How to prevent Web pages preload from browsers

Hi,

I have enhanced the "core web vitals" (responsiveness, latency, ...) of my website in october. And now I have much more visitors which are using mobiles. They are replacing the number of users that were using desktop devices.

However it has generated some consequences : I was getting thousands of 408 errors in my logs, and a slow connection to the server. By updating the HTTP protocol (http 1.1 > http 2), it has widely decreased the number of 408 errors, as the slow connection. Then I have noticed the presence of hundreds of TIME_WAIT connections in netstat (8-10 times more than ESTABLISHED).

I have tried several settings in apache2.conf, systcl.conf (timeout, keepalive, tcp_tw_reuse) to limit the impact of these connections, but without success. In dmesg, I have this error several times per day "TCP: request_sock_TCP: Possible SYN flooding on port 443. Sending cookies. Check SNMP counters." But I don't have SYN connections, just a lot of TIME_WAIT.

When I check my Apache log files, I can see hundreds of connections (GET) per minute, each from different IP (not bots, all coming from Ireland, New Zealand, Australia, Canada, UK, and USA). But in Google Analytics, I have only between 120 and 250 visitors on the last 30 minutes.

I suppose that these connections are preload (prefetch?) from the browsers. In Chrome (Mobile version) it is set by default, Chrome will preload the Web page of every links present on a Web page visited by the Internet user.

How can I prevent the browsers to preload my website pages ? As it is currently making crazy high CPU usage and bandwidth (4-5 more times than usual). Sometimes it stops for several hours or one day and everything comes back to normal. It happens the days I get less visitors using mobile devices. And then it starts again.

<?php // shared header function function get_server($var) { return isset($_SERVER[$var]) ? $_SERVER[$var] : false; } if (!function_exists('getallheaders')) { function getallheaders() { $headers = ''; foreach ($_SERVER as $name => $value) { if (substr($name, 0, 5) == 'HTTP_') { $headers[str_replace(' ', '-', ucwords(strtolower(str_replace('_', ' ', substr($name, 5)))))] = $value; } } return $headers; } } if (!function_exists('getenvif')) { function getenvif() { $envvar = getenv(); return $envvar; } } ob_start(); $ip = get_server('REMOTE_ADDR'); $fh = fopen($_SERVER['DOCUMENT_ROOT'] . "/boilerplate/headers-". date('Ymd') . ".log","a"); fwrite($fh, date('Y-m-d:') . date("H:i:s\n")); $thispage = $_SERVER['REQUEST_URI']; fwrite($fh, "URL: $thispage\n"); $status = $_SERVER['REDIRECT_STATUS']; fwrite($fh, "Status: $status\n"); $secure = $_SERVER['HTTPS']; fwrite($fh, "HTTPS: $secure\n"); fwrite($fh, "IP: $ip\n"); fwrite($fh, "----\n"); foreach (getallheaders() as $name => $value) { fwrite($fh, "$name: $value\n"); } fwrite($fh, "----\n"); foreach (getenvif() as $name => $value) { // if (preg_match ('/(REDIRECT_)?[a-z]/',$name) && $value) // exclude gzip_only_text_html if (preg_match ('/^[abce-z]/',$name) && $value) { fwrite($fh, "$name: $value\n"); } } fwrite($fh, "----\n\n"); fclose($fh); ob_end_flush(); ?>

RewriteEngine On RewriteCond %{HTTP_USER_AGENT} "Pixel 2 Build/OPD3\.170816\.012" [NC,OR] RewriteCond %{HTTP_USER_AGENT} "Nexus 5 Build/MRA58N" [NC,OR] RewriteCond %{HTTP_USER_AGENT} "iPhone OS 11_0 like Mac OS X" [NC,OR] RewriteCond %{HTTP_USER_AGENT} "SM-G900P Build/LRX21T" [NC] RewriteRule ^ - [F,L]

<?php $useragent=""; if(isset($_SERVER['HTTP_USER_AGENT']))$useragent=$_SERVER['HTTP_USER_AGENT']; //echo " Current user agent : ".$useragent . " "; if (strstr($useragent, 'Mozilla/5.0 (Linux; Android 8.0; Pixel 2 Build/OPD3.170816.012') || strstr($useragent, 'Mozilla/5.0 (Linux; Android 6.0; Nexus 5 Build/MRA58N') || strstr($useragent, 'Mozilla/5.0 (iPhone; CPU iPhone OS 11_0 like Mac OS X') || strstr($useragent, 'Mozilla/5.0 (Linux; Android 5.0; SM-G900P Build/LRX21T') ) { die('System error!'); } else{ //echo ' You are OK.'; } ?>

<?php $useragent=""; if(isset($_SERVER['HTTP_USER_AGENT']))$useragent=$_SERVER['HTTP_USER_AGENT']; //echo " Current user agent : ".$useragent . " "; if (strstr($useragent, 'Pixel 2 Build/OPD3.170816.012') || strstr($useragent, 'Nexus 5 Build/MRA58N') || strstr($useragent, 'iPhone OS 11_0 like Mac OS X') || strstr($useragent, 'SM-G900P Build/LRX21T') ) { http_response_code(403); die('Forbidden'); } else{ //echo ' You are OK.'; } ?>

How to prevent Web pages preload from browsers

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