linux/samples/bpf/tcp_dumpstats_kern.c

// SPDX-License-Identifier: GPL-2.0
/* Refer to samples/bpf/tcp_bpf.readme for the instructions on
 * how to run this sample program.
 */
#include <linux/bpf.h>

#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>

#define INTERVAL			1000000000ULL

int _version SEC("version") = 1;
char _license[] SEC("license") = "GPL";

struct {
	__u32 type;
	__u32 map_flags;
	int *key;
	__u64 *value;
} bpf_next_dump SEC(".maps") = {
	.type = BPF_MAP_TYPE_SK_STORAGE,
	.map_flags = BPF_F_NO_PREALLOC,
};

SEC("sockops")
int _sockops(struct bpf_sock_ops *ctx)
{
	struct bpf_tcp_sock *tcp_sk;
	struct bpf_sock *sk;
	__u64 *next_dump;
	__u64 now;

	switch (ctx->op) {
	case BPF_SOCK_OPS_TCP_CONNECT_CB:
		bpf_sock_ops_cb_flags_set(ctx, BPF_SOCK_OPS_RTT_CB_FLAG);
		return 1;
	case BPF_SOCK_OPS_RTT_CB:
		break;
	default:
		return 1;
	}

	sk = ctx->sk;
	if (!sk)
		return 1;

	next_dump = bpf_sk_storage_get(&bpf_next_dump, sk, 0,
				       BPF_SK_STORAGE_GET_F_CREATE);
	if (!next_dump)
		return 1;

	now = bpf_ktime_get_ns();
	if (now < *next_dump)
		return 1;

	tcp_sk = bpf_tcp_sock(sk);
	if (!tcp_sk)
		return 1;

	*next_dump = now + INTERVAL;

	bpf_printk("dsack_dups=%u delivered=%u\n",
		   tcp_sk->dsack_dups, tcp_sk->delivered);
	bpf_printk("delivered_ce=%u icsk_retransmits=%u\n",
		   tcp_sk->delivered_ce, tcp_sk->icsk_retransmits);

	return 1;
}