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diff --git a/share/FAQ/Text/slip_server.FAQ b/share/FAQ/Text/slip_server.FAQ new file mode 100644 index 0000000..99b50a2 --- /dev/null +++ b/share/FAQ/Text/slip_server.FAQ @@ -0,0 +1,433 @@ + Slip Server + FAQ + For + FreeBSD + +$Id: slip_server.FAQ,v 1.2 1994/12/16 04:01:16 gclarkii Exp $ + +Help for setting up SLIP Server services on a FreeBSD system +------------------------------------------------------------ + +Written by Guy Helmer (ghelmer@alpha.dsu.edu) +Last Updated December 13, 1994 + +This document provides suggestions for setting up SLIP Server services +on a FreeBSD system, which typically means configuring your system to +automatically startup connections upon login for remote SLIP clients. +I've written this document based on my own experience; however, as +your system and needs may be different, this document may not answer +all of your questions, and I cannot be responsible if you damage your +system or lose data due to attempting to follow the suggestions here. + +I have only setup SLIP Server services on a FreeBSD 1.1 system, so if +you are running a different version (such as FreeBSD 2.0), your system +may be different. I've decided to write this document since I've +recently been asked for the umpteenth time how to setup a FreeBSD +machine as a SLIP server :-) + + +1. Prerequisites +---------------- + +This document is very technical in nature, so background knowledge is +required. I must assume that you are familiar with the TCP/IP network +protocol, and in particular, network and node addressing, network +address masks, subnetting, routing, and routing protocols, such as +RIP. Configuring SLIP services on a dial-up server requires a +knowledge of these concepts, and if you are not familiar with them, +please read a copy of either Craig Hunt's "TCP/IP Network +Administration" published by O'Reilly & Associates, Inc. (ISBN Number +0-937175-82-X), or Douglas Comer's book on the TCP/IP protocol. + +I will assume that you have already setup your modem(s) and configured +the appropriate system files to allow logins through your modems (see +the manual pages for sio(4) for information on the serial port device +driver and ttys(5), gettytab(5), getty(8), & init(8) for information +relevant to configuring the system to accept logins on modems, and +perhaps stty(1) for information on setting serial port parameters +[such as "clocal" for directly-connected serial interfaces]). + +2. Quick Overview +----------------- + +In its typical configuration, using FreeBSD as a SLIP server works as +follows: a SLIP user dials up your FreeBSD SLIP Server system and logs +in with a special SLIP login ID that uses "/usr/sbin/sliplogin" as the +special user's shell. The "sliplogin" program browses the file +"/etc/slip.hosts" to find a matching line for the special user, and if +it finds a match, connects the serial line to an available SLIP +interface and then runs /etc/slip.login to configure the SLIP +interface. + +2.1 An Example of a SLIP Server Login +------------------------------------- + +For example, if my SLIP user ID were "Shelmerg", that user's entry in +/etc/master.passwd would look something like this (except it would be +all on one line): + +Shelmerg:password:1964:89::0:0:Guy Helmer - SLIP: + /usr/users/Shelmerg:/usr/sbin/sliplogin + +and, when I log in with that user ID, "sliplogin" will search +/etc/slip.hosts for a line that had a matching user ID; on my system, +I may have a line in /etc/slip.hosts that reads: + +Shelmerg dc-slip sl-helmer 0xfffffc00 autocomp + +sliplogin will find that matching line, hook the serial line I'm on +into the next available SLIP interface, and then execute +/etc/slip.login like this: + +/etc/slip.login 0 19200 Shelmerg dc-slip sl-helmer 0xfffffc00 autocomp + +If all goes well, /etc/slip.login will issue an "ifconfig" for the +SLIP interface to which sliplogin attached itself (slip interface 0, +in the above example, which was the first parameter in the list given +to slip.login) to set the local IP address (dc-slip), remote IP +address (sl-helmer), network mask for the SLIP interface (0xfffffc00), +and any additional flags (autocomp). If something goes wrong, +sliplogin usually logs good informational messages via the daemon +syslog facility, which usually goes into /var/log/messages (see the +manual pages for syslogd(8) and syslog.conf(5), and perhaps check +/etc/syslog.conf to see to which files syslogd is logging). + +OK, enough of the examples -- let's dive into setting up the system. + +3. Kernel Configuration +----------------------- + +FreeBSD's default kernels usually come with two SLIP interfaces +defined (sl0 and sl1); you can use "netstat -i" to see whether these +interfaces are defined in your kernel. + +Sample output from "netstat -i": +Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Coll +ed0 1500 <Link>0.0.c0.2c.5f.4a 291311 0 174209 0 133 +ed0 1500 138.247.224 ivory 291311 0 174209 0 133 +lo0 65535 <Link> 79 0 79 0 0 +lo0 65535 loop localhost 79 0 79 0 0 +sl0* 296 <Link> 0 0 0 0 0 +sl1* 296 <Link> 0 0 0 0 0 + +The sl0 and sl1 interfaces shown in "netstat -i"'s output indicate +that there are two SLIP interfaces built into the kernel. (The +asterisks after the "sl0" and "sl1" indicate that the interfaces are +"down".) + +However, FreeBSD's default kernels do not come configured to forward +packets (ie, your FreeBSD machine will not act as a router) due to +Internet RFC requirements for Internet hosts (see RFC's 1009 +[Requirements for Internet Gateways], 1122 [Requirements for Internet +Hosts -- Communication Layers], and perhaps 1127 [A Perspective on the +Host Requirements RFCs]), so if you want your FreeBSD SLIP Server to +act as a router, you'll have to add the line "options GATEWAY" to your +machine's kernel configuration file and re-compile the kernel anyway. +(Trivia: "Gateways" are the Internet's old name for what are now +usually called "routers".) + +Please see the BSD System Manager's Manual chapter on "Building +Berkeley Kernels with Config" [the source for which is in +/usr/src/share/doc/smm] and the "FreeBSD Configuration Options" [in +/sys/doc/options.doc] for more information on configuring and building +kernels. You may have to unpack the kernel source distribution if +haven't installed the system sources already (srcdist/srcsys.?? in +FreeBSD 1.1, srcdist/sys.?? in FreeBSD 1.1.5.1, or the entire source +distribution in FreeBSD 2.0-RELEASE) to be able to configure and build +kernels. + +You'll notice that near the end of the default kernel configuration +file (/sys/i386/conf/GENERICAH) is a line that reads: + +pseudo-device sl 2 + +which is the line that defines the number of SLIP devices available in +the kernel; the number at the end of the line is the maximum number of +SLIP connections that may be operating simultaneously. + +See the "Building Berkeley Kernels with Config" and the manual page +for config(8) to see how to configure and build kernels. + +4. Sliplogin Configuration +-------------------------- + +As mentioned earlier, there are three files in the /etc directory that +are part of the configuration for /usr/sbin/sliplogin (see +sliplogin(8) for the actual manual page for sliplogin): slip.hosts, +which lists the SLIP users & their associated IP addresses; +slip.login, which usually just configures the SLIP interface; and +slip.logout, which undoes slip.login's effects when the serial +connection is terminated. + +4.1 slip.hosts Configuration & Local and Remote Address Selection +----------------------------------------------------------------- + +/etc/slip.hosts contains lines which have at least four items listed: +a SLIP user's login ID, the local address (local to the SLIP server) +of the SLIP link, the remote address of the SLIP link, and the network +mask. The local and remote addresses may be host names (given in +/etc/hosts or by the domain name service, depending on your +specifications in /etc/host.conf), and I believe the network mask may +be a name that can be resolved by a lookup into /etc/networks. On one +of my systems, /etc/slip.hosts looks like this: + +----- begin /etc/slip.hosts ----- +# +# login local-addr remote-addr mask opt1 opt2 +# (normal,compress,noicmp) +# +Shelmerg dc-slip sl-helmerg 0xfffffc00 autocomp +----- end /etc/slip.hosts ------ + +At the end of the line is one or more of the options: + + "normal" - no header compression + "compress" - compress headers + "autocomp" - compress headers if the remote end allows it + "noicmp" - disable ICMP packets (so any "ping" packets won't use up + any of your bandwidth) + +Your choice of local and remote addresses for your SLIP links depends +on whether you are going to dedicate a TCP/IP subnet or if you are +going to use "proxy ARP" on your SLIP server (it's not "true" proxy +ARP, but that is the terminology that I will use in this document to +describe it). If you're not sure which method to select or how to +assign IP addresses, please refer to the TCP/IP books referenced in +the "Prerequisites" section and/or consult your IP network manager. + +If you are going to use a separate subnet for your SLIP clients, you +will need to allocate the subnet number out of your assigned IP +network number and assign each of your SLIP client's IP numbers out of +that subnet; then you will probably either need to configure a static +route to the SLIP subnet via your SLIP server on your nearest IP +router, or install "gated" on your FreeBSD SLIP server and configure +it to talk the appropriate routing protocols to your other routers to +inform them about your SLIP server's route to the SLIP subnet. + +Otherwise, if you will use the "proxy ARP" method, you will need to +assign your SLIP client's IP addresses out of your SLIP server's +Ethernet subnet, and you'll also need to adjust your /etc/slip.login +and /etc/slip.logout scripts to use arp(8) to manage the proxy-ARP +entries in the SLIP server's ARP table. + +4.2 slip.login Configuration +---------------------------- + +The typical /etc/slip.login file looks like this: + +----- begin /etc/slip.login ----- +#!/bin/sh - +# +# @(#)slip.login 5.1 (Berkeley) 7/1/90 + +# +# generic login file for a slip line. sliplogin invokes this with +# the parameters: +# 1 2 3 4 5 6 7-n +# slipunit ttyspeed loginname local-addr remote-addr mask opt-args +# +/sbin/ifconfig sl$1 inet $4 $5 netmask $6 +----- end /etc/slip.login ----- + +This slip.login file merely ifconfig's the appropriate SLIP interface +with the local and remote addresses and network mask of the SLIP +interface. + +If you have decided to use the "proxy ARP" method (instead of using a +separate subnet for your SLIP clients), your /etc/slip.login file will +need to look something like this: + +----- begin /etc/slip.login for "proxy ARP" ----- +#!/bin/sh - +# +# @(#)slip.login 5.1 (Berkeley) 7/1/90 + +# +# generic login file for a slip line. sliplogin invokes this with +# the parameters: +# 1 2 3 4 5 6 7-n +# slipunit ttyspeed loginname local-addr remote-addr mask opt-args +# +/sbin/ifconfig sl$1 inet $4 $5 netmask $6 +# Answer ARP requests for the SLIP client with our Ethernet addr +/usr/sbin/arp -s $5 00:11:22:33:44:55 pub +----- end /etc/slip.login for "proxy ARP" ----- + +The additional line in this slip.login, "arp -s...", creates an ARP +entry in the SLIP server's ARP table which asks the system to give out +the SLIP server's Ethernet MAC address whenever a another system or +router on the Ethernet asks to speak to the SLIP client's IP address. + +When using the example above, be sure to replace the Ethernet MAC +address (00:11:22:33:44:55) with the MAC address of your system's +Ethernet card, or your "proxy ARP" will definitely not work! You can +discover your SLIP server's Ethernet MAC address by looking at the +results of running "netstat -i"; the second line of the output should +look something like: + +ed0 1500 <Link>0.2.c1.28.5f.4a 191923 0 129457 0 116 + ^^^^^^^^^^^^^^^ + +which indicates that this particular system's Ethernet MAC address is +"00:02:c1:28:5f:4a" -- the periods in the Ethernet MAC address given +by "netstat -i" must be changed to colons and leading zeros should be +added to each single-digit hexadecimal number to convert the address +into the form that arp(8) desires; see the manual page on arp(8) for +complete information on usage. + +Note that when you create /etc/slip.login and /etc/slip.logout, the +"execute" bit ("chmod 755 /etc/slip.login /etc/slip.logout") must be +set, or sliplogin will be unable to execute it. + +4.3 slip.logout Configuration +----------------------------- + +"/etc/slip.logout" isn't strictly needed, but if you decide to create +it, this is an example of a basic slip.logout script: + +----- begin /etc/slip.logout ----- +#!/bin/sh - +# +# slip.logout + +# +# logout file for a slip line. sliplogin invokes this with +# the parameters: +# 1 2 3 4 5 6 7-n +# slipunit ttyspeed loginname local-addr remote-addr mask opt-args +# +/sbin/ifconfig sl$1 down +----- end /etc/slip.logout ----- + +If you are using "proxy ARP", you'll want to have /etc/slip.logout +remove the ARP entry for the SLIP client: + +----- begin /etc/slip.logout for "proxy ARP" ----- +#!/bin/sh - +# +# @(#)slip.logout + +# +# logout file for a slip line. sliplogin invokes this with +# the parameters: +# 1 2 3 4 5 6 7-n +# slipunit ttyspeed loginname local-addr remote-addr mask opt-args +# +/sbin/ifconfig sl$1 down +# Quit answering ARP requests for the SLIP client +/usr/sbin/arp -d $5 +----- end /etc/slip.logout for "proxy ARP" ----- + +The "arp -d $5" removes the ARP entry that the "proxy ARP" slip.login +added when the SLIP client logged in. + +It bears repeating: make sure /etc/slip.logout has the execute bit set +for after you create it (e.g., "chmod 755 /etc/slip.logout"). + +5. Routing Considerations +------------------------- + +If you are not using the "proxy ARP" method for routing packets +between your SLIP clients and the rest of your network (and perhaps +the Internet), you will probably either have to add static routes to +your closest default router(s) to route your SLIP client subnet via +your SLIP server, or you will probably need to install and configure +gated on your FreeBSD SLIP server so that it will tell your routers +via appropriate routing protocols about your SLIP subnet. + +5.1 Static Routes +----------------- + +Adding static routes to your nearest default routers can be +troublesome (or impossible, if you don't have authority to do so...). +If you have a multiple-router network in your organization, some +routers, such as Cisco and Proteon, may not only need to be configured +with the static route to the SLIP subnet, but also need to be told +which static routes to tell other routers about, so some expertise and +troubleshooting/tweaking may be necessary to get static-route-based +routing to work... + +5.2 Running gated +----------------- + +An alternative to the headaches of static routes is to install gated +on your FreeBSD SLIP server and configure it to use the appropriate +routing protocols (RIP/OSPF/BGP/EGP) to tell other routers about your +SLIP subnet. gated is available from ftp.gated.cornell.edu in +/pub/gated; I believe the current version as of this writing is +"gated-R3_5Alpha_8.tar.Z", which should include support for FreeBSD +"out-of-the-box". Compile and install it, and then write a +/etc/gated.conf file to configure your gated; here's a sample, similar +to what I use on my FreeBSD SLIP server: + +----- begin sample /etc/gated.conf for gated version 3.5Alpha5 ----- +# +# gated configuration file for dc.dsu.edu; for gated version 3.5alpha5 +# Only broadcast RIP information for xxx.xxx.yy out the ed Ethernet interface +# +# +# tracing options +# +traceoptions "/var/tmp/gated.output" replace size 100k files 2 general ; + +rip yes { + interface sl noripout noripin ; + interface ed ripin ripout version 1 ; + traceoptions route ; +} ; + +# +# Turn on a bunch of tracing info for the interface to the kernel: +kernel { + traceoptions remnants request routes info interface ; +} ; + +# +# Propagate the route to xxx.xxx.yy out the Ethernet interface via RIP +# + +export proto rip interface ed { + proto direct { + xxx.xxx.yy mask 255.255.252.0 metric 1; # SLIP connections + } ; +} ; + +# +# Accept routes from RIP via ed Ethernet interfaces + +import proto rip interface ed { + all ; +} ; + +----- end sample /etc/gated.conf ----- + +The above sample gated.conf file broadcasts routing information +regarding the SLIP subnet "xxx.xxx.yy" via RIP onto the Ethernet; if +you are using a different Ethernet driver than the "ed" driver, you'll +need to change the references to the "ed" interface appropriately. +This sample file also sets up tracing to /var/tmp/gated.output for +debugging gated; you can certainly turn off the tracing options if +gated works OK for you. I've changed my SLIP subnet's address to +"xxx.xxx.yy" throughout the above file; you'll need to change the +"xxx.xxx.yy"'s into the network address of your own SLIP subnet (be +sure to change the net mask in the "proto direct" clause as well). +Complete gated configuration information may be read through the Web +at "http://www.gated.cornell.edu/". + +When you get gated built and installed, and create a configuration +file for it, you'll need to run gated in place of routed on your +FreeBSD system; change the routed/gated startup parameters in +/etc/netstart as appropriate for your system. Please see the manual +page for gated for information on gated's command-line parameters. + +6. Acknowledgements +------------------- + +Thanks to these people for comments and advice regarding this FAQ: + + Wilko Bulte <wilko@yedi.iaf.nl> + Piero Serini <Piero@Strider.Inet.IT> + +<<< END OF SLIP SERVER FAQ >>> + + |
