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 11 int 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); 103 104 cleanup: 105 bpf_link__destroy(link); 106 bpf_object__close(obj); 107 return 0; 108 } 109