469 lines
13 KiB
Groff
469 lines
13 KiB
Groff
.\" Copyright (c) 1985, 1991, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" @(#)ping.8 8.2 (Berkeley) 12/11/93
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd March 1, 1997
|
|
.Dt PING 8
|
|
.Os BSD 4.3
|
|
.Sh NAME
|
|
.Nm ping
|
|
.Nd send
|
|
.Tn ICMP ECHO_REQUEST
|
|
packets to network hosts
|
|
.Sh SYNOPSIS
|
|
.Nm
|
|
.Op Fl AQRadfnqrv
|
|
.Op Fl c Ar count
|
|
.Op Fl i Ar wait
|
|
.Op Fl l Ar preload
|
|
.Op Fl m Ar ttl
|
|
.Op Fl p Ar pattern
|
|
.Op Fl P Ar policy
|
|
.Op Fl s Ar packetsize
|
|
.Op Fl S Ar src_addr
|
|
.Op Fl t Ar timeout
|
|
.Bo
|
|
.Ar host |
|
|
.Op Fl L
|
|
.Op Fl I Ar interface
|
|
.Op Fl T Ar ttl
|
|
.Ar mcast-group
|
|
.Bc
|
|
.Sh DESCRIPTION
|
|
.Nm Ping
|
|
uses the
|
|
.Tn ICMP
|
|
.No protocol Ap s mandatory
|
|
.Tn ECHO_REQUEST
|
|
datagram to elicit an
|
|
.Tn ICMP ECHO_RESPONSE
|
|
from a host or gateway.
|
|
.Tn ECHO_REQUEST
|
|
datagrams
|
|
.Pq Dq pings
|
|
have an IP and
|
|
.Tn ICMP
|
|
header, followed by a
|
|
.Dq struct timeval
|
|
and then an arbitrary number of
|
|
.Dq pad
|
|
bytes used to fill out the packet. The options are as follows:
|
|
.Bl -tag -width indent
|
|
.It Fl A
|
|
Audible.
|
|
Include a bell
|
|
.Pq ASCII 0x07
|
|
character in the output when no packet is received before the next packet
|
|
is transmitted.
|
|
.It Fl a
|
|
Audible.
|
|
Include a bell
|
|
.Pq ASCII 0x07
|
|
character in the output when any packet is received.
|
|
This option is ignored
|
|
if other format options are present.
|
|
.It Fl c Ar count
|
|
Stop after sending
|
|
.Pq and receiving
|
|
.Ar count
|
|
.Tn ECHO_RESPONSE
|
|
packets.
|
|
If this option is not specified,
|
|
.Nm
|
|
will operate until interrupted.
|
|
.It Fl d
|
|
Set the
|
|
.Dv SO_DEBUG
|
|
option on the socket being used.
|
|
.It Fl f
|
|
Flood ping.
|
|
Outputs packets as fast as they come back or one hundred times per second,
|
|
whichever is more.
|
|
For every
|
|
.Tn ECHO_REQUEST
|
|
sent a period
|
|
.Dq .\&
|
|
is printed, while for every
|
|
.Tn ECHO_REPLY
|
|
received a backspace is printed.
|
|
This provides a rapid display of how many packets are being dropped.
|
|
Only the super-user may use this option.
|
|
.Bf -emphasis
|
|
This can be very hard on a network and should be used with caution.
|
|
.Ef
|
|
.It Fl i Ar wait
|
|
Wait
|
|
.Ar wait
|
|
seconds
|
|
.Em between sending each packet .
|
|
The default is to wait for one second between each packet.
|
|
The wait time may be fractional, but only the super-user may specify
|
|
values less then 1 second.
|
|
This option is incompatible with the
|
|
.Fl f
|
|
option.
|
|
.It Fl I Ar interface
|
|
Source multicast packets with the given interface address.
|
|
This flag only applies if the ping destination is a multicast address.
|
|
.It Fl l Ar preload
|
|
If
|
|
.Ar preload
|
|
is specified,
|
|
.Nm
|
|
sends that many packets as fast as possible before falling into its normal
|
|
mode of behavior.
|
|
Only the super-user may use this option.
|
|
.It Fl m Ar ttl
|
|
Set the IP Time To Live for outgoing packets.
|
|
If not specified, the kernel uses the value of the
|
|
.Va net.inet.ip.ttl
|
|
MIB variable.
|
|
.It Fl L
|
|
Suppress loopback of multicast packets.
|
|
This flag only applies if the ping destination is a multicast address.
|
|
.It Fl n
|
|
Numeric output only.
|
|
No attempt will be made to lookup symbolic names for host addresses.
|
|
.It Fl p Ar pattern
|
|
You may specify up to 16
|
|
.Dq pad
|
|
bytes to fill out the packet you send.
|
|
This is useful for diagnosing data-dependent problems in a network.
|
|
For example,
|
|
.Dq Li \-p ff
|
|
will cause the sent packet to be filled with all
|
|
ones.
|
|
.It Fl P Ar policy
|
|
.Ar policy
|
|
specifies IPsec policy for the ping session.
|
|
For details please refer to
|
|
.Xr ipsec 4
|
|
and
|
|
.Xr ipsec_set_policy 3 .
|
|
.It Fl Q
|
|
Somewhat quiet output.
|
|
.No Don Ap t
|
|
display ICMP error messages that are in response to our query messages.
|
|
Originally, the
|
|
.Fl v
|
|
flag was required to display such errors, but
|
|
.Fl v
|
|
displays all ICMP error messages. On a busy machine, this output can
|
|
be overbearing. Without the
|
|
.Fl Q
|
|
flag,
|
|
.Nm
|
|
prints out any ICMP error messages caused by its own ECHO_REQUEST
|
|
messages.
|
|
.It Fl q
|
|
Quiet output.
|
|
Nothing is displayed except the summary lines at startup time and
|
|
when finished.
|
|
.It Fl R
|
|
Record route.
|
|
Includes the
|
|
.Tn RECORD_ROUTE
|
|
option in the
|
|
.Tn ECHO_REQUEST
|
|
packet and displays
|
|
the route buffer on returned packets.
|
|
Note that the IP header is only large enough for nine such routes;
|
|
the
|
|
.Xr traceroute 8
|
|
command is usually better at determining the route packets take to a
|
|
particular destination.
|
|
If more routes come back than should, such as due to an illegal spoofed
|
|
packet, ping will print the route list and then truncate it at the correct
|
|
spot.
|
|
Many hosts ignore or discard the
|
|
.Tn RECORD_ROUTE
|
|
option.
|
|
.It Fl r
|
|
Bypass the normal routing tables and send directly to a host on an attached
|
|
network.
|
|
If the host is not on a directly-attached network, an error is returned.
|
|
This option can be used to ping a local host through an interface
|
|
that has no route through it
|
|
.Po
|
|
e.g., after the interface was dropped by
|
|
.Xr routed 8
|
|
.Pc .
|
|
.It Fl s Ar packetsize
|
|
Specify the number of data bytes to be sent.
|
|
The default is 56, which translates into 64
|
|
.Tn ICMP
|
|
data bytes when combined
|
|
with the 8 bytes of
|
|
.Tn ICMP
|
|
header data.
|
|
Only the super-user may use this option.
|
|
.It Fl S Ar src_addr
|
|
Use the following IP address as the source address in outgoing packets.
|
|
On hosts with more than one IP address, this option can be used to
|
|
force the source address to be something other than the IP address
|
|
of the interface the probe packet is sent on. If the IP address
|
|
is not one of this machine's interface addresses, an error is
|
|
returned and nothing is sent.
|
|
.It Fl t Ar timeout
|
|
Specify a timeout, in seconds, before ping exits regardless of how
|
|
many packets have been recieved.
|
|
.It Fl T Ar ttl
|
|
Set the IP Time To Live for multicasted packets.
|
|
This flag only applies if the ping destination is a multicast address.
|
|
.It Fl v
|
|
Verbose output.
|
|
.Tn ICMP
|
|
packets other than
|
|
.Tn ECHO_RESPONSE
|
|
that are received are listed.
|
|
.El
|
|
.Pp
|
|
When using
|
|
.Nm
|
|
for fault isolation, it should first be run on the local host, to verify
|
|
that the local network interface is up and running.
|
|
Then, hosts and gateways further and further away should be
|
|
.Dq pinged .
|
|
Round-trip times and packet loss statistics are computed.
|
|
If duplicate packets are received, they are not included in the packet
|
|
loss calculation, although the round trip time of these packets is used
|
|
in calculating the round-trip time statistics.
|
|
When the specified number of packets have been sent
|
|
.Pq and received
|
|
or if the program is terminated with a
|
|
.Dv SIGINT ,
|
|
a brief summary is displayed, showing the number of packets sent and
|
|
received, and the minimum, maximum, mean, and standard deviation of
|
|
the round-trip times.
|
|
.Pp
|
|
This program is intended for use in network testing, measurement and
|
|
management.
|
|
Because of the load it can impose on the network, it is unwise to use
|
|
.Nm
|
|
during normal operations or from automated scripts.
|
|
.Sh ICMP PACKET DETAILS
|
|
An IP header without options is 20 bytes.
|
|
An
|
|
.Tn ICMP
|
|
.Tn ECHO_REQUEST
|
|
packet contains an additional 8 bytes worth of
|
|
.Tn ICMP
|
|
header followed by an arbitrary amount of data.
|
|
When a
|
|
.Ar packetsize
|
|
is given, this indicated the size of this extra piece of data
|
|
.Pq the default is 56 .
|
|
Thus the amount of data received inside of an IP packet of type
|
|
.Tn ICMP
|
|
.Tn ECHO_REPLY
|
|
will always be 8 bytes more than the requested data space
|
|
.Pq the Tn ICMP header .
|
|
.Pp
|
|
If the data space is at least eight bytes large,
|
|
.Nm
|
|
uses the first eight bytes of this space to include a timestamp which
|
|
it uses in the computation of round trip times.
|
|
If less than eight bytes of pad are specified, no round trip times are
|
|
given.
|
|
.Sh DUPLICATE AND DAMAGED PACKETS
|
|
.Nm Ping
|
|
will report duplicate and damaged packets.
|
|
Duplicate packets should never occur when pinging a unicast address,
|
|
and seem to be caused by
|
|
inappropriate link-level retransmissions.
|
|
Duplicates may occur in many situations and are rarely
|
|
.Pq if ever
|
|
a good sign, although the presence of low levels of duplicates may not
|
|
always be cause for alarm.
|
|
Duplicates are expected when pinging a broadcast or multicast address,
|
|
since they are not really duplicates but replies from different hosts
|
|
to the same request.
|
|
.Pp
|
|
Damaged packets are obviously serious cause for alarm and often
|
|
indicate broken hardware somewhere in the
|
|
.Nm
|
|
packet's path (in the network or in the hosts).
|
|
.Sh TRYING DIFFERENT DATA PATTERNS
|
|
The
|
|
(inter)network
|
|
layer should never treat packets differently depending on the data
|
|
contained in the data portion.
|
|
Unfortunately, data-dependent problems have been known to sneak into
|
|
networks and remain undetected for long periods of time.
|
|
In many cases the particular pattern that will have problems is something
|
|
that does not have sufficient
|
|
.Dq transitions ,
|
|
such as all ones or all zeros, or a pattern right at the edge, such as
|
|
almost all zeros.
|
|
It is not
|
|
necessarily enough to specify a data pattern of all zeros (for example)
|
|
on the command line because the pattern that is of interest is
|
|
at the data link level, and the relationship between what you type and
|
|
what the controllers transmit can be complicated.
|
|
.Pp
|
|
This means that if you have a data-dependent problem you will probably
|
|
have to do a lot of testing to find it.
|
|
If you are lucky, you may manage to find a file that either
|
|
cannot
|
|
be sent across your network or that takes much longer to transfer than
|
|
other similar length files.
|
|
You can then examine this file for repeated patterns that you can test
|
|
using the
|
|
.Fl p
|
|
option of
|
|
.Nm .
|
|
.Sh TTL DETAILS
|
|
The
|
|
.Tn TTL
|
|
value of an IP packet represents the maximum number of IP routers
|
|
that the packet can go through before being thrown away.
|
|
In current practice you can expect each router in the Internet to decrement
|
|
the
|
|
.Tn TTL
|
|
field by exactly one.
|
|
.Pp
|
|
The
|
|
.Tn TCP/IP
|
|
specification states that the
|
|
.Tn TTL
|
|
field for
|
|
.Tn TCP
|
|
packets should be set to 60, but many systems use smaller values
|
|
.Po
|
|
.Bx 4.3
|
|
uses 30,
|
|
.Bx 4.2
|
|
used 15
|
|
.Pc .
|
|
.Pp
|
|
The maximum possible value of this field is 255, and most
|
|
.Ux
|
|
systems set
|
|
the
|
|
.Tn TTL
|
|
field of
|
|
.Tn ICMP ECHO_REQUEST
|
|
packets to 255.
|
|
This is why you will find you can
|
|
.Dq ping
|
|
some hosts, but not reach them with
|
|
.Xr telnet 1
|
|
or
|
|
.Xr ftp 1 .
|
|
.Pp
|
|
In normal operation
|
|
.Nm
|
|
prints the ttl value from the packet it receives.
|
|
When a remote system receives a ping packet, it can do one of three things
|
|
with the
|
|
.Tn TTL
|
|
field in its response:
|
|
.Bl -bullet
|
|
.It
|
|
Not change it; this is what
|
|
.Bx
|
|
systems did before the
|
|
.Bx 4.3 tahoe
|
|
release.
|
|
In this case the
|
|
.Tn TTL
|
|
value in the received packet will be 255 minus the
|
|
number of routers in the round-trip path.
|
|
.It
|
|
Set it to 255; this is what current
|
|
.Bx
|
|
systems do.
|
|
In this case the
|
|
.Tn TTL
|
|
value in the received packet will be 255 minus the
|
|
number of routers in the path
|
|
.Em from
|
|
the remote system
|
|
.Em to
|
|
the
|
|
.Nm Ns Em ing
|
|
host.
|
|
.It
|
|
Set it to some other value.
|
|
Some machines use the same value for
|
|
.Tn ICMP
|
|
packets that they use for
|
|
.Tn TCP
|
|
packets, for example either 30 or 60.
|
|
Others may use completely wild values.
|
|
.El
|
|
.Sh RETURN VALUES
|
|
The
|
|
.Nm
|
|
command returns an exit status of zero if at least one response was
|
|
heard from the specified
|
|
.Ar host ;
|
|
a status of two if the transmission was successful but no responses
|
|
were received; or another value
|
|
.Pq from Aq Pa sysexits.h
|
|
if an error occurred.
|
|
.Sh SEE ALSO
|
|
.Xr netstat 1 ,
|
|
.Xr ifconfig 8 ,
|
|
.Xr routed 8 ,
|
|
.Xr traceroute 8
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
command appeared in
|
|
.Bx 4.3 .
|
|
.Sh AUTHORS
|
|
The original
|
|
.Nm
|
|
command was written by
|
|
.An Mike Muuss
|
|
while at the US Army Ballistics
|
|
Research Laboratory.
|
|
.Sh BUGS
|
|
Many Hosts and Gateways ignore the
|
|
.Tn RECORD_ROUTE
|
|
option.
|
|
.Pp
|
|
The maximum IP header length is too small for options like
|
|
.Tn RECORD_ROUTE
|
|
to be completely useful.
|
|
.No There Ap s
|
|
not much that can be done about this, however.
|
|
.Pp
|
|
Flood pinging is not recommended in general, and flood pinging the
|
|
broadcast address should only be done under very controlled conditions.
|
|
.Pp
|
|
The
|
|
.Fl v
|
|
option is not worth much on busy hosts.
|