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glibc/resolv/res_init.c
Ulrich Drepper 44d20bca52 Implement second fallback mode for DNS requests. 
There is some more shardware/software out there which has problems
if two DNS requests are sent using the same tuple

  (source addr, source port, dest addr, dest port)

This can range from firewalls to load balancers.  Some of the vendors
already fixed it in response to this problem.  Still, we need a way
to make glibc work with broken environments.  The single-request-reopen
flag can be used or we fall back automatically to this mode.
2009-06-26 03:47:47 -07:00

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/*
* Copyright (c) 1985, 1989, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* Portions Copyright (c) 1993 by Digital Equipment Corporation.
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies, and that
* the name of Digital Equipment Corporation not be used in advertising or
* publicity pertaining to distribution of the document or software without
* specific, written prior permission.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
* WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL DIGITAL EQUIPMENT
* CORPORATION 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.
*/
/*
* Portions Copyright (c) 1996-1999 by Internet Software Consortium.
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
* ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
* CONSORTIUM 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.
*/
#if defined(LIBC_SCCS) && !defined(lint)
static const char sccsid[] = "@(#)res_init.c 8.1 (Berkeley) 6/7/93";
static const char rcsid[] = "$BINDId: res_init.c,v 8.16 2000/05/09 07:10:12 vixie Exp $";
#endif /* LIBC_SCCS and not lint */
#include <ctype.h>
#include <netdb.h>
#include <resolv.h>
#include <stdio.h>
#include <stdio_ext.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <net/if.h>
#include <netinet/in.h>
#include <sys/param.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/types.h>
#include <not-cancel.h>
/* Options. Should all be left alone. */
#define RESOLVSORT
#define RFC1535
/* #undef DEBUG */
static void res_setoptions (res_state, const char *, const char *)
internal_function;
#ifdef RESOLVSORT
static const char sort_mask_chars[] = "/&";
#define ISSORTMASK(ch) (strchr(sort_mask_chars, ch) != NULL)
static u_int32_t net_mask (struct in_addr) __THROW;
#endif
#if !defined(isascii) /* XXX - could be a function */
# define isascii(c) (!(c & 0200))
#endif
#ifdef _LIBC
unsigned long long int __res_initstamp attribute_hidden;
#endif
/*
* Resolver state default settings.
*/
/*
* Set up default settings. If the configuration file exist, the values
* there will have precedence. Otherwise, the server address is set to
* INADDR_ANY and the default domain name comes from the gethostname().
*
* An interrim version of this code (BIND 4.9, pre-4.4BSD) used 127.0.0.1
* rather than INADDR_ANY ("0.0.0.0") as the default name server address
* since it was noted that INADDR_ANY actually meant ``the first interface
* you "ifconfig"'d at boot time'' and if this was a SLIP or PPP interface,
* it had to be "up" in order for you to reach your own name server. It
* was later decided that since the recommended practice is to always
* install local static routes through 127.0.0.1 for all your network
* interfaces, that we could solve this problem without a code change.
*
* The configuration file should always be used, since it is the only way
* to specify a default domain. If you are running a server on your local
* machine, you should say "nameserver 0.0.0.0" or "nameserver 127.0.0.1"
* in the configuration file.
*
* Return 0 if completes successfully, -1 on error
*/
int
res_ninit(res_state statp) {
extern int __res_vinit(res_state, int);
return (__res_vinit(statp, 0));
}
#ifdef _LIBC
libc_hidden_def (__res_ninit)
#endif
/* This function has to be reachable by res_data.c but not publically. */
int
__res_vinit(res_state statp, int preinit) {
register FILE *fp;
register char *cp, **pp;
register int n;
char buf[BUFSIZ];
int nserv = 0; /* number of nameserver records read from file */
#ifdef _LIBC
int nservall = 0; /* number of NS records read, nserv IPv4 only */
#endif
int haveenv = 0;
int havesearch = 0;
#ifdef RESOLVSORT
int nsort = 0;
char *net;
#endif
#ifndef RFC1535
int dots;
#endif
#ifdef _LIBC
statp->_u._ext.initstamp = __res_initstamp;
#endif
if (!preinit) {
statp->retrans = RES_TIMEOUT;
statp->retry = RES_DFLRETRY;
statp->options = RES_DEFAULT;
statp->id = res_randomid();
}
#ifdef USELOOPBACK
statp->nsaddr.sin_addr = inet_makeaddr(IN_LOOPBACKNET, 1);
#else
statp->nsaddr.sin_addr.s_addr = INADDR_ANY;
#endif
statp->nsaddr.sin_family = AF_INET;
statp->nsaddr.sin_port = htons(NAMESERVER_PORT);
statp->nscount = 0;
statp->ndots = 1;
statp->pfcode = 0;
statp->_vcsock = -1;
statp->_flags = 0;
statp->qhook = NULL;
statp->rhook = NULL;
statp->_u._ext.nsinit = 0;
statp->_u._ext.nscount = 0;
#ifdef _LIBC
statp->_u._ext.nscount6 = 0;
for (n = 0; n < MAXNS; n++) {
statp->_u._ext.nsaddrs[n] = NULL;
statp->_u._ext.nsmap[n] = MAXNS;
}
#endif
/* Allow user to override the local domain definition */
if ((cp = getenv("LOCALDOMAIN")) != NULL) {
(void)strncpy(statp->defdname, cp, sizeof(statp->defdname) - 1);
statp->defdname[sizeof(statp->defdname) - 1] = '\0';
haveenv++;
/*
* Set search list to be blank-separated strings
* from rest of env value. Permits users of LOCALDOMAIN
* to still have a search list, and anyone to set the
* one that they want to use as an individual (even more
* important now that the rfc1535 stuff restricts searches)
*/
cp = statp->defdname;
pp = statp->dnsrch;
*pp++ = cp;
for (n = 0; *cp && pp < statp->dnsrch + MAXDNSRCH; cp++) {
if (*cp == '\n') /* silly backwards compat */
break;
else if (*cp == ' ' || *cp == '\t') {
*cp = 0;
n = 1;
} else if (n) {
*pp++ = cp;
n = 0;
havesearch = 1;
}
}
/* null terminate last domain if there are excess */
while (*cp != '\0' && *cp != ' ' && *cp != '\t' && *cp != '\n')
cp++;
*cp = '\0';
*pp++ = 0;
}
#define MATCH(line, name) \
(!strncmp(line, name, sizeof(name) - 1) && \
(line[sizeof(name) - 1] == ' ' || \
line[sizeof(name) - 1] == '\t'))
if ((fp = fopen(_PATH_RESCONF, "rc")) != NULL) {
/* No threads use this stream. */
__fsetlocking (fp, FSETLOCKING_BYCALLER);
/* read the config file */
while (fgets_unlocked(buf, sizeof(buf), fp) != NULL) {
/* skip comments */
if (*buf == ';' || *buf == '#')
continue;
/* read default domain name */
if (MATCH(buf, "domain")) {
if (haveenv) /* skip if have from environ */
continue;
cp = buf + sizeof("domain") - 1;
while (*cp == ' ' || *cp == '\t')
cp++;
if ((*cp == '\0') || (*cp == '\n'))
continue;
strncpy(statp->defdname, cp, sizeof(statp->defdname) - 1);
statp->defdname[sizeof(statp->defdname) - 1] = '\0';
if ((cp = strpbrk(statp->defdname, " \t\n")) != NULL)
*cp = '\0';
havesearch = 0;
continue;
}
/* set search list */
if (MATCH(buf, "search")) {
if (haveenv) /* skip if have from environ */
continue;
cp = buf + sizeof("search") - 1;
while (*cp == ' ' || *cp == '\t')
cp++;
if ((*cp == '\0') || (*cp == '\n'))
continue;
strncpy(statp->defdname, cp, sizeof(statp->defdname) - 1);
statp->defdname[sizeof(statp->defdname) - 1] = '\0';
if ((cp = strchr(statp->defdname, '\n')) != NULL)
*cp = '\0';
/*
* Set search list to be blank-separated strings
* on rest of line.
*/
cp = statp->defdname;
pp = statp->dnsrch;
*pp++ = cp;
for (n = 0; *cp && pp < statp->dnsrch + MAXDNSRCH; cp++) {
if (*cp == ' ' || *cp == '\t') {
*cp = 0;
n = 1;
} else if (n) {
*pp++ = cp;
n = 0;
}
}
/* null terminate last domain if there are excess */
while (*cp != '\0' && *cp != ' ' && *cp != '\t')
cp++;
*cp = '\0';
*pp++ = 0;
havesearch = 1;
continue;
}
/* read nameservers to query */
#ifdef _LIBC
if (MATCH(buf, "nameserver") && nservall < MAXNS) {
#else
if (MATCH(buf, "nameserver") && nserv < MAXNS) {
#endif
struct in_addr a;
cp = buf + sizeof("nameserver") - 1;
while (*cp == ' ' || *cp == '\t')
cp++;
if ((*cp != '\0') && (*cp != '\n')
&& __inet_aton(cp, &a)) {
statp->nsaddr_list[nservall].sin_addr = a;
statp->nsaddr_list[nservall].sin_family = AF_INET;
statp->nsaddr_list[nservall].sin_port =
htons(NAMESERVER_PORT);
nserv++;
#ifdef _LIBC
nservall++;
} else {
struct in6_addr a6;
char *el;
if ((el = strchr(cp, '\n')) != NULL)
*el = '\0';
if ((el = strchr(cp, SCOPE_DELIMITER)) != NULL)
*el = '\0';
if ((*cp != '\0') &&
(inet_pton(AF_INET6, cp, &a6) > 0)) {
struct sockaddr_in6 *sa6;
sa6 = malloc(sizeof(*sa6));
if (sa6 != NULL) {
sa6->sin6_family = AF_INET6;
sa6->sin6_port = htons(NAMESERVER_PORT);
sa6->sin6_flowinfo = 0;
sa6->sin6_addr = a6;
if (__builtin_expect (el == NULL, 1))
sa6->sin6_scope_id = 0;
else {
int try_numericscope = 1;
if (IN6_IS_ADDR_LINKLOCAL (&a6)
|| IN6_IS_ADDR_MC_LINKLOCAL (&a6)) {
sa6->sin6_scope_id
= if_nametoindex (el + 1);
if (sa6->sin6_scope_id != 0)
try_numericscope = 0;
}
if (try_numericscope) {
char *end;
sa6->sin6_scope_id
= (uint32_t) strtoul (el + 1, &end,
10);
if (*end != '\0')
sa6->sin6_scope_id = 0;
}
}
statp->_u._ext.nsaddrs[nservall] = sa6;
statp->_u._ext.nssocks[nservall] = -1;
statp->_u._ext.nsmap[nservall] = MAXNS + 1;
nservall++;
}
}
#endif
}
continue;
}
#ifdef RESOLVSORT
if (MATCH(buf, "sortlist")) {
struct in_addr a;
cp = buf + sizeof("sortlist") - 1;
while (nsort < MAXRESOLVSORT) {
while (*cp == ' ' || *cp == '\t')
cp++;
if (*cp == '\0' || *cp == '\n' || *cp == ';')
break;
net = cp;
while (*cp && !ISSORTMASK(*cp) && *cp != ';' &&
isascii(*cp) && !isspace(*cp))
cp++;
n = *cp;
*cp = 0;
if (__inet_aton(net, &a)) {
statp->sort_list[nsort].addr = a;
if (ISSORTMASK(n)) {
*cp++ = n;
net = cp;
while (*cp && *cp != ';' &&
isascii(*cp) && !isspace(*cp))
cp++;
n = *cp;
*cp = 0;
if (__inet_aton(net, &a)) {
statp->sort_list[nsort].mask = a.s_addr;
} else {
statp->sort_list[nsort].mask =
net_mask(statp->sort_list[nsort].addr);
}
} else {
statp->sort_list[nsort].mask =
net_mask(statp->sort_list[nsort].addr);
}
nsort++;
}
*cp = n;
}
continue;
}
#endif
if (MATCH(buf, "options")) {
res_setoptions(statp, buf + sizeof("options") - 1, "conf");
continue;
}
}
statp->nscount = nservall;
#ifdef _LIBC
if (nservall - nserv > 0) {
statp->_u._ext.nscount6 = nservall - nserv;
/* We try IPv6 servers again. */
statp->ipv6_unavail = false;
}
#endif
#ifdef RESOLVSORT
statp->nsort = nsort;
#endif
(void) fclose(fp);
}
if (statp->defdname[0] == 0 &&
__gethostname(buf, sizeof(statp->defdname) - 1) == 0 &&
(cp = strchr(buf, '.')) != NULL)
strcpy(statp->defdname, cp + 1);
/* find components of local domain that might be searched */
if (havesearch == 0) {
pp = statp->dnsrch;
*pp++ = statp->defdname;
*pp = NULL;
#ifndef RFC1535
dots = 0;
for (cp = statp->defdname; *cp; cp++)
dots += (*cp == '.');
cp = statp->defdname;
while (pp < statp->dnsrch + MAXDFLSRCH) {
if (dots < LOCALDOMAINPARTS)
break;
cp = __rawmemchr(cp, '.') + 1; /* we know there is one */
*pp++ = cp;
dots--;
}
*pp = NULL;
#ifdef DEBUG
if (statp->options & RES_DEBUG) {
printf(";; res_init()... default dnsrch list:\n");
for (pp = statp->dnsrch; *pp; pp++)
printf(";;\t%s\n", *pp);
printf(";;\t..END..\n");
}
#endif
#endif /* !RFC1535 */
}
if ((cp = getenv("RES_OPTIONS")) != NULL)
res_setoptions(statp, cp, "env");
statp->options |= RES_INIT;
return (0);
}
static void
internal_function
res_setoptions(res_state statp, const char *options, const char *source) {
const char *cp = options;
int i;
#ifdef DEBUG
if (statp->options & RES_DEBUG)
printf(";; res_setoptions(\"%s\", \"%s\")...\n",
options, source);
#endif
while (*cp) {
/* skip leading and inner runs of spaces */
while (*cp == ' ' || *cp == '\t')
cp++;
/* search for and process individual options */
if (!strncmp(cp, "ndots:", sizeof("ndots:") - 1)) {
i = atoi(cp + sizeof("ndots:") - 1);
if (i <= RES_MAXNDOTS)
statp->ndots = i;
else
statp->ndots = RES_MAXNDOTS;
#ifdef DEBUG
if (statp->options & RES_DEBUG)
printf(";;\tndots=%d\n", statp->ndots);
#endif
} else if (!strncmp(cp, "timeout:", sizeof("timeout:") - 1)) {
i = atoi(cp + sizeof("timeout:") - 1);
if (i <= RES_MAXRETRANS)
statp->retrans = i;
else
statp->retrans = RES_MAXRETRANS;
} else if (!strncmp(cp, "attempts:", sizeof("attempts:") - 1)){
i = atoi(cp + sizeof("attempts:") - 1);
if (i <= RES_MAXRETRY)
statp->retry = i;
else
statp->retry = RES_MAXRETRY;
} else if (!strncmp(cp, "debug", sizeof("debug") - 1)) {
#ifdef DEBUG
if (!(statp->options & RES_DEBUG)) {
printf(";; res_setoptions(\"%s\", \"%s\")..\n",
options, source);
statp->options |= RES_DEBUG;
}
printf(";;\tdebug\n");
#endif
} else if (!strncmp(cp, "inet6", sizeof("inet6") - 1)) {
statp->options |= RES_USE_INET6;
} else if (!strncmp(cp, "ip6-bytestring",
sizeof("ip6-bytestring") - 1)) {
statp->options |= RES_USEBSTRING;
} else if (!strncmp(cp, "no-ip6-dotint",
sizeof("no-ip6-dotint") - 1)) {
statp->options |= RES_NOIP6DOTINT;
} else if (!strncmp(cp, "ip6-dotint",
sizeof("ip6-dotint") - 1)) {
statp->options &= ~RES_NOIP6DOTINT;
} else if (!strncmp(cp, "rotate", sizeof("rotate") - 1)) {
statp->options |= RES_ROTATE;
} else if (!strncmp(cp, "no-check-names",
sizeof("no-check-names") - 1)) {
statp->options |= RES_NOCHECKNAME;
} else if (!strncmp(cp, "edns0", sizeof("edns0") - 1)) {
statp->options |= RES_USE_EDNS0;
} else if (!strncmp(cp, "single-request-reopen",
sizeof("single-request-reopen") - 1)) {
statp->options |= RES_SNGLKUPREOP;
} else if (!strncmp(cp, "single-request",
sizeof("single-request") - 1)) {
statp->options |= RES_SNGLKUP;
} else {
/* XXX - print a warning here? */
}
/* skip to next run of spaces */
while (*cp && *cp != ' ' && *cp != '\t')
cp++;
}
}
#ifdef RESOLVSORT
/* XXX - should really support CIDR which means explicit masks always. */
static u_int32_t
net_mask(in) /* XXX - should really use system's version of this */
struct in_addr in;
{
register u_int32_t i = ntohl(in.s_addr);
if (IN_CLASSA(i))
return (htonl(IN_CLASSA_NET));
else if (IN_CLASSB(i))
return (htonl(IN_CLASSB_NET));
return (htonl(IN_CLASSC_NET));
}
#endif
u_int
res_randomid(void) {
return 0xffff & __getpid();
}
#ifdef _LIBC
libc_hidden_def (__res_randomid)
#endif
/*
* This routine is for closing the socket if a virtual circuit is used and
* the program wants to close it. This provides support for endhostent()
* which expects to close the socket.
*
* This routine is not expected to be user visible.
*/
void
__res_iclose(res_state statp, bool free_addr) {
int ns;
if (statp->_vcsock >= 0) {
close_not_cancel_no_status(statp->_vcsock);
statp->_vcsock = -1;
statp->_flags &= ~(RES_F_VC | RES_F_CONN);
}
#ifdef _LIBC
for (ns = 0; ns < MAXNS; ns++)
#else
for (ns = 0; ns < statp->_u._ext.nscount; ns++)
#endif
if (statp->_u._ext.nsaddrs[ns]) {
if (statp->_u._ext.nssocks[ns] != -1) {
close_not_cancel_no_status(statp->_u._ext.nssocks[ns]);
statp->_u._ext.nssocks[ns] = -1;
}
if (free_addr) {
free (statp->_u._ext.nsaddrs[ns]);
statp->_u._ext.nsaddrs[ns] = NULL;
}
}
statp->_u._ext.nsinit = 0;
}
libc_hidden_def (__res_iclose)
void
res_nclose(res_state statp)
{
__res_iclose (statp, true);
}
#ifdef _LIBC
libc_hidden_def (__res_nclose)
#endif
#ifdef _LIBC
# ifdef _LIBC_REENTRANT
/* This is called when a thread is exiting to free resources held in _res. */
static void __attribute__ ((section ("__libc_thread_freeres_fn")))
res_thread_freeres (void)
{
if (_res.nscount == 0)
/* Never called res_ninit. */
return;
__res_iclose (&_res, true); /* Close any VC sockets. */
/* Make sure we do a full re-initialization the next time. */
_res.options = 0;
}
text_set_element (__libc_thread_subfreeres, res_thread_freeres);
text_set_element (__libc_subfreeres, res_thread_freeres);
# endif
#endif
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