No packet in IOUserNetworkRxSubmissionQueue

I am writing a NetworkingDriverKit extension.

So I subclassed IOUserNetworkEthernet. In my class Start method, among hardware specific things here is what I do:

• Allocate a IOUserNetworkPacketBufferPool, with IOUserNetworkPacketBufferPool::Create(this, "myPacketsPool", 5000, 5000, 10000, &ivars->PacketsPool);
• Create an IODispatchQueue with IODispatchQueue::Create("myPacketsDispatchQueue", 0, 0, &ivars->PacketsDispatchQueue);
• Create the IOUserNetworkPacketQueue objects:

IOUserNetworkRxSubmissionQueue::Create(ivars->PacketsPool, this, 250, 0, ivars->PacketsDispatchQueue, &ivars->RxSubmissionQueue);
IOUserNetworkRxCompletionQueue::Create(ivars->PacketsPool, this, 250, 0, ivars->PacketsDispatchQueue, &ivars->RxCompletionQueue);
IOUserNetworkTxSubmissionQueue::Create(ivars->PacketsPool, this, 250, 0, ivars->PacketsDispatchQueue, &ivars->TxSubmissionQueue);
IOUserNetworkTxCompletionQueue::Create(ivars->PacketsPool, this, 250, 0, ivars->PacketsDispatchQueue, &ivars->TxCompletionQueue);

queues[0] = ivars->RxSubmissionQueue;
queues[1] = ivars->RxCompletionQueue;
queues[2] = ivars->TxSubmissionQueue;
queues[3] = ivars->TxCompletionQueue;

• I register the ethernet interface: RegisterEthernetInterface(mac, ivars->PacketsPool, queues, 4);
• And I report link status with ReportLinkStatus(kIOUserNetworkLinkStatusActive, kIOUserNetworkMediaEthernet1000BaseT | kIOUserNetworkMediaOptionFullDuplex);

After that, the new network interface shows up in MacOS. I see that SetInterfaceEnable gets called with true as argument.

In the receive data path I get data from the USB device, which I want to pass to the network stack. So I try to get an empty packet with:

IOUserNetworkPacket * packet;
r = ivars->RxSubmissionQueue->DequeuePacket(&packet);

But at that point, I always get kIOReturnUnderrun.

Is there something else I should do to be able to dequeue empty packets from the IOUserNetworkRxSubmissionQueue ?

I already tried to enable the packets queues with:

ivars->RxSubmissionQueue->SetEnable(true);
ivars->RxCompletionQueue->SetEnable(true);
ivars->TxSubmissionQueue->SetEnable(true);
ivars->TxCompletionQueue->SetEnable(true);

But that doesn't change anything.