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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 "sd-daemon.h"
#include "alloc-util.h"
#include "creds-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "fs-util.h"
#include "hostname-setup.h"
#include "hostname-util.h"
#include "initrd-util.h"
#include "log.h"
#include "macro.h"
#include "proc-cmdline.h"
#include "string-table.h"
#include "string-util.h"
static int sethostname_idempotent_full(const char *s, bool really) {
struct utsname u;
assert(s);
if (uname(&u) < 0)
return -errno;
if (streq_ptr(s, u.nodename))
return 0;
if (really &&
sethostname(s, strlen(s)) < 0)
return -errno;
return 1;
}
int sethostname_idempotent(const char *s) {
return sethostname_idempotent_full(s, true);
}
int shorten_overlong(const char *s, char **ret) {
_cleanup_free_ char *h = NULL;
/* Shorten an overlong name to HOST_NAME_MAX or to the first dot,
* whatever comes earlier. */
assert(s);
assert(ret);
h = strdup(s);
if (!h)
return -ENOMEM;
if (hostname_is_valid(h, 0)) {
*ret = TAKE_PTR(h);
return 0;
}
char *p = strchr(h, '.');
if (p)
*p = 0;
strshorten(h, HOST_NAME_MAX);
if (!hostname_is_valid(h, /* flags= */ 0))
return -EDOM;
*ret = TAKE_PTR(h);
return 1;
}
static int acquire_hostname_from_credential(char **ret) {
_cleanup_free_ char *cred = NULL;
int r;
assert(ret);
r = read_credential_with_decryption("system.hostname", (void **) &cred, /* ret_size= */ NULL);
if (r < 0)
return log_warning_errno(r, "Failed to read system.hostname credential, ignoring: %m");
if (r == 0) /* not found */
return -ENXIO;
if (!hostname_is_valid(cred, VALID_HOSTNAME_TRAILING_DOT)) /* check that the hostname we return is valid */
return log_warning_errno(SYNTHETIC_ERRNO(EBADMSG), "Hostname specified in system.hostname credential is invalid, ignoring: %s", cred);
log_info("Initializing hostname from credential.");
*ret = TAKE_PTR(cred);
return 0;
}
int read_etc_hostname_stream(FILE *f, char **ret) {
int r;
assert(f);
assert(ret);
for (;;) {
_cleanup_free_ char *line = NULL;
r = read_stripped_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;
/* File may have empty lines or comments, ignore them */
if (IN_SET(line[0], '\0', '#'))
continue;
hostname_cleanup(line); /* normalize the hostname */
if (!hostname_is_valid(line, VALID_HOSTNAME_TRAILING_DOT)) /* check that the hostname we return is valid */
return -EBADMSG;
*ret = TAKE_PTR(line);
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);
}
void hostname_update_source_hint(const char *hostname, HostnameSource source) {
int r;
/* Why save the value and not just create a flag file? This way we will
* notice if somebody sets the hostname directly (not going through hostnamed).
*/
if (source == HOSTNAME_DEFAULT) {
r = write_string_file("/run/systemd/default-hostname", hostname,
WRITE_STRING_FILE_CREATE | WRITE_STRING_FILE_ATOMIC);
if (r < 0)
log_warning_errno(r, "Failed to create \"/run/systemd/default-hostname\", ignoring: %m");
} else
unlink_or_warn("/run/systemd/default-hostname");
}
int hostname_setup(bool really) {
_cleanup_free_ char *hn = NULL;
HostnameSource source;
bool enoent = false;
int r;
r = proc_cmdline_get_key("systemd.hostname", 0, &hn);
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(hn, VALID_HOSTNAME_TRAILING_DOT))
source = HOSTNAME_TRANSIENT;
else {
log_warning("Hostname specified on kernel command line is invalid, ignoring: %s", hn);
hn = mfree(hn);
}
}
if (!hn) {
r = read_etc_hostname(NULL, &hn);
if (r == -ENOENT)
enoent = true;
else if (r < 0)
log_warning_errno(r, "Failed to read configured hostname, ignoring: %m");
else
source = HOSTNAME_STATIC;
}
if (!hn) {
r = acquire_hostname_from_credential(&hn);
if (r >= 0)
source = HOSTNAME_TRANSIENT;
}
if (!hn) {
/* Don't override the hostname if it is already set and not explicitly configured */
r = gethostname_full(GET_HOSTNAME_ALLOW_LOCALHOST, &hn);
if (r == -ENOMEM)
return log_oom();
if (r >= 0) {
log_debug("No hostname configured, leaving existing hostname <%s> in place.", hn);
goto finish;
}
if (enoent)
log_info("No hostname configured, using default hostname.");
hn = get_default_hostname();
if (!hn)
return log_oom();
source = HOSTNAME_DEFAULT;
}
r = sethostname_idempotent_full(hn, really);
if (r < 0)
return log_warning_errno(r, "Failed to set hostname to <%s>: %m", hn);
if (r == 0)
log_debug("Hostname was already set to <%s>.", hn);
else
log_info("Hostname %s to <%s>.",
really ? "set" : "would have been set",
hn);
if (really)
hostname_update_source_hint(hn, source);
finish:
if (!in_initrd())
(void) sd_notifyf(/* unset_environment= */ false, "X_SYSTEMD_HOSTNAME=%s", hn);
return 0;
}
static const char* const hostname_source_table[] = {
[HOSTNAME_STATIC] = "static",
[HOSTNAME_TRANSIENT] = "transient",
[HOSTNAME_DEFAULT] = "default",
};
DEFINE_STRING_TABLE_LOOKUP(hostname_source, HostnameSource);
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