-.\" @(#) $Header: /tcpdump/master/tcpdump/Attic/tcpdump.1,v 1.104 2001-06-22 08:52:05 guy Exp $ (LBL)
+.\" @(#) $Header: /tcpdump/master/tcpdump/Attic/tcpdump.1,v 1.105 2001-06-25 03:18:27 itojun Exp $ (LBL)
.\"
.\" Copyright (c) 1987, 1988, 1989, 1990, 1991, 1992, 1994, 1995, 1996, 1997
.\" The Regents of the University of California. All rights reserved.
Print the link-level header on each dump line.
.TP
.B \-E
-Use \fIalgo:secret\fP for decrypting IPsec ESP packets. Algorithms may be
+Use \fIalgo:secret\fP for decrypting IPsec ESP packets.
+Algorithms may be
\fBdes-cbc\fP,
\fB3des-cbc\fP,
\fBblowfish-cbc\fP,
.IP
On Linux systems with 2.2 or later kernels, an
.I interface
-argument of ``any'' can be used to capture packets from all interfaces.
+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.
.TP
.B \-l
-Make stdout line buffered. Useful if you want to see the data
-while capturing it. E.g.,
+Make stdout line buffered.
+Useful if you want to see the data
+while capturing it.
+E.g.,
.br
``tcpdump\ \ \-l\ \ |\ \ tee dat'' or
``tcpdump\ \ \-l \ \ > dat\ \ &\ \ tail\ \ \-f\ \ dat''.
Don't convert addresses (i.e., host addresses, port numbers, etc.) to names.
.TP
.B \-N
-Don't print domain name qualification of host names. E.g.,
+Don't print domain name qualification of host names.
+E.g.,
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
+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
+Do not run the packet-matching code optimizer.
+This is useful only
if you suspect a bug in the optimizer.
.TP
.B \-p
\fIDon't\fP put the interface
-into promiscuous mode. Note that the interface might be in promiscuous
+into promiscuous mode.
+Note that the interface might be in promiscuous
mode for some other reason; hence, `-p' cannot be used as an abbreviation for
`ether host {local-hw-addr} or ether broadcast'.
.TP
.B \-q
-Quick (quiet?) output. Print less protocol information so output
+Quick (quiet?) output.
+Print less protocol information so output
lines are shorter.
.TP
.B \-r
default of 68 (with SunOS's NIT, the minimum is actually 96).
68 bytes is adequate for IP, ICMP, TCP
and UDP but may truncate protocol information from name server and NFS
-packets (see below). Packets truncated because of a limited snapshot
+packets (see below).
+Packets truncated because of a limited snapshot
are indicated in the output with ``[|\fIproto\fP]'', where \fIproto\fP
is the name of the protocol level at which the truncation has occurred.
Note that taking larger snapshots both increases
the amount of time it takes to process packets and, effectively,
-decreases the amount of packet buffering. This may cause packets to be
-lost. You should limit \fIsnaplen\fP to the smallest number that will
-capture the protocol information you're interested in. Setting
+decreases the amount of packet buffering.
+This may cause packets to be
+lost.
+You should limit \fIsnaplen\fP to the smallest number that will
+capture the protocol information you're interested in.
+Setting
\fIsnaplen\fP to 0 means use the required length to catch whole packets.
.TP
.B \-T
Force packets selected by "\fIexpression\fP" to be interpreted the
-specified \fItype\fR. Currently known types are
+specified \fItype\fR.
+Currently known types are
\fBcnfp\fR (Cisco NetFlow protocol),
\fBrpc\fR (Remote Procedure Call),
\fBrtp\fR (Real-Time Applications protocol),
Print a timestamp in default format proceeded by date on each dump line.
.TP
.B \-v
-(Slightly more) verbose output. For example, the time to live,
+(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.
.TP
.B \-vv
-Even more verbose output. For example, additional fields are
+Even more verbose output.
+For example, additional fields are
printed from NFS reply packets, and SMB packets are fully decoded.
.TP
.B \-vvv
-Even more verbose output. For example,
+Even more verbose output.
+For example,
telnet \fBSB\fP ... \fBSE\fP options
-are printed in full. With
+are printed in full.
+With
.B \-X
telnet options are printed in hex as well.
.TP
.B \-w
Write the raw packets to \fIfile\fR rather than parsing and printing
-them out. They can later be printed with the \-r option.
+them out.
+They can later be printed with the \-r option.
Standard output is used if \fIfile\fR is ``-''.
.TP
.B \-x
bytes will be printed.
.TP
.B \-X
-When printing hex, print ascii too. Thus if
+When printing hex, print ascii too.
+Thus if
.B \-x
is also set, the packet is printed in hex/ascii.
This is very handy for analysing new protocols.
in hex/ascii.
.IP "\fI expression\fP"
.RS
-selects which packets will be dumped. If no \fIexpression\fP
-is given, all packets on the net will be dumped. Otherwise,
+selects which packets will be dumped.
+If no \fIexpression\fP
+is given, all packets on the net will be dumped.
+Otherwise,
only packets for which \fIexpression\fP is `true' will be dumped.
.LP
The \fIexpression\fP consists of one or more
.I primitives.
Primitives usually consist of an
.I id
-(name or number) preceded by one or more qualifiers. There are three
+(name or number) preceded by one or more qualifiers.
+There are three
different kinds of qualifier:
.IP \fItype\fP
qualifiers say what kind of thing the id name or number refers to.
.B net
and
.BR port .
-E.g., `host foo', `net 128.3', `port 20'. If there is no type
+E.g., `host foo', `net 128.3', `port 20'.
+If there is no type
qualifier,
.B host
is assumed.
and
.B "src and"
.BR dst .
-E.g., `src foo', `dst net 128.3', `src or dst port ftp-data'. If
+E.g., `src foo', `dst net 128.3', `src or dst port ftp-data'.
+If
there is no dir qualifier,
.B "src or dst"
is assumed.
.B outbound
qualifiers can be used to specify a desired direction.
.IP \fIproto\fP
-qualifiers restrict the match to a particular protocol. Possible
+qualifiers restrict the match to a particular protocol.
+Possible
protos are:
.BR ether ,
.BR fddi ,
.B tcp
and
.BR udp .
-E.g., `ether src foo', `arp net 128.3', `tcp port 21'. If there is
+E.g., `ether src foo', `arp net 128.3', `tcp port 21'.
+If there is
no proto qualifier, all protocols consistent with the type are
-assumed. E.g., `src foo' means `(ip or arp or rarp) src foo'
+assumed.
+E.g., `src foo' means `(ip or arp or rarp) src foo'
(except the latter is not legal syntax), `net bar' means `(ip or
arp or rarp) net bar' and `port 53' means `(tcp or udp) port 53'.
.LP
network interface.'' FDDI headers contain Ethernet-like source
and destination addresses, and often contain Ethernet-like packet
types, so you can filter on these FDDI fields just as with the
-analogous Ethernet fields. FDDI headers also contain other fields,
+analogous Ethernet fields.
+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
.BR broadcast ,
.BR less ,
.B greater
-and arithmetic expressions. All of these are described below.
+and arithmetic expressions.
+All of these are described below.
.LP
More complex filter expressions are built up by using the words
.BR and ,
.B or
and
.B not
-to combine primitives. E.g., `host foo and not port ftp and not port ftp-data'.
-To save typing, identical qualifier lists can be omitted. E.g.,
+to combine primitives.
+E.g., `host foo and not port ftp and not port ftp-data'.
+To save typing, identical qualifier lists can be omitted.
+E.g.,
`tcp dst port ftp or ftp-data or domain' is exactly the same as
`tcp dst port ftp or tcp dst port ftp-data or tcp dst port domain'.
.LP
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. \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 host \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
+True if the packet used \fIhost\fP as a gateway.
+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
+nor the IP destination was \fIhost\fP.
+\fIHost\fP must be a name and
must be found both by the machine's host-name-to-IP-address resolution
mechanisms (host name file, DNS, NIS, etc.) and by the machine's
-host-name-to-Ethernet-address resolution mechanism (/etc/ethers, etc.).
+host-name-to-Ethernet-address resolution mechanism (/etc/ethers, etc.).
(An equivalent expression is
.in +.5i
.nf
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
+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
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,
+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 "\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
+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
+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
+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 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
+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
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
+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
intervening fragment.
Some offsets and field values may be expressed as names rather than
-as numeric values. The following protocol header field offsets are
+as numeric values.
+The following protocol header field offsets are
available: \fBicmptype\fP (ICMP type field), \fBicmpcode\fP (ICMP
code field), and \fBtcpflags\fP (TCP flags field).
.LP
Negation has highest precedence.
Alternation and concatenation have equal precedence and associate
-left to right. Note that explicit \fBand\fR tokens, not juxtaposition,
+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
.RE
.SH OUTPUT FORMAT
.LP
-The output of \fItcpdump\fP is protocol dependent. The following
+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
.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
+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
+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
+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
.HD
ARP/RARP Packets
.LP
-Arp/rarp output shows the type of request and its arguments. The
+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:
.fi
.RE
The first line says that rtsg sent an arp packet asking
-for the ethernet address of internet host csam. Csam
+for the ethernet address of internet host csam.
+Csam
replies with its ethernet address (in this example, ethernet addresses
are in caps and internet addresses in lower case).
.LP
TCP Packets
.LP
\fI(N.B.:The following description assumes familiarity with
-the TCP protocol described in RFC-793. If you are not familiar
+the TCP protocol described in RFC-793.
+If you are not familiar
with the protocol, neither this description nor \fItcpdump\fP will
be of much use to you.)\fP
.LP
.fi
.RE
\fISrc\fP and \fIdst\fP are the source and destination IP
-addresses and ports. \fIFlags\fP are some combination of S (SYN),
+addresses and ports.
+\fIFlags\fP are some combination of S (SYN),
F (FIN), P (PUSH) or R (RST) or a single `.' (no flags).
\fIData-seqno\fP describes the portion of sequence space covered
by the data in this packet (see example below).
\fIUrg\fP indicates there is `urgent' data in the packet.
\fIOptions\fP are tcp options enclosed in angle brackets (e.g., <mss 1024>).
.LP
-\fISrc, dst\fP and \fIflags\fP are always present. The other fields
+\fISrc, dst\fP and \fIflags\fP are always present.
+The other fields
depend on the contents of the packet's tcp protocol header and
are output only if appropriate.
.LP
.RE
The first line says that tcp port 1023 on rtsg sent a packet
to port \fIlogin\fP
-on csam. The \fBS\fP indicates that the \fISYN\fP flag was set.
+on csam.
+The \fBS\fP indicates that the \fISYN\fP flag was set.
The packet sequence number was 768512 and it contained no data.
(The notation is `first:last(nbytes)' which means `sequence
numbers \fIfirst\fP
1024 bytes.
.LP
Csam replies with a similar packet except it includes a piggy-backed
-ack for rtsg's SYN. Rtsg then acks csam's SYN. The `.' means no
+ack for rtsg's SYN.
+Rtsg then acks csam's SYN.
+The `.' means no
flags were set.
The packet contained no data so there is no data sequence number.
Note that the ack sequence
-number is a small integer (1). The first time \fItcpdump\fP sees a
+number is a small integer (1).
+The first time \fItcpdump\fP sees a
tcp `conversation', it prints the sequence number from the packet.
On subsequent packets of the conversation, the difference between
the current packet's sequence number and this initial sequence number
-is printed. This means that sequence numbers after the
+is printed.
+This means that sequence numbers after the
first can be interpreted
as relative byte positions in the conversation's data stream (with the
-first data byte each direction being `1'). `-S' will override this
+first data byte each direction being `1').
+`-S' will override this
feature, causing the original sequence numbers to be output.
.LP
On the 6th line, rtsg sends csam 19 bytes of data (bytes 2 through 20
in the rtsg \(-> csam side of the conversation).
The PUSH flag is set in the packet.
On the 7th line, csam says it's received data sent by rtsg up to
-but not including byte 21. Most of this data is apparently sitting in the
+but not including byte 21.
+Most of this data is apparently sitting in the
socket buffer since csam's receive window has gotten 19 bytes smaller.
Csam also sends one byte of data to rtsg in this packet.
On the 8th and 9th lines,
If the snapshot was small enough that \fItcpdump\fP didn't capture
the full TCP header, it interprets as much of the header as it can
and then reports ``[|\fItcp\fP]'' to indicate the remainder could not
-be interpreted. If the header contains a bogus option (one with a length
+be interpreted.
+If the header contains a bogus option (one with a length
that's either too small or beyond the end of the header), \fItcpdump\fP
reports it as ``[\fIbad opt\fP]'' and does not interpret any further
-options (since it's impossible to tell where they start). If the header
+options (since it's impossible to tell where they start).
+If the header
length indicates options are present but the IP datagram length is not
long enough for the options to actually be there, \fItcpdump\fP reports
it as ``[\fIbad hdr length\fP]''.
.I URG | ACK | PSH | RST | SYN | FIN
.PP
Let's assume that we want to watch packets used in establishing
-a TCP connection. Recall that TCP uses a 3-way handshake protocol
+a TCP connection.
+Recall that TCP uses a 3-way handshake protocol
when it initializes a new connection; the connection sequence with
regard to the TCP control bits is
.PP
.RE
.PP
Now we're interested in capturing packets that have only the
-SYN bit set (Step 1). Note that we don't want packets from step 2
-(SYN-ACK), just a plain initial SYN. What we need is a correct filter
+SYN bit set (Step 1).
+Note that we don't want packets from step 2
+(SYN-ACK), just a plain initial SYN.
+What we need is a correct filter
expression for \fItcpdump\fP.
.PP
Recall the structure of a TCP header without options:
.fi
.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
+present.
+The fist 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
.PP
We see that this octet contains 2 bytes 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
-in. We have numbered the bits in this octet from 0 to 7, right to
+be 0.
+The remaining 6 bits 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.
.PP
Recall that we want to capture packets with only SYN set.
.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
+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
Assuming that octet number 13 is an 8-bit unsigned integer in
.PP
Now, let's assume that we need to capture SYN packets, but we
don't care if ACK or any other TCP control bit is set at the
-same time. Let's see what happens to octet 13 when a TCP datagram
+same time.
+Let's see what happens to octet 13 when a TCP datagram
with SYN-ACK set arrives:
.PP
.nf
|7 6 5 4 3 2 1 0|
.fi
.PP
-Now bits 1 and 4 are set in the 13th octet. The binary value of
+Now bits 1 and 4 are set in the 13th octet.
+The binary value of
octet 13 is
.IP
00010010
.PP
Now we can't just use 'tcp[13] == 18' in the \fItcpdump\fP filter
expression, because that would select only those packets that have
-SYN-ACK set, but not those with only SYN set. Remember that we don't care
+SYN-ACK set, but not those with only SYN set.
+Remember that we don't care
if ACK or any other control bit is set as long as SYN is set.
.PP
In order to achieve our goal, we need to logically AND the
binary value of octet 13 with some other value to preserve
-the SYN bit. We know that we want SYN to be set in any case,
+the SYN bit.
+We know that we want SYN to be set in any case,
so we'll logically AND the value in the 13th octet with
the binary value of a SYN:
.PP
.RE
This says that port \fIwho\fP on host \fIactinide\fP sent a udp
datagram to port \fIwho\fP on host \fIbroadcast\fP, the Internet
-broadcast address. The packet contained 84 bytes of user data.
+broadcast address.
+The packet contained 84 bytes of user data.
.LP
Some UDP services are recognized (from the source or destination
port number) and the higher level protocol information printed.
UDP Name Server Requests
.LP
\fI(N.B.:The following description assumes familiarity with
-the Domain Service protocol described in RFC-1035. If you are not familiar
+the Domain Service protocol described in RFC-1035.
+If you are not familiar
with the protocol, the following description will appear to be written
in greek.)\fP
.LP
.RE
Host \fIh2opolo\fP asked the domain server on \fIhelios\fP for an
address record (qtype=A) associated with the name \fIucbvax.berkeley.edu.\fP
-The query id was `3'. The `+' indicates the \fIrecursion desired\fP flag
-was set. The query length was 37 bytes, not including the UDP and
-IP protocol headers. The query operation was the normal one, \fIQuery\fP,
-so the op field was omitted. If the op had been anything else, it would
+The query id was `3'.
+The `+' indicates the \fIrecursion desired\fP flag
+was set.
+The query length was 37 bytes, not including the UDP and
+IP protocol headers.
+The query operation was the normal one, \fIQuery\fP,
+so the op field was omitted.
+If the op had been anything else, it would
have been printed between the `3' and the `+'.
Similarly, the qclass was the normal one,
-\fIC_IN\fP, and omitted. Any other qclass would have been printed
+\fIC_IN\fP, and omitted.
+Any other qclass would have been printed
immediately after the `A'.
.LP
A few anomalies are checked and may result in extra fields enclosed in
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.
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,
-excluding UDP and IP headers. The op (Query) and response code
+address 128.32.137.3.
+The total size of the response was 273 bytes,
+excluding UDP and IP headers.
+The op (Query) and response code
(NoError) were omitted, as was the class (C_IN) of the A record.
.LP
In the second example, \fIhelios\fP responds to query 2 with a
response code of non-existent domain (NXDomain) with no answers,
-one name server and no authority records. The `*' indicates that
-the \fIauthoritative answer\fP bit was set. Since there were no
+one name server and no authority records.
+The `*' indicates that
+the \fIauthoritative answer\fP bit was set.
+Since there were no
answers, no type, class or data were printed.
.LP
Other flag characters that might appear are `\-' (recursion available,
-RA, \fInot\fP set) and `|' (truncated message, TC, set). If the
+RA, \fInot\fP set) and `|' (truncated message, TC, set).
+If the
`question' section doesn't contain exactly one entry, `[\fIn\fPq]'
is printed.
.LP
Note that name server requests and responses tend to be large and the
default \fIsnaplen\fP of 68 bytes may not capture enough of the packet
-to print. Use the \fB\-s\fP flag to increase the snaplen if you
-need to seriously investigate name server traffic. `\fB\-s 128\fP'
+to print.
+Use the \fB\-s\fP flag to increase the snaplen if you
+need to seriously investigate name server traffic.
+`\fB\-s 128\fP'
has worked well for me.
.HD
SMB/CIFS decoding
.LP
\fItcpdump\fP now includes fairly extensive SMB/CIFS/NBT decoding for data
-on UDP/137, UDP/138 and TCP/139. Some primitive decoding of IPX and
-NetBEUI SMB data is also done.
+on UDP/137, UDP/138 and TCP/139.
+Some primitive decoding of IPX and
+NetBEUI SMB data is also done.
By default a fairly minimal decode is done, with a much more detailed
-decode done if -v is used. Be warned that with -v a single SMB packet
+decode done if -v is used.
+Be warned that with -v a single SMB packet
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
+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
-samba.org mirror site. The SMB patches were written by Andrew Tridgell
+samba.org mirror site.
+The SMB patches were written by Andrew Tridgell
.HD
.RE
In the first line, host \fIsushi\fP sends a transaction with id \fI6709\fP
to \fIwrl\fP (note that the number following the src host is a
-transaction id, \fInot\fP the source port). The request was 112 bytes,
-excluding the UDP and IP headers. The operation was a \fIreadlink\fP
+transaction id, \fInot\fP the source port).
+The request was 112 bytes,
+excluding the UDP and IP headers.
+The operation was a \fIreadlink\fP
(read symbolic link) on file handle (\fIfh\fP) 21,24/10.731657119.
(If one is lucky, as in this case, the file handle can be interpreted
as a major,minor device number pair, followed by the inode number and
\fIWrl\fP replies `ok' with the contents of the link.
.LP
In the third line, \fIsushi\fP asks \fIwrl\fP to lookup the name
-`\fIxcolors\fP' in directory file 9,74/4096.6878. Note that the data printed
-depends on the operation type. The format is intended to be self
+`\fIxcolors\fP' in directory file 9,74/4096.6878.
+Note that the data printed
+depends on the operation type.
+The format is intended to be self
explanatory if read in conjunction with
an NFS protocol spec.
.LP
(\-v also prints the IP header TTL, ID, length, and fragmentation fields,
which have been omitted from this example.) In the first line,
\fIsushi\fP asks \fIwrl\fP to read 8192 bytes from file 21,11/12.195,
-at byte offset 24576. \fIWrl\fP replies `ok'; the packet shown on the
+at byte offset 24576.
+\fIWrl\fP replies `ok'; the packet shown on the
second line is the first fragment of the reply, and hence is only 1472
bytes long (the other bytes will follow in subsequent fragments, but
these fragments do not have NFS or even UDP headers and so might not be
-printed, depending on the filter expression used). Because the \-v flag
+printed, depending on the filter expression used).
+Because the \-v flag
is given, some of the file attributes (which are returned in addition
to the file data) are printed: the file type (``REG'', for regular file),
the file mode (in octal), the uid and gid, and the file size.
If the \-v flag is given more than once, even more details are printed.
.LP
Note that NFS requests are very large and much of the detail won't be printed
-unless \fIsnaplen\fP is increased. Try using `\fB\-s 192\fP' to watch
+unless \fIsnaplen\fP is increased.
+Try using `\fB\-s 192\fP' to watch
NFS traffic.
.LP
-NFS reply packets do not explicitly identify the RPC operation. Instead,
+NFS reply packets do not explicitly identify the RPC operation.
+Instead,
\fItcpdump\fP keeps track of ``recent'' requests, and matches them to the
-replies using the transaction ID. If a reply does not closely follow the
+replies using the transaction ID.
+If a reply does not closely follow the
corresponding request, it might not be parsable.
.HD
AFS Requests and Replies
.sp .5
.fi
.RE
-In the first line, host elvis sends a RX packet to pike. This was
+In the first line, host elvis sends a RX packet to pike.
+This was
a RX data packet to the fs (fileserver) service, and is the start of
-an RPC call. The RPC call was a rename, with the old directory file id
+an RPC call.
+The RPC call was a rename, with the old directory file id
of 536876964/1/1 and an old filename of `.newsrc.new', and a new directory
-file id of 536876964/1/1 and a new filename of `.newsrc'. The host pike
+file id of 536876964/1/1 and a new filename of `.newsrc'.
+The host pike
responds with a RPC reply to the rename call (which was successful, because
it was a data packet and not an abort packet).
.LP
-In general, all AFS RPCs are decoded at least by RPC call name. Most
+In general, all AFS RPCs are decoded at least by RPC call name.
+Most
AFS RPCs have at least some of the arguments decoded (generally only
the `interesting' arguments, for some definition of interesting).
.LP
for the Ubik protocol).
.LP
Note that AFS requests are very large and many of the arguments won't
-be printed unless \fIsnaplen\fP is increased. Try using `\fB-s 256\fP'
+be printed unless \fIsnaplen\fP is increased.
+Try using `\fB-s 256\fP'
to watch AFS traffic.
.LP
-AFS reply packets do not explicitly identify the RPC operation. Instead,
+AFS reply packets do not explicitly identify the RPC operation.
+Instead,
\fItcpdump\fP keeps track of ``recent'' requests, and matches them to the
-replies using the call number and service ID. If a reply does not closely
+replies using the call number and service ID.
+If a reply does not closely
follow the
corresponding request, it might not be parsable.
.LP
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
+discarded).
+The file
.I /etc/atalk.names
is used to translate appletalk net and node numbers to names.
Lines in this file have the form
.sp .5
.fi
.RE
-The first two lines give the names of appletalk networks. The third
+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 \-
a net number \fImust\fP have two octets and a host number \fImust\fP
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.
The second line is the same except the full name of the source node
-is known (`office'). The third line is a send from port 235 on
+is known (`office').
+The third line is a send from port 235 on
net jssmag node 149 to broadcast on the icsd-net NBP port (note that
the broadcast address (255) is indicated by a net name with no host
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)
-packets have their contents interpreted. Other protocols just dump
+packets have their contents interpreted.
+Other protocols just dump
the protocol name (or number if no name is registered for the
protocol) and packet size.
.fi
.RE
The first line is a name lookup request for laserwriters sent by net icsd host
-112 and broadcast on net jssmag. The nbp id for the lookup is 190.
+112 and broadcast on net jssmag.
+The nbp id for the lookup is 190.
The second line shows a reply for this request (note that it has the
same id) from host jssmag.209 saying that it has a laserwriter
-resource named "RM1140" registered on port 250. The third line is
+resource named "RM1140" registered on port 250.
+The third line is
another reply to the same request saying host techpit has laserwriter
"techpit" registered on port 186.
.fi
.RE
Jssmag.209 initiates transaction id 12266 with host helios by requesting
-up to 8 packets (the `<0-7>'). The hex number at the end of the line
+up to 8 packets (the `<0-7>').
+The hex number at the end of the line
is the value of the `userdata' field in the request.
.LP
-Helios responds with 8 512-byte packets. The `:digit' following the
+Helios responds with 8 512-byte packets.
+The `:digit' following the
transaction id gives the packet sequence number in the transaction
and the number in parens is the amount of data in the packet,
-excluding the atp header. The `*' on packet 7 indicates that the
+excluding the atp header.
+The `*' on packet 7 indicates that the
EOM bit was set.
.LP
-Jssmag.209 then requests that packets 3 & 5 be retransmitted. Helios
-resends them then jssmag.209 releases the transaction. Finally,
-jssmag.209 initiates the next request. The `*' on the request
+Jssmag.209 then requests that packets 3 & 5 be retransmitted.
+Helios
+resends them then jssmag.209 releases the transaction.
+Finally,
+jssmag.209 initiates the next request.
+The `*' on the request
indicates that XO (`exactly once') was \fInot\fP set.
.HD
.sp .5
.fi
.RE
-(The first form indicates there are more fragments. The second
+(The first form indicates there are more fragments.
+The second
indicates this is the last fragment.)
.LP
-\fIId\fP is the fragment id. \fISize\fP is the fragment
-size (in bytes) excluding the IP header. \fIOffset\fP is this
+\fIId\fP is the fragment id.
+\fISize\fP is the fragment
+size (in bytes) excluding the IP header.
+\fIOffset\fP is this
fragment's offset (in bytes) in the original datagram.
.LP
-The fragment information is output for each fragment. The first
+The fragment information is output for each fragment.
+The first
fragment contains the higher level protocol header and the frag
-info is printed after the protocol info. Fragments
+info is printed after the protocol info.
+Fragments
after the first contain no higher level protocol header and the
frag info is printed after the source and destination addresses.
For example, here is part of an ftp from arizona.edu to lbl-rtsg.arpa
.fi
.RE
There are a couple of things to note here: First, addresses in the
-2nd line don't include port numbers. This is because the TCP
+2nd line don't include port numbers.
+This is because the TCP
protocol information is all in the first fragment and we have no idea
what the port or sequence numbers are when we print the later fragments.
Second, the tcp sequence information in the first line is printed as if there
were 308 bytes of user data when, in fact, there are 512 bytes (308 in
-the first frag and 204 in the second). If you are looking for holes
+the first frag and 204 in the second).
+If you are looking for holes
in the sequence space or trying to match up acks
with packets, this can fool you.
.LP
.HD
Timestamps
.LP
-By default, all output lines are preceded by a timestamp. The timestamp
+By default, all output lines are preceded by a timestamp.
+The timestamp
is the current clock time in the form
.RS
.nf
.fi
.RE
and is as accurate as the kernel's clock.
-The timestamp reflects the time the kernel first saw the packet. No attempt
+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
serviced the `new packet' interrupt.
.LP
Name server inverse queries are not dumped correctly: the (empty)
question section is printed rather than real query in the answer
-section. Some believe that inverse queries are themselves a bug and
+section.
+Some believe that inverse queries are themselves a bug and
prefer to fix the program generating them rather than \fItcpdump\fP.
.LP
A packet trace that crosses a daylight savings time change will give
.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
+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.
.LP
Filter expressions on fields other than those that manipulate Token Ring
projects / tcpdump / commitdiff
