func (cq *Cq) clientLookup(cr *clientRequest) {
// Ensure that this query makes some sense
if len(cr.Query.Questions) == 1 {
q := cr.Query.Questions[0]
c := make(chan *lookupRes)
go cq.collapsedLookup(q, c)
lres := <-c
l.Debug("final lookup reply -> %v", lres)
if lres != nil { // fixme: error
cres := lres.cres
p := &packet.ParsedPacket{}
p.Header.Id = cr.Query.Header.Id
p.Header.Response = true
p.Header.ResponseCode = cres.ResponseCode
p.Questions = cr.Query.Questions
if lres.negative {
p.Nameservers = append(p.Nameservers, cres.ResourceRecord...)
} else {
p.Answers = append(p.Answers, cres.ResourceRecord...)
}
cq.conn.WriteToUDP(packet.Assemble(p), cr.RemoteAddr)
} else {
l.Info("Lookup returned an error, should send it back to client (fixme): %+v", lres)
}
} else {
l.Info("Dropping nonsense query")
}
}
func main() {
flag.Parse()
listenStr := fmt.Sprintf(":%d", *listenPort)
l.Info("Starting up, listening on %s", listenStr)
listenAddr, err := net.ResolveUDPAddr("udp", listenStr)
if err != nil {
l.Panic("ResolveUDPAddr failed: %v", err)
}
conn, err := net.ListenUDP("udp", listenAddr)
if err != nil {
l.Panic("listen failed: %v", err)
}
buf := make([]byte, constants.MAX_SIZE_UDP) // Upper limit as defined by RFC 1035 2.3.4
nc := cache.NewNameCache()
sq := queue.NewServerQueue(nc)
cq := queue.NewClientQueue(conn, nc, sq)
for {
nread, remoteAddr, err := conn.ReadFromUDP(buf)
if err != nil || nread < constants.FIX_SIZE_HEADER {
l.Debug("%v dropping malformed datagram. Size=%d, err=%v", remoteAddr, nread, err)
continue
}
p, err := packet.Parse(buf[0:nread])
if err != nil {
l.Debug("%v failed to parse datagram, err=%v", remoteAddr, err)
continue
}
if p.Header.Response == false && p.Header.Opcode == constants.OP_QUERY && p.Header.RecDesired {
// This is a query, requesting recursion
cq.AddClientRequest(p, remoteAddr)
} else if p.Header.Response == true && p.Header.Opcode == constants.OP_QUERY {
// A reply, try to put it into our cache
nc.Put(p, remoteAddr)
} else {
// DOES NOT COMPUTE.
l.Info("%v dropped packet", remoteAddr)
}
}
}
func (cq *Cq) blockForQuery(pp *packet.ParsedPacket) bool {
cbi := &putCbItem{Key: pp.Questions[0].Name.ToKey(), Type: pp.Questions[0].Type}
key := cbi.ToString()
cq.Lock()
c := make(chan bool)
if cq.inflight[key] == nil {
cq.inflight[key] = make([]chan bool, 0)
}
cq.inflight[key] = append(cq.inflight[key], c)
cq.Unlock()
l.Debug("Blocking for progress on %s", key)
select {
case <-c:
l.Debug("%s progressed", key)
return true
case <-time.After(time.Second * 2):
l.Debug("%s timed out!", key)
return false
}
}
func (cq *Cq) handlePutCallback(isrc cache.InjectSource) {
cbi := &putCbItem{Key: isrc.Name.ToKey(), Type: isrc.Type}
key := cbi.ToString()
cq.Lock()
if cq.inflight[key] != nil {
for _, c := range cq.inflight[key] {
l.Debug("Broadcasting progress on %s", key)
close(c)
}
cq.inflight[key] = nil
}
cq.Unlock()
}
// Internal implementation of cache who works on multiple maps
func (c *Cache) injectInternal(m map[string]cmap, isrc InjectSource, item packet.ResourceRecordFormat, rcode uint8) {
key := item.Name.ToKey()
t := item.Type
data := item.Data
ttl := item.Ttl
c.Lock()
defer c.Unlock()
if m[key] == nil {
m[key] = make(cmap, 0)
}
if m[key][t] == nil {
m[key][t] = make(centry, 0)
}
l.Debug("+ cache inject: %+v", item)
cpy := make([]byte, len(data))
copy(cpy, data)
m[key][t][string(data)] = citem{data: cpy, deadline: time.Now().Add(time.Duration(ttl) * time.Second), rcode: rcode}
c.notify(isrc)
}
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
}
