TYPO3 Core

Almost every software which allows connections to different domains allows the configuration of proxies. And exceptions for them.
Thus not every connection uses the proxy configured.

TYPO3 allows to configure a proxy used by Curl. But when activated every connection will use this proxy. Especially in complex server environments this limits possible settings. An admin has to decide to either allow connections to the outer world (Extension Updates, Translation Handling) or other servers in the local network.

Best would be to allow the configuration of Exceptions for Curl in localconf.php. e.g.

$TYPO3_CONF_VARS['SYS']['curlProxyExceptions'] = '*.localdomain,*.local';

and adjust the method getURL() in class.t3lib_div.php to use the proxy only when there is no exception for the current domain.

Thereby every extension that uses this method can benefit from this feature and doesn't have to implement the whole "download-files-from-the-right-location-and-sometimes-with-proxy" stuff.