1 /* Host name canonicalization
3 Copyright (C) 1995 Free Software Foundation, Inc.
5 Written by Miles Bader <miles@gnu.ai.mit.edu>
7 This program is free software; you can redistribute it and/or
8 modify it under the terms of the GNU General Public License as
9 published by the Free Software Foundation; either version 2, or (at
10 your option) any later version.
12 This program is distributed in the hope that it will be useful, but
13 WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
35 #ifdef HAVE_NETINET_IN_H
36 #include <netinet/in.h>
38 #ifdef HAVE_ARPA_INET_H
39 #include <arpa/inet.h>
42 /* Returns the canonical hostname associated with HOST (allocated in a static
43 buffer), or 0 if it can't be determined. */
48 #ifdef HAVE_GETHOSTBYNAME
49 struct hostent *he = gethostbyname (host);
53 #ifdef HAVE_GETHOSTBYADDR
56 /* Try and get an ascii version of the numeric host address. */
57 switch (he->h_addrtype)
61 addr = inet_ntoa (*(struct in_addr *) he->h_addr);
63 #endif /* HAVE_INET_NTOA */
66 if (addr && strcmp (he->h_name, addr) == 0)
67 /* gethostbyname() cheated! Lookup the host name via the address
68 this time to get the actual host name. */
69 he = gethostbyaddr (he->h_addr, he->h_length, he->h_addrtype);
70 #endif /* HAVE_GETHOSTBYADDR */
73 return (char *) (he->h_name);
75 #endif /* HAVE_GETHOSTBYNAME */