/*  * 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 <ip.h>#include "dns.h" static RR*	doextquery(DNSmsg*, Request*, int);static void	hint(RR**, RR*); /* set in dns.c */int	norecursion;		/* don't allow recursive requests */ /* *  answer a dns request */voiddnserver(DNSmsg *reqp, DNSmsg *repp, Request *req, uchar *srcip, int rcode){	int recursionflag;	char *cp, *errmsg;	char tname[32];	DN *nsdp, *dp;	Area *myarea;	RR *tp, *neg, *rp; 	dncheck(nil, 1); 	recursionflag = norecursion? 0: Fcanrec;	memset(repp, 0, sizeof(*repp));	repp->id = reqp->id;	repp->flags = Fresp | recursionflag | Oquery; 	/* move one question from reqp to repp */	tp = reqp->qd;	reqp->qd = tp->next;	tp->next = nil;	repp->qd = tp; 	if (rcode) {		errmsg = "";		if (rcode >= 0 && rcode < nrname)			errmsg = rname[rcode];		dnslog("server: response code 0%o (%s), req from %I",			rcode, errmsg, srcip);		/* provide feedback to clients who send us trash */		repp->flags = (rcode&Rmask) | Fresp | Fcanrec | Oquery;		return;	}	if(!rrsupported(repp->qd->type)){		dnslog("server: unsupported request %s from %I",			rrname(repp->qd->type, tname, sizeof tname), srcip);		repp->flags = Runimplimented | Fresp | Fcanrec | Oquery;		return;	} 	if(repp->qd->owner->class != Cin){		dnslog("server: unsupported class %d from %I",			repp->qd->owner->class, srcip);		repp->flags = Runimplimented | Fresp | Fcanrec | Oquery;		return;	} 	myarea = inmyarea(repp->qd->owner->name);	if(myarea != nil) {		if(repp->qd->type == Tixfr || repp->qd->type == Taxfr){			dnslog("server: unsupported xfr request %s for %s from %I",				rrname(repp->qd->type, tname, sizeof tname),				repp->qd->owner->name, srcip);			repp->flags = Runimplimented | Fresp | recursionflag |				Oquery;			return;		}	} else		if(norecursion) {			/* we don't recurse and we're not authoritative */			repp->flags = Rok | Fresp | Oquery;			return;		} 	/*	 *  get the answer if we can, in *repp	 */	if(reqp->flags & Frecurse)		neg = doextquery(repp, req, Recurse);	else		neg = doextquery(repp, req, Dontrecurse); 	/* authority is transitive */	if(myarea != nil || (repp->an && repp->an->auth))		repp->flags |= Fauth; 	/* pass on error codes */	if(repp->an == nil){		dp = dnlookup(repp->qd->owner->name, repp->qd->owner->class, 0);		if(dp->rr == nil)			if(reqp->flags & Frecurse)				repp->flags |= dp->respcode | Fauth;	} 	if(myarea == nil)		/*		 *  add name server if we know		 */		for(cp = repp->qd->owner->name; cp; cp = walkup(cp)){			nsdp = dnlookup(cp, repp->qd->owner->class, 0);			if(nsdp == nil)				continue; 			repp->ns = rrlookup(nsdp, Tns, OKneg);			if(repp->ns){				/* don't pass on anything we know is wrong */				if(repp->ns->negative){					lock(&dnlock);					rp = repp->ns;					repp->ns = nil;					rrfreelist(rp);					unlock(&dnlock);				}				break;			} 			if (strncmp(nsdp->name, "local#", 6) == 0)				dnslog("returning %s as nameserver", nsdp->name);			repp->ns = dblookup(cp, repp->qd->owner->class, Tns, 0, 0);			if(repp->ns)				break;		} 	/*	 *  add ip addresses as hints	 */	if(repp->qd->type != Taxfr && repp->qd->type != Tixfr){		for(tp = repp->ns; tp; tp = tp->next)			hint(&repp->ar, tp);		for(tp = repp->an; tp; tp = tp->next)			hint(&repp->ar, tp);	} 	/* hint calls rrlookup which holds dnlock, so don't lock before this. */ 	/*	 *  add an soa to the authority section to help client	 *  with negative caching	 */	if(repp->an == nil)		if(myarea != nil){			lock(&dnlock);			rrcopy(myarea->soarr, &tp);			rrcat(&repp->ns, tp);			unlock(&dnlock);		} else if(neg != nil) {			if(neg->negsoaowner != nil) {				tp = rrlookup(neg->negsoaowner, Tsoa, NOneg);				lock(&dnlock);				rrcat(&repp->ns, tp);				unlock(&dnlock);			}			repp->flags |= neg->negrcode;		} 	/*	 *  get rid of duplicates	 */	lock(&dnlock);	unique(repp->an);	unique(repp->ns);	unique(repp->ar); 	rrfreelist(neg);	unlock(&dnlock); 	dncheck(nil, 1);} /* *  satisfy a recursive request.  dnlookup will handle cnames. */static RR*doextquery(DNSmsg *mp, Request *req, int recurse){	ushort type;	char *name;	RR *rp, *neg; 	name = mp->qd->owner->name;	type = mp->qd->type;	rp = dnresolve(name, Cin, type, req, &mp->an, 0, recurse, 1, 0); 	lock(&dnlock);	/* don't return soa hints as answers, it's wrong */	if(rp && rp->db && !rp->auth && rp->type == Tsoa) {		rrfreelist(rp);		rp = nil;	} 	/* don't let negative cached entries escape */	neg = rrremneg(&rp);	rrcat(&mp->an, rp);	unlock(&dnlock);	return neg;} static voidhint(RR **last, RR *rp){	RR *hp; 	switch(rp->type){	case Tns:	case Tmx:	case Tmb:	case Tmf:	case Tmd:		assert(rp->host != nil);		hp = rrlookup(rp->host, Ta, NOneg);		if(hp == nil)			hp = dblookup(rp->host->name, Cin, Ta, 0, 0);		if(hp == nil)			hp = rrlookup(rp->host, Taaaa, NOneg);		if(hp == nil)			hp = dblookup(rp->host->name, Cin, Taaaa, 0, 0);		if (hp && hp->owner && hp->owner->name &&		    strncmp(hp->owner->name, "local#", 6) == 0)			dnslog("returning %s as hint", hp->owner->name);		lock(&dnlock);		rrcat(last, hp);		unlock(&dnlock);		break;	}}