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/***
This file is part of systemd.
Copyright 2015 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>
#include <sys/utsname.h>
#include <unistd.h>
#include "fd-util.h"
#include "fileio.h"
#include "hostname-util.h"
#include "macro.h"
#include "string-util.h"
bool hostname_is_set(void) {
struct utsname u;
assert_se(uname(&u) >= 0);
if (isempty(u.nodename))
return false;
/* This is the built-in kernel default host name */
if (streq(u.nodename, "(none)"))
return false;
return true;
}
char* gethostname_malloc(void) {
struct utsname u;
/* This call tries to return something useful, either the actual hostname
* or it makes something up. The only reason it might fail is OOM.
* It might even return "localhost" if that's set. */
assert_se(uname(&u) >= 0);
if (isempty(u.nodename) || streq(u.nodename, "(none)"))
return strdup(u.sysname);
return strdup(u.nodename);
}
int gethostname_strict(char **ret) {
struct utsname u;
char *k;
/* This call will rather fail than make up a name. It will not return "localhost" either. */
assert_se(uname(&u) >= 0);
if (isempty(u.nodename))
return -ENXIO;
if (streq(u.nodename, "(none)"))
return -ENXIO;
if (is_localhost(u.nodename))
return -ENXIO;
k = strdup(u.nodename);
if (!k)
return -ENOMEM;
*ret = k;
return 0;
}
static bool hostname_valid_char(char c) {
return
(c >= 'a' && c <= 'z') ||
(c >= 'A' && c <= 'Z') ||
(c >= '0' && c <= '9') ||
c == '-' ||
c == '_' ||
c == '.';
}
/**
* Check if s looks like a valid host name or FQDN. This does not do
* full DNS validation, but only checks if the name is composed of
* allowed characters and the length is not above the maximum allowed
* by Linux (c.f. dns_name_is_valid()). Trailing dot is allowed if
* allow_trailing_dot is true and at least two components are present
* in the name. Note that due to the restricted charset and length
* this call is substantially more conservative than
* dns_name_is_valid().
*/
bool hostname_is_valid(const char *s, bool allow_trailing_dot) {
unsigned n_dots = 0;
const char *p;
bool dot;
if (isempty(s))
return false;
/* Doesn't accept empty hostnames, hostnames with
* leading dots, and hostnames with multiple dots in a
* sequence. Also ensures that the length stays below
* HOST_NAME_MAX. */
for (p = s, dot = true; *p; p++) {
if (*p == '.') {
if (dot)
return false;
dot = true;
n_dots++;
} else {
if (!hostname_valid_char(*p))
return false;
dot = false;
}
}
if (dot && (n_dots < 2 || !allow_trailing_dot))
return false;
if (p-s > HOST_NAME_MAX) /* Note that HOST_NAME_MAX is 64 on
* Linux, but DNS allows domain names
* up to 255 characters */
return false;
return true;
}
char* hostname_cleanup(char *s) {
char *p, *d;
bool dot;
assert(s);
strshorten(s, HOST_NAME_MAX);
for (p = s, d = s, dot = true; *p; p++) {
if (*p == '.') {
if (dot)
continue;
*(d++) = '.';
dot = true;
} else if (hostname_valid_char(*p)) {
*(d++) = *p;
dot = false;
}
}
if (dot && d > s)
d[-1] = 0;
else
*d = 0;
return s;
}
bool is_localhost(const char *hostname) {
assert(hostname);
/* This tries to identify local host and domain names
* described in RFC6761 plus the redhatism of localdomain */
return strcaseeq(hostname, "localhost") ||
strcaseeq(hostname, "localhost.") ||
strcaseeq(hostname, "localhost.localdomain") ||
strcaseeq(hostname, "localhost.localdomain.") ||
endswith_no_case(hostname, ".localhost") ||
endswith_no_case(hostname, ".localhost.") ||
endswith_no_case(hostname, ".localhost.localdomain") ||
endswith_no_case(hostname, ".localhost.localdomain.");
}
bool is_gateway_hostname(const char *hostname) {
assert(hostname);
/* This tries to identify the valid syntaxes for the our
* synthetic "gateway" host. */
return
strcaseeq(hostname, "gateway") ||
strcaseeq(hostname, "gateway.");
}
int sethostname_idempotent(const char *s) {
char buf[HOST_NAME_MAX + 1] = {};
assert(s);
if (gethostname(buf, sizeof(buf)) < 0)
return -errno;
if (streq(buf, s))
return 0;
if (sethostname(s, strlen(s)) < 0)
return -errno;
return 1;
}
int read_hostname_config(const char *path, char **hostname) {
_cleanup_fclose_ FILE *f = NULL;
char l[LINE_MAX];
char *name = NULL;
assert(path);
assert(hostname);
f = fopen(path, "re");
if (!f)
return -errno;
/* may have comments, ignore them */
FOREACH_LINE(l, f, return -errno) {
truncate_nl(l);
if (l[0] != '\0' && l[0] != '#') {
/* found line with value */
name = hostname_cleanup(l);
name = strdup(name);
if (!name)
return -ENOMEM;
break;
}
}
if (!name)
/* no non-empty line found */
return -ENOENT;
*hostname = name;
return 0;
}
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