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Details

Type: Bug
Resolution: Done
Priority: P2: Important
Fix Version/s: 5.12.5, 5.13.1, 5.14.0 Alpha
Affects Version/s: 5.12.3, 5.13.0
Component/s: Network: Proxies
Labels:
None

Platform/s:

Windows
Commits:
2a15ec72c0d088a5dca344df163fac73c24caa1f (qt/qtbase/5.12)

Description

Its very related to the issue ~~QTBUG-22177~~, which was resolved years ago.

We setup a proxy server and the default behaviour of that server is to disconnect the connection when required authentication on HTTP/1.1.

The header that Proxy returned is:

Connetion: Close \r\n
Proxy-Connection: Close \r\n

Expected:

QT's QNetworkAccessManager reconnect to Proxy and send the authentication to Proxy.

Actual:

The signal proxyAuthenticationRequired never emitted and QNetworkAccessManager never reconnect to the Proxy.

What I found from QT 5.13.0 's source code:

        bool willClose;
        QByteArray proxyConnectionHeader = d->reply->headerField("Proxy-Connection");
        // Although most proxies use the unofficial Proxy-Connection header, the Connection header
        // from http spec is also allowed.
        if (proxyConnectionHeader.isEmpty())
            proxyConnectionHeader = d->reply->headerField("Connection");
        if (proxyConnectionHeader.compare("close", Qt::CaseSensitive) == 0) {
            willClose = true;
        } else if (proxyConnectionHeader.compare("keep-alive", Qt::CaseInsensitive) == 0) {
            willClose = false;
        } else {
            // no Proxy-Connection header, so use the default
            // HTTP 1.1's default behaviour is to keep persistent connections
            // HTTP 1.0 or earlier, so we expect the server to close
            willClose = (d->reply->majorVersion() * 0x100 + d->reply->minorVersion()) <= 0x0100;
        }

It seems already being refactored after this fix: https://codereview.qt-project.org/c/qt/qtbase/+/7484

The original one use the toLower to ignore the case:

proxyConnectionHeader = proxyConnectionHeader.toLower();

But the latest code (from QT 5.13.0) made some mistake (I guess):

proxyConnectionHeader.compare("close", Qt::CaseSensitive)

Attached Debug Info

I've saw the HTTP RFC spec and it defined:

Connection: close
Connection: Keep-Alive

But why Qt use Qt::CaseSensitive only for the close header then use Qt::CaseInsensitive for the keep-alive one? I guess both of them should use Qt::CaseInsensitive to enlarge the compatibility of such non-standard proxies, thus the upper case "Close" header from our Proxy server could be handled properly.