package home import ( "encoding/binary" "net" "time" "github.com/AdguardTeam/AdGuardHome/internal/agherr" "github.com/AdguardTeam/AdGuardHome/internal/dnsforward" "github.com/AdguardTeam/golibs/cache" "github.com/AdguardTeam/golibs/log" ) // RDNS resolves clients' addresses to enrich their metadata. type RDNS struct { exchanger dnsforward.RDNSExchanger clients *clientsContainer // ipCh used to pass client's IP to rDNS workerLoop. ipCh chan net.IP // ipCache caches the IP addresses to be resolved by rDNS. The resolved // address stays here while it's inside clients. After leaving clients // the address will be resolved once again. If the address couldn't be // resolved, cache prevents further attempts to resolve it for some // time. ipCache cache.Cache } // Default rDNS values. const ( defaultRDNSCacheSize = 10000 defaultRDNSCacheTTL = 1 * 60 * 60 defaultRDNSIPChSize = 256 ) // NewRDNS creates and returns initialized RDNS. func NewRDNS( exchanger dnsforward.RDNSExchanger, clients *clientsContainer, ) (rDNS *RDNS) { rDNS = &RDNS{ exchanger: exchanger, clients: clients, ipCache: cache.New(cache.Config{ EnableLRU: true, MaxCount: defaultRDNSCacheSize, }), ipCh: make(chan net.IP, defaultRDNSIPChSize), } go rDNS.workerLoop() return rDNS } // Begin adds the ip to the resolving queue if it is not cached or already // resolved. func (r *RDNS) Begin(ip net.IP) { now := uint64(time.Now().Unix()) if expire := r.ipCache.Get(ip); len(expire) != 0 { if binary.BigEndian.Uint64(expire) > now { return } } // The cache entry either expired or doesn't exist. ttl := make([]byte, 8) binary.BigEndian.PutUint64(ttl, now+defaultRDNSCacheTTL) r.ipCache.Set(ip, ttl) id := ip.String() if r.clients.Exists(id, ClientSourceRDNS) { return } select { case r.ipCh <- ip: log.Tracef("rdns: %q added to queue", ip) default: log.Tracef("rdns: queue is full") } } // workerLoop handles incoming IP addresses from ipChan and adds it into // clients. func (r *RDNS) workerLoop() { defer agherr.LogPanic("rdns") for ip := range r.ipCh { host, err := r.exchanger.Exchange(ip) if err != nil { log.Debug("rdns: resolving %q: %s", ip, err) continue } if host == "" { continue } // Don't handle any errors since AddHost doesn't return non-nil // errors for now. _, _ = r.clients.AddHost(ip.String(), host, ClientSourceRDNS) } }