Hi all,
Not sure if I'm hitting a bug here but I could narrow down my observed behaviors to a Squid configuration parameter.
- proxy setup in Transparent mode.
- setting the "Number of squid workers" to 4
- simple CLI request : curl www.perdu.com
Would randomly hit a Squid "id=ERR_INVALID_URL" thrown error message (and would sometimes pass through with no issues):
</head><body id=ERR_INVALID_URL>
<div id="titles">
<h1>ERROR</h1>
<h2>The requested URL could not be retrieved</h2>
</div>
<hr>
<div id="content">
<p>The following error was encountered while trying to retrieve the URL: <a href="/">/</a></p>
<blockquote id="error">
<p><b>Invalid URL</b></p>
</blockquote>
<p>Some aspect of the requested URL is incorrect.</p>
<p>Some possible problems are:</p>
<ul>
<li><p>Missing or incorrect access protocol (should be <q>http://</q> or similar)</p></li>
<li><p>Missing hostname</p></li>
<li><p>Illegal double-escape in the URL-Path</p></li>
<li><p>Illegal character in hostname; underscores are not allowed.</p></li>
</ul>
<p>Your cache administrator is <a href="mailto:admin@localhost.local">admin@localhost.local</a>.</p>
<br>
</div>
<hr>
<div id="footer">
<p>Generated Mon, 02 Mar 2026 06:52:39 GMT by squid.domain.local (squid)</p>
<!-- ERR_INVALID_URL -->
</div>
</body></html>
My guess is that this happens whenever the request is served by any workers other than 0 hence [1,2,3] in my tests.
Reverting to "Number of squid workers = 1" gets me a steady transparent proxy configuration which serve's any requests, all the time.
Any thoughts?
Thanks a lot,
Kind regards,
m.