129 lines
2.9 KiB
Go
129 lines
2.9 KiB
Go
package home
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import (
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"encoding/binary"
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"strings"
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"time"
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"github.com/AdguardTeam/AdGuardHome/internal/dnsforward"
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"github.com/AdguardTeam/golibs/cache"
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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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// RDNS - module context
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type RDNS struct {
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dnsServer *dnsforward.Server
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clients *clientsContainer
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ipChannel chan string // pass data from DNS request handling thread to rDNS thread
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// Contains IP addresses of clients to be resolved by rDNS
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// If IP address is resolved, it stays here while it's inside Clients.
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// If it's removed from Clients, this IP address will be resolved once again.
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// If IP address couldn't be resolved, it stays here for some time to prevent further attempts to resolve the same IP.
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ipAddrs cache.Cache
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}
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// InitRDNS - create module context
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func InitRDNS(dnsServer *dnsforward.Server, clients *clientsContainer) *RDNS {
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r := RDNS{}
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r.dnsServer = dnsServer
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r.clients = clients
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cconf := cache.Config{}
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cconf.EnableLRU = true
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cconf.MaxCount = 10000
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r.ipAddrs = cache.New(cconf)
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r.ipChannel = make(chan string, 256)
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go r.workerLoop()
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return &r
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}
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// Begin - add IP address to rDNS queue
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func (r *RDNS) Begin(ip string) {
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now := uint64(time.Now().Unix())
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expire := r.ipAddrs.Get([]byte(ip))
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if len(expire) != 0 {
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exp := binary.BigEndian.Uint64(expire)
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if exp > now {
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return
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}
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// TTL expired
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}
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expire = make([]byte, 8)
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const ttl = 1 * 60 * 60
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binary.BigEndian.PutUint64(expire, now+ttl)
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_ = r.ipAddrs.Set([]byte(ip), expire)
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if r.clients.Exists(ip, ClientSourceRDNS) {
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return
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}
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log.Tracef("rDNS: adding %s", ip)
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select {
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case r.ipChannel <- 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 (r *RDNS) resolve(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 := r.dnsServer.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) == 0 {
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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 (r *RDNS) workerLoop() {
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for {
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ip := <-r.ipChannel
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host := r.resolve(ip)
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if len(host) == 0 {
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continue
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}
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_, _ = r.clients.AddHost(ip, host, ClientSourceRDNS)
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}
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}
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