-.\" @(#) $Header: /tcpdump/master/tcpdump/Attic/tcpdump.1,v 1.134 2002-12-19 05:44:47 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 "8 August 2002"
+.TH TCPDUMP 1 "18 April 2005"
.SH NAME
tcpdump \- dump traffic on a network
.SH SYNOPSIS
.na
.B tcpdump
[
-.B \-aAdDeflnNOpqRStuvxX
+.B \-AdDeflLnNOpqRStuUvxX
] [
.B \-c
.I count
.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
.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:
.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/Tru64 UNIX:
+.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
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
Print each packet (minus its link level header) in ASCII. Handy for
capturing web pages.
.TP
-.B \-a
-Attempt to convert network and broadcast addresses to names.
-.TP
.B \-c
Exit after receiving \fIcount\fP packets.
.TP
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 2 and continuing upward.
+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
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' IPv4 addresses numerically rather than symbolically
``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
\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
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).
.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.
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. Note that this is the entire link-layer
required padding.
.TP
.B \-xx
-Print each packet,
+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
-Print each packet (minus its link level header) in hex and 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.
.TP
.B \-XX
-Print each packet,
+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
.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.
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"
"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
\fItcpdump\fR checks the DSAP (Destination Service Access Point) and
SSAP (Source Service Access Point) fields of the LLC header;
.TP
-\fBstp\fP and \fInetbeui\fP
+\fBstp\fP and \fBnetbeui\fP
\fItcpdump\fR checks the DSAP of the LLC header;
.TP
-\fIatalk\fP
+\fBatalk\fP
\fItcpdump\fR checks for a SNAP-format packet with an OUI of 0x080007
-and the Appletalk etype.
+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:
.RS
.TP
-\fBiso\fP, \fBsap\fP, and \fBnetbeui\fP
+\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
+\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
+\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
.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
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
.fi
.in -.5i
\fIProto\fR is one of \fBether, fddi, tr, wlan, ppp, slip, link,
-ip, arp, rarp, tcp, udp, icmp\fR or \fBip6\fR, and
+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.)
+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
.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
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
projects / tcpdump / blobdiff