I've built an open-source DriverKit + NetworkingDriverKit (IOUserNetworkEthernet/Skywalk) driver for a USB 5GbE adapter (AQTION AQC111U chipset). As far as I can tell this is the first public one for real third-party hardware:
github.com/jquirke/AQC111Driver
It's a fully functional driver at this point: RX/TX hardware checksum offload, jumbo frame/MTU control up to 16KB, runtime-controllable diagnostics via a custom IOUserClient, and most recently working 802.1Q VLAN support via macOS's vlan(4) software path.
While attempting to implement hardware offload VLAN support, I ran into what looks like a gap between documentation and the public SDK, and I'd appreciate expert opinion either way before filing Feedback.
The issue:
IOUserNetworkPacket::getVlanTag()/setVlanTag() (DriverKit 24.0+) have a doc comment stating: "Get the Vlan Tag from the packet, where the driver has enabled the kFeatureHardwareVlan capability; for the case that feature is not enabled, this method will return false."
kFeatureHardwareVlan does not appear anywhere in the public NetworkingDriverKit.framework/Headers/ tree confirmed via exhaustive grep, including the full hwAssist/feature-flag enum in IOUserNetworkTypes.h.
I tested every plausible related mechanism exhaustively, with a real device reattach for each combination, to rule out attach-time-only behaviour:
+------------------------+--------------------------+--------------+-----------+
| HWAssist bit declared? | SetSoftwareVlanSupport()| getVlanTag() | vlan0 MTU |
+------------------------+--------------------------+--------------+-----------+
| Yes | true | always false | 1500 |
| Yes | false | always false | 1500 |
| No | not called | always false | 1496 |
| No | false | always false | 1496 |
+------------------------+--------------------------+--------------+-----------+
none of these combinations gates real 802.1q tag-delivery/demux behavior at all; it seems Vlan support is completely implemented in software on the MacOS side and I have to explicitly program my hardware registers to disable VLAN tagging.
Question: is hardware VLAN tag insert/strip (via getVlanTag()/setVlanTag()) currently reachable from a third-party DriverKit USB Ethernet driver at all? If kFeatureHardwareVlan is real but intentionally withheld from public headers, is there a documented path (entitlement, different NDK version, etc.) to enable it or is this confirmed unreachable without Apple's direct involvement (Feedback/DTS)?
Can share full test logs/methodology if useful.
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