A simple non-recursive DNS server written in Go.
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package realm
import (
"fmt"
"os"
"github.com/miekg/dns"
)
type Zone struct {
records []dns.RR
}
func ParseZone(filename string) (*Zone, error) {
var zone *Zone
var err error
zone = &Zone{
records: make([]dns.RR, 0),
}
var file *os.File
file, err = os.Open(filename)
if err != nil {
return nil, fmt.Errorf("could not parse zone file \"%s\": \"%s\"", filename, err)
}
defer file.Close()
var tokens chan *dns.Token
tokens = dns.ParseZone(file, "", "")
for token := range tokens {
if token.Error != nil {
return nil, fmt.Errorf("could not parse zone file \"%s\": \"%s\"", filename, token.Error)
}
zone.records = append(zone.records, token.RR)
}
return zone, nil
}
func (zone *Zone) Lookup(name string, reqType uint16, reqClass uint16) []dns.RR {
name = dns.Fqdn(name)
var records []dns.RR = make([]dns.RR, 0)
for _, record := range zone.records {
var header *dns.RR_Header = record.Header()
if header.Name != name || (header.Class != reqClass && reqClass != dns.ClassANY) {
continue
}
if reqType == dns.TypeANY || reqType == header.Rrtype {
records = append(records, record)
} else if header.Rrtype == dns.TypeCNAME {
records = append(records, record)
var cname *dns.CNAME = record.(*dns.CNAME)
var cnameRecords []dns.RR = zone.Lookup(dns.Fqdn(cname.Target), reqType, reqClass)
records = append(records, cnameRecords...)
}
}
return records
}