135 lines
3.2 KiB
Go
135 lines
3.2 KiB
Go
package home
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import (
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"encoding/binary"
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"net/netip"
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"sync/atomic"
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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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)
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// RDNS resolves clients' addresses to enrich their metadata.
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type RDNS struct {
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exchanger dnsforward.RDNSExchanger
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clients *clientsContainer
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// usePrivate is used to store the state of current private RDNS resolving
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// settings and to react to it's changes.
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usePrivate uint32
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// ipCh used to pass client's IP to rDNS workerLoop.
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ipCh chan netip.Addr
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// ipCache caches the IP addresses to be resolved by rDNS. The resolved
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// address stays here while it's inside clients. After leaving clients the
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// address will be resolved once again. If the address couldn't be
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// resolved, cache prevents further attempts to resolve it for some time.
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ipCache cache.Cache
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}
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// Default rDNS values.
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const (
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defaultRDNSCacheSize = 10000
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defaultRDNSCacheTTL = 1 * 60 * 60
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defaultRDNSIPChSize = 256
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)
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// NewRDNS creates and returns initialized RDNS.
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func NewRDNS(
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exchanger dnsforward.RDNSExchanger,
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clients *clientsContainer,
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usePrivate bool,
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) (rDNS *RDNS) {
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rDNS = &RDNS{
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exchanger: exchanger,
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clients: clients,
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ipCache: cache.New(cache.Config{
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EnableLRU: true,
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MaxCount: defaultRDNSCacheSize,
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}),
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ipCh: make(chan netip.Addr, defaultRDNSIPChSize),
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}
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if usePrivate {
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rDNS.usePrivate = 1
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}
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go rDNS.workerLoop()
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return rDNS
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}
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// ensurePrivateCache ensures that the state of the RDNS cache is consistent
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// with the current private client RDNS resolving settings.
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//
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// TODO(e.burkov): Clearing cache each time this value changed is not a perfect
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// approach since only unresolved locally-served addresses should be removed.
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// Implement when improving the cache.
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func (r *RDNS) ensurePrivateCache() {
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var usePrivate uint32
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if r.exchanger.ResolvesPrivatePTR() {
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usePrivate = 1
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}
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if atomic.CompareAndSwapUint32(&r.usePrivate, 1-usePrivate, usePrivate) {
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r.ipCache.Clear()
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}
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}
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// isCached returns true if ip is already cached and not expired yet. It also
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// caches it otherwise.
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func (r *RDNS) isCached(ip netip.Addr) (ok bool) {
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ipBytes := ip.AsSlice()
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now := uint64(time.Now().Unix())
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if expire := r.ipCache.Get(ipBytes); len(expire) != 0 {
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if binary.BigEndian.Uint64(expire) > now {
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return true
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}
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}
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// The cache entry either expired or doesn't exist.
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ttl := make([]byte, 8)
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binary.BigEndian.PutUint64(ttl, now+defaultRDNSCacheTTL)
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r.ipCache.Set(ipBytes, ttl)
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return false
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}
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// Begin adds the ip to the resolving queue if it is not cached or already
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// resolved.
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func (r *RDNS) Begin(ip netip.Addr) {
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r.ensurePrivateCache()
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if r.isCached(ip) || r.clients.exists(ip, ClientSourceRDNS) {
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return
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}
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select {
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case r.ipCh <- ip:
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log.Debug("rdns: %q added to queue", ip)
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default:
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log.Debug("rdns: queue is full")
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}
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}
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// workerLoop handles incoming IP addresses from ipChan and adds it into
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// clients.
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func (r *RDNS) workerLoop() {
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defer log.OnPanic("rdns")
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for ip := range r.ipCh {
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host, err := r.exchanger.Exchange(ip.AsSlice())
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if err != nil {
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log.Debug("rdns: resolving %q: %s", ip, err)
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continue
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} else if host == "" {
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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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