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Diffstat (limited to 'Documentation/networking/af_xdp.rst')
| -rw-r--r-- | Documentation/networking/af_xdp.rst | 26 |
1 files changed, 21 insertions, 5 deletions
diff --git a/Documentation/networking/af_xdp.rst b/Documentation/networking/af_xdp.rst index 50bccbf68308..83f7ae5fc045 100644 --- a/Documentation/networking/af_xdp.rst +++ b/Documentation/networking/af_xdp.rst @@ -153,10 +153,12 @@ an example, if the UMEM is 64k and each chunk is 4k, then the UMEM has Frames passed to the kernel are used for the ingress path (RX rings). -The user application produces UMEM addrs to this ring. Note that the -kernel will mask the incoming addr. E.g. for a chunk size of 2k, the -log2(2048) LSB of the addr will be masked off, meaning that 2048, 2050 -and 3000 refers to the same chunk. +The user application produces UMEM addrs to this ring. Note that, if +running the application with aligned chunk mode, the kernel will mask +the incoming addr. E.g. for a chunk size of 2k, the log2(2048) LSB of +the addr will be masked off, meaning that 2048, 2050 and 3000 refers +to the same chunk. If the user application is run in the unaligned +chunks mode, then the incoming addr will be left untouched. UMEM Completion Ring @@ -220,7 +222,21 @@ Usage In order to use AF_XDP sockets there are two parts needed. The user-space application and the XDP program. For a complete setup and usage example, please refer to the sample application. The user-space -side is xdpsock_user.c and the XDP side xdpsock_kern.c. +side is xdpsock_user.c and the XDP side is part of libbpf. + +The XDP code sample included in tools/lib/bpf/xsk.c is the following:: + + SEC("xdp_sock") int xdp_sock_prog(struct xdp_md *ctx) + { + int index = ctx->rx_queue_index; + + // A set entry here means that the correspnding queue_id + // has an active AF_XDP socket bound to it. + if (bpf_map_lookup_elem(&xsks_map, &index)) + return bpf_redirect_map(&xsks_map, index, 0); + + return XDP_PASS; + } Naive ring dequeue and enqueue could look like this:: |