gethostent.c

<B>Digital的Unix操作系统VAX 4.2源码</B>

#ifdef DEBUG
	fprintf(stderr, "gethostbyname_yp(%s)\n", name);
#endif DEBUG
	sethostent_yp(0);
	if ((domain = yellowup(0)) == NULL)
		return (gethostbyname_local(name));
	if (reason = yp_match(domain, "hosts.byname", name, strlen(name), &val, &vallen)) {
#ifdef DEBUG
		fprintf(stderr, "reason yp_first failed is %d\n", reason);
#endif
		p = NULL;
	}
	else {
		p = interpret(val, vallen, SVC_YP);
		free(val);
	}
	endhostent_yp();
	return (p);
}

static
sethostent_local(f)
	int f;
{
	if (hostf == NULL)
		hostf = fopen(HOSTDB, "r");
	else
		rewind(hostf);
	stayopen |= f;
}

/*
 * setent_bind(stayopen) in getcommon.c
 */

sethostent_yp(f)
	int f;
{
	if ((domain = yellowup(1)) == NULL)
		return (sethostent_local (f));
	if (current)
		free(current);
	current = NULL;
	stayopen |= f;
}
static 
endhostent_local()
{
	if (hostf && !stayopen) {
		fclose(hostf);
		hostf = NULL;
	}
}

/*
 * endent_bind(stayopen) in getcommon.c
 */

endhostent_yp()
{
	if ((domain = yellowup(0)) == NULL)
		return (endhostent_local ());
	if (current && !stayopen) {
		free(current);
		current = NULL;
	}
}

static struct hostent *
gethostent_local()
{
	static char line1[BUFSIZ+1];

#ifdef DEBUG
	fprintf(stderr,"gethostent_local\n");
#endif DEBUG
	if (hostf == NULL && (hostf = fopen(HOSTDB, "r")) == NULL)
		return (NULL);
        if (fgets(line1, BUFSIZ, hostf) == NULL)
		return (NULL);
	return interpret(line1, strlen(line1), SVC_LOCAL);
}

struct hostent *
gethostent_bind()
{
	char bindbuf[64];
	struct hostent *hp = NULL;

	sprintf(bindbuf, "hosts-%d", svc_gethostbind);
#ifdef DEBUG
	fprintf(stderr, "gethostent_bind(%s)\n", bindbuf);
#endif DEBUG
	if ((hp = gethostbyname_bind(bindbuf)) == NULL)
		return(NULL);
	svc_gethostbind++;
	return(hp);
}

struct hostent *
gethostent_yp()
{
	struct hostent *hp;
	int reason;
	char *key = NULL;
	char *val = NULL;
	int keylen = 0;
	int vallen = 0;

#ifdef DEBUG
	fprintf(stderr,"gethostent_yp\n");
#endif DEBUG
	if ((domain = yellowup(0)) == NULL)
		return (gethostent_local ());
	if (current == NULL) {
		if (reason =  yp_first(domain, "hosts.byaddr", &key, &keylen, &val, &vallen)) {
#ifdef DEBUG
			fprintf(stderr, "reason yp_first failed is %d\n", reason);
#endif
			return NULL;
		}
	}
	else {
		if (reason = yp_next(domain, "hosts.byaddr", current, currentlen, &key, &keylen, &val, &vallen)) {
#ifdef DEBUG
			fprintf(stderr, "reason yp_next failed is %d\n", reason);
#endif
			return NULL;
		}
	}
	if (current)
		free(current);
	current = key;
	currentlen = keylen;
	hp = interpret(val, vallen, SVC_YP);
	free(val);
	return (hp);
}

static struct hostent *
interpret(val, len, svc)
	char *val;
	int len, svc;
{
	char *p;
	register char *cp, **q;

	strncpy(line, val, len);
	p = line;
	line[len] = '\n';
	if (*p == '#')
		switch (svc) {
			case SVC_LOCAL:
				return (gethostent_local());
			case SVC_YP:
				return (gethostent_yp());
		}
	cp = getcommon_any(p, "#\n");
	if (cp == NULL)
		switch (svc) {
			case SVC_LOCAL:
				return (gethostent_local());
			case SVC_YP:
				return (gethostent_yp());
		}
	*cp = '\0';
	cp = getcommon_any(p, " \t");
	if (cp == NULL)
		switch (svc) {
			case SVC_LOCAL:
				return (gethostent_local());
			case SVC_YP:
				return (gethostent_yp());
		}
	*cp++ = '\0';
	/* THIS STUFF IS INTERNET SPECIFIC */

	/* 
	 *	The hostent structure was modified in 4.3BSD to return
	 *	a list of host addresses, with the last address in the list
	 *	NULL.  Some 4.3 utilities expect the list, so set it up, 
	 *	but provide backward compatibility for local /etc/hosts
	 *	and YP by defining host.h_addr as the first address in 
	 *	the list.
	 */

	host.h_addr_list    = host_addrs;	/* point to the list */
	host.h_addr_list[0] = hostaddr;		/* point to the host addrs */
	host.h_addr_list[1] = (char *)0;	/* and null terminate */
	*((u_long *)host.h_addr) = inet_addr(p);
	
	host.h_length = sizeof (u_long);
	host.h_addrtype = AF_INET;
	while (*cp == ' ' || *cp == '\t')
		cp++;
	host.h_name = cp;
	q = host.h_aliases = host_aliases;
	cp = getcommon_any(cp, " \t");
	if (cp != NULL) 
		*cp++ = '\0';
	while (cp && *cp) {
		if (*cp == ' ' || *cp == '\t') {
			cp++;
			continue;
		}
		if (q < &host_aliases[MAXALIASES - 1])
			*q++ = cp;
		cp = getcommon_any(cp, " \t");
		if (cp != NULL)
			*cp++ = '\0';
	}
	*q = NULL;
	return (&host);
}

char *
hostalias(name)
	register char *name;
{
	register char *C1, *C2;
	FILE *fp;
	char *file, *getenv();
	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);
}

static struct hostent *
gethostdomain(name, domain)
	char *name, *domain;
{
	querybuf buf;
	char nbuf[2*MAXDNAME+2];
	char *longname = nbuf;
	int n;

	if (domain == NULL || strfind(name,domain)) {
		/*
		 * 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);

	n = res_mkquery(QUERY, longname, C_IN, T_A, (char *)NULL, 0, NULL, (char *)&buf, sizeof(buf));
	if (n < 0) {
#ifdef DEBUG
		if (_res.options & RES_DEBUG)
			fprintf(stderr,"res_mkquery failed\n");
#endif
		return ((struct hostent *)NULL);
	}
	return (getanswer((char *)&buf, n, 0));
}

static struct hostent *
getanswer(msg, msglen, iquery)
	char *msg;
	int msglen, iquery;
{
	register HEADER *hp;
	register char *cp;
	register int n;
	querybuf answer;
	char *eom, *bp, **ap;
	int type, class, buflen, ancount, qdcount;
	int haveanswer, getclass = C_ANY;
	char **hap;

	n = res_send(msg, msglen, (char *)&answer, sizeof(answer));
	if (n < 0) {
#ifdef DEBUG
		int terrno;
		terrno = errno;
		if (_res.options & RES_DEBUG)
			fprintf(stderr,"res_send failed\n");
		errno = terrno;
#endif
		h_errno = TRY_AGAIN;
		return ((struct hostent *)NULL);
	}
	eom = (char *)&answer + n;
	/*
	 * find first satisfactory answer
	 */
	hp = (HEADER *) &answer;
	ancount = ntohs(hp->ancount);
	qdcount = ntohs(hp->qdcount);
	if (hp->rcode != NOERROR || ancount == 0) {
#ifdef DEBUG
		if (_res.options & RES_DEBUG)
			fprintf(stderr,"rcode = %d, ancount=%d\n", hp->rcode, ancount);
#endif
		switch (hp->rcode) {
			case NXDOMAIN:
				/* Check if it's an authoritive answer */
				if (hp->aa)
					h_errno = HOST_NOT_FOUND;
				else
					h_errno = TRY_AGAIN;
				break;
			case SERVFAIL:
				h_errno = TRY_AGAIN;
				break;
			case NOERROR:
				if (hp->aa)
					h_errno = NO_ADDRESS;
				else
					h_errno = TRY_AGAIN;
				break;
			case FORMERR:
			case NOTIMP:
			case REFUSED:
				h_errno = NO_RECOVERY;
		}
		return ((struct hostent *)NULL);
	}
	bp = hostbuf;
	buflen = sizeof(hostbuf);
	cp = (char *)&answer + sizeof(HEADER);
	if (qdcount) {
		if (iquery) {
			if ((n = dn_expand((char *)&answer, eom,
			     cp, bp, buflen)) < 0) {
				h_errno = NO_RECOVERY;
				return ((struct hostent *)NULL);
			}
			cp += n + QFIXEDSZ;
			host.h_name = bp;
			n = strlen(bp) + 1;
			bp += n;
			buflen -= n;
		} else
			cp += dn_skipname(cp, eom) + QFIXEDSZ;
		while (--qdcount > 0)
			cp += dn_skipname(cp, eom) + QFIXEDSZ;
	} else if (iquery) {
		if (hp->aa)
			h_errno = HOST_NOT_FOUND;
		else
			h_errno = TRY_AGAIN;
		return ((struct hostent *)NULL);
	}
	ap = host_aliases;
	host.h_aliases = host_aliases;
	hap = h_addr_ptrs;
#ifdef h_addr
	host.h_addr_list = h_addr_ptrs;
#endif
	haveanswer = 0;
	while (--ancount >= 0 && cp < eom) {
		if ((n = dn_expand((char *)&answer, eom, cp, bp, buflen)) < 0)
			break;
		cp += n;
		type = _getshort(cp);
 		cp += sizeof(u_short);
		class = _getshort(cp);
 		cp += sizeof(u_short) + sizeof(u_long);
		n = _getshort(cp);
		cp += sizeof(u_short);
		if (type == T_CNAME) {
			cp += n;
			if (ap >= &host_aliases[MAXALIASES-1])
				continue;
			*ap++ = bp;
			n = strlen(bp) + 1;
			bp += n;
			buflen -= n;
			continue;
		}
		if (type == T_PTR) {
			if ((n = dn_expand((char *)&answer, eom,
			    cp, bp, buflen)) < 0) {
				cp += n;
				continue;
			}
			cp += n;
			host.h_name = bp;
			return(&host);
		}
		if (type != T_A)  {
#ifdef DEBUG
			if (_res.options & RES_DEBUG)
				fprintf(stderr,"unexpected answer type %d, size %d\n",
					type, n);
#endif
			cp += n;
			continue;
		}
		if (haveanswer) {
			if (n != host.h_length) {
				cp += n;
				continue;
			}
			if (class != getclass) {
				cp += n;
				continue;
			}
		} else {
			host.h_length = n;
			getclass = class;
			host.h_addrtype = (class == C_IN) ? AF_INET : AF_UNSPEC;
			if (!iquery) {
				host.h_name = bp;
				bp += strlen(bp) + 1;
			}
		}

		bp += sizeof(align) - ((u_long)bp % sizeof(align));

		if (bp + n >= &hostbuf[sizeof(hostbuf)]) {
#ifdef DEBUG
			if (_res.options & RES_DEBUG)
				fprintf(stderr,"size (%d) too big\n", n);
#endif
			break;
		}
		bcopy(cp, *hap++ = bp, n);
		bp +=n;
		cp += n;
		haveanswer++;
	}
	if (haveanswer) {
		*ap = NULL;
#ifdef h_addr
		*hap = NULL;
#else
		host.h_addr = h_addr_ptrs[0];
#endif
		return (&host);
	} else {
		h_errno = TRY_AGAIN;
		return ((struct hostent *)NULL);
	}
}

/*
 * If
 *	1.  There is a dot in hname, and
 *	2.  the resolver is inited, and
 *	3.  the default domain name is not null, and
 *	4.  the end of hname contains the local domain name
 * return the length of the local host name of hname.
 */
local_hostname_length(hname)
	char *hname;
{
	char *cp;
	int i,j = 0;

	if (hname == NULL)
		return(NULL);
	i = strlen(hname);
	for (cp = hname; cp && *cp != NULL && *cp != '.'; cp++, j++)
		;
	if ((j < i) && (res_init() != -1) && (_res.defdname[0] != '\0') && ((strcasecmp(cp+1, _res.defdname)) == NULL))
		return(j);
	return(NULL);
}

/* Function:
 *
 *	strfind
 *
 * Function Description:
 *
 *	Searches for  substr  at the END of text. ie.
 *	See if one string is terminated by the occurance of another string.
 *	
 * Arguments:
 *
 *	char	*text		Text to search
 *	char	*substr		String to locate
 *
 * Return values:
 *
 *	Pointer to  substr  starting position in text if found.
 *	NULL if not found.
 *
 * Side Effects:
 *
 *	
 */
char *
strfind(text,substr)
		char *text, *substr;
{
	int	substrlen;
	int	textlen;

textlen = strlen(text);
substrlen = strlen(substr);

if (textlen > substrlen) 
	text = (text + textlen) - substrlen;

else
	return(NULL);

/* Search end of text for match.
 */
if (strncasecmp(text, substr, substrlen) == NULL)
        return(text);
else
        return(NULL);
}/*E strfind() */