This all happens after the packet is transferred over PCIe to the CPU/memory (even the interrupt happens after DMA transfer). Otherwise the XDP code wouldn't h

This all happens after the packet is transferred over PCIe to the CPU/memory (even the interrupt happens after DMA transfer). Otherwise the XDP code wouldn't have access to the packet to filter it; the example doesn't just drop all packets, it drops all packets matching a /24 subnet which happens to be all packets here ;)