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Issues with http proxy requests with 7.79.0

From: Abhinav Singhal via curl-library <>
Date: Tue, 21 Sep 2021 00:35:31 -0400

I'm tasked to upgrade the curl version at work from the current 7.71 to the
latest 7.79.0. The issue I am running into is that one of the tests that
validates whether an http proxy server is running by sending it a dummy url
is failing with this error:

Error: command failed: HTTP proxy configuration is invalid. Reason: Empty
reply from server

The expected HTTP error message for this operation is 403 (forbidden), but
the server is not returning anything. The same code works perfectly fine
with 7.71.1.

Question is, what changed between 7.71.1 and 7.79.0 that could have caused
this issue? The only issue I ran into while building the latest libcurl was
that it prompted me to add a TLS backend, or disable it, which I fixed by
adding the --with-openssl.

Do I need to add any other option here in order for this request to go
through? Moreover, this failure is also observed on 7.78.0, the other build
that I tried out.

These are the curl_easy_setopt options currently being used in the code (in
type (value) format) that work with 7.71.1, but fail with 7.79.0:

Does anything here seem missing? Any inputs would help.

This is the http-proxy server configuration to which the requests are being
Squid Cache: Version 4.14


Received on 2021-09-21