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8d53e6f · Jan 3, 2025

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AF_XDP-forwarding

AF_XDP socket multi-threaded forwarding sample application

This sample code could originally be found in the Linux source code tree under samples/bpf. It illustrates the packet forwarding between multiple AF_XDP sockets in multi-threading environment. All the threads and sockets are sharing a common buffer pool, with each socket having its own private buffer cache. The sockets are created with the xsk_socket__create_shared() function, which allows multiple AF_XDP sockets to share the same UMEM object.

Example 1: Single thread handling two sockets. Packets received from socket A (on top of interface IFA, queue QA) are forwarded to socket B (on top of interface IFB, queue QB) and vice-versa. The thread is affinitized to CPU core C:

./xsk_fwd -i IFA -q QA -i IFB -q QB -c C

Example 2: Two threads, each handling two sockets. Packets from socket A are sent to socket B (by thread X), packets from socket B are sent to socket A (by thread X); packets from socket C are sent to socket D (by thread Y), packets from socket D are sent to socket C (by thread Y). The two threads are bound to CPU cores CX and CY:

./xdp_fwd -i IFA -q QA -i IFB -q QB -i IFC -q QC -i IFD -q QD -c CX -c CY