Release 4.15 samples/bpf/xdp_monitor_kern.c

/* XDP monitor tool, based on tracepoints
 *
 *  Copyright(c) 2017 Jesper Dangaard Brouer, Red Hat Inc.
 */
#include <uapi/linux/bpf.h>
#include "bpf_helpers.h"

struct bpf_map_def SEC("maps") redirect_err_cnt = {
	.type = BPF_MAP_TYPE_PERCPU_ARRAY,
	.key_size = sizeof(u32),
	.value_size = sizeof(u64),
	.max_entries = 2,
	/* TODO: have entries for all possible errno's */
};


#define XDP_UNKNOWN	XDP_REDIRECT + 1
struct bpf_map_def SEC("maps") exception_cnt = {
	.type		= BPF_MAP_TYPE_PERCPU_ARRAY,
	.key_size	= sizeof(u32),
	.value_size	= sizeof(u64),
	.max_entries	= XDP_UNKNOWN + 1,
};

/* Tracepoint format: /sys/kernel/debug/tracing/events/xdp/xdp_redirect/format
 * Code in:                kernel/include/trace/events/xdp.h
 */

struct xdp_redirect_ctx {
	
u64 __pad;		// First 8 bytes are not accessible by bpf code
	
int prog_id;		//      offset:8;  size:4; signed:1;
	
u32 act;		//      offset:12  size:4; signed:0;
	
int ifindex;		//      offset:16  size:4; signed:1;
	
int err;		//      offset:20  size:4; signed:1;
	
int to_ifindex;		//      offset:24  size:4; signed:1;
	
u32 map_id;		//      offset:28  size:4; signed:0;
	
int map_index;		//      offset:32  size:4; signed:1;
};				//      offset:36

enum {
	
XDP_REDIRECT_SUCCESS = 0,
	
XDP_REDIRECT_ERROR = 1
};


static __always_inline

int xdp_redirect_collect_stat(struct xdp_redirect_ctx *ctx)
{
	u32 key = XDP_REDIRECT_ERROR;
	int err = ctx->err;
	u64 *cnt;

	if (!err)
		key = XDP_REDIRECT_SUCCESS;

	cnt  = bpf_map_lookup_elem(&redirect_err_cnt, &key);
	if (!cnt)
		return 1;
	*cnt += 1;

	return 0; /* Indicate event was filtered (no further processing)*/
	/*
         * Returning 1 here would allow e.g. a perf-record tracepoint
         * to see and record these events, but it doesn't work well
         * in-practice as stopping perf-record also unload this
         * bpf_prog.  Plus, there is additional overhead of doing so.
         */
}

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SEC("tracepoint/xdp/xdp_redirect_err")


int trace_xdp_redirect_err(struct xdp_redirect_ctx *ctx)
{
	return xdp_redirect_collect_stat(ctx);
}


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SEC("tracepoint/xdp/xdp_redirect_map_err")


int trace_xdp_redirect_map_err(struct xdp_redirect_ctx *ctx)
{
	return xdp_redirect_collect_stat(ctx);
}

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/* Likely unloaded when prog starts */
SEC("tracepoint/xdp/xdp_redirect")


int trace_xdp_redirect(struct xdp_redirect_ctx *ctx)
{
	return xdp_redirect_collect_stat(ctx);
}

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/* Likely unloaded when prog starts */
SEC("tracepoint/xdp/xdp_redirect_map")


int trace_xdp_redirect_map(struct xdp_redirect_ctx *ctx)
{
	return xdp_redirect_collect_stat(ctx);
}

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/* Tracepoint format: /sys/kernel/debug/tracing/events/xdp/xdp_exception/format
 * Code in:                kernel/include/trace/events/xdp.h
 */

struct xdp_exception_ctx {
	
u64 __pad;	// First 8 bytes are not accessible by bpf code
	
int prog_id;	//      offset:8;  size:4; signed:1;
	
u32 act;	//      offset:12; size:4; signed:0;
	
int ifindex;	//      offset:16; size:4; signed:1;
};

SEC("tracepoint/xdp/xdp_exception")


int trace_xdp_exception(struct xdp_exception_ctx *ctx)
{
	u64 *cnt;;
	u32 key;

	key = ctx->act;
	if (key > XDP_REDIRECT)
		key = XDP_UNKNOWN;

	cnt = bpf_map_lookup_elem(&exception_cnt, &key);
	if (!cnt)
		return 1;
	*cnt += 1;

	return 0;
}
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Directory: samples/bpf

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