Mark a session defunct if an attempt to send a message on it fails ou…

…tright. (#26778)

This is most likely a "No route to host" error or something like that, which
_may_ get cleared up with a new dns-sd resolve and session re-establishment.

src/messaging/ExchangeContext.cpp

@@ -203,6 +203,7 @@ CHIP_ERROR ExchangeContext::SendMessage(Protocols::Id protocolId, uint8_t msgTyp
  return CHIP_ERROR_MISSING_SECURE_SESSION;
  }
 
+ SessionHandle session = GetSessionHandle();
  CHIP_ERROR err;
 
 #if CONFIG_BUILD_FOR_HOST_UNIT_TEST
@@ -213,17 +214,29 @@ CHIP_ERROR ExchangeContext::SendMessage(Protocols::Id protocolId, uint8_t msgTyp
  else
  {
 #endif
- err = mDispatch.SendMessage(GetExchangeMgr()->GetSessionManager(), mSession.Get().Value(), mExchangeId, IsInitiator(),
+ err = mDispatch.SendMessage(GetExchangeMgr()->GetSessionManager(), session, mExchangeId, IsInitiator(),
  GetReliableMessageContext(), reliableTransmissionRequested, protocolId, msgType,
  std::move(msgBuf));
 #if CONFIG_BUILD_FOR_HOST_UNIT_TEST
  }
 #endif
- // We should only cancel the response timer if the ExchangeContext fails to send the message that starts the response timer.
- if (err != CHIP_NO_ERROR && startedResponseTimer)
+ if (err != CHIP_NO_ERROR)
  {
- CancelResponseTimer();
- SetResponseExpected(false);
+ // We should only cancel the response timer if the ExchangeContext fails to send the message that starts the response
+ // timer.
+ if (startedResponseTimer)
+ {
+ CancelResponseTimer();
+ SetResponseExpected(false);
+ }
+
+ // If we can't even send a message (send failed with a non-transient
+ // error), mark the session as defunct, just like we would if we
+ // thought we sent the message and never got a response.
+ if (session->IsSecureSession() && session->AsSecureSession()->IsCASESession())
+ {
+ session->AsSecureSession()->MarkAsDefunct();
+ }
  }
 
  // Standalone acks are not application-level message sends.