samples/bpf/xdp_rxq_info_kern.c

   1 /* SPDX-License-Identifier: GPL-2.0
   2  * Copyright (c) 2017 Jesper Dangaard Brouer, Red Hat Inc.
   3  *
   4  *  Example howto extract XDP RX-queue info
   5  */
   6 #include <uapi/linux/bpf.h>
   7 #include "bpf_helpers.h"
   8
   9 /* Config setup from with userspace
  10  *
  11  * User-side setup ifindex in config_map, to verify that
  12  * ctx->ingress_ifindex is correct (against configured ifindex)
  13  */
  14 struct config {
  15         __u32 action;
  16         int ifindex;
  17 };
  18 struct bpf_map_def SEC("maps") config_map = {
  19         .type           = BPF_MAP_TYPE_ARRAY,
  20         .key_size       = sizeof(int),
  21         .value_size     = sizeof(struct config),
  22         .max_entries    = 1,
  23 };
  24
  25 /* Common stats data record (shared with userspace) */
  26 struct datarec {
  27         __u64 processed;
  28         __u64 issue;
  29 };
  30
  31 struct bpf_map_def SEC("maps") stats_global_map = {
  32         .type           = BPF_MAP_TYPE_PERCPU_ARRAY,
  33         .key_size       = sizeof(u32),
  34         .value_size     = sizeof(struct datarec),
  35         .max_entries    = 1,
  36 };
  37
  38 #define MAX_RXQs 64
  39
  40 /* Stats per rx_queue_index (per CPU) */
  41 struct bpf_map_def SEC("maps") rx_queue_index_map = {
  42         .type           = BPF_MAP_TYPE_PERCPU_ARRAY,
  43         .key_size       = sizeof(u32),
  44         .value_size     = sizeof(struct datarec),
  45         .max_entries    = MAX_RXQs + 1,
  46 };
  47
  48 SEC("xdp_prog0")
  49 int  xdp_prognum0(struct xdp_md *ctx)
  50 {
  51         void *data_end = (void *)(long)ctx->data_end;
  52         void *data     = (void *)(long)ctx->data;
  53         struct datarec *rec, *rxq_rec;
  54         int ingress_ifindex;
  55         struct config *config;
  56         u32 key = 0;
  57
  58         /* Global stats record */
  59         rec = bpf_map_lookup_elem(&stats_global_map, &key);
  60         if (!rec)
  61                 return XDP_ABORTED;
  62         rec->processed++;
  63
  64         /* Accessing ctx->ingress_ifindex, cause BPF to rewrite BPF
  65          * instructions inside kernel to access xdp_rxq->dev->ifindex
  66          */
  67         ingress_ifindex = ctx->ingress_ifindex;
  68
  69         config = bpf_map_lookup_elem(&config_map, &key);
  70         if (!config)
  71                 return XDP_ABORTED;
  72
  73         /* Simple test: check ctx provided ifindex is as expected */
  74         if (ingress_ifindex != config->ifindex) {
  75                 /* count this error case */
  76                 rec->issue++;
  77                 return XDP_ABORTED;
  78         }
  79
  80         /* Update stats per rx_queue_index. Handle if rx_queue_index
  81          * is larger than stats map can contain info for.
  82          */
  83         key = ctx->rx_queue_index;
  84         if (key >= MAX_RXQs)
  85                 key = MAX_RXQs;
  86         rxq_rec = bpf_map_lookup_elem(&rx_queue_index_map, &key);
  87         if (!rxq_rec)
  88                 return XDP_ABORTED;
  89         rxq_rec->processed++;
  90         if (key == MAX_RXQs)
  91                 rxq_rec->issue++;
  92
  93         return config->action;
  94 }
  95
  96 char _license[] SEC("license") = "GPL";