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|
package main
import (
"fmt"
"github.com/miekg/dns"
"log"
"net"
"time"
)
type updateState struct {
updateZone string
removeNames []dns.RR
inserts []dns.RR
}
type Update struct {
ttl int
timeout time.Duration
retry time.Duration
verbose bool
zone string
name string
tsig map[string]string
tsigAlgo TSIGAlgorithm
server string
updateChan chan updateState
doneChan chan error
}
func (u *Update) Init(name string, zone string, server string) error {
if name == "" {
return fmt.Errorf("Missing name")
} else {
u.name = dns.Fqdn(name)
}
if zone == "" {
// guess
if labels := dns.Split(u.name); len(labels) > 1 {
u.zone = u.name[labels[1]:]
} else {
return fmt.Errorf("Missing zone")
}
} else {
u.zone = dns.Fqdn(zone)
}
if server == "" {
if server, err := discoverZoneServer(u.zone); err != nil {
return fmt.Errorf("Failed to discver server")
} else {
log.Printf("discover server=%v", server)
u.server = net.JoinHostPort(server, "53")
}
} else {
if _, _, err := net.SplitHostPort(server); err == nil {
u.server = server
} else {
u.server = net.JoinHostPort(server, "53")
}
}
return nil
}
func (u *Update) InitTSIG(name string, secret string, algo TSIGAlgorithm) {
u.tsig = map[string]string{dns.Fqdn(name): secret}
u.tsigAlgo = algo
}
func (u *Update) buildAddr(ip net.IP) dns.RR {
if ip4 := ip.To4(); ip4 != nil {
return &dns.A{
Hdr: dns.RR_Header{Name: u.name, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: uint32(u.ttl)},
A: ip4,
}
}
if ip6 := ip.To16(); ip6 != nil {
return &dns.AAAA{
Hdr: dns.RR_Header{Name: u.name, Rrtype: dns.TypeAAAA, Class: dns.ClassINET, Ttl: uint32(u.ttl)},
AAAA: ip6,
}
}
return nil
}
func (u *Update) buildState(addrs *AddrSet) (state updateState, err error) {
state.updateZone = u.zone
state.removeNames = []dns.RR{
&dns.RR_Header{Name: u.name},
}
addrs.Each(func(ip net.IP) {
state.inserts = append(state.inserts, u.buildAddr(ip))
})
return
}
func (u *Update) buildQuery(state updateState) *dns.Msg {
var msg = new(dns.Msg)
msg.SetUpdate(state.updateZone)
msg.RemoveName(state.removeNames)
msg.Insert(state.inserts)
if u.tsig != nil {
for keyName, _ := range u.tsig {
msg.SetTsig(keyName, string(u.tsigAlgo), TSIG_FUDGE_SECONDS, time.Now().Unix())
}
}
return msg
}
func (u *Update) query(msg *dns.Msg) (*dns.Msg, error) {
var client = new(dns.Client)
client.DialTimeout = u.timeout
client.ReadTimeout = u.timeout
client.WriteTimeout = u.timeout
if u.tsig != nil {
client.TsigSecret = u.tsig
}
msg, _, err := client.Exchange(msg, u.server)
if err != nil {
return msg, fmt.Errorf("dns:Client.Exchange ... %v: %v", u.server, err)
}
if msg.Rcode == dns.RcodeSuccess {
return msg, nil
} else {
return msg, fmt.Errorf("rcode=%v", dns.RcodeToString[msg.Rcode])
}
}
func (u *Update) update(state updateState) error {
q := u.buildQuery(state)
if u.verbose {
log.Printf("update query:\n%v", q)
} else {
log.Printf("update query...")
}
r, err := u.query(q)
if err != nil {
return err
}
if u.verbose {
log.Printf("update answer:\n%v", r)
} else {
log.Printf("update answer")
}
return nil
}
func (u *Update) run() {
var state updateState
var retry = 0
var retryTimer = time.NewTimer(time.Duration(0))
var updateChan = u.updateChan
var updateError error
defer func() { u.doneChan <- updateError }()
for {
select {
case updateState, running := <-updateChan:
if running {
// Update() called
state = updateState
} else if retry > 0 {
// Done() called, but still waiting for retry...
updateChan = nil
continue
} else {
// Done() called, no retrys or updates remaining
return
}
case <-retryTimer.C:
if retry == 0 {
// spurious timer event..
continue
}
// trigger retry
}
if err := u.update(state); err != nil {
log.Printf("update (retry=%v) error: %v", retry, err)
updateError = err
retry++
} else {
// success
updateError = nil
retry = 0
}
if retry == 0 && updateChan == nil {
// done, no more updates
return
} else if retry == 0 {
// wait for next update
retryTimer.Stop()
} else {
retryTimeout := time.Duration(retry * int(u.retry))
// wait for next retry
// TODO: exponential backoff?
retryTimer.Reset(retryTimeout)
log.Printf("update retry in %v...", retryTimeout)
}
}
}
func (u *Update) Start() {
u.updateChan = make(chan updateState)
go u.run()
}
func (u *Update) Update(addrs *AddrSet) error {
if state, err := u.buildState(addrs); err != nil {
return err
} else {
u.updateChan <- state
}
return nil
}
func (u *Update) Done() error {
u.doneChan = make(chan error)
close(u.updateChan)
return <-u.doneChan
}
|
