1 files changed, 143 insertions, 0 deletions
diff --git a/update.go b/update.go
new file mode 100644
index 0000000..c0a0c00
--- /dev/null
+++ b/update.go
@@ -0,0 +1,143 @@
+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
+}