2.11BSD/src/lib/libc/net/res_send.c
/*
* Copyright (c) 1985 Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms are permitted
* provided that this notice is preserved and that due credit is given
* to the University of California at Berkeley. The name of the University
* may not be used to endorse or promote products derived from this
* software without specific prior written permission. This software
* is provided ``as is'' without express or implied warranty.
*/
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)res_send.c 6.19.1 (Berkeley) 6/27/94";
#endif /* LIBC_SCCS and not lint */
/*
* 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 <netinet/in.h>
#include <stdio.h>
#include <errno.h>
#include <arpa/nameser.h>
#include <resolv.h>
extern int errno;
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)))
#define FD_ZERO(p) bzero((char *)(p), sizeof(*(p)))
#endif
#define KEEPOPEN (RES_USEVC|RES_STAYOPEN)
res_send(buf, buflen, answer, anslen)
char *buf;
int buflen;
char *answer;
int anslen;
{
register int n;
int retry, v_circuit, resplen, ns;
int gotsomewhere = 0, connected = 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[16];
#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;
id = hp->id;
/*
* Send request, RETRY times, or until successful
*/
for (retry = _res.retry; retry > 0; retry--) {
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 DEBUG
if (v_circuit) {
int truncated = 0;
/*
* Use virtual circuit.
*/
if (s < 0) {
s = socket(AF_INET, SOCK_STREAM, 0);
if (s < 0) {
terrno = errno;
#ifdef DEBUG
if (_res.options & RES_DEBUG)
perror("socket failed");
#endif DEBUG
continue;
}
if (connect(s, &(_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 = 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;
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 {
/*
* Use datagrams.
*/
if (s < 0)
s = socket(AF_INET, SOCK_DGRAM, 0);
#if BSD >= 43
if (_res.nscount == 1 || retry == _res.retry) {
/*
* Don't use connect if we might
* still receive a response
* from another server.
*/
if (connected == 0) {
if (connect(s, &_res.nsaddr_list[ns],
sizeof(struct sockaddr)) < 0) {
#ifdef DEBUG
if (_res.options & RES_DEBUG)
perror("connect");
#endif DEBUG
continue;
}
connected = 1;
}
if (send(s, buf, buflen, 0) != buflen) {
#ifdef DEBUG
if (_res.options & RES_DEBUG)
perror("send");
#endif DEBUG
continue;
}
} else
#endif BSD
if (sendto(s, buf, buflen, 0, &_res.nsaddr_list[ns],
sizeof(struct sockaddr)) != buflen) {
#ifdef DEBUG
if (_res.options & RES_DEBUG)
perror("sendto");
#endif DEBUG
continue;
}
/*
* Wait for reply
*/
timeout.tv_sec = (_res.retrans << (_res.retry - retry))
/ _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 DEBUG
continue;
}
if (n == 0) {
/*
* timeout
*/
#ifdef DEBUG
if (_res.options & RES_DEBUG)
printf("timeout\n");
#endif DEBUG
/*
* Disconnect if we want to listen
* for responses from more than one server.
*/
if (_res.nscount > 1 && connected) {
(void) connect(s, &no_addr,
sizeof(no_addr));
connected = 0;
}
gotsomewhere = 1;
continue;
}
if ((resplen = recv(s, answer, anslen, 0)) <= 0) {
#ifdef DEBUG
if (_res.options & RES_DEBUG)
perror("recvfrom");
#endif DEBUG
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 DEBUG
goto wait;
}
if (!(_res.options & RES_IGNTC) && anhp->tc) {
/*
* get rest of answer
*/
#ifdef DEBUG
if (_res.options & RES_DEBUG)
printf("truncated answer\n");
#endif DEBUG
(void) close(s);
s = -1;
/*
* retry decremented on continue
* to desired starting value
*/
retry = _res.retry + 1;
v_circuit = 1;
continue;
}
}
#ifdef DEBUG
if (_res.options & RES_DEBUG) {
printf("got answer:\n");
p_query(answer);
}
#endif DEBUG
/*
* We are going to 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 ((_res.options & KEEPOPEN) == KEEPOPEN && ns == 0) {
return (resplen);
} else {
(void) close(s);
s = -1;
return (resplen);
}
}
}
if (s >= 0) {
(void) close(s);
s = -1;
}
if (v_circuit == 0)
if (gotsomewhere == 0)
errno = ECONNREFUSED;
else
errno = ETIMEDOUT;
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.
*/
_res_close()
{
if (s != -1) {
(void) close(s);
s = -1;
}
}