// Performs the actual query by service name (browse) or service instance name (lookup),
// start response listeners goroutines and loops over the entries channel.
func (c *client) query(params *LookupParams) error {
var serviceName, serviceInstanceName string
serviceName = fmt.Sprintf("%s.%s.", trimDot(params.Service), trimDot(params.Domain))
if params.Instance != "" {
serviceInstanceName = fmt.Sprintf("%s.%s", params.Instance, serviceName)
}
// send the query
m := new(dns.Msg)
if serviceInstanceName != "" {
m.Question = []dns.Question{
dns.Question{serviceInstanceName, dns.TypeSRV, dns.ClassINET},
dns.Question{serviceInstanceName, dns.TypeTXT, dns.ClassINET},
}
m.RecursionDesired = false
} else {
m.SetQuestion(serviceName, dns.TypePTR)
m.RecursionDesired = false
}
if err := c.sendQuery(m); err != nil {
return err
}
return nil
}
func main() {
if len(os.Args) <= 1 {
log.Printf("Usage: %s domain", os.Args[0])
os.Exit(1)
}
config, _ := dns.ClientConfigFromFile("/etc/resolv.conf")
c := new(dns.Client)
m := new(dns.Msg)
m.SetQuestion(dns.Fqdn(os.Args[1]), dns.TypeMX)
m.RecursionDesired = true
r, _, err := c.Exchange(m, net.JoinHostPort(config.Servers[0], config.Port))
if r == nil {
log.Fatalf("*** error: %s\n", err.Error())
}
if r.Rcode != dns.RcodeSuccess {
log.Fatalf(" *** invalid answer name %s after MX query for %s\n", os.Args[1], os.Args[1])
}
// Stuff must be in the answer section
for _, a := range r.Answer {
fmt.Printf("%v\n", a)
}
}
// perform a DNS query and assert the reply code, number or answers, etc
func assertExchange(t *testing.T, z string, ty uint16, minAnswers int, maxAnswers int, expErr int) *dns.Msg {
c := new(dns.Client)
c.UDPSize = testUDPBufSize
m := new(dns.Msg)
m.RecursionDesired = true
m.SetQuestion(z, ty)
m.SetEdns0(testUDPBufSize, false) // we don't want to play with truncation here...
r, _, err := c.Exchange(m, fmt.Sprintf("127.0.0.1:%d", testPort))
t.Logf("Response:\n%+v\n", r)
wt.AssertNoErr(t, err)
if minAnswers == 0 && maxAnswers == 0 {
wt.AssertStatus(t, r.Rcode, expErr, "DNS response code")
} else {
wt.AssertStatus(t, r.Rcode, dns.RcodeSuccess, "DNS response code")
}
answers := len(r.Answer)
if minAnswers >= 0 && answers < minAnswers {
wt.Fatalf(t, "Number of answers >= %d", minAnswers)
}
if maxAnswers >= 0 && answers > maxAnswers {
wt.Fatalf(t, "Number of answers <= %d", maxAnswers)
}
return r
}
func (self *DnsResolver) lookupHost(host string, triesLeft int) ([]net.IP, error) {
m1 := new(dns.Msg)
m1.Id = dns.Id()
m1.RecursionDesired = true
m1.Question = make([]dns.Question, 1)
m1.Question[0] = dns.Question{dns.Fqdn(host), dns.TypeA, dns.ClassINET}
in, err := dns.Exchange(m1, self.Servers[self.r.Intn(len(self.Servers))])
result := []net.IP{}
if err != nil {
if strings.HasSuffix(err.Error(), "i/o timeout") && triesLeft > 0 {
triesLeft -= 1
return self.lookupHost(host, triesLeft)
} else {
return result, err
}
}
if in != nil && in.Rcode != dns.RcodeSuccess {
return result, errors.New(dns.RcodeToString[in.Rcode])
}
for _, record := range in.Answer {
if t, ok := record.(*dns.A); ok {
result = append(result, t.A)
}
}
return result, err
}
func (c *Client) Discover(domain string, cb func(*dns.Msg)) {
m := new(dns.Msg)
m.SetQuestion(dns.Fqdn(domain), dns.TypePTR)
m.RecursionDesired = true
addr := &net.UDPAddr{
IP: net.ParseIP("224.0.0.251"),
Port: 5353,
}
conn, err := net.ListenMulticastUDP("udp4", nil, addr)
if err != nil {
panic(err)
}
defer conn.Close()
c.conn = conn
out, err := m.Pack()
if err != nil {
panic(err)
}
_, err = conn.WriteToUDP(out, addr)
if err != nil {
panic(err)
}
c.handleReceiveMsg(domain, cb)
}
// Perform a DNS query and assert the reply code, number or answers, etc
func assertExchange(t *testing.T, z string, ty uint16, port int, minAnswers int, maxAnswers int, expErr int) (*dns.Msg, *dns.Msg) {
require.NotEqual(t, 0, port, "invalid DNS server port")
c := &dns.Client{
UDPSize: testUDPBufSize,
}
m := new(dns.Msg)
m.RecursionDesired = true
m.SetQuestion(z, ty)
m.SetEdns0(testUDPBufSize, false) // we don't want to play with truncation here...
lstAddr := fmt.Sprintf("127.0.0.1:%d", port)
r, _, err := c.Exchange(m, lstAddr)
t.Logf("Response from '%s':\n%+v\n", lstAddr, r)
if err != nil {
t.Errorf("Error when querying DNS server at %s: %s", lstAddr, err)
}
require.NoError(t, err)
if minAnswers == 0 && maxAnswers == 0 {
require.Equal(t, expErr, r.Rcode, "DNS response code")
} else {
require.Equal(t, dns.RcodeSuccess, r.Rcode, "DNS response code")
}
answers := len(r.Answer)
if minAnswers >= 0 && answers < minAnswers {
require.FailNow(t, fmt.Sprintf("Number of answers >= %d", minAnswers))
}
if maxAnswers >= 0 && answers > maxAnswers {
require.FailNow(t, fmt.Sprintf("Number of answers <= %d", maxAnswers))
}
return m, r
}
// dnsQuery will query a nameserver, iterating through the supplied servers as it retries
// The nameserver should include a port, to facilitate testing where we talk to a mock dns server.
func dnsQuery(fqdn string, rtype uint16, nameservers []string, recursive bool) (in *dns.Msg, err error) {
m := new(dns.Msg)
m.SetQuestion(fqdn, rtype)
m.SetEdns0(4096, false)
if !recursive {
m.RecursionDesired = false
}
// Will retry the request based on the number of servers (n+1)
for i := 1; i <= len(nameservers)+1; i++ {
ns := nameservers[i%len(nameservers)]
udp := &dns.Client{Net: "udp", Timeout: DNSTimeout}
in, _, err = udp.Exchange(m, ns)
if err == dns.ErrTruncated {
tcp := &dns.Client{Net: "tcp", Timeout: DNSTimeout}
// If the TCP request suceeds, the err will reset to nil
in, _, err = tcp.Exchange(m, ns)
}
if err == nil {
break
}
}
return
}
// Async
func (c *MDNSClient) SendQuery(name string, querytype uint16, insistent bool, responseCh chan<- *Response) {
c.actionChan <- func() {
query, found := c.inflight[name]
if !found {
m := new(dns.Msg)
m.SetQuestion(name, querytype)
m.RecursionDesired = false
buf, err := m.Pack()
if err != nil {
responseCh <- &Response{err: err}
close(responseCh)
return
}
query = &inflightQuery{
name: name,
id: m.Id,
}
if _, err = c.conn.WriteTo(buf, c.addr); err != nil {
responseCh <- &Response{err: err}
close(responseCh)
return
}
c.inflight[name] = query
}
info := &responseInfo{
ch: responseCh,
timeout: time.Now().Add(mDNSTimeout),
insistent: insistent,
}
// Invariant on responseInfos: they are in ascending order of
// timeout. Since we use a fixed interval from Now(), this
// must be after all existing timeouts.
query.responseInfos = append(query.responseInfos, info)
}
}
func makeDnsTxtRequest(domain string, server string) (string, error) {
var err error
var conn *dns.Conn
if conn, err = dns.Dial("udp", server); err != nil {
return "", err
}
m := new(dns.Msg)
m.SetQuestion(dns.Fqdn(domain), dns.TypeTXT)
m.RecursionDesired = true
if err = conn.WriteMsg(m); err != nil {
return "", err
}
var rm *dns.Msg
if rm, err = conn.ReadMsg(); err != nil {
return "", err
}
if txt, ok := rm.Answer[0].(*dns.TXT); !ok {
return "", fmt.Errorf("No TXT Answer")
} else {
return strings.Join(txt.Txt, ""), nil
}
}
func createDKIMQuery(selector, domain string) *dns.Msg {
q := fmt.Sprintf("%s._domainkey.%s", selector, domain)
m := new(dns.Msg)
m.SetQuestion(dns.Fqdn(q), dns.TypeTXT)
m.RecursionDesired = true
return m
}
// Check that we can prune an answer
func TestPrune(t *testing.T) {
InitDefaultLogging(testing.Verbose())
Info.Println("TestPrune starting")
questionMsg := new(dns.Msg)
questionMsg.SetQuestion("name", dns.TypeA)
questionMsg.RecursionDesired = true
question := &questionMsg.Question[0]
records := []ZoneRecord{
Record{"name", net.ParseIP("10.0.1.1"), 0, 0, 0},
Record{"name", net.ParseIP("10.0.1.2"), 0, 0, 0},
Record{"name", net.ParseIP("10.0.1.3"), 0, 0, 0},
Record{"name", net.ParseIP("10.0.1.4"), 0, 0, 0},
}
reply := makeAddressReply(questionMsg, question, records, DefaultLocalTTL)
reply.Answer[0].Header().Ttl = DefaultLocalTTL
pruned := pruneAnswers(reply.Answer, 1)
require.Equal(t, 1, len(pruned), "wrong number of answers")
pruned = pruneAnswers(reply.Answer, 2)
require.Equal(t, 2, len(pruned), "wrong number of answers")
pruned = pruneAnswers(reply.Answer, 0)
require.Equal(t, len(records), len(pruned), "wrong number of answers")
}
func DnsQuery(query string, wg *sync.WaitGroup, config *dns.ClientConfig, cm *chanman.ChanMan) {
defer wg.Done()
dnsClient := new(dns.Client)
message := new(dns.Msg)
message.SetQuestion(dns.Fqdn(query), dns.TypeA)
message.RecursionDesired = true
response, rtt, err := dnsClient.Exchange(message, net.JoinHostPort(config.Servers[0], "53"))
if err != nil {
log.Println(err)
cm.RunChan <- true
}
if response == nil {
} else {
if response.Rcode != dns.RcodeSuccess {
log.Println(" query fail")
}
var stat = new(dnsstat.Info)
stat.Rtt = rtt
cm.StatsChan <- stat
cm.RunChan <- true
}
}
func newMsg(host string, qClass uint16) *dns.Msg {
m1 := new(dns.Msg)
m1.Id = dns.Id()
m1.RecursionDesired = true
m1.Question = make([]dns.Question, 1)
m1.Question[0] = dns.Question{host, qClass, dns.ClassINET}
return m1
}
func localQuery(mychan chan DNSreply, qname string, qtype uint16) {
var result DNSreply
var trials uint
result.qname = qname
result.qtype = qtype
result.r = nil
result.err = errors.New("No name server to answer the question")
localm := new(dns.Msg)
localm.Id = dns.Id()
localm.RecursionDesired = true
localm.Question = make([]dns.Question, 1)
localm.SetEdns0(EDNSBUFFERSIZE, false) // Even if no EDNS requested, see #9 May be we should retry without it if timeout?
localc := new(dns.Client)
localc.ReadTimeout = timeout
localm.Question[0] = dns.Question{qname, qtype, dns.ClassINET}
Tests:
for trials = 0; trials < uint(*maxTrials); trials++ {
Resolvers:
for serverIndex := range conf.Servers {
server := conf.Servers[serverIndex]
result.nameserver = server
// Brackets around the server address are necessary for IPv6 name servers
r, rtt, err := localc.Exchange(localm, "["+server+"]:"+conf.Port) // Do not use net.JoinHostPort, see https://github.com/bortzmeyer/check-soa/commit/3e4edb13855d8c4016768796b2892aa83eda1933#commitcomment-2355543
if r == nil {
result.r = nil
result.err = err
if strings.Contains(err.Error(), "timeout") {
// Try another resolver
break Resolvers
} else { // We give in
break Tests
}
} else {
result.rtt = rtt
if r.Rcode == dns.RcodeSuccess {
// TODO: as a result, NODATA (NOERROR/ANSWER=0) are silently ignored (try "foo", for instance, the name exists but no IP address)
// TODO: for rcodes like SERVFAIL, trying another resolver could make sense
result.r = r
result.err = nil
break Tests
} else {
// All the other codes are errors. Yes, it may
// happens that one resolver returns REFUSED
// and the others work but we do not handle
// this case. TODO: delete the resolver from
// the list and try another one
result.r = r
result.err = errors.New(dns.RcodeToString[r.Rcode])
break Tests
}
}
}
}
if *debug {
fmt.Printf("DEBUG: end of DNS request \"%s\" / %d\n", qname, qtype)
}
mychan <- result
}
// Perform probing & announcement
//TODO: implement a proper probing & conflict resolution
func (s *Server) probe() {
q := new(dns.Msg)
q.SetQuestion(s.service.ServiceInstanceName(), dns.TypePTR)
q.RecursionDesired = false
srv := &dns.SRV{
Hdr: dns.RR_Header{
Name: s.service.ServiceInstanceName(),
Rrtype: dns.TypeSRV,
Class: dns.ClassINET,
Ttl: s.ttl,
},
Priority: 0,
Weight: 0,
Port: uint16(s.service.Port),
Target: s.service.HostName,
}
txt := &dns.TXT{
Hdr: dns.RR_Header{
Name: s.service.ServiceInstanceName(),
Rrtype: dns.TypeTXT,
Class: dns.ClassINET,
Ttl: s.ttl,
},
Txt: s.service.Text,
}
q.Ns = []dns.RR{srv, txt}
randomizer := rand.New(rand.NewSource(time.Now().UnixNano()))
for i := 0; i < 3; i++ {
if err := s.multicastResponse(q); err != nil {
log.Println("[ERR] bonjour: failed to send probe:", err.Error())
}
time.Sleep(time.Duration(randomizer.Intn(250)) * time.Millisecond)
}
resp := new(dns.Msg)
resp.MsgHdr.Response = true
resp.Answer = []dns.RR{}
resp.Extra = []dns.RR{}
s.composeLookupAnswers(resp, s.ttl)
// From RFC6762
// The Multicast DNS responder MUST send at least two unsolicited
// responses, one second apart. To provide increased robustness against
// packet loss, a responder MAY send up to eight unsolicited responses,
// provided that the interval between unsolicited responses increases by
// at least a factor of two with every response sent.
timeout := 1 * time.Second
for i := 0; i < 3; i++ {
if err := s.multicastResponse(resp); err != nil {
log.Println("[ERR] bonjour: failed to send announcement:", err.Error())
}
time.Sleep(timeout)
timeout *= 2
}
}
// DNS requests go to this function
func dnsHandle(w dns.ResponseWriter, r *dns.Msg) {
name := r.Question[0].Name
if !namePattern.MatchString(name) {
kilog.Debug("%v does not match pattern, forwarding", name)
dnsForward(w, r)
return
}
// otherwise
kilog.Debug("%v matches pattern, handling", name)
dnsLock.Lock()
defer dnsLock.Unlock()
// check in table first
fakeIP, ok := nameToIP[name]
if !ok {
// place in table
var nwIP string
for {
haha := ipAlloc().String()
_, exists := ipToName[haha]
if exists {
continue
}
nwIP = haha
break
}
fakeIP = nwIP
nameToIP[name] = fakeIP
ipToName[fakeIP] = name
// remove in 30 minutes
go func() {
time.Sleep(time.Minute * 30)
dnsLock.Lock()
defer dnsLock.Unlock()
delete(nameToIP, name)
delete(ipToName, fakeIP)
}()
}
// return the fake IP to the user
resp := new(dns.A)
resp.Hdr.Name = name
resp.Hdr.Ttl = 1 // very short
resp.Hdr.Class = dns.ClassINET
resp.Hdr.Rrtype = dns.TypeA
resp.A = net.ParseIP(fakeIP)
towrite := new(dns.Msg)
towrite.Id = r.Id
towrite.RecursionAvailable = true
towrite.RecursionDesired = true
towrite.Response = true
towrite.Question = r.Question
towrite.Answer = make([]dns.RR, 1)
towrite.Answer[0] = resp
w.WriteMsg(towrite)
kilog.Debug("returning mapping %v -> %v", name, fakeIP)
}
func (d PodCheckAuth) authenticateToRegistry(token string, r types.DiagnosticResult) {
resolvConf, err := getResolvConf(r)
if err != nil {
return // any errors have been reported via "r", env is very borked, test cannot proceed
}
msg := new(dns.Msg)
msg.SetQuestion(registryHostname+".", dns.TypeA)
msg.RecursionDesired = false
result, completed := dnsQueryWithTimeout(msg, resolvConf.Servers[0], 2)
switch {
case !completed:
r.Error("DP1006", nil, fmt.Sprintf("DNS resolution for registry address %s timed out; this could indicate problems with DNS resolution or networking", registryHostname))
return
case result.err != nil:
r.Error("DP1016", nil, fmt.Sprintf("DNS resolution for registry address %s returned an error; container DNS is likely incorrect. The error was: %v", registryHostname, result.err))
return
case result.in == nil, len(result.in.Answer) == 0:
r.Warn("DP1007", nil, fmt.Sprintf("DNS resolution for registry address %s returned no results; either the integrated registry is not deployed, or container DNS configuration is incorrect.", registryHostname))
return
}
// first try the secure connection in case they followed directions to secure the registry
// (https://docs.openshift.org/latest/install_config/install/docker_registry.html#securing-the-registry)
cacert, err := ioutil.ReadFile(d.MasterCaPath) // TODO: we assume same CA as master - better choice?
if err != nil {
r.Error("DP1008", err, fmt.Sprintf("Failed to read CA cert file %s:\n%v", d.MasterCaPath, err))
return
}
pool := x509.NewCertPool()
if !pool.AppendCertsFromPEM(cacert) {
r.Error("DP1009", err, fmt.Sprintf("Could not use cert from CA cert file %s:\n%v", d.MasterCaPath, err))
return
}
noSecClient := http.Client{
CheckRedirect: func(req *http.Request, via []*http.Request) error {
return fmt.Errorf("no redirect expected")
},
Timeout: time.Second * 2,
}
secClient := noSecClient
secClient.Transport = knet.SetTransportDefaults(&http.Transport{TLSClientConfig: &tls.Config{RootCAs: pool}})
secError := processRegistryRequest(&secClient, fmt.Sprintf("https://%s:%s/v2/", registryHostname, registryPort), token, r)
if secError == nil {
return // made the request successfully enough to diagnose
}
switch {
case strings.Contains(secError.Error(), "tls: oversized record received"),
strings.Contains(secError.Error(), "server gave HTTP response to HTTPS"):
r.Debug("DP1015", "docker-registry not secured; falling back to cleartext connection")
if nosecError := processRegistryRequest(&noSecClient, fmt.Sprintf("http://%s:%s/v2/", registryHostname, registryPort), token, r); nosecError != nil {
r.Error("DP1013", nosecError, fmt.Sprintf("Unexpected error authenticating to the integrated registry:\n(%T) %[1]v", nosecError))
}
default:
r.Error("DP1013", secError, fmt.Sprintf("Unexpected error authenticating to the integrated registry:\n(%T) %[1]v", secError))
}
}
/*
* makeMessage() - construct DNS message structure
*/
func makeMessage(c *Context, qname, qtype, qclass string, ext Extension) *dns.Msg {
m := new(dns.Msg)
m.Id = dns.Id()
if c.restype == RESOLUTION_STUB {
m.RecursionDesired = true
} else {
m.RecursionDesired = false
}
if c.adflag {
m.AuthenticatedData = true
}
if c.cdflag {
m.CheckingDisabled = true
}
if ext["dnssec_return_status"] || ext["dnssec_return_only_secure"] || ext["dnssec_return_validation_chain"] {
opt := new(dns.OPT)
opt.Hdr.Name = "."
opt.Hdr.Rrtype = dns.TypeOPT
opt.SetDo()
m.Extra = append(m.Extra, opt)
}
m.Question = make([]dns.Question, 1)
qtype_int, ok := dns.StringToType[strings.ToUpper(qtype)]
if !ok {
fmt.Printf("%s: Unrecognized query type.\n", qtype)
return nil
}
qclass_int, ok := dns.StringToClass[strings.ToUpper(qclass)]
if !ok {
fmt.Printf("%s: Unrecognized query class.\n", qclass)
return nil
}
m.Question[0] = dns.Question{qname, qtype_int, qclass_int}
return m
}
func (d *DnsDomain) Test() bool {
if !(*Domain)(d).Test() {
return false
}
fqdn := d.Name
if strings.HasPrefix(fqdn, "*.") {
fqdn = "a" + fqdn[1:]
}
if !strings.HasSuffix(fqdn, ".") {
fqdn = fqdn + "."
}
any_ok := false
d.DNS = make([]*DnsRecords, 0, len(DNS_servers))
for name, addr := range DNS_servers {
records := new(DnsRecords)
records.Server = name
records.NS = addr
d.DNS = append(d.DNS, records)
req := new(dns.Msg)
req.Id = dns.Id()
req.RecursionDesired = true
req.Question = []dns.Question{
dns.Question{fqdn, dns.TypeA, dns.ClassINET},
}
resp, err := dns_client.Exchange(req, addr)
if err != nil {
records.Status = 900
records.Message = err.Error()
continue
}
records.IPs = make([]string, 0, len(resp.Answer))
for _, rr := range resp.Answer {
switch a := rr.(type) {
case *dns.RR_A:
records.IPs = append(records.IPs, a.A.String())
}
}
if len(records.IPs) > 0 {
any_ok = true
} else {
records.Status = 900
records.Message = "No records"
}
}
return any_ok
}
func DnsGetDoaminIP(domain string) (string, error) {
m := new(dns.Msg)
m.Id = dns.Id()
m.SetQuestion(dns.Fqdn(domain), dns.TypeA)
m.RecursionDesired = true
res, err := dnsQuery(m)
if nil != err {
return "", err
}
return pickIP(res), nil
}
func pinguer(domain string) (int, int) {
// Every N steps, we will tell the stats module how many requests we sent
maxRequestID := big.NewInt(65536)
errors := 0
totalSent := 0
questionRecord := dns.TypeA
message := new(dns.Msg).SetQuestion(domain, questionRecord)
if iterative {
message.RecursionDesired = false
}
for reqnumber := 0; count == 0 || reqnumber < count; reqnumber++ {
// Try to resolve the domain
if randomIds {
// Regenerate message Id to avoid servers dropping (seemingly) duplicate messages
newid, _ := rand.Int(rand.Reader, maxRequestID)
message.Id = uint16(newid.Int64())
}
start := time.Now()
err := dnsExchange(resolver, message)
elapsedMilliSeconds := float64(time.Since(start)) / float64(time.Millisecond)
if err != nil {
if verbose {
fmt.Printf("%s error: % (%s)\n", domain, err, resolver)
}
errors++
}
totalSent++
// Display results of the ping
fmt.Printf(
"ping %s with %s %s: %.3fms\n",
resolver,
dns.TypeToString[questionRecord],
domain,
elapsedMilliSeconds,
)
time.Sleep(time.Duration(pingInterval) * time.Millisecond)
}
return totalSent, errors
}
// Returns true if domain has a Name Server associated
func queryNS(domain string, dnsServers []string, proto string) (int, error) {
c := new(dns.Client)
c.ReadTimeout = time.Duration(2 * time.Second)
c.WriteTimeout = time.Duration(2 * time.Second)
c.Net = proto
m := new(dns.Msg)
m.RecursionDesired = true
dnsServer := dnsServers[rand.Intn(len(dnsServers))]
m.SetQuestion(dns.Fqdn(domain), dns.TypeNS)
in, _, err := c.Exchange(m, dnsServer+":53")
if err == nil {
return in.Rcode, err
}
return dns.RcodeRefused, err
}
func (resolver ConsulDnsAddressResolver) Resolve(service string) (string, error) {
m1 := new(dns.Msg)
m1.Id = dns.Id()
m1.RecursionDesired = true
m1.SetQuestion(service+".service.consul.", dns.TypeA)
c := new(dns.Client)
in, _, err := c.Exchange(m1, resolver.ServerAddress)
if err != nil {
log.Fatal(err)
}
if len(in.Answer) > 0 {
log.Println(in.Answer)
return in.Answer[0].(*dns.A).A.String(), nil
}
return "", errors.New("Could not resolve service address")
}
// ExampleRetrieverFunc uses a specific resolver with custom timeouts.
func ExampleRetrieverFunc() {
discovery := dnsdisco.NewDiscovery("jabber", "tcp", "registro.br")
discovery.SetRetriever(dnsdisco.RetrieverFunc(func(service, proto, name string) (servers []*net.SRV, err error) {
client := dns.Client{
ReadTimeout: 2 * time.Second,
WriteTimeout: 2 * time.Second,
}
name = strings.TrimRight(name, ".")
z := fmt.Sprintf("_%s._%s.%s.", service, proto, name)
var request dns.Msg
request.SetQuestion(z, dns.TypeSRV)
request.RecursionDesired = true
response, _, err := client.Exchange(&request, "8.8.8.8:53")
if err != nil {
return nil, err
}
for _, rr := range response.Answer {
if srv, ok := rr.(*dns.SRV); ok {
servers = append(servers, &net.SRV{
Target: srv.Target,
Port: srv.Port,
Priority: srv.Priority,
Weight: srv.Weight,
})
}
}
return
}))
// Retrieve the servers
if err := discovery.Refresh(); err != nil {
fmt.Println(err)
return
}
target, port := discovery.Choose()
fmt.Printf("Target: %s\nPort: %d\n", target, port)
// Output:
// Target: jabber.registro.br.
// Port: 5269
}
func findSoaNs(domain string) (string, string, string) {
var cname string
var soa string
var ns string
add := func(c, s, n string) {
cname += c
soa += s
ns += n
return
}
cname += domain + ","
m1 := new(dns.Msg)
m1.Id = dns.Id()
m1.RecursionDesired = true
m1.Question = make([]dns.Question, 1)
m1.Question[0] = dns.Question{domain, dns.TypeSOA, dns.ClassINET}
in, _ := dns.Exchange(m1, (cf.Servers[1] + ":53"))
rrList := [...][]dns.RR{in.Answer, in.Ns, in.Extra}
for _, rr := range rrList {
for i := len(rr) - 1; i >= 0; i-- {
switch rr[i].Header().Rrtype {
case dns.TypeCNAME:
temp_cname := rr[i].(*dns.CNAME)
add(findSoaNs(temp_cname.Target))
// fmt.Println( "temp_cname:" , temp_cname )
return cname, soa, ns
break
case dns.TypeNS:
temp_ns := rr[i].(*dns.NS)
ns += temp_ns.Ns + "," // + "|" + fmt.Sprint( temp_ns.Hdr.Ttl ) + ","
// fmt.Println( "temp_ns:" , temp_ns )
break
case dns.TypeSOA:
temp_soa := rr[i].(*dns.SOA)
soa += temp_soa.Ns + "," // + "|" + fmt.Sprint( temp_soa.Hdr.Ttl ) + ","
// fmt.Println( "temp_soa:" , temp_soa )
break
}
}
}
return cname, soa, ns
}
// dnsQuery sends a DNS query to the given nameserver.
// The nameserver should include a port, to facilitate testing where we talk to a mock dns server.
func dnsQuery(fqdn string, rtype uint16, nameserver string, recursive bool) (in *dns.Msg, err error) {
m := new(dns.Msg)
m.SetQuestion(fqdn, rtype)
m.SetEdns0(4096, false)
if !recursive {
m.RecursionDesired = false
}
in, err = dns.Exchange(m, nameserver)
if err == dns.ErrTruncated {
tcp := &dns.Client{Net: "tcp"}
in, _, err = tcp.Exchange(m, nameserver)
}
return
}
func (this *UDPNameServer) BuildQueryA(domain string, id uint16) *alloc.Buffer {
buffer := alloc.NewBuffer()
msg := new(dns.Msg)
msg.Id = id
msg.RecursionDesired = true
msg.Question = []dns.Question{
dns.Question{
Name: dns.Fqdn(domain),
Qtype: dns.TypeA,
Qclass: dns.ClassINET,
}}
writtenBuffer, _ := msg.PackBuffer(buffer.Value)
buffer.Slice(0, len(writtenBuffer))
return buffer
}
func fakeMsg(dom string, rrHeader uint16, proto string, serverPort int) (*dns.Msg, error) {
qc := uint16(dns.ClassINET)
c := new(dns.Client)
c.Net = proto
m := new(dns.Msg)
m.Question = make([]dns.Question, 1)
m.Question[0] = dns.Question{
Name: dns.Fqdn(dom),
Qtype: rrHeader,
Qclass: qc,
}
m.RecursionDesired = true
in, _, err := c.Exchange(m, "127.0.0.1:"+strconv.Itoa(serverPort))
return in, err
}
// Lookup the IP address using HypeDNS
func lookupHypeDNS(hostname string) (response string, err error) {
c := new(dns.Client)
m := new(dns.Msg)
m.SetQuestion(dns.Fqdn(hostname), dns.TypeAAAA)
m.RecursionDesired = true
r, _, err := c.Exchange(m, "[fc5d:baa5:61fc:6ffd:9554:67f0:e290:7535]:53")
if r == nil || err != nil {
return
}
// Stuff must be in the answer section
for _, a := range r.Answer {
columns := strings.Fields(a.String()) //column 4 holds the ip address
return padIPv6(net.ParseIP(columns[4])), nil
}
return
}
func linearResolver(threadID int, domain string, sentCounterCh chan<- result) {
// Resolve the domain as fast as possible
if verbose {
fmt.Printf("Starting thread #%d.\n", threadID)
}
// Every N steps, we will tell the stats module how many requests we sent
displayStep := 5
maxRequestID := big.NewInt(65536)
errors := 0
message := new(dns.Msg).SetQuestion(domain, dns.TypeA)
if iterative {
message.RecursionDesired = false
}
for {
for i := 0; i < displayStep; i++ {
// Try to resolve the domain
if randomIds {
// Regenerate message Id to avoid servers dropping (seemingly) duplicate messages
newid, _ := rand.Int(rand.Reader, maxRequestID)
message.Id = uint16(newid.Int64())
}
if flood {
go dnsExchange(resolver, message)
} else {
err := dnsExchange(resolver, message)
if err != nil {
if verbose {
fmt.Printf("%s error: % (%s)\n", domain, err, resolver)
}
errors++
}
}
}
// Update the counter of sent requests and requests
sentCounterCh <- result{displayStep, errors}
errors = 0
}
}