samples/bpf/xdp_monitor_kern.c

   1 /* XDP monitor tool, based on tracepoints
   2  *
   3  *  Copyright(c) 2017 Jesper Dangaard Brouer, Red Hat Inc.
   4  */
   5 #include <uapi/linux/bpf.h>
   6 #include "bpf_helpers.h"
   7
   8 struct bpf_map_def SEC("maps") redirect_err_cnt = {
   9         .type = BPF_MAP_TYPE_PERCPU_ARRAY,
  10         .key_size = sizeof(u32),
  11         .value_size = sizeof(u64),
  12         .max_entries = 2,
  13         /* TODO: have entries for all possible errno's */
  14 };
  15
  16 /* Tracepoint format: /sys/kernel/debug/tracing/events/xdp/xdp_redirect/format
  17  * Code in:                kernel/include/trace/events/xdp.h
  18  */
  19 struct xdp_redirect_ctx {
  20         unsigned short common_type;     //      offset:0;  size:2; signed:0;
  21         unsigned char common_flags;     //      offset:2;  size:1; signed:0;
  22         unsigned char common_preempt_count;//   offset:3;  size:1; signed:0;
  23         int common_pid;                 //      offset:4;  size:4; signed:1;
  24
  25         int prog_id;                    //      offset:8;  size:4; signed:1;
  26         u32 act;                        //      offset:12  size:4; signed:0;
  27         int ifindex;                    //      offset:16  size:4; signed:1;
  28         int err;                        //      offset:20  size:4; signed:1;
  29         int to_ifindex;                 //      offset:24  size:4; signed:1;
  30         u32 map_id;                     //      offset:28  size:4; signed:0;
  31         int map_index;                  //      offset:32  size:4; signed:1;
  32 };                                      //      offset:36
  33
  34 enum {
  35         XDP_REDIRECT_SUCCESS = 0,
  36         XDP_REDIRECT_ERROR = 1
  37 };
  38
  39 static __always_inline
  40 int xdp_redirect_collect_stat(struct xdp_redirect_ctx *ctx)
  41 {
  42         u32 key = XDP_REDIRECT_ERROR;
  43         int err = ctx->err;
  44         u64 *cnt;
  45
  46         if (!err)
  47                 key = XDP_REDIRECT_SUCCESS;
  48
  49         cnt  = bpf_map_lookup_elem(&redirect_err_cnt, &key);
  50         if (!cnt)
  51                 return 0;
  52         *cnt += 1;
  53
  54         return 0; /* Indicate event was filtered (no further processing)*/
  55         /*
  56          * Returning 1 here would allow e.g. a perf-record tracepoint
  57          * to see and record these events, but it doesn't work well
  58          * in-practice as stopping perf-record also unload this
  59          * bpf_prog.  Plus, there is additional overhead of doing so.
  60          */
  61 }
  62
  63 SEC("tracepoint/xdp/xdp_redirect_err")
  64 int trace_xdp_redirect_err(struct xdp_redirect_ctx *ctx)
  65 {
  66         return xdp_redirect_collect_stat(ctx);
  67 }
  68
  69
  70 SEC("tracepoint/xdp/xdp_redirect_map_err")
  71 int trace_xdp_redirect_map_err(struct xdp_redirect_ctx *ctx)
  72 {
  73         return xdp_redirect_collect_stat(ctx);
  74 }
  75
  76 /* Likely unloaded when prog starts */
  77 SEC("tracepoint/xdp/xdp_redirect")
  78 int trace_xdp_redirect(struct xdp_redirect_ctx *ctx)
  79 {
  80         return xdp_redirect_collect_stat(ctx);
  81 }
  82
  83 /* Likely unloaded when prog starts */
  84 SEC("tracepoint/xdp/xdp_redirect_map")
  85 int trace_xdp_redirect_map(struct xdp_redirect_ctx *ctx)
  86 {
  87         return xdp_redirect_collect_stat(ctx);
  88 }