how QEMU guest can send packets to NIC of the host?

Issue

i'm trying to test XDP program but the test environment was provided by the client consists of one server and qemu guest running on it and act as a traffic generator ( using scapy or DPDK ). and to have this test run successfully,the packets from the guest should arrive/be injected to the NIC driver ( XDP working in native mode ) of the host. is there's any configs/hacks that can make the traffic goes from the guest to the host driver?

edit : some points to be cleared as @vipin suggested,

• on the host, the NIC is connected to virbr0 on kernel.
• the XDP is running on the physical NIC.
• i'm using bpf_redirect_map for redirecting as we still in simple stage.

anyway, i got a work around is just to add a physical router to the lab setup and it's enough for this stage of test.

Solution

XDP (Express Data Path) supported in Linux is for RX side, and there were patches for TX but not integrated. Based on the current update XDP-eBPF is on Physical NIC. So all RX packet on physical NIC is processed.

But as per the question shared packets from the guest should arrive/be injected to the NIC driver ( XDP working in native mode ) of the host.. If one needs to run the logic for traffic coming from GUEST OS, XDP has to be loaded to emulator or TAP or Bridge interface. This will allow to redirect packets based on Kernel NIC id to Physcial NIC.

Answered By - Vipin Varghese