SERVER-32635 an old mongos server communicating with a fully upgraded cluster should crash

1 files changed, 18 insertions, 0 deletions

diff --git a/src/mongo/rpc/protocol_test.cpp b/src/mongo/rpc/protocol_test.cpp
index 1781d9fab2c..ab92e3eeae1 100644
--- a/src/mongo/rpc/protocol_test.cpp
+++ b/src/mongo/rpc/protocol_test.cpp
@@ -281,4 +281,22 @@ TEST(Protocol, validateWireVersion) {
                           WireVersion::LATEST_WIRE_VERSION - 1);
 }
 
+// A mongos is unable to communicate with a fully upgraded cluster with a higher wire version.
+TEST(Protocol, validateWireVersionFailsForUpgradedServerNode) {
+    // Server is fully upgraded higher than the latest wire version.
+    auto msg =
+        BSON("minWireVersion" << static_cast<int>(WireVersion::FUTURE_WIRE_VERSION_FOR_TESTING)
+                              << "maxWireVersion"
+                              << static_cast<int>(WireVersion::FUTURE_WIRE_VERSION_FOR_TESTING));
+    auto swReply = parseProtocolSetFromIsMasterReply(msg);
+    ASSERT_OK(swReply.getStatus());
+
+    // The client (this mongos server) only has latest wire version.
+    ASSERT_EQUALS(
+        mongo::ErrorCodes::IncompatibleWithUpgradedServer,
+        validateWireVersion({WireVersion::LATEST_WIRE_VERSION, WireVersion::LATEST_WIRE_VERSION},
+                            swReply.getValue().version)
+            .code());
+}
+
 }  // namespace