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#include <stdint.h> /* uint16_t, uint32_t */
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#include <stddef.h> /* NULL, size_t, ssize_t */
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#include <stdlib.h> /* free(), EXIT_SUCCESS, EXIT_FAILURE,
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srand(), strtof(), abort() */
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#include <stdbool.h> /* bool, false, true */
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#include <string.h> /* memset(), strcmp(), strlen(),
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strerror(), asprintf(), strcpy() */
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INET_ADDRSTRLEN, INET6_ADDRSTRLEN
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#include <unistd.h> /* close(), SEEK_SET, off_t, write(),
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getuid(), getgid(), seteuid(),
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getuid(), getgid(), setuid(),
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#include <arpa/inet.h> /* inet_pton(), htons */
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#include <iso646.h> /* not, or, and */
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#include <argp.h> /* struct argp_option, error_t, struct
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#include <signal.h> /* sigemptyset(), sigaddset(),
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sigaction(), SIGTERM, sig_atomic_t,
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#include <sysexits.h> /* EX_OSERR, EX_USAGE */
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#include <sys/klog.h> /* klogctl() */
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.dh_bits = 1024, .priority = "SECURE256"
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":!CTYPE-X.509:+CTYPE-OPENPGP" };
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sig_atomic_t quit_now = 0;
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int signal_received = 0;
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* Make additional room in "buffer" for at least BUFFER_SIZE more
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* bytes. "buffer_capacity" is how much is currently allocated,
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static int init_gnutls_session(gnutls_session_t *session){
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/* GnuTLS session creation */
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ret = gnutls_init(session, GNUTLS_SERVER);
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} while(ret == GNUTLS_E_INTERRUPTED or ret == GNUTLS_E_AGAIN);
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ret = gnutls_init(session, GNUTLS_SERVER);
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if(ret != GNUTLS_E_SUCCESS){
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fprintf(stderr, "Error in GnuTLS session initialization: %s\n",
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safer_gnutls_strerror(ret));
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ret = gnutls_priority_set_direct(*session, mc.priority, &err);
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gnutls_deinit(*session);
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} while(ret == GNUTLS_E_INTERRUPTED or ret == GNUTLS_E_AGAIN);
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ret = gnutls_priority_set_direct(*session, mc.priority, &err);
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if(ret != GNUTLS_E_SUCCESS){
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fprintf(stderr, "Syntax error at: %s\n", err);
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fprintf(stderr, "GnuTLS error: %s\n",
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ret = gnutls_credentials_set(*session, GNUTLS_CRD_CERTIFICATE,
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gnutls_deinit(*session);
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} while(ret == GNUTLS_E_INTERRUPTED or ret == GNUTLS_E_AGAIN);
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ret = gnutls_credentials_set(*session, GNUTLS_CRD_CERTIFICATE,
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if(ret != GNUTLS_E_SUCCESS){
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fprintf(stderr, "Error setting GnuTLS credentials: %s\n",
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safer_gnutls_strerror(ret));
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/* ignore client certificate if any. */
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gnutls_certificate_server_set_request(*session, GNUTLS_CERT_IGNORE);
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gnutls_certificate_server_set_request(*session,
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gnutls_dh_set_prime_bits(*session, mc.dh_bits);
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static void empty_log(__attribute__((unused)) AvahiLogLevel level,
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__attribute__((unused)) const char *txt){}
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sig_atomic_t quit_now = 0;
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int signal_received = 0;
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/* Called when a Mandos server is found */
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static int start_mandos_communication(const char *ip, uint16_t port,
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AvahiIfIndex if_index,
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int ret, tcp_sd = -1;
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struct sockaddr_in in;
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struct sockaddr_in6 in6;
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char *buffer = NULL;
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char *decrypted_buffer = NULL;
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char *decrypted_buffer;
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size_t buffer_length = 0;
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size_t buffer_capacity = 0;
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ssize_t decrypted_buffer_size;
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gnutls_session_t session;
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int pf; /* Protocol family */
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if(if_index == AVAHI_IF_UNSPEC){
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fprintf(stderr, "An IPv6 link-local address is incomplete"
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" without a network interface\n");
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/* Set the network interface number as scope */
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to.in6.sin6_scope_id = (uint32_t)if_index;
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fprintf(stderr, "Establishing TLS session with %s\n", ip);
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gnutls_transport_set_ptr(session, (gnutls_transport_ptr_t) tcp_sd);
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ret = gnutls_handshake(session);
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} while(ret == GNUTLS_E_AGAIN or ret == GNUTLS_E_INTERRUPTED);
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if(ret != GNUTLS_E_SUCCESS){
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case GNUTLS_E_AGAIN:
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case GNUTLS_E_REHANDSHAKE:
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ret = gnutls_handshake(session);
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} while(ret == GNUTLS_E_AGAIN or ret == GNUTLS_E_INTERRUPTED);
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fprintf(stderr, "*** GnuTLS Re-handshake failed ***\n");
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gnutls_perror(ret);
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fprintf(stderr, "Unknown error while reading data from"
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" encrypted session with Mandos server\n");
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gnutls_bye(session, GNUTLS_SHUT_RDWR);
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fprintf(stderr, "Closing TLS session\n");
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ret = gnutls_bye(session, GNUTLS_SHUT_RDWR);
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} while(ret == GNUTLS_E_AGAIN or ret == GNUTLS_E_INTERRUPTED);
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gnutls_bye(session, GNUTLS_SHUT_RDWR);
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if(buffer_length > 0){
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ssize_t decrypted_buffer_size;
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decrypted_buffer_size = pgp_packet_decrypt(buffer,
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&decrypted_buffer);
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if(decrypted_buffer_size >= 0){
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while(written < (size_t) decrypted_buffer_size){
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ret = (int)fwrite(decrypted_buffer + written, 1,
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(size_t)decrypted_buffer_size - written,
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bool gpgme_initialized = false;
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float delay = 2.5f;
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struct sigaction old_sigterm_action = { .sa_handler = SIG_DFL };
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struct sigaction old_sigterm_action;
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struct sigaction sigterm_action = { .sa_handler = handle_sigterm };
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/* Lower any group privileges we might have, just to be safe */
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/* Lower user privileges (temporarily) */
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struct argp_option options[] = {
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{ .name = "debug", .key = 128,
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.arg = "SECONDS",
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.doc = "Maximum delay to wait for interface startup",
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* These reproduce what we would get without ARGP_NO_HELP
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{ .name = "help", .key = '?',
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.doc = "Give this help list", .group = -1 },
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{ .name = "usage", .key = -3,
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.doc = "Give a short usage message", .group = -1 },
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{ .name = "version", .key = 'V',
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.doc = "Print program version", .group = -1 },
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{ .name = NULL }
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error_t parse_opt(int key, char *arg,
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struct argp_state *state){
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case 128: /* --debug */
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tmpmax = strtoimax(arg, &tmp, 10);
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if(errno != 0 or tmp == arg or *tmp != '\0'
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or tmpmax != (typeof(mc.dh_bits))tmpmax){
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argp_error(state, "Bad number of DH bits");
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fprintf(stderr, "Bad number of DH bits\n");
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mc.dh_bits = (typeof(mc.dh_bits))tmpmax;
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delay = strtof(arg, &tmp);
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if(errno != 0 or tmp == arg or *tmp != '\0'){
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argp_error(state, "Bad delay");
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fprintf(stderr, "Bad delay\n");
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* These reproduce what we would get without ARGP_NO_HELP
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case '?': /* --help */
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argp_state_help(state, state->out_stream,
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(ARGP_HELP_STD_HELP | ARGP_HELP_EXIT_ERR)
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& ~(unsigned int)ARGP_HELP_EXIT_OK);
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case -3: /* --usage */
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argp_state_help(state, state->out_stream,
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ARGP_HELP_USAGE | ARGP_HELP_EXIT_ERR);
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case 'V': /* --version */
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fprintf(state->out_stream, "%s\n", argp_program_version);
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exit(argp_err_exit_status);
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return ARGP_ERR_UNKNOWN;
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struct argp argp = { .options = options, .parser = parse_opt,
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.args_doc = "",
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.doc = "Mandos client -- Get and decrypt"
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" passwords from a Mandos server" };
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ret = argp_parse(&argp, argc, argv,
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ARGP_IN_ORDER | ARGP_NO_HELP, 0, NULL);
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perror("argp_parse");
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exitcode = EX_OSERR;
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exitcode = EX_USAGE;
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ret = argp_parse(&argp, argc, argv, 0, 0, NULL);
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if(ret == ARGP_ERR_UNKNOWN){
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fprintf(stderr, "Unknown error while parsing arguments\n");
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exitcode = EXIT_FAILURE;
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/* Re-raise priviliges */
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#ifdef __linux__
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/* Lower kernel loglevel to KERN_NOTICE to avoid KERN_INFO
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messages about the network interface to mess up the prompt */
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messages to mess up the prompt */
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ret = klogctl(8, NULL, 5);
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bool restore_loglevel = true;
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/* Take down the network interface */
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if(take_down_interface){
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/* Re-raise priviliges */
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ret = ioctl(sd, SIOCGIFFLAGS, &network);
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perror("ioctl SIOCGIFFLAGS");
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} else if(network.ifr_flags & IFF_UP) {
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network.ifr_flags &= ~IFF_UP; /* clear flag */
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ret = ioctl(sd, SIOCSIFFLAGS, &network);
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perror("ioctl SIOCSIFFLAGS");
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ret = ioctl(sd, SIOCGIFFLAGS, &network);
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perror("ioctl SIOCGIFFLAGS");
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} else if(network.ifr_flags & IFF_UP) {
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network.ifr_flags &= ~(short)IFF_UP; /* clear flag */
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ret = ioctl(sd, SIOCSIFFLAGS, &network);
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perror("ioctl SIOCSIFFLAGS");
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ret = (int)TEMP_FAILURE_RETRY(close(sd));
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/* Lower privileges permanently */
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ret = (int)TEMP_FAILURE_RETRY(close(sd));
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sigemptyset(&old_sigterm_action.sa_mask);
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old_sigterm_action.sa_handler = SIG_DFL;
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ret = (int)TEMP_FAILURE_RETRY(sigaction(signal_received,
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&old_sigterm_action,
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ret = sigaction(signal_received, &old_sigterm_action, NULL);
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perror("sigaction");
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ret = raise(signal_received);
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} while(ret != 0 and errno == EINTR);
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TEMP_FAILURE_RETRY(pause());
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raise(signal_received);
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return exitcode;