/*  * This file is part of the UCB release of Plan 9. It is subject to the license * terms in the LICENSE file found in the top-level directory of this * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No * part of the UCB release of Plan 9, including this file, may be copied, * modified, propagated, or distributed except according to the terms contained * in the LICENSE file. */ #include <u.h>#include <libc.h>#include <bio.h>#include <ndb.h>#include <ndbhf.h> static void nstrcpy(char*, char*, int);static void mkptrname(char*, char*, int);static Ndbtuple *doquery(int, char *dn, char *type); /* *  search for a tuple that has the given 'attr=val' and also 'rattr=x'. *  copy 'x' into 'buf' and return the whole tuple. * *  return 0 if not found. */Ndbtuple*dnsquery(char *net, char *val, char *type){	char rip[128];	char *p;	Ndbtuple *t;	int fd; 	/* if the address is V4 or V6 null address, give up early */	if(strcmp(val, "::") == 0 || strcmp(val, "0.0.0.0") == 0)		return nil; 	if(net == nil)		net = "/net";	snprint(rip, sizeof(rip), "%s/dns", net);	fd = open(rip, ORDWR);	if(fd < 0){		if(strcmp(net, "/net") == 0)			snprint(rip, sizeof(rip), "/srv/dns");		else {			snprint(rip, sizeof(rip), "/srv/dns%s", net);			p = strrchr(rip, '/');			*p = '_';		}		fd = open(rip, ORDWR);		if(fd < 0)			return nil;		if(mount(fd, -1, net, MBEFORE, "") < 0){			close(fd);			return nil;		}		/* fd is now closed */		snprint(rip, sizeof(rip), "%s/dns", net);		fd = open(rip, ORDWR);		if(fd < 0)			return nil;	} 	/* zero out the error string */	werrstr(""); 	/* if this is a reverse lookup, first lookup the domain name */	if(strcmp(type, "ptr") == 0){		mkptrname(val, rip, sizeof rip);		t = doquery(fd, rip, "ptr");	} else		t = doquery(fd, val, type); 	/*	 * TODO: make fd static and keep it open to reduce 9P traffic	 * walking to /net*^/dns.  Must be prepared to re-open it on error.	 */	close(fd);	ndbsetmalloctag(t, getcallerpc(&net));	return t;} /* *  convert address into a reverse lookup address */static voidmkptrname(char *ip, char *rip, int rlen){	char buf[128];	char *p, *np;	int len; 	if(cistrstr(ip, "in-addr.arpa") || cistrstr(ip, "ip6.arpa")){		nstrcpy(rip, ip, rlen);		return;	} 	nstrcpy(buf, ip, sizeof buf);	for(p = buf; *p; p++)		;	*p = '.';	np = rip;	len = 0;	while(p >= buf){		len++;		p--;		if(*p == '.'){			memmove(np, p+1, len);			np += len;			len = 0;		}	}	memmove(np, p+1, len);	np += len;	strcpy(np, "in-addr.arpa");} static voidnstrcpy(char *to, char *from, int len){	strncpy(to, from, len);	to[len-1] = 0;} static Ndbtuple*doquery(int fd, char *dn, char *type){	char buf[1024];	int n;	Ndbtuple *t, *first, *last; 	seek(fd, 0, 0);	snprint(buf, sizeof(buf), "!%s %s", dn, type);	if(write(fd, buf, strlen(buf)) < 0)		return nil;			seek(fd, 0, 0); 	first = last = nil;		for(;;){		n = read(fd, buf, sizeof(buf)-2);		if(n <= 0)			break;		if(buf[n-1] != '\n')			buf[n++] = '\n';	/* ndbparsline needs a trailing new line */		buf[n] = 0; 		/* check for the error condition */		if(buf[0] == '!'){			werrstr("%s", buf+1);			return nil;		} 		t = _ndbparseline(buf);		if(t != nil){			if(first)				last->entry = t;			else				first = t;			last = t; 			while(last->entry)				last = last->entry;		}	} 	ndbsetmalloctag(first, getcallerpc(&fd));	return first;}