mirror of
https://git.savannah.gnu.org/git/inetutils.git
synced 2026-01-12 00:19:39 +08:00
119 lines
2.9 KiB
C
119 lines
2.9 KiB
C
/* localhost.c - A slightly more convenient wrapper for gethostname
|
|
Copyright (C) 1996-2022 Free Software Foundation, Inc.
|
|
|
|
This file is part of GNU Inetutils.
|
|
|
|
GNU Inetutils is free software: you can redistribute it and/or modify
|
|
it under the terms of the GNU General Public License as published by
|
|
the Free Software Foundation, either version 3 of the License, or (at
|
|
your option) any later version.
|
|
|
|
GNU Inetutils is distributed in the hope that it will be useful, but
|
|
WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with this program. If not, see `http://www.gnu.org/licenses/'. */
|
|
|
|
/* Written by Miles Bader. */
|
|
|
|
#include <config.h>
|
|
|
|
#include <unistd.h>
|
|
#include <stdlib.h>
|
|
#include <stdint.h>
|
|
#include <string.h>
|
|
#include <errno.h>
|
|
#include <sys/types.h>
|
|
#include <sys/socket.h>
|
|
#include <netinet/in.h>
|
|
#include <netdb.h>
|
|
|
|
/* Return the name of the localhost. This is just a wrapper for gethostname,
|
|
taking care of allocating a big enough buffer, and caching the result
|
|
after the first call (so the result should be copied before modification).
|
|
If something goes wrong, 0 is returned, and errno is set.
|
|
*/
|
|
/* We no longer use static buffers, as it is too dangerous and
|
|
it causes subtile bugs. */
|
|
char *
|
|
localhost (void)
|
|
{
|
|
char *buf = NULL;
|
|
size_t buf_len = 0;
|
|
int status = 0;
|
|
|
|
do
|
|
{
|
|
char *tmp;
|
|
errno = 0;
|
|
|
|
buf_len += 256; /* Initial guess */
|
|
tmp = realloc (buf, buf_len);
|
|
if (tmp == NULL)
|
|
{
|
|
errno = ENOMEM;
|
|
free (buf);
|
|
return 0;
|
|
}
|
|
else
|
|
buf = tmp;
|
|
}
|
|
while (((status = gethostname (buf, buf_len)) == 0
|
|
&& !memchr (buf, '\0', buf_len))
|
|
#ifdef ENAMETOOLONG
|
|
|| errno == ENAMETOOLONG
|
|
#endif
|
|
);
|
|
|
|
if (status != 0 && errno != 0)
|
|
/* gethostname failed, abort. */
|
|
{
|
|
free (buf);
|
|
buf = 0;
|
|
}
|
|
else
|
|
/* Determine FQDN. */
|
|
{
|
|
#if HAVE_DECL_GETADDRINFO
|
|
int rc;
|
|
struct addrinfo hints, *res;
|
|
char fqdn[NI_MAXHOST];
|
|
|
|
memset (&hints, 0, sizeof (hints));
|
|
hints.ai_family = AF_INET;
|
|
|
|
rc = getaddrinfo (buf, NULL, &hints, &res);
|
|
if (!rc)
|
|
{
|
|
/* Back resolving as official host name. */
|
|
rc = getnameinfo (res->ai_addr, res->ai_addrlen,
|
|
fqdn, sizeof (fqdn), NULL, 0,
|
|
NI_NAMEREQD);
|
|
if (!rc)
|
|
{
|
|
free (buf);
|
|
buf = strdup (fqdn);
|
|
}
|
|
freeaddrinfo (res);
|
|
}
|
|
#else /* !HAVE_DECL_GETADDRINFO */
|
|
struct hostent *hp = gethostbyname (buf);
|
|
|
|
if (hp)
|
|
{
|
|
struct in_addr addr;
|
|
addr.s_addr = *(unsigned int *) hp->h_addr;
|
|
hp = gethostbyaddr ((char *) &addr, sizeof (addr), AF_INET);
|
|
if (hp)
|
|
{
|
|
free (buf);
|
|
buf = strdup (hp->h_name);
|
|
}
|
|
}
|
|
#endif /* !HAVE_DECL_GETADDRINFO */
|
|
}
|
|
return buf;
|
|
}
|