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dns.go
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dns.go
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package main
import (
"context"
"errors"
"net"
"strings"
"sync"
"sync/atomic"
"time"
"github.com/Sirupsen/logrus"
"github.com/miekg/dns"
)
var (
allowedDomainChars [255]bool
)
func init() {
for _, b := range []byte("1234567890qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM.-") {
allowedDomainChars[b] = true
}
}
func domainValidName(domain string) error {
if len(domain) == 0 {
return errors.New("Zero length domain name")
}
if domain[0] == '.' || domain[0] == '-' {
return errors.New("Bad start symbol")
}
if domain[len(domain)-1] == '-' {
return errors.New("Bad end symbol")
}
for _, latinChar := range []byte(domain) {
if !allowedDomainChars[latinChar] {
return errors.New("Bad symbol")
}
}
return nil
}
func domainHasLocalIP(ctx context.Context, domain string) (res bool) {
defer func() { logrus.Debugf("domainHasLocalIP for '%v': %v", domain, res) }()
var ipsChan = make(chan []net.IP, 1)
defer func() {
// clean channel for no leak blocked goroutines
for range ipsChan {
// pass
}
}()
var dnsRequests = &sync.WaitGroup{}
dnsRequests.Add(1)
go func() {
ips, err := net.LookupIP(domain)
if err == nil {
ipsChan <- ips
} else {
logrus.Infof("Can't local lookup ip for domain %v: %v", DomainPresent(domain), err)
}
logrus.Debugf("Receive answer from local lookup for domain %v ips: '%v'", DomainPresent(domain), ips)
dnsRequests.Done()
}()
domainForRequest := domain
if !strings.HasSuffix(domainForRequest, ".") {
domainForRequest += "."
}
dnsq := func(server string) {
const recordTypeForRequest = 2 // two request for every server: for A and AAAA record
var serverWg sync.WaitGroup
serverWg.Add(recordTypeForRequest)
var dnsServerIpsChan = make(chan []net.IP, recordTypeForRequest)
var dnsRequestErrorCount int32
go func() {
defer serverWg.Done()
ips, err := getIPsFromDNS(ctx, domainForRequest, server, dns.TypeA)
if err == nil {
dnsServerIpsChan <- ips
} else {
logrus.Debugf("Error with request to dns server '%v' (type A) for domain '%v': %v", server, domain, err)
atomic.AddInt32(&dnsRequestErrorCount, 1)
}
}()
go func() {
defer serverWg.Done()
ips, err := getIPsFromDNS(ctx, domainForRequest, server, dns.TypeAAAA)
if err == nil {
dnsServerIpsChan <- ips
} else {
logrus.Debugf("Error with request to dns server '%v' (type AAAA) for domain '%v': %v", server, domain, err)
atomic.AddInt32(&dnsRequestErrorCount, 1)
}
}()
go func() {
serverWg.Wait()
close(dnsServerIpsChan)
}()
var serverResult []net.IP
for serverIps := range dnsServerIpsChan {
serverResult = append(serverResult, serverIps...)
}
if dnsRequestErrorCount > 0 {
logrus.Infof("Dns server '%v' has errors while request process for domain '%v'. It is not send IP result for main IP comparer.", server, domain)
return
}
ipsChan <- serverResult
}
dnsServers := []string{
"8.8.8.8:53", // google 1
"[2001:4860:4860::8844]:53", // google 2 (ipv6)
"77.88.8.8:53", // yandex 1
"[2a02:6b8:0:1::feed:0ff]:53", // yandex 2 (ipv6)
}
dnsRequests.Add(len(dnsServers))
for _, dnsServer := range dnsServers {
go func(server string) {
dnsq(server)
dnsRequests.Done()
}(dnsServer)
}
go func() {
// close channel after all requests complete
dnsRequests.Wait()
close(ipsChan)
}()
hasIP := false
allowIPs := getAllowIPs()
for ips := range ipsChan {
if len(ips) > 0 {
hasIP = true
logrus.Debugf("Has IP for domain '%v' set: %v", domain, hasIP)
} else {
logrus.Infof("Some dns server doesn't know domain and no return IP addresses (see debug log for details) for domain: %v", domain)
return false
}
for _, ip := range ips {
// If domain has ip doesn't that doesn't bind to the server
if !ipContains(allowIPs, ip) {
logrus.Debugf("Domain have ip of other server. domain %v, Domain ips: '%v', Server ips: '%v'", DomainPresent(domain), ips, allowIPs)
return false
}
}
}
logrus.Debugf("HasIP after receive all dns answer for domain '%v': %v", domain, hasIP)
if !hasIP {
logrus.Infof("Doesn't found ip addresses for domain %v", DomainPresent(domain))
return false
}
return true
}
func getIPsFromDNS(ctx context.Context, domain, dnsServer string, recordType uint16) (ips []net.IP, err error) {
dnsClient := dns.Client{}
if deadline, hasDeadline := ctx.Deadline(); hasDeadline {
ctxTimeout := time.Until(deadline)
if *dnsTimeout < ctxTimeout {
ctxTimeout = *dnsTimeout
}
dnsClient.DialTimeout = ctxTimeout
dnsClient.ReadTimeout = ctxTimeout
dnsClient.WriteTimeout = ctxTimeout
}
msg := dns.Msg{}
msg.Id = dns.Id()
msg.SetQuestion(domain, recordType)
answer, _, err := dnsClient.Exchange(&msg, dnsServer)
if err != nil {
logrus.Infof("Error from dns server '%v' for domain %v, record type '%v': %v", dnsServer, DomainPresent(domain), dns.TypeToString[recordType], err)
return nil, err
}
if answer.Id != msg.Id {
logrus.Infof("Error answer ID from dns server '%v' for domain %v, record type '%v', %v != %v", dnsServer, DomainPresent(domain), dns.TypeToString[recordType], msg.Id, answer.Id)
return nil, errors.New("error answer ID from dns server")
}
var res []net.IP
for _, r := range answer.Answer {
if r.Header().Rrtype != recordType {
continue
}
switch r.Header().Rrtype {
case dns.TypeA:
res = append(res, r.(*dns.A).A)
case dns.TypeAAAA:
res = append(res, r.(*dns.AAAA).AAAA)
default:
continue
}
}
logrus.Debugf("Receive answer from dns server '%v' for domain %v record type '%v' ips: '%v'", dnsServer, DomainPresent(domain), dns.TypeToString[recordType], res)
return res, nil
}