LXR busybox/libbb/safe

   1/* vi: set sw=4 ts=4: */
   2/*
   3 * Safe gethostname implementation for busybox
   4 *
   5 * Copyright (C) 2008 Tito Ragusa <farmatito@tiscali.it>
   6 *
   7 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   8 */
   9/*
  10 * SUSv2 guarantees that "Host names are limited to 255 bytes"
  11 * POSIX.1-2001 guarantees that "Host names (not including the terminating
  12 * null byte) are limited to HOST_NAME_MAX bytes" (64 bytes on my box).
  13 *
  14 * RFC1123 says:
  15 *
  16 * The syntax of a legal Internet host name was specified in RFC-952
  17 * [DNS:4].  One aspect of host name syntax is hereby changed: the
  18 * restriction on the first character is relaxed to allow either a
  19 * letter or a digit.  Host software MUST support this more liberal
  20 * syntax.
  21 *
  22 * Host software MUST handle host names of up to 63 characters and
  23 * SHOULD handle host names of up to 255 characters.
  24 */
  25#include "libbb.h"
  26#include <sys/utsname.h>
  27
  28/*
  29 * On success return the current malloced and NUL terminated hostname.
  30 * On error return malloced and NUL terminated string "?".
  31 * This is an illegal first character for a hostname.
  32 * The returned malloced string must be freed by the caller.
  33 */
  34char* FAST_FUNC safe_gethostname(void)
  35{
  36        struct utsname uts;
  37
  38        /* The length of the arrays in a struct utsname is unspecified;
  39         * the fields are terminated by a null byte.
  40         * Note that there is no standard that says that the hostname
  41         * set by sethostname(2) is the same string as the nodename field of the
  42         * struct returned by uname (indeed, some systems allow a 256-byte host-
  43         * name and an 8-byte nodename), but this is true on Linux. The same holds
  44         * for setdomainname(2) and the domainname field.
  45         */
  46
  47        /* Uname can fail only if you pass a bad pointer to it. */
  48        uname(&uts);
  49        return xstrndup(!uts.nodename[0] ? "?" : uts.nodename, sizeof(uts.nodename));
  50}
  51