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 #define XDP_UNKNOWN     XDP_REDIRECT + 1
  17 struct bpf_map_def SEC("maps") exception_cnt = {
  18         .type           = BPF_MAP_TYPE_PERCPU_ARRAY,
  19         .key_size       = sizeof(u32),
  20         .value_size     = sizeof(u64),
  21         .max_entries    = XDP_UNKNOWN + 1,
  22 };
  23
  24 /* Tracepoint format: /sys/kernel/debug/tracing/events/xdp/xdp_redirect/format
  25  * Code in:                kernel/include/trace/events/xdp.h
  26  */
  27 struct xdp_redirect_ctx {
  28         u64 __pad;              // First 8 bytes are not accessible by bpf code
  29         int prog_id;            //      offset:8;  size:4; signed:1;
  30         u32 act;                //      offset:12  size:4; signed:0;
  31         int ifindex;            //      offset:16  size:4; signed:1;
  32         int err;                //      offset:20  size:4; signed:1;
  33         int to_ifindex;         //      offset:24  size:4; signed:1;
  34         u32 map_id;             //      offset:28  size:4; signed:0;
  35         int map_index;          //      offset:32  size:4; signed:1;
  36 };                              //      offset:36
  37
  38 enum {
  39         XDP_REDIRECT_SUCCESS = 0,
  40         XDP_REDIRECT_ERROR = 1
  41 };
  42
  43 static __always_inline
  44 int xdp_redirect_collect_stat(struct xdp_redirect_ctx *ctx)
  45 {
  46         u32 key = XDP_REDIRECT_ERROR;
  47         int err = ctx->err;
  48         u64 *cnt;
  49
  50         if (!err)
  51                 key = XDP_REDIRECT_SUCCESS;
  52
  53         cnt  = bpf_map_lookup_elem(&redirect_err_cnt, &key);
  54         if (!cnt)
  55                 return 1;
  56         *cnt += 1;
  57
  58         return 0; /* Indicate event was filtered (no further processing)*/
  59         /*
  60          * Returning 1 here would allow e.g. a perf-record tracepoint
  61          * to see and record these events, but it doesn't work well
  62          * in-practice as stopping perf-record also unload this
  63          * bpf_prog.  Plus, there is additional overhead of doing so.
  64          */
  65 }
  66
  67 SEC("tracepoint/xdp/xdp_redirect_err")
  68 int trace_xdp_redirect_err(struct xdp_redirect_ctx *ctx)
  69 {
  70         return xdp_redirect_collect_stat(ctx);
  71 }
  72
  73
  74 SEC("tracepoint/xdp/xdp_redirect_map_err")
  75 int trace_xdp_redirect_map_err(struct xdp_redirect_ctx *ctx)
  76 {
  77         return xdp_redirect_collect_stat(ctx);
  78 }
  79
  80 /* Likely unloaded when prog starts */
  81 SEC("tracepoint/xdp/xdp_redirect")
  82 int trace_xdp_redirect(struct xdp_redirect_ctx *ctx)
  83 {
  84         return xdp_redirect_collect_stat(ctx);
  85 }
  86
  87 /* Likely unloaded when prog starts */
  88 SEC("tracepoint/xdp/xdp_redirect_map")
  89 int trace_xdp_redirect_map(struct xdp_redirect_ctx *ctx)
  90 {
  91         return xdp_redirect_collect_stat(ctx);
  92 }
  93
  94 /* Tracepoint format: /sys/kernel/debug/tracing/events/xdp/xdp_exception/format
  95  * Code in:                kernel/include/trace/events/xdp.h
  96  */
  97 struct xdp_exception_ctx {
  98         u64 __pad;      // First 8 bytes are not accessible by bpf code
  99         int prog_id;    //      offset:8;  size:4; signed:1;
 100         u32 act;        //      offset:12; size:4; signed:0;
 101         int ifindex;    //      offset:16; size:4; signed:1;
 102 };
 103
 104 SEC("tracepoint/xdp/xdp_exception")
 105 int trace_xdp_exception(struct xdp_exception_ctx *ctx)
 106 {
 107         u64 *cnt;;
 108         u32 key;
 109
 110         key = ctx->act;
 111         if (key > XDP_REDIRECT)
 112                 key = XDP_UNKNOWN;
 113
 114         cnt = bpf_map_lookup_elem(&exception_cnt, &key);
 115         if (!cnt)
 116                 return 1;
 117         *cnt += 1;
 118
 119         return 0;
 120 }