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multi interface proxy issue

From: Thomas Herchek <>
Date: Wed, 21 May 2014 12:41:30 -0400


One of our customers is having an issue traversing an HTTP authenticated proxy using our application. We are using libcurl 7.33.0 and specify CURL_AUTH_ANY for proxy authentication.

Our application uses both the multi and non-multi libcurl interfaces. The code that does not use the multi interface has no problem authenticating to the proxy and reaching the Internet. From the logs I can see it is using NTLM for the auth. But the code that uses the multi interface just hangs for 30 minutes when traversing the proxy before timing out. The customer is using a Forefront TMG proxy.

I see there is Known Bug 65 that says “libcurl will fail if the (passive) TCP connection for the data transfer isn’t more or less instant because it doesn’t wait for a connect confirmation”. Is that the likely issue? Do you have any debugging suggestions or work arounds?

Any help is appreciated. Thanks.

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Received on 2014-05-21