1400 lines
31 KiB
Text
1400 lines
31 KiB
Text
.TH IP 3
|
|
.SH NAME
|
|
ip, esp, gre, icmp, icmpv6, ipmux, rudp, tcp, udp, il \- network protocols over IP
|
|
.SH SYNOPSIS
|
|
.nf
|
|
.2C
|
|
.B bind -a #I\fIspec\fP /net
|
|
.sp 0.3v
|
|
.B /net/ipifc
|
|
.B /net/ipifc/clone
|
|
.B /net/ipifc/stats
|
|
.BI /net/ipifc/ n
|
|
.BI /net/ipifc/ n /status
|
|
.BI /net/ipifc/ n /ctl
|
|
\&...
|
|
.sp 0.3v
|
|
.B /net/arp
|
|
.B /net/bootp
|
|
.B /net/iproute
|
|
.B /net/ipselftab
|
|
.B /net/log
|
|
.B /net/ndb
|
|
.sp 0.3v
|
|
.B /net/esp
|
|
.B /net/gre
|
|
.B /net/icmp
|
|
.B /net/icmpv6
|
|
.B /net/ipmux
|
|
.B /net/rudp
|
|
.B /net/tcp
|
|
.B /net/udp
|
|
.B /net/il
|
|
.sp 0.3v
|
|
.B /net/tcp/clone
|
|
.B /net/tcp/stats
|
|
.BI /net/tcp/ n
|
|
.BI /net/tcp/ n /data
|
|
.BI /net/tcp/ n /ctl
|
|
.BI /net/tcp/ n /local
|
|
.BI /net/tcp/ n /remote
|
|
.BI /net/tcp/ n /status
|
|
.BI /net/tcp/ n /listen
|
|
\&...
|
|
.1C
|
|
.fi
|
|
.SH DESCRIPTION
|
|
The
|
|
.I ip
|
|
device provides the interface to Internet Protocol stacks.
|
|
.I Spec
|
|
is an integer starting from 0 identifying a stack.
|
|
Each stack implements IPv4 and IPv6.
|
|
Each stack is independent of all others:
|
|
the only information transfer between them is via programs that
|
|
mount multiple stacks.
|
|
Normally a system uses only one stack.
|
|
However multiple stacks can be used for debugging
|
|
new IP networks or implementing firewalls or proxy
|
|
services.
|
|
.PP
|
|
All addresses used are 16-byte IPv6 addresses.
|
|
IPv4 addresses are a subset of the IPv6 addresses and both standard
|
|
.SM ASCII
|
|
formats are accepted.
|
|
In binary representation, all v4 addresses start with the 12 bytes, in hex:
|
|
.IP
|
|
.EX
|
|
00 00 00 00 00 00 00 00 00 00 ff ff
|
|
.EE
|
|
.
|
|
.SS "Configuring interfaces
|
|
Each stack may have multiple interfaces and each interface
|
|
may have multiple addresses.
|
|
The
|
|
.B /net/ipifc
|
|
directory contains a
|
|
.B clone
|
|
file, a
|
|
.B stats
|
|
file, and numbered subdirectories for each physical interface.
|
|
.PP
|
|
Opening the
|
|
.B clone
|
|
file reserves an interface.
|
|
The file descriptor returned from the
|
|
.IR open (2)
|
|
will point to the control file,
|
|
.BR ctl ,
|
|
of the newly allocated interface.
|
|
Reading
|
|
.B ctl
|
|
returns a text string representing the number of the interface.
|
|
Writing
|
|
.B ctl
|
|
alters aspects of the interface.
|
|
The possible
|
|
.I ctl
|
|
messages are those described under
|
|
.B "Protocol directories"
|
|
below and these:
|
|
.TF "\fLbind loopback\fR"
|
|
.PD
|
|
.
|
|
.\" from devip.c
|
|
.
|
|
.TP
|
|
.BI "bind ether " path
|
|
Treat the device mounted at
|
|
.I path
|
|
as an Ethernet medium carrying IP and ARP packets
|
|
and associate it with this interface.
|
|
The kernel will
|
|
.IR dial (2)
|
|
.IR path !0x800,
|
|
.IR path !0x86DD
|
|
and
|
|
.IR path !0x806
|
|
and use the three connections for IPv4, IPv6 and
|
|
ARP respectively.
|
|
.TP
|
|
.B "bind pkt
|
|
Treat this interface as a packet interface. Assume
|
|
a user program will read and write the
|
|
.I data
|
|
file to receive and transmit IP packets to the kernel.
|
|
This is used by programs such as
|
|
.IR ppp (8)
|
|
to mediate IP packet transfer between the kernel and
|
|
a PPP encoded device.
|
|
.TP
|
|
.BI "bind netdev " path
|
|
Treat this interface as a packet interface.
|
|
The kernel will open
|
|
.I path
|
|
and read and write the resulting file descriptor
|
|
to receive and transmit IP packets.
|
|
.TP
|
|
.BI "bind loopback "
|
|
Treat this interface as a local loopback. Anything
|
|
written to it will be looped back.
|
|
.
|
|
.\" from ipifc.c
|
|
.
|
|
.TP
|
|
.B "unbind
|
|
Disassociate the physical device from an IP interface.
|
|
.TP
|
|
.BI add\ "local mask remote mtu " proxy|trans
|
|
.PD 0
|
|
.TP
|
|
.BI try\ "local mask remote mtu " proxy|trans
|
|
.PD
|
|
Add a local IP address to the interface.
|
|
.I Try
|
|
adds the
|
|
.I local
|
|
address as a tentative address
|
|
if it's an IPv6 address.
|
|
The
|
|
.IR mask ,
|
|
.IR remote ,
|
|
.IR mtu ,
|
|
.IR proxy ,
|
|
and
|
|
.R trans
|
|
arguments are all optional.
|
|
The default
|
|
.I mask
|
|
is the class mask for the local address.
|
|
The default
|
|
.I remote
|
|
address is
|
|
.I local
|
|
ANDed with
|
|
.IR mask .
|
|
The default
|
|
.I mtu
|
|
(maximum transmission unit)
|
|
is 1514 for Ethernet and 4096 for packet media.
|
|
The
|
|
.I mtu
|
|
is the size in bytes of the largest packet that this interface can send.
|
|
Specifying a
|
|
.I mtu
|
|
of 0 will use the default.
|
|
.IR Proxy ,
|
|
if specified, means that this machine should answer
|
|
ARP requests for the remote address.
|
|
.IR Ppp (8)
|
|
does this to make remote machines appear
|
|
to be connected to the local Ethernet.
|
|
The
|
|
.I trans
|
|
argument enables source address translation
|
|
for packets routed to the interface.
|
|
Adding the special null-address
|
|
.B "0.0.0.0"
|
|
or
|
|
.B "::"
|
|
in
|
|
.I local
|
|
to a interface makes the ip stack accept all incoming
|
|
connections regardless of the destination IP address.
|
|
This is used temporarily by
|
|
.IR ipconfig (8)
|
|
to accept DHCP answers when no IP address
|
|
has been assigned yet. This can also be used
|
|
to implement a NAT gateway by accepting all
|
|
incoming connections and proxying them with
|
|
.IR trampoline (8)
|
|
to a different ip stack.
|
|
.TP
|
|
.BI remove\ "local mask"
|
|
Remove a local IP address from an interface.
|
|
.TP
|
|
.BI mtu\ n
|
|
Set the maximum transfer unit for this device to
|
|
.IR n .
|
|
The mtu is the maximum size of the packet including any
|
|
medium-specific headers.
|
|
.TP
|
|
.BI speed\ n
|
|
Set the maximum transmit speed in bits per second.
|
|
.TP
|
|
.BI delay\ n
|
|
Set the maximum burst delay in milliseconds. (Default is 40ms)
|
|
When
|
|
.B speed
|
|
has been set and packets in flight exceed the maximum burst
|
|
delay then packets send on the interface are discarded until
|
|
the load drops below the maximum.
|
|
.TP
|
|
.BI iprouting\ n
|
|
Allow
|
|
.RI ( n
|
|
is missing or non-zero) or disallow
|
|
.RI ( n
|
|
is 0) forwarding packets between this interface and others.
|
|
.TP
|
|
.BI reflect\ n
|
|
When forwarding, allow packets from this interface to be
|
|
echoed back on the same interface.
|
|
.TP
|
|
.BI reassemble\ n
|
|
Reassemble IP fragments before forwarding to this interface
|
|
.
|
|
.\" remainder from netif.c (thus called from devether.c),
|
|
.\" except add6 and ra6 from ipifc.c
|
|
.
|
|
.TP
|
|
.B bridge
|
|
Enable bridging (see
|
|
.IR bridge (3)).
|
|
.TP
|
|
.B promiscuous
|
|
Set the interface into promiscuous mode,
|
|
which makes it accept all incoming packets,
|
|
whether addressed to it or not.
|
|
.TP
|
|
.BI "connect " type
|
|
marks the Ethernet packet
|
|
.I type
|
|
as being in use, if not already in use
|
|
on this interface.
|
|
A
|
|
.I type
|
|
of -1 means `all' but appears to be a no-op.
|
|
.TP
|
|
.BI addmulti\ Media-addr
|
|
Treat the multicast
|
|
.I Media-addr
|
|
on this interface as a local address.
|
|
.TP
|
|
.BI remmulti\ Media-addr
|
|
Remove the multicast address
|
|
.I Media-addr
|
|
from this interface.
|
|
.TP
|
|
.B scanbs
|
|
Make the wireless interface scan for base stations.
|
|
.TP
|
|
.B headersonly
|
|
Set the interface to pass only packet headers, not data too.
|
|
.
|
|
.\" remainder from ipifc.c; tedious, so put them last
|
|
.
|
|
.TP
|
|
.BI "add6 " "v6addr pfx-len [onlink auto validlt preflt]"
|
|
Add the local IPv6 address
|
|
.I v6addr
|
|
with prefix length
|
|
.I pfx-len
|
|
to this interface.
|
|
See RFC 2461 §6.2.1 for more detail.
|
|
The remaining arguments are optional:
|
|
.RS
|
|
.TF "\fIonlink\fR"
|
|
.TP
|
|
.I onlink
|
|
flag: address is `on-link'
|
|
.TP
|
|
.I auto
|
|
flag: autonomous
|
|
.TP
|
|
.I validlt
|
|
valid life-time in seconds
|
|
.TP
|
|
.I preflt
|
|
preferred life-time in seconds
|
|
.RE
|
|
.PD
|
|
.TP
|
|
.B remove6
|
|
Remove local IPv6 addresses that have expired ther
|
|
valid life-time.
|
|
.TP
|
|
.BI "ra6 " "keyword value ..."
|
|
Set IPv6 router advertisement (RA) parameter
|
|
.IR keyword 's
|
|
.IR value .
|
|
Known
|
|
.IR keyword s
|
|
and the meanings of their values follow.
|
|
See RFC 2461 §6.2.1 for more detail.
|
|
Flags are true iff non-zero.
|
|
.RS
|
|
.TF "\fLreachtime\fR"
|
|
.TP
|
|
.B recvra
|
|
flag: receive and process RAs.
|
|
.TP
|
|
.B sendra
|
|
flag: generate and send RAs.
|
|
.TP
|
|
.B mflag
|
|
flag: ``Managed address configuration'',
|
|
goes into RAs.
|
|
.TP
|
|
.B oflag
|
|
flag: ``Other stateful configuration'',
|
|
goes into RAs.
|
|
.TP
|
|
.B maxraint
|
|
``maximum time allowed between sending unsolicited multicast''
|
|
RAs from the interface, in ms.
|
|
.TP
|
|
.B minraint
|
|
``minimum time allowed between sending unsolicited multicast''
|
|
RAs from the interface, in ms.
|
|
.TP
|
|
.B linkmtu
|
|
``value to be placed in MTU options sent by the router.''
|
|
Zero indicates none.
|
|
.TP
|
|
.B reachtime
|
|
sets the Reachable Time field in RAs sent by the router.
|
|
``Zero means unspecified (by this router).''
|
|
.TP
|
|
.B rxmitra
|
|
sets the Retrans Timer field in RAs sent by the router.
|
|
``Zero means unspecified (by this router).''
|
|
.TP
|
|
.B ttl
|
|
default value of the Cur Hop Limit field in RAs sent by the router.
|
|
Should be set to the ``current diameter of the Internet.''
|
|
``Zero means unspecified (by this router).''
|
|
.TP
|
|
.B routerlt
|
|
sets the Router Lifetime field of RAs sent from the interface, in ms.
|
|
Zero means the router is not to be used as a default router.
|
|
.PD
|
|
.RE
|
|
.PP
|
|
Reading the interface's
|
|
.I status
|
|
file returns information about the interface. The first line
|
|
is composed of white-space-separated fields, the first two
|
|
fields are: device and maxmtu. Subsequent lines list the
|
|
ip addresses assigned to that inferface. The colums are:
|
|
ip address, network mask, network address and valid/preferred
|
|
life times in milliseconds. See
|
|
.I readipifc
|
|
in
|
|
.IR ip (2).
|
|
.
|
|
.SS "Routing
|
|
The file
|
|
.I iproute
|
|
controls information about IP routing.
|
|
When read, it returns one line per routing entry.
|
|
Each line contains eight white-space-separated fields:
|
|
target address, target mask, address of next hop, flags,
|
|
tag, interface number, source address, source mask.
|
|
The entry used for routing an IP packet is the one with
|
|
the longest destination and source mask for which
|
|
destination address ANDed with target mask equals the
|
|
target and also the source ANDed with the source mask equals
|
|
the source address.
|
|
The one-character flags are:
|
|
.TF m
|
|
.TP
|
|
.B 4
|
|
IPv4 route
|
|
.TP
|
|
.B 6
|
|
IPv6 route
|
|
.TP
|
|
.B i
|
|
local interface
|
|
.TP
|
|
.B b
|
|
broadcast address
|
|
.TP
|
|
.B u
|
|
local unicast address
|
|
.TP
|
|
.B m
|
|
multicast route
|
|
.TP
|
|
.B p
|
|
point-to-point route
|
|
.TP
|
|
.B t
|
|
network source address translation
|
|
.PD
|
|
.PP
|
|
The tag is an arbitrary, up to 4 character, string. It is normally used to
|
|
indicate what routing protocol originated the route.
|
|
.PP
|
|
Writing to
|
|
.B /net/iproute
|
|
changes the route table. The messages are:
|
|
.TF "\fLtag \fIstring\fR"
|
|
.PD
|
|
.TP
|
|
.BI flush\ tag
|
|
Remove routes of the specified tag, or all routes if
|
|
.I tag
|
|
is omitted.
|
|
.TP
|
|
.BI tag\ string
|
|
Associate the tag,
|
|
.IR string ,
|
|
with all subsequent routes added via this file descriptor.
|
|
.TP
|
|
.BI add\ "target mask nexthop"
|
|
.TP
|
|
.BI add\ "target mask nexthop interface"
|
|
.TP
|
|
.BI add\ "target mask nexthop source smask"
|
|
.TP
|
|
.BI add\ "target mask nexthop interface source smask"
|
|
.TP
|
|
.BI add\ "target mask nexthop flags interface source smask"
|
|
.TP
|
|
.BI add\ "target mask nexthop flags tag interface source smask"
|
|
Add the route to the table. If one already exists with the
|
|
same target and mask, replace it. The
|
|
.I interface
|
|
can be given as either the interface number or a local
|
|
IP address on the desired interface or as a
|
|
.B "-"
|
|
when unspecified.
|
|
.TP
|
|
.BI remove\ "target mask"
|
|
.TP
|
|
.BI remove\ "target mask nexthop"
|
|
.TP
|
|
.BI remove\ "target mask source smask"
|
|
.TP
|
|
.BI remove\ "target mask nexthop source smask"
|
|
.TP
|
|
.BI remove\ "target mask nexthop interface source smask"
|
|
.TP
|
|
.BI remove\ "target mask nexthop flags interface source smask"
|
|
.TP
|
|
.BI remove\ "target mask nexthop flags tag interface source smask"
|
|
Remove the matching route.
|
|
.
|
|
.SS "Address resolution
|
|
The file
|
|
.B /net/arp
|
|
controls information about address resolution.
|
|
The kernel automatically updates the v4 ARP and v6 Neighbour Discovery
|
|
information for Ethernet interfaces.
|
|
When read, the file returns one line per address containing the
|
|
type of medium, the status of the entry (OK, WAIT), the IP
|
|
address, the medium address and the IP address of the interface
|
|
where the entry is valid.
|
|
Writing to
|
|
.B /net/arp
|
|
administers the ARP information.
|
|
The control messages are:
|
|
.TF "\fLdel \fIIP-addr\fR"
|
|
.PD
|
|
.TP
|
|
.B flush
|
|
Remove all entries.
|
|
.TP
|
|
.BI add\ "type IP-addr Media-addr Interface-IP-addr"
|
|
Add an entry or replace an existing one for the
|
|
same IP address. The optional interface IP address specifies the
|
|
interface where the ARP entry will be valid. This is needed
|
|
for IPv6 link local addresses.
|
|
.TP
|
|
.BI del\ "IP-addr"
|
|
Delete an individual entry.
|
|
.PP
|
|
ARP entries do not time out. The ARP table is a
|
|
cache with an LRU replacement policy. The IP stack
|
|
listens for all ARP requests and, if the requester is in
|
|
the table, the entry is updated.
|
|
Also, whenever a new address is configured onto an
|
|
Ethernet, an ARP request is sent to help
|
|
update the table on other systems.
|
|
.PP
|
|
Currently, the only medium type is
|
|
.BR ether .
|
|
.br
|
|
.ne 3
|
|
.
|
|
.SS "Debugging and stack information
|
|
If any process is holding
|
|
.B /net/log
|
|
open, the IP stack queues debugging information to it.
|
|
This is intended primarily for debugging the IP stack.
|
|
The information provided is implementation-defined;
|
|
see the source for details. Generally, what is returned is error messages
|
|
about bad packets.
|
|
.PP
|
|
Writing to
|
|
.B /net/log
|
|
controls debugging. The control messages are:
|
|
.TF "\fLclear \fIarglist\fR"
|
|
.PD
|
|
.TP
|
|
.BI set\ arglist
|
|
.I Arglist
|
|
is a space-separated list of items for which to enable debugging.
|
|
The possible items are:
|
|
.BR ppp ,
|
|
.BR ip ,
|
|
.BR fs ,
|
|
.BR tcp ,
|
|
.BR il ,
|
|
.BR icmp ,
|
|
.BR udp ,
|
|
.BR compress ,
|
|
.BR ilmsg ,
|
|
.BR gre ,
|
|
.BR tcpwin ,
|
|
.BR tcprxmt ,
|
|
.BR udpmsg ,
|
|
.BR ipmsg ,
|
|
and
|
|
.BR esp .
|
|
.TP
|
|
.BI clear\ arglist
|
|
.I Arglist
|
|
is a space-separated list of items for which to disable debugging.
|
|
.TP
|
|
.BI only\ addr
|
|
If
|
|
.I addr
|
|
is non-zero, restrict debugging to only those
|
|
packets whose source or destination is that
|
|
address.
|
|
.PP
|
|
The file
|
|
.B /net/ndb
|
|
can be read or written by
|
|
programs. It is normally used by
|
|
.IR ipconfig (8)
|
|
to leave configuration information for other programs
|
|
such as
|
|
.B dns
|
|
and
|
|
.B cs
|
|
(see
|
|
.IR ndb (8)).
|
|
.B /net/ndb
|
|
may contain up to 1024 bytes.
|
|
.PP
|
|
The file
|
|
.B /net/ipselftab
|
|
is a read-only file containing all the IP addresses
|
|
considered local. Each line in the file contains
|
|
three white-space-separated fields: IP address, usage count,
|
|
and flags. The usage count is the number of interfaces to which
|
|
the address applies. The flags are the same as for routing
|
|
entries.
|
|
.br
|
|
.ne 3
|
|
.
|
|
.SS "Protocol directories
|
|
The
|
|
.I ip
|
|
device
|
|
supports IP as well as several protocols that run over it:
|
|
TCP, UDP, RUDP, ICMP, IL, GRE, and ESP.
|
|
TCP and UDP provide the standard Internet
|
|
protocols for reliable stream and unreliable datagram
|
|
communication.
|
|
RUDP is a locally-developed reliable datagram protocol based on UDP.
|
|
ICMP is IP's catch-all control protocol used to send
|
|
low level error messages and to implement
|
|
.IR ping (8).
|
|
GRE is a general encapsulation protocol.
|
|
ESP is the encapsulation protocol for IPsec.
|
|
IL provides a reliable datagram service for communication
|
|
between Plan 9 machines but is now deprecated.
|
|
.PP
|
|
Each protocol is a subdirectory of the IP stack.
|
|
The top level directory of each protocol contains a
|
|
.B clone
|
|
file, a
|
|
.B stats
|
|
file, and subdirectories numbered from zero to the number of connections
|
|
opened for this protocol.
|
|
.PP
|
|
Opening the
|
|
.B clone
|
|
file reserves a connection. The file descriptor returned from the
|
|
.IR open (2)
|
|
will point to the control file,
|
|
.BR ctl ,
|
|
of the newly allocated connection.
|
|
Reading
|
|
.B ctl
|
|
returns a text
|
|
string representing the number of the
|
|
connection.
|
|
Connections may be used either to listen for incoming calls
|
|
or to initiate calls to other machines.
|
|
.PP
|
|
A connection is controlled by writing text strings to the associated
|
|
.B ctl
|
|
file.
|
|
After a connection has been established data may be read from
|
|
and written to
|
|
.BR data .
|
|
A connection can be actively established using the
|
|
.B connect
|
|
message (see also
|
|
.IR dial (2)).
|
|
A connection can be established passively by first
|
|
using an
|
|
.B announce
|
|
message (see
|
|
.IR dial (2))
|
|
to bind to a local port and then
|
|
opening the
|
|
.B listen
|
|
file (see
|
|
.IR dial (2))
|
|
to receive incoming calls.
|
|
.PP
|
|
The following control messages are supported:
|
|
.TF "\fLremmulti \fIip\fR"
|
|
.PD
|
|
.TP
|
|
.BI connect\ ip-address ! port "!r " local
|
|
Establish a connection to the remote
|
|
.I ip-address
|
|
and
|
|
.IR port .
|
|
If
|
|
.I local
|
|
is specified, it is used as the local port number.
|
|
If
|
|
.I local
|
|
is not specified but
|
|
.B !r
|
|
is, the system will allocate
|
|
a restricted port number (less than 1024) for the connection to allow communication
|
|
with Unix
|
|
.B login
|
|
and
|
|
.B exec
|
|
services.
|
|
Otherwise a free port number starting at 5000 is chosen.
|
|
The connect fails if the combination of local and remote address/port pairs
|
|
are already assigned to another port.
|
|
.TP
|
|
.BI announce\ [ip-address ! ]port
|
|
Set the local IP address and port number and accept calls there. If
|
|
ip-address is left out, accept calls on any address. If port is 0, a
|
|
port is automatically choosen that is not yet announced.
|
|
If the address is
|
|
.LR * ,
|
|
accept calls on any address.
|
|
If port is
|
|
.LR * ,
|
|
accept calls on any port.
|
|
If port is
|
|
.LR * ,
|
|
and the address is left out, accept calls on any address and port.
|
|
.B Announce
|
|
fails if the connection is already announced.
|
|
.TP
|
|
.BI bind\ [ip-address ! ]port
|
|
Set the local IP address and port number like for a server connection
|
|
similar to the
|
|
.B announce
|
|
command.
|
|
If ip-address is left out, an address is automatically selected. If
|
|
port is 0, a port is automatically choosen that is not yet announced.
|
|
This command has no actual effect, beyond remembering the parameters
|
|
and possibly selecting an unused port.
|
|
The commands
|
|
.B announce
|
|
and
|
|
.B connect
|
|
reset both the local address and the port according to their own
|
|
parameters.
|
|
This command also does
|
|
.B not
|
|
reserve the IP address and port, another connection can use them, even
|
|
while they are registered in a connection by this command.
|
|
This exists to support emulation of BSD sockets by the APE libraries
|
|
(see
|
|
.IR pcc (1))
|
|
and is not otherwise used.
|
|
.\" this is gone
|
|
.\" .TP
|
|
.\" .BI backlog\ n
|
|
.\" Set the maximum number of unanswered (queued) incoming
|
|
.\" connections to an announced port to
|
|
.\" .IR n .
|
|
.\" By default
|
|
.\" .I n
|
|
.\" is set to five. If more than
|
|
.\" .I n
|
|
.\" connections are pending,
|
|
.\" further requests for a service will be rejected.
|
|
.TP
|
|
.BI ttl\ n
|
|
Set the time to live IP field in outgoing packets to
|
|
.IR n .
|
|
.TP
|
|
.BI tos\ n
|
|
Set the service type IP field in outgoing packets to
|
|
.IR n .
|
|
.TP
|
|
.B ignoreadvice
|
|
Don't break (UDP) connections because of ICMP errors.
|
|
.TP
|
|
.BI addmulti\ "ifc-ip [ mcast-ip ]"
|
|
Treat
|
|
.I ifc-ip
|
|
on this multicast interface as a local address.
|
|
If
|
|
.I mcast-ip
|
|
is present,
|
|
use it as the interface's multicast address.
|
|
.TP
|
|
.BI remmulti\ ip
|
|
Remove the address
|
|
.I ip
|
|
from this multicast interface.
|
|
.PP
|
|
Port numbers must be in the range 1 to 32767.
|
|
.PP
|
|
Several files report the status of a
|
|
connection.
|
|
The
|
|
.B remote
|
|
and
|
|
.B local
|
|
files contain the IP address and port number for the remote and local side of the
|
|
connection. The
|
|
.B status
|
|
file contains protocol-dependent information to help debug network connections.
|
|
On receiving and error or EOF reading or writing the
|
|
.B data
|
|
file, the
|
|
.B err
|
|
file contains the reason for error.
|
|
.PP
|
|
A process may accept incoming connections by
|
|
.IR open (2)ing
|
|
the
|
|
.B listen
|
|
file.
|
|
The
|
|
.B open
|
|
will block until a new connection request arrives.
|
|
Then
|
|
.B open
|
|
will return an open file descriptor which points to the control file of the
|
|
newly accepted connection.
|
|
This procedure will accept all calls for the
|
|
given protocol.
|
|
See
|
|
.IR dial (2).
|
|
.
|
|
.SS TCP
|
|
TCP connections are reliable point-to-point byte streams; there are no
|
|
message delimiters.
|
|
A connection is determined by the address and port numbers of the two
|
|
ends.
|
|
TCP
|
|
.B ctl
|
|
files support the following additional messages:
|
|
.TF "\fLkeepalive\fI n\fR"
|
|
.PD
|
|
.TP
|
|
.B hangup
|
|
close down this TCP connection
|
|
.TP
|
|
.B close
|
|
graceful hangup
|
|
.TP
|
|
.BI keepalive \ n
|
|
turn on keep alive messages.
|
|
.IR N ,
|
|
if given, is the milliseconds between keepalives
|
|
(default 30000).
|
|
.TP
|
|
.BI checksum \ n
|
|
emit TCP checksums of zero if
|
|
.I n
|
|
is zero; otherwise, and by default,
|
|
TCP checksums are computed and sent normally.
|
|
.TP
|
|
.BI tcpporthogdefense \ onoff
|
|
.I onoff
|
|
of
|
|
.L on
|
|
enables the TCP port-hog defense for all TCP connections;
|
|
.I onoff
|
|
of
|
|
.L off
|
|
disables it.
|
|
The defense is a solution to hijacked systems staking out ports
|
|
as a form of denial-of-service attack.
|
|
To avoid stateless TCP conversation hogs,
|
|
.I ip
|
|
picks a TCP sequence number at random for keepalives.
|
|
If that number gets acked by the other end,
|
|
.I ip
|
|
shuts down the connection.
|
|
Some firewalls,
|
|
notably ones that perform stateful inspection,
|
|
discard such out-of-specification keepalives,
|
|
so connections through such firewalls
|
|
will be killed after five minutes
|
|
by the lack of keepalives.
|
|
.
|
|
.SS UDP
|
|
UDP connections carry unreliable and unordered datagrams. A read from
|
|
.B data
|
|
will return the next datagram, discarding anything
|
|
that doesn't fit in the read buffer.
|
|
A write is sent as a single datagram.
|
|
.PP
|
|
By default, a UDP connection is a point-to-point link.
|
|
Either a
|
|
.B connect
|
|
establishes a local and remote address/port pair or
|
|
after an
|
|
.BR announce ,
|
|
each datagram coming from a different remote address/port pair
|
|
establishes a new incoming connection.
|
|
However, many-to-one semantics is also possible.
|
|
.PP
|
|
If, after an
|
|
.BR announce ,
|
|
the message
|
|
.L headers
|
|
is written to
|
|
.BR ctl ,
|
|
then all messages sent to the announced port
|
|
are received on the announced connection prefixed
|
|
with the corresponding structure,
|
|
declared in
|
|
.BR <ip.h> :
|
|
.IP
|
|
.EX
|
|
typedef struct Udphdr Udphdr;
|
|
struct Udphdr
|
|
{
|
|
uchar raddr[16]; /* V6 remote address and port */
|
|
uchar laddr[16]; /* V6 local address and port */
|
|
uchar ifcaddr[16]; /* V6 interface address (receive only) */
|
|
uchar rport[2]; /* remote port */
|
|
uchar lport[2]; /* local port */
|
|
};
|
|
.EE
|
|
.PP
|
|
Before a write, a user must prefix a similar structure to each message.
|
|
The system overrides the user specified local port with the announced
|
|
one. If the user specifies an address that isn't a unicast address in
|
|
.BR /net/ipselftab ,
|
|
that too is overridden.
|
|
Since the prefixed structure is the same in read and write, it is relatively
|
|
easy to write a server that responds to client requests by just copying new
|
|
data into the message body and then writing back the same buffer that was
|
|
read.
|
|
.PP
|
|
In this case (writing
|
|
.L headers
|
|
to the
|
|
.I ctl
|
|
file),
|
|
no
|
|
.I listen
|
|
nor
|
|
.I accept
|
|
is needed;
|
|
otherwise,
|
|
the usual sequence of
|
|
.IR announce ,
|
|
.IR listen ,
|
|
.I accept
|
|
must be executed before performing I/O on the corresponding
|
|
.I data
|
|
file.
|
|
.
|
|
.SS RUDP
|
|
RUDP is a reliable datagram protocol based on UDP,
|
|
currently only for IPv4.
|
|
Packets are delivered in order.
|
|
RUDP does not support
|
|
.BR listen .
|
|
One must write either
|
|
.L connect
|
|
or
|
|
.L announce
|
|
followed immediately by
|
|
.L headers
|
|
to
|
|
.BR ctl .
|
|
.PP
|
|
Unlike TCP, the reboot of one end of a connection does
|
|
not force a closing of the connection. Communications will
|
|
resume when the rebooted machine resumes talking. Any unacknowledged
|
|
packets queued before the reboot will be lost. A reboot can
|
|
be detected by reading the
|
|
.B err
|
|
file. It will contain the message
|
|
.IP
|
|
.BI hangup\ address ! port
|
|
.PP
|
|
where
|
|
.I address
|
|
and
|
|
.I port
|
|
are of the far side of the connection.
|
|
Retransmitting a datagram more than 10 times
|
|
is treated like a reboot:
|
|
all queued messages are dropped, an error is queued to the
|
|
.B err
|
|
file, and the conversation resumes.
|
|
.PP
|
|
RUDP
|
|
.I ctl
|
|
files accept the following messages:
|
|
.TF "\fLranddrop \fI[ percent ]\fR"
|
|
.TP
|
|
.B headers
|
|
Corresponds to the
|
|
.L headers
|
|
format of UDP.
|
|
.TP
|
|
.BI "hangup " "IP port"
|
|
Drop the connection to address
|
|
.I IP
|
|
and
|
|
.IR port .
|
|
.TP
|
|
.BI "randdrop " "[ percent ]"
|
|
Randomly drop
|
|
.I percent
|
|
of outgoing packets.
|
|
Default is 10%.
|
|
.
|
|
.SS ICMP
|
|
ICMP is a datagram protocol for IPv4 used to exchange control requests and
|
|
their responses with other machines' IP implementations.
|
|
ICMP is primarily a kernel-to-kernel protocol, but it is possible
|
|
to generate `echo request' and read `echo reply' packets from user programs.
|
|
.
|
|
.SS ICMPV6
|
|
ICMPv6 is the IPv6 equivalent of ICMP.
|
|
If, after an
|
|
.BR announce ,
|
|
the message
|
|
.L headers
|
|
is written to
|
|
.BR ctl ,
|
|
then before a write,
|
|
a user must prefix each message with a corresponding structure,
|
|
declared in
|
|
.BR <ip.h> :
|
|
.IP
|
|
.EX
|
|
/*
|
|
* user level icmpv6 with control message "headers"
|
|
*/
|
|
typedef struct Icmp6hdr Icmp6hdr;
|
|
struct Icmp6hdr {
|
|
uchar unused[8];
|
|
uchar laddr[IPaddrlen]; /* local address */
|
|
uchar raddr[IPaddrlen]; /* remote address */
|
|
};
|
|
.EE
|
|
.PP
|
|
In this case (writing
|
|
.L headers
|
|
to the
|
|
.I ctl
|
|
file),
|
|
no
|
|
.I listen
|
|
nor
|
|
.I accept
|
|
is needed;
|
|
otherwise,
|
|
the usual sequence of
|
|
.IR announce ,
|
|
.IR listen ,
|
|
.I accept
|
|
must be executed before performing I/O on the corresponding
|
|
.I data
|
|
file.
|
|
.
|
|
.SS IL
|
|
IL is a reliable point-to-point datagram protocol that runs over IPv4.
|
|
Like TCP, IL delivers datagrams
|
|
reliably and in order. Also like TCP, a connection is
|
|
determined by the address and port numbers of the two ends.
|
|
Like UDP, each read and write transfers a single datagram.
|
|
.PP
|
|
IL is efficient for LANs but doesn't have the
|
|
congestion control features needed for use through
|
|
the Internet.
|
|
It is no longer necessary, except to communicate with old standalone
|
|
.IR fs (4)
|
|
file servers.
|
|
Its use is now deprecated.
|
|
.
|
|
.SS GRE
|
|
GRE is the encapsulation protocol used by PPTP.
|
|
The kernel implements just enough of the protocol
|
|
to multiplex it.
|
|
Our implementation encapsulates in IPv4, per RFC 1702.
|
|
.B Announce
|
|
is not allowed in GRE, only
|
|
.BR connect .
|
|
Since GRE has no port numbers, the port number in the connect
|
|
is actually the 16 bit
|
|
.B eproto
|
|
field in the GRE header.
|
|
.PP
|
|
Reads and writes transfer a
|
|
GRE datagram starting at the GRE header.
|
|
On write, the kernel fills in the
|
|
.B eproto
|
|
field with the port number specified
|
|
in the connect message.
|
|
.br
|
|
.ne 3
|
|
.
|
|
.SS ESP
|
|
ESP is the Encapsulating Security Payload (RFC 1827, obsoleted by RFC 4303)
|
|
for IPsec (RFC 4301).
|
|
We currently implement only tunnel mode, not transport mode.
|
|
It is used to set up an encrypted tunnel between machines.
|
|
Like GRE, ESP has no port numbers. Instead, the
|
|
port number in the
|
|
.B connect
|
|
message is the SPI (Security Association Identifier (sic)).
|
|
IP packets are written to and read from
|
|
.BR data .
|
|
The kernel encrypts any packets written to
|
|
.BR data ,
|
|
appends a MAC, and prefixes an ESP header before
|
|
sending to the other end of the tunnel.
|
|
Received packets are checked against their MAC's,
|
|
decrypted, and queued for reading from
|
|
.BR data .
|
|
In the following,
|
|
.I secret
|
|
is the hexadecimal encoding of a key,
|
|
without a leading
|
|
.LR 0x .
|
|
The control messages are:
|
|
.TF "\fLesp \fIalg secret\fR"
|
|
.PD
|
|
.TP
|
|
.BI esp\ "alg secret
|
|
Encrypt with the algorithm,
|
|
.IR alg ,
|
|
using
|
|
.I secret
|
|
as the key.
|
|
Possible algorithms are:
|
|
.BR null ,
|
|
.BR des_56_cbc ,
|
|
.BR des3_cbc ,
|
|
and eventually
|
|
.BR aes_128_cbc ,
|
|
and
|
|
.BR aes_ctr .
|
|
.TP
|
|
.BI ah\ "alg secret
|
|
Use the hash algorithm,
|
|
.IR alg ,
|
|
with
|
|
.I secret
|
|
as the key for generating the MAC.
|
|
Possible algorithms are:
|
|
.BR null ,
|
|
.BR hmac_sha1_96 ,
|
|
.BR hmac_md5_96 ,
|
|
and eventually
|
|
.BR aes_xcbc_mac_96 .
|
|
.TP
|
|
.B header
|
|
Turn on header mode. Every buffer read from
|
|
.B data
|
|
starts with 4 unused bytes, and the first 4 bytes
|
|
of every buffer written to
|
|
.B data
|
|
are ignored.
|
|
.TP
|
|
.B noheader
|
|
Turn off header mode.
|
|
.
|
|
.SS "IP packet filter
|
|
The directory
|
|
.B /net/ipmux
|
|
looks like another protocol directory.
|
|
It is a packet filter built on top of IP.
|
|
Each numbered
|
|
subdirectory represents a different filter.
|
|
The connect messages written to the
|
|
.I ctl
|
|
file describe the filter. Packets matching the filter can be read on the
|
|
.B data
|
|
file. Packets written to the
|
|
.B data
|
|
file are routed to an interface and transmitted.
|
|
.PP
|
|
A filter is a semicolon-separated list of
|
|
relations. Each relation describes a portion
|
|
of a packet to match. The possible relations are:
|
|
.TF "\fLdata[\fIn\fL:\fIm\fL]=\fIexpr\fR "
|
|
.PD
|
|
.TP
|
|
.BI ver= n
|
|
the IP version must be
|
|
.IR n .
|
|
.TP
|
|
.BI proto= n
|
|
the IP protocol number must be
|
|
.IR n .
|
|
.TP
|
|
.BI data[ n : m ]= expr
|
|
bytes
|
|
.I n
|
|
through
|
|
.I m
|
|
following the IP header must match
|
|
.IR expr .
|
|
.TP
|
|
.BI iph[ n : m ]= expr
|
|
bytes
|
|
.I n
|
|
through
|
|
.I m
|
|
of the IP packet header must match
|
|
.IR expr .
|
|
.TP
|
|
.BI ifc= expr
|
|
the packet must have been received on an interface whose address
|
|
matches
|
|
.IR expr .
|
|
.TP
|
|
.BI src= expr
|
|
The source address in the packet must match
|
|
.IR expr .
|
|
.TP
|
|
.BI dst= expr
|
|
The destination address in the packet must match
|
|
.IR expr .
|
|
.PP
|
|
.I Expr
|
|
is of the form:
|
|
.TP
|
|
.I \ value
|
|
.TP
|
|
.IB \ value | value | ...
|
|
.TP
|
|
.IB \ value & mask
|
|
.TP
|
|
.IB \ value | value & mask
|
|
.PP
|
|
If a mask is given, the relevant field is first ANDed with
|
|
the mask. The result is compared against the value or list
|
|
of values for a match. In the case of
|
|
.BR ifc ,
|
|
.BR dst ,
|
|
and
|
|
.B src
|
|
the value is a dot-formatted IP address and the mask is a dot-formatted
|
|
IP mask. In the case of
|
|
.BR data ,
|
|
.B iph
|
|
and
|
|
.BR proto ,
|
|
both value and mask are strings of 2 hexadecimal digits representing
|
|
8-bit values.
|
|
.PP
|
|
A packet is delivered to only one filter.
|
|
The filters are merged into a single comparison tree.
|
|
If two filters match the same packet, the following
|
|
rules apply in order (here '>' means is preferred to):
|
|
.IP 1)
|
|
protocol > data > source > destination > interface
|
|
.IP 2)
|
|
lower data offsets > higher data offsets
|
|
.IP 3)
|
|
longer matches > shorter matches
|
|
.IP 4)
|
|
older > younger
|
|
.PP
|
|
So far this has just been used to implement a version of
|
|
OSPF in Inferno
|
|
and 6to4 tunnelling.
|
|
.br
|
|
.ne 5
|
|
.
|
|
.SS Statistics
|
|
The
|
|
.B stats
|
|
files are read only and contain statistics useful to network monitoring.
|
|
.br
|
|
.ne 12
|
|
.PP
|
|
Reading
|
|
.B /net/ipifc/stats
|
|
returns a list of 19 tagged and newline-separated fields representing:
|
|
.EX
|
|
.ft 1
|
|
.2C
|
|
.in +0.25i
|
|
forwarding status (0 and 2 mean forwarding off,
|
|
1 means on)
|
|
default TTL
|
|
input packets
|
|
input header errors
|
|
input address errors
|
|
packets forwarded
|
|
input packets for unknown protocols
|
|
input packets discarded
|
|
input packets delivered to higher level protocols
|
|
output packets
|
|
output packets discarded
|
|
output packets with no route
|
|
timed out fragments in reassembly queue
|
|
requested reassemblies
|
|
successful reassemblies
|
|
failed reassemblies
|
|
successful fragmentations
|
|
unsuccessful fragmentations
|
|
fragments created
|
|
.in -0.25i
|
|
.1C
|
|
.ft
|
|
.EE
|
|
.br
|
|
.ne 16
|
|
.PP
|
|
Reading
|
|
.B /net/icmp/stats
|
|
returns a list of 26 tagged and newline-separated fields representing:
|
|
.EX
|
|
.ft 1
|
|
.2C
|
|
.in +0.25i
|
|
messages received
|
|
bad received messages
|
|
unreachables received
|
|
time exceededs received
|
|
input parameter problems received
|
|
source quenches received
|
|
redirects received
|
|
echo requests received
|
|
echo replies received
|
|
timestamps received
|
|
timestamp replies received
|
|
address mask requests received
|
|
address mask replies received
|
|
messages sent
|
|
transmission errors
|
|
unreachables sent
|
|
time exceededs sent
|
|
input parameter problems sent
|
|
source quenches sent
|
|
redirects sent
|
|
echo requests sent
|
|
echo replies sent
|
|
timestamps sent
|
|
timestamp replies sent
|
|
address mask requests sent
|
|
address mask replies sent
|
|
.in -0.25i
|
|
.1C
|
|
.EE
|
|
.PP
|
|
Reading
|
|
.B /net/tcp/stats
|
|
returns a list of 11 tagged and newline-separated fields representing:
|
|
.EX
|
|
.ft 1
|
|
.2C
|
|
.in +0.25i
|
|
maximum number of connections
|
|
total outgoing calls
|
|
total incoming calls
|
|
number of established connections to be reset
|
|
number of currently established connections
|
|
segments received
|
|
segments sent
|
|
segments retransmitted
|
|
retransmit timeouts
|
|
bad received segments
|
|
transmission failures
|
|
.in -0.25i
|
|
.1C
|
|
.EE
|
|
.PP
|
|
Reading
|
|
.B /net/udp/stats
|
|
returns a list of 4 tagged and newline-separated fields representing:
|
|
.EX
|
|
.ft 1
|
|
.2C
|
|
.in +0.25i
|
|
datagrams received
|
|
datagrams received for bad ports
|
|
malformed datagrams received
|
|
datagrams sent
|
|
.in -0.25i
|
|
.1C
|
|
.EE
|
|
.PP
|
|
Reading
|
|
.B /net/il/stats
|
|
returns a list of 6 tagged and newline-separated fields representing:
|
|
.EX
|
|
.ft 1
|
|
.2C
|
|
.in +0.25i
|
|
checksum errors
|
|
header length errors
|
|
out of order messages
|
|
retransmitted messages
|
|
duplicate messages
|
|
duplicate bytes
|
|
.in -0.25i
|
|
.1C
|
|
.EE
|
|
.PP
|
|
Reading
|
|
.B /net/gre/stats
|
|
returns a list of 1 tagged number representing:
|
|
.EX
|
|
.ft 1
|
|
.in +0.25i
|
|
header length errors
|
|
.in -0.25i
|
|
.EE
|
|
.SH "SEE ALSO"
|
|
.IR dial (2),
|
|
.IR ip (2),
|
|
.IR bridge (3),
|
|
.\" .IR ike (4),
|
|
.IR ndb (6),
|
|
.IR listen (8)
|
|
.br
|
|
.PD 0
|
|
.TF "\fL/lib/rfc/rfc2822"
|
|
.TP
|
|
.B /lib/rfc/rfc2460
|
|
IPv6
|
|
.TP
|
|
.B /lib/rfc/rfc4291
|
|
IPv6 address architecture
|
|
.TP
|
|
.B /lib/rfc/rfc4443
|
|
ICMPv6
|
|
.SH SOURCE
|
|
.B /sys/src/9/ip
|
|
.SH BUGS
|
|
.I Ipmux
|
|
has not been heavily used and should be considered experimental.
|
|
It may disappear in favor of a more traditional packet filter in the future.
|