are printed in the form
+AppleTalk addresses are printed in the form
.RS
.nf
.sp .5
.RE
(If the
.I /etc/atalk.names
-doesn't exist or doesn't contain an entry for some appletalk
+doesn't exist or doesn't contain an entry for some AppleTalk
host/net number, addresses are printed in numeric form.)
In the first example, NBP (DDP port 2) on net 144.1 node 209
is sending to whatever is listening on port 220 of net icsd node 112.
number \- for this reason it's a good idea to keep node names and
net names distinct in /etc/atalk.names).
.LP
-NBP (name binding protocol) and ATP (Appletalk transaction protocol)
+NBP (name binding protocol) and ATP (AppleTalk transaction protocol)
packets have their contents interpreted.
Other protocols just dump
the protocol name (or number if no name is registered for the
The timestamp reflects the time the kernel first saw the packet.
No attempt
is made to account for the time lag between when the
-ethernet interface removed the packet from the wire and when the kernel
+Ethernet interface removed the packet from the wire and when the kernel
serviced the `new packet' interrupt.
.SH "SEE ALSO"
-traffic(1C), nit(4P), bpf(4), pcap(3)
+stty(1), pcap(3), bpf(4), nit(4P), pfconfig(8)
.SH AUTHORS
The original authors are:
.LP
asked to copy only part of a packet to userland, will not report the
true length of the packet; this would cause most IP packets to get an
error from
-.BR tcpdump ).
+.BR tcpdump );
+.IP
+capturing on some PPP devices won't work correctly.
.LP
We recommend that you upgrade to a 2.2 or later kernel.
.LP
A packet trace that crosses a daylight savings time change will give
skewed time stamps (the time change is ignored).
.LP
-Filter expressions that manipulate FDDI or Token Ring headers assume
-that all FDDI and Token Ring packets are SNAP-encapsulated Ethernet
-packets.
-This is true for IP, ARP, and DECNET Phase IV, but is not true
-for protocols such as ISO CLNS.
-Therefore, the filter may inadvertently
-accept certain packets that do not properly match the filter expression.
+Filter expressions on fields other than those in Token Ring headers will
+not correctly handle source-routed Token Ring packets.
.LP
-Filter expressions on fields other than those that manipulate Token Ring
-headers will not correctly handle source-routed Token Ring packets.
+Filter expressions on fields other than those in 802.11 headers will not
+correctly handle 802.11 data packets with both To DS and From DS set.
.LP
.BR "ip6 proto"
should chase header chain, but at this moment it does not.
projects / tcpdump / blobdiff