fix: add SNI servername for TLS connection from host field

lib/connectors/StandaloneConnector.ts

@@ -1,4 +1,4 @@
-import { createConnection, IpcNetConnectOpts, TcpNetConnectOpts } from "net";
+import { createConnection, IpcNetConnectOpts, TcpNetConnectOpts, isIP } from "net";
 import { connect as createTLSConnection, ConnectionOptions } from "tls";
 import { NetStream } from "../types";
 import { CONNECTION_CLOSED_ERROR_MSG } from "../utils";
@@ -41,6 +41,12 @@ export default class StandaloneConnector extends AbstractConnector {
 
     if (options.tls) {
       Object.assign(connectionOptions, options.tls);
+      if ("host" in connectionOptions && !("servername" in connectionOptions)) {
+        const host = (connectionOptions as TcpOptions).host;
+        if (host && !isIP(host)) {
+          (connectionOptions as any).servername = host;
+        }
+      }
     }
 
     // TODO:

test/unit/connectors/connector.ts

@@ -44,5 +44,40 @@ describe("StandaloneConnector", () => {
       });
       connector.disconnect();
     });
+
+    it("uses host as tls servername when not explicitly provided", async () => {
+      const spy = sinon.spy(tls, "connect");
+      const connector = new StandaloneConnector({
+        host: "cache.internal",
+        port: 6379,
+        tls: { rejectUnauthorized: false },
+      });
+      await connector.connect(() => {});
+      expect(spy.calledOnce).to.eql(true);
+      expect(spy.firstCall.args[0]).to.eql({
+        host: "cache.internal",
+        port: 6379,
+        rejectUnauthorized: false,
+        servername: "cache.internal",
+      });
+      connector.disconnect();
+    });
+
+    it("does not set tls servername from host when host is an IP", async () => {
+      const spy = sinon.spy(tls, "connect");
+      const connector = new StandaloneConnector({
+        host: "127.0.0.1",
+        port: 6379,
+        tls: { rejectUnauthorized: false },
+      });
+      await connector.connect(() => {});
+      expect(spy.calledOnce).to.eql(true);
+      expect(spy.firstCall.args[0]).to.eql({
+        host: "127.0.0.1",
+        port: 6379,
+        rejectUnauthorized: false,
+      });
+      connector.disconnect();
+    });
   });
 });