fix(NODE-3176): handle errors from MessageStream (#2774)

If there's a socket that gets a large amount of data written to it our MessageStream will throw an error about exceeding the permitted BSON size, this error is now captured in SDAM.

Author: nbbeeken

lib/cmap/connection.js

@@ -58,38 +58,9 @@ 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]);
@@ -132,6 +103,39 @@ class Connection extends EventEmitter {
     this[kLastUseTime] = now();
   }
 
+  /**
+   * @param {{ isTimeout?: boolean; isClose?: boolean; destroy?: boolean | Error }} issue
+   */
+  handleIssue(issue) {
+    if (this.closed) {
+      return;
+    }
+
+    if (issue.destroy) {
+      this[kStream].destroy(typeof issue.destroy === 'boolean' ? undefined : issue.destroy);
+    }
+
+    this.closed = true;
+
+    for (const idAndOp of this[kQueue]) {
+      const op = idAndOp[1];
+      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(options, callback) {
     if (typeof options === 'function') {
       callback = options;

test/unit/sdam/topology.test.js

@@ -291,5 +291,35 @@ 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 = server.address();
+        const client = this.configuration.newClient(
+          `mongodb://${address.address}:${address.port}`,
+          { serverSelectionTimeoutMS: 1000 }
+        );
+        p.then(() =>
+          client
+            .connect()
+            .then(() => {
+              server.close();
+              client.close();
+              expect.fail('Should throw a server selection error!');
+            })
+            .catch(error => {
+              server.close();
+              const closePromise = client.close();
+              expect(error).to.exist;
+              return closePromise;
+            })
+        );
+      });
+      return p;
+    });
   });
 });