1
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_kern.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
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
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
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
