net: reduce likelihood of race conditions on keep-alive timeout calcu…

…lation between http1.1 servers and clients

reduced likelihood of race conditions on keep-alive timeout calculation between http1.1 servers and clients and honor server keep-alive timeout when agentTimeout is not set

Fixes: nodejs#47130
Fixes: nodejs#52649

lib/_http_agent.js

@@ -488,6 +488,7 @@ Agent.prototype.keepSocketAlive = function keepSocketAlive(socket) {
   socket.unref();
 
   let agentTimeout = this.options.timeout || 0;
+  let canKeepSocketAlive = true;
 
   if (socket._httpMessage?.res) {
     const keepAliveHint = socket._httpMessage.res.headers['keep-alive'];
@@ -496,9 +497,14 @@ Agent.prototype.keepSocketAlive = function keepSocketAlive(socket) {
       const hint = RegExpPrototypeExec(/^timeout=(\d+)/, keepAliveHint)?.[1];
 
       if (hint) {
-        const serverHintTimeout = NumberParseInt(hint) * 1000;
-
-        if (serverHintTimeout < agentTimeout) {
+        // Let the timer expires before the announced timeout to reduce
+        // the likelihood of ECONNRESET errors
+        let serverHintTimeout = (NumberParseInt(hint) * 1000) - 1000;
+        serverHintTimeout = serverHintTimeout > 0 ? serverHintTimeout : 0;
+        if (serverHintTimeout === 0) {
+          // Cannot safely reuse the socket because the server timeout is too short
+          canKeepSocketAlive = false;
+        } else if (!agentTimeout || serverHintTimeout < agentTimeout) {
           agentTimeout = serverHintTimeout;
         }
       }
@@ -509,7 +515,7 @@ Agent.prototype.keepSocketAlive = function keepSocketAlive(socket) {
     socket.setTimeout(agentTimeout);
   }
 
-  return true;
+  return canKeepSocketAlive;
 };
 
 Agent.prototype.reuseSocket = function reuseSocket(socket, req) {