【OpenAirInterface5g】RRC NR解析之RrcSetupComplete

作者柒号华仔个人主页欢迎访问我的主页个人信条星光不问赶路人,岁月不负有心人。个人方向专注于4G/5G领域同时兼顾其他网络协议编解码协议C/Clinux等感兴趣的小伙伴可以关注我一起交流。目录1. RRC SetupComplete介绍1.1 发送目的1.2 传输信道1.3 信令内容抓包2.rrcSetupComplete解析处理流程3. 相关代码3.1 rrcSetupComplete解析3.2 rrcSetupComplete处理1. RRC SetupComplete介绍RRC SetupComplete是终端收到网络侧分配到无线资源的RRC SETUP“消息的应答。UE在应答消息中对分配资源进行了确认并回复了其5G_S_TMSI_Value Part2的内容消息中携带selectedPLMN-Identity、registeredAMF、snssai-list和NASNAS信息为上下文建立和注册请求。基站(gNB)收到后根据其AMF标识,与核心网一同进行认证和注册流程。1.1 发送目的通知网络侧,终端与无线网之间RRC连接建立完成1.2 传输信道承载SRB1;信道DCCH;方向UE-gNB其中的NAS最终会到达5GC1.3 信令内容抓包rrcSetupComplete信令抓包selectedPLMN-IdentityPLMN选择标识指示UE选择的哪个PLMN此处是1表示选择了SIB1中的第一个PLMN如果是2则表示选择了SIB1中第二个PLMNregisteredAMF注册的AMF标识guami-Typeguami类型S-NSSAI切片类型Security protected NAS 5GS message已经进行加密和完整性保护的NAS消息到达核心网AMF进行解码后可以看到详细内容2.rrcSetupComplete解析处理流程nr_rrc_gNB_decode_dcch()解码rrcSetupComplete流程如下对于主函数传过来的buffer调用uper_decode()进行per解码获得消息ID为rrcSetupComplete。根据rnti查找UE上下文rrc_gNB_get_ue_context()如果无法找到上下文说明该rnti未进行接入直接break跳出正常情况能够找到UE上下文。对ng_5G_S_TMSI_Value类型进行判断分两种情况ng_5G_S_TMSI 此处是完整的5g_s_tmsi长度为48bit。ng_5G_S_TMSI_Part2 在Rrc setup Request中存在是5G_S_TMSI_Part1长度为39bit。此处Part2为5g_s_tmsi后9bit两者合起来为48bit。根据收到的TMSI更新UE上下文进入rrc_gNB_process_RRCSetupComplete()函数对解析后的rrcSetupComplete进行处理由于SRB1已经建立因此将上下文中SRB1的Active设为1Srb_id设为1StatusRrcRRC状态设为NR_RRC_CONNECTED调用rrc_gNB_send_NGAP_NAS_FIRST_REQ()函数向NGAP模块发送初始NAS消息该NAS信息通常为Register Request或Service Request即UE开始向5GC进行注册。3. 相关代码3.1 rrcSetupComplete解析switch(ul_dcch_msg-message.choice.c1-present){caseNR_UL_DCCH_MessageType__c1_PR_rrcSetupComplete:if(!ue_context_p){LOG_I(NR_RRC,Processing NR_RRCSetupComplete UE %x, ue_context_p is NULL\n,ctxt_pP-rnti);break;}LOG_DUMPMSG(NR_RRC,DEBUG_RRC,(char*)Rx_sdu,sdu_sizeP,[MSG] RRC SetupComplete\n);MSC_LOG_RX_MESSAGE(MSC_RRC_GNB,MSC_RRC_UE,Rx_sdu,sdu_sizeP,MSC_AS_TIME_FMT NR_RRCSetupComplete UE %x size %u,MSC_AS_TIME_ARGS(ctxt_pP),ue_context_p-ue_context.rnti,sdu_sizeP);LOG_D(NR_RRC,PROTOCOL_NR_RRC_CTXT_UE_FMT RLC RB %02d --- RLC_DATA_IND %d bytes (RRCSetupComplete) --- RRC_gNB\n,PROTOCOL_NR_RRC_CTXT_UE_ARGS(ctxt_pP),DCCH,sdu_sizeP);if(ul_dcch_msg-message.choice.c1-choice.rrcSetupComplete-criticalExtensions.presentNR_RRCSetupComplete__criticalExtensions_PR_rrcSetupComplete){if(ul_dcch_msg-message.choice.c1-choice.rrcSetupComplete-criticalExtensions.choice.rrcSetupComplete-ng_5G_S_TMSI_Value!NULL){if(ul_dcch_msg-message.choice.c1-choice.rrcSetupComplete-criticalExtensions.choice.rrcSetupComplete-ng_5G_S_TMSI_Value-presentNR_RRCSetupComplete_IEs__ng_5G_S_TMSI_Value_PR_ng_5G_S_TMSI_Part2){// ng-5G-S-TMSI-Part2 BIT STRING (SIZE (9))if(ul_dcch_msg-message.choice.c1-choice.rrcSetupComplete-criticalExtensions.choice.rrcSetupComplete-ng_5G_S_TMSI_Value-choice.ng_5G_S_TMSI_Part2.size!2){LOG_E(NR_RRC,wrong ng_5G_S_TMSI_Part2 size, expected 2, provided %lu,(longunsignedint)ul_dcch_msg-message.choice.c1-choice.rrcSetupComplete-criticalExtensions.choice.rrcSetupComplete-ng_5G_S_TMSI_Value-choice.ng_5G_S_TMSI_Part2.size);return-1;}if(ue_context_p-ue_context.ng_5G_S_TMSI_Part1!0){ue_context_p-ue_context.ng_5G_S_TMSI_Part2BIT_STRING_to_uint16(ul_dcch_msg-message.choice.c1-choice.rrcSetupComplete-criticalExtensions.choice.rrcSetupComplete-ng_5G_S_TMSI_Value-choice.ng_5G_S_TMSI_Part2);}/* TODO */}elseif(ul_dcch_msg-message.choice.c1-choice.rrcSetupComplete-criticalExtensions.choice.rrcSetupComplete-ng_5G_S_TMSI_Value-presentNR_RRCSetupComplete_IEs__ng_5G_S_TMSI_Value_PR_ng_5G_S_TMSI){// NG-5G-S-TMSI :: BIT STRING (SIZE (48))if(ul_dcch_msg-message.choice.c1-choice.rrcSetupComplete-criticalExtensions.choice.rrcSetupComplete-ng_5G_S_TMSI_Value-choice.ng_5G_S_TMSI.size!6){LOG_E(NR_RRC,wrong ng_5G_S_TMSI size, expected 6, provided %lu,(longunsignedint)ul_dcch_msg-message.choice.c1-choice.rrcSetupComplete-criticalExtensions.choice.rrcSetupComplete-ng_5G_S_TMSI_Value-choice.ng_5G_S_TMSI.size);return-1;}uint64_tfiveg_s_TMSIbitStr_to_uint64(ul_dcch_msg-message.choice.c1-choice.rrcSetupComplete-criticalExtensions.choice.rrcSetupComplete-ng_5G_S_TMSI_Value-choice.ng_5G_S_TMSI);LOG_I(NR_RRC,Received rrcSetupComplete, 5g_s_TMSI: 0x%lX, amf_set_id: 0x%lX(%ld), amf_pointer: 0x%lX(%ld), 5g TMSI: 0x%X \n,fiveg_s_TMSI,fiveg_s_TMSI38,fiveg_s_TMSI38,(fiveg_s_TMSI32)0x3F,(fiveg_s_TMSI32)0x3F,(uint32_t)fiveg_s_TMSI);if(ue_context_p-ue_context.Initialue_identity_5g_s_TMSI.presenceTRUE){ue_context_p-ue_context.Initialue_identity_5g_s_TMSI.amf_set_idfiveg_s_TMSI38;ue_context_p-ue_context.Initialue_identity_5g_s_TMSI.amf_pointer(fiveg_s_TMSI32)0x3F;ue_context_p-ue_context.Initialue_identity_5g_s_TMSI.fiveg_tmsi(uint32_t)fiveg_s_TMSI;}}}rrc_gNB_process_RRCSetupComplete(ctxt_pP,ue_context_p,ul_dcch_msg-message.choice.c1-choice.rrcSetupComplete-criticalExtensions.choice.rrcSetupComplete);LOG_I(NR_RRC,PROTOCOL_NR_RRC_CTXT_UE_FMT UE State NR_RRC_CONNECTED \n,PROTOCOL_NR_RRC_CTXT_UE_ARGS(ctxt_pP));}ue_context_p-ue_context.ue_release_timer0;break;3.2 rrcSetupComplete处理voidrrc_gNB_process_RRCSetupComplete(constprotocol_ctxt_t*constctxt_pP,rrc_gNB_ue_context_t*ue_context_pP,NR_RRCSetupComplete_IEs_t*rrcSetupComplete){LOG_I(NR_RRC,PROTOCOL_NR_RRC_CTXT_UE_FMT [RAPROC] Logical Channel UL-DCCH, processing NR_RRCSetupComplete from UE (SRB1 Active)\n,PROTOCOL_NR_RRC_CTXT_UE_ARGS(ctxt_pP));ue_context_pP-ue_context.Srb1.Active1;ue_context_pP-ue_context.Srb1.Srb_info.Srb_id1;ue_context_pP-ue_context.StatusRrcNR_RRC_CONNECTED;if(AMF_MODE_ENABLED){rrc_gNB_send_NGAP_NAS_FIRST_REQ(ctxt_pP,ue_context_pP,rrcSetupComplete);}else{rrc_gNB_generate_SecurityModeCommand(ctxt_pP,ue_context_pP);}}