diff options
Diffstat (limited to 'src/shared/hostname-setup.c')
| -rw-r--r-- | src/shared/hostname-setup.c | 236 |
1 files changed, 236 insertions, 0 deletions
diff --git a/src/shared/hostname-setup.c b/src/shared/hostname-setup.c new file mode 100644 index 0000000000..c0465d3dcd --- /dev/null +++ b/src/shared/hostname-setup.c @@ -0,0 +1,236 @@ +/* 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 "fs-util.h" +#include "hostname-setup.h" +#include "hostname-util.h" +#include "log.h" +#include "macro.h" +#include "proc-cmdline.h" +#include "string-table.h" +#include "string-util.h" +#include "util.h" + +static int sethostname_idempotent_full(const char *s, bool really) { + char buf[HOST_NAME_MAX + 1] = {}; + + assert(s); + + if (gethostname(buf, sizeof(buf) - 1) < 0) + return -errno; + + if (streq(buf, s)) + 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); +} + +bool get_hostname_filtered(char ret[static HOST_NAME_MAX + 1]) { + char buf[HOST_NAME_MAX + 1] = {}; + + /* Returns true if we got a good hostname, false otherwise. */ + + if (gethostname(buf, sizeof(buf) - 1) < 0) + return false; /* This can realistically only fail with ENAMETOOLONG. + * Let's treat that case the same as an invalid hostname. */ + + if (isempty(buf)) + return false; + + /* This is the built-in kernel default hostname */ + if (streq(buf, "(none)")) + return false; + + memcpy(ret, buf, sizeof buf); + return true; +} + +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); +} + +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_FALLBACK) { + r = write_string_file("/run/systemd/fallback-hostname", hostname, + WRITE_STRING_FILE_CREATE | WRITE_STRING_FILE_ATOMIC); + if (r < 0) + log_warning_errno(r, "Failed to create \"/run/systemd/fallback-hostname\": %m"); + } else + unlink_or_warn("/run/systemd/fallback-hostname"); +} + +int hostname_setup(bool really) { + _cleanup_free_ char *b = NULL; + const char *hn = NULL; + HostnameSource source; + 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; + source = HOSTNAME_TRANSIENT; + } 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; + source = HOSTNAME_STATIC; + } + } + + if (isempty(hn)) { + /* Don't override the hostname if it is already set and not explicitly configured */ + + char buf[HOST_NAME_MAX + 1] = {}; + if (get_hostname_filtered(buf)) { + log_debug("No hostname configured, leaving existing hostname <%s> in place.", buf); + return 0; + } + + if (enoent) + log_info("No hostname configured, using fallback hostname."); + + hn = FALLBACK_HOSTNAME; + source = HOSTNAME_FALLBACK; + + } + + 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); + + return r; +} + +static const char* const hostname_source_table[] = { + [HOSTNAME_STATIC] = "static", + [HOSTNAME_TRANSIENT] = "transient", + [HOSTNAME_FALLBACK] = "fallback", +}; + +DEFINE_STRING_TABLE_LOOKUP_TO_STRING(hostname_source, HostnameSource); |