func TestDedup(t *testing.T) {
m := new(dns.Msg)
m.Answer = []dns.RR{
newA("svc.ns.kubernetes.local. IN A 3.3.3.3"),
newA("svc.ns.kubernetes.local. IN A 2.2.2.2"),
newA("svc.ns.kubernetes.local. IN A 3.3.3.3"),
newA("svc.ns.kubernetes.local. IN A 2.2.2.2"),
newA("svc.ns.kubernetes.local. IN A 1.1.1.1"),
newA("svc.ns.kubernetes.local. IN A 1.1.1.1"),
}
s := &server{}
m = s.dedup(m)
sort.Sort(rrSet(m.Answer))
if len(m.Answer) != 3 {
t.Fatalf("failing dedup: should have collapsed it to 3 records")
}
if dns.Field(m.Answer[0], 1) != "1.1.1.1" || dns.Field(m.Answer[1], 1) != "2.2.2.2" ||
dns.Field(m.Answer[2], 1) != "3.3.3.3" {
t.Fatalf("failing dedup: %s", m)
}
}
// dedup will de-duplicate a message on a per section basis.
// Multiple identical (same name, class, type and rdata) RRs will be coalesced into one.
func (s *server) dedup(m *dns.Msg) *dns.Msg {
// Answer section
ma := make(map[string]dns.RR)
for _, a := range m.Answer {
// Or use Pack()... Think this function also could be placed in go dns.
s1 := a.Header().Name
s1 += strconv.Itoa(int(a.Header().Class))
s1 += strconv.Itoa(int(a.Header().Rrtype))
// there can only be one CNAME for an ownername
if a.Header().Rrtype == dns.TypeCNAME {
if _, ok := ma[s1]; ok {
// already exist, randomly overwrite if roundrobin is true
// Note: even with roundrobin *off* this depends on the
// order we get the names.
if s.config.RoundRobin && dns.Id()%2 == 0 {
ma[s1] = a
continue
}
}
ma[s1] = a
continue
}
for i := 1; i <= dns.NumField(a); i++ {
s1 += dns.Field(a, i)
}
ma[s1] = a
}
// Only is our map is smaller than the #RR in the answer section we should reset the RRs
// in the section it self
if len(ma) < len(m.Answer) {
i := 0
for _, v := range ma {
m.Answer[i] = v
i++
}
m.Answer = m.Answer[:len(ma)]
}
// Additional section
me := make(map[string]dns.RR)
for _, e := range m.Extra {
s1 := e.Header().Name
s1 += strconv.Itoa(int(e.Header().Class))
s1 += strconv.Itoa(int(e.Header().Rrtype))
// there can only be one CNAME for an ownername
if e.Header().Rrtype == dns.TypeCNAME {
if _, ok := me[s1]; ok {
// already exist, randomly overwrite if roundrobin is true
if s.config.RoundRobin && dns.Id()%2 == 0 {
me[s1] = e
continue
}
}
me[s1] = e
continue
}
for i := 1; i <= dns.NumField(e); i++ {
s1 += dns.Field(e, i)
}
me[s1] = e
}
if len(me) < len(m.Extra) {
i := 0
for _, v := range me {
m.Extra[i] = v
i++
}
m.Extra = m.Extra[:len(me)]
}
return m
}