126 lines
2.6 KiB
Go
126 lines
2.6 KiB
Go
package home
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import (
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"fmt"
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"strings"
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"time"
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"github.com/AdguardTeam/dnsproxy/upstream"
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"github.com/AdguardTeam/golibs/log"
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"github.com/miekg/dns"
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)
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const (
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rdnsTimeout = 3 * time.Second // max time to wait for rDNS response
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)
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func initRDNS() {
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var err error
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bindhost := config.DNS.BindHost
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if config.DNS.BindHost == "0.0.0.0" {
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bindhost = "127.0.0.1"
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}
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resolverAddress := fmt.Sprintf("%s:%d", bindhost, config.DNS.Port)
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opts := upstream.Options{
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Timeout: rdnsTimeout,
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}
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config.dnsctx.upstream, err = upstream.AddressToUpstream(resolverAddress, opts)
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if err != nil {
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log.Error("upstream.AddressToUpstream: %s", err)
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return
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}
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config.dnsctx.rdnsIP = make(map[string]bool)
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config.dnsctx.rdnsChannel = make(chan string, 256)
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go asyncRDNSLoop()
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}
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// Add IP address to the rDNS queue
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func beginAsyncRDNS(ip string) {
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if config.clients.Exists(ip) {
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return
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}
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// add IP to rdnsIP, if not exists
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config.dnsctx.rdnsLock.Lock()
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defer config.dnsctx.rdnsLock.Unlock()
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_, ok := config.dnsctx.rdnsIP[ip]
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if ok {
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return
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}
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config.dnsctx.rdnsIP[ip] = true
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log.Tracef("Adding %s for rDNS resolve", ip)
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select {
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case config.dnsctx.rdnsChannel <- ip:
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//
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default:
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log.Tracef("rDNS queue is full")
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}
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}
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// Use rDNS to get hostname by IP address
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func resolveRDNS(ip string) string {
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log.Tracef("Resolving host for %s", ip)
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req := dns.Msg{}
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req.Id = dns.Id()
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req.RecursionDesired = true
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req.Question = []dns.Question{
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{
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Qtype: dns.TypePTR,
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Qclass: dns.ClassINET,
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},
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}
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var err error
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req.Question[0].Name, err = dns.ReverseAddr(ip)
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if err != nil {
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log.Debug("Error while calling dns.ReverseAddr(%s): %s", ip, err)
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return ""
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}
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resp, err := config.dnsctx.upstream.Exchange(&req)
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if err != nil {
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log.Debug("Error while making an rDNS lookup for %s: %s", ip, err)
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return ""
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}
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if len(resp.Answer) != 1 {
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log.Debug("No answer for rDNS lookup of %s", ip)
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return ""
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}
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ptr, ok := resp.Answer[0].(*dns.PTR)
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if !ok {
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log.Debug("not a PTR response for %s", ip)
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return ""
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}
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log.Tracef("PTR response for %s: %s", ip, ptr.String())
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if strings.HasSuffix(ptr.Ptr, ".") {
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ptr.Ptr = ptr.Ptr[:len(ptr.Ptr)-1]
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}
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return ptr.Ptr
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}
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// Wait for a signal and then synchronously resolve hostname by IP address
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// Add the hostname:IP pair to "Clients" array
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func asyncRDNSLoop() {
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for {
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var ip string
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ip = <-config.dnsctx.rdnsChannel
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host := resolveRDNS(ip)
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if len(host) == 0 {
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continue
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}
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config.dnsctx.rdnsLock.Lock()
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delete(config.dnsctx.rdnsIP, ip)
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config.dnsctx.rdnsLock.Unlock()
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_, _ = config.clients.AddHost(ip, host, ClientSourceRDNS)
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}
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}
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