// Package dnsforward contains a DNS forwarding server. package dnsforward import ( "context" "fmt" "io" "net" "net/http" "net/netip" "runtime" "slices" "strings" "sync" "sync/atomic" "time" "github.com/AdguardTeam/AdGuardHome/internal/aghalg" "github.com/AdguardTeam/AdGuardHome/internal/aghnet" "github.com/AdguardTeam/AdGuardHome/internal/client" "github.com/AdguardTeam/AdGuardHome/internal/filtering" "github.com/AdguardTeam/AdGuardHome/internal/querylog" "github.com/AdguardTeam/AdGuardHome/internal/rdns" "github.com/AdguardTeam/AdGuardHome/internal/stats" "github.com/AdguardTeam/dnsproxy/proxy" "github.com/AdguardTeam/dnsproxy/upstream" "github.com/AdguardTeam/golibs/cache" "github.com/AdguardTeam/golibs/errors" "github.com/AdguardTeam/golibs/log" "github.com/AdguardTeam/golibs/netutil" "github.com/AdguardTeam/golibs/netutil/sysresolv" "github.com/AdguardTeam/golibs/stringutil" "github.com/miekg/dns" ) // DefaultTimeout is the default upstream timeout const DefaultTimeout = 10 * time.Second // defaultLocalTimeout is the default timeout for resolving addresses from // locally-served networks. It is assumed that local resolvers should work much // faster than ordinary upstreams. const defaultLocalTimeout = 1 * time.Second // defaultClientIDCacheCount is the default count of items in the LRU ClientID // cache. The assumption here is that there won't be more than this many // requests between the BeforeRequestHandler stage and the actual processing. const defaultClientIDCacheCount = 1024 var defaultDNS = []string{ "https://dns10.quad9.net/dns-query", } var defaultBootstrap = []string{"9.9.9.10", "149.112.112.10", "2620:fe::10", "2620:fe::fe:10"} // Often requested by all kinds of DNS probes var defaultBlockedHosts = []string{"version.bind", "id.server", "hostname.bind"} var ( // defaultUDPListenAddrs are the default UDP addresses for the server. defaultUDPListenAddrs = []*net.UDPAddr{{Port: 53}} // defaultTCPListenAddrs are the default TCP addresses for the server. defaultTCPListenAddrs = []*net.TCPAddr{{Port: 53}} ) var webRegistered bool // DHCP is an interface for accessing DHCP lease data needed in this package. type DHCP interface { // HostByIP returns the hostname of the DHCP client with the given IP // address. The address will be netip.Addr{} if there is no such client, // due to an assumption that a DHCP client must always have an IP address. HostByIP(ip netip.Addr) (host string) // IPByHost returns the IP address of the DHCP client with the given // hostname. The hostname will be an empty string if there is no such // client, due to an assumption that a DHCP client must always have a // hostname, either set by the client or assigned automatically. IPByHost(host string) (ip netip.Addr) // Enabled returns true if DHCP provides information about clients. Enabled() (ok bool) } // SystemResolvers is an interface for accessing the OS-provided resolvers. type SystemResolvers interface { // Addrs returns the list of system resolvers' addresses. Callers must // clone the returned slice before modifying it. Implementations of Addrs // must be safe for concurrent use. Addrs() (addrs []netip.AddrPort) } // Server is the main way to start a DNS server. // // Example: // // s := dnsforward.Server{} // err := s.Start(nil) // will start a DNS server listening on default port 53, in a goroutine // err := s.Reconfigure(ServerConfig{UDPListenAddr: &net.UDPAddr{Port: 53535}}) // will reconfigure running DNS server to listen on UDP port 53535 // err := s.Stop() // will stop listening on port 53535 and cancel all goroutines // err := s.Start(nil) // will start listening again, on port 53535, in a goroutine // // The zero Server is empty and ready for use. type Server struct { // dnsProxy is the DNS proxy for forwarding client's DNS requests. dnsProxy *proxy.Proxy // dnsFilter is the DNS filter for filtering client's DNS requests and // responses. dnsFilter *filtering.DNSFilter // dhcpServer is the DHCP server for accessing lease data. dhcpServer DHCP // queryLog is the query log for client's DNS requests, responses and // filtering results. queryLog querylog.QueryLog // stats is the statistics collector for client's DNS usage data. stats stats.Interface // access drops disallowed clients. access *accessManager // localDomainSuffix is the suffix used to detect internal hosts. It // must be a valid domain name plus dots on each side. localDomainSuffix string // ipset processes DNS requests using ipset data. ipset ipsetCtx // privateNets is the configured set of IP networks considered private. privateNets netutil.SubnetSet // addrProc, if not nil, is used to process clients' IP addresses with rDNS, // WHOIS, etc. addrProc client.AddressProcessor // localResolvers is a DNS proxy instance used to resolve PTR records for // addresses considered private as per the [privateNets]. // // TODO(e.burkov): Remove once the local resolvers logic moved to dnsproxy. localResolvers *proxy.Proxy // sysResolvers used to fetch system resolvers to use by default for private // PTR resolving. sysResolvers SystemResolvers // etcHosts contains the current data from the system's hosts files. etcHosts upstream.Resolver // bootstrap is the resolver for upstreams' hostnames. bootstrap upstream.Resolver // bootResolvers are the resolvers that should be used for // bootstrapping along with [etcHosts]. // // TODO(e.burkov): Use [proxy.UpstreamConfig] when it will implement the // [upstream.Resolver] interface. bootResolvers []*upstream.UpstreamResolver // recDetector is a cache for recursive requests. It is used to detect and // prevent recursive requests only for private upstreams. // // See https://github.com/adguardTeam/adGuardHome/issues/3185#issuecomment-851048135. recDetector *recursionDetector // dns64Pref is the NAT64 prefix used for DNS64 response mapping. The major // part of DNS64 happens inside the [proxy] package, but there still are // some places where response mapping is needed (e.g. DHCP). dns64Pref netip.Prefix // anonymizer masks the client's IP addresses if needed. anonymizer *aghnet.IPMut // clientIDCache is a temporary storage for ClientIDs that were extracted // during the BeforeRequestHandler stage. clientIDCache cache.Cache // internalProxy resolves internal requests from the application itself. It // isn't started and so no listen ports are required. internalProxy *proxy.Proxy // isRunning is true if the DNS server is running. isRunning bool // protectionUpdateInProgress is used to make sure that only one goroutine // updating the protection configuration after a pause is running at a time. protectionUpdateInProgress atomic.Bool // conf is the current configuration of the server. conf ServerConfig // serverLock protects Server. serverLock sync.RWMutex } // defaultLocalDomainSuffix is the default suffix used to detect internal hosts // when no suffix is provided. // // See the documentation for Server.localDomainSuffix. const defaultLocalDomainSuffix = "lan" // DNSCreateParams are parameters to create a new server. type DNSCreateParams struct { DNSFilter *filtering.DNSFilter Stats stats.Interface QueryLog querylog.QueryLog DHCPServer DHCP PrivateNets netutil.SubnetSet Anonymizer *aghnet.IPMut EtcHosts *aghnet.HostsContainer LocalDomain string } const ( // recursionTTL is the time recursive request is cached for. recursionTTL = 1 * time.Second // cachedRecurrentReqNum is the maximum number of cached recurrent // requests. cachedRecurrentReqNum = 1000 ) // NewServer creates a new instance of the dnsforward.Server // Note: this function must be called only once // // TODO(a.garipov): How many constructors and initializers does this thing have? // Refactor! func NewServer(p DNSCreateParams) (s *Server, err error) { var localDomainSuffix string if p.LocalDomain == "" { localDomainSuffix = defaultLocalDomainSuffix } else { err = netutil.ValidateDomainName(p.LocalDomain) if err != nil { return nil, fmt.Errorf("local domain: %w", err) } localDomainSuffix = p.LocalDomain } if p.Anonymizer == nil { p.Anonymizer = aghnet.NewIPMut(nil) } var etcHosts upstream.Resolver if p.EtcHosts != nil { etcHosts = upstream.NewHostsResolver(p.EtcHosts) } s = &Server{ dnsFilter: p.DNSFilter, dhcpServer: p.DHCPServer, stats: p.Stats, queryLog: p.QueryLog, privateNets: p.PrivateNets, // TODO(e.burkov): Use some case-insensitive string comparison. localDomainSuffix: strings.ToLower(localDomainSuffix), etcHosts: etcHosts, recDetector: newRecursionDetector(recursionTTL, cachedRecurrentReqNum), clientIDCache: cache.New(cache.Config{ EnableLRU: true, MaxCount: defaultClientIDCacheCount, }), anonymizer: p.Anonymizer, conf: ServerConfig{ ServePlainDNS: true, }, } s.sysResolvers, err = sysresolv.NewSystemResolvers(nil, defaultPlainDNSPort) if err != nil { return nil, fmt.Errorf("initializing system resolvers: %w", err) } if runtime.GOARCH == "mips" || runtime.GOARCH == "mipsle" { // Use plain DNS on MIPS, encryption is too slow defaultDNS = defaultBootstrap } return s, nil } // Close gracefully closes the server. It is safe for concurrent use. // // TODO(e.burkov): A better approach would be making Stop method waiting for all // its workers finished. But it would require the upstream.Upstream to have the // Close method to prevent from hanging while waiting for unresponsive server to // respond. func (s *Server) Close() { s.serverLock.Lock() defer s.serverLock.Unlock() // TODO(s.chzhen): Remove it. s.stats = nil s.queryLog = nil s.dnsProxy = nil if err := s.ipset.close(); err != nil { log.Error("dnsforward: closing ipset: %s", err) } } // WriteDiskConfig - write configuration func (s *Server) WriteDiskConfig(c *Config) { s.serverLock.RLock() defer s.serverLock.RUnlock() sc := s.conf.Config *c = sc c.RatelimitWhitelist = slices.Clone(sc.RatelimitWhitelist) c.BootstrapDNS = slices.Clone(sc.BootstrapDNS) c.FallbackDNS = slices.Clone(sc.FallbackDNS) c.AllowedClients = slices.Clone(sc.AllowedClients) c.DisallowedClients = slices.Clone(sc.DisallowedClients) c.BlockedHosts = slices.Clone(sc.BlockedHosts) c.TrustedProxies = slices.Clone(sc.TrustedProxies) c.UpstreamDNS = slices.Clone(sc.UpstreamDNS) } // LocalPTRResolvers returns the current local PTR resolver configuration. func (s *Server) LocalPTRResolvers() (localPTRResolvers []string) { s.serverLock.RLock() defer s.serverLock.RUnlock() return slices.Clone(s.conf.LocalPTRResolvers) } // AddrProcConfig returns the current address processing configuration. Only // fields c.UsePrivateRDNS, c.UseRDNS, and c.UseWHOIS are filled. func (s *Server) AddrProcConfig() (c *client.DefaultAddrProcConfig) { s.serverLock.RLock() defer s.serverLock.RUnlock() return &client.DefaultAddrProcConfig{ UsePrivateRDNS: s.conf.UsePrivateRDNS, UseRDNS: s.conf.AddrProcConf.UseRDNS, UseWHOIS: s.conf.AddrProcConf.UseWHOIS, } } // Resolve gets IP addresses by host name from an upstream server. No // request/response filtering is performed. Query log and Stats are not // updated. This method may be called before [Server.Start]. func (s *Server) Resolve(ctx context.Context, net, host string) (addr []netip.Addr, err error) { s.serverLock.RLock() defer s.serverLock.RUnlock() return s.internalProxy.LookupNetIP(ctx, net, host) } const ( // ErrRDNSNoData is returned by [RDNSExchanger.Exchange] when the answer // section of response is either NODATA or has no PTR records. ErrRDNSNoData errors.Error = "no ptr data in response" // ErrRDNSFailed is returned by [RDNSExchanger.Exchange] if the received // response is not a NOERROR or NXDOMAIN. ErrRDNSFailed errors.Error = "failed to resolve ptr" ) // type check var _ rdns.Exchanger = (*Server)(nil) // Exchange implements the [rdns.Exchanger] interface for *Server. func (s *Server) Exchange(ip netip.Addr) (host string, ttl time.Duration, err error) { s.serverLock.RLock() defer s.serverLock.RUnlock() arpa, err := netutil.IPToReversedAddr(ip.AsSlice()) if err != nil { return "", 0, fmt.Errorf("reversing ip: %w", err) } arpa = dns.Fqdn(arpa) req := &dns.Msg{ MsgHdr: dns.MsgHdr{ Id: dns.Id(), RecursionDesired: true, }, Compress: true, Question: []dns.Question{{ Name: arpa, Qtype: dns.TypePTR, Qclass: dns.ClassINET, }}, } dctx := &proxy.DNSContext{ Proto: "udp", Req: req, } var resolver *proxy.Proxy var errMsg string if s.privateNets.Contains(ip) { if !s.conf.UsePrivateRDNS { return "", 0, nil } resolver = s.localResolvers errMsg = "resolving a private address: %w" s.recDetector.add(*req) } else { resolver = s.internalProxy errMsg = "resolving an address: %w" } if err = resolver.Resolve(dctx); err != nil { return "", 0, fmt.Errorf(errMsg, err) } return hostFromPTR(dctx.Res) } // hostFromPTR returns domain name from the PTR response or error. func hostFromPTR(resp *dns.Msg) (host string, ttl time.Duration, err error) { // Distinguish between NODATA response and a failed request. if resp.Rcode != dns.RcodeSuccess && resp.Rcode != dns.RcodeNameError { return "", 0, fmt.Errorf( "received %s response: %w", dns.RcodeToString[resp.Rcode], ErrRDNSFailed, ) } var ttlSec uint32 log.Debug("dnsforward: resolving ptr, received %d answers", len(resp.Answer)) for _, ans := range resp.Answer { ptr, ok := ans.(*dns.PTR) if !ok { continue } // Respect zero TTL records since some DNS servers use it to // locally-resolved addresses. // // See https://github.com/AdguardTeam/AdGuardHome/issues/6046. if ptr.Hdr.Ttl >= ttlSec { host = ptr.Ptr ttlSec = ptr.Hdr.Ttl } } if host != "" { // NOTE: Don't use [aghnet.NormalizeDomain] to retain original letter // case. host = strings.TrimSuffix(host, ".") ttl = time.Duration(ttlSec) * time.Second return host, ttl, nil } return "", 0, ErrRDNSNoData } // Start starts the DNS server. It must only be called after [Server.Prepare]. func (s *Server) Start() error { s.serverLock.Lock() defer s.serverLock.Unlock() return s.startLocked() } // startLocked starts the DNS server without locking. s.serverLock is expected // to be locked. func (s *Server) startLocked() error { // TODO(e.burkov): Use context properly. err := s.dnsProxy.Start(context.Background()) if err == nil { s.isRunning = true } return err } // prepareLocalResolvers initializes the local upstreams configuration using // boot as bootstrap. It assumes that s.serverLock is locked or s not running. func (s *Server) prepareLocalResolvers( boot upstream.Resolver, ) (uc *proxy.UpstreamConfig, err error) { set, err := s.conf.ourAddrsSet() if err != nil { // Don't wrap the error because it's informative enough as is. return nil, err } resolvers := s.conf.LocalPTRResolvers confNeedsFiltering := len(resolvers) > 0 if confNeedsFiltering { resolvers = stringutil.FilterOut(resolvers, IsCommentOrEmpty) } else { sysResolvers := slices.DeleteFunc(slices.Clone(s.sysResolvers.Addrs()), set.Has) resolvers = make([]string, 0, len(sysResolvers)) for _, r := range sysResolvers { resolvers = append(resolvers, r.String()) } } log.Debug("dnsforward: upstreams to resolve ptr for local addresses: %v", resolvers) uc, err = s.prepareUpstreamConfig(resolvers, nil, &upstream.Options{ Bootstrap: boot, Timeout: defaultLocalTimeout, // TODO(e.burkov): Should we verify server's certificates? PreferIPv6: s.conf.BootstrapPreferIPv6, }) if err != nil { return nil, fmt.Errorf("preparing private upstreams: %w", err) } if confNeedsFiltering { err = filterOutAddrs(uc, set) if err != nil { return nil, fmt.Errorf("filtering private upstreams: %w", err) } } return uc, nil } // LocalResolversError is an error type for errors during local resolvers setup. // This is only needed to distinguish these errors from errors returned by // creating the proxy. type LocalResolversError struct { Err error } // type check var _ error = (*LocalResolversError)(nil) // Error implements the error interface for *LocalResolversError. func (err *LocalResolversError) Error() (s string) { return fmt.Sprintf("creating local resolvers: %s", err.Err) } // type check var _ errors.Wrapper = (*LocalResolversError)(nil) // Unwrap implements the [errors.Wrapper] interface for *LocalResolversError. func (err *LocalResolversError) Unwrap() error { return err.Err } // setupLocalResolvers initializes and sets the resolvers for local addresses. // It assumes s.serverLock is locked or s not running. It returns the upstream // configuration used for private PTR resolving, or nil if it's disabled. Note, // that it's safe to put nil into [proxy.Config.PrivateRDNSUpstreamConfig]. func (s *Server) setupLocalResolvers(boot upstream.Resolver) (uc *proxy.UpstreamConfig, err error) { if !s.conf.UsePrivateRDNS { // It's safe to put nil into [proxy.Config.PrivateRDNSUpstreamConfig]. return nil, nil } uc, err = s.prepareLocalResolvers(boot) if err != nil { // Don't wrap the error because it's informative enough as is. return nil, err } localResolvers, err := proxy.New(&proxy.Config{ UpstreamConfig: uc, }) if err != nil { return nil, &LocalResolversError{Err: err} } s.localResolvers = localResolvers // TODO(e.burkov): Should we also consider the DNS64 usage? return uc, nil } // Prepare initializes parameters of s using data from conf. conf must not be // nil. func (s *Server) Prepare(conf *ServerConfig) (err error) { s.conf = *conf // dnsFilter can be nil during application update. if s.dnsFilter != nil { mode, bIPv4, bIPv6 := s.dnsFilter.BlockingMode() err = validateBlockingMode(mode, bIPv4, bIPv6) if err != nil { return fmt.Errorf("checking blocking mode: %w", err) } } s.initDefaultSettings() boot, err := s.prepareInternalDNS() if err != nil { // Don't wrap the error, because it's informative enough as is. return err } proxyConfig, err := s.newProxyConfig() if err != nil { return fmt.Errorf("preparing proxy: %w", err) } s.setupDNS64() s.access, err = newAccessCtx( s.conf.AllowedClients, s.conf.DisallowedClients, s.conf.BlockedHosts, ) if err != nil { return fmt.Errorf("preparing access: %w", err) } // TODO(e.burkov): Remove once the local resolvers logic moved to dnsproxy. proxyConfig.PrivateRDNSUpstreamConfig, err = s.setupLocalResolvers(boot) if err != nil { return fmt.Errorf("setting up resolvers: %w", err) } proxyConfig.Fallbacks, err = s.setupFallbackDNS() if err != nil { return fmt.Errorf("setting up fallback dns servers: %w", err) } dnsProxy, err := proxy.New(proxyConfig) if err != nil { return fmt.Errorf("creating proxy: %w", err) } s.dnsProxy = dnsProxy s.recDetector.clear() s.setupAddrProc() s.registerHandlers() return nil } // prepareInternalDNS initializes the internal state of s before initializing // the primary DNS proxy instance. It assumes s.serverLock is locked or the // Server not running. func (s *Server) prepareInternalDNS() (boot upstream.Resolver, err error) { err = s.prepareIpsetListSettings() if err != nil { return nil, fmt.Errorf("preparing ipset settings: %w", err) } s.bootstrap, s.bootResolvers, err = s.createBootstrap(s.conf.BootstrapDNS, &upstream.Options{ Timeout: DefaultTimeout, HTTPVersions: UpstreamHTTPVersions(s.conf.UseHTTP3Upstreams), }) if err != nil { // Don't wrap the error, because it's informative enough as is. return nil, err } err = s.prepareUpstreamSettings(s.bootstrap) if err != nil { // Don't wrap the error, because it's informative enough as is. return s.bootstrap, err } err = s.prepareInternalProxy() if err != nil { return s.bootstrap, fmt.Errorf("preparing internal proxy: %w", err) } return s.bootstrap, nil } // setupFallbackDNS initializes the fallback DNS servers. func (s *Server) setupFallbackDNS() (uc *proxy.UpstreamConfig, err error) { fallbacks := s.conf.FallbackDNS fallbacks = stringutil.FilterOut(fallbacks, IsCommentOrEmpty) if len(fallbacks) == 0 { return nil, nil } uc, err = proxy.ParseUpstreamsConfig(fallbacks, &upstream.Options{ // TODO(s.chzhen): Investigate if other options are needed. Timeout: s.conf.UpstreamTimeout, PreferIPv6: s.conf.BootstrapPreferIPv6, // TODO(e.burkov): Use bootstrap. }) if err != nil { // Do not wrap the error because it's informative enough as is. return nil, err } return uc, nil } // setupAddrProc initializes the address processor. It assumes s.serverLock is // locked or the Server not running. func (s *Server) setupAddrProc() { // TODO(a.garipov): This is a crutch for tests; remove. if s.conf.AddrProcConf == nil { s.conf.AddrProcConf = &client.DefaultAddrProcConfig{} } if s.conf.AddrProcConf.AddressUpdater == nil { s.addrProc = client.EmptyAddrProc{} } else { c := s.conf.AddrProcConf c.DialContext = s.DialContext c.PrivateSubnets = s.privateNets c.UsePrivateRDNS = s.conf.UsePrivateRDNS s.addrProc = client.NewDefaultAddrProc(s.conf.AddrProcConf) // Clear the initial addresses to not resolve them again. // // TODO(a.garipov): Consider ways of removing this once more client // logic is moved to package client. c.InitialAddresses = nil } } // validateBlockingMode returns an error if the blocking mode data aren't valid. func validateBlockingMode( mode filtering.BlockingMode, blockingIPv4, blockingIPv6 netip.Addr, ) (err error) { switch mode { case filtering.BlockingModeDefault, filtering.BlockingModeNXDOMAIN, filtering.BlockingModeREFUSED, filtering.BlockingModeNullIP: return nil case filtering.BlockingModeCustomIP: if !blockingIPv4.Is4() { return fmt.Errorf("blocking_ipv4 must be valid ipv4 on custom_ip blocking_mode") } else if !blockingIPv6.Is6() { return fmt.Errorf("blocking_ipv6 must be valid ipv6 on custom_ip blocking_mode") } return nil default: return fmt.Errorf("bad blocking mode %q", mode) } } // prepareInternalProxy initializes the DNS proxy that is used for internal DNS // queries, such as public clients PTR resolving and updater hostname resolving. func (s *Server) prepareInternalProxy() (err error) { srvConf := s.conf conf := &proxy.Config{ CacheEnabled: true, CacheSizeBytes: 4096, UpstreamConfig: srvConf.UpstreamConfig, MaxGoroutines: s.conf.MaxGoroutines, } err = setProxyUpstreamMode(conf, srvConf.UpstreamMode, srvConf.FastestTimeout.Duration) if err != nil { return fmt.Errorf("invalid upstream mode: %w", err) } s.internalProxy, err = proxy.New(conf) return err } // Stop stops the DNS server. func (s *Server) Stop() error { s.serverLock.Lock() defer s.serverLock.Unlock() return s.stopLocked() } // stopLocked stops the DNS server without locking. s.serverLock is expected to // be locked. func (s *Server) stopLocked() (err error) { // TODO(e.burkov, a.garipov): Return critical errors, not just log them. // This will require filtering all the non-critical errors in // [upstream.Upstream] implementations. if s.dnsProxy != nil { // TODO(e.burkov): Use context properly. err = s.dnsProxy.Shutdown(context.Background()) if err != nil { log.Error("dnsforward: closing primary resolvers: %s", err) } } logCloserErr(s.internalProxy.UpstreamConfig, "dnsforward: closing internal resolvers: %s") if s.localResolvers != nil { logCloserErr(s.localResolvers.UpstreamConfig, "dnsforward: closing local resolvers: %s") } for _, b := range s.bootResolvers { logCloserErr(b, "dnsforward: closing bootstrap %s: %s", b.Address()) } s.isRunning = false return nil } // logCloserErr logs the error returned by c, if any. func logCloserErr(c io.Closer, format string, args ...any) { if c == nil { return } err := c.Close() if err != nil { log.Error(format, append(args, err)...) } } // IsRunning returns true if the DNS server is running. func (s *Server) IsRunning() bool { s.serverLock.RLock() defer s.serverLock.RUnlock() return s.isRunning } // srvClosedErr is returned when the method can't complete without inaccessible // data from the closing server. const srvClosedErr errors.Error = "server is closed" // proxy returns a pointer to the current DNS proxy instance. If p is nil, the // server is closing. // // See https://github.com/AdguardTeam/AdGuardHome/issues/3655. func (s *Server) proxy() (p *proxy.Proxy) { s.serverLock.RLock() defer s.serverLock.RUnlock() return s.dnsProxy } // Reconfigure applies the new configuration to the DNS server. func (s *Server) Reconfigure(conf *ServerConfig) error { s.serverLock.Lock() defer s.serverLock.Unlock() log.Info("dnsforward: starting reconfiguring server") defer log.Info("dnsforward: finished reconfiguring server") err := s.stopLocked() if err != nil { return fmt.Errorf("could not reconfigure the server: %w", err) } // It seems that net.Listener.Close() doesn't close file descriptors right away. // We wait for some time and hope that this fd will be closed. time.Sleep(100 * time.Millisecond) // TODO(a.garipov): This whole piece of API is weird and needs to be remade. if conf == nil { conf = &s.conf } else { closeErr := s.addrProc.Close() if closeErr != nil { log.Error("dnsforward: closing address processor: %s", closeErr) } } // TODO(e.burkov): It seems an error here brings the server down, which is // not reliable enough. err = s.Prepare(conf) if err != nil { return fmt.Errorf("could not reconfigure the server: %w", err) } err = s.startLocked() if err != nil { return fmt.Errorf("could not reconfigure the server: %w", err) } return nil } // ServeHTTP is a HTTP handler method we use to provide DNS-over-HTTPS. func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) { if prx := s.proxy(); prx != nil { prx.ServeHTTP(w, r) } } // IsBlockedClient returns true if the client is blocked by the current access // settings. func (s *Server) IsBlockedClient(ip netip.Addr, clientID string) (blocked bool, rule string) { s.serverLock.RLock() defer s.serverLock.RUnlock() blockedByIP := false if ip != (netip.Addr{}) { blockedByIP, rule = s.access.isBlockedIP(ip) } allowlistMode := s.access.allowlistMode() blockedByClientID := s.access.isBlockedClientID(clientID) // Allow if at least one of the checks allows in allowlist mode, but block // if at least one of the checks blocks in blocklist mode. if allowlistMode && blockedByIP && blockedByClientID { log.Debug("dnsforward: client %v (id %q) is not in access allowlist", ip, clientID) // Return now without substituting the empty rule for the // clientID because the rule can't be empty here. return true, rule } else if !allowlistMode && (blockedByIP || blockedByClientID) { log.Debug("dnsforward: client %v (id %q) is in access blocklist", ip, clientID) blocked = true } return blocked, aghalg.Coalesce(rule, clientID) }