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}