Network initiated PDU session release impl.

src/ue/sm/procedure.cpp

@@ -41,6 +41,12 @@ void NasSm::abortProcedureByPti(int pti)
     if (pt.state != EPtState::PENDING)
         return;
 
+    if (pt.message == nullptr)
+    {
+        m_logger->err("Procedure abortion failure, stored SM message is null");
+        return;
+    }
+
     auto msgType = pt.message->messageType;
 
     int psi = m_procedureTransactions[pti].psi;

src/ue/sm/release.cpp

@@ -7,9 +7,9 @@
 //
 
 #include "sm.hpp"
-#include <algorithm>
 #include <nas/proto_conf.hpp>
 #include <nas/utils.hpp>
+#include <optional>
 #include <ue/app/task.hpp>
 #include <ue/mm/mm.hpp>
 
@@ -88,4 +88,74 @@ void NasSm::receiveReleaseReject(const nas::PduSessionReleaseReject &msg)
     }
 }
 
-} // namespace nr::ue
\ No newline at end of file
+void NasSm::receiveReleaseCommand(const nas::PduSessionReleaseCommand &msg)
+{
+    m_logger->debug("PDU Session Release Command received");
+
+    int psi = msg.pduSessionId;
+    int pti = msg.pti;
+
+    /* Abnormal case handling 6.3.3.6/a */
+    if (m_pduSessions[msg.pduSessionId]->psState == EPsState::INACTIVE)
+    {
+        m_logger->err("PS[%d] is already in inactive state, ignoring release command", msg.pduSessionId);
+        sendSmCause(nas::ESmCause::INVALID_PDU_SESSION_IDENTITY, msg.pti, msg.pduSessionId);
+        return;
+    }
+
+    /* Abnormal case handling 6.4.1.6/c */
+    if (m_pduSessions[psi]->psState == EPsState::ACTIVE_PENDING)
+    {
+        m_logger->warn("PDU Session Release Command ignored for PSI[%d] due to collision with establishment procedure.",
+                       psi);
+        return;
+    }
+
+    /* Handle reactivation case (take the fields before releasing the PS) */
+    std::optional<SessionConfig> reactivation{};
+    if (msg.smCause.value == nas::ESmCause::REACTIVATION_REQUESTED)
+    {
+        reactivation = SessionConfig{};
+        reactivation->type = m_pduSessions[psi]->sessionType;
+        reactivation->apn = m_pduSessions[psi]->apn;
+        reactivation->sNssai = m_pduSessions[psi]->sNssai;
+    }
+
+    /* Release PS and handle PT */
+    localReleaseSession(psi);
+    if (pti != 0)
+    {
+        auto &pt = m_procedureTransactions[pti];
+
+        if (pt.message == nullptr || pt.message->messageType != nas::EMessageType::PDU_SESSION_RELEASE_REQUEST)
+        {
+            m_logger->err("PTI mismatch occurred, received PTI[%d] has no PDU session release request", pti);
+            sendSmCause(nas::ESmCause::PTI_MISMATCH, msg.pti, msg.pduSessionId);
+            return;
+        }
+
+        // Warning: PS has been released, and the spec says that (6.3.3.3) this PTI should not be released immediately
+        // Therefore the PT does not hold a valid PSI after this point
+        pt.psi = 0;
+
+        // TODO: Let's immediately release the PT for now. See 6.3.3.3
+        freeProcedureTransactionId(pti);
+    }
+
+    /* Construct Release Complete message */
+    nas::PduSessionReleaseComplete resp{};
+    resp.pduSessionId = psi;
+    resp.pti = pti;
+
+    /* Send SM message */
+    sendSmMessage(psi, resp);
+
+    /* Handle reactivation */
+    if (reactivation.has_value())
+    {
+        m_logger->debug("Re-initiating a PDU session establishment procedure due to reactivation request");
+        sendEstablishmentRequest(*reactivation);
+    }
+}
+
+} // namespace nr::ue

src/ue/sm/sm.hpp

@@ -73,7 +73,8 @@ class NasSm
     void receiveEstablishmentRoutingFailure(const nas::PduSessionEstablishmentRequest &msg);
 
     /* Session Release */
-    void receiveReleaseReject(const nas::PduSessionReleaseReject& msg);
+    void receiveReleaseReject(const nas::PduSessionReleaseReject &msg);
+    void receiveReleaseCommand(const nas::PduSessionReleaseCommand &msg);
 
     /* Timer */
     std::unique_ptr<nas::NasTimer> newTransactionTimer(int code);

src/ue/sm/transport.cpp

@@ -56,6 +56,9 @@ void NasSm::receiveSmMessage(const nas::SmMessage &msg)
     case nas::EMessageType::PDU_SESSION_RELEASE_REJECT:
         receiveReleaseReject((const nas::PduSessionReleaseReject &)msg);
         break;
+    case nas::EMessageType::PDU_SESSION_RELEASE_COMMAND:
+        receiveReleaseCommand((const nas::PduSessionReleaseCommand &)msg);
+        break;
     case nas::EMessageType::FIVEG_SM_STATUS:
         receiveSmStatus((const nas::FiveGSmStatus &)msg);
         break;