QWebView using QNetworkAccessManager to deal with requests/responses. Only useful thing you can override is a virtual
QNetworkReply * QNetworkAccessManager::createRequest(Operation op,
const QNetworkRequest & req, QIODevice * outgoingData = 0) [virtual protected]
which unfortunately is not really useful for your purposes..
As well I don't think the Bearer thing will work either.
So, depending on how bad you need this functionality I would look into making changes in QNetworkAccessManager to be able to pass list of allowed interfaces/ip addresses, so QTcpSocket it will bind itself to specified IP address.. and then set this AccessManager to WebView.
As far as I know specifying bind address is not supported for QNetworkAccessManager