QHostAddress:isInSubnet() always returns false

[itanitarek10]

Hello,

I am trying to search for a specific IPv4 address on a VirtualBox Linux VM. No matter what I set the argument parameters to for the isInSubnet() function call, it always returns false. The address I am searching for is 10.0.2.15. Even if I set the first parameter to 10.0.2.15 it still returns false, even though the documentation says it will return true. What gives?

    // get a list of all IP addresses on the workstation
    QList<QHostAddress> listOfAddresses = QNetworkInterface::allAddresses();
    QHostAddress workstationIPAddress;

    for(int i = 0; i<listOfAddresses.count(); i++)
    {
        if(!listOfAddresses[i].isLoopback())
        {
            if (listOfAddresses[i].protocol() == QAbstractSocket::IPv4Protocol)
            {
                if (listOfAddresses[i].isInSubnet(QHostAddress("10.0.2.0"),
                                                  QHostAddress("255.255.255.0")
                                                  .toIPv4Address()))
                {
                     workstationIPAddress = listOfAddresses[i];
                     break;
                }
            }
        }
    }

Thank you

[SGaist]

Hi,

Which guest OS are you running ?

Did you print the value of each address you test ?

[itanitarek10]

This post is deleted!

[itanitarek10]

@SGaist
I am running RedHat 8.

And yes I did verify each value that is being tested by placing breakpoints and seeing what address passes through each if statement. QNetworkInterface::allAddresses() returns 4 addresses, one of which is the address I am looking for.

[Christian Ehrlicher]

Then please write a minimal, compilable example with hard-coded addresses so we can try to reproduce it here.

[Jerry.Liu]

@itanitarek10 mask is not "mask"(255.255.255.0), should prefixLength. like linux format.
example: 192.168.0.123/24

testCncConnect() {
    QString lDevIp = RcUtilsGlobal::GetInstance()->getDeviceIP();
    QHostAddress lDevAddr;
    if(!lDevAddr.setAddress(lDevIp)) {
        LOG_DBG("set dev ip to QHostAddress false, devIP:" + lDevIp);
        return false;
    }
    LOG_DEBUG("DevIP to QHostAddress: " + lDevIp  + "->" + lDevAddr.toString());

    QList<QNetworkInterface> lInterfaceList = QNetworkInterface::allInterfaces();
    QList<QNetworkInterface> lRunningEthernetInterfaces;

    for(const auto & lInterface: lInterfaceList) {
        if(lInterface.type() != QNetworkInterface::Ethernet || (lInterface.flags() & QNetworkInterface::IsRunning) == 0) {
            LOG_DEBUG(QString("Network: %1(%2) is not Ethernet or not Running").arg(lInterface.name()).arg(lInterface.humanReadableName()));
            continue;
        }
        lRunningEthernetInterfaces << lInterface;
    }

    for(const auto & lInterface: lRunningEthernetInterfaces) {
        const QList<QNetworkAddressEntry> & lInteraceAddressEnteries = lInterface.addressEntries();
        for(const auto & lNetworkAddressEntry : lInteraceAddressEnteries) {
            const QHostAddress lIp = lNetworkAddressEntry.ip();
            if(lIp.protocol() != QAbstractSocket::NetworkLayerProtocol::IPv4Protocol)
                continue;
            const QHostAddress lMask = lNetworkAddressEntry.netmask();

            bool bInSub = lDevAddr.isInSubnet(lIp, lNetworkAddressEntry.prefixLength());
            LOG_DEBUG(QString("Network: %1(%2) lIp: %3/%4 inThisSub: %5")
                      .arg(lInterface.name()).arg(lInterface.humanReadableName()).arg(lIp.toString()).arg(lNetworkAddressEntry.prefixLength())
                      .arg(bInSub ? "in": "not"));
        }
    }
    return false;
}