diff --git a/control/controlknobs/controlknobs.go b/control/controlknobs/controlknobs.go index 0b86c2d3b..f4cef7b41 100644 --- a/control/controlknobs/controlknobs.go +++ b/control/controlknobs/controlknobs.go @@ -81,6 +81,15 @@ type Knobs struct { // how to dial the destination address. When true, it also makes the DNS forwarder // use UserDial instead of SystemDial when dialing resolvers. UserDialUseRoutes atomic.Bool + + // DisableSplitDNSWhenNoCustomResolvers indicates that the node's DNS manager + // should not adopt a split DNS configuration even though the Config of the + // resolver only contains routes that do not specify custom resolver(s), hence + // all DNS queries can be safely sent to the upstream DNS resolver and the + // node's DNS forwarder doesn't need to handle all DNS traffic. + // This is for now (2024-06-06) an iOS-specific battery life optimization, + // and this knob allows us to disable the optimization remotely if needed. + DisableSplitDNSWhenNoCustomResolvers atomic.Bool } // UpdateFromNodeAttributes updates k (if non-nil) based on the provided self @@ -91,22 +100,23 @@ func (k *Knobs) UpdateFromNodeAttributes(capMap tailcfg.NodeCapMap) { } has := capMap.Contains var ( - keepFullWG = has(tailcfg.NodeAttrDebugDisableWGTrim) - disableDRPO = has(tailcfg.NodeAttrDebugDisableDRPO) - disableUPnP = has(tailcfg.NodeAttrDisableUPnP) - randomizeClientPort = has(tailcfg.NodeAttrRandomizeClientPort) - disableDeltaUpdates = has(tailcfg.NodeAttrDisableDeltaUpdates) - oneCGNAT opt.Bool - forceBackgroundSTUN = has(tailcfg.NodeAttrDebugForceBackgroundSTUN) - peerMTUEnable = has(tailcfg.NodeAttrPeerMTUEnable) - dnsForwarderDisableTCPRetries = has(tailcfg.NodeAttrDNSForwarderDisableTCPRetries) - silentDisco = has(tailcfg.NodeAttrSilentDisco) - forceIPTables = has(tailcfg.NodeAttrLinuxMustUseIPTables) - forceNfTables = has(tailcfg.NodeAttrLinuxMustUseNfTables) - seamlessKeyRenewal = has(tailcfg.NodeAttrSeamlessKeyRenewal) - probeUDPLifetime = has(tailcfg.NodeAttrProbeUDPLifetime) - appCStoreRoutes = has(tailcfg.NodeAttrStoreAppCRoutes) - userDialUseRoutes = has(tailcfg.NodeAttrUserDialUseRoutes) + keepFullWG = has(tailcfg.NodeAttrDebugDisableWGTrim) + disableDRPO = has(tailcfg.NodeAttrDebugDisableDRPO) + disableUPnP = has(tailcfg.NodeAttrDisableUPnP) + randomizeClientPort = has(tailcfg.NodeAttrRandomizeClientPort) + disableDeltaUpdates = has(tailcfg.NodeAttrDisableDeltaUpdates) + oneCGNAT opt.Bool + forceBackgroundSTUN = has(tailcfg.NodeAttrDebugForceBackgroundSTUN) + peerMTUEnable = has(tailcfg.NodeAttrPeerMTUEnable) + dnsForwarderDisableTCPRetries = has(tailcfg.NodeAttrDNSForwarderDisableTCPRetries) + silentDisco = has(tailcfg.NodeAttrSilentDisco) + forceIPTables = has(tailcfg.NodeAttrLinuxMustUseIPTables) + forceNfTables = has(tailcfg.NodeAttrLinuxMustUseNfTables) + seamlessKeyRenewal = has(tailcfg.NodeAttrSeamlessKeyRenewal) + probeUDPLifetime = has(tailcfg.NodeAttrProbeUDPLifetime) + appCStoreRoutes = has(tailcfg.NodeAttrStoreAppCRoutes) + userDialUseRoutes = has(tailcfg.NodeAttrUserDialUseRoutes) + disableSplitDNSWhenNoCustomResolvers = has(tailcfg.NodeAttrDisableSplitDNSWhenNoCustomResolvers) ) if has(tailcfg.NodeAttrOneCGNATEnable) { @@ -131,6 +141,7 @@ func (k *Knobs) UpdateFromNodeAttributes(capMap tailcfg.NodeCapMap) { k.ProbeUDPLifetime.Store(probeUDPLifetime) k.AppCStoreRoutes.Store(appCStoreRoutes) k.UserDialUseRoutes.Store(userDialUseRoutes) + k.DisableSplitDNSWhenNoCustomResolvers.Store(disableSplitDNSWhenNoCustomResolvers) } // AsDebugJSON returns k as something that can be marshalled with json.Marshal @@ -140,21 +151,22 @@ func (k *Knobs) AsDebugJSON() map[string]any { return nil } return map[string]any{ - "DisableUPnP": k.DisableUPnP.Load(), - "DisableDRPO": k.DisableDRPO.Load(), - "KeepFullWGConfig": k.KeepFullWGConfig.Load(), - "RandomizeClientPort": k.RandomizeClientPort.Load(), - "OneCGNAT": k.OneCGNAT.Load(), - "ForceBackgroundSTUN": k.ForceBackgroundSTUN.Load(), - "DisableDeltaUpdates": k.DisableDeltaUpdates.Load(), - "PeerMTUEnable": k.PeerMTUEnable.Load(), - "DisableDNSForwarderTCPRetries": k.DisableDNSForwarderTCPRetries.Load(), - "SilentDisco": k.SilentDisco.Load(), - "LinuxForceIPTables": k.LinuxForceIPTables.Load(), - "LinuxForceNfTables": k.LinuxForceNfTables.Load(), - "SeamlessKeyRenewal": k.SeamlessKeyRenewal.Load(), - "ProbeUDPLifetime": k.ProbeUDPLifetime.Load(), - "AppCStoreRoutes": k.AppCStoreRoutes.Load(), - "UserDialUseRoutes": k.UserDialUseRoutes.Load(), + "DisableUPnP": k.DisableUPnP.Load(), + "DisableDRPO": k.DisableDRPO.Load(), + "KeepFullWGConfig": k.KeepFullWGConfig.Load(), + "RandomizeClientPort": k.RandomizeClientPort.Load(), + "OneCGNAT": k.OneCGNAT.Load(), + "ForceBackgroundSTUN": k.ForceBackgroundSTUN.Load(), + "DisableDeltaUpdates": k.DisableDeltaUpdates.Load(), + "PeerMTUEnable": k.PeerMTUEnable.Load(), + "DisableDNSForwarderTCPRetries": k.DisableDNSForwarderTCPRetries.Load(), + "SilentDisco": k.SilentDisco.Load(), + "LinuxForceIPTables": k.LinuxForceIPTables.Load(), + "LinuxForceNfTables": k.LinuxForceNfTables.Load(), + "SeamlessKeyRenewal": k.SeamlessKeyRenewal.Load(), + "ProbeUDPLifetime": k.ProbeUDPLifetime.Load(), + "AppCStoreRoutes": k.AppCStoreRoutes.Load(), + "UserDialUseRoutes": k.UserDialUseRoutes.Load(), + "DisableSplitDNSWhenNoCustomResolvers": k.DisableSplitDNSWhenNoCustomResolvers.Load(), } } diff --git a/net/dns/manager.go b/net/dns/manager.go index cdbc676eb..61c6dfecc 100644 --- a/net/dns/manager.go +++ b/net/dns/manager.go @@ -52,6 +52,7 @@ type Manager struct { resolver *resolver.Resolver os OSConfigurator + knobs *controlknobs.Knobs goos string // if empty, gets set to runtime.GOOS } @@ -67,11 +68,13 @@ func NewManager(logf logger.Logf, oscfg OSConfigurator, health *health.Tracker, if goos == "" { goos = runtime.GOOS } + m := &Manager{ logf: logf, resolver: resolver.New(logf, linkSel, dialer, knobs), os: oscfg, health: health, + knobs: knobs, goos: goos, } m.ctx, m.ctxCancel = context.WithCancel(context.Background()) @@ -273,8 +276,12 @@ func (m *Manager) compileConfig(cfg Config) (rcfg resolver.Config, ocfg OSConfig // a query for 'work-laptop' might lead to search domain expansion, resolving // as 'work-laptop.aws.com' for example. if m.goos == "ios" && rcfg.RoutesRequireNoCustomResolvers() { - for r := range rcfg.Routes { - ocfg.MatchDomains = append(ocfg.MatchDomains, r) + if !m.disableSplitDNSOptimization() { + for r := range rcfg.Routes { + ocfg.MatchDomains = append(ocfg.MatchDomains, r) + } + } else { + m.logf("iOS split DNS is disabled by nodeattr") } } var defaultRoutes []*dnstype.Resolver @@ -288,6 +295,10 @@ func (m *Manager) compileConfig(cfg Config) (rcfg resolver.Config, ocfg OSConfig return rcfg, ocfg, nil } +func (m *Manager) disableSplitDNSOptimization() bool { + return m.knobs.DisableSplitDNSWhenNoCustomResolvers.Load() +} + // toIPsOnly returns only the IP portion of dnstype.Resolver. // Only safe to use if the resolvers slice has been cleared of // DoH or custom-port entries with something like hasDefaultIPResolversOnly. diff --git a/tailcfg/tailcfg.go b/tailcfg/tailcfg.go index f9cf9f8fc..c5a517cba 100644 --- a/tailcfg/tailcfg.go +++ b/tailcfg/tailcfg.go @@ -2286,6 +2286,17 @@ const ( // NodeAttrSSHBehaviorV1 forces SSH to use the V1 behavior (no su, run SFTP in-process) // Added 2024-05-29 in Tailscale version 1.68. NodeAttrSSHBehaviorV1 NodeCapability = "ssh-behavior-v1" + + // NodeAttrDisableSplitDNSWhenNoCustomResolvers indicates that the node's + // DNS manager should not adopt a split DNS configuration even though the + // Config of the resolver only contains routes that do not specify custom + // resolver(s), hence all DNS queries can be safely sent to the upstream + // DNS resolver and the node's DNS forwarder doesn't need to handle all + // DNS traffic. + // This is for now (2024-06-06) an iOS-specific battery life optimization, + // and this node attribute allows us to disable the optimization remotely + // if needed. + NodeAttrDisableSplitDNSWhenNoCustomResolvers NodeCapability = "disable-split-dns-when-no-custom-resolvers" ) // SetDNSRequest is a request to add a DNS record.