dist/dhcp/common/resolv.c

   1 /* resolv.c
   2
   3    Parser for /etc/resolv.conf file. */
   4
   5 /*
   6  * Copyright (c) 2004 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  *   http://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  * ``http://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 #ifndef lint
  36 static char copyright[] =
  37 "$Id: resolv.c,v 1.4 2005/08/11 17:13:21 drochner Exp $ Copyright (c) 2004 Internet Systems Consortium.  All rights reserved.\n";
  38 #endif /* not lint */
  39
  40 #include "dhcpd.h"
  41
  42 struct name_server *name_servers;
  43 struct domain_search_list *domains;
  44 char path_resolv_conf [] = _PATH_RESOLV_CONF;
  45
  46 void read_resolv_conf (parse_time)
  47         TIME parse_time;
  48 {
  49         int file;
  50         struct parse *cfile;
  51         const char *val;
  52         int token;
  53         struct name_server *sp, *sl, *ns;
  54         struct domain_search_list *dp, *dl, *nd;
  55
  56         if ((file = open (path_resolv_conf, O_RDONLY)) < 0) {
  57                 log_error ("Can't open %s: %m", path_resolv_conf);
  58                 return;
  59         }
  60
  61         cfile = (struct parse *)0;
  62         new_parse (&cfile, file, (char *)0, 0, path_resolv_conf, 1);
  63
  64         do {
  65                 token = next_token (&val, (unsigned *)0, cfile);
  66                 if (token == END_OF_FILE)
  67                         break;
  68                 else if (token == EOL)
  69                         continue;
  70                 else if (token == DOMAIN || token == SEARCH) {
  71                         do {
  72                                 struct domain_search_list *nd, **dp;
  73                                 char *dn;
  74
  75                                 dn = parse_host_name (cfile);
  76                                 if (!dn)
  77                                         break;
  78
  79                                 dp = &domains;
  80                                 for (nd = domains; nd; nd = nd -> next) {
  81                                         dp = &nd -> next;
  82                                         if (!strcmp (nd -> domain, dn))
  83                                                 break;
  84                                 }
  85                                 if (!nd) {
  86                                         nd = new_domain_search_list (MDL);
  87                                         if (!nd)
  88                                                 log_fatal ("No memory for %s",
  89                                                            dn);
  90                                         nd -> next =
  91                                                 (struct domain_search_list *)0;
  92                                         *dp = nd;
  93                                         nd -> domain = dn;
  94                                         dn = (char *)0;
  95                                 }
  96                                 nd -> rcdate = parse_time;
  97                                 token = peek_token (&val,
  98                                                     (unsigned *)0, cfile);
  99                         } while (token != EOL);
 100                         if (token != EOL) {
 101                                 parse_warn (cfile,
 102                                             "junk after domain declaration");
 103                                 skip_to_semi (cfile);
 104                         }
 105                         token = next_token (&val, (unsigned *)0, cfile);
 106                 } else if (token == NAMESERVER) {
 107                         struct name_server *ns, **sp;
 108                         struct iaddr iaddr;
 109
 110                         parse_ip_addr (cfile, &iaddr);
 111
 112                         sp = &name_servers;
 113                         for (ns = name_servers; ns; ns = ns -> next) {
 114                                 sp = &ns -> next;
 115                                 if (!memcmp (&ns -> addr.sin_addr,
 116                                              iaddr.iabuf, iaddr.len))
 117                                         break;
 118                         }
 119                         if (!ns) {
 120                                 ns = new_name_server (MDL);
 121                                 if (!ns)
 122                                     log_fatal ("No memory for nameserver %s",
 123                                                piaddr (iaddr));
 124                                 ns -> next = (struct name_server *)0;
 125                                 *sp = ns;
 126                                 memset (&ns->addr, 0, sizeof ns->addr);
 127                                 memcpy (&ns -> addr.sin_addr,
 128                                         iaddr.iabuf, iaddr.len);
 129 #ifdef HAVE_SA_LEN
 130                                 ns -> addr.sin_len = sizeof ns -> addr;
 131 #endif
 132                                 ns -> addr.sin_family = AF_INET;
 133                                 ns -> addr.sin_port = htons (53);
 134                         }
 135                         ns -> rcdate = parse_time;
 136                         skip_to_semi (cfile);
 137                 } else
 138                         skip_to_semi (cfile); /* Ignore what we don't grok. */
 139         } while (1);
 140         token = next_token (&val, (unsigned *)0, cfile);
 141
 142         /* Lose servers that are no longer in /etc/resolv.conf. */
 143         sl = (struct name_server *)0;
 144         for (sp = name_servers; sp; sp = ns) {
 145                 ns = sp -> next;
 146                 if (sp -> rcdate != parse_time) {
 147                         if (sl)
 148                                 sl -> next = sp -> next;
 149                         else
 150                                 name_servers = sp -> next;
 151                         /* We can't actually free the name server structure,
 152                            because somebody might be hanging on to it.    If
 153                            your /etc/resolv.conf file changes a lot, this
 154                            could be a noticable memory leak. */
 155                 } else
 156                         sl = sp;
 157         }
 158
 159         /* Lose domains that are no longer in /etc/resolv.conf. */
 160         dl = (struct domain_search_list *)0;
 161         for (dp = domains; dp; dp = nd) {
 162                 nd = dp -> next;
 163                 if (dp -> rcdate != parse_time) {
 164                         if (dl)
 165                                 dl -> next = dp -> next;
 166                         else
 167                                 domains = dp -> next;
 168                         free_domain_search_list (dp, MDL);
 169                 } else
 170                         dl = dp;
 171         }
 172         close (file);
 173         end_parse (&cfile);
 174 }
 175
 176 /* Pick a name server from the /etc/resolv.conf file. */
 177
 178 struct name_server *first_name_server ()
 179 {
 180         static TIME rcdate;
 181         struct stat st;
 182
 183         /* Check /etc/resolv.conf and reload it if it's changed. */
 184         if (cur_time > rcdate) {
 185                 if (stat (path_resolv_conf, &st) < 0) {
 186                         log_error ("Can't stat %s", path_resolv_conf);
 187                         return (struct name_server *)0;
 188                 }
 189                 if (st.st_mtime > rcdate) {
 190                         rcdate = cur_time + 1;
 191
 192                         read_resolv_conf (rcdate);
 193                 }
 194         }
 195
 196         return name_servers;
 197 }