Hi there!

> KS Lee <kslee_at_soft-skills.com.my> hat am 7. Oktober 2015 um 12:19 geschrieben:
>
>
> Hi
> This problem has stumped us for a good part of this past week.
>
> We had a C++ code using libcurl running for the past five or so years, was
> working fine until this week.
>
> This is a service that connects to a HTTPS-based IBM Websphere. It sends &
> receives financial transactions. We don't operate the web server i.e. it
> is third-party and hence, we have no control over it.
>
> Here's what stumping us:
>
> 1. The exact same program, if connected through a proxy server to the same
> web server, runs without any errors. This service continues to run with
> nary a blip.
>
> 2. The same code, running on a different server with NO proxy i.e. directly
> connected to the web-server via a firewall, has decided to act up.
> Starting this past Monday, we've been consistenly getting the
> CURLE_RECV_ERROR "Failure when receiving data from the peer" after a
> successful POST.
>
> 3. We enabled all tracing from libcurl CURLOPT_DEBUGFUNCTION. We do see
> fragments of messages coming back and are duly collected into a buffer
> properly.
>
> 4. We know something on the third-party web server has changed, but we
> don't know what, and the operator of the site is under no obligation to
> tell us anything. And they don't.
>
> 5. What we have tried so far, with no success:
> a. Changing the User-Agent string to use more "modern" browser
> identification.
>
> b. The code fragment (assumed variables defined, this is a large routine):
>
> CURLcode curlCode = CURLE_READ_ERROR; // Dummy value
> while ( ( pCurlMsg = curl_multi_info_read( m_pMultiCurlHandle,
> &msgs_left ) ) )
> {
> if ( pCurlMsg->msg == CURLMSG_DONE )
> {
> curlCode = pCurlMsg->data.result;
> curl_easy_getinfo( pCurlMsg->easy_handle,
>
> CURLINFO_RESPONSE_CODE,
> &lHttpResponseCode
> );
> break; // Out of while loop
> }
> }
>
> // At this point:
> // curlCode == CURLE_RECV_ERROR if we are not connecting via a
> proxy!!
>
> 6. Here are the libcurl settings called for the non-proxy version:
>
> curl_global_init(CURL_GLOBAL_ALL);
> curl_easy_setopt(m_pCurl, CURLOPT_USERAGENT, "bla bla bla");
> curl_easy_setopt(m_pCurl, CURLOPT_WRITEFUNCTION, HttpGetCallback);
> curl_easy_setopt(m_pCurl, CURLOPT_WRITEDATA, &m_stHTMLPage);
> curl_easy_setopt(m_pCurl, CURLOPT_DEBUGFUNCTION, CurlDebugCallback);
> curl_easy_setopt(m_pCurl, CURLOPT_DEBUGDATA, this);
> curl_easy_setopt(m_pCurl, CURLOPT_VERBOSE, true);
> curl_easy_setopt(m_pCurl, CURLOPT_AUTOREFERER, 1);
> curl_easy_setopt(m_pCurl, CURLOPT_UNRESTRICTED_AUTH, 1);
> curl_easy_setopt(m_pCurl, CURLOPT_HEADER, 1);
> curl_easy_setopt(m_pCurl, CURLOPT_SSL_VERIFYPEER, 0);
> curl_easy_setopt(m_pCurl, CURLOPT_SSL_VERIFYHOST, 0);
> curl_easy_setopt(m_pCurl, CURLOPT_COOKIEFILE, "");
> curl_easy_setopt(m_pCurl, CURLOPT_COOKIESESSION , 1);
> curl_easy_setopt(m_pCurl, CURLOPT_FOLLOWLOCATION, 1);
> curl_easy_setopt(m_pCurl, CURLOPT_ACCEPT_ENCODING, "deflate, gzip");
> curl_easy_setopt(m_pCurl, CURLOPT_INTERFACE, "192.168.128.61"); // some IP
>
> 7. What can possibly be changed on the third-party that could have
> affected this non-proxy service but NOT the one connected through a proxy.
> They are the exact SAME program!
>
> Any help is deeply appreciated.

1. I assume HTTPS is used always with your service.
2. There is no problem with establishing the SSL connection neither directly
nor through the proxy.

If 1 and 2 hold true, this should eliminate SSL as the problem, except maybe
for some weird renegotiation stuff.

I would look at the HTTP headers. See if theres anything that could cause a
hickup on the remote end. Look at the response header you get from the web
server. Especially look at the differences in the headers when connecting
directly vs. via proxy. Post sanitized versions of those headers here(remove
authentication data). This is the least that is needed to start guessing.

Greeting,
  Michael
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Received on 2015-10-07