Libygsm library

Description
This library provides encoders and decoders for Mobile Radio Interface Layer 3 messages according to ETSI TS 124 007 and ETSI TS 124 008. Messages are decoded to XML format. Encoders also expect XML format for encoding messages.

The following details a proposal for decoded XML messages:


 * a Mobility Management message

 0 0   false normal-location-updating  0  26203</PLMNidentity> <LAC>011b</LAC> </LAI> <MobileStationClassmark> <RFPowerCapability>class4</RFPowerCapability> <RevisionLevel>GSM-phase2</RevisionLevel> <Flags>ES-IND</Flags> </MobileStationClassmark> <MobileIdentity> <TMSI>9b055efc</TMSI> </MobileIdentity> <AdditionalUpdateParameters>CSMT,CSMO</AdditionalUpdateParameters> <DeviceProperties>NAS-low-priority</DeviceProperties> <MSNetworkFeatureSupport>MS-supports-the-extended-periodic-timer-in-this-domain</MSNetworkFeatureSupport> </Message> </MM>


 * a Call Control message

<CC> <TID TIFlag="false">0</TID> 1</NSD> <Message type="Setup"> <BearerCapability1> <ITC>speech</ITC> <TransferMode>circuit-mode</TransferMode> <CodingStandard>GSM</CodingStandard> <RadioChannelRequirement>FR-and-HR-speech-version1-supported/FR-speech-preferred</RadioChannelRequirement> <SpeechVersions>GSM-FR-speech-version3,GSM-FR-speech-version2,GSM-FR-speech-version1,GSM-HR-speech-version3,GSM-HR-speech-version1</SpeechVersions> </BearerCapability1> <CalledPartyBCDNumber nature="unknown" plan="isdn">122</CalledPartyBCDNumber> <SSVersion>SS-protocol-version-3-and-phase2-error-handling-supported</SSVersion> <CCCapabilities> <Flags>DTMF</Flags> <MaxSupportedBearers>1</MaxSupportedBearers> <MaxSpeechBearers>1</MaxSpeechBearers> </CCCapabilities> <StreamIdentifier>17</StreamIdentifier> </Message> </CC>


 * EPS Mobility Management Message

<EPS_MM> <SecurityHeader>integrity-protected</SecurityHeader> <MAC>03522c19</MAC> <SequenceNumber>8</SequenceNumber> <EPS_MM> <SecurityHeader>plain-NAS-message</SecurityHeader> <Message type="AttachRequest"> <EPSAttachType>combined-EPS-IMSI-attach</EPSAttachType> <NASKeySetIdentifier> <TSC>native-security-context-for-KSI_ASME</TSC> <NASKeySetId>0</NASKeySetId> </NASKeySetIdentifier> <EPSMobileIdentity> <GUTI> <PLMNidentity>46089</PLMNidentity> <MMEGroupID>32769</MMEGroupID> <MMECode>1</MMECode> <M_TMSI>0000002b</M_TMSI> </GUTI> </EPSMobileIdentity> <UENetworkCapability>128-EIA2,128-EIA1,EIA0,128-EEA2,128-EEA1,EEA0,UEA1,UEA0,UIA1</UENetworkCapability> <ESMMessageContainer> <EPS_SM> <EPSBearerIdentity>00</EPSBearerIdentity> <PTID>01</PTID> <Message type=\"PDNConnectivityRequest\"> <RequestType>initialRequest</RequestType> <PDNType>IPv4</PDNType> <ESMInformationTransferFlag>security-protected-ESM-information-transfer-required</ESMInformationTransferFlag> <ProtocolConfigurationOptions>8080211001</ProtocolConfigurationOptions> </Message> </EPS_SM> </ESMMessageContainer> <LastVisitedRegisteredTAI> <PLMNidentity>46099</PLMNidentity> <TAC>0001</TAC> </LastVisitedRegisteredTAI> <DRXParameter> <SplitPGCycleCode>10</SplitPGCycleCode> <NonDRXTimer>no-non-DRX-mode</NonDRXTimer> <SplitOnCCCH>false</SplitOnCCCH> <CNSpecificDRXCycleLength>not-specified-by-the-MS</CNSpecificDRXCycleLength> </DRXParameter> <MSNetworkCapability>e5e034</MSNetworkCapability> <TMSIStatus>no-valid-TMSI-available</TMSIStatus> <MobileStationClassmark2> <RFPowerCapability>irrelevant</RFPowerCapability> <RevisionLevel>R99-or-later</RevisionLevel> <SSScreeningIndicator>ellipsis-notation-and-phase2-error-handling</SSScreeningIndicator> <Flags>ES-IND,MT-sms-point-to-point-capability,pseudo-sync-capability,A5/3-support,CMSP-support,LCS-VA-support,CM3-support</Flags> </MobileStationClassmark2> <VoiceDomainPreferenceAndUEsUsageSetting> <UEUsageSetting>voice-centric</UEUsageSetting> <VoiceDomainPreference>CS-voice-preferred</VoiceDomainPreference> </VoiceDomainPreferenceAndUEsUsageSetting> <OldGUTIType>native-GUTI</OldGUTIType> </Message> </EPS_MM> </EPS_MM>

General format for XML would be: <protocol_tag> <header_IE_1/> <header_IE_2/> ...    <message_type_tag> <message_type_IE_1/> <message_type_IE_2/> ...    </message_type_tag> </protocol_tag>

Unknown IEs will be added as: <ie>02510140</ie>

where the value of the ie element will be a octet string dump of the IE, including IEI.

Implementation
Decoders and encoders will be implemented in a dynamic library found in Yate source directory libs/ygsm.

A class RL3Codec will offer coding and decoding functionality for messages:
 * the decoding function will expect as parameters the input buffer, its length and a XMLElement*&. On return, the XMLElement will contain the decoded message. The function will also return 0 if decoding succeeded or a error indication (value different of 0)
 * the encoding function will expect and XMLElement and a DataBlock into which the XMLElement should be encoded. On return, the DataBlock will contain the encoded message. The function will also return 0 if encoding succeeded or a error indication (value different of 0).
 * the codec will also allow setting some decoding options (like dumping the whole RL3 message buffer into the XML).
 * the codec will use IE descriptions to decode/encode the input data into XML/DataBlock
 * the codec will be able to parse unknown IEs.

Documentation
Documentation will be found on this wiki page.