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)
}
}
}
// Puts given entry into c's Cache
func (c *Cache) Put(p *packet.ParsedPacket, ns *net.UDPAddr) {
if len(p.Questions) != 1 {
return
}
// Check if we have a CrossHierarchy (XH) label
// a nil value indicates that this reply is invalid
xhlabel := c.VrfyCallback(p.Questions[0], ns)
if xhlabel == nil {
l.Info("Dropping unexpected reply from %v", ns)
return
}
qname := p.Questions[0].Name
qtype := p.Questions[0].Type
isrc := InjectSource{Name: qname, Type: qtype}
if p.Header.Authoritative == true {
for _, n := range p.Answers {
if n.Class == constants.CLASS_IN && n.Name.IsChildOf(xhlabel) {
c.injectPositiveItem(isrc, n)
}
}
}
// Scan if there any additional A or AAA records
for _, n := range p.Additionals {
if n.Class == constants.CLASS_IN && n.Name.IsChildOf(xhlabel) {
if n.Type == constants.TYPE_A || n.Type == constants.TYPE_AAAA {
c.injectPositiveItem(isrc, n)
}
}
}
for _, n := range p.Nameservers {
if n.Class == constants.CLASS_IN && n.Name.IsChildOf(xhlabel) {
if n.Type == constants.TYPE_NS {
c.injectPositiveItem(isrc, n)
}
if p.Header.AnswerCount == 0 && n.Type == constants.TYPE_SOA {
c.injectNegativeItem(isrc, n, p.Header.ResponseCode)
}
}
}
}
// injectNegativeItem marks given label as non existing. rc defines the return code
// item is supposed to be a SOA
func (c *Cache) injectNegativeItem(isrc InjectSource, item packet.ResourceRecordFormat, rcode uint8) {
if item.Type != constants.TYPE_SOA {
panic("Not a SOA!")
}
// Unbound uses the RR TTL while some other caches seem to use SOA.MINTTL ?
// We are going unbound-style but emit a warning
soaTtl := packet.ParseSoaTtl(item.Data)
if item.Ttl != soaTtl {
l.Info("SOA ttl mismatch: %d != %d (isrc=%+v)", item.Ttl, soaTtl, isrc)
}
switch {
case item.Ttl < 5:
item.Ttl = 5
case item.Ttl > 600:
item.Ttl = 600
}
// xxx: The cache key for this entry should not be the response label but the
// question (isrc) label. However: The response label needs to be preserved
// so we are prefixing it to the raw data for now (until we have a nicer API)
rawlabel := packet.EncodeName(item.Name)
item.Data = append(rawlabel, item.Data...)
item.Data = append([]byte{byte(len(rawlabel))}, item.Data...)
item.Name = isrc.Name // use the looked up label as cache key, not the SOA label
// We shall also use the source TYPE *unless* we are storing an NXDOMAIN entry
if rcode != constants.RC_NAME_ERR {
item.Type = isrc.Type
} else {
// this was an NXDOMAIN -> a negative SOA entry signals that NO RRs exist
item.Type = constants.TYPE_SOA
}
c.injectInternal(c.MissMap, isrc, item, rcode)
}
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
}