add dns

src/cmd/ndb/dnserver.c

@@ -0,0 +1,178 @@
+#include <u.h>
+#include <libc.h>
+#include <ip.h>
+#include <bio.h>
+#include <ndb.h>
+#include "dns.h"
+
+static RR*	doextquery(DNSmsg*, Request*, int);
+static void	hint(RR**, RR*);
+
+extern char *logfile;
+
+/*
+ *  answer a dns request
+ */
+void
+dnserver(DNSmsg *reqp, DNSmsg *repp, Request *req)
+{
+	RR *tp, *neg;
+	char *cp;
+	DN *nsdp, *dp;
+	Area *myarea;
+	char tname[32];
+
+	dncheck(nil, 1);
+
+	memset(repp, 0, sizeof(*repp));
+	repp->id = reqp->id;
+	repp->flags = Fresp | Fcanrec | Oquery;
+
+	/* move one question from reqp to repp */
+	tp = reqp->qd;
+	reqp->qd = tp->next;
+	tp->next = 0;
+	repp->qd = tp;
+
+	if(!rrsupported(repp->qd->type)){
+		syslog(0, logfile, "server: request %s", rrname(repp->qd->type, tname, sizeof tname));
+		repp->flags = Runimplimented | Fresp | Fcanrec | Oquery;
+		return;
+	}
+
+	if(repp->qd->owner->class != Cin){
+		syslog(0, logfile, "server: class %d", repp->qd->owner->class);
+		repp->flags = Runimplimented | Fresp | Fcanrec | Oquery;
+		return;
+	}
+
+	myarea = inmyarea(repp->qd->owner->name);
+	if(myarea != nil && (repp->qd->type == Tixfr || repp->qd->type == Taxfr)){
+		syslog(0, logfile, "server: request %s", rrname(repp->qd->type, tname, sizeof tname));
+		repp->flags = Runimplimented | Fresp | Fcanrec | Oquery;
+		return;
+	}
+
+	/*
+	 *  get the answer if we can
+	 */
+	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 == 0){
+		dp = dnlookup(repp->qd->owner->name, repp->qd->owner->class, 0);
+		if(dp->rr == 0)
+			if(reqp->flags & Frecurse)
+				repp->flags |= dp->nonexistent|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 == 0)
+				continue;
+	
+			repp->ns = rrlookup(nsdp, Tns, OKneg);
+			if(repp->ns){
+				/* don't pass on anything we know is wrong */
+				if(repp->ns->negative){
+					rrfreelist(repp->ns);
+					repp->ns = nil;
+				}
+				break;
+			}
+	
+			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);
+	}
+
+	/*
+	 *  add an soa to the authority section to help client with negative caching
+	 */
+	if(repp->an == nil){
+		if(myarea != nil){
+			rrcopy(myarea->soarr, &tp);
+			rrcat(&repp->ns, tp);
+		} else if(neg != nil) {
+			if(neg->negsoaowner != nil)
+				rrcat(&repp->ns, rrlookup(neg->negsoaowner, Tsoa, NOneg));
+			repp->flags |= neg->negrcode;
+		}
+	}
+
+	/*
+	 *  get rid of duplicates
+	 */
+	unique(repp->an);
+	unique(repp->ns);
+	unique(repp->ar);
+
+	rrfreelist(neg);
+
+	dncheck(nil, 1);
+}
+
+/*
+ *  satisfy a recursive request.  dnlookup will handle cnames.
+ */
+static RR*
+doextquery(DNSmsg *mp, Request *req, int recurse)
+{
+	int 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);
+
+	/* don't return soa hints as answers, it's wrong */
+	if(rp && rp->db && !rp->auth && rp->type == Tsoa)
+		rrfreelist(rp);
+
+	/* don't let negative cached entries escape */
+	neg = rrremneg(&rp);
+	rrcat(&mp->an, rp);
+	return neg;
+}
+
+static void
+hint(RR **last, RR *rp)
+{
+	RR *hp;
+
+	switch(rp->type){
+	case Tns:
+	case Tmx:
+	case Tmb:
+	case Tmf:
+	case Tmd:
+		hp = rrlookup(rp->host, Ta, NOneg);
+		if(hp == nil)
+			hp = dblookup(rp->host->name, Cin, Ta, 0, 0);
+		rrcat(last, hp);
+		break;
+	}
+}