usr/src/lib/libc/net/res_query.c

/*
 * Copyright (c) 1988 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_query.c 5.4 (Berkeley) 4/21/88";
#endif /* LIBC_SCCS and not lint */

#include <sys/param.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <ctype.h>
#include <netdb.h>
#include <stdio.h>
#include <errno.h>
#include <strings.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <resolv.h>

#if PACKETSZ > 1024
#define MAXPACKET       PACKETSZ
#else
#define MAXPACKET       1024
#endif

extern int errno;
int h_errno;

/*
 * Formulate a normal query, send, and await answer.
 * Returned answer is placed in supplied buffer "answer".
 * Perform preliminary check of answer, returning success only
 * if no error is indicated and the answer count is nonzero.
 * Return the size of the response on success, -1 on error.
 * Error number is left in h_errno.
 * Caller must parse answer and determine whether it answers the question.
 */
res_query(name, class, type, answer, anslen)
        char *name;             /* domain name */
        int class, type;        /* class and type of query */
        u_char *answer;         /* buffer to put answer */
        int anslen;             /* size of answer buffer */
{
        char buf[MAXPACKET];
        HEADER *hp;
        int n;

        if ((_res.options & RES_INIT) == 0 && res_init() == -1)
                return (-1);
#ifdef DEBUG
        if (_res.options & RES_DEBUG)
                printf("res_query(%s, %d, %d)\n", name, class, type);
#endif
        n = res_mkquery(QUERY, name, class, type, (char *)NULL, 0, NULL,
            buf, sizeof(buf));

        if (n <= 0) {
#ifdef DEBUG
                if (_res.options & RES_DEBUG)
                        printf("res_query: mkquery failed\n");
#endif
                h_errno = NO_RECOVERY;
                return (n);
        }
        n = res_send(buf, n, answer, anslen);
        if (n < 0) {
#ifdef DEBUG
                if (_res.options & RES_DEBUG)
                        printf("res_query: send error\n");
#endif
                h_errno = TRY_AGAIN;
                return(n);
        }

        hp = (HEADER *) answer;
        if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
#ifdef DEBUG
                if (_res.options & RES_DEBUG)
                        printf("rcode = %d, ancount=%d\n", hp->rcode,
                            ntohs(hp->ancount));
#endif
                switch (hp->rcode) {
                        case NXDOMAIN:
                                h_errno = HOST_NOT_FOUND;
                                break;
                        case SERVFAIL:
                                h_errno = TRY_AGAIN;
                                break;
                        case NOERROR:
                                h_errno = NO_DATA;
                                break;
                        case FORMERR:
                        case NOTIMP:
                        case REFUSED:
                        default:
                                h_errno = NO_RECOVERY;
                                break;
                }
                return (-1);
        }
        return(n);
}

/*
 * Formulate a normal query, send, and retrieve answer in supplied buffer.
 * Return the size of the response on success, -1 on error.
 * If enabled, implement search rules until answer or unrecoverable failure
 * is detected.  Error number is left in h_errno.
 * Only useful for queries in the same name hierarchy as the local host
 * (not, for example, for host address-to-name lookups in domain in-addr.arpa).
 */
res_search(name, class, type, answer, anslen)
        char *name;             /* domain name */
        int class, type;        /* class and type of query */
        u_char *answer;         /* buffer to put answer */
        int anslen;             /* size of answer */
{
        register char *cp, **domain;
        int n, ret, got_nodata = 0;
        char *hostalias();

        if ((_res.options & RES_INIT) == 0 && res_init() == -1)
                return (-1);

        errno = 0;
        h_errno = HOST_NOT_FOUND;               /* default, if we never query */
        for (cp = name, n = 0; *cp; cp++)
                if (*cp == '.')
                        n++;
        if (n == 0 && (cp = hostalias(name)))
                return (res_query(cp, class, type, answer, anslen));

        if ((n == 0 || *--cp != '.') && (_res.options & RES_DEFNAMES))
            for (domain = _res.dnsrch; *domain; domain++) {
                ret = res_querydomain(name, *domain, class, type,
                    answer, anslen);
                if (ret > 0)
                        return (ret);
                /*
                 * If no server present, give up.
                 * If name isn't found in this domain,
                 * keep trying higher domains in the search list
                 * (if that's enabled).
                 * On a NO_DATA error, keep trying, otherwise
                 * a wildcard entry of another type could keep us
                 * from finding this entry higher in the domain.
                 * If we get some other error (non-authoritative negative
                 * answer or server failure), then stop searching up,
                 * but try the input name below in case it's fully-qualified.
                 */
                if (errno == ECONNREFUSED) {
                        h_errno = TRY_AGAIN;
                        return (-1);
                }
                if (h_errno == NO_DATA)
                        got_nodata++;
                if ((h_errno != HOST_NOT_FOUND && h_errno != NO_DATA) ||
                    (_res.options & RES_DNSRCH) == 0)
                        break;
        }
        /*
         * If the search/default failed, try the name as fully-qualified,
         * but only if it contained at least one dot (even trailing).
         */
        if (n)
                return (res_querydomain(name, (char *)NULL, class, type,
                    answer, anslen));
        if (got_nodata)
                h_errno = NO_DATA;
        return (-1);
}

/*
 * Perform a call on res_query on the concatenation of name and domain,
 * removing a trailing dot from name if domain is NULL.
 */
res_querydomain(name, domain, class, type, answer, anslen)
        char *name, *domain;
        int class, type;        /* class and type of query */
        u_char *answer;         /* buffer to put answer */
        int anslen;             /* size of answer */
{
        char nbuf[2*MAXDNAME+2];
        char *longname = nbuf;
        int n;

#ifdef DEBUG
        if (_res.options & RES_DEBUG)
                printf("res_querydomain(%s, %s, %d, %d)\n",
                    name, domain, class, type);
#endif
        if (domain == NULL) {
                /*
                 * Check for trailing '.';
                 * copy without '.' if present.
                 */
                n = strlen(name) - 1;
                if (name[n] == '.' && n < sizeof(nbuf) - 1) {
                        bcopy(name, nbuf, n);
                        nbuf[n] = '\0';
                } else
                        longname = name;
        } else
                (void)sprintf(nbuf, "%.*s.%.*s",
                    MAXDNAME, name, MAXDNAME, domain);

        return (res_query(longname, class, type, answer, anslen));
}

char *
hostalias(name)
        register char *name;
{
        register char *C1, *C2;
        FILE *fp;
        char *file, *getenv(), *strcpy(), *strncpy();
        char buf[BUFSIZ];
        static char abuf[MAXDNAME];

        file = getenv("HOSTALIASES");
        if (file == NULL || (fp = fopen(file, "r")) == NULL)
                return (NULL);
        buf[sizeof(buf) - 1] = '\0';
        while (fgets(buf, sizeof(buf), fp)) {
                for (C1 = buf; *C1 && !isspace(*C1); ++C1);
                if (!*C1)
                        break;
                *C1 = '\0';
                if (!strcasecmp(buf, name)) {
                        while (isspace(*++C1));
                        if (!*C1)
                                break;
                        for (C2 = C1 + 1; *C2 && !isspace(*C2); ++C2);
                        abuf[sizeof(abuf) - 1] = *C2 = '\0';
                        (void)strncpy(abuf, C1, sizeof(abuf) - 1);
                        fclose(fp);
                        return (abuf);
                }
        }
        fclose(fp);
        return (NULL);
}