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I've been creating a virtual ethernet interface. I've opened asynchronous communication with a controlling application and every time there are new packets, the controlling app is notified and then asks for the packet data. The packet data is stored in a simple struct, with uint8_t[1600] for the bytes, and uint32_t for the length. The dext is able to populate this struct with dummy data every time a packet is available, with the dummy data visible on the controlling application. However, I'm struggling to fill it with the real packet data. The IOUserNetworkPacket provides metadata about a packet. It contains a packets timestamp, size, etc, but it doesn't seem to contain the packet's data. There are the GetDataOffset() and GetMemorySegmentOffset() methods which seem to return byte offsets for where the packet data is located in their memory buffer. My instinct tells me to add this offset to the pointer of wherever the packet data is stored. The problem is I have no idea where the packets are actually stored. I know they are managed by the IOUserNetworkPacketBufferPool, but I don't think that's where their memory is. There is the CopyMemoryDescriptor() method which gives an IOMemoryDescriptor of its contents. I tried using the descriptor to create an IOMemoryMap, using it to call GetAddress(). The pointers to all the mentioned objects lead to junk data. I must be approaching this entirely wrong. If anyone knows how to access the packet data, or has any ideas, I would appreciate any help. Thanks.

I have tried extending IOUserNetworkEthernet and calling RegisterEthernetInterface. This works perfectly for one ethernet interface, though the driver crashes when RegisterEthernetInterface is called a second time (doesn't return an error code). I have tried registering with separate queues. Another approach was extending IOUserClient instead, and calling IOService::Create to create child IOUserNetworkEthernet instances. Everything about this approach works (the children appear within ioreg). However, once I call RegisterEthernetInterface on just one of the children, macOS crashes. How would I go about creating a dext with multiple ethernet interfaces? Have I been approaching it the right way? Thanks, Jake