// SPDX-License-Identifier: GPL-2.0 #include #include #include #include #include #include #include #include int main(int ac, char **argv) { struct sockaddr_in *serv_addr_in, *mapped_addr_in, *tmp_addr_in; struct sockaddr serv_addr, mapped_addr, tmp_addr; int serverfd, serverconnfd, clientfd, map_fd; struct bpf_link *link = NULL; struct bpf_program *prog; struct bpf_object *obj; socklen_t sockaddr_len; char filename[256]; char *ip; serv_addr_in = (struct sockaddr_in *)&serv_addr; mapped_addr_in = (struct sockaddr_in *)&mapped_addr; tmp_addr_in = (struct sockaddr_in *)&tmp_addr; snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]); obj = bpf_object__open_file(filename, NULL); if (libbpf_get_error(obj)) { fprintf(stderr, "ERROR: opening BPF object file failed\n"); return 0; } prog = bpf_object__find_program_by_name(obj, "bpf_prog1"); if (libbpf_get_error(prog)) { fprintf(stderr, "ERROR: finding a prog in obj file failed\n"); goto cleanup; } /* load BPF program */ if (bpf_object__load(obj)) { fprintf(stderr, "ERROR: loading BPF object file failed\n"); goto cleanup; } map_fd = bpf_object__find_map_fd_by_name(obj, "dnat_map"); if (map_fd < 0) { fprintf(stderr, "ERROR: finding a map in obj file failed\n"); goto cleanup; } link = bpf_program__attach(prog); if (libbpf_get_error(link)) { fprintf(stderr, "ERROR: bpf_program__attach failed\n"); link = NULL; goto cleanup; } assert((serverfd = socket(AF_INET, SOCK_STREAM, 0)) > 0); assert((clientfd = socket(AF_INET, SOCK_STREAM, 0)) > 0); /* Bind server to ephemeral port on lo */ memset(&serv_addr, 0, sizeof(serv_addr)); serv_addr_in->sin_family = AF_INET; serv_addr_in->sin_port = 0; serv_addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK); assert(bind(serverfd, &serv_addr, sizeof(serv_addr)) == 0); sockaddr_len = sizeof(serv_addr); assert(getsockname(serverfd, &serv_addr, &sockaddr_len) == 0); ip = inet_ntoa(serv_addr_in->sin_addr); printf("Server bound to: %s:%d\n", ip, ntohs(serv_addr_in->sin_port)); memset(&mapped_addr, 0, sizeof(mapped_addr)); mapped_addr_in->sin_family = AF_INET; mapped_addr_in->sin_port = htons(5555); mapped_addr_in->sin_addr.s_addr = inet_addr("255.255.255.255"); assert(!bpf_map_update_elem(map_fd, &mapped_addr, &serv_addr, BPF_ANY)); assert(listen(serverfd, 5) == 0); ip = inet_ntoa(mapped_addr_in->sin_addr); printf("Client connecting to: %s:%d\n", ip, ntohs(mapped_addr_in->sin_port)); assert(connect(clientfd, &mapped_addr, sizeof(mapped_addr)) == 0); sockaddr_len = sizeof(tmp_addr); ip = inet_ntoa(tmp_addr_in->sin_addr); assert((serverconnfd = accept(serverfd, &tmp_addr, &sockaddr_len)) > 0); printf("Server received connection from: %s:%d\n", ip, ntohs(tmp_addr_in->sin_port)); sockaddr_len = sizeof(tmp_addr); assert(getpeername(clientfd, &tmp_addr, &sockaddr_len) == 0); ip = inet_ntoa(tmp_addr_in->sin_addr); printf("Client's peer address: %s:%d\n", ip, ntohs(tmp_addr_in->sin_port)); /* Is the server's getsockname = the socket getpeername */ assert(memcmp(&serv_addr, &tmp_addr, sizeof(struct sockaddr_in)) == 0); cleanup: bpf_link__destroy(link); bpf_object__close(obj); return 0; }