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/*
* hostname This file contains an implementation of the command
* that maintains the host name and the domain name. It
* is also used to show the FQDN and the IP-Addresses.
*
* Usage: hostname [-a|-A|-d|-f|-i|-I|-s|-y]
* hostname [-h|-V]
* hostname [-b] {name|-F file}
* dnsdomainname
* domainname
* ypdomainname
* nisdomainname
*
* Authors: Peter Tobias <tobias@et-inf.fho-emden.de>
* Bernd Eckenfels
* Graham Wilson <graham@debian.org>
* Michael Meskes <meskes@debian.org>
*
* This program is free software; you can redistribute it
* and/or modify it under the terms of the GNU General
* Public License as published by the Free Software
* Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* The localdomain and localhost functions are copyright
* (C) 1996 Free Software Foundation, Inc. and were
* written by Miles Bader <miles@gnu.ai.mit.edu> and
* Marcus Brinkmann <brinkmd@debian.org>.
*/
#include <sys/stat.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <ifaddrs.h>
#include <net/if.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <getopt.h>
#include <string.h>
#include <netdb.h>
#include <errno.h>
#include <ctype.h>
#include <err.h>
#define VERSION "3.18"
enum type_t { DEFAULT, DNS, FQDN, SHORT, ALIAS, IP, NIS, NIS_DEF, ALL_FQDNS, ALL_IPS };
char *progname;
/*
* Return the name of the nis default domain. Same as localdomain below,
* but reports failure for unset domain.
*/
char *
localnisdomain()
{
/* The historical NIS limit is 1024, the limit on Linux is 64. */
static char buf[1025];
int myerror = 0;
myerror = getdomainname(buf, sizeof buf);
if (myerror || strcmp(buf, "(none)") == 0) {
printf("%s: Local domain name not set\n", progname);
exit (1);
}
return buf;
}
/*
* Return the name of the localdomain. This is just a wrapper for
* getdomainname, which takes care of allocating a big enough buffer, and
* caches the result after the first call (so the result should be copied
* before modification). If something goes wrong, program exits.
*/
char *
localdomain()
{
char *buf = 0;
size_t buf_len = 0;
int myerror = 0;
do {
errno = 0;
if (buf) {
buf_len += buf_len;
if ((buf = realloc (buf, buf_len)) == NULL)
err(1, NULL);
} else {
buf_len = 128; /* Initial guess */
if ((buf = malloc (buf_len)) == NULL)
err(1, NULL);
}
} while (((myerror = getdomainname(buf, buf_len)) == 0 && !memchr (buf, '\0', buf_len))
|| errno == ENAMETOOLONG);
/* getdomainname failed, abort. */
if (myerror)
err(1, NULL);
return buf;
}
/*
* Return the name of the localhost. This is just a wrapper for gethostname,
* which takes care of allocating a big enough buffer, and caches the result
* after the first call (so the result should be copied before modification).
* If something goes wrong, program exits.
*/
char *
localhost()
{
char *buf = 0;
size_t buf_len = 0;
int myerror = 0;
do {
errno = 0;
if (buf) {
buf_len += buf_len;
if ((buf = realloc (buf, buf_len)) == NULL)
err(1, NULL);
} else {
buf_len = 128; /* Initial guess */
if ((buf = malloc (buf_len)) == NULL)
err(1, NULL);
}
} while (((myerror = gethostname(buf, buf_len)) == 0 && !memchr (buf, '\0', buf_len))
|| errno == ENAMETOOLONG);
/* gethostname failed, abort. */
if (myerror)
err(1, NULL);
return buf;
}
void
usage(FILE *stream)
{
fprintf(stream,
"Usage: hostname [-b] {hostname|-F file} set host name (from file)\n"
" hostname [-a|-A|-d|-f|-i|-I|-s|-y] display formatted name\n"
" hostname display host name\n"
"\n"
" {yp,nis,}domainname {nisdomain|-F file} set NIS domain name (from file)\n"
" {yp,nis,}domainname display NIS domain name\n"
"\n"
" dnsdomainname display dns domain name\n"
"\n"
" hostname -V|--version|-h|--help print info and exit\n"
"\n"
"Program name:\n"
" {yp,nis,}domainname=hostname -y\n"
" dnsdomainname=hostname -d\n"
"\n"
"Program options:\n"
" -a, --alias alias names\n"
" -A, --all-fqdns all long host names (FQDNs)\n"
" -b, --boot set default hostname if none available\n"
" -d, --domain DNS domain name\n"
" -f, --fqdn, --long long host name (FQDN)\n"
" -F, --file read host name or NIS domain name from given file\n"
" -i, --ip-address addresses for the host name\n"
" -I, --all-ip-addresses all addresses for the host\n"
" -s, --short short host name\n"
" -y, --yp, --nis NIS/YP domain name\n"
"\n"
"Description:\n"
" This command can get or set the host name or the NIS domain name. You can\n"
" also get the DNS domain or the FQDN (fully qualified domain name).\n"
" Unless you are using bind or NIS for host lookups you can change the\n"
" FQDN (Fully Qualified Domain Name) and the DNS domain name (which is\n"
" part of the FQDN) in the /etc/hosts file.\n");
exit(-1);
}
/*
* Check the format of a user-specified hostname. Uses the rules from RFC 1035,
* section 2.3.1.
*/
int
check_name(char *name)
{
int i, len = strlen(name);
/* Handle leading and trailing hyphen now. */
if (!len || !isalnum(name[0]) || !isalnum(name[len-1]))
return 0;
for (i = 0; i < len; i++) {
if (!isalnum(name[i]) && name[i] != '-' && name[i] != '.')
return 0;
if (name[i] == '-' && (name[i - 1] == '.' || name[i + 1] == '.'))
return 0;
if (name[i] == '.' && name[i - 1] == '.')
return 0;
}
return 1;
}
void
set_name(enum type_t type, char *name)
{
int i;
switch (type) {
case DEFAULT:
/* Whitespaces are invalid characters in a hostname. */
/* Thus remove trailing and leading whitespaces. */
while (isspace(*name)) { name++; }
for (i = strlen(name) - 1; i >= 0 && isspace(name[i]); i--);
name[i+1] = '\0';
/* Now check for a valid name. */
if (!check_name(name))
errx(1, "the specified hostname is invalid");
if (sethostname(name, strlen(name))) {
if (errno == EPERM)
errx(1, "you must be root to change the host name");
else if (errno == EINVAL)
errx(1, "name too long");
}
break;
case NIS:
case NIS_DEF:
if (setdomainname(name, strlen(name))) {
if (errno == EPERM)
errx(1, "you must be root to change the domain name");
else if (errno == EINVAL)
errx(1, "name too long");
}
break;
default:
/*
* Only the host name and the domain name can be set using this
* command.
*/
usage(stderr);
}
}
void
show_name(enum type_t type)
{
struct addrinfo *res;
struct addrinfo hints;
struct ifaddrs *ifa, *ifap;
char *p;
int ret;
/* Handle a few cases specially. */
switch(type)
{
case DEFAULT:
printf("%s\n", localhost());
break;
case SHORT:
p = localhost();
*(strchrnul(p, '.')) = '\0';
printf("%s\n", p);
break;
case NIS:
printf("%s\n", localdomain());
break;
case NIS_DEF:
printf("%s\n", localnisdomain());
break;
case ALL_IPS:
case ALL_FQDNS: {
char buf[255];
int flags, ret, family, addrlen;
/* What kind of information do we want from getnameinfo()? */
flags = (type == ALL_IPS) ? NI_NUMERICHOST : NI_NAMEREQD;
if (getifaddrs(&ifa) != 0)
errx(1, "%s", strerror(errno));
for (ifap = ifa; ifap != NULL; ifap = ifap->ifa_next) {
/* Skip interfaces that have no configured addresses */
if (ifap->ifa_addr == NULL)
continue;
/* Skip the loopback interface */
if (ifap->ifa_flags & IFF_LOOPBACK)
continue;
/* Skip interfaces that are not UP */
if (!(ifap->ifa_flags & IFF_UP))
continue;
/* Only handle IPv4 and IPv6 addresses */
family = ifap->ifa_addr->sa_family;
if (family != AF_INET && family != AF_INET6)
continue;
addrlen = (family == AF_INET) ? sizeof(struct sockaddr_in) :
sizeof(struct sockaddr_in6);
/* Skip IPv6 link-local addresses */
if (family == AF_INET6) {
struct sockaddr_in6 *sin6;
sin6 = (struct sockaddr_in6 *)ifap->ifa_addr;
if (IN6_IS_ADDR_LINKLOCAL(&sin6->sin6_addr) ||
IN6_IS_ADDR_MC_LINKLOCAL(&sin6->sin6_addr))
continue;
}
ret = getnameinfo(ifap->ifa_addr, addrlen,
buf, sizeof(buf), NULL, 0, flags);
/* Just skip addresses that cannot be translated */
if (ret != 0) {
if (type != ALL_FQDNS && ret != EAI_NONAME)
errx(1, "%s", gai_strerror(ret));
} else
printf("%s ", buf);
}
printf("\n");
freeifaddrs(ifa);
break;
}
default:
memset(&hints, 0, sizeof(struct addrinfo));
hints.ai_socktype = SOCK_DGRAM;
hints.ai_flags = AI_CANONNAME;
p = localhost();
if ((ret = getaddrinfo(p, NULL, &hints, &res)) != 0)
errx(1, "%s", gai_strerror(ret));
p = strchr(res->ai_canonname, '.');
switch (type) {
case ALIAS: {
struct hostent *hp;
int i;
if ((hp = gethostbyname(localhost())) == NULL)
errx(1, "%s", hstrerror(h_errno));
for (i = 0; hp->h_aliases[i]; i++) {
if (i > 0)
printf(" ");
printf("%s", hp->h_aliases[i]);
}
printf("\n");
break;
}
case IP: {
char buf[INET6_ADDRSTRLEN];
int ret;
struct addrinfo *walk;
for (walk = res; walk != NULL; walk = walk->ai_next) {
if ((ret = getnameinfo(walk->ai_addr, walk->ai_addrlen,
buf, sizeof(buf), NULL, 0,
NI_NUMERICHOST)) != 0)
errx(1, "%s", gai_strerror(ret));
if (walk != res)
printf(" ");
printf("%s", buf);
}
printf("\n");
break;
}
case DNS:
if (p != NULL)
printf("%s\n", ++p);
break;
case FQDN:
printf("%s\n", res->ai_canonname);
break;
default:
break;
}
break;
}
}
char *
read_file(char *filename, int boot)
{
struct stat st;
FILE *fp;
char *buf;
if ((fp = fopen(filename, "r")) == NULL) {
if (boot)
return NULL;
else
err(1, NULL);
}
if (fstat(fileno(fp), &st) == -1
|| (buf = (char *) calloc(st.st_size + 1, sizeof(char))) == NULL)
err(1, NULL);
while (fgets(buf, st.st_size + 1, fp) != NULL) {
char *p;
if (buf[0] == '\n' || buf[0] == '#')
continue;
if ((p = strchr(buf, '\n')) != NULL)
*p = '\0';
break;
}
fclose(fp);
return buf;
}
int
main(int argc, char **argv)
{
char *file = NULL, *name = NULL;
enum type_t type = DEFAULT;
int boot = 0;
int o;
static const struct option long_options[] =
{
{"domain", no_argument, 0, 'd'},
{"boot", no_argument, 0, 'b'},
{"file", required_argument, 0, 'F'},
{"fqdn", no_argument, 0, 'f'},
{"all-fqdns", no_argument, 0, 'A'},
{"help", no_argument, 0, 'h'},
{"long", no_argument, 0, 'f'},
{"short", no_argument, 0, 's'},
{"version", no_argument, 0, 'V'},
{"alias", no_argument, 0, 'a'},
{"ip-address", no_argument, 0, 'i'},
{"all-ip-addresses", no_argument, 0, 'I'},
{"nis", no_argument, 0, 'y'},
{"yp", no_argument, 0, 'y'},
{0, 0, 0, 0}
};
/* If called as 'dnsdomainname', by default show the DNS domain name. */
progname = (rindex(argv[0], '/')) ? rindex(argv[0], '/') + 1 : argv[0];
if (!strcmp(progname, "dnsdomainname"))
type = DNS;
else if (!strcmp(progname, "domainname"))
type = NIS;
else if (!strcmp(progname, "ypdomainname"))
type = NIS_DEF;
else if (!strcmp(progname, "nisdomainname"))
type = NIS_DEF;
while((o = getopt_long(argc, argv, "aAdfbF:h?iIsVy", long_options, NULL)) != -1)
switch (o) {
case 'd':
type = DNS;
break;
case 'a':
type = ALIAS;
break;
case 'f':
type = FQDN;
break;
case 'A':
type = ALL_FQDNS;
break;
case 'i':
type = IP;
break;
case 'I':
type = ALL_IPS;
break;
case 's':
type = SHORT;
break;
case 'y':
type = NIS_DEF;
break;
case 'b':
boot = 1;
break;
case 'F':
file = optarg;
break;
case 'V':
printf("hostname %s\n", VERSION);
return 0;
case '?':
case 'h':
usage(stdout);
break;
default:
usage(stderr);
}
/*
* Hostname may be read from a file, it's ok for this file to not
* exist or be empty if -b is given in which case we default to
* "localhost" if there is not one already set.
*/
if (file) {
name = read_file(file, boot);
if (boot && (name == NULL || name[0] == '\0')) {
free(name);
name = localhost();
if (name[0] == '\0' || !strcmp(name,"(none)"))
strcpy(name, "localhost");
}
}
/* Otherwise the hostname is the first non-option argument. */
if (optind < argc) {
/*
* It is an error to specify a host name as an argument, and to
* be read from a file.
*/
if (name)
usage(stderr);
if ((name = strdup(argv[optind])) == NULL)
err(1, NULL);
optind++;
}
/* Check for any remaining arguments. */
if (optind < argc)
usage(stderr);
if (name) {
set_name(type, name);
free(name);
} else
show_name(type);
return 0;
}
/* vim: set noexpandtab: */
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