scan interface addresses, and send nsupdate

3 files changed, 279 insertions, 0 deletions

diff --git a/addr.go b/addr.go
new file mode 100644
index 0000000..080f11b
--- /dev/null
+++ b/addr.go
@@ -0,0 +1,29 @@
+package main
+
+import (
+	"net"
+	"github.com/miekg/dns"
+)
+
+type Addr struct {
+	IP		net.IP
+}
+
+func (addr Addr) buildRR(name string, ttl int) dns.RR {
+	if ip4 := addr.IP.To4(); ip4 != nil {
+		return &dns.A{
+			Hdr: dns.RR_Header{Name: name, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: uint32(ttl)},
+			A:	 ip4,
+		}
+	}
+
+	if ip6 := addr.IP.To16(); ip6 != nil {
+		return &dns.AAAA{
+			Hdr:  dns.RR_Header{Name: name, Rrtype: dns.TypeAAAA, Class: dns.ClassINET, Ttl: uint32(ttl)},
+			AAAA: ip6,
+		}
+	}
+
+	return nil
+}
+
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..fe7cd64
--- /dev/null
+++ b/main.go
@@ -0,0 +1,107 @@
+package main
+
+import (
+	"github.com/jessevdk/go-flags"
+	"github.com/vishvananda/netlink"
+	"github.com/miekg/dns"
+	"net"
+	"fmt"
+	"log"
+	"os"
+	"time"
+)
+
+// zero value is unspec=all
+type Family int
+
+func (f *Family) UnmarshalFlag(value string) error {
+	switch (value) {
+	case "inet", "ipv4":
+		*f = netlink.FAMILY_V4
+	case "inet6", "ipv6":
+		*f = netlink.FAMILY_V6
+	default:
+		return fmt.Errorf("Invalid --family=%v", value)
+	}
+
+	return nil
+}
+
+const TSIG_FUDGE_SECONDS = 300
+type TSIGAlgorithm string
+
+func (t *TSIGAlgorithm) UnmarshalFlag(value string) error {
+	switch (value) {
+	case "hmac-md5", "md5":
+		*t = dns.HmacMD5
+	case "hmac-sha1", "sha1":
+		*t = dns.HmacSHA1
+	case "hmac-sha256", "sha256":
+		*t = dns.HmacSHA256
+	case "hmac-sha512", "sha512":
+		*t = dns.HmacSHA512
+	default:
+		return fmt.Errorf("Invalid --tsig-algorithm=%v", value)
+	}
+
+	return nil
+}
+
+type Options struct {
+	Verbose			bool	`long:"verbose" short:"v"`
+
+	Interface		string	`long:"interface" short:"i" value-name:"IFACE" description:"Use address from interface"`
+	InterfaceFamily	Family	`long:"interface-family"`
+
+	Server		string	`long:"server" value-name:"HOST[:PORT]"`
+	Timeout		time.Duration `long:"timeout" value-name:"DURATION" default:"10s"`
+	TSIGName	string	`long:"tsig-name"`
+	TSIGSecret	string	`long:"tsig-secret" env:"TSIG_SECRET"`
+	TSIGAlgorithm TSIGAlgorithm `long:"tsig-algorithm" default:"hmac-sha1."`
+
+	Zone		string	`long:"zone" description:"Zone to update"`
+	Name		string	`long:"name" description:"Name to update"`
+	TTL			int		`long:"ttl" default:"60"`
+}
+
+func main() {
+	var options Options
+
+	if args, err := flags.Parse(&options); err != nil {
+		log.Fatalf("flags.Parse: %v", err)
+		os.Exit(1)
+	} else if len(args) > 0 {
+		log.Fatalf("Usage: no args")
+		os.Exit(1)
+	}
+
+	var update = &Update{
+		zone:	 dns.Fqdn(options.Zone),
+		name:	 dns.Fqdn(options.Name),
+		ttl:	 options.TTL,
+		timeout: options.Timeout,
+	}
+
+	if _, _, err := net.SplitHostPort(options.Server); err == nil {
+		update.server = options.Server
+	} else {
+		update.server = net.JoinHostPort(options.Server, "53")
+	}
+
+	if options.TSIGName != "" {
+		log.Printf("using TSIG: %v (algo=%v)", options.TSIGName, options.TSIGAlgorithm)
+
+		update.initTSIG(dns.Fqdn(options.TSIGName), options.TSIGSecret, string(options.TSIGAlgorithm))
+	}
+
+	// run
+	if options.Interface == "" {
+
+	} else if err := update.scan(options.Interface, int(options.InterfaceFamily)); err != nil {
+		log.Fatalf("scan: %v", err)
+	}
+
+	if err := update.update(options.Verbose); err != nil {
+		log.Fatalf("update: %v", err)
+	}
+}
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
+}