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/* resolv.c
Parser for /etc/resolv.conf file. */
/*
* Copyright (c) 2004-2017 by Internet Systems Consortium, Inc. ("ISC")
* Copyright (c) 1996-2003 by Internet Software Consortium
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
* OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
* Internet Systems Consortium, Inc.
* 950 Charter Street
* Redwood City, CA 94063
* <info@isc.org>
* https://www.isc.org/
*
*/
#include "dhcpd.h"
struct name_server *name_servers;
struct domain_search_list *domains;
char path_resolv_conf [] = _PATH_RESOLV_CONF;
void read_resolv_conf (parse_time)
TIME parse_time;
{
int file;
struct parse *cfile;
const char *val;
int token;
struct name_server *sp, *sl, *ns;
struct domain_search_list *dp, *dl, *nd;
isc_result_t status;
if ((file = open (path_resolv_conf, O_RDONLY)) < 0) {
log_error ("Can't open %s: %m", path_resolv_conf);
return;
}
cfile = NULL;
status = new_parse(&cfile, file, NULL, 0, path_resolv_conf, 1);
if (status != ISC_R_SUCCESS || cfile == NULL)
return;
do {
token = next_token (&val, (unsigned *)0, cfile);
if (token == END_OF_FILE)
break;
else if (token == EOL)
continue;
else if (token == DOMAIN || token == SEARCH) {
do {
struct domain_search_list *nd, **dp;
char *dn;
dn = parse_host_name (cfile);
if (!dn)
break;
dp = &domains;
for (nd = domains; nd; nd = nd -> next) {
dp = &nd -> next;
if (!strcmp (nd -> domain, dn))
break;
}
if (!nd) {
nd = new_domain_search_list (MDL);
if (!nd)
log_fatal ("No memory for %s",
dn);
nd -> next =
(struct domain_search_list *)0;
*dp = nd;
nd -> domain = dn;
}
nd -> rcdate = parse_time;
token = peek_token (&val,
(unsigned *)0, cfile);
} while (token != EOL);
if (token != EOL) {
parse_warn (cfile,
"junk after domain declaration");
skip_to_semi (cfile);
}
skip_token(&val, (unsigned *)0, cfile);
} else if (token == NAMESERVER) {
struct name_server *ns, **sp;
struct iaddr iaddr;
parse_ip_addr (cfile, &iaddr);
sp = &name_servers;
for (ns = name_servers; ns; ns = ns -> next) {
sp = &ns -> next;
if (!memcmp (&ns -> addr.sin_addr,
iaddr.iabuf, iaddr.len))
break;
}
if (!ns) {
ns = new_name_server (MDL);
if (!ns)
log_fatal ("No memory for nameserver %s",
piaddr (iaddr));
ns -> next = (struct name_server *)0;
*sp = ns;
memcpy (&ns -> addr.sin_addr,
iaddr.iabuf, iaddr.len);
#ifdef HAVE_SA_LEN
ns -> addr.sin_len = sizeof ns -> addr;
#endif
ns -> addr.sin_family = AF_INET;
ns -> addr.sin_port = htons (53);
memset (ns -> addr.sin_zero, 0,
sizeof ns -> addr.sin_zero);
}
ns -> rcdate = parse_time;
skip_to_semi (cfile);
} else
skip_to_semi (cfile); /* Ignore what we don't grok. */
} while (1);
skip_token(&val, (unsigned *)0, cfile);
/* Lose servers that are no longer in /etc/resolv.conf. */
sl = (struct name_server *)0;
for (sp = name_servers; sp; sp = ns) {
ns = sp -> next;
if (sp -> rcdate != parse_time) {
if (sl)
sl -> next = sp -> next;
else
name_servers = sp -> next;
/* We can't actually free the name server structure,
because somebody might be hanging on to it. If
your /etc/resolv.conf file changes a lot, this
could be a noticeable memory leak. */
} else
sl = sp;
}
/* Lose domains that are no longer in /etc/resolv.conf. */
dl = (struct domain_search_list *)0;
for (dp = domains; dp; dp = nd) {
nd = dp -> next;
if (dp -> rcdate != parse_time) {
if (dl)
dl -> next = dp -> next;
else
domains = dp -> next;
free_domain_search_list (dp, MDL);
} else
dl = dp;
}
end_parse (&cfile);
}
/* Pick a name server from the /etc/resolv.conf file. */
struct name_server *first_name_server ()
{
static TIME rcdate;
struct stat st;
/* Check /etc/resolv.conf and reload it if it's changed. */
if (cur_time > rcdate) {
if (stat (path_resolv_conf, &st) < 0) {
log_error ("Can't stat %s", path_resolv_conf);
return (struct name_server *)0;
}
if (st.st_mtime > rcdate) {
rcdate = cur_time + 1;
read_resolv_conf (rcdate);
}
}
return name_servers;
}
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