tcpdump.1

Windump3.6.2源代码

.nf
\fBether host \fIehost \fBand not host \fIhost\fR
.fi
.in -.5i
which can be used with either names or numbers for \fIhost / ehost\fP.)
This syntax does not work in IPv6-enabled configuration at this moment.
.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).
.IP "\fBsrc net \fInet\fR"
True if the IPv4/v6 source address of the packet has a network
number of \fInet\fP.
.IP "\fBnet \fInet\fR"
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 \fImask\fR"
True if the IP address matches \fInet\fR with the specific netmask.
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 IPv4/v6 address matches \fInet\fR a netmask \fIlen\fR bits wide.
May be qualified with \fBsrc\fR or \fBdst\fR.
.IP "\fBdst port \fIport\fR"
True if the packet is ip/tcp, ip/udp, ip6/tcp or ip6/udp and has a
destination port value of \fIport\fP.
The \fIport\fP can be a number or a name used in /etc/services (see
.IR tcp (4P)
and
.IR udp (4P)).
If a name is used, both the port
number and protocol are checked.  If a number or ambiguous name is used,
only the port number is checked (e.g., \fBdst port 513\fR will print both
tcp/login traffic and udp/who traffic, and \fBport domain\fR will print
both tcp/domain and udp/domain traffic).
.IP "\fBsrc port \fIport\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:
.in +.5i
.nf
\fBtcp src port \fIport\fR
.fi
.in -.5i
which matches only tcp packets whose source port is \fIport\fP.
.IP "\fBless \fIlength\fR"
True if the packet has a length less than or equal to \fIlength\fP.
This is equivalent to:
.in +.5i
.nf
\fBlen <= \fIlength\fP.
.fi
.in -.5i
.IP "\fBgreater \fIlength\fR"
True if the packet has a length greater than or equal to \fIlength\fP.
This is equivalent to:
.in +.5i
.nf
\fBlen >= \fIlength\fP.
.fi
.in -.5i
.IP "\fBip proto \fIprotocol\fR"
True if the packet is an IP 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, \fIudp\fP, or \fItcp\fP.
Note that the identifiers \fItcp\fP, \fIudp\fP, and \fIicmp\fP are also
keywords and must be escaped via backslash (\\), which is \\\\ in the C-shell.
Note that this primitive does not chase protocol header chain.
.IP "\fBip6 proto \fIprotocol\fR"
True if the packet is an IPv6 packet of protocol type \fIprotocol\fP.
Note that this primitive does not chase protocol header chain.
.IP "\fBip6 protochain \fIprotocol\fR"
True if the packet is IPv6 packet,
and contains protocol header with type \fIprotocol\fR
in its protocol header chain.
For example,
.in +.5i
.nf
\fBip6 protochain 6\fR
.fi
.in -.5i
matches any IPv6 packet with TCP protocol header in the protocol header chain.
The packet may contain, for example,
authentication header, routing header, or hop-by-hop option header,
between IPv6 header and TCP header.
The BPF code emitted by this primitive is complex and
cannot be optimized by BPF optimizer code in \fItcpdump\fP,
so this can be somewhat slow.
.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.  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.
.IP "\fBether multicast\fR"
True if the packet is an ethernet multicast packet.  The \fIether\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.
.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, or
\fIiso\fP.
Note these identifiers are also keywords
and must be escaped via backslash (\\).
[In the case of FDDI (e.g., `\fBfddi protocol arp\fR'), the
protocol identification comes from the 802.2 Logical Link Control
(LLC) header, which is usually layered on top of the FDDI header.
\fITcpdump\fP assumes, when filtering on the protocol identifier,
that all FDDI packets include an LLC header, and that the LLC header
is in so-called SNAP format.  The same applies to Token Ring.]
.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
that are configured to run DECNET.]
.IP "\fBdecnet dst \fIhost\fR"
True if the DECNET destination address is
.IR host .
.IP "\fBdecnet host \fIhost\fR"
True if either the DECNET source or destination address is
.IR host .
.IP "\fBip\fR, \fBip6\fR, \fBarp\fR, \fBrarp\fR, \fBatalk\fR, \fBaarp\fR, \fBdecnet\fR, \fBiso\fR"
Abbreviations for:
.in +.5i
.nf
\fBether proto \fIp\fR
.fi
.in -.5i
where \fIp\fR is one of the above protocols.
.IP "\fBlat\fR, \fBmoprc\fR, \fBmopdl\fR"
Abbreviations for:
.in +.5i
.nf
\fBether proto \fIp\fR
.fi
.in -.5i
where \fIp\fR is one of the above protocols.
Note that
\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
\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.
.IP  "\fBtcp\fR, \fBudp\fR, \fBicmp\fR"
Abbreviations for:
.in +.5i
.nf
\fBip proto \fIp\fR\fB or ip6 proto \fIp\fR
.fi
.in -.5i
where \fIp\fR is one of the above protocols.
.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.
.IP "\fBclnp\fR, \fBesis\fR, \fBisis\fR"
Abbreviations for:
.in +.5i
.nf
\fBiso proto \fIp\fR
.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  "\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.
To access
data inside the packet, use the following syntax:
.in +.5i
.nf
\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
indicates the protocol layer for the index operation.
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
given by \fIexpr\fR.
\fISize\fR is optional and indicates the number of bytes in the
field of interest; it can be either one, two, or four, and defaults to one.
The length operator, indicated by the keyword \fBlen\fP, gives the
length of the packet.

For example, `\fBether[0] & 1 != 0\fP' catches all multicast traffic.
The expression `\fBip[0] & 0xf != 5\fP'
catches all IP packets with options. The expression
`\fBip[6:2] & 0x1fff = 0\fP'
catches only unfragmented datagrams and frag zero of fragmented datagrams.
This check is implicitly applied to the \fBtcp\fP and \fBudp\fP
index operations.
For instance, \fBtcp[0]\fP always means the first
byte of the TCP \fIheader\fP, and never means the first byte of an
intervening fragment.
.LP
Primitives may be combined using:
.IP
A parenthesized group of primitives and operators
(parentheses are special to the Shell and must be escaped).
.IP
Negation (`\fB!\fP' or `\fBnot\fP').
.IP
Concatenation (`\fB&&\fP' or `\fBand\fP').
.IP
Alternation (`\fB||\fP' or `\fBor\fP').
.LP
Negation has highest precedence.
Alternation and concatenation have equal precedence and associate
left to right.  Note that explicit \fBand\fR tokens, not juxtaposition,
are now required for concatenation.
.LP
If an identifier is given without a keyword, the most recent keyword
is assumed.
For example,
.in +.5i
.nf
\fBnot host vs and ace\fR
.fi
.in -.5i
is short for
.in +.5i
.nf
\fBnot host vs and host ace\fR
.fi
.in -.5i
which should not be confused with
.in +.5i
.nf
\fBnot ( host vs or ace )\fR
.fi
.in -.5i
.LP
Expression arguments can be passed to \fItcpdump\fP as either a single
argument or as multiple arguments, whichever is more convenient.
Generally, if the expression contains Shell metacharacters, it is
easier to pass it as a single, quoted argument.
Multiple arguments are concatenated with spaces before being parsed.
.SH EXAMPLES
.LP
To print all packets arriving at or departing from \fIsundown\fP:
.RS
.nf
\fBtcpdump host sundown\fP
.fi
.RE
.LP
To print traffic between \fIhelios\fR and either \fIhot\fR or \fIace\fR:
.RS
.nf
\fBtcpdump host helios and \\( hot or ace \\)\fP
.fi
.RE
.LP
To print all IP packets between \fIace\fR and any host except \fIhelios\fR:
.RS
.nf
\fBtcpdump ip host ace and not helios\fP
.fi
.RE
.LP
To print all traffic between local hosts and hosts at Berkeley:
.RS
.nf
.B
tcpdump net ucb-ether
.fi
.RE
.LP
To print all ftp traffic through internet gateway \fIsnup\fP:
(note that the expression is quoted to prevent the shell from
(mis-)interpreting the parentheses):
.RS
.nf
.B
tcpdump 'gateway snup and (port ftp or ftp-data)'
.fi
.RE
.LP
To print traffic neither sourced from nor destined for local hosts
(if you gateway to one other net, this stuff should never make it
onto your local net).
.RS
.nf
.B
tcpdump ip and not net \fIlocalnet\fP
.fi
.RE
.LP
To print the start and end packets (the SYN and FIN packets) of each
TCP conversation that involves a non-local host.
.RS
.nf
.B
tcpdump 'tcp[13] & 3 != 0 and not src and dst net \fIlocalnet\fP'
.fi
.RE
.LP
To print IP packets longer than 576 bytes sent through gateway \fIsnup\fP:
.RS
.nf
.B
tcpdump 'gateway snup and ip[2:2] > 576'
.fi
.RE
.LP
To print IP broadcast or multicast packets that were
.I not
sent via ethernet broadcast or multicast:
.RS
.nf
.B
tcpdump 'ether[0] & 1 = 0 and ip[16] >= 224'
.fi
.RE
.LP
To print all ICMP packets that are not echo requests/replies (i.e., not
ping packets):
.RS
.nf
.B
tcpdump 'icmp[0] != 8 and icmp[0] != 0'
.fi
.RE
.SH OUTPUT FORMAT
.LP
The output of \fItcpdump\fP is protocol dependent.  The following
gives a brief description and examples of most of the formats.
.de HD
.sp 1.5
.B
..
.HD
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,
and packet length are printed.
.LP
On FDDI networks, the  '-e' option causes \fItcpdump\fP to print
the `frame control' field,  the source and destination addresses,
and the packet length.  (The `frame control' field governs the
interpretation of the rest of the packet.  Normal packets (such
as those containing IP datagrams) are `async' packets, with a priority
value between 0 and 7; for example, `\fBasync4\fR'.  Such packets
are assumed to contain an 802.2 Logical Link Control (LLC) packet;
the LLC header is printed if it is \fInot\fR an ISO datagram or a
so-called SNAP packet.
.LP
On Token Ring networks, the '-e' option causes \fItcpdump\fP to print
the `access control' and `frame control' fields, the source and
destination addresses, and the packet length.  As on FDDI networks,
packets are assumed to contain an LLC packet.  Regardless of whether
the '-e' option is specified or not, the source routing information is
printed for source-routed packets.
.LP
\fI(N.B.: The following description assumes familiarity with
the SLIP compression algorithm described in RFC-1144.)\fP
.LP
On SLIP links, a direction indicator (``I'' for inbound, ``O'' for outbound),
packet type, and compression information are printed out.
The packet type is printed first.
The three types are \fIip\fP, \fIutcp\fP, and \fIctcp\fP.
No further link information is printed for \fIip\fR packets.
For TCP packets, the connection identifier is printed following the type.
If the packet is compressed, its encoded header is printed out.
The special cases are printed out as
\fB*S+\fIn\fR and \fB*SA+\fIn\fR, where \fIn\fR is the amount by which
the sequence number (or sequence number and ack) has changed.
If it is not a special case,
zero or more changes are printed.
A change is indicated by U (urgent pointer), W (window), A (ack),
S (sequence number), and I (packet ID), followed by a delta (+n or -n),
or a new value (=n).
Finally, the amount of data in the packet and compressed header length
are printed.
.LP
For example, the following line shows an outbound compressed TCP packet,
with an implicit connection identifier; the ack has changed by 6,
the sequence number by 49, and the packet ID by 6; there are 3 bytes of
data and 6 bytes of compressed header:
.RS
.nf
\fBO ctcp * A+6 S+49 I+6 3 (6)\fP
.fi
.RE
.HD
ARP/RARP Packets
.LP
Arp/rarp output shows the type of request and its arguments.  The
format is intended to be self explanatory.
Here is a short sample taken from the start of an `rlogin' from
host \fIrtsg\fP to host \fIcsam\fP:
.RS
.nf
.sp .5