http: `servername === false` should disable SNI

There is no way to disable SNI extension when sending a request to HTTPS
server. Setting `options.servername` to a falsy value would make Node.js
core override it with either hostname or ip address.

This change introduces a way to disable SNI completely if this is
required for user's application. Setting `options.servername` to ``
in `https.request` would disable overrides and thus disable the
extension.

PR-URL: https://github.com/nodejs/node/pull/27316
Reviewed-By: Steven R Loomis <srloomis@us.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/lib/_http_agent.js b/lib/_http_agent.js
index 32dbf27abc..eb98f2b0bd 100644
--- a/lib/_http_agent.js
+++ b/lib/_http_agent.js
@@ -151,7 +151,7 @@ Agent.prototype.addRequest = function addRequest(req, options, port/* legacy */,
   if (options.socketPath)
     options.path = options.socketPath;
 
-  if (!options.servername)
+  if (!options.servername && options.servername !== '')
     options.servername = calculateServerName(options, req);
 
   const name = this.getName(options);
@@ -198,7 +198,7 @@ Agent.prototype.createSocket = function createSocket(req, options, cb) {
   if (options.socketPath)
     options.path = options.socketPath;
 
-  if (!options.servername)
+  if (!options.servername && options.servername !== '')
     options.servername = calculateServerName(options, req);
 
   const name = this.getName(options);