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33 .ds LH "Installing/Operating \*(4B
38 \*(4B provides support for the standard Internet
39 protocols IP, ICMP, TCP, and UDP. These protocols may be used
40 on top of a variety of hardware devices ranging from
41 serial lines to local area network controllers
42 for the Ethernet. Network services are split between the
43 kernel (communication protocols) and user programs (user
44 services such as TELNET and FTP). This section describes
45 how to configure your system to use the Internet networking support.
46 \*(4B also supports the Xerox Network Systems (NS) protocols.
47 IDP and SPP are implemented in the kernel,
48 and other protocols such as Courier run at the user level.
49 \*(4B provides some support for the ISO OSI protocols CLNP
50 TP4, and ESIS. User level process
51 complete the application protocols such as X.400 and X.500.
52 .Sh 2 "System configuration"
54 To configure the kernel to include the Internet communication
55 protocols, define the INET option.
56 Xerox NS support is enabled with the NS option.
57 ISO OSI support is enabled with the ISO option.
58 In either case, include the pseudo-devices
59 ``pty'', and ``loop'' in your machine's configuration
61 The ``pty'' pseudo-device forces the pseudo terminal device driver
62 to be configured into the system, see
64 while the ``loop'' pseudo-device forces inclusion of the software loopback
66 The loop driver is used in network testing
67 and also by the error logging system.
69 If you are planning to use the Internet network facilities on a 10Mb/s
70 Ethernet, the pseudo-device ``ether'' should also be included
71 in the configuration; this forces inclusion of the Address Resolution
72 Protocol module used in mapping between 48-bit Ethernet
73 and 32-bit Internet addresses.
75 Before configuring the appropriate networking hardware, you should
76 consult the manual pages in section 4 of the Programmer's Manual
77 selecting the appropriate interfaces for your architecture.
79 All network interface drivers including the loopback interface,
80 require that their host address(es) be defined at boot time.
83 commands included in the
86 Interfaces that are able to dynamically deduce the host
87 part of an address may check that the host part of the address is correct.
88 The manual page for each network interface
89 describes the method used to establish a host's address.
91 can also be used to set options for the interface at boot time.
92 Options are set independently for each interface, and
93 apply to all packets sent using that interface.
94 Alternatively, translations for such hosts may be set in advance
95 or ``published'' by a \*(4B host by use of the
98 Note that the use of trailer link-level is now negotiated between \*(4B hosts
100 and it is thus no longer necessary to disable the use of trailers
104 The OSI equivalent to ARP is ESIS (End System to Intermediate System Routing
105 Protocol); running this protocol is mandatory, however one can manually add
106 translations for machines that do not participate by use of the
109 Additional information is provided in the manual page describing
111 .Sh 2 "Local subnets"
113 In \*(4B the Internet support
114 includes the notion of ``subnets''. This is a mechanism
115 by which multiple local networks may appears as a single Internet
116 network to off-site hosts. Subnetworks are useful because
117 they allow a site to hide their local topology, requiring only a single
118 route in external gateways;
119 it also means that local network numbers may be locally administered.
120 The standard describing this change in Internet addressing is RFC-950.
122 To set up local subnets one must first decide how the available
123 address space (the Internet ``host part'' of the 32-bit address)
124 is to be partitioned.
125 Sites with a class A network
126 number have a 24-bit host address space with which to work, sites with a
127 class B network number have a 16-bit host address space, while sites with
128 a class C network number have an 8-bit host address space\**.
130 If you are unfamiliar with the Internet addressing structure, consult
131 ``Address Mappings'', Internet RFC-796, J. Postel; available from
132 the Internet Network Information Center at SRI.
134 To define local subnets you must steal some bits
135 from the local host address space for use in extending the network
136 portion of the Internet address. This reinterpretation of Internet
137 addresses is done only for local networks; i.e. it is not visible
138 to hosts off-site. For example, if your site has a class B network
139 number, hosts on this network have an Internet address that contains
140 the network number, 16 bits, and the host number, another
141 16 bits. To define 254 local subnets, each
142 possessing at most 255 hosts, 8 bits may be taken from the local part.
143 (The use of subnets 0 and all-1's, 255 in this example, is discouraged
144 to avoid confusion about broadcast addresses.)
146 numbers are then constructed by concatenating the original 16-bit network
147 number with the extra 8 bits containing the local subnet number.
149 The existence of local subnets is communicated to the system at the time a
150 network interface is configured with the
154 program. A ``network mask'' is specified to define the
155 portion of the Internet address that is to be considered the network part
157 This mask normally contains the bits corresponding to the standard
158 network part as well as the portion of the local part
159 that has been assigned to subnets.
160 If no mask is specified when the address is set,
161 it will be set according to the class of the network.
162 For example, at Berkeley (class B network 128.32) 8 bits
163 of the local part have been reserved for defining subnets;
166 file contains lines of the form
169 /sbin/ifconfig le0 netmask 0xffffff00 128.32.1.7
171 This specifies that for interface ``le0'', the upper 24 bits of
172 the Internet address should be used in calculating network numbers
173 (netmask 0xffffff00), and the interface's Internet address is
174 ``128.32.1.7'' (host 7 on network 128.32.1). Hosts \fIm\fP on
175 sub-network \fIn\fP of this network would then have addresses of
176 the form ``128.32.\fIn\fP.\fIm\fP''; for example, host
177 99 on network 129 would have an address ``128.32.129.99''.
178 For hosts with multiple interfaces, the network mask should
179 be set for each interface,
180 although in practice only the mask of the first interface on each network
182 .Sh 2 "Internet broadcast addresses"
184 The address defined as the broadcast address for Internet networks
185 according to RFC-919 is the address with a host part of all 1's.
186 The address used by 4.2BSD was the address with a host part of 0.
187 \*(4B uses the standard broadcast address (all 1's) by default,
188 but allows the broadcast address to be set (with
191 This allows networks consisting of both 4.2BSD, \*(Ps and \*(4B hosts
192 to coexist while the upgrade process proceeds.
193 In the presence of subnets, the broadcast address uses the subnet field
194 as for normal host addresses, with the remaining host part set to 1's
195 (or 0's, on a network that has not yet been converted).
196 \*(4B hosts recognize and accept packets
197 sent to the logical-network broadcast address as well as those sent
198 to the subnet broadcast address, and when using an all-1's broadcast,
199 also recognize and receive packets sent to host 0 as a broadcast.
202 If your environment allows access to networks not directly
203 attached to your host you will need to set up routing information
204 to allow packets to be properly routed. Two schemes are
205 supported by the system. The first scheme
206 employs a routing table management daemon.
207 Optimally, you should use the routing daemon
209 available from Cornell university.
210 We use it on our systems and it works well,
211 especially for multi-homed hosts using Serial Line IP (SLIP).
212 Unfortunately, we were not able to obtain permission to
215 If you do not wish to or cannot obtain
217 the distribution does include
219 to maintain the system routing tables. The routing daemon
220 uses a variant of the Xerox Routing Information Protocol
221 to maintain up to date routing tables in a cluster of local
222 area networks. By using the
224 file, the routing daemon can also be used to initialize static routes
225 to distant networks (see the next section for further discussion).
226 When the routing daemon is started up
231 if it exists and installs those routes defined there,
232 then broadcasts on each local network
233 to which the host is attached to find other instances of the routing
234 daemon. If any responses are received, the routing daemons
235 cooperate in maintaining a globally consistent view of routing
236 in the local environment. This view can be extended to include
237 remote sites also running the routing daemon by setting up suitable
242 for a more thorough discussion.
244 The second approach is to define a default or wildcard
246 gateway and depend on the gateway to provide ICMP routing
247 redirect information to dynamically create a routing data
248 base. This is done by adding an entry of the form
251 /sbin/route add default \fIsmart-gateway\fP 1
257 for more information. The default route
258 will be used by the system as a ``last resort''
259 in routing packets to their destination. Assuming the gateway
260 to which packets are directed is able to generate the proper
261 routing redirect messages, the system will then add routing
262 table entries based on the information supplied. This approach
263 has certain advantages over the routing daemon, but is
264 unsuitable in an environment where there are only bridges (i.e.
265 pseudo gateways that, for instance, do not generate routing
266 redirect messages). Further, if the
267 smart gateway goes down there is no alternative, save manual
268 alteration of the routing table entry, to maintaining service.
270 The system always listens, and processes, routing redirect
271 information, so it is possible to combine both of the above
272 facilities. For example, the routing table management process
273 might be used to maintain up to date information about routes
274 to geographically local networks, while employing the wildcard
275 routing techniques for ``distant'' networks. The
277 program may be used to display routing table contents as well
278 as various routing oriented statistics. For example,
280 \fB#\fP \fInetstat \-r\fP
282 will display the contents of the routing tables, while
284 \fB#\fP \fInetstat \-r \-s\fP
286 will show the number of routing table entries dynamically
287 created as a result of routing redirect messages, etc.
288 .Sh 2 "Use of \*(4B machines as gateways"
290 Several changes have been made in \*(4B in the area of gateway support
291 (or packet forwarding, if one prefers).
292 A new configuration option, GATEWAY, is used when configuring
293 a machine to be used as a gateway.
294 This option increases the size of the routing hash tables in the kernel.
295 Unless configured with that option,
296 hosts with only a single non-loopback interface never attempt
297 to forward packets or to respond with ICMP error messages to misdirected
299 This change reduces the problems that may occur when different hosts
300 on a network disagree on the network number or broadcast address.
301 Another change is that \*(4B machines that forward packets back through
302 the same interface on which they arrived
303 will send ICMP redirects to the source host if it is on the same network.
304 This improves the interaction of \*(4B gateways with hosts that configure
305 their routes via default gateways and redirects.
306 The generation of redirects may be disabled with the configuration option
307 IPSENDREDIRECTS=0 or while the system is running by using the command:
310 sysctl -w net.inet.ip.redirect=0
312 in environments where it may cause difficulties.
313 .Sh 2 "Network databases"
315 Several data files are used by the network library routines
316 and server programs. Most of these files are host independent
317 and updated only rarely.
322 File Manual reference Use
324 /etc/hosts \fIhosts\fP\|(5) local host names
325 /etc/networks \fInetworks\fP\|(5) network names
326 /etc/services \fIservices\fP\|(5) list of known services
327 /etc/protocols \fIprotocols\fP\|(5) protocol names
328 /etc/hosts.equiv \fIrshd\fP\|(8) list of ``trusted'' hosts
329 /etc/netstart \fIrc\fP\|(8) command script for initializing network
330 /etc/rc \fIrc\fP\|(8) command script for starting standard servers
331 /etc/rc.local \fIrc\fP\|(8) command script for starting local servers
332 /etc/ftpusers \fIftpd\fP\|(8) list of ``unwelcome'' ftp users
333 /etc/hosts.lpd \fIlpd\fP\|(8) list of hosts allowed to access printers
334 /etc/inetd.conf \fIinetd\fP\|(8) list of servers started by \fIinetd\fP
336 The files distributed are set up for Internet hosts.
337 Local networks and hosts should be added to describe the local
338 configuration; the Berkeley entries may serve as examples
339 (see also the section on
341 Network numbers will have to be chosen for each Ethernet.
342 For sites connected to the Internet,
343 the normal channels should be used for allocation of network
344 numbers (contact hostmaster@SRI-NIC.ARPA).
346 these could be chosen more or less arbitrarily,
347 but it is generally better to request official numbers
348 to avoid conversion if a connection to the Internet (or others on the Internet)
350 .Sh 3 "Network servers"
352 Most network servers are automatically started up at boot time
355 or by the Internet daemon (see below).
356 These include the following:
359 Program Server Started by
361 /usr/sbin/syslogd error logging server \f(CW/etc/rc\fP
362 /usr/sbin/named Internet name server \f(CW/etc/rc\fP
363 /sbin/routed routing table management daemon \f(CW/etc/rc\fP
364 /usr/sbin/rwhod system status daemon \f(CW/etc/rc\fP
365 /usr/sbin/timed time synchronization daemon \f(CW/etc/rc\fP
366 /usr/sbin/sendmail SMTP server \f(CW/etc/rc\fP
367 /usr/libexec/rshd shell server inetd
368 /usr/libexec/rexecd exec server inetd
369 /usr/libexec/rlogind login server inetd
370 /usr/libexec/telnetd TELNET server inetd
371 /usr/libexec/ftpd FTP server inetd
372 /usr/libexec/fingerd Finger server inetd
373 /usr/libexec/tftpd TFTP server inetd
375 Consult the manual pages and accompanying documentation (particularly
376 for named and sendmail) for details about their operation.
382 is controlled by shell
389 is not; they are enabled by setting the variables \fIroutedflags\fP and
391 to strings other than ``NO.''
392 The value of \fIroutedflags\fP provides host-specific options to
405 To have other network servers started as well,
406 commands of the following sort should be placed in the site-dependent file
410 if [ -f /usr/sbin/timed ]; then
411 /usr/sbin/timed & echo -n ' timed' >/dev/console
414 .Sh 3 "Internet daemon"
416 In \*(4B most of the servers for user-visible services are started up by a
417 ``super server'', the Internet daemon. The Internet
419 .Pn /usr/sbin/inetd ,
420 acts as a master server for
421 programs specified in its configuration file,
422 .Pn /etc/inetd.conf ,
423 listening for service requests for these servers, and starting
424 up the appropriate program whenever a request is received.
425 The configuration file contains lines containing a service
428 the type of socket the
429 server expects (e.g. stream or dgram), the protocol to be
430 used with the socket (as found in
431 .Pn /etc/protocols ),
432 whether to wait for each server to complete before starting up another,
433 the user name by which the server should run, the server
434 program's name, and at most five arguments to pass to the
436 Some trivial services are implemented internally in
438 and their servers are listed as ``internal.''
439 For example, an entry for the file
440 transfer protocol server would appear as
443 ftp stream tcp nowait root /usr/libexec/ftpd ftpd
447 for more detail on the format of the configuration file
448 and the operation of the Internet daemon.
449 .Sh 3 "The \f(CW/etc/hosts.equiv\fP file"
451 The remote login and shell servers use an
452 authentication scheme based on trusted hosts. The
454 file contains a list of hosts that are considered trusted
455 and, under a single administrative control. When a user
456 contacts a remote login or shell server requesting service,
457 the client process passes the user's name and the official
458 name of the host on which the client is located. In the simple
459 case, if the host's name is located in
461 and the user has an account on the server's machine, then service
462 is rendered (i.e. the user is allowed to log in, or the command
463 is executed). Users may expand this ``equivalence'' of
464 machines by installing a
466 file in their login directory.
467 The root login is handled specially, bypassing the
469 file, and using only the
473 Thus, to create a class of equivalent machines, the
475 file should contain the \fIofficial\fP names for those machines.
476 If you are running the name server, you may omit the domain part
477 of the host name for machines in your local domain.
478 For example, four machines on our local
479 network are considered trusted, so the
484 vangogh.CS.Berkeley.EDU
485 picasso.CS.Berkeley.EDU
486 okeeffe.CS.Berkeley.EDU
488 .Sh 3 "The \f(CW/etc/ftpusers\fP file"
490 The FTP server included in the system provides support for an
491 anonymous FTP account. Because of the inherent security problems
492 with such a facility you should read this section carefully if
493 you consider providing such a service.
495 An anonymous account is enabled by creating a user
497 When a client uses the anonymous account a
499 system call is performed by the server to restrict the client
500 from moving outside that part of the filesystem where the
501 user ftp home directory is located. Because a
503 call is used, certain programs and files used by the server
504 process must be placed in the ftp home directory.
506 sure that all directories and executable images are unwritable.
507 The following directory setup is recommended. The
514 files are \fBSTRONGLY\fP recommended.
516 \fB#\fP \fIcd ~ftp\fP
517 \fB#\fP \fIchmod 555 .; chown ftp .; chgrp ftp .\fP
518 \fB#\fP \fImkdir bin etc pub\fP
519 \fB#\fP \fIchown root bin etc\fP
520 \fB#\fP \fIchmod 555 bin etc\fP
521 \fB#\fP \fIchown ftp pub\fP
522 \fB#\fP \fIchmod 777 pub\fP
524 \fB#\fP \fIcp /bin/sh /bin/ls .\fP
525 \fB#\fP \fIchmod 111 sh ls\fP
526 \fB#\fP \fIcd ../etc\fP
527 \fB#\fP \fIawk -F: '{$2="*";print$1":"$2":"$3":"$4":"$5":"$6":"}' < /etc/passwd > passwd\fP
528 \fB#\fP \fIawk -F: '{$2="*";print$1":"$2":"}' < /etc/group > group\fP
529 \fB#\fP \fIchmod 444 passwd group\fP
531 When local users wish to place files in the anonymous
532 area, they must be placed in a subdirectory. In the
533 setup here, the directory
537 Aside from the problems of directory modes and such,
538 the ftp server may provide a loophole for interlopers
539 if certain user accounts are allowed.
542 is checked on each connection.
543 If the requested user name is located in the file, the
544 request for service is denied. This file normally has
545 the following names on our systems.
550 Accounts without passwords need not be listed in this file as the ftp
551 server will refuse service to these users.
552 Accounts with nonstandard shells (any not listed in
554 will also be denied access via ftp.