AF_XDP based bridge

Transfers L2 packets between two interfaces (in both directions) as is with the help of AF_XDP technology https://www.kernel.org/doc/html/v4.18/networking/af_xdp.html

Packets from client to world travel via userspace and can be controlled (find validate_packets, an application logic stub). Packets from world to client travel via kernelspace only.

Usage

# ./build/xdpbridge/xdpbridge -h
  Usage: xdpbridge [OPTIONS]
  Options :
  -i, --client-interface=input_iface	Client interface
  -o, --world-interface=output_iface	World interface
  -q, --queues=n	Number of client-side incoming queues and threads (default 1)
  -t, --transmit-queue=n	Transmit queue (can be set multiple times)
  -b, --bidirectional	Transfer packets from world to client as well
  -S, --xdp-skb-client Enforce XDP skb-mod for client interface
  -N, --xdp-native-client	Enforce XDP native mode for client interface
  -Z, --xdp-zerocopy-client	Enforce XDP zerocopy for client interface
  -C, --xdp-copy-client	Enforce XDP copy for client interface
  -s, --xdp-skb-world Enforce XDP skb-mod for world interface
  -n, --xdp-native-world	Enforce XDP native mode for world interface
  -z, --xdp-zerocopy-world	Enforce XDP zerocopy for world interface
  -c, --xdp-copy-world	Enforce XDP copy for world interface

Thread model for c=>w part is a thread per queue.

If no transmit-queue is specified, Nth transmit queue (at world interface) is used to send a packet received via Nth incoming queue (at client interface).

Note, that some hardware or drivers require that transmit queues (at world side) are dedicated, without incoming traffic, that is why transmit-queue option is introduced.

Build prerequisites

• g++
• clang
• cmake
• libelf
• linux kernel tree 4.18 or 5 (make oldconfig && make prepare && make headers_install && make)

Build procedure

cmake -DKERNEL_TOP=/path/to/kernel/tree . && make