Support retrieving the initial destination CID from GetParam

docs/Settings.md

@@ -168,7 +168,7 @@ These parameters are accessed by calling [GetParam](./api/GetParam.md) or [SetPa
 | `QUIC_PARAM_CONN_CIBIR_ID`<br> 21                 | uint8_t[]                     | Set-only  | The CIBIR well-known identifier.                                                          |
 | `QUIC_PARAM_CONN_STATISTICS_V2`<br> 22            | QUIC_STATISTICS_V2            | Get-only  | Connection-level statistics, version 2.                                                   |
 | `QUIC_PARAM_CONN_STATISTICS_V2_PLAT`<br> 23       | QUIC_STATISTICS_V2            | Get-only  | Connection-level statistics with platform-specific time format, version 2.                |
-
+| `QUIC_PARAM_CONN_ORIG_DEST_CID` <br> 24           | uint8_t[]                     | Get-only  | CID information about the original client that made the connection to the server.         |
 ### QUIC_PARAM_CONN_STATISTICS_V2
 
 Querying the `QUIC_STATISTICS_V2` struct via `QUIC_PARAM_CONN_STATISTICS_V2` or `QUIC_PARAM_CONN_STATISTICS_V2_PLAT` should be aware of possible changes in the size of the struct, depending on the version of MsQuic the app using at runtime, not just what it was compiled against.

src/core/connection.c

@@ -7170,6 +7170,31 @@ QuicConnParamGet(
         break;
     }
 
+    case QUIC_PARAM_CONN_ORIG_DEST_CID:
+        if (Connection->OrigDestCID == NULL) {
+            Status = QUIC_STATUS_INVALID_STATE;
+            break;
+        }
+        if (Buffer == NULL) {
+            Status = QUIC_STATUS_INVALID_PARAMETER;
+            break;
+        }
+        if (*BufferLength < Connection->OrigDestCID->Length) {
+            Status = QUIC_STATUS_BUFFER_TOO_SMALL;
+            *BufferLength = Connection->OrigDestCID->Length;
+            break;
+        }
+        CxPlatCopyMemory(
+            Connection->OrigDestCID->Data,
+            Buffer,
+            Connection->OrigDestCID->Length);
+        //
+        // Tell app how much buffer we copied.
+        //
+        *BufferLength = Connection->OrigDestCID->Length;
+        Status = QUIC_STATUS_SUCCESS;
+        break;
+
     default:
         Status = QUIC_STATUS_INVALID_PARAMETER;
         break;

src/inc/msquic.h

@@ -889,6 +889,7 @@ typedef struct QUIC_SCHANNEL_CREDENTIAL_ATTRIBUTE_W {
 #endif
 #define QUIC_PARAM_CONN_STATISTICS_V2                   0x05000016  // QUIC_STATISTICS_V2
 #define QUIC_PARAM_CONN_STATISTICS_V2_PLAT              0x05000017  // QUIC_STATISTICS_V2
+#define QUIC_PARAM_CONN_ORIG_DEST_CID                   0x05000018  // uint8_t[]
 
 //
 // Parameters for TLS.

src/test/lib/ApiTest.cpp

@@ -4227,6 +4227,116 @@ void QuicTest_QUIC_PARAM_CONN_STATISTICS_V2_PLAT(MsQuicRegistration& Registratio
     }
 }
 
+
+void QuicTest_QUIC_PARAM_CONN_ORIG_DEST_CID(MsQuicRegistration& Registration) {
+    //
+    // This is the unit test for checking to see if a server has the correct original dest CID.
+    //
+    TestScopeLogger LogScope0("QUIC_PARAM_CONN_ORIG_DEST_CID");
+    {
+        MsQuicConnection Connection(Registration);
+        TEST_QUIC_SUCCEEDED(Connection.GetInitStatus());
+        MsQuicAlpn Alpn("MsQuicTest");
+        MsQuicConfiguration ClientConfiguration(Registration, Alpn, ClientCertCredConfig);
+        TEST_QUIC_SUCCEEDED(
+        MsQuic->ConnectionStart(
+            Connection.Handle,
+            ClientConfiguration,
+            QUIC_ADDRESS_FAMILY_INET,
+            "localhost",
+            4433));
+        //
+        // 8 bytes is the expected minimum size of the CID.
+        //
+        uint32_t SizeOfBuffer = 8;
+        uint8_t Buffer[8]; 
+        TestScopeLogger LogScope1("GetParam test success case");
+        TEST_QUIC_STATUS(
+            QUIC_STATUS_SUCCESS, 
+            Connection.GetParam(
+                QUIC_PARAM_CONN_ORIG_DEST_CID,
+                &SizeOfBuffer, 
+                Buffer
+            )
+        )
+    }
+    {
+        MsQuicConnection Connection(Registration);
+        TEST_QUIC_SUCCEEDED(Connection.GetInitStatus());
+        MsQuicAlpn Alpn("MsQuicTest");
+        MsQuicConfiguration ClientConfiguration(Registration, Alpn, ClientCertCredConfig);
+        TEST_QUIC_SUCCEEDED(
+        MsQuic->ConnectionStart(
+            Connection.Handle,
+            ClientConfiguration,
+            QUIC_ADDRESS_FAMILY_INET,
+            "localhost",
+            4433));
+        uint32_t SizeOfBuffer = 8;
+        TestScopeLogger LogScope1("GetParam null buffer check");
+        TEST_QUIC_STATUS(
+            QUIC_STATUS_INVALID_PARAMETER, 
+            Connection.GetParam(
+                QUIC_PARAM_CONN_ORIG_DEST_CID,
+                &SizeOfBuffer, 
+                nullptr
+            )
+        )
+    }
+    {
+        MsQuicConnection Connection(Registration);
+        TEST_QUIC_SUCCEEDED(Connection.GetInitStatus());
+        MsQuicAlpn Alpn("MsQuicTest");
+        MsQuicConfiguration ClientConfiguration(Registration, Alpn, ClientCertCredConfig);
+        TEST_QUIC_SUCCEEDED(
+        MsQuic->ConnectionStart(
+            Connection.Handle,
+            ClientConfiguration,
+            QUIC_ADDRESS_FAMILY_INET,
+            "localhost",
+            4433));
+        uint32_t SizeOfBuffer = 1;
+        TestScopeLogger LogScope1("GetParam buffer too small check");
+        uint8_t Buffer[1];
+        TEST_QUIC_STATUS(
+            QUIC_STATUS_BUFFER_TOO_SMALL, 
+            Connection.GetParam(
+                QUIC_PARAM_CONN_ORIG_DEST_CID,
+                &SizeOfBuffer, 
+                Buffer
+            )
+        )
+    }
+    {
+        MsQuicConnection Connection(Registration);
+        TEST_QUIC_SUCCEEDED(Connection.GetInitStatus());
+        MsQuicAlpn Alpn("MsQuicTest");
+        MsQuicConfiguration ClientConfiguration(Registration, Alpn, ClientCertCredConfig);
+        TEST_QUIC_SUCCEEDED(
+        MsQuic->ConnectionStart(
+            Connection.Handle,
+            ClientConfiguration,
+            QUIC_ADDRESS_FAMILY_INET,
+            "localhost",
+            4433));
+        uint32_t SizeOfBuffer = 100;
+        uint8_t Buffer[100];
+        TestScopeLogger LogScope1("GetParam size of buffer bigger than needed");
+        TEST_QUIC_STATUS(
+            QUIC_STATUS_SUCCESS, 
+            Connection.GetParam(
+                QUIC_PARAM_CONN_ORIG_DEST_CID,
+                &SizeOfBuffer, 
+                Buffer
+            )
+        )
+        // 
+        // There is no way the CID written should be 100 bytes according to the RFC.
+        //
+        TEST_TRUE(SizeOfBuffer < 100);
+    }
+}
+
 void QuicTestConnectionParam()
 {
     MsQuicAlpn Alpn("MsQuicTest");
@@ -4259,6 +4369,7 @@ void QuicTestConnectionParam()
     QuicTest_QUIC_PARAM_CONN_CIBIR_ID(Registration, ClientConfiguration);
     QuicTest_QUIC_PARAM_CONN_STATISTICS_V2(Registration);
     QuicTest_QUIC_PARAM_CONN_STATISTICS_V2_PLAT(Registration);
+    QuicTest_QUIC_PARAM_CONN_ORIG_DEST_CID(Registration);
 }
 
 //