src/nss-myhostname/nss-myhostname.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2008-2011 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU Lesser General Public License as published by
  10   the Free Software Foundation; either version 2.1 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include <limits.h>
  23 #include <nss.h>
  24 #include <sys/types.h>
  25 #include <netdb.h>
  26 #include <errno.h>
  27 #include <string.h>
  28 #include <assert.h>
  29 #include <unistd.h>
  30 #include <net/if.h>
  31 #include <stdlib.h>
  32 #include <arpa/inet.h>
  33
  34 #include "ifconf.h"
  35 #include "macro.h"
  36 #include "util.h"
  37
  38 /* We use 127.0.0.2 as IPv4 address. This has the advantage over
  39  * 127.0.0.1 that it can be translated back to the local hostname. For
  40  * IPv6 we use ::1 which unfortunately will not translate back to the
  41  * hostname but instead something like "localhost6" or so. */
  42
  43 #define LOCALADDRESS_IPV4 (htonl(0x7F000002))
  44 #define LOCALADDRESS_IPV6 &in6addr_loopback
  45 #define LOOPBACK_INTERFACE "lo"
  46
  47 enum nss_status _nss_myhostname_gethostbyname4_r(
  48                 const char *name,
  49                 struct gaih_addrtuple **pat,
  50                 char *buffer, size_t buflen,
  51                 int *errnop, int *h_errnop,
  52                 int32_t *ttlp) _public_;
  53
  54 enum nss_status _nss_myhostname_gethostbyname3_r(
  55                 const char *name,
  56                 int af,
  57                 struct hostent *host,
  58                 char *buffer, size_t buflen,
  59                 int *errnop, int *h_errnop,
  60                 int32_t *ttlp,
  61                 char **canonp) _public_;
  62
  63 enum nss_status _nss_myhostname_gethostbyname2_r(
  64                 const char *name,
  65                 int af,
  66                 struct hostent *host,
  67                 char *buffer, size_t buflen,
  68                 int *errnop, int *h_errnop) _public_;
  69
  70 enum nss_status _nss_myhostname_gethostbyname_r(
  71                 const char *name,
  72                 struct hostent *host,
  73                 char *buffer, size_t buflen,
  74                 int *errnop, int *h_errnop) _public_;
  75
  76 enum nss_status _nss_myhostname_gethostbyaddr2_r(
  77                 const void* addr, socklen_t len,
  78                 int af,
  79                 struct hostent *host,
  80                 char *buffer, size_t buflen,
  81                 int *errnop, int *h_errnop,
  82                 int32_t *ttlp) _public_;
  83
  84 enum nss_status _nss_myhostname_gethostbyaddr_r(
  85                 const void* addr, socklen_t len,
  86                 int af,
  87                 struct hostent *host,
  88                 char *buffer, size_t buflen,
  89                 int *errnop, int *h_errnop) _public_;
  90
  91 enum nss_status _nss_myhostname_gethostbyname4_r(
  92                 const char *name,
  93                 struct gaih_addrtuple **pat,
  94                 char *buffer, size_t buflen,
  95                 int *errnop, int *h_errnop,
  96                 int32_t *ttlp) {
  97
  98         unsigned lo_ifi;
  99         char hn[HOST_NAME_MAX+1] = {};
 100         size_t l, idx, ms;
 101         char *r_name;
 102         struct gaih_addrtuple *r_tuple, *r_tuple_prev = NULL;
 103         struct address *addresses = NULL, *a;
 104         unsigned n_addresses = 0, n;
 105
 106         if (gethostname(hn, sizeof(hn)-1) < 0) {
 107                 *errnop = errno;
 108                 *h_errnop = NO_RECOVERY;
 109                 return NSS_STATUS_UNAVAIL;
 110         }
 111
 112         if (strcasecmp(name, hn) != 0) {
 113                 *errnop = ENOENT;
 114                 *h_errnop = HOST_NOT_FOUND;
 115                 return NSS_STATUS_NOTFOUND;
 116         }
 117
 118         /* If this fails, n_addresses is 0. Which is fine */
 119         ifconf_acquire_addresses(&addresses, &n_addresses);
 120
 121         /* If this call fails we fill in 0 as scope. Which is fine */
 122         lo_ifi = if_nametoindex(LOOPBACK_INTERFACE);
 123
 124         l = strlen(hn);
 125         ms = ALIGN(l+1)+ALIGN(sizeof(struct gaih_addrtuple))*(n_addresses > 0 ? n_addresses : 2);
 126         if (buflen < ms) {
 127                 *errnop = ENOMEM;
 128                 *h_errnop = NO_RECOVERY;
 129                 free(addresses);
 130                 return NSS_STATUS_TRYAGAIN;
 131         }
 132
 133         /* First, fill in hostname */
 134         r_name = buffer;
 135         memcpy(r_name, hn, l+1);
 136         idx = ALIGN(l+1);
 137
 138         if (n_addresses <= 0) {
 139                 /* Second, fill in IPv6 tuple */
 140                 r_tuple = (struct gaih_addrtuple*) (buffer + idx);
 141                 r_tuple->next = r_tuple_prev;
 142                 r_tuple->name = r_name;
 143                 r_tuple->family = AF_INET6;
 144                 memcpy(r_tuple->addr, LOCALADDRESS_IPV6, 16);
 145                 r_tuple->scopeid = (uint32_t) lo_ifi;
 146
 147                 idx += ALIGN(sizeof(struct gaih_addrtuple));
 148                 r_tuple_prev = r_tuple;
 149
 150                 /* Third, fill in IPv4 tuple */
 151                 r_tuple = (struct gaih_addrtuple*) (buffer + idx);
 152                 r_tuple->next = r_tuple_prev;
 153                 r_tuple->name = r_name;
 154                 r_tuple->family = AF_INET;
 155                 *(uint32_t*) r_tuple->addr = LOCALADDRESS_IPV4;
 156                 r_tuple->scopeid = (uint32_t) lo_ifi;
 157
 158                 idx += ALIGN(sizeof(struct gaih_addrtuple));
 159                 r_tuple_prev = r_tuple;
 160         }
 161
 162         /* Fourth, fill actual addresses in, but in backwards order */
 163         for (a = addresses + n_addresses - 1, n = 0; n < n_addresses; n++, a--) {
 164                 r_tuple = (struct gaih_addrtuple*) (buffer + idx);
 165                 r_tuple->next = r_tuple_prev;
 166                 r_tuple->name = r_name;
 167                 r_tuple->family = a->family;
 168                 r_tuple->scopeid = a->ifindex;
 169                 memcpy(r_tuple->addr, a->address, 16);
 170
 171                 idx += ALIGN(sizeof(struct gaih_addrtuple));
 172                 r_tuple_prev = r_tuple;
 173         }
 174
 175         /* Verify the size matches */
 176         assert(idx == ms);
 177
 178         /* Nscd expects us to store the first record in **pat. */
 179         if (*pat)
 180                 **pat = *r_tuple_prev;
 181         else
 182                 *pat = r_tuple_prev;
 183
 184         if (ttlp)
 185                 *ttlp = 0;
 186
 187         free(addresses);
 188
 189         return NSS_STATUS_SUCCESS;
 190 }
 191
 192 static enum nss_status fill_in_hostent(
 193                 const char *hn,
 194                 int af,
 195                 struct hostent *result,
 196                 char *buffer, size_t buflen,
 197                 int *errnop, int *h_errnop,
 198                 int32_t *ttlp,
 199                 char **canonp) {
 200
 201         size_t l, idx, ms;
 202         char *r_addr, *r_name, *r_aliases, *r_addr_list;
 203         size_t alen;
 204         struct address *addresses = NULL, *a;
 205         unsigned n_addresses = 0, n, c;
 206
 207         alen = PROTO_ADDRESS_SIZE(af);
 208
 209         ifconf_acquire_addresses(&addresses, &n_addresses);
 210
 211         for (a = addresses, n = 0, c = 0; n < n_addresses; a++, n++)
 212                 if (af == a->family)
 213                         c++;
 214
 215         l = strlen(hn);
 216         ms = ALIGN(l+1)+
 217                 sizeof(char*)+
 218                 (c > 0 ? c : 1)*ALIGN(alen)+
 219                 (c > 0 ? c+1 : 2)*sizeof(char*);
 220
 221         if (buflen < ms) {
 222                 *errnop = ENOMEM;
 223                 *h_errnop = NO_RECOVERY;
 224                 free(addresses);
 225                 return NSS_STATUS_TRYAGAIN;
 226         }
 227
 228         /* First, fill in hostname */
 229         r_name = buffer;
 230         memcpy(r_name, hn, l+1);
 231         idx = ALIGN(l+1);
 232
 233         /* Second, create (empty) aliases array */
 234         r_aliases = buffer + idx;
 235         *(char**) r_aliases = NULL;
 236         idx += sizeof(char*);
 237
 238         /* Third, add addresses */
 239         r_addr = buffer + idx;
 240         if (c > 0) {
 241                 unsigned i = 0;
 242
 243                 for (a = addresses, n = 0; n < n_addresses; a++, n++) {
 244                         if (af != a->family)
 245                                 continue;
 246
 247                         memcpy(r_addr + i*ALIGN(alen), a->address, alen);
 248                         i++;
 249                 }
 250
 251                 assert(i == c);
 252                 idx += c*ALIGN(alen);
 253         } else {
 254                 if (af == AF_INET)
 255                         *(uint32_t*) r_addr = LOCALADDRESS_IPV4;
 256                 else
 257                         memcpy(r_addr, LOCALADDRESS_IPV6, 16);
 258
 259                 idx += ALIGN(alen);
 260         }
 261
 262         /* Fourth, add address pointer array */
 263         r_addr_list = buffer + idx;
 264         if (c > 0) {
 265                 unsigned i = 0;
 266
 267                 for (a = addresses, n = 0; n < n_addresses; a++, n++) {
 268                         if (af != a->family)
 269                                 continue;
 270
 271                         ((char**) r_addr_list)[i] = (r_addr + i*ALIGN(alen));
 272                         i++;
 273                 }
 274
 275                 assert(i == c);
 276                 ((char**) r_addr_list)[c] = NULL;
 277                 idx += (c+1)*sizeof(char*);
 278
 279         } else {
 280                 ((char**) r_addr_list)[0] = r_addr;
 281                 ((char**) r_addr_list)[1] = NULL;
 282                 idx += 2*sizeof(char*);
 283         }
 284
 285         /* Verify the size matches */
 286         assert(idx == ms);
 287
 288         result->h_name = r_name;
 289         result->h_aliases = (char**) r_aliases;
 290         result->h_addrtype = af;
 291         result->h_length = alen;
 292         result->h_addr_list = (char**) r_addr_list;
 293
 294         if (ttlp)
 295                 *ttlp = 0;
 296
 297         if (canonp)
 298                 *canonp = r_name;
 299
 300         free(addresses);
 301
 302         return NSS_STATUS_SUCCESS;
 303 }
 304
 305 enum nss_status _nss_myhostname_gethostbyname3_r(
 306                 const char *name,
 307                 int af,
 308                 struct hostent *host,
 309                 char *buffer, size_t buflen,
 310                 int *errnop, int *h_errnop,
 311                 int32_t *ttlp,
 312                 char **canonp) {
 313
 314         char hn[HOST_NAME_MAX+1] = {};
 315
 316         if (af == AF_UNSPEC)
 317                 af = AF_INET;
 318
 319         if (af != AF_INET && af != AF_INET6) {
 320                 *errnop = EAFNOSUPPORT;
 321                 *h_errnop = NO_DATA;
 322                 return NSS_STATUS_UNAVAIL;
 323         }
 324
 325         if (gethostname(hn, sizeof(hn)-1) < 0) {
 326                 *errnop = errno;
 327                 *h_errnop = NO_RECOVERY;
 328                 return NSS_STATUS_UNAVAIL;
 329         }
 330
 331         if (strcasecmp(name, hn) != 0) {
 332                 *errnop = ENOENT;
 333                 *h_errnop = HOST_NOT_FOUND;
 334                 return NSS_STATUS_NOTFOUND;
 335         }
 336
 337         return fill_in_hostent(hn, af, host, buffer, buflen, errnop, h_errnop, ttlp, canonp);
 338 }
 339
 340 enum nss_status _nss_myhostname_gethostbyname2_r(
 341                 const char *name,
 342                 int af,
 343                 struct hostent *host,
 344                 char *buffer, size_t buflen,
 345                 int *errnop, int *h_errnop) {
 346
 347         return _nss_myhostname_gethostbyname3_r(
 348                         name,
 349                         af,
 350                         host,
 351                         buffer, buflen,
 352                         errnop, h_errnop,
 353                         NULL,
 354                         NULL);
 355 }
 356
 357 enum nss_status _nss_myhostname_gethostbyname_r(
 358                 const char *name,
 359                 struct hostent *host,
 360                 char *buffer, size_t buflen,
 361                 int *errnop, int *h_errnop) {
 362
 363         return _nss_myhostname_gethostbyname3_r(
 364                         name,
 365                         AF_UNSPEC,
 366                         host,
 367                         buffer, buflen,
 368                         errnop, h_errnop,
 369                         NULL,
 370                         NULL);
 371 }
 372
 373 enum nss_status _nss_myhostname_gethostbyaddr2_r(
 374                 const void* addr, socklen_t len,
 375                 int af,
 376                 struct hostent *host,
 377                 char *buffer, size_t buflen,
 378                 int *errnop, int *h_errnop,
 379                 int32_t *ttlp) {
 380
 381         char hn[HOST_NAME_MAX+1] = {};
 382         _cleanup_free_ struct address *addresses = NULL;
 383         struct address *a;
 384         unsigned n_addresses = 0, n;
 385
 386         if (len != PROTO_ADDRESS_SIZE(af)) {
 387                 *errnop = EINVAL;
 388                 *h_errnop = NO_RECOVERY;
 389                 return NSS_STATUS_UNAVAIL;
 390         }
 391
 392         if (af == AF_INET) {
 393
 394                 if ((*(uint32_t*) addr) == LOCALADDRESS_IPV4)
 395                         goto found;
 396
 397         } else if (af == AF_INET6) {
 398
 399                 if (memcmp(addr, LOCALADDRESS_IPV6, 16) == 0)
 400                         goto found;
 401
 402         } else {
 403                 *errnop = EAFNOSUPPORT;
 404                 *h_errnop = NO_DATA;
 405                 return NSS_STATUS_UNAVAIL;
 406         }
 407
 408         ifconf_acquire_addresses(&addresses, &n_addresses);
 409
 410         for (a = addresses, n = 0; n < n_addresses; n++, a++) {
 411                 if (af != a->family)
 412                         continue;
 413
 414                 if (memcmp(addr, a->address, PROTO_ADDRESS_SIZE(af)) == 0)
 415                         goto found;
 416         }
 417
 418         *errnop = ENOENT;
 419         *h_errnop = HOST_NOT_FOUND;
 420
 421         return NSS_STATUS_NOTFOUND;
 422
 423 found:
 424         if (gethostname(hn, sizeof(hn)-1) < 0) {
 425                 *errnop = errno;
 426                 *h_errnop = NO_RECOVERY;
 427
 428                 return NSS_STATUS_UNAVAIL;
 429         }
 430
 431         return fill_in_hostent(hn, af, host, buffer, buflen, errnop, h_errnop, ttlp, NULL);
 432
 433 }
 434
 435 enum nss_status _nss_myhostname_gethostbyaddr_r(
 436                 const void* addr, socklen_t len,
 437                 int af,
 438                 struct hostent *host,
 439                 char *buffer, size_t buflen,
 440                 int *errnop, int *h_errnop) {
 441
 442         return _nss_myhostname_gethostbyaddr2_r(
 443                         addr, len,
 444                         af,
 445                         host,
 446                         buffer, buflen,
 447                         errnop, h_errnop,
 448                         NULL);
 449 }