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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/utsname.h>
#include <unistd.h>
#include "alloc-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "hostname-setup.h"
#include "hostname-util.h"
#include "log.h"
#include "macro.h"
#include "proc-cmdline.h"
#include "string-util.h"
#include "util.h"
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 shorten_overlong(const char *s, char **ret) {
char *h, *p;
/* Shorten an overlong name to HOST_NAME_MAX or to the first dot,
* whatever comes earlier. */
assert(s);
h = strdup(s);
if (!h)
return -ENOMEM;
if (hostname_is_valid(h, 0)) {
*ret = h;
return 0;
}
p = strchr(h, '.');
if (p)
*p = 0;
strshorten(h, HOST_NAME_MAX);
if (!hostname_is_valid(h, 0)) {
free(h);
return -EDOM;
}
*ret = h;
return 1;
}
int read_etc_hostname_stream(FILE *f, char **ret) {
int r;
assert(f);
assert(ret);
for (;;) {
_cleanup_free_ char *line = NULL;
char *p;
r = read_line(f, LONG_LINE_MAX, &line);
if (r < 0)
return r;
if (r == 0) /* EOF without any hostname? the file is empty, let's treat that exactly like no file at all: ENOENT */
return -ENOENT;
p = strstrip(line);
/* File may have empty lines or comments, ignore them */
if (!IN_SET(*p, '\0', '#')) {
char *copy;
hostname_cleanup(p); /* normalize the hostname */
if (!hostname_is_valid(p, VALID_HOSTNAME_TRAILING_DOT)) /* check that the hostname we return is valid */
return -EBADMSG;
copy = strdup(p);
if (!copy)
return -ENOMEM;
*ret = copy;
return 0;
}
}
}
int read_etc_hostname(const char *path, char **ret) {
_cleanup_fclose_ FILE *f = NULL;
assert(ret);
if (!path)
path = "/etc/hostname";
f = fopen(path, "re");
if (!f)
return -errno;
return read_etc_hostname_stream(f, ret);
}
static 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 hostname */
if (streq(u.nodename, "(none)"))
return false;
return true;
}
int hostname_setup(void) {
_cleanup_free_ char *b = NULL;
const char *hn = NULL;
bool enoent = false;
int r;
r = proc_cmdline_get_key("systemd.hostname", 0, &b);
if (r < 0)
log_warning_errno(r, "Failed to retrieve system hostname from kernel command line, ignoring: %m");
else if (r > 0) {
if (hostname_is_valid(b, true))
hn = b;
else {
log_warning("Hostname specified on kernel command line is invalid, ignoring: %s", b);
b = mfree(b);
}
}
if (!hn) {
r = read_etc_hostname(NULL, &b);
if (r < 0) {
if (r == -ENOENT)
enoent = true;
else
log_warning_errno(r, "Failed to read configured hostname: %m");
} else
hn = b;
}
if (isempty(hn)) {
/* Don't override the hostname if it is already set and not explicitly configured */
if (hostname_is_set())
return 0;
if (enoent)
log_info("No hostname configured.");
hn = FALLBACK_HOSTNAME;
}
r = sethostname_idempotent(hn);
if (r < 0)
return log_warning_errno(r, "Failed to set hostname to <%s>: %m", hn);
log_info("Set hostname to <%s>.", hn);
return 0;
}
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