arlib.c

网络时间协议NTP 源码 版本v4.2.0b 该源码用于linux平台下

	return (ar_query_name(hname, C_IN, T_A, rptr));
}


/*
 * ar_gethostbyaddr
 *
 * Generates a query for a given IP address.
 */
int	ar_gethostbyaddr(addr, info, size)
char	*addr;
char	*info;
int	size;
{
	struct	resinfo	resi;
	register struct resinfo *rp = &resi;

	if (size && info)
	    {
		rp->ri_ptr = (char *)malloc(size);
		bcopy(info, rp->ri_ptr, size);
		rp->ri_size = size;
	    }
	else
		bzero((char *)rp, sizeof(resi));
	ar_reinfo.re_nu_look++;
	return (do_query_number(rp, addr, NULL));
}


/*
 * do_query_number
 *
 * Use this to do reverse IP# lookups.
 */
static	int	do_query_number(resi, numb, rptr)
struct	resinfo	*resi;
char	*numb;
register struct	reslist	*rptr;
{
	register unsigned char	*cp;
	static	char	ipbuf[32];

	/*
	 * Generate name in the "in-addr.arpa" domain.  No addings bits to this
	 * name to get more names to query!.
	 */
	cp = (unsigned char *)numb;
	(void)sprintf(ipbuf,"%u.%u.%u.%u.in-addr.arpa.",
			(unsigned int)(cp[3]), (unsigned int)(cp[2]),
			(unsigned int)(cp[1]), (unsigned int)(cp[0]));

	if (!rptr)
	    {
		rptr = ar_make_request(resi);
		rptr->re_type = T_PTR;
		rptr->re_he.h_length = sizeof(struct in_addr);
		bcopy(numb, (char *)&rptr->re_addr, rptr->re_he.h_length);
		bcopy(numb, (char *)&rptr->re_he.h_addr_list[0].s_addr,
			rptr->re_he.h_length);
	    }
	return (ar_query_name(ipbuf, C_IN, T_PTR, rptr));
}


/*
 * ar_resent_query
 *
 * resends a query.
 */
static	int	ar_resend_query(rptr)
struct	reslist	*rptr;
{
	if (!rptr->re_resend)
		return -1;

	switch(rptr->re_type)
	{
	case T_PTR:
		ar_reinfo.re_resends++;
		return do_query_number(NULL, &rptr->re_addr, rptr);
	case T_A:
		ar_reinfo.re_resends++;
		return do_query_name(NULL, rptr->re_name, rptr);
	default:
		break;
	}

	return -1;
}


/*
 * ar_procanswer
 *
 * process an answer received from a nameserver.
 */
static	int	ar_procanswer(rptr, hptr, buf, eob)
struct	reslist	*rptr;
char	*buf, *eob;
HEADER	*hptr;
{
	char	*cp, **alias, *s;
	int	class, type, dlen, len, ans = 0, n, i;
	u_int32_t ttl, dr, *adr;
	struct	hent	*hp;

	cp = buf + sizeof(HEADER);
	adr = (u_int32_t *)rptr->re_he.h_addr_list;

	while (*adr)
		adr++;

	alias = rptr->re_he.h_aliases;
	while (*alias)
		alias++;

	hp = &rptr->re_he;


	/*
	 * Skip over the original question.
	 */
	while (hptr->qdcount-- > 0)
		cp += dn_skipname(cp, eob) + QFIXEDSZ;
	/*
	 * proccess each answer sent to us. blech.
	 */
	while (hptr->ancount-- > 0 && cp < eob) {
		n = dn_expand(buf, eob, cp, ar_hostbuf, sizeof(ar_hostbuf));
		cp += n;
		if (n <= 0)
			return ans;

		ans++;
		/*
		 * 'skip' past the general dns crap (ttl, class, etc) to get
		 * the pointer to the right spot.  Some of thse are actually
		 * useful so its not a good idea to skip past in one big jump.
		 */
		type = (int)_getshort(cp);
		cp += sizeof(short);
		class = (int)_getshort(cp);
		cp += sizeof(short);
		ttl = (u_int32_t)_getlong(cp);
		cp += sizeof(u_int32_t);
		dlen =  (int)_getshort(cp);
		cp += sizeof(short);
		rptr->re_type = type;

		switch(type)
		{
		case T_A :
			rptr->re_he.h_length = dlen;
			if (ans == 1)
				rptr->re_he.h_addrtype=(class == C_IN) ?
							AF_INET : AF_UNSPEC;
			if (dlen != sizeof(dr))
			    {
				h_errno = TRY_AGAIN;
				continue;
			    }
			bcopy(cp, &dr, dlen);
			*adr++ = dr;
			*adr = 0;
			cp += dlen;
			len = strlen(ar_hostbuf);
			if (!rptr->re_he.h_name)
			    {
				rptr->re_he.h_name = (char *)malloc(len+1);
				if (!rptr->re_he.h_name)
					break;
				(void)strcpy(rptr->re_he.h_name, ar_hostbuf);
			    }
 			break;
		case T_PTR :
			if ((n = dn_expand(buf, eob, cp, ar_hostbuf,
					   sizeof(ar_hostbuf) )) < 0)
			    {
				cp += n;
				continue;
			    }
			cp += n;
			len = strlen(ar_hostbuf)+1;
			/*
			 * copy the returned hostname into the host name
			 * or alias field if there is a known hostname
			 * already.
			 */
			if (!rptr->re_he.h_name)
			    {
				rptr->re_he.h_name = (char *)malloc(len);
				if (!rptr->re_he.h_name)
					break;
				(void)strcpy(rptr->re_he.h_name, ar_hostbuf);
			    }
			else
			    {
				*alias = (char *)malloc(len);
				if (!*alias)
					return -1;
				(void)strcpy(*alias++, ar_hostbuf);
				*alias = NULL;
			    }
			break;
		case T_CNAME :
			cp += dlen;
			if (alias >= &(rptr->re_he.h_aliases[MAXALIASES-1]))
				continue;
			n = strlen(ar_hostbuf)+1;
			*alias = (char *)malloc(n);
			if (!*alias)
				return -1;
			(void)strcpy(*alias++, ar_hostbuf);
			*alias = NULL;
			break;
		default :
			break;
		}
	}

	return ans;
}


/*
 * ar_answer
 *
 * Get an answer from a DNS server and process it.  If a query is found to
 * which no answer has been given to yet, copy its 'info' structure back
 * to where "reip" points and return a pointer to the hostent structure.
 */
struct	hostent	*ar_answer(reip, size)
char	*reip;
int	size;
{
	static	char	ar_rcvbuf[sizeof(HEADER) + MAXPACKET];
	static	struct	hostent	ar_host;

	register HEADER	*hptr;
	register struct	reslist	*rptr = NULL;
	register struct hostent *hp;
	register char **s;
	unsigned long	*adr;
	int	rc, i, n, a;

	rc = recv(ar_resfd, ar_rcvbuf, sizeof(ar_rcvbuf), 0);
	if (rc <= 0)
		goto getres_err;

	ar_reinfo.re_replies++;
	hptr = (HEADER *)ar_rcvbuf;
	/*
	 * convert things to be in the right order.
	 */
	hptr->id = ntohs(hptr->id);
	hptr->ancount = ntohs(hptr->ancount);
	hptr->arcount = ntohs(hptr->arcount);
	hptr->nscount = ntohs(hptr->nscount);
	hptr->qdcount = ntohs(hptr->qdcount);
	/*
	 * response for an id which we have already received an answer for
	 * just ignore this response.
	 */
	rptr = ar_find_id(hptr->id);
	if (!rptr)
		goto getres_err;

	if ((hptr->rcode != NOERROR) || (hptr->ancount == 0))
	    {
		switch (hptr->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;
		}
		ar_reinfo.re_errors++;
		/*
		** If a bad error was returned, we stop here and dont send
		** send any more (no retries granted).
		*/
		if (h_errno != TRY_AGAIN)
		    {
			rptr->re_resend = 0;
			rptr->re_retries = 0;
		    }
		goto getres_err;
	    }

	a = ar_procanswer(rptr, hptr, ar_rcvbuf, ar_rcvbuf+rc);

	if ((rptr->re_type == T_PTR) && (_res.options & RES_CHECKPTR))
	    {
		/*
		 * For reverse lookups on IP#'s, lookup the name that is given
		 * for the ip# and return with that as the official result.
		 * -avalon
		 */
		rptr->re_type = T_A;
		/*
		 * Clean out the list of addresses already set, even though
		 * there should only be one :)
		 */
		adr = (unsigned long *)rptr->re_he.h_addr_list;
		while (*adr)
			*adr++ = 0L;
		/*
		 * Lookup the name that we were given for the ip#
		 */
		ar_reinfo.re_na_look++;
		(void)strncpy(rptr->re_name, rptr->re_he.h_name,
			sizeof(rptr->re_name)-1);
		rptr->re_he.h_name = NULL;
		rptr->re_retries = _res.retry;
		rptr->re_sends = 1;
		rptr->re_resend = 1;
		rptr->re_he.h_name = NULL;
		ar_reinfo.re_na_look++;
		(void)ar_query_name(rptr->re_name, C_IN, T_A, rptr);
		return NULL;
	    }

	if (reip && rptr->re_rinfo.ri_ptr && size)
		bcopy(rptr->re_rinfo.ri_ptr, reip,
			MIN(rptr->re_rinfo.ri_size, size));
	/*
	 * Clean up structure from previous usage.
	 */
	hp = &ar_host;
#ifdef	ARLIB_DEBUG
	ar_dump_hostent("ar_answer: previous usage", hp);
#endif

	if (hp->h_name)
		(void)free(hp->h_name);
	if (s = hp->h_aliases)
	    {
		while (*s)
			(void)free(*s++);
		(void)free(hp->h_aliases);
	    }
	if (s = hp->h_addr_list)
	    {
		/*
		 * Only free once since we allocated space for
		 * address in one big chunk.
		 */
		(void)free(*s);
		(void)free(hp->h_addr_list);
	    }
	bzero((char *)hp, sizeof(*hp));

	/*
	 * Setup and copy details for the structure we return a pointer to.
	 */
	hp->h_addrtype = AF_INET;
	hp->h_length = sizeof(struct in_addr);
	if(rptr->re_he.h_name)
	    {
		hp->h_name = (char *)malloc(strlen(rptr->re_he.h_name)+1);
		if(!hp->h_name)
		    {
#ifdef	ARLIB_DEBUG
			fprintf(stderr, "no memory for hostname\n");
#endif
			h_errno = TRY_AGAIN;
			goto getres_err;
		    }
		(void)strcpy(hp->h_name, rptr->re_he.h_name);
	    }
#ifdef	ARLIB_DEBUG
	ar_dump_hostent("ar_answer: (snap) store name", hp);
#endif

	/*
	 * Count IP#'s.
	 */
	for (i = 0, n = 0; i < MAXADDRS; i++, n++)
		if (!rptr->re_he.h_addr_list[i].s_addr)
			break;
	s = hp->h_addr_list = (char **)malloc((n + 1) * sizeof(char *));
	if (n)
	    {
		*s = (char *)malloc(n * sizeof(struct in_addr));
		if(!*s)
		    {
#ifdef	ARLIB_DEBUG
			fprintf(stderr, "no memory for IP#'s (%d)\n", n);
#endif
			h_errno = TRY_AGAIN;
			goto getres_err;
		    }
		bcopy((char *)&rptr->re_he.h_addr_list[0].s_addr, *s,
			sizeof(struct in_addr));
		s++;
		for (i = 1; i < n; i++, s++)
		    {
			*s = hp->h_addr + i * sizeof(struct in_addr);
			bcopy((char *)&rptr->re_he.h_addr_list[i].s_addr, *s,
				sizeof(struct in_addr));
		    }
	    }
	*s = NULL;
#ifdef	ARLIB_DEBUG
	ar_dump_hostent("ar_answer: (snap) store IP#'s", hp);
#endif

	/*
	 * Count CNAMEs
	 */
	for (i = 0, n = 0; i < MAXADDRS; i++, n++)
		if (!rptr->re_he.h_aliases[i])
			break;
	s = hp->h_aliases = (char **)malloc((n + 1) * sizeof(char *));
	if (!s)
	    {
#ifdef	ARLIB_DEBUG
		fprintf(stderr, "no memory for aliases (%d)\n", n);
#endif
		h_errno = TRY_AGAIN;
		goto getres_err;
	    }
	for (i = 0; i < n; i++)
	    {
		*s++ = rptr->re_he.h_aliases[i];
		rptr->re_he.h_aliases[i] = NULL;
	    }
	*s = NULL;
#ifdef	ARLIB_DEBUG
	ar_dump_hostent("ar_answer: (snap) store CNAMEs", hp);
	ar_dump_hostent("ar_answer: new one", hp);
#endif

	if (a > 0)
		(void)ar_remrequest(rptr);
	else
		if (!rptr->re_sent)
			(void)ar_remrequest(rptr);
	return hp;

getres_err:
	if (rptr)
	    {
		if (reip && rptr->re_rinfo.ri_ptr && size)
			bcopy(rptr->re_rinfo.ri_ptr, reip,
				MIN(rptr->re_rinfo.ri_size, size));
		if ((h_errno != TRY_AGAIN) &&
		    (_res.options & (RES_DNSRCH|RES_DEFNAMES) ==
		     (RES_DNSRCH|RES_DEFNAMES) ))
			if (_res.dnsrch[rptr->re_srch])
			    {
				rptr->re_retries = _res.retry;
				rptr->re_sends = 1;
				rptr->re_resend = 1;
				(void)ar_resend_query(rptr);
				rptr->re_srch++;
			    }
		return NULL;
	    }
	return NULL;
}


#ifdef	ARLIB_DEBUG
void ar_dump_hostent(prefix, hp)
char *prefix;
struct hostent *hp;
{
	register char **s;

	fflush(stdout);

	fprintf(stderr, "%s\n", prefix);
	fprintf(stderr, "  hp %p\n", hp);
	fprintf(stderr, "    h_name %p '%s'\n",
	hp->h_name, hp->h_name);
	if (s = hp->h_aliases)
	    {
		fprintf(stderr, "    h_aliases %p\n",
		hp->h_aliases);
		while (*s)
		    {
			fprintf(stderr, "      element %p\n", *s);
			s++;
		    }
	    }
	if (s = hp->h_addr_list)
	    {
		fprintf(stderr, "    h_addr_list %p\n",
		hp->h_addr_list);
		while (*s)
		    {
			fprintf(stderr, "      element %p\n", *s);
			s++;
		    }
	    }

	fflush(stderr);
}


void ar_dump_reslist(FILE* fp)
{
	register struct reslist *rptr;
	int c;

	c = 0;
	for (rptr = ar_first; rptr; rptr = rptr->re_next)
	    {
		fprintf(fp, "%4d [%p] %4d [%p]: %s\n", rptr->re_id, rptr,
			*(rptr->re_rinfo.ri_ptr), rptr->re_rinfo.ri_ptr,
			rptr->re_name);
	    }
}
#endif