OpenSolaris_b135/lib/libresolv/res_send.c
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2008 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
/* Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/* All Rights Reserved */
/*
* University Copyright- Copyright (c) 1982, 1986, 1988
* The Regents of the University of California
* All Rights Reserved
*
* University Acknowledgment- Portions of this document are derived from
* software developed by the University of California, Berkeley, and its
* contributors.
*/
#pragma ident "%Z%%M% %I% %E% SMI"
/*
* Send query to name server and wait for reply.
*/
#include <sys/param.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <sys/uio.h>
#include <sys/stat.h>
#include <netinet/in.h>
#include <stdio.h>
#include <errno.h>
#include <arpa/nameser.h>
#include <resolv.h>
static int s = -1; /* socket used for communications */
static struct sockaddr no_addr;
#ifndef FD_SET
#define NFDBITS 32
#define FD_SETSIZE 32
#define FD_SET(n, p) ((p)->fds_bits[(n)/NFDBITS] |= (1 << ((n) % NFDBITS)))
#define FD_CLR(n, p) ((p)->fds_bits[(n)/NFDBITS] &= ~(1 << ((n) % NFDBITS)))
#define FD_ISSET(n, p) ((p)->fds_bits[(n)/NFDBITS] & (1 << ((n) % NFDBITS)))
#ifdef SYSV
#define FD_ZERO(p) memset((void *)(p), 0, sizeof (*(p)))
#else
#define FD_ZERO(p) bzero((char *)(p), sizeof (*(p)))
#endif
#endif
/*
* 1247019: Kludge to time out quickly if there is no /etc/resolv.conf
* and a TCP connection to the local DNS server fails.
*/
static int _confcheck()
{
int ns;
struct stat rc_stat;
struct sockaddr_in ns_sin;
/* First, we check to see if /etc/resolv.conf exists.
* If it doesn't, then localhost is mostlikely to be
* the nameserver.
*/
if (stat(_PATH_RESCONF, &rc_stat) == -1 && errno == ENOENT) {
/* Next, we check to see if _res.nsaddr is set to loopback.
* If it isn't, it has been altered by the application
* explicitly and we then want to bail with success.
*/
if (_res.nsaddr.sin_addr.S_un.S_addr == htonl(INADDR_LOOPBACK)) {
/* Lastly, we try to connect to the TCP port of the
* nameserver. If this fails, then we know that
* DNS is misconfigured and we can quickly exit.
*/
ns = socket(AF_INET, SOCK_STREAM, 0);
IN_SET_LOOPBACK_ADDR(&ns_sin);
ns_sin.sin_port = htons(NAMESERVER_PORT);
if (connect(ns, (struct sockaddr *) &ns_sin,
sizeof ns_sin) == -1) {
close(ns);
return(-1);
}
else {
close(ns);
return(0);
}
}
return(0);
}
return (0);
}
int
res_send(buf, buflen, answer, anslen)
char *buf;
int buflen;
char *answer;
int anslen;
{
register int n;
int try, v_circuit, resplen, ns;
int gotsomewhere = 0, connected = 0;
int connreset = 0;
u_short id, len;
char *cp;
fd_set dsmask;
struct timeval timeout;
HEADER *hp = (HEADER *) buf;
HEADER *anhp = (HEADER *) answer;
struct iovec iov[2];
int terrno = ETIMEDOUT;
char junk[512];
#ifdef DEBUG
if (_res.options & RES_DEBUG) {
printf("res_send()\n");
p_query(buf);
}
#endif
if (!(_res.options & RES_INIT))
if (res_init() == -1) {
return (-1);
}
/* 1247019: Check to see if we can bailout quickly. */
if (_confcheck() == -1)
return(-1);
v_circuit = (_res.options & RES_USEVC) || buflen > PACKETSZ;
id = hp->id;
/*
* Send request, RETRY times, or until successful
*/
for (try = 0; try < _res.retry; try++) {
for (ns = 0; ns < _res.nscount; ns++) {
#ifdef DEBUG
if (_res.options & RES_DEBUG)
printf("Querying server (# %d) address = %s\n",
ns+1, inet_ntoa(_res.nsaddr_list[ns].sin_addr));
#endif
usevc:
if (v_circuit) {
int truncated = 0;
/*
* Use virtual circuit;
* at most one attempt per server.
*/
try = _res.retry;
if (s < 0) {
s = _socket(AF_INET, SOCK_STREAM, 0);
if (s < 0) {
terrno = errno;
#ifdef DEBUG
if (_res.options & RES_DEBUG) {
perror("socket (vc) failed");
}
#endif
continue;
}
if (connect(s, (struct sockaddr *) &_res.nsaddr_list[ns],
sizeof (struct sockaddr)) < 0) {
terrno = errno;
#ifdef DEBUG
if (_res.options & RES_DEBUG) {
perror("connect failed");
}
#endif
(void) close(s);
s = -1;
continue;
}
}
/*
* Send length & message
*/
len = htons((u_short)buflen);
iov[0].iov_base = (caddr_t)&len;
iov[0].iov_len = sizeof (len);
iov[1].iov_base = buf;
iov[1].iov_len = buflen;
if (writev(s, iov, 2) != sizeof (len) +
buflen) {
terrno = errno;
#ifdef DEBUG
if (_res.options & RES_DEBUG)
perror("write failed");
#endif
(void) close(s);
s = -1;
continue;
}
/*
* Receive length & response
*/
cp = answer;
len = sizeof (short);
while (len != 0 && (n = read
(s, (char *)cp, (int)len)) > 0) {
cp += n;
len -= n;
}
if (n <= 0) {
terrno = errno;
#ifdef DEBUG
if (_res.options & RES_DEBUG)
perror("read failed");
#endif
(void) close(s);
s = -1;
/*
* A long running process might get its TCP
* connection reset if the remote server was
* restarted. Requery the server instead of
* trying a new one. When there is only one
* server, this means that a query might work
* instead of failing. We only allow one reset
* per query to prevent looping.
*/
if (terrno == ECONNRESET &&
!connreset) {
connreset = 1;
ns--;
}
continue;
}
cp = answer;
if ((resplen = ntohs(*(u_short *)cp)) >
anslen) {
#ifdef DEBUG
if (_res.options & RES_DEBUG)
fprintf(stderr,
"response truncated\n");
#endif
len = anslen;
truncated = 1;
} else
len = resplen;
while (len != 0 &&
(n = read(s, (char *)cp,
(int)len)) > 0) {
cp += n;
len -= n;
}
if (n <= 0) {
terrno = errno;
#ifdef DEBUG
if (_res.options & RES_DEBUG)
perror("read failed");
#endif
(void) close(s);
s = -1;
continue;
}
if (truncated) {
/*
* Flush rest of answer
* so connection stays in synch.
*/
anhp->tc = 1;
len = resplen - anslen;
/*
* set the value of resplen to anslen,
* this is done because the caller
* assumes resplen contains the size of
* message read into the "answer" buffer
* passed in.
*/
resplen = anslen;
while (len != 0) {
n = (len > sizeof (junk) ?
sizeof (junk) : len);
if ((n = read(s, junk, n)) > 0)
len -= n;
else
break;
}
}
} else {
/*
* Use datagrams.
*/
if (s < 0) {
s = _socket(AF_INET, SOCK_DGRAM, 0);
if (s < 0) {
terrno = errno;
#ifdef DEBUG
if (_res.options & RES_DEBUG) {
perror("socket (dg) failed");
}
#endif
continue;
}
}
#if BSD >= 43
/*
* I'm tired of answering this question, so:
* On a 4.3BSD+ machine (client and server,
* actually), sending to a nameserver datagram
* port with no nameserver will cause an
* ICMP port unreachable message to be returned.
* If our datagram socket is "connected" to the
* server, we get an ECONNREFUSED error on the next
* socket operation, and select returns if the
* error message is received. We can thus detect
* the absence of a nameserver without timing out.
* If we have sent queries to at least two servers,
* however, we don't want to remain connected,
* as we wish to receive answers from the first
* server to respond.
*/
if (_res.nscount == 1 ||
(try == 0 && ns == 0)) {
/*
* Don't use connect if we might
* still receive a response
* from another server.
*/
if (connected == 0) {
if (connect(s,
(struct sockaddr *) &_res.nsaddr_list[ns],
sizeof (struct sockaddr)) < 0) {
#ifdef DEBUG
if (_res.options &
RES_DEBUG) {
perror("connect");
}
#endif
continue;
}
connected = 1;
}
if (send(s, buf, buflen, 0) != buflen) {
#ifdef DEBUG
if (_res.options & RES_DEBUG)
perror("send");
#endif
continue;
}
} else {
/*
* Disconnect if we want to listen for
* responses from more than one server.
*/
if (connected) {
(void) connect(s, &no_addr,
sizeof (no_addr));
connected = 0;
}
#endif /* BSD */
if (sendto(s, buf, buflen, 0,
(struct sockaddr *) &_res.nsaddr_list[ns],
sizeof (struct sockaddr)) != buflen) {
#ifdef DEBUG
if (_res.options & RES_DEBUG)
perror("sendto");
#endif
continue;
}
#if BSD >= 43
}
#endif
/*
* Wait for reply
*/
timeout.tv_sec = (_res.retrans << try);
if (try > 0)
timeout.tv_sec /= _res.nscount;
if (timeout.tv_sec <= 0)
timeout.tv_sec = 1;
timeout.tv_usec = 0;
wait:
FD_ZERO(&dsmask);
FD_SET(s, &dsmask);
n = select(s+1, &dsmask, (fd_set *)NULL,
(fd_set *)NULL, &timeout);
if (n < 0) {
#ifdef DEBUG
if (_res.options & RES_DEBUG)
perror("select");
#endif
continue;
}
if (n == 0) {
/*
* timeout
*/
#ifdef DEBUG
if (_res.options & RES_DEBUG)
printf("timeout\n");
#endif
#if BSD >= 43
gotsomewhere = 1;
#endif
continue;
}
if ((resplen = recv(s, answer, anslen, 0))
<= 0) {
#ifdef DEBUG
if (_res.options & RES_DEBUG)
perror("recvfrom");
#endif
continue;
}
gotsomewhere = 1;
if (id != anhp->id) {
/*
* response from old query, ignore it
*/
#ifdef DEBUG
if (_res.options & RES_DEBUG) {
printf("old answer:\n");
p_query(answer);
}
#endif
goto wait;
}
if (!(_res.options & RES_IGNTC) && anhp->tc) {
/*
* get rest of answer;
* use TCP with same server.
*/
#ifdef DEBUG
if (_res.options & RES_DEBUG)
printf("truncated answer\n");
#endif
(void) close(s);
s = -1;
v_circuit = 1;
goto usevc;
}
}
#ifdef DEBUG
if (_res.options & RES_DEBUG) {
printf("got answer:\n");
p_query(answer);
}
#endif
/*
* If using virtual circuits, we assume that the first server
* is preferred * over the rest (i.e. it is on the local
* machine) and only keep that one open.
* If we have temporarily opened a virtual circuit,
* or if we haven't been asked to keep a socket open,
* close the socket.
*/
if ((v_circuit &&
((_res.options & RES_USEVC) == 0 || ns != 0)) ||
(_res.options & RES_STAYOPEN) == 0) {
(void) close(s);
s = -1;
}
return (resplen);
}
}
if (s >= 0) {
(void) close(s);
s = -1;
}
if (v_circuit == 0)
if (gotsomewhere == 0)
errno = ECONNREFUSED; /* no nameservers found */
else
errno = ETIMEDOUT; /* no answer obtained */
else
errno = terrno;
return (-1);
}
/*
* 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_close()
{
if (s != -1) {
(void) close(s);
s = -1;
}
}