external/ibm-public/postfix/dist/src/util/get_hostname.c

   1 /*      $NetBSD$        */
   2
   3 /*++
   4 /* NAME
   5 /*      get_hostname 3
   6 /* SUMMARY
   7 /*      network name lookup
   8 /* SYNOPSIS
   9 /*      #include <get_hostname.h>
  10 /*
  11 /*      const char *get_hostname()
  12 /* DESCRIPTION
  13 /*      get_hostname() returns the local hostname as obtained
  14 /*      via gethostname() or its moral equivalent. This routine
  15 /*      goes to great length to avoid dependencies on any network
  16 /*      services.
  17 /* DIAGNOSTICS
  18 /*      Fatal errors: no hostname, invalid hostname.
  19 /* SEE ALSO
  20 /*      valid_hostname(3)
  21 /* LICENSE
  22 /* .ad
  23 /* .fi
  24 /*      The Secure Mailer license must be distributed with this software.
  25 /* AUTHOR(S)
  26 /*      Wietse Venema
  27 /*      IBM T.J. Watson Research
  28 /*      P.O. Box 704
  29 /*      Yorktown Heights, NY 10598, USA
  30 /*--*/
  31
  32 /* System library. */
  33
  34 #include <sys_defs.h>
  35 #include <sys/param.h>
  36 #include <string.h>
  37 #include <unistd.h>
  38
  39 #if (MAXHOSTNAMELEN < 256)
  40 #undef MAXHOSTNAMELEN
  41 #define MAXHOSTNAMELEN  256
  42 #endif
  43
  44 /* Utility library. */
  45
  46 #include "mymalloc.h"
  47 #include "msg.h"
  48 #include "valid_hostname.h"
  49 #include "get_hostname.h"
  50
  51 /* Local stuff. */
  52
  53 static char *my_host_name;
  54
  55 /* get_hostname - look up my host name */
  56
  57 const char *get_hostname(void)
  58 {
  59     char    namebuf[MAXHOSTNAMELEN + 1];
  60
  61     /*
  62      * The gethostname() call is not (or not yet) in ANSI or POSIX, but it is
  63      * part of the socket interface library. We avoid the more politically-
  64      * correct uname() routine because that has no portable way of dealing
  65      * with long (FQDN) hostnames.
  66      *
  67      * DO NOT CALL GETHOSTBYNAME FROM THIS FUNCTION. IT BREAKS MAILDIR DELIVERY
  68      * AND OTHER THINGS WHEN THE MACHINE NAME IS NOT FOUND IN /ETC/HOSTS OR
  69      * CAUSES PROCESSES TO HANG WHEN THE NETWORK IS DISCONNECTED.
  70      *
  71      * POSTFIX NO LONGER NEEDS A FULLY QUALIFIED HOSTNAME. INSTEAD POSTFIX WILL
  72      * USE A DEFAULT DOMAIN NAME "LOCALDOMAIN".
  73      */
  74     if (my_host_name == 0) {
  75         /* DO NOT CALL GETHOSTBYNAME FROM THIS FUNCTION */
  76         if (gethostname(namebuf, sizeof(namebuf)) < 0)
  77             msg_fatal("gethostname: %m");
  78         namebuf[MAXHOSTNAMELEN] = 0;
  79         /* DO NOT CALL GETHOSTBYNAME FROM THIS FUNCTION */
  80         if (valid_hostname(namebuf, DO_GRIPE) == 0)
  81             msg_fatal("unable to use my own hostname");
  82         /* DO NOT CALL GETHOSTBYNAME FROM THIS FUNCTION */
  83         my_host_name = mystrdup(namebuf);
  84     }
  85     return (my_host_name);
  86 }