1// SPDX-License-Identifier: GPL-2.0
2#include <stdio.h>
3#include <assert.h>
4#include <unistd.h>
5#include <bpf/bpf.h>
6#include <bpf/libbpf.h>
7#include <sys/socket.h>
8#include <netinet/in.h>
9#include <arpa/inet.h>
10
11int main(int ac, char **argv)
12{
13	struct sockaddr_in *serv_addr_in, *mapped_addr_in, *tmp_addr_in;
14	struct sockaddr serv_addr, mapped_addr, tmp_addr;
15	int serverfd, serverconnfd, clientfd, map_fd;
16	struct bpf_link *link = NULL;
17	struct bpf_program *prog;
18	struct bpf_object *obj;
19	socklen_t sockaddr_len;
20	char filename[256];
21	char *ip;
22
23	serv_addr_in = (struct sockaddr_in *)&serv_addr;
24	mapped_addr_in = (struct sockaddr_in *)&mapped_addr;
25	tmp_addr_in = (struct sockaddr_in *)&tmp_addr;
26
27	snprintf(filename, sizeof(filename), "%s.bpf.o", argv[0]);
28	obj = bpf_object__open_file(filename, NULL);
29	if (libbpf_get_error(obj)) {
30		fprintf(stderr, "ERROR: opening BPF object file failed\n");
31		return 0;
32	}
33
34	prog = bpf_object__find_program_by_name(obj, "bpf_prog1");
35	if (libbpf_get_error(prog)) {
36		fprintf(stderr, "ERROR: finding a prog in obj file failed\n");
37		goto cleanup;
38	}
39
40	/* load BPF program */
41	if (bpf_object__load(obj)) {
42		fprintf(stderr, "ERROR: loading BPF object file failed\n");
43		goto cleanup;
44	}
45
46	map_fd = bpf_object__find_map_fd_by_name(obj, "dnat_map");
47	if (map_fd < 0) {
48		fprintf(stderr, "ERROR: finding a map in obj file failed\n");
49		goto cleanup;
50	}
51
52	link = bpf_program__attach(prog);
53	if (libbpf_get_error(link)) {
54		fprintf(stderr, "ERROR: bpf_program__attach failed\n");
55		link = NULL;
56		goto cleanup;
57	}
58
59	assert((serverfd = socket(AF_INET, SOCK_STREAM, 0)) > 0);
60	assert((clientfd = socket(AF_INET, SOCK_STREAM, 0)) > 0);
61
62	/* Bind server to ephemeral port on lo */
63	memset(&serv_addr, 0, sizeof(serv_addr));
64	serv_addr_in->sin_family = AF_INET;
65	serv_addr_in->sin_port = 0;
66	serv_addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
67
68	assert(bind(serverfd, &serv_addr, sizeof(serv_addr)) == 0);
69
70	sockaddr_len = sizeof(serv_addr);
71	assert(getsockname(serverfd, &serv_addr, &sockaddr_len) == 0);
72	ip = inet_ntoa(serv_addr_in->sin_addr);
73	printf("Server bound to: %s:%d\n", ip, ntohs(serv_addr_in->sin_port));
74
75	memset(&mapped_addr, 0, sizeof(mapped_addr));
76	mapped_addr_in->sin_family = AF_INET;
77	mapped_addr_in->sin_port = htons(5555);
78	mapped_addr_in->sin_addr.s_addr = inet_addr("255.255.255.255");
79
80	assert(!bpf_map_update_elem(map_fd, &mapped_addr, &serv_addr, BPF_ANY));
81
82	assert(listen(serverfd, 5) == 0);
83
84	ip = inet_ntoa(mapped_addr_in->sin_addr);
85	printf("Client connecting to: %s:%d\n",
86	       ip, ntohs(mapped_addr_in->sin_port));
87	assert(connect(clientfd, &mapped_addr, sizeof(mapped_addr)) == 0);
88
89	sockaddr_len = sizeof(tmp_addr);
90	ip = inet_ntoa(tmp_addr_in->sin_addr);
91	assert((serverconnfd = accept(serverfd, &tmp_addr, &sockaddr_len)) > 0);
92	printf("Server received connection from: %s:%d\n",
93	       ip, ntohs(tmp_addr_in->sin_port));
94
95	sockaddr_len = sizeof(tmp_addr);
96	assert(getpeername(clientfd, &tmp_addr, &sockaddr_len) == 0);
97	ip = inet_ntoa(tmp_addr_in->sin_addr);
98	printf("Client's peer address: %s:%d\n",
99	       ip, ntohs(tmp_addr_in->sin_port));
100
101	/* Is the server's getsockname = the socket getpeername */
102	assert(memcmp(&serv_addr, &tmp_addr, sizeof(struct sockaddr_in)) == 0);
103
104cleanup:
105	bpf_link__destroy(link);
106	bpf_object__close(obj);
107	return 0;
108}
109