From bebbd68ef6ed53c6a5eba4b21f307cc32260d0bc Mon Sep 17 00:00:00 2001
From: Neal Beeken <neal.beeken@mongodb.com>
Date: Mon, 19 Apr 2021 10:43:26 -0400
Subject: [PATCH] fix(NODE-3176): handle errors from MessageStream (#2780)

---
 src/cmap/connection.ts          | 64 ++++++++++++++++-----------------
 test/unit/sdam/topology.test.js | 28 +++++++++++++++
 2 files changed, 60 insertions(+), 32 deletions(-)

diff --git a/src/cmap/connection.ts b/src/cmap/connection.ts
index 50f3cd099ed..682023a0605 100644
--- a/src/cmap/connection.ts
+++ b/src/cmap/connection.ts
@@ -194,38 +194,9 @@ export class Connection extends EventEmitter {
       /* ignore errors, listen to `close` instead */
     });
 
-    stream.on('close', () => {
-      if (this.closed) {
-        return;
-      }
-
-      this.closed = true;
-      this[kQueue].forEach(op =>
-        op.cb(new MongoNetworkError(`connection ${this.id} to ${this.address} closed`))
-      );
-      this[kQueue].clear();
-
-      this.emit('close');
-    });
-
-    stream.on('timeout', () => {
-      if (this.closed) {
-        return;
-      }
-
-      stream.destroy();
-      this.closed = true;
-      this[kQueue].forEach(op =>
-        op.cb(
-          new MongoNetworkTimeoutError(`connection ${this.id} to ${this.address} timed out`, {
-            beforeHandshake: this[kIsMaster] == null
-          })
-        )
-      );
-
-      this[kQueue].clear();
-      this.emit('close');
-    });
+    this[kMessageStream].on('error', error => this.handleIssue({ destroy: error }));
+    stream.on('close', () => this.handleIssue({ isClose: true }));
+    stream.on('timeout', () => this.handleIssue({ isTimeout: true, destroy: true }));
 
     // hook the message stream up to the passed in stream
     stream.pipe(this[kMessageStream]);
@@ -269,6 +240,35 @@ export class Connection extends EventEmitter {
     this[kLastUseTime] = now();
   }
 
+  handleIssue(issue: { isTimeout?: boolean; isClose?: boolean; destroy?: boolean | Error }): void {
+    if (this.closed) {
+      return;
+    }
+
+    if (issue.destroy) {
+      this[kStream].destroy(typeof issue.destroy === 'boolean' ? undefined : issue.destroy);
+    }
+
+    this.closed = true;
+
+    for (const [, op] of this[kQueue]) {
+      if (issue.isTimeout) {
+        op.cb(
+          new MongoNetworkTimeoutError(`connection ${this.id} to ${this.address} timed out`, {
+            beforeHandshake: !!this[kIsMaster]
+          })
+        );
+      } else if (issue.isClose) {
+        op.cb(new MongoNetworkError(`connection ${this.id} to ${this.address} closed`));
+      } else {
+        op.cb(typeof issue.destroy === 'boolean' ? undefined : issue.destroy);
+      }
+    }
+
+    this[kQueue].clear();
+    this.emit('close');
+  }
+
   destroy(): void;
   destroy(callback: Callback): void;
   destroy(options: DestroyOptions): void;
diff --git a/test/unit/sdam/topology.test.js b/test/unit/sdam/topology.test.js
index 71964ed918a..4669c722060 100644
--- a/test/unit/sdam/topology.test.js
+++ b/test/unit/sdam/topology.test.js
@@ -286,5 +286,33 @@ describe('Topology (unit)', function () {
         });
       });
     });
+
+    it('should encounter a server selection timeout on garbled server responses', function () {
+      const net = require('net');
+      const server = net.createServer();
+      const p = Promise.resolve();
+      server.listen(0, 'localhost', 2, () => {
+        server.on('connection', c => c.on('data', () => c.write('garbage_data')));
+        const { address, port } = server.address();
+        const client = this.configuration.newClient(`mongodb://${address}:${port}`, {
+          serverSelectionTimeoutMS: 1000
+        });
+        p.then(() =>
+          client
+            .connect()
+            .then(() => {
+              expect.fail('Should throw a server selection error!');
+            })
+            .catch(error => {
+              expect(error).to.exist;
+            })
+            .finally(() => {
+              server.close();
+              return client.close();
+            })
+        );
+      });
+      return p;
+    });
   });
 });