// Our shiny lookup loop
func (cq *Cq) collapsedLookup(q packet.QuestionFormat, c chan *lookupRes) {
for i := 0; i < 5; {
cres, cerr := cq.cache.Lookup(q.Name, q.Type)
if cres != nil {
c <- &lookupRes{cres, false}
break
}
if cerr != nil {
c <- &lookupRes{cerr, true}
break
}
// No such type exists in cache, but maybe we got a CNAME... horray.
cres, _ = cq.cache.Lookup(q.Name, constants.TYPE_CNAME)
if cres != nil {
if len(cres.ResourceRecord) == 1 {
// We do not support weird multi-record cnames
target_label, err := packet.ParseName(cres.ResourceRecord[0].Data)
if err == nil {
// Restart query with cname label but inherit types of original query.
target_chan := make(chan *lookupRes)
target_q := packet.QuestionFormat{Name: target_label, Type: q.Type, Class: q.Class}
go cq.collapsedLookup(target_q, target_chan)
target_res := <-target_chan
if target_res != nil {
// not a dead cname: we got the requested record -> append it to original cache reply
cres.ResourceRecord = append(cres.ResourceRecord, target_res.cres.ResourceRecord...)
}
c <- &lookupRes{cres, false}
}
}
break
}
pp := cq.advanceCache(q)
progress := cq.blockForQuery(pp)
if progress == false {
i++
}
}
// return pseudio-nil if we give up
close(c)
}
func (cq *Cq) advanceCache(q packet.QuestionFormat) *packet.ParsedPacket {
// our hardcoded, not so redundant slist
targetNS := "192.5.5.241:53"
targetXH := &packet.Namelabel{}
targetQT := q.Type
POP_LOOP:
for i := 0; ; i++ {
label := q.Name.PoppedLabel(i) // removes 'i' labels from the label list
nsrec, _ := cq.cache.Lookup(*label, constants.TYPE_NS)
if nsrec != nil { // we got an NS cache entry for this level
var candidate_cres *cache.CacheResult
var candidate_label packet.Namelabel
// loop trough all NS servers for this record
for _, candidate_data := range nsrec.ResourceRecord {
name, err := packet.ParseName(candidate_data.Data)
if err == nil {
l.Debug("NS %v handles %v", name, label)
cres, _ := cq.cache.Lookup(name, constants.TYPE_A)
if cres != nil {
candidate_cres = cres
} else {
candidate_label = name
}
}
}
// Fixme: We should try to resolve (yet unknown) nameservers
// even if we got a candidate_res as the one we are contacting
// might fail for some reason.
if candidate_cres == nil && candidate_label.Len() > 0 {
l.Debug("Looking up IP of known candidate: %v", candidate_label)
c := make(chan *lookupRes)
go cq.collapsedLookup(packet.QuestionFormat{Type: constants.TYPE_A, Class: constants.CLASS_IN, Name: candidate_label}, c)
lres := <-c
if lres != nil && lres.negative == false {
candidate_cres = lres.cres
}
}
if candidate_cres != nil {
l.Debug("We got an RR: %v", candidate_cres)
for _, v := range candidate_cres.ResourceRecord {
if v.Type != constants.TYPE_A {
l.Panic("Not an A type: %v", v)
}
targetNS = fmt.Sprintf("%d.%d.%d.%d:53", v.Data[0], v.Data[1], v.Data[2], v.Data[3])
targetXH = label
break POP_LOOP
}
}
}
if label.Len() == 1 {
break
}
}
pp := &packet.ParsedPacket{}
pp.Header.Id = uint16(rand.Uint32()) // will simply overflow
pp.Header.Opcode = constants.OP_QUERY
pp.Header.QuestionCount = 1
pp.Questions = []packet.QuestionFormat{{Name: q.Name, Class: constants.CLASS_IN, Type: targetQT}}
remoteNs, err := net.ResolveUDPAddr("udp", targetNS)
if err == nil {
l.Info("+ op=query, remote=%s, type=%d, id=%d, name=%v", targetNS, targetQT, pp.Header.Id, q.Name)
cq.conn.WriteToUDP(packet.Assemble(pp), remoteNs)
cq.sq.registerQuery(pp.Questions[0], remoteNs, targetXH)
}
return pp
}
// Lookup returns the CacheResult of given Namelabel and Type combination
// rr will be nil if there was no positive match
// re will be nil if there was no negative match
// rr == re == nil if the entry is completely unknown
func (c *Cache) Lookup(label packet.Namelabel, t uint16) (rr *CacheResult, re *CacheResult) {
key := label.ToKey()
now := time.Now()
c.Lock()
defer c.Unlock()
if c.CacheMap[key] != nil {
qtypes := []uint16{t} // the types we are going to query from the cache
ent := make([]packet.ResourceRecordFormat, 0) // the final response
if t == constants.QTYPE_ALL && len(c.CacheMap[key]) > 0 {
// special case: This was an ANY query and we DO have some data.
// As QTYPE_ALL is not a valid type, we are just going to return all rr's we got data for
qtypes = []uint16{}
for k, _ := range c.CacheMap[key] {
qtypes = append(qtypes, k)
}
}
for _, qtype := range qtypes {
if c.CacheMap[key][qtype] != nil {
for _, item := range c.CacheMap[key][qtype] {
if now.Before(item.deadline) {
ttl := uint32(item.deadline.Sub(now).Seconds())
ent = append(ent, packet.ResourceRecordFormat{Name: label, Class: constants.CLASS_IN, Type: qtype, Ttl: ttl, Data: item.data})
}
}
}
}
if len(ent) > 0 { // ensure to return a null pointer if ent is empty
rr = &CacheResult{ResourceRecord: ent, ResponseCode: constants.RC_NO_ERR}
}
}
// rr will be nil on cache miss, check if we have a negative cache entry
if rr == nil && c.MissMap[key] != nil {
mtype := t
if c.MissMap[key][constants.TYPE_SOA] != nil {
// we do have a negative soa entry, so the domain simply does not exist
// and there is no point in looking up 't'
mtype = constants.TYPE_SOA
}
if c.MissMap[key][mtype] != nil {
for _, item := range c.MissMap[key][mtype] {
if now.Before(item.deadline) {
ttl := uint32(item.deadline.Sub(now).Seconds())
// unparse fiddled-in soa label
rend := item.data[0] + 1
rlabel := item.data[1:rend]
plabel, _ := packet.ParseName(rlabel)
ent := make([]packet.ResourceRecordFormat, 0)
ent = append(ent, packet.ResourceRecordFormat{Name: plabel, Class: constants.CLASS_IN, Type: constants.TYPE_SOA, Ttl: ttl, Data: item.data[rend:]})
re = &CacheResult{ResourceRecord: ent, ResponseCode: item.rcode}
}
}
}
}
return
}