Improve shutdown performance

Author: yhirose

httplib.h

@@ -8541,25 +8541,33 @@ inline SSL *ssl_new(socket_t sock, SSL_CTX *ctx, std::mutex &ctx_mutex,
   return ssl;
 }
 
-inline void ssl_delete(std::mutex &ctx_mutex, SSL *ssl,
+inline void ssl_delete(std::mutex &ctx_mutex, SSL *ssl, socket_t sock,
                        bool shutdown_gracefully) {
   // sometimes we may want to skip this to try to avoid SIGPIPE if we know
   // the remote has closed the network connection
   // Note that it is not always possible to avoid SIGPIPE, this is merely a
   // best-efforts.
   if (shutdown_gracefully) {
+#ifdef _WIN32
+    SSL_shutdown(ssl);
+#else
     auto is_peer_could_be_closed = false;
     {
+      timeval tv;
+      tv.tv_sec = 1;
+      tv.tv_usec = 0;
+      setsockopt(sock, SOL_SOCKET, SO_RCVTIMEO,
+                 reinterpret_cast<const void *>(&tv), sizeof(tv));
+
       char buf[1];
       if (SSL_peek(ssl, buf, 1) == 0 &&
           SSL_get_error(ssl, 0) == SSL_ERROR_ZERO_RETURN) {
         is_peer_could_be_closed = true;
       }
     }
 
-    if (!is_peer_could_be_closed) {
-      SSL_shutdown(ssl);
-    }
+    if (!is_peer_could_be_closed) { SSL_shutdown(ssl); }
+#endif
   }
 
   std::lock_guard<std::mutex> guard(ctx_mutex);
@@ -8839,7 +8847,7 @@ inline bool SSLServer::process_and_close_socket(socket_t sock) {
     // Shutdown gracefully if the result seemed successful, non-gracefully if
     // the connection appeared to be closed.
     const bool shutdown_gracefully = ret;
-    detail::ssl_delete(ctx_mutex_, ssl, shutdown_gracefully);
+    detail::ssl_delete(ctx_mutex_, ssl, sock, shutdown_gracefully);
   }
 
   detail::shutdown_socket(sock);
@@ -9122,7 +9130,8 @@ inline void SSLClient::shutdown_ssl_impl(Socket &socket,
     return;
   }
   if (socket.ssl) {
-    detail::ssl_delete(ctx_mutex_, socket.ssl, shutdown_gracefully);
+    detail::ssl_delete(ctx_mutex_, socket.ssl, socket.sock,
+                       shutdown_gracefully);
     socket.ssl = nullptr;
   }
   assert(socket.ssl == nullptr);