CLI cURL works flawlessly, Apache with mod_php cannot resolve host, how to fix?

Question

Setup:

• cURL 7.32.0
• Apache 2.2.25
• PHP 5.5.4

Whenever I attempt to:

$ch = curl_init('www.google.com');
curl_exec($ch);

var_dump(curl_error($ch));

within PHP, I get:

Could not resolve host: www.google.com

If I change to curl_init('80.233.168.207') (resolved google.com), the script executes.

Though, running curl www.google.com in CLI, I get a 302 Moved HTML page, due to redirect to localized site (*.lv), but still, that means that cURL executed successfully.

I have seen multiple similar questions (not on SE though), most of them saying that Apache is started either before or concurrently with Network Manager, hence not receiving DNS information. Most of the questions have answers explaining, that the issue can be temporarily resolved/debugged by explicitly stopping, then starting the Apache daemon (instead of restart/graceful-restart).

fsockopen, file_get_contents works flawlessly, though.

My Apache virtual host:

<VirtualHost *.777>
    ServerAdmin [e-mail]
    ServerName localhost

    DocumentRoot "/srv/stone/public"

    ErrorLog "/srv/stone/app/storage/logs/apache-errors.log"
    CustomLog "/srv/stone/app/storage/logs/apache-custom.log" common

    <Directory /srv/stone/public>
        php_admin_value open_basedir /

        # Pretty URL rewrites, better not to rely on .htaccess
        <IfModule mod_rewrite.c>
            Options -MultiViews

            RewriteEngine On
            RewriteCond %{REQUEST_FILENAME} !-f
            RewriteRule ^ index.php [L]
        </IfModule>

        # Prevent further overrides
        AllowOverride None

        Order allow,deny
        Allow from all
    </Directory>
</VirtualHost>

And global config just has a specific entry for Listen 777.

This and this, both lead to DNS problem, so, I think I may have problems with it too, plus, it clearly looks like it.

I've given a shot by changing virtual host entries to 0.0.0.0:777 and other configurations to no avail.

How do I fix the issue?

Answer 1

It appears that the problem was with my /etc/resolv.conf.

I had set up a custom network connection manager, that executed an external command to set up nameservers from a specific configuration file. The setup would simply erase the contents of /etc/resolv.conf, append with new info and then start the network interface, set it's parameters (IP, Mask, Cast, Gate) and voila.

Apparently that screwed up something. I guess I will have to look for different Before/After targets and write a custom resolv.conf updater.

I did leave resolv.conf static now, and that seems to fix the issue.

In the end, clearly this was a DNS problem. Thankfully, it's fixed.

Answer 2

Have you tried the CURL_IPRESOLVE_V4 option?

$ch = curl_init('www.google.com');
curl_setopt($ch, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, false);
curl_setopt($ch, CURLOPT_HEADER, true);
curl_exec($ch);
var_dump(curl_error($ch));

And what is the output of the headers if you use the CURLOPT_HEADER option?