2.11BSD/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 5.3 (Berkeley) 4/5/88";
#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;
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++) {
h_errno = 0;
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 != 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));
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);
}