connect4_dropper.c

 1// SPDX-License-Identifier: GPL-2.0
 2
 3#include <string.h>
 4
 5#include <linux/stddef.h>
 6#include <linux/bpf.h>
 7
 8#include <sys/socket.h>
 9
10#include <bpf/bpf_helpers.h>
11#include <bpf/bpf_endian.h>
12
13#define VERDICT_REJECT	0
14#define VERDICT_PROCEED	1
15
16int port;
17
18SEC("cgroup/connect4")
19int connect_v4_dropper(struct bpf_sock_addr *ctx)
20{
21	if (ctx->type != SOCK_STREAM)
22		return VERDICT_PROCEED;
23	if (ctx->user_port == bpf_htons(port))
24		return VERDICT_REJECT;
25	return VERDICT_PROCEED;
26}
27
28char _license[] SEC("license") = "GPL";