Marcus Wichelmann wrote:
The existing XDP metadata test works by creating a veth pair and attaching XDP & TC programs that drop the packet when the condition of the test isn't fulfilled. The test then pings through the veth pair and succeeds when the ping comes through.
While this test works great for a veth pair, it is hard to replicate for tap devices to test the XDP metadata support of them. A similar test for the tun driver would either involve logic to reply to the ping request, or would have to capture the packet to check if it was dropped or not.
To make the testing of other drivers easier while still maximizing code reuse, this commit refactors the existing xdp_context_functional test to use a test_result map. Instead of conditionally passing or dropping the packet, the TC program is changed to copy the received metadata into the value of that single-entry array map. Tests can then verify that the map value matches the expectation.
This testing logic is easy to adapt to other network drivers as the only remaining requirement is that there is some way to send a custom Ethernet packet through it that triggers the XDP & TC programs.
The Ethernet header of that custom packet is all-zero, because it is not required to be valid for the test to work. The zero ethertype also helps to filter out packets that are not related to the test and would otherwise interfere with it.
The payload of the Ethernet packet is used as the test data that is expected to be passed as metadata from the XDP to the TC program and written to the map. It has a fixed size of 32 bytes which is a reasonable size that should be supported by both drivers. Additional packet headers are not necessary for the test and were therefore skipped to keep the testing code short.
This new testing methodology no longer requires the veth interfaces to have IP addresses assigned, therefore these were removed.
Signed-off-by: Marcus Wichelmann marcus.wichelmann@hetzner-cloud.de
Reviewed-by: Willem de Bruijn willemb@google.com