Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

feat: refactor lookup logic #161

Merged
merged 1 commit into from
May 31, 2024
Merged

feat: refactor lookup logic #161

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
123 changes: 50 additions & 73 deletions internal/dns/dns.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -68,41 +68,25 @@ func handleQuery(w dns.ResponseWriter, r *dns.Msg) {
}
}

// Check for known record for domain nameserver
records, err := state.GetState().LookupNameserverRecord(
// Check for known record from local storage
records, err := state.GetState().LookupRecords(
[]string{dns.Type(r.Question[0].Qtype).String()},
strings.TrimSuffix(r.Question[0].Name, "."),
)
if err != nil {
logger.Errorf("failed to lookup record in state: %s", err)
logger.Errorf("failed to lookup records in state: %s", err)
return
}
if records != nil {
// Assemble response
m.SetReply(r)
for k, v := range records {
k = dns.Fqdn(k)
address := net.ParseIP(v)
// A or AAAA record
if address.To4() != nil {
// IPv4
a := &dns.A{
Hdr: dns.RR_Header{
Name: k,
Rrtype: dns.TypeA,
Class: dns.ClassINET,
Ttl: 999,
},
A: address,
}
m.Answer = append(m.Answer, a)
} else {
// IPv6
aaaa := &dns.AAAA{
Hdr: dns.RR_Header{Name: k, Rrtype: dns.TypeAAAA, Class: dns.ClassINET, Ttl: 999},
AAAA: address,
}
m.Answer = append(m.Answer, aaaa)
for _, tmpRecord := range records {
tmpRR, err := stateRecordToDnsRR(tmpRecord)
if err != nil {
logger.Errorf("failed to convert state record to dns.RR: %s", err)
return
}
m.Answer = append(m.Answer, tmpRR)
}
// Send response
if err := w.WriteMsg(m); err != nil {
Expand All @@ -112,6 +96,7 @@ func handleQuery(w dns.ResponseWriter, r *dns.Msg) {
return
}

// Check for any NS records for parent domains from local storage
nameserverDomain, nameservers, err := findNameserversForDomain(
r.Question[0].Name,
)
Expand Down Expand Up @@ -182,13 +167,52 @@ func handleQuery(w dns.ResponseWriter, r *dns.Msg) {
return
}

// Query fallback servers, if configured
if len(cfg.Dns.FallbackServers) > 0 {
// Pick random fallback server
fallbackServer := randomFallbackServer()
// Pass along query to chosen fallback server
resp, err := doQuery(r, fallbackServer, false)
if err != nil {
// Send failure response
m.SetRcode(r, dns.RcodeServerFailure)
if err := w.WriteMsg(m); err != nil {
logger.Errorf("failed to write response: %s", err)
}
logger.Errorf("failed to query domain nameserver: %s", err)
return
} else {
copyResponse(r, resp, m)
// Send response
if err := w.WriteMsg(m); err != nil {
logger.Errorf("failed to write response: %s", err)
}
return
}
}

// Return NXDOMAIN if we have no information about the requested domain or any of its parents
m.SetRcode(r, dns.RcodeNameError)
if err := w.WriteMsg(m); err != nil {
logger.Errorf("failed to write response: %s", err)
}
}

func stateRecordToDnsRR(record state.DomainRecord) (dns.RR, error) {
tmpTtl := ""
if record.Ttl > 0 {
tmpTtl = fmt.Sprintf("%d", record.Ttl)
}
tmpRR := fmt.Sprintf(
"%s %s IN %s %s",
record.Lhs,
tmpTtl,
record.Type,
record.Rhs,
)
return dns.NewRR(tmpRR)
}

func copyResponse(req *dns.Msg, srcResp *dns.Msg, destResp *dns.Msg) {
// Copy relevant data from original request and source response into destination response
destResp.SetRcode(req, srcResp.MsgHdr.Rcode)
Expand Down Expand Up @@ -279,8 +303,6 @@ func doQuery(msg *dns.Msg, address string, recursive bool) (*dns.Msg, error) {
func findNameserversForDomain(
recordName string,
) (string, map[string][]net.IP, error) {
cfg := config.GetConfig()

// Split record name into labels and lookup each domain and parent until we get a hit
queryLabels := dns.SplitDomainName(recordName)

Expand Down Expand Up @@ -314,51 +336,6 @@ func findNameserversForDomain(
}
}

// Query fallback servers, if configured
if len(cfg.Dns.FallbackServers) > 0 {
// Pick random fallback server
fallbackServer := randomFallbackServer()
for startLabelIdx := 0; startLabelIdx < len(queryLabels); startLabelIdx++ {
lookupDomainName := dns.Fqdn(
strings.Join(queryLabels[startLabelIdx:], "."),
)
m := createQuery(lookupDomainName, dns.TypeNS)
in, err := doQuery(m, fallbackServer, false)
if err != nil {
return "", nil, err
}
if in.Rcode == dns.RcodeSuccess {
if len(in.Answer) > 0 {
ret := map[string][]net.IP{}
for _, answer := range in.Answer {
switch v := answer.(type) {
case *dns.NS:
ns := v.Ns
ret[ns] = make([]net.IP, 0)
// Query for matching A/AAAA records
m2 := createQuery(ns, dns.TypeA)
in2, err := doQuery(m2, fallbackServer, false)
if err != nil {
return "", nil, err
}
for _, answer2 := range in2.Answer {
switch v := answer2.(type) {
case *dns.A:
ret[ns] = append(ret[ns], v.A)
case *dns.AAAA:
ret[ns] = append(ret[ns], v.AAAA)
}
}
}
}
if len(ret) > 0 {
return lookupDomainName, ret, nil
}
}
}
}
}

return "", nil, nil
}

Expand Down
38 changes: 0 additions & 38 deletions internal/state/state.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -259,44 +259,6 @@ func (s *State) LookupRecords(recordTypes []string, recordName string) ([]Domain
return ret, nil
}

// LookupNameserverRecord searches the domain nameserver entries for one matching the requested record
func (s *State) LookupNameserverRecord(
recordName string,
) (map[string]string, error) {
ret := map[string]string{}
err := s.db.View(func(txn *badger.Txn) error {
opts := badger.DefaultIteratorOptions
// Makes key scans faster
opts.PrefetchValues = false
it := txn.NewIterator(opts)
defer it.Close()
for it.Rewind(); it.Valid(); it.Next() {
item := it.Item()
k := item.Key()
if strings.HasSuffix(
string(k),
fmt.Sprintf("_nameserver_%s", recordName),
) {
err := item.Value(func(v []byte) error {
ret[recordName] = string(v)
return nil
})
if err != nil {
return err
}
}
}
return nil
})
if err != nil {
return nil, err
}
if len(ret) == 0 {
return nil, nil
}
return ret, nil
}

func GetState() *State {
return globalState
}
Expand Down