432 lines
11 KiB
C
432 lines
11 KiB
C
/*
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* Copyright (c) 1985, 1989 Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#if defined(LIBC_SCCS) && !defined(lint)
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static char sccsid[] = "@(#)res_send.c 6.27 (Berkeley) 2/24/91";
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#endif /* LIBC_SCCS and not lint */
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/*
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* Send query to name server and wait for reply.
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*/
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#include <sys/param.h>
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#include <sys/time.h>
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#include <sys/socket.h>
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#include <sys/uio.h>
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#include <netinet/in.h>
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#include <arpa/nameser.h>
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#include <stdio.h>
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#include <errno.h>
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#include <resolv.h>
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#include <unistd.h>
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#include <string.h>
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static int s = -1; /* socket used for communications */
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static struct sockaddr no_addr;
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#ifndef FD_SET
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#define NFDBITS 32
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#define FD_SETSIZE 32
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#define FD_SET(n, p) ((p)->fds_bits[(n)/NFDBITS] |= (1 << ((n) % NFDBITS)))
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#define FD_CLR(n, p) ((p)->fds_bits[(n)/NFDBITS] &= ~(1 << ((n) % NFDBITS)))
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#define FD_ISSET(n, p) ((p)->fds_bits[(n)/NFDBITS] & (1 << ((n) % NFDBITS)))
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#define FD_ZERO(p) bzero((char *)(p), sizeof(*(p)))
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#endif
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res_send(buf, buflen, answer, anslen)
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const char *buf;
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int buflen;
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char *answer;
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int anslen;
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{
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register int n;
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int try, v_circuit, resplen, ns;
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int gotsomewhere = 0, connected = 0;
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int connreset = 0;
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u_short id, len;
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char *cp;
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fd_set dsmask;
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struct timeval timeout;
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HEADER *hp = (HEADER *) buf;
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HEADER *anhp = (HEADER *) answer;
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struct iovec iov[2];
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int terrno = ETIMEDOUT;
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char junk[512];
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#ifdef DEBUG
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if (_res.options & RES_DEBUG) {
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printf("res_send()\n");
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__p_query(buf);
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}
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#endif DEBUG
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if (!(_res.options & RES_INIT))
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if (res_init() == -1) {
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return(-1);
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}
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v_circuit = (_res.options & RES_USEVC) || buflen > PACKETSZ;
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id = hp->id;
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/*
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* Send request, RETRY times, or until successful
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*/
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for (try = 0; try < _res.retry; try++) {
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for (ns = 0; ns < _res.nscount; ns++) {
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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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printf("Querying server (# %d) address = %s\n", ns+1,
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inet_ntoa(_res.nsaddr_list[ns].sin_addr));
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#endif DEBUG
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usevc:
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if (v_circuit) {
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int truncated = 0;
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/*
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* Use virtual circuit;
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* at most one attempt per server.
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*/
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try = _res.retry;
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if (s < 0) {
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s = socket(AF_INET, SOCK_STREAM, 0);
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if (s < 0) {
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terrno = errno;
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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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perror("socket (vc) failed");
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#endif DEBUG
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continue;
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}
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if (connect(s,
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(struct sockaddr *)&(_res.nsaddr_list[ns]),
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sizeof(struct sockaddr)) < 0) {
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terrno = errno;
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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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perror("connect failed");
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#endif DEBUG
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(void) close(s);
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s = -1;
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continue;
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}
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}
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/*
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* Send length & message
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*/
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len = htons((u_short)buflen);
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iov[0].iov_base = (caddr_t)&len;
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iov[0].iov_len = sizeof(len);
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iov[1].iov_base = (char *)buf;
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iov[1].iov_len = buflen;
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if (writev(s, iov, 2) != sizeof(len) + buflen) {
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terrno = errno;
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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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perror("write failed");
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#endif DEBUG
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(void) close(s);
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s = -1;
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continue;
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}
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/*
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* Receive length & response
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*/
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cp = answer;
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len = sizeof(short);
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while (len != 0 &&
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(n = read(s, (char *)cp, (int)len)) > 0) {
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cp += n;
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len -= n;
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}
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if (n <= 0) {
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terrno = errno;
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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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perror("read failed");
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#endif DEBUG
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(void) close(s);
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s = -1;
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/*
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* A long running process might get its TCP
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* connection reset if the remote server was
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* restarted. Requery the server instead of
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* trying a new one. When there is only one
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* server, this means that a query might work
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* instead of failing. We only allow one reset
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* per query to prevent looping.
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*/
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if (terrno == ECONNRESET && !connreset) {
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connreset = 1;
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ns--;
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}
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continue;
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}
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cp = answer;
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if ((resplen = ntohs(*(u_short *)cp)) > anslen) {
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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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fprintf(stderr, "response truncated\n");
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#endif DEBUG
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len = anslen;
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truncated = 1;
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} else
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len = resplen;
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while (len != 0 &&
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(n = read(s, (char *)cp, (int)len)) > 0) {
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cp += n;
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len -= n;
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}
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if (n <= 0) {
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terrno = errno;
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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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perror("read failed");
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#endif DEBUG
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(void) close(s);
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s = -1;
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continue;
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}
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if (truncated) {
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/*
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* Flush rest of answer
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* so connection stays in synch.
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*/
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anhp->tc = 1;
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len = resplen - anslen;
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while (len != 0) {
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n = (len > sizeof(junk) ?
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sizeof(junk) : len);
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if ((n = read(s, junk, n)) > 0)
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len -= n;
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else
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break;
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}
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}
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} else {
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/*
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* Use datagrams.
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*/
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if (s < 0) {
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s = socket(AF_INET, SOCK_DGRAM, 0);
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if (s < 0) {
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terrno = errno;
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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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perror("socket (dg) failed");
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#endif DEBUG
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continue;
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}
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}
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#if BSD >= 43
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/*
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* I'm tired of answering this question, so:
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* On a 4.3BSD+ machine (client and server,
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* actually), sending to a nameserver datagram
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* port with no nameserver will cause an
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* ICMP port unreachable message to be returned.
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* If our datagram socket is "connected" to the
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* server, we get an ECONNREFUSED error on the next
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* socket operation, and select returns if the
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* error message is received. We can thus detect
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* the absence of a nameserver without timing out.
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* If we have sent queries to at least two servers,
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* however, we don't want to remain connected,
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* as we wish to receive answers from the first
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* server to respond.
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*/
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if (_res.nscount == 1 || (try == 0 && ns == 0)) {
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/*
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* Don't use connect if we might
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* still receive a response
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* from another server.
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*/
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if (connected == 0) {
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if (connect(s, (struct sockaddr *)&_res.nsaddr_list[ns],
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sizeof(struct sockaddr)) < 0) {
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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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perror("connect");
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#endif DEBUG
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continue;
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}
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connected = 1;
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}
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if (send(s, buf, buflen, 0) != buflen) {
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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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perror("send");
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#endif DEBUG
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continue;
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}
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} else {
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/*
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* Disconnect if we want to listen
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* for responses from more than one server.
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*/
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if (connected) {
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(void) connect(s, &no_addr,
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sizeof(no_addr));
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connected = 0;
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}
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#endif BSD
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if (sendto(s, buf, buflen, 0,
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(struct sockaddr *)&_res.nsaddr_list[ns],
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sizeof(struct sockaddr)) != buflen) {
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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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perror("sendto");
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#endif DEBUG
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continue;
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}
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#if BSD >= 43
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}
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#endif
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/*
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* Wait for reply
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*/
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timeout.tv_sec = (_res.retrans << try);
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if (try > 0)
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timeout.tv_sec /= _res.nscount;
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if (timeout.tv_sec <= 0)
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timeout.tv_sec = 1;
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timeout.tv_usec = 0;
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wait:
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FD_ZERO(&dsmask);
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FD_SET(s, &dsmask);
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n = select(s+1, &dsmask, (fd_set *)NULL,
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(fd_set *)NULL, &timeout);
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if (n < 0) {
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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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perror("select");
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#endif DEBUG
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continue;
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}
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if (n == 0) {
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/*
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* timeout
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*/
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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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printf("timeout\n");
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#endif DEBUG
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#if BSD >= 43
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gotsomewhere = 1;
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#endif
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continue;
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}
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if ((resplen = recv(s, answer, anslen, 0)) <= 0) {
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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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perror("recvfrom");
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#endif DEBUG
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continue;
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}
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gotsomewhere = 1;
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if (id != anhp->id) {
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/*
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* response from old query, ignore it
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*/
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#ifdef DEBUG
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if (_res.options & RES_DEBUG) {
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printf("old answer:\n");
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__p_query(answer);
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}
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#endif DEBUG
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goto wait;
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}
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if (!(_res.options & RES_IGNTC) && anhp->tc) {
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/*
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* get rest of answer;
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* use TCP with same server.
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*/
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#ifdef DEBUG
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if (_res.options & RES_DEBUG)
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printf("truncated answer\n");
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#endif DEBUG
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(void) close(s);
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s = -1;
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v_circuit = 1;
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goto usevc;
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}
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}
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#ifdef DEBUG
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if (_res.options & RES_DEBUG) {
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printf("got answer:\n");
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__p_query(answer);
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}
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#endif DEBUG
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/*
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* If using virtual circuits, we assume that the first server
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* is preferred * over the rest (i.e. it is on the local
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* machine) and only keep that one open.
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* If we have temporarily opened a virtual circuit,
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* or if we haven't been asked to keep a socket open,
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* close the socket.
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*/
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if ((v_circuit &&
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((_res.options & RES_USEVC) == 0 || ns != 0)) ||
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(_res.options & RES_STAYOPEN) == 0) {
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(void) close(s);
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s = -1;
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}
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return (resplen);
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}
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}
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if (s >= 0) {
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(void) close(s);
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s = -1;
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}
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if (v_circuit == 0)
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if (gotsomewhere == 0)
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errno = ECONNREFUSED; /* no nameservers found */
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else
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errno = ETIMEDOUT; /* no answer obtained */
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else
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errno = terrno;
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return (-1);
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}
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/*
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* This routine is for closing the socket if a virtual circuit is used and
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* the program wants to close it. This provides support for endhostent()
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* which expects to close the socket.
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*
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* This routine is not expected to be user visible.
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*/
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_res_close()
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{
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if (s != -1) {
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(void) close(s);
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s = -1;
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}
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}
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