forked from ehazlett/stellar
/
dns.go
204 lines (182 loc) · 4.33 KB
/
dns.go
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package nameserver
import (
"context"
"fmt"
"net"
"strings"
"github.com/containerd/typeurl"
api "github.com/ehazlett/stellar/api/services/nameserver/v1"
"github.com/ehazlett/stellar/api/types"
"github.com/miekg/dns"
"github.com/pkg/errors"
"github.com/sirupsen/logrus"
)
// TODO: support multiple RR per name
// TODO: add forwarder for nameserver
func (s *service) startDNSServer() error {
// TODO: make configurable
gw, err := s.gateway()
if err != nil {
return err
}
dns.HandleFunc(".", s.handler)
for _, proto := range []string{"tcp4", "udp4"} {
srv := &dns.Server{
Addr: fmt.Sprintf("%s:53", gw.String()),
Net: proto,
}
go func() {
if err := srv.ListenAndServe(); err != nil {
logrus.Errorf("error starting dns server on 53/%s", srv.Net)
}
}()
}
return nil
}
func (s *service) gateway() (net.IP, error) {
c, err := s.client()
if err != nil {
return nil, err
}
defer c.Close()
subnetCIDR, err := c.Network().AllocateSubnet(s.agent.Config().NodeName)
if err != nil {
return nil, err
}
if subnetCIDR == "" {
return nil, fmt.Errorf("unable to detect subnet for node")
}
logrus.Debugf("gateway cidr: %s", subnetCIDR)
ip, ipnet, err := net.ParseCIDR(subnetCIDR)
if err != nil {
return nil, err
}
gw := ip.Mask(ipnet.Mask)
gw[3]++
return gw, nil
}
func (s *service) handler(w dns.ResponseWriter, r *dns.Msg) {
m := new(dns.Msg)
m.SetReply(r)
m.RecursionAvailable = true
query := m.Question[0].Name
queryType := m.Question[0].Qtype
logrus.Debugf("nameserver: query=%q", query)
name := getName(query, queryType)
logrus.Debugf("nameserver: looking up %s", name)
resp, err := s.Lookup(context.Background(), &api.LookupRequest{
Query: name,
})
if err != nil {
logrus.Error(errors.Wrapf(err, "nameserver: error performing lookup for %s", name))
w.WriteMsg(m)
return
}
// forward if empty
if len(resp.Records) == 0 {
x, err := dns.Exchange(r, s.upstreamDNSAddr)
if err != nil {
logrus.Errorf("nameserver: error forwarding lookup: %+v", err)
w.WriteMsg(m)
return
}
x.SetReply(r)
w.WriteMsg(x)
return
}
// defer WriteMsg to ensure a response
defer w.WriteMsg(m)
m.Answer = []dns.RR{}
m.Extra = []dns.RR{}
for _, record := range resp.Records {
var rr dns.RR
switch record.Type {
case api.RecordType_A:
ip := net.ParseIP(string(record.Value))
rr = &dns.A{
Hdr: dns.RR_Header{
Name: fqdn(name),
Rrtype: dns.TypeA,
Class: dns.ClassINET,
Ttl: 0,
},
A: ip,
}
case api.RecordType_CNAME:
rr = &dns.CNAME{
Hdr: dns.RR_Header{
Name: fqdn(name),
Rrtype: dns.TypeCNAME,
Class: dns.ClassINET,
Ttl: 0,
},
Target: string(record.Value),
}
case api.RecordType_TXT:
rr = &dns.TXT{
Hdr: dns.RR_Header{
Name: fqdn(name),
Rrtype: dns.TypeTXT,
Class: dns.ClassINET,
Ttl: 0,
},
Txt: []string{string(record.Value)},
}
case api.RecordType_MX:
rr = &dns.MX{
Hdr: dns.RR_Header{
Name: fqdn(name),
Rrtype: dns.TypeMX,
Class: dns.ClassINET,
Ttl: 0,
},
Mx: string(record.Value),
}
case api.RecordType_SRV: // srv is unique do to the return format
v, err := typeurl.UnmarshalAny(record.Options)
if err != nil {
logrus.Errorf("ns: unmarshalling record options: %s", err)
return
}
o, ok := v.(*types.SRVOptions)
if !ok {
logrus.Error("ns: invalid type for record options; expected SRVOptions")
}
rr = &dns.SRV{
Hdr: dns.RR_Header{
Name: formatSRV(name, o),
Rrtype: dns.TypeSRV,
Class: dns.ClassINET,
Ttl: 0,
},
Target: query,
Priority: o.Priority,
Weight: o.Weight,
Port: o.Port,
}
default:
logrus.Errorf("nameserver: unsupported record type %s for %s", record.Type, name)
}
// set for answer or extra
if rr.Header().Rrtype == queryType {
m.Answer = append(m.Answer, rr)
} else {
m.Extra = append(m.Extra, rr)
}
}
}
func getName(query string, queryType uint16) string {
// adjust lookup for srv
if queryType == dns.TypeSRV {
p := strings.Split(query, ".")
v := strings.Join(p[2:], ".")
return v[:len(v)-1]
}
return query[:len(query)-1]
}
func formatSRV(name string, opts *types.SRVOptions) string {
return fmt.Sprintf("_%s._%s.%s.", opts.Service, opts.Protocol, name)
}
func fqdn(name string) string {
return name + "."
}