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dnsserver.go
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dnsserver.go
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package dns
import (
"fmt"
"github.com/alibaba/kt-connect/pkg/common"
opt "github.com/alibaba/kt-connect/pkg/kt/command/options"
"github.com/alibaba/kt-connect/pkg/kt/service/cluster"
"github.com/alibaba/kt-connect/pkg/kt/util"
"github.com/miekg/dns"
"github.com/rs/zerolog/log"
"net"
"regexp"
"strconv"
"strings"
"time"
)
type DnsServer struct {
dnsAddresses []string
extraDomains map[string]string
}
func SetupLocalDns(remoteDnsPort, localDnsPort int, dnsOrder []string) error {
var res = make(chan error)
go func() {
upstreamDnsAddresses := getDnsAddresses(dnsOrder, GetNameServer(), remoteDnsPort)
// domain-name -> ip
extraDomains := getIngressDomains()
log.Info().Msgf("Setup local DNS with upstream %v", upstreamDnsAddresses)
HandleExtraDomainMapping(extraDomains, localDnsPort)
res <-common.SetupDnsServer(&DnsServer{upstreamDnsAddresses, extraDomains}, localDnsPort, "udp")
}()
select {
case err := <-res:
return err
case <-time.After(1 * time.Second):
return nil
}
}
func getIngressDomains() map[string]string {
if opt.Get().Connect.IngressIp == "" {
return map[string]string{}
}
if !util.IsValidIp(opt.Get().Connect.IngressIp) {
log.Warn().Msgf("Ingress Ip '" + opt.Get().Connect.IngressIp + "' is invalid")
return map[string]string{}
}
ingressDomains := make(map[string]string)
if ingresses, err := cluster.Ins().GetAllIngressInNamespace(opt.Get().Global.Namespace); err != nil {
log.Warn().Err(err).Msgf("Failed to found ingress instances")
} else {
for _, ingress := range ingresses.Items {
for _, rule := range ingress.Spec.Rules {
if rule.Host != "" {
log.Debug().Msgf("Find ingress domain " + rule.Host)
ingressDomains[rule.Host] = opt.Get().Connect.IngressIp
}
}
}
}
return ingressDomains
}
func getDnsAddresses(dnsOrder []string, upstreamDns string, clusterDnsPort int) []string {
upstreamPattern := fmt.Sprintf("^([cdptu]{3}:)?%s(:[0-9]+)?$", util.DnsOrderUpstream)
var dnsAddresses []string
for _, dnsAddr := range dnsOrder {
if dnsAddr == util.DnsOrderCluster {
dnsAddresses = append(dnsAddresses, fmt.Sprintf("tcp:%s:%d", common.Localhost, clusterDnsPort))
} else if ok, err := regexp.MatchString(upstreamPattern, dnsAddr); err == nil && ok {
upstreamParts := strings.Split(dnsAddr, ":")
if upstreamDns != "" {
switch strings.Count(dnsAddr, ":") {
case 0:
dnsAddresses = append(dnsAddresses, fmt.Sprintf("udp:%s:%d", upstreamDns, common.StandardDnsPort))
case 1:
if _, err = strconv.Atoi(upstreamParts[1]); err == nil {
dnsAddresses = append(dnsAddresses, fmt.Sprintf("udp:%s:%s", upstreamDns, upstreamParts[1]))
} else {
dnsAddresses = append(dnsAddresses, fmt.Sprintf("%s:%s:%d", upstreamParts[0], upstreamDns, common.StandardDnsPort))
}
case 2:
dnsAddresses = append(dnsAddresses, fmt.Sprintf("%s:%s:%s", upstreamParts[0], upstreamDns, upstreamParts[2]))
default:
log.Warn().Msgf("Skip invalid upstream dns server %s", dnsAddr)
}
}
} else {
switch strings.Count(dnsAddr, ":") {
case 0:
dnsAddresses = append(dnsAddresses, fmt.Sprintf("udp:%s:%d", dnsAddr, common.StandardDnsPort))
case 1:
if _, err = strconv.Atoi(strings.Split(dnsAddr, ":")[1]); err == nil {
dnsAddresses = append(dnsAddresses, fmt.Sprintf("udp:%s", dnsAddr))
} else {
dnsAddresses = append(dnsAddresses, fmt.Sprintf("%s:%d", dnsAddr, common.StandardDnsPort))
}
case 2:
dnsAddresses = append(dnsAddresses, dnsAddr)
default:
log.Warn().Msgf("Skip invalid dns server %s", dnsAddr)
}
}
}
return dnsAddresses
}
// ServeDNS query DNS record
func (s *DnsServer) ServeDNS(w dns.ResponseWriter, req *dns.Msg) {
msg := (&dns.Msg{}).SetReply(req)
msg.Authoritative = true
msg.Answer = query(req, s.dnsAddresses, s.extraDomains)
if err := w.WriteMsg(msg); err != nil {
log.Warn().Err(err).Msgf("Failed to reply dns request")
}
}
func query(req *dns.Msg, dnsAddresses []string, extraDomains map[string]string) []dns.RR {
domain := req.Question[0].Name
qtype := req.Question[0].Qtype
answer := common.ReadCache(domain, qtype, int64(opt.Get().Connect.DnsCacheTtl))
if answer != nil {
log.Debug().Msgf("Found domain %s (%d) in cache", domain, qtype)
return answer
}
for host, ip := range extraDomains {
if wildcardMatch(host, domain) {
return []dns.RR{toARecord(domain, ip)}
}
}
for _, dnsAddr := range dnsAddresses {
dnsParts := strings.SplitN(dnsAddr, ":", 3)
protocol := dnsParts[0]
ip := dnsParts[1]
port, err := strconv.Atoi(dnsParts[2])
if ip == "" || err != nil || (protocol != "tcp" && protocol != "udp") {
// skip invalid dns address
continue
}
res, err := common.NsLookup(domain, qtype, protocol, fmt.Sprintf("%s:%d", ip, port))
if res != nil && len(res.Answer) > 0 {
// only record none-empty result of cluster dns
log.Debug().Msgf("Found domain %s (%d) in dns (%s:%d)", domain, qtype, ip, port)
common.WriteCache(domain, qtype, res.Answer, time.Now().Unix())
return res.Answer
} else if err != nil && !common.IsDomainNotExist(err) {
// usually io timeout error
log.Warn().Err(err).Msgf("Failed to lookup %s (%d) in dns (%s:%d)", domain, qtype, ip, port)
}
}
log.Debug().Msgf("Empty answer for domain lookup %s (%d)", domain, qtype)
common.WriteCache(domain, qtype, []dns.RR{}, time.Now().Unix()-int64(opt.Get().Connect.DnsCacheTtl)/2)
return []dns.RR{}
}
func wildcardMatch(pattenDomain, targetDomain string) bool {
if !strings.HasSuffix(pattenDomain, ".") {
pattenDomain = pattenDomain + "."
}
if strings.Contains(pattenDomain, "*") {
ok, err := regexp.MatchString("^" + strings.ReplaceAll(strings.ReplaceAll(pattenDomain, ".", "\\."), "*", ".*") + "$", targetDomain)
return ok && err == nil
} else {
return pattenDomain == targetDomain
}
}
func toARecord(domain, ip string) dns.RR {
return &dns.A {
Hdr: dns.RR_Header {
Name: domain,
Rrtype: dns.TypeA,
Class: dns.ClassINET,
Ttl: 5,
Rdlength: 4,
},
A: net.ParseIP(ip),
}
}