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Diffstat (limited to 'src/libbasic/hostname-util.c')
| -rw-r--r-- | src/libbasic/hostname-util.c | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/src/libbasic/hostname-util.c b/src/libbasic/hostname-util.c new file mode 100644 index 0000000000..13c3bb6446 --- /dev/null +++ b/src/libbasic/hostname-util.c @@ -0,0 +1,252 @@ +/*** + 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; +} |