Linux Amateur Radio AX.25 HOWTO Jeff Tranter, VE3ICH tranter@pobox.com v2.1, 19 September 2001 TheLinuxoperatingsystemisperhapstheonlyoperatingsystemintheworldthatcanboast nativeandstandardsupportfortheAX.25packetradioprotocolutilizedbyAmateurRadio operatorsworldwide.Thisdocumentdescribeshowtoinstallandconfigurethissupport. 1. Introduction Amateurradioisanon-profit,non-commercialactivityenjoyedbyhobbyistsworld-wide.Radio amateursarelicensedbygovernmentauthoritiestouseportionsoftheradiospectrumallocatedtothem fornon-commercial,non-profitactivitiesincludingpersonalcommunication,publicservice,and technicalexperimentation.PacketRadioisaparticulardigitalmodeofcommunicationthatmakesuseof networkingprotocolstoprovidecomputertocomputercommunication. ThisdocumentwasoriginallyanappendixtotheHAM-HOWTO,butgrewtoolargetobereasonably managedinthatfashion.ThisdocumentdescribeshowtoinstallandconfigurethenativeAX.25, NET/ROMandROSEsupportforLinux.Afewtypicalconfigurationsaredescribedthatcouldbeused asmodelstoworkfrom. TheLinuximplementationoftheamateurradioprotocolsisveryflexible.Topeoplerelativelyunfamiliar withtheLinuxoperatingsystemtheconfigurationprocessmaylookdauntingandcomplicated.Itwill takeyoualittletimetocometounderstandhowthewholethingfitstogether.Youwillfindconfiguration verydifficultifyouhavenotproperlypreparedyourselfbylearningaboutLinuxingeneral.Youcannot expecttoswitchfromsomeotherenvironmenttoLinuxwithoutlearningaboutLinuxitself. 1.1. Changes from the previous version • UpdatedIPIPtunnellingsectiontoreflectiproute2package(thankstoMilanKalina). 1 LinuxAmateurRadioAX.25HOWTO 1.2. Where to obtain new versions of this document ThebestplacetoobtainthelatestversionofthisdocumentisfromaLinuxDocumentationProject archive.TheLinuxDocumentationProjectrunsawebserverandthisdocumentappearsthereasthe AX25-HOWTO(http://www.linuxdoc.org/HOWTO/AX25-HOWTO.html).Thisdocumentisalso availableinvariousformatsfromtheLinuxDocumentationProject(http://www.linuxdoc.org). Youcanalwayscontactme,butIpassnewversionsofthedocumentdirectlytotheLDPHOWTO coordinator,soifitisn’ttherethenchancesareIhaven’tfinishedit. 1.3. Other related documentation Thereisalotofrelateddocumentation.TherearemanydocumentsthatrelatetoLinuxnetworkingin moregeneralwaysandIstronglyrecommendyoualsoreadtheseastheywillassistyouinyourefforts andprovideyouwithdeeperinsightintootherpossibleconfigurations.Theyare: • LinuxNetworkingHOWTO(http://www.linuxdoc.org/HOWTO/Net-HOWTO/index.html) • LinuxEthernetHOWTO(http://www.linuxdoc.org/HOWTO/Ethernet-HOWTO.html) • LinuxFirewallandProxyServerHOWTO (http://www.linuxdoc.org/HOWTO/Firewall-HOWTO.html) • Linux2.4AdvancedRoutingHOWTO (http://www.linuxdoc.org/HOWTO/Adv-Routing-HOWTO.html) • Netrom-Nodemini-Howto(http://www.linuxdoc.org/HOWTO/mini/Netrom-Node.html) YoumaycomeacrossreferencestoaLinuxHAMHOWTO.Thisdocumentisobsoleteandhasbeen replacedbytheHamsoftLinuxHamRadioApplicationsandUtilitiesDatabase (http://radio.linux.org.au/)website.MoregeneralLinuxinformationmaybefoundbyreferencingother LinuxHOWTO(http://www.linuxdoc.org/HOWTO/HOWTO-INDEX/index.html)documents. 2. The Packet Radio Protocols and Linux TheAX.25protocoloffersbothconnectedandconnectionlessmodesofoperation,andisusedeitherby itselfforpoint-pointlinks,ortocarryotherprotocolssuchasTCP/IPandNET/ROM. ItissimilartoX.25level2instructure,withsomeextensionstomakeitmoreusefulintheamateurradio environment. TheNET/ROMprotocolisanattemptatafullnetworkprotocolandusesAX.25atitslowestlayerasa datalinkprotocol.ItprovidesanetworklayerthatisanadaptedformofAX.25.TheNET/ROMprotocol 2 LinuxAmateurRadioAX.25HOWTO featuresdynamicroutingandnodealiases. TheROSEprotocolwasconceivedandfirstimplementedbyTomMoultonW2VYandisan implementationoftheX.25packetlayerprotocolandisdesignedtooperatewithAX.25asitsdatalink layerprotocol.Ittooprovidesanetworklayer.ROSEaddressestaketheformof10digitnumbers.The firstfourdigitsarecalledtheDataNetworkIdentificationCode(DNIC)andaretakenfromAppendixB oftheCCITTX.121recommendation.MoreinformationontheROSEprotocolmaybeobtainedfrom theRATSWebserver(http://www.rats.org/). AlanCoxdevelopedsomeearlykernelbasedAX.25softwaresupportforLinux.JonathonNaylor (mailto:g4klx@g4klx.demon.co.uk)hastakenupongoingdevelopmentofthecode,hasadded NET/ROMandROSEsupportandisnowthedeveloperoftheAX.25relatedkernelcode.DAMA supportwasdevelopedbyJoerg(mailto:jreuter@poboxes.com),DL1BKE.BaycomandSoundmodem supportwereaddedbyThomasSailer(mailto:sailer@ife.ee.ethz.ch).TheAX.25softwareisnow maintainedbyasmallteamofdevelopersonSourceForge(http://www.sourceforge.net). TheLinuxcodesupportsKISSand6PACKbasedTNC’s(TerminalNodeControllers),theOttawaPI card,theGracilisPacketTwincardandotherZ8530SCCbasedcardswiththegenericSCCdriver, severalparallelandserialportBaycommodems,andserialportYAMmodems.ThomasSailer’skernel soundmodemdriversupportsSoundBlasterandsoundcardsbasedontheCrystalchipset,andhisnewer user-modesoundmodemusesthestandardkernelsounddrivers,soitshouldworkwithanysoundcard supportedunderLinux. TheuserprogramscontainasimplePMS(PersonalMessageSystem),abeaconfacility,alinemode connectprogram,listen(anexampleofhowtocaptureallAX.25framesatrawinterfacelevel),and programstoconfiguretheNET/ROMprotocol.AlsoincludedareanAX.25serverstyleprogramto handleanddispatchincomingAX.25connectionsandaNET/ROMdaemonwhichdoesmostofthehard workforNET/ROMsupport. ThereareutilityprogramstosupportAPRS,includingdigipeatingandgatewayingtotheInternet. 2.1. How it all fits together TheLinuxAX.25implementationisabrandnewimplementation.Whileinmanywaysitmaylooks similartoNOS,orBPQorotherAX.25implementations,itisnoneoftheseandisnotidenticaltoanyof them.TheLinuxAX.25implementationiscapableofbeingconfiguredtobehavealmostidenticallyto otherimplementations,buttheconfigurationprocessisverydifferent. Toassistyouinunderstandinghowyouneedtothinkwhenconfiguringthissectiondescribessomeof thestructuralfeaturesoftheAX.25implementationandhowitfitsintothecontextoftheoverallLinux structure. 3 LinuxAmateurRadioAX.25HOWTO SimplifiedProtocolLayeringDiagram _____________________________________________ | | | | | | AF_AX25 | AF_NETROM | AF_INET | AF_ROSE | |=========|===========|=============|=========| | | | | | | | | TCP/IP | | | | |________ | | | | NET/ROM | | ROSE | | |____________________|____|_________| | AX.25 | |_____________________________________________| ThisdiagramsimplyillustratesthatNET/ROM,ROSEandTCP/IPallrundirectlyontopofAX.25,but thateachoftheseprotocolsistreatedasaseparateprotocolattheprogramminginterface.The‘_’names aresimplythenamesgiventothe‘AddressFamily’ofeachoftheseprotocolswhenwritingprogramsto usethem.Theimportantthingtonotehereistheimplicitdependenceontheconfigurationofyour AX.25devicesbeforeyoucanconfigureyourNET/ROM,ROSEorTCP/IPdevices. SoftwareModuleDiagramofLinuxNetworkImplementation ___________________________________________________________________________ | | | || | | | User | Programs | call node || Daemons | ax25d mheardd | | | | pms mheard || | inetd netromd | |_________|___________|_______________________||__________|_________________| | | Sockets |open(), close(), listen(), read(), write(), connect()| | | |_____________________________________________________| | | | AF_AX25 | AF_NETROM | AF_ROSE | AF_INET | | |___________|_____________|_____________|_____________|___________| |Kernel | Protocols | AX.25 | NetRom | ROSE | IP/TCP/UDP| | |___________|_____________|_____________|_____________|___________| | | Devices | ax0,ax1 | nr0,nr1 | rose0,rose1 | eth0,ppp0 | | |___________|_____________|_____________|_____________|___________| | | Drivers | Kiss PI2 PacketTwin SCC BPQ | slip ppp | | | | Soundmodem Baycom | ethernet | |_________|___________|_________________________________________|___________| |Hardware | PI2 Card, PacketTwin Card, SCC card, Serial port, Ethernet Card | |_________|_________________________________________________________________| Thisdiagramisalittlemoregeneralthanthefirst.Thisdiagramattemptstoshowtherelationship betweenuserapplications,thekernelandthehardware.ItalsoshowstherelationshipbetweentheSocket applicationprogramminginterface,theactualprotocolmodules,thekernelnetworkingdevicesandthe devicedrivers.Anythinginthisdiagramisdependentonanythingunderneathit,andingeneralyoumust configurefromthebottomofthediagramupwards.Soforexample,ifyouwanttorunthecallprogram 4 LinuxAmateurRadioAX.25HOWTO youmustalsoconfigurethehardware,thenensurethatthekernelhastheappropriatedevicedriver,that youcreatetheappropriatenetworkdevice,thatthekernelincludesthedesiredprotocolthatpresentsa programminginterfacethatthecallprogramcanuse.Ihaveattemptedtolayoutthisdocumentin roughlythatorder. 3. The AX.25/NET/ROM/ROSE software components TheAX.25softwareiscomprisedofthreecomponents:thekernelsource,thenetworkconfiguration toolsandtheutilityprograms. AX.25supportintheLinuxkernelhasbeenfairlystablesincethe2.2seriesofkernelversions.This documentassumesyouareusingthemostrecentkernel,whichasthetimeofwritingwas2.4.9. Note:Softwareversionslistedinthisdocumentwerethelatestatthetimeofwriting,butaresubject tochange.Checkfornewerversionswhendownloadingthem. 3.1. Finding the kernel, tools and utility packages 3.1.1. The kernel source Thekernelsourcecanbefoundatwww.kernel.organdftp.kernel.org.Forthe2.4.9kernelit wouldbedownloadedfromftp://ftp.kernel.org/pub/linux/kernel/v2.4/linux-2.4.9.tar.gz. 3.1.2. The network tools ThelatestreleaseofthestandardLinuxnetworktoolssupportAX.25andNET/ROMandcanbefoundat http://www.tazenda.demon.co.uk/phil/net-tools. Thelatestipchainspackagecanbefoundathttp://netfilter.filewatcher.org/ipchains (http://netfilter.filewatcher.org/ipchains/). Note:ItisusuallynotnecessarytodownloadandinstalltheseasanyrecentLinuxdistribution shouldincludethem. 5 LinuxAmateurRadioAX.25HOWTO 3.1.3. The AX.25 utilities Theoldax25-utilsusedwiththe2.0and2.1kernelsisnowobsoleteandhasbeenreplacedwithnew packageshostedonSourceForge(http://sourceforge.net)athttp://sourceforge.net/projects/hams. Thesoftwareisdistributedasthreepackages:theAX.25library,tools,andapplications.Atthetimeof writingthemostrecentversionswerethefollowing: • ftp://hams.sourceforge.net/pub/hams/ax25/libax25-0.0.7.tar.gz • ftp://hams.sourceforge.net/pub/hams/ax25/ax25-tools-0.0.6.tar.gz • ftp://hams.sourceforge.net/pub/hams/ax25/ax25-apps-0.0.4.tar.gz 3.1.4. The APRS utilities IfyouwanttouseAPRSyoucandownloadaprsd(http://sourceforge.net/projects/aprsd/)andaprsdigi (http://www.users.cloud9.net/~alan/ham/aprs/): • http://prdownloads.sourceforge.net/aprsd/aprsd-2.1.4.tar.gz • http://www.users.cloud9.net/~alan/ham/aprs/aprsdigi-2.0-pre3.tar.gz 4. Installing the AX.25/NET/ROM/ROSE software TosuccessfullyinstallAX.25supportonyourLinuxsystemyoumustconfigureandinstallan appropriatekernelandtheninstalltheAX.25utilities. Tip:Ratherthanbuildingandinstallingfromsource,youmayprefertoinstallprebuiltbinary packagesforyoursystem.DebianandRPMformatpackagesareavailableonvariousarchivesites includinghttp://www.debian.organdhttp://rpmfind.net;lookfor"ax25".Incidently,theDebianLinux distributionisconsideredbymanypeopletobeoneofthemore"AmateurRadiofriendly" distributions,andprovidesmanyamateurradioapplicationsasDebianpackages(oneofthe foundersoftheprojectisaham). 4.1. Compiling the kernel IfyouarealreadyfamiliarwiththeprocessofcompilingtheLinuxkernelthenyoucanskipthissection, justbesuretoselecttheappropriateoptionswhencompilingthekernel.Ifyouarenot,thenreadon.You 6 LinuxAmateurRadioAX.25HOWTO mayalsowanttoreadtheLinuxKernelHOWTO (http://www.linuxdoc.org/HOWTO/Kernel-HOWTO.html). Thenormalplaceforthekernelsourcetobeunpackedtoisthe/usr/srcdirectoryintoasubdirectory calledlinux.Todothisyoushouldbeloggedinasrootandexecuteaseriesofcommandssimilarto thefollowing: # cd /usr/src # mv linux linux.old # tar xzvf linux-2.4.9.tar.gz # cd linux Afteryouhaveunpackedthekernelsource,youneedtoruntheconfigurationscriptandchoosethe optionsthatsuityourhardwareconfigurationandtheoptionsthatyouwishbuiltintoyourkernel.Youdo thisbyusingthecommand: # make menuconfig IfyouarerunningXyoucangetagraphicalinterfaceusing: # make xconfig Youmightalsotry: # make config I’mgoingtodescribethefullscreenmethod(menuconfig)becauseitiseasiertomovearound,butuse whicheveryouaremostcomfortablewith. Ineithercaseyouwillbeofferedarangeofoptionsatwhichyoumustanswer‘Y’or‘N’.(Noteyoumay alsoanswer‘M’ifyouareusingmodules.ForthesakeofsimplicityIwillassumeyouarenot,please makeappropriatemodificationsifyouare). 7 LinuxAmateurRadioAX.25HOWTO TheoptionsmostrelevanttoanAX.25configurationare: Code maturity level options ---> [*] Prompt for development and/or incomplete code/drivers ... General setup ---> ... [*] Networking support ... Networking options ---> <*> UNIX domain sockets ... [*] TCP/IP networking ... [?] IP: tunneling ... Amateur Radio Support ---> --- Packet Radio protocols [*] Amateur Radio AX.25 Level 2 protocol [?] AX.25 DAMA Slave support [?] Amateur Radio NET/ROM protocol [?] Amateur Radio X.25 PLP (Rose) AX.25 network device drivers ---> Serial port KISS driver Serial port 6PACK driver BPQ Ethernet driver High-speed (DMA) SCC driver for AX.25 Z8530 SCC driver BAYCOM ser12 fullduplex driver for AX.25 BAYCOM ser12 halfduplex driver for AX.25 BAYCOM picpar and par96 driver for AX.25 BAYCOM epp driver for AX.25 Soundcard modem driver [?] soundmodem support for Soundblaster and compatible cards [?] soundmodem support for WSS and Crystal cards [?] soundmodem support for 1200 baud AFSK modulation [?] soundmodem support for 2400 baud AFSK modulation (7.3728MHz crystal) [?] soundmodem support for 2400 baud AFSK modulation (8MHz crystal) [?] soundmodem support for 2666 baud AFSK modulation [?] soundmodem support for 4800 baud HAPN-1 modulation [?] soundmodem support for 4800 baud PSK modulation [?] soundmodem support for 9600 baud FSK G3RUH modulation YAM driver for AX.25 TheoptionsIhaveflaggedwitha‘*’arethosethatyoumustmustanswer‘Y’to.Therestaredependent onwhathardwareyouhaveandwhatotheroptionsyouwanttoinclude.Someoftheseoptionsare describedinmoredetaillateron,soifyoudon’tknowwhatyouwantyet,thenreadaheadandcome backtothissteplater. 8 LinuxAmateurRadioAX.25HOWTO Afteryouhavecompletedthekernelconfigurationyoushouldbeabletocleanlycompileyournew kernel: # make dep # make clean # make zImage Makesureyoumoveyourarch/i386/boot/zImagefilewhereveryouwantitandthenedityour /etc/lilo.conffileandrerunlilotoensurethatyouactuallybootfromit. 4.1.1. A word about kernel modules CompilingdriversasmodulesisusefulifyouonlyuseAX.25occasionallyandwanttobeabletoload andunloadthemondemandtosavesystemresources.However,somepeoplehaveproblemsgettingthe modularizeddriversworkingbecausetheyaremorecomplicatedtoconfigure.Ifyou’vechosento compileanydriversasmodules,thenyou’llalsoneedtorunthecommands: # make modules # make modules_install toinstallyourmodulesintheappropriatelocation. Youwillalsoneedtoaddsomeentriesintoyour/etc/modules.conffiletoensurethatthekerneld programknowshowtolocatethekernelmodules.Youshouldadd/modifythefollowing: alias net-pf-3 ax25 alias net-pf-6 netrom alias net-pf-11 rose alias tty-ldisc-1 slip alias tty-ldisc-3 ppp alias tty-ldisc-5 mkiss alias bc0 baycom alias nr0 netrom alias pi0a pi2 alias pt0a pt alias scc0 optoscc (or one of the other scc drivers) alias sm0 soundmodem alias tunl0 newtunnel alias char-major-4 serial 9 LinuxAmateurRadioAX.25HOWTO alias char-major-5 serial alias char-major-6 lp Tip:OnDebian-basedLinuxsystemstheseentriesshouldgointothefile/etc/modutils/aliases andthenyouneedtorun/sbin/update-mpodules. 4.2. The AX.25 library, tools, and application programs Afteryouhavesuccessfullycompiledandbootedyournewkernelyouneedtocompileandinstallthe ax25library,tools,andapplicationprograms. Tocompileandinstalllibax25youshoulduseaseriesofcommandssimilartothefollowing: # cd /usr/src # tar xzvf libax25-0.0.7.tar.gz # cd libax25-0.0.7 # ./configure --exec_prefix=/usr --sysconfdir=/etc --localstatedir=/var # make # make install Tip:Theargumentstotheconfigurecommandensurethatthefileswillbeinstalledinthe "standard"placesunderthedirectory/usrinsubdirectoriesbin,sbin,etcandman.Ifyousimply runconfigurewithnooptionsitwilldefaulttoputtingallfilesunder/usr/local.Thiscancausethe situationwhereyouhaveconfigurationfilesinboth/usrand/usr/local.Ifyouwanttoensurethat thiscan’thappenyoucanmake/usr/local/etc/ax25asymboliclinkto/etc/ax25atthevery beginningoftheinstallprocessandthenyouwon’thavetoworryaboutit. Ifthisisafirsttimeinstallation,thatisyou’veneverinstalledanyax25codeonyourmachinebefore, youshouldalsousethe: # make installconf commandtoinstallsomesampleconfigurationfilesintothe/etc/ax25/directoryfromwhichtowork. 10

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