Use library functions for low-level name mangling in the DNS module

node/dns.go

@@ -13,7 +13,7 @@ import (
 const (
 	zoneTTL   = 21600
 	nsTTL     = 3600
-	recordTTL = 5
+	recordTTL = 300
 
 	maxRecords = 5
 )
@@ -61,7 +61,7 @@ func newDNSZone(lb *loadBalancer, origin string, nameservers []string) *dnsZone
 		soa:            soa,
 		nameservers:    nameservers,
 		origin:         origin,
-		originNumParts: len(strings.Split(origin, ".")),
+		originNumParts: dns.CountLabel(origin),
 	}
 }
 
@@ -70,8 +70,12 @@ func (d *dnsZone) ServeDNS(w dns.ResponseWriter, req *dns.Msg) {
 	ednsFromRequest(req, m)
 
 	// Only consider the first question.
+	var name string
 	q := req.Question[0]
-	name := d.getQuestionName(q)
+	if !dns.IsSubDomain(d.origin, q.Name) {
+		goto nxDomain
+	}
+	name = d.stripOrigin(q.Name)
 
 	switch {
 	case name == "" && q.Qtype == dns.TypeSOA:
@@ -149,9 +153,9 @@ func (d *dnsZone) getNodeIPs(q dns.Question) []net.IP {
 }
 
 // Strip the origin from the query.
-func (d *dnsZone) getQuestionName(q dns.Question) string {
-	lx := dns.SplitDomainName(q.Name)
-	ql := lx[0 : len(lx)-d.originNumParts]
+func (d *dnsZone) stripOrigin(name string) string {
+	lx := dns.SplitDomainName(name)
+	ql := lx[:len(lx)-d.originNumParts]
 	return strings.ToLower(strings.Join(ql, "."))
 }