func ExamplePrivateHandle() {
dns.PrivateHandle("APAIR", TypeAPAIR, NewAPAIR)
defer dns.PrivateHandleRemove(TypeAPAIR)
rr, err := dns.NewRR("miek.nl. APAIR (1.2.3.4 1.2.3.5)")
if err != nil {
log.Fatal("could not parse APAIR record: ", err)
}
fmt.Println(rr)
// Output: miek.nl. 3600 IN APAIR 1.2.3.4 1.2.3.5
m := new(dns.Msg)
m.Id = 12345
m.SetQuestion("miek.nl.", TypeAPAIR)
m.Answer = append(m.Answer, rr)
fmt.Println(m)
// ;; opcode: QUERY, status: NOERROR, id: 12345
// ;; flags: rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
//
// ;; QUESTION SECTION:
// ;miek.nl. IN APAIR
//
// ;; ANSWER SECTION:
// miek.nl. 3600 IN APAIR 1.2.3.4 1.2.3.5
}
// parsePacket is used to parse an incoming packet
func (s *Server) parsePacket(packet []byte, from net.Addr) error {
var msg dns.Msg
if err := msg.Unpack(packet); err != nil {
log.Printf("[ERR] mdns: Failed to unpack packet: %v", err)
return err
}
return s.handleQuery(&msg, from)
}
// sendQuery is used to multicast a query out
func (c *client) sendQuery(q *dns.Msg) error {
buf, err := q.Pack()
if err != nil {
return err
}
if c.ipv4UnicastConn != nil {
c.ipv4UnicastConn.WriteToUDP(buf, ipv4Addr)
}
if c.ipv6UnicastConn != nil {
c.ipv6UnicastConn.WriteToUDP(buf, ipv6Addr)
}
return nil
}
// sendResponse is used to send a response packet
func (s *Server) sendResponse(resp *dns.Msg, from net.Addr, unicast bool) error {
// TODO(reddaly): Respect the unicast argument, and allow sending responses
// over multicast.
buf, err := resp.Pack()
if err != nil {
return err
}
// Determine the socket to send from
addr := from.(*net.UDPAddr)
if addr.IP.To4() != nil {
_, err = s.ipv4List.WriteToUDP(buf, addr)
return err
} else {
_, err = s.ipv6List.WriteToUDP(buf, addr)
return err
}
}
// Retrieve the MX records for miek.nl.
func ExampleMX() {
config, _ := dns.ClientConfigFromFile("/etc/resolv.conf")
c := new(dns.Client)
m := new(dns.Msg)
m.SetQuestion("miek.nl.", dns.TypeMX)
m.RecursionDesired = true
r, _, err := c.Exchange(m, config.Servers[0]+":"+config.Port)
if err != nil {
return
}
if r.Rcode != dns.RcodeSuccess {
return
}
for _, a := range r.Answer {
if mx, ok := a.(*dns.MX); ok {
fmt.Printf("%s\n", mx.String())
}
}
}
// recv is used to receive until we get a shutdown
func (c *client) recv(l *net.UDPConn, msgCh chan *dns.Msg) {
if l == nil {
return
}
buf := make([]byte, 65536)
for !c.closed {
n, err := l.Read(buf)
if err != nil {
log.Printf("[ERR] mdns: Failed to read packet: %v", err)
continue
}
msg := new(dns.Msg)
if err := msg.Unpack(buf[:n]); err != nil {
log.Printf("[ERR] mdns: Failed to unpack packet: %v", err)
continue
}
select {
case msgCh <- msg:
case <-c.closedCh:
return
}
}
}
// Retrieve the DNSKEY records of a zone and convert them
// to DS records for SHA1, SHA256 and SHA384.
func ExampleDS(zone string) {
config, _ := dns.ClientConfigFromFile("/etc/resolv.conf")
c := new(dns.Client)
m := new(dns.Msg)
if zone == "" {
zone = "miek.nl"
}
m.SetQuestion(dns.Fqdn(zone), dns.TypeDNSKEY)
m.SetEdns0(4096, true)
r, _, err := c.Exchange(m, config.Servers[0]+":"+config.Port)
if err != nil {
return
}
if r.Rcode != dns.RcodeSuccess {
return
}
for _, k := range r.Answer {
if key, ok := k.(*dns.DNSKEY); ok {
for _, alg := range []uint8{dns.SHA1, dns.SHA256, dns.SHA384} {
fmt.Printf("%s; %d\n", key.ToDS(alg).String(), key.Flags)
}
}
}
}
// query is used to perform a lookup and stream results
func (c *client) query(params *QueryParam) error {
// Create the service name
serviceAddr := fmt.Sprintf("%s.%s.", trimDot(params.Service), trimDot(params.Domain))
// Start listening for response packets
msgCh := make(chan *dns.Msg, 32)
go c.recv(c.ipv4UnicastConn, msgCh)
go c.recv(c.ipv6UnicastConn, msgCh)
go c.recv(c.ipv4MulticastConn, msgCh)
go c.recv(c.ipv6MulticastConn, msgCh)
// Send the query
m := new(dns.Msg)
m.SetQuestion(serviceAddr, dns.TypePTR)
// RFC 6762, section 18.12. Repurposing of Top Bit of qclass in Question
// Section
//
// In the Question Section of a Multicast DNS query, the top bit of the qclass
// field is used to indicate that unicast responses are preferred for this
// particular question. (See Section 5.4.)
if params.WantUnicastResponse {
m.Question[0].Qclass |= 1 << 15
}
m.RecursionDesired = false
if err := c.sendQuery(m); err != nil {
return err
}
// Map the in-progress responses
inprogress := make(map[string]*ServiceEntry)
// Listen until we reach the timeout
finish := time.After(params.Timeout)
for {
select {
case resp := <-msgCh:
var inp *ServiceEntry
for _, answer := range append(resp.Answer, resp.Extra...) {
// TODO(reddaly): Check that response corresponds to serviceAddr?
switch rr := answer.(type) {
case *dns.PTR:
// Create new entry for this
inp = ensureName(inprogress, rr.Ptr)
case *dns.SRV:
// Check for a target mismatch
if rr.Target != rr.Hdr.Name {
alias(inprogress, rr.Hdr.Name, rr.Target)
}
// Get the port
inp = ensureName(inprogress, rr.Hdr.Name)
inp.Host = rr.Target
inp.Port = int(rr.Port)
case *dns.TXT:
// Pull out the txt
inp = ensureName(inprogress, rr.Hdr.Name)
inp.Info = strings.Join(rr.Txt, "|")
inp.hasTXT = true
case *dns.A:
// Pull out the IP
inp = ensureName(inprogress, rr.Hdr.Name)
inp.Addr = rr.A // @Deprecated
inp.AddrV4 = rr.A
case *dns.AAAA:
// Pull out the IP
inp = ensureName(inprogress, rr.Hdr.Name)
inp.Addr = rr.AAAA // @Deprecated
inp.AddrV6 = rr.AAAA
}
}
if inp == nil {
continue
}
// Check if this entry is complete
if inp.complete() {
if inp.sent {
continue
}
inp.sent = true
select {
case params.Entries <- inp:
default:
}
} else {
// Fire off a node specific query
m := new(dns.Msg)
m.SetQuestion(inp.Name, dns.TypePTR)
m.RecursionDesired = false
if err := c.sendQuery(m); err != nil {
log.Printf("[ERR] mdns: Failed to query instance %s: %v", inp.Name, err)
}
}
case <-finish:
return nil
}
}
}