usr.bin/netstat/netstat.1

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.\"	@(#)netstat.1	8.8 (Berkeley) 4/18/94
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.Dd December 21, 2022
.Dt NETSTAT 1
.Os
.Sh NAME
.Nm netstat
.Nd show network status
.Sh SYNOPSIS
.ds address_family Fl f Ar address_family Ns Op , Ns Ar family ...
.Nm
.Op Fl Aan
.Op \*[address_family]
.Op Fl M Ar core
.Op Fl N Ar system
.Nm
.Op Fl bdghiLlmnqrSsTtv
.Op \*[address_family]
.Op Fl M Ar core
.Op Fl N Ar system
.Nm
.Op Fl dn
.Op Fl I Ar interface
.Op Fl M Ar core
.Op Fl N Ar system
.Op Fl w Ar wait
.Nm
.Op Fl M Ar core
.Op Fl N Ar system
.Op Fl p Ar protocol
.Nm
.Op Fl M Ar core
.Op Fl N Ar system
.Op Fl p Ar protocol
.Fl P Ar pcbaddr
.Nm
.Op Fl i
.Op Fl I Ar Interface
.Op Fl p Ar protocol
.Nm
.Op Fl is
.Op \*[address_family]
.Op Fl I Ar Interface
.Nm
.Op Fl s
.Op Fl I Ar Interface
.Fl B
.Sh DESCRIPTION
The
.Nm
command symbolically displays the contents of various network-related
data structures.
There are a number of output formats,
depending on the options for the information presented.
The first form of the command displays a list of active sockets for
each protocol.
The second form presents the contents of one of the other network
data structures according to the option selected.
Using the third form, with a
.Ar wait
interval specified,
.Nm
will continuously display the information regarding packet
traffic on the configured network interfaces.
The fourth form displays statistics about the named protocol.
The fifth and sixth forms display per interface statistics for
the specified protocol or address family.
.Pp
The options have the following meaning:
.Bl -tag -width flag
.It Fl A
With the default display,
show the address of any protocol control blocks associated with sockets; used
for debugging.
.It Fl a
With the default display,
show the state of all sockets; normally sockets used by
server processes are not shown.
.It Fl B
With the default display,
show the current
.Xr bpf 4
peers.
To show only the peers listening to a specific interface,
use the
.Fl I
option.
If the
.Fl s
option is present, show the current
.Xr bpf 4
statistics.
.It Fl b
With the interface display (option
.Fl i ) ,
show bytes in and out, instead of packets in and out.
.It Fl d
With either interface display (option
.Fl i
or an interval, as described below),
show the number of dropped packets.
.It \*[address_family]
Limit statistics or address control block reports to those
of the specified
.Ar address_families  .
The following address families
are recognized:
.Ar inet ,
for
.Dv AF_INET ;
.Ar inet6 ,
for
.Dv AF_INET6 ;
.Ar arp ,
for
.Dv AF_ARP ;
.Ar ns ,
for
.Dv AF_NS ;
.Ar atalk ,
for
.Dv AF_APPLETALK ;
.Ar mpls ,
for
.Dv AF_MPLS ;
and
.Ar local
or
.Ar unix ,
for
.Dv AF_LOCAL .
.It Fl g
Show information related to multicast (group address) routing.
By default, show the IP Multicast virtual-interface and routing tables.
If the
.Fl s
option is also present, show multicast routing statistics.
.It Fl h
When used with
.Fl b
in combination with either
.Fl i
or
.Fl I ,
output "human-readable" byte counts.
.It Fl I Ar interface
Show information about the specified interface;
used with a
.Ar wait
interval as described below.
If the
.Fl f Ar address_family
option (with the
.Fl s
option) or the
.Fl p Ar protocol
option is present, show per-interface statistics on the
.Ar interface
for the specified
.Ar address_family
or
.Ar protocol ,
respectively.
.It Fl i
Show the state of interfaces which have been auto-configured
(interfaces statically configured into a system, but not
located at boot time are not shown).
If the
.Fl a
options is also present, multicast addresses currently in use are shown
for each Ethernet interface and for each IP interface address.
Multicast addresses are shown on separate lines following the interface
address with which they are associated.
If the
.Fl f Ar address_family
option (with the
.Fl s
option) or the
.Fl p Ar protocol
option is present, show per-interface statistics on all interfaces
for the specified
.Ar address_family
or
.Ar protocol ,
respectively.
.It Fl L
Don't show link-level routes (e.g., IPv4 ARP or IPv6 neighbour cache).
.It Fl l
With the
.Fl g
option, display wider fields for the IPv6 multicast routing table
.Qq Origin
and
.Qq Group
columns.
.It Fl M Ar core
Use
.Xr kvm 3
instead of
.Xr sysctl 3
to retrieve information and
extract values associated with the name list from the specified core.
If the
.Fl M
option is not given but the
.Fl N
option is given, the default
.Pa /dev/mem
is used.
.It Fl m
Show statistics recorded by the mbuf memory management routines
(the network manages a private pool of memory buffers).
If the kernel option
.Cd options MBUFTRACE
is set, extra info can be retrieved with
.Fl mssv .
See also
.Xr options 4 .
.It Fl N Ar system
Use
.Xr kvm 3
instead of
.Xr sysctl 3
to retrieve information and extract the name list from the specified system.
For the default behavior when only
.Fl M
option is given, see the description about when
.Fa execfile
is
.Dv NULL
in
.Xr kvm_openfiles 3 .
.It Fl n
Show network addresses and ports as numbers (normally
.Nm
interprets addresses and ports and attempts to display them
symbolically).
This option may be used with any of the display formats.
.It Fl P Ar pcbaddr
Dump the contents of the protocol control block (PCB) located at kernel
virtual address
.Ar pcbaddr .
This address may be obtained using the
.Fl A
flag.
The default protocol is TCP, but may be overridden using the
.Fl p
flag.
.It Fl p Ar protocol
Show statistics about
.Ar protocol  ,
which is either a well-known name for a protocol or an alias for it.
Some protocol names and aliases are listed in the file
.Pa /etc/protocols .
A null response typically means that there are no interesting numbers to
report.
The program will complain if
.Ar protocol
is unknown or if there is no statistics routine for it.
.It Fl q
Show software interrupt queue setting/statistics for all protocols.
.It Fl r
Show the routing tables.
When
.Fl s
is also present, show routing statistics instead.
.It Fl S
Show network addresses as numbers (as with
.Fl n ,
but show ports symbolically).
.It Fl s
Show per-protocol statistics.
If this option is repeated, counters with a value of zero are suppressed.
.It Fl T
Show MPLS Tags for the routing tables.
If multiple tags exists, they will
be comma separated, first tag being the BoS one.
.It Fl t
With the
.Fl i
option, display the current value of the watchdog timer function.
.It Fl v
Show extra (verbose) detail for the routing tables
.Pq Fl r ,
or avoid truncation of long addresses.
.It Fl w Ar wait
Show network interface statistics at intervals of
.Ar wait
seconds.
.It Fl X
Force use of
.Xr sysctl 3
when retrieving information.
Some features of
.Nm
may not be (fully) supported when using
.Xr sysctl 3 .
This flag forces the use of the latter regardless, and emits a message if a
not yet fully supported feature is used in conjunction with it.
This flag might be removed at any time; do not rely on its presence.
.El
.Pp
The default display, for active sockets, shows the local
and remote addresses, send and receive queue sizes (in bytes), protocol,
and the internal state of the protocol.
Address formats are of the form ``host.port'' or ``network.port''
if a socket's address specifies a network but no specific host address.
When known the host and network addresses are displayed symbolically
according to the data bases
.Pa /etc/hosts
and
.Pa /etc/networks ,
respectively.
If a symbolic name for an address is unknown, or if
the
.Fl n
option is specified, the address is printed numerically, according
to the address family.
For more information regarding
the Internet ``dot format,''
refer to
.Xr inet 3 ) .
Unspecified,
or ``wildcard'', addresses and ports appear as ``*''.
You can use the
.Xr fstat 1
command to find out which process or processes hold references to a socket.
.Pp
The interface display provides a table of cumulative
statistics regarding packets transferred, errors, and collisions.
The network addresses of the interface
and the maximum transmission unit (``mtu'') are also displayed.
.Pp
The routing table display indicates the available routes and
their status.
Each route consists of a destination host or network
and a gateway to use in forwarding packets.
The flags field shows
a collection of information about the route stored as
binary choices.
The individual flags are discussed in more
detail in the
.Xr route 8
and
.Xr route 4
manual pages.
.Pp
Direct routes are created for each
interface attached to the local host;
the gateway field for such entries shows the address of the outgoing interface.
The refcnt field gives the
current number of active uses of the route.
Connection oriented
protocols normally hold on to a single route for the duration of
a connection while connectionless protocols obtain a route while sending
to the same destination.
The use field provides a count of the number of packets
sent using that route.
The mtu entry shows the mtu associated with
that route.
This mtu value is used as the basis for the TCP maximum
segment size.
The 'L' flag appended to the mtu value indicates that
the value is locked, and that path mtu discovery is turned off for
that route.
A
.Sq -
indicates that the mtu for this route has not been set, and a default
TCP maximum segment size will be used.
The interface entry indicates
the network interface used for the route.
.Pp
When
.Nm
is invoked with the
.Fl w
option and a
.Ar wait
interval argument, it displays a running count of statistics related to
network interfaces.
An obsolescent version of this option used a numeric parameter
with no option, and is currently supported for backward compatibility.
This display consists of a column for the primary interface (the first
interface found during autoconfiguration) and a column summarizing
information for all interfaces.
The primary interface may be replaced with another interface with the
.Fl I
option.
The first line of each screen of information contains a summary since the
system was last rebooted.
Subsequent lines of output show values
accumulated over the preceding interval.
.Pp
The first character of the flags column in the
.Fl B
option shows the status of the
.Xr bpf 4
descriptor which has three different values:
Idle ('I'), Waiting ('W') and Timed Out ('T').
The second character indicates whether the promisc flag is set.
The third character indicates the status of the immediate mode.
The fourth character indicates whether the peer will have the ability
to see the packets sent.
And the fifth character shows the header complete flag status.
.Sh SEE ALSO
.Xr fstat 1 ,
.Xr nfsstat 1 ,
.Xr ps 1 ,
.Xr sockstat 1 ,
.Xr vmstat 1 ,
.Xr inet 3 ,
.Xr kvm 3 ,
.Xr kvm_openfiles 3 ,
.Xr sysctl 3 ,
.Xr bpf 4 ,
.Xr options 4 ,
.Xr route 4 ,
.Xr hosts 5 ,
.Xr networks 5 ,
.Xr protocols 5 ,
.Xr services 5 ,
.Xr ifmcstat 8 ,
.Xr iostat 8 ,
.Xr route 8 ,
.Xr trpt 8
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.2 .
IPv6 support was added by WIDE/KAME project.
.\" .Sh FILES
.\" .Bl -tag -width /dev/mem -compact
.\" .It Pa /netbsd
.\" default kernel namelist
.\" .It Pa /dev/mem
.\" default memory file
.\" .El
.Sh BUGS
The notion of errors is ill-defined.