InfoMagic Internet Tools 1993 July/Internet Tools.iso/RockRidge/ip/dns/host/send.c

C/C++ Source or Header | 1992-09-23 | 13.6 KB | 631 lines

/*
 * Copyright (c) 1985, 1989 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that: (1) source distributions retain this entire copyright
 * notice and comment, and (2) distributions including binaries display
 * the following acknowledgement:  ``This product includes software
 * developed by the University of California, Berkeley and its contributors''
 * in the documentation or other materials provided with the distribution
 * and in all advertising materials mentioning features or use of this
 * software. 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 ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#ifndef lint
static char Version[] = "@(#)send.c    [e-mail] (Eric Wassenaar) 920924";
#endif

#include <stdio.h>
#include <errno.h>
#include <setjmp.h>
#include <signal.h>
#include <sys/time.h>

#include <sys/param.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <resolv.h>

#define input            /* read-only input parameter */
#define output            /* modified output parameter */

#if defined(sparc) || defined(hpux) || defined(_AIX) || defined(ultrix)
typedef void    sig_t;
#else
typedef int    sig_t;
#endif

#define bitset(a,b)    (((a) & (b)) != 0)

#ifdef ULTRIX_RESOLV
#define nslist(i)    _res.ns_list[i].addr
#else
#define nslist(i)    _res.nsaddr_list[i]
#endif

extern int errno;
extern struct state _res;    /* defined in res_init.c */

static int timeout;        /* connection read timeout */

extern char *inet_ntoa();

/* send.c */
int res_send();
#ifndef lint
void _res_close();
#endif
static int send_stream();
static int send_dgram();
static sig_t timer();
int _res_connect();
int _res_write();
int _res_read();
static int recvsock();

/*
** RES_SEND -- Send nameserver query and retrieve answer
** -----------------------------------------------------
**
**    Returns:
**        Length of nameserver answer buffer, if obtained.
**        -1 if an error occurred (errno set appropriately).
**
**    This is a simplified version of the BIND 4.8.3 res_send().
**    - Always use connected datagrams to get proper error messages.
**    - Do not only return ETIMEDOUT or ECONNREFUSED in datagram mode.
**    - Never leave a connection open after we got an answer.
**    - No special ECONNRESET handling when using virtual circuits.
*/

int
res_send(query, querylen, answer, anslen)
input char *query;            /* address of formatted query buffer */
input int querylen;            /* length of query buffer */
output char *answer;            /* address of buffer to store answer */
input int anslen;            /* maximum size of answer buffer */
{
    HEADER *bp = (HEADER *)answer;
    struct sockaddr_in *sin;
    int v_circuit;            /* virtual circuit or datagram switch */
    register int try, ns;
    register int n;

    /* make sure resolver has been initialized */
    if (!bitset(RES_INIT, _res.options) && res_init() == -1)
        return(-1);

    if (bitset(RES_DEBUG, _res.options))
    {
        printf("res_send()\n");
        p_query(query);
    }

    /* use virtual circuit if requested or if necessary */
    v_circuit = bitset(RES_USEVC, _res.options) || (querylen > PACKETSZ);

/*
 * Do _res.retry attempts for each of the _res.nscount addresses.
 */
    for (try = 0; try < _res.retry; try++)
    {
        for (ns = 0; ns < _res.nscount; ns++)
        {
        sin = &nslist(ns);
retry:
        if (bitset(RES_DEBUG, _res.options))
            printf("Querying server (# %d) %s address = %s\n", ns+1,
                v_circuit ? "tcp" : "udp", inet_ntoa(sin->sin_addr));

        if (v_circuit)
        {
            /* at most one attempt per server */
            try = _res.retry;

            /* connect via virtual circuit */
            n = send_stream(sin, query, querylen, answer, anslen);
        }
        else
        {
            /* set datagram read timeout for recvsock */
            timeout = (_res.retrans << try);
            if (try > 0)
                timeout /= _res.nscount;
            if (timeout <= 0)
                timeout = 1;

            /* connect via datagram */
            n = send_dgram(sin, query, querylen, answer, anslen);

            /* check truncation; use v_circuit with same server */
            if (n > 0 && bp->tc)
            {
                if (bitset(RES_DEBUG, _res.options))
                    (void) fprintf(stderr, "truncated answer\n");

                if (!bitset(RES_IGNTC, _res.options))
                {
                    v_circuit = 1;
                    goto retry;
                }
            }
        }

        if (n <= 0)
            continue;

        if (bitset(RES_DEBUG, _res.options))
        {
            printf("got answer:\n");
            p_query(answer);
        }

        /* we have an answer; clear possible error condition */
        errno = 0;
        return(n);
        }
    }

    return(-1);
}


/*
 * Note that this private version of res_send() is not only called
 * directly by 'host' but also indirectly by gethostbyname() or by
 * gethostbyaddr() via their resolver interface routines.
 */


/*
 * Provide dummy routine to prevent the real res_send() to be loaded.
 * This one is actually only called by endhostent() to close a socket
 * that was requested to stay open. But in this version sockets are
 * always closed after use.
 */

#ifndef lint

void
_res_close()
{
}

#endif

/*
** SEND_STREAM -- Query nameserver via virtual circuit
** ---------------------------------------------------
**
**    Returns:
**        Length of nameserver answer buffer, if obtained.
**        -1 if an error occurred.
**
**    Note that connect() is the call that is allowed to fail
**    under normal circumstances. All other failures generate
**    an unconditional error message.
*/

static int
send_stream(addr, query, querylen, answer, anslen)
input struct sockaddr_in *addr;        /* the server address to connect to */
input char *query;            /* address of formatted query buffer */
input int querylen;            /* length of query buffer */
output char *answer;            /* address of buffer to store answer */
input int anslen;            /* maximum size of answer buffer */
{
    int sock;
    register int n;

/*
 * Setup a virtual circuit connection.
 */
    sock = socket(AF_INET, SOCK_STREAM, 0);
    if (sock < 0)
    {
        perror("socket");
        return(-1);
    }

    if (_res_connect(sock, addr, sizeof(*addr)) < 0)
    {
        if (bitset(RES_DEBUG, _res.options))
            perror("connect");
        (void) close(sock);
        return(-1);
    }

    if (bitset(RES_DEBUG, _res.options))
        printf("connected to %s\n", inet_ntoa(addr->sin_addr));

/*
 * Send the query buffer.
 */
    if (_res_write(sock, query, querylen) < 0)
    {
        (void) close(sock);
        return(-1);
    }

/*
 * Read the answer buffer.
 */
    n = _res_read(sock, answer, anslen);
    if (n <= 0)
    {
        (void) close(sock);
        return(-1);
    }

/*
 * Never leave the socket open.
 */
    (void) close(sock);
    return(n);
}

/*
** SEND_DGRAM -- Query nameserver via datagram
** -------------------------------------------
**
**    Returns:
**        Length of nameserver answer buffer, if obtained.
**        -1 if an error occurred.
**
**    Inputs:
**        The global variable timeout should have been
**        set with the desired timeout value in seconds.
**
**    Sending to a nameserver datagram port with no nameserver running
**    will cause an ICMP port unreachable message to be returned. If the
**    socket is connected, we get an ECONNREFUSED error on the next socket
**    operation, and select returns if the error message is received.
**    Also, we get ENETUNREACH or EHOSTUNREACH errors if appropriate.
**    We thus get a proper error status before timing out.
**    This method usually works only if BSD >= 43.
**
**    Note that recv() is now the call that is allowed to fail
**    under normal circumstances. All other failures generate
**    an unconditional error message.
*/

static int
send_dgram(addr, query, querylen, answer, anslen)
input struct sockaddr_in *addr;        /* the server address to connect to */
input char *query;            /* address of formatted query buffer */
input int querylen;            /* length of query buffer */
output char *answer;            /* address of buffer to store answer */
input int anslen;            /* maximum size of answer buffer */
{
    HEADER *qp = (HEADER *)query;
    HEADER *bp = (HEADER *)answer;
    int sock;
    register int n;

/*
 * Setup a connected datagram socket.
 */
    sock = socket(AF_INET, SOCK_DGRAM, 0);
    if (sock < 0)
    {
        perror("socket");
        return(-1);
    }

    if (connect(sock, (struct sockaddr *)addr, sizeof(*addr)) < 0)
    {
        perror("connect");
        (void) close(sock);
        return(-1);
    }

/*
 * Send the query buffer.
 */
    if (send(sock, query, querylen, 0) != querylen)
    {
        perror("send");
        (void) close(sock);
        return(-1);
    }

/*
 * Wait for the arrival of a reply, timeout, or error message.
 */
wait:
    n = recvsock(sock, answer, anslen);
    if (n <= 0)
    {
        if (bitset(RES_DEBUG, _res.options))
            perror("recvfrom");
        (void) close(sock);
        return(-1);
    }

/*
 * Make sure it is the proper response by checking the packet id.
 */
    if (qp->id != bp->id)
    {
        if (bitset(RES_DEBUG, _res.options))
        {
            printf("old answer:\n");
            p_query(answer);
        }
        goto wait;
    }

/*
 * Never leave the socket open.
 */
    (void) close(sock);
    return(n);
}

/*
** _RES_CONNECT -- Connect to a stream (virtual circuit) socket
** ------------------------------------------------------------
**
**    Returns:
**        0 if successfully connected.
**        -1 in case of failure or timeout.
**
**    Note that we use _res.retrans to override the default
**    connect timeout value.
*/

static jmp_buf timer_buf;

static sig_t
/*ARGSUSED*/
timer(sig)
int sig;
{
    longjmp(timer_buf, 1);
}


int
_res_connect(sock, addr, addrlen)
input int sock;
input struct sockaddr_in *addr;        /* the server address to connect to */
input int addrlen;
{
    if (setjmp(timer_buf) != 0)
    {
        errno = ETIMEDOUT;
        (void) alarm((u_int)0);
        return(-1);
    }

    (void) signal(SIGALRM, timer);
    (void) alarm((u_int)_res.retrans);

    if (connect(sock, (struct sockaddr *)addr, addrlen) < 0)
    {
        if (errno == EINTR)
            errno = ETIMEDOUT;
        (void) alarm((u_int)0);
        return(-1);
    }

    (void) alarm((u_int)0);
    return(0);
}

/*
** _RES_WRITE -- Write the query buffer via a stream socket
** --------------------------------------------------------
**
**    Returns:
**        Length of buffer if successfully transmitted.
**        -1 in case of failure (error message is issued).
**
**    The query is sent in two steps: first a single word with
**    the length of the buffer, followed by the buffer itself.
*/

int
_res_write(sock, buf, bufsize)
input int sock;
input char *buf;            /* address of formatted query buffer */
input int bufsize;            /* length of query buffer */
{
    u_short len;

/*
 * Write the length of the query buffer.
 */
    len = htons(bufsize);

    if (write(sock, (char *)&len, sizeof(len)) != sizeof(len))
    {
        perror("write query length");
        return(-1);
    }

/*
 * Write the query buffer itself.
 */
    if (write(sock, buf, bufsize) != bufsize)
    {
        perror("write query");
        return(-1);
    }

    return(bufsize);
}

/*
** _RES_READ -- Read the answer buffer via a stream socket
** -------------------------------------------------------
**
**    Returns:
**        Length of buffer if successfully received.
**        -1 in case of failure (error message is issued).
**
**    The answer is read in two steps: first a single word which
**    gives the length of the buffer, followed by the buffer itself.
**    If the answer is too long to fit into the supplied buffer,
**    only the portion that fits will be stored, the residu will be
**    flushed, and the truncation flag will be set.
*/

int
_res_read(sock, buf, bufsize)
input int sock;
output char *buf;            /* address of buffer to store answer */
input int bufsize;            /* maximum size of answer buffer */
{
    u_short len;
    char *buffer;
    int buflen;
    int reslen;
    register int n;

    /* set stream timeout for recvsock */
    timeout = 60;

/*
 * Read the length of answer buffer.
 */
    buffer = (char *)&len;
    buflen = sizeof(len);

    while (buflen > 0 && (n = recvsock(sock, buffer, buflen)) > 0)
    {
        buffer += n;
        buflen -= n;
    }

    if (buflen != 0)
    {
        perror("read answer length");
        return(-1);
    }

/*
 * Terminate if length is zero.
 */
    len = ntohs(len);
    if (len == 0)
        return(0);

/*
 * Check for truncation.
 */
    reslen = 0;
    if ((int)len > bufsize)
    {
        reslen = len - bufsize;
        len = bufsize;
    }

/*
 * Read the answer buffer itself.
 */
    buffer = buf;
    buflen = len;

    while (buflen > 0 && (n = recvsock(sock, buffer, buflen)) > 0)
    {
        buffer += n;
        buflen -= n;
    }

    if (buflen != 0)
    {
        perror("read answer");
        return(-1);
    }

/*
 * Discard the residu to keep connection in sync.
 */
    if (reslen > 0)
    {
        HEADER *bp = (HEADER *)buf;
        char resbuf[PACKETSZ];

        buffer = resbuf;
        buflen = reslen < sizeof(resbuf) ? reslen : sizeof(resbuf);

        while (reslen > 0 && (n = recvsock(sock, buffer, buflen)) > 0)
        {
            reslen -= n;
            buflen = reslen < sizeof(resbuf) ? reslen : sizeof(resbuf);
        }

        if (reslen != 0)
        {
            perror("read residu");
            return(-1);
        }

        if (bitset(RES_DEBUG, _res.options))
            (void) fprintf(stderr, "response truncated\n");

        /* set truncation flag */
        bp->tc = 1;
    }

    return(len);
}

/*
** RECVSOCK -- Read from stream or datagram socket with timeout
** ------------------------------------------------------------
**
**    Returns:
**        Length of buffer if successfully received.
**        -1 in case of failure or timeout.
**
**    Inputs:
**        The global variable timeout should have been
**        set with the desired timeout value in seconds.
*/

static int
recvsock(sock, buffer, buflen)
input int sock;
output char *buffer;            /* current buffer address */
input int buflen;            /* remaining buffer size */
{
    fd_set fds;
    struct timeval wait;
    register int n;

    wait.tv_sec = timeout;
    wait.tv_usec = 0;

    /* FD_ZERO(&fds); */
    bzero((char *)&fds, sizeof(fds));
    FD_SET(sock, &fds);

/*
 * Wait for the arrival of data, or timeout.
 */
    n = select(FD_SETSIZE, &fds, (fd_set *)NULL, (fd_set *)NULL, &wait);
    if (n <= 0)
    {
        if (n == 0)
            errno = ETIMEDOUT;
        return(-1);
    }

/*
 * Fake an error if nothing was actually read.
 */
    n = recv(sock, buffer, buflen, 0);
    if (n == 0)
        errno = ECONNRESET;
    return(n);
}