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117 lines
3.0 KiB
C
117 lines
3.0 KiB
C
/* Host name canonicalization
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Copyright (C) 1995, 1999, 2000 Free Software Foundation, Inc.
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Written by Miles Bader <miles@gnu.ai.mit.edu>
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2, or (at
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your option) any later version.
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This program is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software Foundation,
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Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include <sys/types.h>
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#ifdef HAVE_UNISTD_H
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# include <unistd.h>
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#endif
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#ifdef HAVE_STDLIB_H
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# include <stdlib.h>
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#endif
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#ifdef HAVE_STRING_H
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# include <string.h>
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#endif
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#ifdef HAVE_NETDB_H
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# include <netdb.h>
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#endif
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#ifdef HAVE_SYS_SOCKET_H
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# include <sys/socket.h>
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#endif
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#ifdef HAVE_NETINET_IN_H
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# include <netinet/in.h>
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#endif
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#ifdef HAVE_ARPA_INET_H
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# include <arpa/inet.h>
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#endif
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#ifndef strdup
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char *strdup ();
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#endif
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/* Returns the canonical hostname associated with HOST (allocated in a static
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buffer), or 0 if it can't be determined. */
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char *
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canon_host (const char *host)
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{
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#ifdef HAVE_GETHOSTBYNAME
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struct hostent *he = gethostbyname (host);
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if (he)
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{
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# ifdef HAVE_GETHOSTBYADDR
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char *addr = 0;
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/* Try and get an ascii version of the numeric host address. */
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switch (he->h_addrtype)
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{
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# ifdef HAVE_INET_NTOA
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case AF_INET:
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addr = inet_ntoa (*(struct in_addr *) he->h_addr);
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break;
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# endif /* HAVE_INET_NTOA */
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}
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if (addr && strcmp (he->h_name, addr) == 0)
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{
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/* gethostbyname has returned a string representation of the IP
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address, for example, "127.0.0.1". So now, look up the host
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name via the address. Although it may seem reasonable to look
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up the host name via the address, we must not pass `he->h_addr'
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directly to gethostbyaddr because on some systems he->h_addr
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is located in a static library buffer that is reused in the
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gethostbyaddr call. Make a copy and use that instead. */
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char *h_addr_copy = (char *) malloc (he->h_length);
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if (h_addr_copy == NULL)
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he = NULL;
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else
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{
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memcpy (h_addr_copy, he->h_addr, he->h_length);
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he = gethostbyaddr (h_addr_copy, he->h_length, he->h_addrtype);
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free (h_addr_copy);
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}
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}
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# endif /* HAVE_GETHOSTBYADDR */
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if (he)
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return (char *) (he->h_name);
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}
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#endif /* HAVE_GETHOSTBYNAME */
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return 0;
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}
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#ifdef TEST_CANON_HOST
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int
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main (int argc, char **argv)
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{
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int i;
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for (i = 1; i < argc; i++)
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{
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char *s = canon_host (argv[i]);
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printf ("%s: %s\n", argv[i], (s ? s : "<undef>"));
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}
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exit (0);
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}
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#endif /* TEST_CANON_HOST */
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