mirror of
https://git.savannah.gnu.org/git/inetutils.git
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121 lines
3.0 KiB
C
121 lines
3.0 KiB
C
/* localhost.c - A slightly more convenient wrapper for gethostname
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Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
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2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015,
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2016, 2017 Free Software Foundation, Inc.
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This file is part of GNU Inetutils.
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GNU Inetutils is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or (at
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your option) any later version.
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GNU Inetutils 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, see `http://www.gnu.org/licenses/'. */
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/* Written by Miles Bader. */
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#include <config.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <string.h>
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#include <errno.h>
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <netdb.h>
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/* Return the name of the localhost. This is just a wrapper for gethostname,
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taking care of allocating a big enough buffer, and caching the result
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after the first call (so the result should be copied before modification).
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If something goes wrong, 0 is returned, and errno is set.
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*/
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/* We no longer use static buffers, as it is too dangerous and
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it causes subtile bugs. */
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char *
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localhost (void)
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{
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char *buf = NULL;
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size_t buf_len = 0;
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int status = 0;
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do
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{
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char *tmp;
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errno = 0;
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buf_len += 256; /* Initial guess */
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tmp = realloc (buf, buf_len);
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if (tmp == NULL)
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{
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errno = ENOMEM;
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free (buf);
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return 0;
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}
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else
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buf = tmp;
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}
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while (((status = gethostname (buf, buf_len)) == 0
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&& !memchr (buf, '\0', buf_len))
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#ifdef ENAMETOOLONG
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|| errno == ENAMETOOLONG
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#endif
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);
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if (status != 0 && errno != 0)
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/* gethostname failed, abort. */
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{
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free (buf);
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buf = 0;
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}
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else
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/* Determine FQDN. */
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{
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#if HAVE_DECL_GETADDRINFO
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int rc;
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struct addrinfo hints, *res;
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char fqdn[NI_MAXHOST];
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memset (&hints, 0, sizeof (hints));
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hints.ai_family = AF_INET;
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rc = getaddrinfo (buf, NULL, &hints, &res);
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if (!rc)
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{
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/* Back resolving as official host name. */
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rc = getnameinfo (res->ai_addr, res->ai_addrlen,
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fqdn, sizeof (fqdn), NULL, 0,
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NI_NAMEREQD);
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if (!rc)
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{
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free (buf);
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buf = strdup (fqdn);
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}
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freeaddrinfo (res);
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}
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#else /* !HAVE_DECL_GETADDRINFO */
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struct hostent *hp = gethostbyname (buf);
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if (hp)
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{
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struct in_addr addr;
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addr.s_addr = *(unsigned int *) hp->h_addr;
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hp = gethostbyaddr ((char *) &addr, sizeof (addr), AF_INET);
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if (hp)
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{
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free (buf);
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buf = strdup (hp->h_name);
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}
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}
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#endif /* !HAVE_DECL_GETADDRINFO */
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}
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return buf;
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}
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