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package main
import (
"github.com/vishvananda/netlink"
"github.com/miekg/dns"
"time"
"fmt"
"net"
"log"
)
type Update struct {
zone string
name string
ttl int
tsig map[string]string
tsigAlgo string
server string
timeout time.Duration
link netlink.Link
addrs map[string]Addr
}
func (u *Update) initTSIG(name string, secret string, algo string) {
u.tsig = map[string]string{name: secret}
u.tsigAlgo = algo
}
// Update state for link
func (u *Update) scan(iface string, family int) error {
link, err := netlink.LinkByName(iface)
if err != nil {
return fmt.Errorf("netlink.LinkByName %v: %v", iface, err)
}
addrs, err := netlink.AddrList(link, family)
if err != nil {
return fmt.Errorf("netlink.AddrList %v: %v", link, err)
}
// set
u.addrs = make(map[string]Addr)
for _, addr := range addrs {
u.applyLinkAddr(link, addr)
}
return nil
}
func (u *Update) applyLinkAddr(link netlink.Link, addr netlink.Addr) {
linkUp := link.Attrs().Flags & net.FlagUp != 0
if addr.Scope >= int(netlink.SCOPE_LINK) {
return
}
u.apply(addr.IP, linkUp)
}
// Update state for address
func (u *Update) apply(ip net.IP, up bool) {
if up {
log.Printf("update: up %v", ip)
u.addrs[ip.String()] = Addr{IP: ip}
} else {
log.Printf("update: down %v", ip)
delete(u.addrs, ip.String())
}
}
func (u *Update) buildRR() (rs []dns.RR) {
for _, addr := range u.addrs {
rs = append(rs, addr.buildRR(u.name, u.ttl))
}
return rs
}
func (u *Update) buildMsg() *dns.Msg {
var msg = new(dns.Msg)
msg.SetUpdate(u.zone)
msg.RemoveName([]dns.RR{&dns.RR_Header{Name:u.name}})
msg.Insert(u.buildRR())
if u.tsig != nil {
for keyName, _ := range u.tsig {
msg.SetTsig(keyName, 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(verbose bool) error {
q := u.buildMsg()
if verbose {
log.Printf("query:\n%v", q)
}
r, err := u.query(q)
if err != nil {
return err
}
if verbose {
log.Printf("answer:\n%v", r)
}
return nil
}
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