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safe_gethostname.c 1.8 KB

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  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. * On success return the current malloced and NUL terminated hostname.
  29. * On error return malloced and NUL terminated string "?".
  30. * This is an illegal first character for a hostname.
  31. * The returned malloced string must be freed by the caller.
  32. */
  33. char* FAST_FUNC safe_gethostname(void)
  34. {
  35. struct utsname uts;
  36. /* The length of the arrays in a struct utsname is unspecified;
  37. * the fields are terminated by a null byte.
  38. * Note that there is no standard that says that the hostname
  39. * set by sethostname(2) is the same string as the nodename field of the
  40. * struct returned by uname (indeed, some systems allow a 256-byte host-
  41. * name and an 8-byte nodename), but this is true on Linux. The same holds
  42. * for setdomainname(2) and the domainname field.
  43. */
  44. /* Uname can fail only if you pass a bad pointer to it. */
  45. uname(&uts);
  46. return xstrndup(!uts.nodename[0] ? "?" : uts.nodename, sizeof(uts.nodename));
  47. }