common/resolv.c

   1 /* resolv.c
   2
   3    Parser for /etc/resolv.conf file. */
   4
   5 /*
   6  * Copyright (c) 1995, 1996, 1997 The Internet Software Consortium.
   7  * All rights reserved.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  *
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  * 3. Neither the name of The Internet Software Consortium nor the names
  19  *    of its contributors may be used to endorse or promote products derived
  20  *    from this software without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
  23  * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
  24  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  25  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  26  * DISCLAIMED.  IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
  27  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  28  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  29  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  30  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  31  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  32  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  33  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  * This software has been written for the Internet Software Consortium
  37  * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
  38  * Enterprises.  To learn more about the Internet Software Consortium,
  39  * see ``http://www.vix.com/isc''.  To learn more about Vixie
  40  * Enterprises, see ``http://www.vix.com''.
  41  */
  42
  43 #ifndef lint
  44 static char copyright[] =
  45 "$Id: resolv.c,v 1.7 1999/02/24 17:56:48 mellon Exp $ Copyright (c) 1995, 1996 The Internet Software Consortium.  All rights reserved.\n";
  46 #endif /* not lint */
  47
  48 #include "dhcpd.h"
  49 #include "dhctoken.h"
  50
  51 struct name_server *name_servers;
  52 struct domain_search_list *domains;
  53 char path_resolv_conf [] = _PATH_RESOLV_CONF;
  54
  55 void read_resolv_conf (parse_time)
  56         TIME parse_time;
  57 {
  58         FILE *cfile;
  59         char *val;
  60         int token;
  61         int declaration = 0;
  62         struct name_server *sp, *sl, *ns;
  63         struct domain_search_list *dp, *dl, *nd;
  64         struct iaddr *iaddr;
  65
  66         new_parse (path_resolv_conf);
  67
  68         eol_token = 1;
  69         if ((cfile = fopen (path_resolv_conf, "r")) == NULL) {
  70                 log_error ("Can't open %s: %m", path_resolv_conf);
  71                 return;
  72         }
  73
  74         do {
  75                 token = next_token (&val, cfile);
  76                 if (token == EOF)
  77                         break;
  78                 else if (token == EOL)
  79                         continue;
  80                 else if (token == DOMAIN || token == SEARCH) {
  81                         do {
  82                                 struct domain_search_list *nd, **dp;
  83                                 char *dn;
  84
  85                                 dn = parse_host_name (cfile);
  86                                 if (!dn)
  87                                         break;
  88
  89                                 dp = &domains;
  90                                 for (nd = domains; nd; nd = nd -> next) {
  91                                         dp = &nd -> next;
  92                                         if (!strcmp (nd -> domain, dn))
  93                                                 break;
  94                                 }
  95                                 if (!nd) {
  96                                         nd = new_domain_search_list
  97                                                 ("read_resolv_conf");
  98                                         if (!nd)
  99                                                 log_fatal ("No memory for %s", dn);
 100                                         nd -> next =
 101                                                 (struct domain_search_list *)0;
 102                                         *dp = nd;
 103                                         nd -> domain = dn;
 104                                         dn = (char *)0;
 105                                 }
 106                                 nd -> rcdate = parse_time;
 107                                 token = peek_token (&val, cfile);
 108                         } while (token != EOL);
 109                         if (token != EOL) {
 110                                 parse_warn ("junk after domain declaration");
 111                                 skip_to_semi (cfile);
 112                         }
 113                         token = next_token (&val, cfile);
 114                 } else if (token == NAMESERVER) {
 115                         struct name_server *ns, **sp;
 116                         struct iaddr iaddr;
 117
 118                         parse_ip_addr (cfile, &iaddr);
 119
 120                         sp = &name_servers;
 121                         for (ns = name_servers; ns; ns = ns -> next) {
 122                                 sp = &ns -> next;
 123                                 if (!memcmp (&ns -> addr.sin_addr,
 124                                              iaddr.iabuf, iaddr.len))
 125                                         break;
 126                         }
 127                         if (!ns) {
 128                                 ns = new_name_server ("read_resolv_conf");
 129                                 if (!ns)
 130                                         log_fatal ("No memory for nameserver %s",
 131                                                piaddr (iaddr));
 132                                 ns -> next = (struct name_server *)0;
 133                                 *sp = ns;
 134                                 memcpy (&ns -> addr.sin_addr,
 135                                         iaddr.iabuf, iaddr.len);
 136 #ifdef HAVE_SA_LEN
 137                                 ns -> addr.sin_len = sizeof ns -> addr;
 138 #endif
 139                                 ns -> addr.sin_family = AF_INET;
 140                                 ns -> addr.sin_port = htons (53);
 141                                 memset (ns -> addr.sin_zero, 0,
 142                                         sizeof ns -> addr.sin_zero);
 143                         }
 144                         ns -> rcdate = parse_time;
 145                         skip_to_semi (cfile);
 146                 } else
 147                         skip_to_semi (cfile); /* Ignore what we don't grok. */
 148         } while (1);
 149         token = next_token (&val, cfile); /* Clear the peek buffer */
 150
 151         /* Lose servers that are no longer in /etc/resolv.conf. */
 152         sl = (struct name_server *)0;
 153         for (sp = name_servers; sp; sp = ns) {
 154                 ns = sp -> next;
 155                 if (sp -> rcdate != parse_time) {
 156                         if (sl)
 157                                 sl -> next = sp -> next;
 158                         else
 159                                 name_servers = sp -> next;
 160                         /* We can't actually free the name server structure,
 161                            because somebody might be hanging on to it.    If
 162                            your /etc/resolv.conf file changes a lot, this
 163                            could be a noticable memory leak. */
 164                 } else
 165                         sl = sp;
 166         }
 167
 168         /* Lose domains that are no longer in /etc/resolv.conf. */
 169         dl = (struct domain_search_list *)0;
 170         for (dp = domains; dp; dp = nd) {
 171                 nd = dp -> next;
 172                 if (dp -> rcdate != parse_time) {
 173                         if (dl)
 174                                 dl -> next = dp -> next;
 175                         else
 176                                 domains = dp -> next;
 177                         free_domain_search_list (dp, "pick_name_server");
 178                 } else
 179                         dl = dp;
 180         }
 181         eol_token = 0;
 182 }
 183
 184 /* Pick a name server from the /etc/resolv.conf file. */
 185
 186 struct name_server *first_name_server ()
 187 {
 188         FILE *rc;
 189         static TIME rcdate;
 190         struct stat st;
 191
 192         /* Check /etc/resolv.conf and reload it if it's changed. */
 193         if (cur_time > rcdate) {
 194                 if (stat (path_resolv_conf, &st) < 0) {
 195                         log_error ("Can't stat %s", path_resolv_conf);
 196                         return (struct name_server *)0;
 197                 }
 198                 if (st.st_mtime > rcdate) {
 199                         char rcbuf [512];
 200                         char *s, *t, *u;
 201                         rcdate = cur_time + 1;
 202
 203                         read_resolv_conf (rcdate);
 204                 }
 205         }
 206
 207         return name_servers;
 208 }