nss-myhostname.c revision 8041b5bada31db152de80e45b3047ed32cef6880
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
This file is part of nss-myhostname.
Copyright 2008-2011 Lennart Poettering
nss-myhostname 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.
nss-myhostname 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 nss-myhostname; If not, see
<http://www.gnu.org/licenses/>.
***/
#include <limits.h>
#include <nss.h>
#include <sys/types.h>
#include <netdb.h>
#include <errno.h>
#include <string.h>
#include <assert.h>
#include <unistd.h>
#include <net/if.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include "netlink.h"
/* We use 127.0.0.2 as IPv4 address. This has the advantage over
* 127.0.0.1 that it can be translated back to the local hostname. For
* IPv6 we use ::1 which unfortunately will not translate back to the
* hostname but instead something like "localhost6" or so. */
#define LOCALADDRESS_IPV4 (htonl(0x7F000002))
#define LOCALADDRESS_IPV6 &in6addr_loopback
#define LOOPBACK_INTERFACE "lo"
#define ALIGN(a) (((a+sizeof(void*)-1)/sizeof(void*))*sizeof(void*))
enum nss_status _nss_myhostname_gethostbyname4_r(
const char *name,
struct gaih_addrtuple **pat,
char *buffer, size_t buflen,
int *errnop, int *h_errnop,
int32_t *ttlp);
enum nss_status _nss_myhostname_gethostbyname3_r(
const char *name,
int af,
struct hostent *host,
char *buffer, size_t buflen,
int *errnop, int *h_errnop,
int32_t *ttlp,
char **canonp);
enum nss_status _nss_myhostname_gethostbyname2_r(
const char *name,
int af,
struct hostent *host,
char *buffer, size_t buflen,
int *errnop, int *h_errnop);
enum nss_status _nss_myhostname_gethostbyname_r(
const char *name,
struct hostent *host,
char *buffer, size_t buflen,
int *errnop, int *h_errnop);
enum nss_status _nss_myhostname_gethostbyaddr2_r(
const void* addr, socklen_t len,
int af,
struct hostent *host,
char *buffer, size_t buflen,
int *errnop, int *h_errnop,
int32_t *ttlp);
enum nss_status _nss_myhostname_gethostbyaddr_r(
const void* addr, socklen_t len,
int af,
struct hostent *host,
char *buffer, size_t buflen,
int *errnop, int *h_errnop);
enum nss_status _nss_myhostname_gethostbyname4_r(
const char *name,
struct gaih_addrtuple **pat,
char *buffer, size_t buflen,
int *errnop, int *h_errnop,
int32_t *ttlp) {
unsigned lo_ifi;
char hn[HOST_NAME_MAX+1];
size_t l, idx, ms;
char *r_name;
struct gaih_addrtuple *r_tuple, *r_tuple_prev = NULL;
struct address *addresses = NULL, *a;
unsigned n_addresses = 0, n;
memset(hn, 0, sizeof(hn));
if (gethostname(hn, sizeof(hn)-1) < 0) {
*errnop = errno;
*h_errnop = NO_RECOVERY;
return NSS_STATUS_UNAVAIL;
}
if (strcasecmp(name, hn) != 0) {
*errnop = ENOENT;
*h_errnop = HOST_NOT_FOUND;
return NSS_STATUS_NOTFOUND;
}
/* If this fails, n_addresses is 0. Which is fine */
netlink_acquire_addresses(&addresses, &n_addresses);
/* If this call fails we fill in 0 as scope. Which is fine */
lo_ifi = if_nametoindex(LOOPBACK_INTERFACE);
l = strlen(hn);
ms = ALIGN(l+1)+ALIGN(sizeof(struct gaih_addrtuple))*(n_addresses > 0 ? n_addresses : 2);
if (buflen < ms) {
*errnop = ENOMEM;
*h_errnop = NO_RECOVERY;
free(addresses);
return NSS_STATUS_TRYAGAIN;
}
/* First, fill in hostname */
r_name = buffer;
memcpy(r_name, hn, l+1);
idx = ALIGN(l+1);
if (n_addresses <= 0) {
/* Second, fill in IPv6 tuple */
r_tuple = (struct gaih_addrtuple*) (buffer + idx);
r_tuple->next = r_tuple_prev;
r_tuple->name = r_name;
r_tuple->family = AF_INET6;
memcpy(r_tuple->addr, LOCALADDRESS_IPV6, 16);
r_tuple->scopeid = (uint32_t) lo_ifi;
idx += ALIGN(sizeof(struct gaih_addrtuple));
r_tuple_prev = r_tuple;
/* Third, fill in IPv4 tuple */
r_tuple = (struct gaih_addrtuple*) (buffer + idx);
r_tuple->next = r_tuple_prev;
r_tuple->name = r_name;
r_tuple->family = AF_INET;
*(uint32_t*) r_tuple->addr = LOCALADDRESS_IPV4;
r_tuple->scopeid = (uint32_t) lo_ifi;
idx += ALIGN(sizeof(struct gaih_addrtuple));
r_tuple_prev = r_tuple;
}
/* Fourth, fill actual addresses in, but in backwards order */
for (a = addresses + n_addresses - 1, n = 0; n < n_addresses; n++, a--) {
r_tuple = (struct gaih_addrtuple*) (buffer + idx);
r_tuple->next = r_tuple_prev;
r_tuple->name = r_name;
r_tuple->family = a->family;
r_tuple->scopeid = a->ifindex;
memcpy(r_tuple->addr, a->address, 16);
idx += ALIGN(sizeof(struct gaih_addrtuple));
r_tuple_prev = r_tuple;
}
/* Verify the size matches */
assert(idx == ms);
*pat = r_tuple_prev;
if (ttlp)
*ttlp = 0;
free(addresses);
return NSS_STATUS_SUCCESS;
}
static enum nss_status fill_in_hostent(
const char *hn,
int af,
struct hostent *result,
char *buffer, size_t buflen,
int *errnop, int *h_errnop,
int32_t *ttlp,
char **canonp) {
size_t l, idx, ms;
char *r_addr, *r_name, *r_aliases, *r_addr_list;
size_t alen;
struct address *addresses = NULL, *a;
unsigned n_addresses = 0, n, c;
alen = PROTO_ADDRESS_SIZE(af);
netlink_acquire_addresses(&addresses, &n_addresses);
for (a = addresses, n = 0, c = 0; n < n_addresses; a++, n++)
if (af == a->family)
c++;
l = strlen(hn);
ms = ALIGN(l+1)+
sizeof(char*)+
(c > 0 ? c : 1)*ALIGN(alen)+
(c > 0 ? c+1 : 2)*sizeof(char*);
if (buflen < ms) {
*errnop = ENOMEM;
*h_errnop = NO_RECOVERY;
free(addresses);
return NSS_STATUS_TRYAGAIN;
}
/* First, fill in hostname */
r_name = buffer;
memcpy(r_name, hn, l+1);
idx = ALIGN(l+1);
/* Second, create (empty) aliases array */
r_aliases = buffer + idx;
*(char**) r_aliases = NULL;
idx += sizeof(char*);
/* Third, add addresses */
r_addr = buffer + idx;
if (c > 0) {
unsigned i = 0;
for (a = addresses, n = 0; n < n_addresses; a++, n++) {
if (af != a->family)
continue;
memcpy(r_addr + i*ALIGN(alen), a->address, alen);
i++;
}
assert(i == c);
idx += c*ALIGN(alen);
} else {
if (af == AF_INET)
*(uint32_t*) r_addr = LOCALADDRESS_IPV4;
else
memcpy(r_addr, LOCALADDRESS_IPV6, 16);
idx += ALIGN(alen);
}
/* Fourth, add address pointer array */
r_addr_list = buffer + idx;
if (c > 0) {
unsigned i = 0;
for (a = addresses, n = 0; n < n_addresses; a++, n++) {
if (af != a->family)
continue;
((char**) r_addr_list)[i] = (r_addr + i*ALIGN(alen));
i++;
}
assert(i == c);
((char**) r_addr_list)[c] = NULL;
idx += (c+1)*sizeof(char*);
} else {
((char**) r_addr_list)[0] = r_addr;
((char**) r_addr_list)[1] = NULL;
idx += 2*sizeof(char*);
}
/* Verify the size matches */
assert(idx == ms);
result->h_name = r_name;
result->h_aliases = (char**) r_aliases;
result->h_addrtype = af;
result->h_length = alen;
result->h_addr_list = (char**) r_addr_list;
if (ttlp)
*ttlp = 0;
if (canonp)
*canonp = r_name;
free(addresses);
return NSS_STATUS_SUCCESS;
}
enum nss_status _nss_myhostname_gethostbyname3_r(
const char *name,
int af,
struct hostent *host,
char *buffer, size_t buflen,
int *errnop, int *h_errnop,
int32_t *ttlp,
char **canonp) {
char hn[HOST_NAME_MAX+1];
if (af == AF_UNSPEC)
af = AF_INET;
if (af != AF_INET && af != AF_INET6) {
*errnop = EAFNOSUPPORT;
*h_errnop = NO_DATA;
return NSS_STATUS_UNAVAIL;
}
memset(hn, 0, sizeof(hn));
if (gethostname(hn, sizeof(hn)-1) < 0) {
*errnop = errno;
*h_errnop = NO_RECOVERY;
return NSS_STATUS_UNAVAIL;
}
if (strcasecmp(name, hn) != 0) {
*errnop = ENOENT;
*h_errnop = HOST_NOT_FOUND;
return NSS_STATUS_NOTFOUND;
}
return fill_in_hostent(hn, af, host, buffer, buflen, errnop, h_errnop, ttlp, canonp);
}
enum nss_status _nss_myhostname_gethostbyname2_r(
const char *name,
int af,
struct hostent *host,
char *buffer, size_t buflen,
int *errnop, int *h_errnop) {
return _nss_myhostname_gethostbyname3_r(
name,
af,
host,
buffer, buflen,
errnop, h_errnop,
NULL,
NULL);
}
enum nss_status _nss_myhostname_gethostbyname_r(
const char *name,
struct hostent *host,
char *buffer, size_t buflen,
int *errnop, int *h_errnop) {
return _nss_myhostname_gethostbyname3_r(
name,
AF_UNSPEC,
host,
buffer, buflen,
errnop, h_errnop,
NULL,
NULL);
}
enum nss_status _nss_myhostname_gethostbyaddr2_r(
const void* addr, socklen_t len,
int af,
struct hostent *host,
char *buffer, size_t buflen,
int *errnop, int *h_errnop,
int32_t *ttlp) {
char hn[HOST_NAME_MAX+1];
struct address *addresses = NULL, *a;
unsigned n_addresses = 0, n;
if (len != PROTO_ADDRESS_SIZE(af)) {
*errnop = EINVAL;
*h_errnop = NO_RECOVERY;
return NSS_STATUS_UNAVAIL;
}
if (af == AF_INET) {
if ((*(uint32_t*) addr) == LOCALADDRESS_IPV4)
goto found;
} else if (af == AF_INET6) {
if (memcmp(addr, LOCALADDRESS_IPV6, 16) == 0)
goto found;
} else {
*errnop = EAFNOSUPPORT;
*h_errnop = NO_DATA;
return NSS_STATUS_UNAVAIL;
}
netlink_acquire_addresses(&addresses, &n_addresses);
for (a = addresses, n = 0; n < n_addresses; n++, a++) {
if (af != a->family)
continue;
if (memcmp(addr, a->address, PROTO_ADDRESS_SIZE(af)) == 0)
goto found;
}
*errnop = ENOENT;
*h_errnop = HOST_NOT_FOUND;
free(addresses);
return NSS_STATUS_NOTFOUND;
found:
free(addresses);
memset(hn, 0, sizeof(hn));
if (gethostname(hn, sizeof(hn)-1) < 0) {
*errnop = errno;
*h_errnop = NO_RECOVERY;
return NSS_STATUS_UNAVAIL;
}
return fill_in_hostent(hn, af, host, buffer, buflen, errnop, h_errnop, ttlp, NULL);
}
enum nss_status _nss_myhostname_gethostbyaddr_r(
const void* addr, socklen_t len,
int af,
struct hostent *host,
char *buffer, size_t buflen,
int *errnop, int *h_errnop) {
return _nss_myhostname_gethostbyaddr2_r(
addr, len,
af,
host,
buffer, buflen,
errnop, h_errnop,
NULL);
}