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package dns
import (
"context"
"fmt"
"time"
"github.com/miekg/dns"
"code.crute.me/mcrute/go_ddns_manager/bind"
)
type DNSClient struct {
Server string
RecursiveResolvers []string
PollTimeout time.Duration
}
type DNSTransaction struct {
zone *bind.Zone
key *bind.Key
msg *dns.Msg
}
func (t *DNSTransaction) Upsert(rrs ...RR) *DNSTransaction {
t.RemoveAll(rrs...).Insert(rrs...)
return t
}
func (t *DNSTransaction) Insert(rrs ...RR) *DNSTransaction {
t.msg.Insert(toRRSet(t.zone, rrs...))
return t
}
func (t *DNSTransaction) Remove(rrs ...RR) *DNSTransaction {
t.msg.Remove(toRRSet(t.zone, rrs...))
return t
}
func (t *DNSTransaction) RemoveAll(rrs ...RR) *DNSTransaction {
t.msg.RemoveRRset(toRRSet(t.zone, rrs...))
return t
}
func (c *DNSClient) AXFR(zone *bind.Zone) (chan *dns.Envelope, error) {
k := zone.Keys()[0]
t := &dns.Transfer{TsigSecret: k.AsMap()} // Always uses tcp
m := &dns.Msg{}
m.SetAxfr(zone.Name)
k.Sign(m)
return t.In(m, c.Server)
}
func (c *DNSClient) ReadRemoteZone(zone *bind.Zone) ([]RR, error) {
rrs := []RR{}
seenSoa := false
data, err := c.AXFR(zone)
if err != nil {
return nil, err
}
for rd := range data {
for _, r := range rd.RR {
switch dr := FromDNS(r).(type) {
case *SOA:
// Transfers have 2 SOA records, exclude the last one
if !seenSoa {
rrs = append(rrs, dr)
seenSoa = true
}
case RR:
rrs = append(rrs, dr)
default:
// This should only be possible if we somehow are
// missing generated DNS data types.
return nil, fmt.Errorf("Invalid return type")
}
}
}
return rrs, nil
}
func (c *DNSClient) StartUpdate(zone *bind.Zone) *DNSTransaction {
m := &dns.Msg{}
m.SetUpdate(zone.Name)
return &DNSTransaction{
zone: zone,
key: zone.Keys()[0],
msg: m,
}
}
func (c *DNSClient) QueryRecursive(zone *bind.Zone, fqdn string, rtype uint16) *DNSTransaction {
m := &dns.Msg{}
m.RecursionDesired = true
m.SetQuestion(fqdn, rtype)
return &DNSTransaction{
zone: zone,
key: zone.Keys()[0],
msg: m,
}
}
func (c *DNSClient) SendUpdate(t *DNSTransaction) error {
udp := &dns.Client{Net: "udp", TsigSecret: t.key.AsMap()}
tcp := &dns.Client{Net: "tcp", TsigSecret: t.key.AsMap()}
t.msg.SetEdns0(4096, false)
t.key.Sign(t.msg)
in, _, err := udp.Exchange(t.msg, c.Server)
if in != nil && in.Truncated {
// If the TCP request succeeds, the err will reset to nil
in, _, err = tcp.Exchange(t.msg, c.Server)
}
if err != nil {
return err
}
return nil
}
func (c *DNSClient) SendQuery(t *DNSTransaction) ([]dns.RR, error) {
udp := &dns.Client{Net: "udp", TsigSecret: t.key.AsMap()}
tcp := &dns.Client{Net: "tcp", TsigSecret: t.key.AsMap()}
t.msg.SetEdns0(4096, false)
t.key.Sign(t.msg)
in, _, err := udp.Exchange(t.msg, c.Server)
if in != nil && in.Truncated {
// If the TCP request succeeds, the err will reset to nil
in, _, err = tcp.Exchange(t.msg, c.Server)
}
if err != nil {
return nil, err
}
return in.Answer, nil
}
// TODO: Copied from the letsencrypt service, merge this into existing functions
func (c *DNSClient) sendReadQuery(ctx context.Context, fqdn string, rtype uint16, nameserver string) (*dns.Msg, error) {
udp := &dns.Client{Net: "udp"}
tcp := &dns.Client{Net: "tcp"}
m := &dns.Msg{}
m.SetQuestion(fqdn, rtype)
m.SetEdns0(4096, false)
m.RecursionDesired = true
in, _, err := udp.ExchangeContext(ctx, m, nameserver)
if in != nil && in.Truncated {
// If the TCP request succeeds, the err will reset to nil
in, _, err = tcp.ExchangeContext(ctx, m, nameserver)
}
if err != nil {
return nil, err
}
return in, err
}
func (c *DNSClient) WaitForDNSPropagation(ctx context.Context, fqdn, value string) error {
if c.RecursiveResolvers == nil {
return fmt.Errorf("DNSClient.WaitForDNSPropagation: RecursiveResolvers not set")
}
pt := c.PollTimeout
if pt == 0 {
pt = 3 * time.Second
}
timer := time.NewTicker(pt)
defer timer.Stop()
for {
// Give the server the initial timout to satisfy the request
select {
case <-ctx.Done():
return fmt.Errorf("DNSClient.WaitForDNSPropagation: context has expired, polling terminated")
case <-timer.C:
}
ok_count := 0
for _, rs := range c.RecursiveResolvers {
r, err := c.sendReadQuery(ctx, fqdn, dns.TypeTXT, rs)
if err != nil {
return err
}
if len(r.Answer) > 0 {
if r.Answer[0].(*dns.TXT).Txt[0] == value {
ok_count++
}
}
}
if ok_count == len(c.RecursiveResolvers) {
return nil
}
}
}
|
