common/resolv.c

   1 /* resolv.c
   2
   3    Parser for /etc/resolv.conf file. */
   4
   5 /*
   6  * Copyright (c) 2004-2007,2009 by Internet Systems Consortium, Inc. ("ISC")
   7  * Copyright (c) 1996-2003 by Internet Software Consortium
   8  *
   9  * Permission to use, copy, modify, and distribute this software for any
  10  * purpose with or without fee is hereby granted, provided that the above
  11  * copyright notice and this permission notice appear in all copies.
  12  *
  13  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
  14  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  15  * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
  16  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  17  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  18  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
  19  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  20  *
  21  *   Internet Systems Consortium, Inc.
  22  *   950 Charter Street
  23  *   Redwood City, CA 94063
  24  *   <info@isc.org>
  25  *   https://www.isc.org/
  26  *
  27  * This software has been written for Internet Systems Consortium
  28  * by Ted Lemon in cooperation with Vixie Enterprises and Nominum, Inc.
  29  * To learn more about Internet Systems Consortium, see
  30  * ``https://www.isc.org/''.  To learn more about Vixie Enterprises,
  31  * see ``http://www.vix.com''.   To learn more about Nominum, Inc., see
  32  * ``http://www.nominum.com''.
  33  */
  34
  35 #include "dhcpd.h"
  36
  37 struct name_server *name_servers;
  38 struct domain_search_list *domains;
  39 char path_resolv_conf [] = _PATH_RESOLV_CONF;
  40
  41 void read_resolv_conf (parse_time)
  42         TIME parse_time;
  43 {
  44         int file;
  45         struct parse *cfile;
  46         const char *val;
  47         int token;
  48         struct name_server *sp, *sl, *ns;
  49         struct domain_search_list *dp, *dl, *nd;
  50         isc_result_t status;
  51
  52         if ((file = open (path_resolv_conf, O_RDONLY)) < 0) {
  53                 log_error ("Can't open %s: %m", path_resolv_conf);
  54                 return;
  55         }
  56
  57         cfile = NULL;
  58         status = new_parse(&cfile, file, NULL, 0, path_resolv_conf, 1);
  59         if (status != ISC_R_SUCCESS || cfile == NULL)
  60                 return;
  61
  62         do {
  63                 token = next_token (&val, (unsigned *)0, cfile);
  64                 if (token == END_OF_FILE)
  65                         break;
  66                 else if (token == EOL)
  67                         continue;
  68                 else if (token == DOMAIN || token == SEARCH) {
  69                         do {
  70                                 struct domain_search_list *nd, **dp;
  71                                 char *dn;
  72
  73                                 dn = parse_host_name (cfile);
  74                                 if (!dn)
  75                                         break;
  76
  77                                 dp = &domains;
  78                                 for (nd = domains; nd; nd = nd -> next) {
  79                                         dp = &nd -> next;
  80                                         if (!strcmp (nd -> domain, dn))
  81                                                 break;
  82                                 }
  83                                 if (!nd) {
  84                                         nd = new_domain_search_list (MDL);
  85                                         if (!nd)
  86                                                 log_fatal ("No memory for %s",
  87                                                            dn);
  88                                         nd -> next =
  89                                                 (struct domain_search_list *)0;
  90                                         *dp = nd;
  91                                         nd -> domain = dn;
  92                                         dn = (char *)0;
  93                                 }
  94                                 nd -> rcdate = parse_time;
  95                                 token = peek_token (&val,
  96                                                     (unsigned *)0, cfile);
  97                         } while (token != EOL);
  98                         if (token != EOL) {
  99                                 parse_warn (cfile,
 100                                             "junk after domain declaration");
 101                                 skip_to_semi (cfile);
 102                         }
 103                         token = next_token (&val, (unsigned *)0, cfile);
 104                 } else if (token == NAMESERVER) {
 105                         struct name_server *ns, **sp;
 106                         struct iaddr iaddr;
 107
 108                         parse_ip_addr (cfile, &iaddr);
 109
 110                         sp = &name_servers;
 111                         for (ns = name_servers; ns; ns = ns -> next) {
 112                                 sp = &ns -> next;
 113                                 if (!memcmp (&ns -> addr.sin_addr,
 114                                              iaddr.iabuf, iaddr.len))
 115                                         break;
 116                         }
 117                         if (!ns) {
 118                                 ns = new_name_server (MDL);
 119                                 if (!ns)
 120                                     log_fatal ("No memory for nameserver %s",
 121                                                piaddr (iaddr));
 122                                 ns -> next = (struct name_server *)0;
 123                                 *sp = ns;
 124                                 memcpy (&ns -> addr.sin_addr,
 125                                         iaddr.iabuf, iaddr.len);
 126 #ifdef HAVE_SA_LEN
 127                                 ns -> addr.sin_len = sizeof ns -> addr;
 128 #endif
 129                                 ns -> addr.sin_family = AF_INET;
 130                                 ns -> addr.sin_port = htons (53);
 131                                 memset (ns -> addr.sin_zero, 0,
 132                                         sizeof ns -> addr.sin_zero);
 133                         }
 134                         ns -> rcdate = parse_time;
 135                         skip_to_semi (cfile);
 136                 } else
 137                         skip_to_semi (cfile); /* Ignore what we don't grok. */
 138         } while (1);
 139         token = next_token (&val, (unsigned *)0, cfile);
 140
 141         /* Lose servers that are no longer in /etc/resolv.conf. */
 142         sl = (struct name_server *)0;
 143         for (sp = name_servers; sp; sp = ns) {
 144                 ns = sp -> next;
 145                 if (sp -> rcdate != parse_time) {
 146                         if (sl)
 147                                 sl -> next = sp -> next;
 148                         else
 149                                 name_servers = sp -> next;
 150                         /* We can't actually free the name server structure,
 151                            because somebody might be hanging on to it.    If
 152                            your /etc/resolv.conf file changes a lot, this
 153                            could be a noticeable memory leak. */
 154                 } else
 155                         sl = sp;
 156         }
 157
 158         /* Lose domains that are no longer in /etc/resolv.conf. */
 159         dl = (struct domain_search_list *)0;
 160         for (dp = domains; dp; dp = nd) {
 161                 nd = dp -> next;
 162                 if (dp -> rcdate != parse_time) {
 163                         if (dl)
 164                                 dl -> next = dp -> next;
 165                         else
 166                                 domains = dp -> next;
 167                         free_domain_search_list (dp, MDL);
 168                 } else
 169                         dl = dp;
 170         }
 171         end_parse (&cfile);
 172 }
 173
 174 /* Pick a name server from the /etc/resolv.conf file. */
 175
 176 struct name_server *first_name_server ()
 177 {
 178         static TIME rcdate;
 179         struct stat st;
 180
 181         /* Check /etc/resolv.conf and reload it if it's changed. */
 182         if (cur_time > rcdate) {
 183                 if (stat (path_resolv_conf, &st) < 0) {
 184                         log_error ("Can't stat %s", path_resolv_conf);
 185                         return (struct name_server *)0;
 186                 }
 187                 if (st.st_mtime > rcdate) {
 188                         rcdate = cur_time + 1;
 189
 190                         read_resolv_conf (rcdate);
 191                 }
 192         }
 193
 194         return name_servers;
 195 }