Allow setting up an auto-resubscribe ReadClient with just a peer id.

This delegates all the work of setting up the CASE session, and the attendant
retries, to the ReadClient.

Fixes project-chip#23983

src/app/ReadClient.cpp

@@ -940,6 +940,19 @@ CHIP_ERROR ReadClient::SendAutoResubscribeRequest(ReadPrepareParams && aReadPrep
  return err;
 }
 
+CHIP_ERROR ReadClient::SendAutoResubscribeRequest(const ScopedNodeId & aPublisherId, ReadPrepareParams && aReadPrepareParams)
+{
+ mPeer = aPublisherId;
+ mReadPrepareParams = std::move(aReadPrepareParams);
+ CHIP_ERROR err = EstablishSessionToPeer();
+ if (err != CHIP_NO_ERROR)
+ {
+ // Make sure we call our callback's OnDeallocatePaths.
+ StopResubscription();
+ }
+ return err;
+}
+
 CHIP_ERROR ReadClient::SendSubscribeRequest(const ReadPrepareParams & aReadPrepareParams)
 {
  VerifyOrReturnError(aReadPrepareParams.mMinIntervalFloorSeconds <= aReadPrepareParams.mMaxIntervalCeilingSeconds,
@@ -1118,12 +1131,8 @@ void ReadClient::OnResubscribeTimerCallback(System::Layer * /* If this starts be
  {
  // We don't have an active CASE session. We need to go ahead and set
  // one up, if we can.
- ChipLogProgress(DataManagement, "Trying to establish a CASE session");
- auto * caseSessionManager = InteractionModelEngine::GetInstance()->GetCASESessionManager();
- if (caseSessionManager)
+ if (_this->EstablishSessionToPeer() == CHIP_NO_ERROR)
  {
- caseSessionManager->FindOrEstablishSession(_this->mPeer, &_this->mOnConnectedCallback,
- &_this->mOnConnectionFailureCallback);
  return;
  }
 
@@ -1209,5 +1218,14 @@ Optional<System::Clock::Timeout> ReadClient::GetSubscriptionTimeout()
  return MakeOptional(timeout);
 }
 
+CHIP_ERROR ReadClient::EstablishSessionToPeer()
+{
+ ChipLogProgress(DataManagement, "Trying to establish a CASE session for subscription");
+ auto * caseSessionManager = InteractionModelEngine::GetInstance()->GetCASESessionManager();
+ VerifyOrReturnError(caseSessionManager != nullptr, CHIP_ERROR_INCORRECT_STATE);
+ caseSessionManager->FindOrEstablishSession(mPeer, &mOnConnectedCallback, &mOnConnectionFailureCallback);
+ return CHIP_NO_ERROR;
+}
+
 } // namespace app
 } // namespace chip

src/app/ReadClient.h

@@ -352,12 +352,23 @@ class ReadClient : public Messaging::ExchangeDelegate
  * OnDeallocatePaths. Note: At a given time in the system, you can either have a single subscription with re-sub enabled that
  * has mKeepSubscriptions = false, OR, multiple subs with re-sub enabled with mKeepSubscriptions = true. You shall not
  * have a mix of both simultaneously. If SendAutoResubscribeRequest is called at all, it guarantees that it will call
- * OnDeallocatePaths when OnDone is called. SendAutoResubscribeRequest is the only case that calls OnDeallocatePaths, since
- * that's the only case when the consumer moved a ReadParams into the client.
+ * OnDeallocatePaths (either befor returning error, or when OnDone is called). SendAutoResubscribeRequest is the only case
+ * that calls OnDeallocatePaths, since that's the only case when the consumer moved a ReadParams into the client.
  *
  */
  CHIP_ERROR SendAutoResubscribeRequest(ReadPrepareParams && aReadPrepareParams);
 
+ /**
+ * Like SendAutoResubscribeRequest above, but without a session being
+ * available in the ReadPrepareParams. When this is used, the ReadClient is
+ * responsible for setting up the CASE session itself.
+ *
+ * When using this version of SendAutoResubscribeRequest, the
+ * ReadPrepareParams should have a reference to a session, and if it does
+ * have one that session will be ignored.
+ */
+ CHIP_ERROR SendAutoResubscribeRequest(const ScopedNodeId & aPublisherId, ReadPrepareParams && aReadPrepareParams);
+
  /**
  * This provides a standard re-subscription policy implementation that given a termination cause, does the following:
  * - Calculates the time till next subscription with fibonacci back-off (implemented by ComputeTimeTillNextSubscription()).
@@ -538,6 +549,13 @@ class ReadClient : public Messaging::ExchangeDelegate
 
  CHIP_ERROR GetMinEventNumber(const ReadPrepareParams & aReadPrepareParams, Optional<EventNumber> & aEventMin);
 
+ /**
+ * Start setting up a CASE session to our peer, if we can locate a
+ * CASESessionManager. Returns error if we did not even manage to kick off
+ * a CASE attempt.
+ */
+ CHIP_ERROR EstablishSessionToPeer();
+
  Messaging::ExchangeManager * mpExchangeMgr = nullptr;
  Messaging::ExchangeHolder mExchange;
  Callback & mpCallback;