res_send.c

操作系统源代码

/*
 * Copyright (c) 1985, 1989 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 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.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)res_send.c	6.27 (Berkeley) 2/24/91";
#endif /* LIBC_SCCS and not lint */

/*
 * Send query to name server and wait for reply.
 */

#if !_MINIX
#include <sys/param.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <sys/uio.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <stdio.h>
#include <errno.h>
#include <resolv.h>
#include <unistd.h>
#include <string.h>

#else /* _MINIX */

#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <net/hton.h>

#include <net/netlib.h>
#include <net/gen/in.h>
#include <net/gen/inet.h>
#include <net/gen/netdb.h>
#include <net/gen/nameser.h>
#include <net/gen/resolv.h>
#include <net/gen/tcp.h>
#include <net/gen/tcp_io.h>
#include <net/gen/udp.h>
#include <net/gen/udp_hdr.h>
#include <net/gen/udp_io.h>

typedef u16_t u_short;

static int tcp_connect _ARGS(( ipaddr_t host, Tcpport_t port, int *terrno ));
static int tcpip_writeall _ARGS(( int fd, const char *buf, size_t siz ));
static int udp_connect _ARGS(( void ));
static int udp_sendto _ARGS(( int fd, const char *buf, unsigned buflen,
				ipaddr_t addr, Udpport_t port ));
static int udp_receive _ARGS(( int fd, char *buf, unsigned buflen,
				time_t timeout ));
static void alarm_handler _ARGS(( int sig ));

#endif /* !_MINIX */

static int s = -1;	/* socket used for communications */
#if !_MINIX
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)))
#define FD_ZERO(p)	bzero((char *)(p), sizeof(*(p)))
#endif /* FD_SET */
#endif /* _MINIX */

res_send(buf, buflen, answer, anslen)
	const 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;
#if !_MINIX
	u_short id, len;
#else /* _MINIX */
	u16_t id, len;
#endif /* !_MINIX */
	char *cp;
#if !_MINIX
	fd_set dsmask;
	struct timeval timeout;
	HEADER *hp = (HEADER *) buf;
	HEADER *anhp = (HEADER *) answer;
	struct iovec iov[2];
#else /* _MINIX */
	time_t timeout;
	dns_hdr_t *hp = (dns_hdr_t *) buf;
	dns_hdr_t *anhp = (dns_hdr_t *) answer;
#endif /* !_MINIX */
	int terrno = ETIMEDOUT;
	char junk[512];

#ifdef DEBUG
	if (_res.options & RES_DEBUG) {
		printf("res_send()\n");
		__p_query(buf);
	}
#endif /* DEBUG */
	if (!(_res.options & RES_INIT))
		if (res_init() == -1) {
			return(-1);
		}

	v_circuit = (_res.options & RES_USEVC) || buflen > PACKETSZ;
#if !_MINIX
	id = hp->id;
#else /* _MINIX */
	id = hp->dh_id;
#endif /* !_MINIX */
	/*
	 * Send request, RETRY times, or until successful
	 */
	for (try = 0; try < _res.retry; try++) {
	   for (ns = 0; ns < _res.nscount; ns++) {
#ifdef DEBUG
#if !_MINIX
		if (_res.options & RES_DEBUG)
			printf("Querying server (# %d) address = %s\n", ns+1,
			      inet_ntoa(_res.nsaddr_list[ns].sin_addr));
#else /* _MINIX */
		if (_res.options & RES_DEBUG)
			printf("Querying server (# %d) address = %s\n", ns+1,
			      inet_ntoa(_res.nsaddr_list[ns]));
#endif /* !_MINIX */
#endif /* DEBUG */
	usevc:
		if (v_circuit) {
#if !_MINIX
			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 /* DEBUG */
					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 /* DEBUG */
					(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 = (char *)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 /* DEBUG */
				(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 /* DEBUG */
				(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 /* DEBUG */
				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 /* DEBUG */
				(void) close(s);
				s = -1;
				continue;
			}
			if (truncated) {
				/*
				 * Flush rest of answer
				 * so connection stays in synch.
				 */
				anhp->tc = 1;
				len = resplen - anslen;
				while (len != 0) {
					n = (len > sizeof(junk) ?
					    sizeof(junk) : len);
					if ((n = read(s, junk, n)) > 0)
						len -= n;
					else
						break;
				}
			}
#else /* _MINIX */
			int truncated = 0;
			int nbytes;

			/*
			 * Use virtual circuit;
			 * at most one attempt per server.
			 */
			try = _res.retry;
			if (s < 0) 
			{
				s= tcp_connect(_res.nsaddr_list[ns],
					_res.nsport_list[ns], &terrno);
				if (s == -1)
					continue;
			}
			/*
			 * Send length & message
			 */
			len = htons((u_short)buflen);
			nbytes= tcpip_writeall(s, (char *)&len, 
				sizeof(len));
			if (nbytes != sizeof(len))
			{
				terrno= errno;
#ifdef DEBUG
				if (_res.options & RES_DEBUG)
					fprintf(stderr, "write failed: %s\n",
					strerror(terrno));
#endif /* DEBUG */
				close(s);
				s= -1;
				continue;
			}
			nbytes= tcpip_writeall(s, buf, buflen);
			if (nbytes != buflen)
			{
				terrno= errno;
#ifdef DEBUG
				if (_res.options & RES_DEBUG)
					fprintf(stderr, "write failed: %s\n",
					strerror(terrno));
#endif /* DEBUG */
				close(s);
				s= -1;
				continue;
			}
			/*
			 * Receive length & response
			 */
			cp = answer;
			len = sizeof(short);
			while (len != 0)
			{
				n = read(s, (char *)cp, (int)len);
				if (n <= 0)
					break;
				cp += n;
				assert(len >= n);
				len -= n;
			}
			if (len) {
				terrno = errno;
#ifdef DEBUG
				if (_res.options & RES_DEBUG)
					fprintf(stderr, "read failed: %s\n",
						strerror(terrno));
#endif /* DEBUG */
				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 /* DEBUG */
				len = anslen;
				truncated = 1;
			} else
				len = resplen;
			while (len != 0)
			{
				n= read(s, (char *)cp, (int)len);
				if (n <= 0)
					break;
				cp += n;
				assert(len >= n);
				len -= n;
			}
			if (len) {
				terrno = errno;
#ifdef DEBUG
				if (_res.options & RES_DEBUG)
					fprintf(stderr, "read failed: %s\n",
						strerror(terrno));
#endif /* DEBUG */
				close(s);
				s= -1;
				continue;
			}
			if (truncated) {
				/*
				 * Flush rest of answer
				 * so connection stays in synch.
				 */
				anhp->dh_flag1 |= DHF_TC;
				len = resplen - anslen;
				while (len != 0) {
					n = (len > sizeof(junk) ?
					    sizeof(junk) : len);
					n = read(s, junk, n);
					if (n <= 0)
					{
						assert(len >= n);
						len -= n;
					}
					else
						break;
				}
			}
#endif /* _MINIX */
		} else {
#if !_MINIX
			/*
			 * 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 /* DEBUG */
					continue;
				}
			}
#if	BSD >= 43
			/*
			 * I'm tired of answering this question, so:
			 * On a 4.3BSD+ machine (client and server,