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Diffstat (limited to 'pkg/tcpip/stack/ndp.go')
| -rw-r--r-- | pkg/tcpip/stack/ndp.go | 1157 |
1 files changed, 1157 insertions, 0 deletions
diff --git a/pkg/tcpip/stack/ndp.go b/pkg/tcpip/stack/ndp.go new file mode 100644 index 000000000..90664ba8a --- /dev/null +++ b/pkg/tcpip/stack/ndp.go @@ -0,0 +1,1157 @@ +// Copyright 2019 The gVisor Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +package stack + +import ( + "fmt" + "log" + "time" + + "gvisor.dev/gvisor/pkg/tcpip" + "gvisor.dev/gvisor/pkg/tcpip/buffer" + "gvisor.dev/gvisor/pkg/tcpip/header" +) + +const ( + // defaultDupAddrDetectTransmits is the default number of NDP Neighbor + // Solicitation messages to send when doing Duplicate Address Detection + // for a tentative address. + // + // Default = 1 (from RFC 4862 section 5.1) + defaultDupAddrDetectTransmits = 1 + + // defaultRetransmitTimer is the default amount of time to wait between + // sending NDP Neighbor solicitation messages. + // + // Default = 1s (from RFC 4861 section 10). + defaultRetransmitTimer = time.Second + + // defaultHandleRAs is the default configuration for whether or not to + // handle incoming Router Advertisements as a host. + // + // Default = true. + defaultHandleRAs = true + + // defaultDiscoverDefaultRouters is the default configuration for + // whether or not to discover default routers from incoming Router + // Advertisements, as a host. + // + // Default = true. + defaultDiscoverDefaultRouters = true + + // defaultDiscoverOnLinkPrefixes is the default configuration for + // whether or not to discover on-link prefixes from incoming Router + // Advertisements' Prefix Information option, as a host. + // + // Default = true. + defaultDiscoverOnLinkPrefixes = true + + // defaultAutoGenGlobalAddresses is the default configuration for + // whether or not to generate global IPv6 addresses in response to + // receiving a new Prefix Information option with its Autonomous + // Address AutoConfiguration flag set, as a host. + // + // Default = true. + defaultAutoGenGlobalAddresses = true + + // minimumRetransmitTimer is the minimum amount of time to wait between + // sending NDP Neighbor solicitation messages. Note, RFC 4861 does + // not impose a minimum Retransmit Timer, but we do here to make sure + // the messages are not sent all at once. We also come to this value + // because in the RetransmitTimer field of a Router Advertisement, a + // value of 0 means unspecified, so the smallest valid value is 1. + // Note, the unit of the RetransmitTimer field in the Router + // Advertisement is milliseconds. + // + // Min = 1ms. + minimumRetransmitTimer = time.Millisecond + + // MaxDiscoveredDefaultRouters is the maximum number of discovered + // default routers. The stack should stop discovering new routers after + // discovering MaxDiscoveredDefaultRouters routers. + // + // This value MUST be at minimum 2 as per RFC 4861 section 6.3.4, and + // SHOULD be more. + // + // Max = 10. + MaxDiscoveredDefaultRouters = 10 + + // MaxDiscoveredOnLinkPrefixes is the maximum number of discovered + // on-link prefixes. The stack should stop discovering new on-link + // prefixes after discovering MaxDiscoveredOnLinkPrefixes on-link + // prefixes. + // + // Max = 10. + MaxDiscoveredOnLinkPrefixes = 10 + + // validPrefixLenForAutoGen is the expected prefix length that an + // address can be generated for. Must be 64 bits as the interface + // identifier (IID) is 64 bits and an IPv6 address is 128 bits, so + // 128 - 64 = 64. + validPrefixLenForAutoGen = 64 +) + +var ( + // MinPrefixInformationValidLifetimeForUpdate is the minimum Valid + // Lifetime to update the valid lifetime of a generated address by + // SLAAC. + // + // This is exported as a variable (instead of a constant) so tests + // can update it to a smaller value. + // + // Min = 2hrs. + MinPrefixInformationValidLifetimeForUpdate = 2 * time.Hour +) + +// NDPDispatcher is the interface integrators of netstack must implement to +// receive and handle NDP related events. +type NDPDispatcher interface { + // OnDuplicateAddressDetectionStatus will be called when the DAD process + // for an address (addr) on a NIC (with ID nicID) completes. resolved + // will be set to true if DAD completed successfully (no duplicate addr + // detected); false otherwise (addr was detected to be a duplicate on + // the link the NIC is a part of, or it was stopped for some other + // reason, such as the address being removed). If an error occured + // during DAD, err will be set and resolved must be ignored. + // + // This function is permitted to block indefinitely without interfering + // with the stack's operation. + OnDuplicateAddressDetectionStatus(nicID tcpip.NICID, addr tcpip.Address, resolved bool, err *tcpip.Error) + + // OnDefaultRouterDiscovered will be called when a new default router is + // discovered. Implementations must return true if the newly discovered + // router should be remembered. + // + // This function is not permitted to block indefinitely. This function + // is also not permitted to call into the stack. + OnDefaultRouterDiscovered(nicID tcpip.NICID, addr tcpip.Address) bool + + // OnDefaultRouterInvalidated will be called when a discovered default + // router that was remembered is invalidated. + // + // This function is not permitted to block indefinitely. This function + // is also not permitted to call into the stack. + OnDefaultRouterInvalidated(nicID tcpip.NICID, addr tcpip.Address) + + // OnOnLinkPrefixDiscovered will be called when a new on-link prefix is + // discovered. Implementations must return true if the newly discovered + // on-link prefix should be remembered. + // + // This function is not permitted to block indefinitely. This function + // is also not permitted to call into the stack. + OnOnLinkPrefixDiscovered(nicID tcpip.NICID, prefix tcpip.Subnet) bool + + // OnOnLinkPrefixInvalidated will be called when a discovered on-link + // prefix that was remembered is invalidated. + // + // This function is not permitted to block indefinitely. This function + // is also not permitted to call into the stack. + OnOnLinkPrefixInvalidated(nicID tcpip.NICID, prefix tcpip.Subnet) + + // OnAutoGenAddress will be called when a new prefix with its + // autonomous address-configuration flag set has been received and SLAAC + // has been performed. Implementations may prevent the stack from + // assigning the address to the NIC by returning false. + // + // This function is not permitted to block indefinitely. It must not + // call functions on the stack itself. + OnAutoGenAddress(tcpip.NICID, tcpip.AddressWithPrefix) bool + + // OnAutoGenAddressInvalidated will be called when an auto-generated + // address (as part of SLAAC) has been invalidated. + // + // This function is not permitted to block indefinitely. It must not + // call functions on the stack itself. + OnAutoGenAddressInvalidated(tcpip.NICID, tcpip.AddressWithPrefix) + + // OnRecursiveDNSServerOption will be called when an NDP option with + // recursive DNS servers has been received. Note, addrs may contain + // link-local addresses. + // + // It is up to the caller to use the DNS Servers only for their valid + // lifetime. OnRecursiveDNSServerOption may be called for new or + // already known DNS servers. If called with known DNS servers, their + // valid lifetimes must be refreshed to lifetime (it may be increased, + // decreased, or completely invalidated when lifetime = 0). + OnRecursiveDNSServerOption(nicID tcpip.NICID, addrs []tcpip.Address, lifetime time.Duration) +} + +// NDPConfigurations is the NDP configurations for the netstack. +type NDPConfigurations struct { + // The number of Neighbor Solicitation messages to send when doing + // Duplicate Address Detection for a tentative address. + // + // Note, a value of zero effectively disables DAD. + DupAddrDetectTransmits uint8 + + // The amount of time to wait between sending Neighbor solicitation + // messages. + // + // Must be greater than 0.5s. + RetransmitTimer time.Duration + + // HandleRAs determines whether or not Router Advertisements will be + // processed. + HandleRAs bool + + // DiscoverDefaultRouters determines whether or not default routers will + // be discovered from Router Advertisements. This configuration is + // ignored if HandleRAs is false. + DiscoverDefaultRouters bool + + // DiscoverOnLinkPrefixes determines whether or not on-link prefixes + // will be discovered from Router Advertisements' Prefix Information + // option. This configuration is ignored if HandleRAs is false. + DiscoverOnLinkPrefixes bool + + // AutoGenGlobalAddresses determines whether or not global IPv6 + // addresses will be generated for a NIC in response to receiving a new + // Prefix Information option with its Autonomous Address + // AutoConfiguration flag set, as a host, as per RFC 4862 (SLAAC). + // + // Note, if an address was already generated for some unique prefix, as + // part of SLAAC, this option does not affect whether or not the + // lifetime(s) of the generated address changes; this option only + // affects the generation of new addresses as part of SLAAC. + AutoGenGlobalAddresses bool +} + +// DefaultNDPConfigurations returns an NDPConfigurations populated with +// default values. +func DefaultNDPConfigurations() NDPConfigurations { + return NDPConfigurations{ + DupAddrDetectTransmits: defaultDupAddrDetectTransmits, + RetransmitTimer: defaultRetransmitTimer, + HandleRAs: defaultHandleRAs, + DiscoverDefaultRouters: defaultDiscoverDefaultRouters, + DiscoverOnLinkPrefixes: defaultDiscoverOnLinkPrefixes, + AutoGenGlobalAddresses: defaultAutoGenGlobalAddresses, + } +} + +// validate modifies an NDPConfigurations with valid values. If invalid values +// are present in c, the corresponding default values will be used instead. +// +// If RetransmitTimer is less than minimumRetransmitTimer, then a value of +// defaultRetransmitTimer will be used. +func (c *NDPConfigurations) validate() { + if c.RetransmitTimer < minimumRetransmitTimer { + c.RetransmitTimer = defaultRetransmitTimer + } +} + +// ndpState is the per-interface NDP state. +type ndpState struct { + // The NIC this ndpState is for. + nic *NIC + + // configs is the per-interface NDP configurations. + configs NDPConfigurations + + // The DAD state to send the next NS message, or resolve the address. + dad map[tcpip.Address]dadState + + // The default routers discovered through Router Advertisements. + defaultRouters map[tcpip.Address]defaultRouterState + + // The on-link prefixes discovered through Router Advertisements' Prefix + // Information option. + onLinkPrefixes map[tcpip.Subnet]onLinkPrefixState + + // The addresses generated by SLAAC. + autoGenAddresses map[tcpip.Address]autoGenAddressState +} + +// dadState holds the Duplicate Address Detection timer and channel to signal +// to the DAD goroutine that DAD should stop. +type dadState struct { + // The DAD timer to send the next NS message, or resolve the address. + timer *time.Timer + + // Used to let the DAD timer know that it has been stopped. + // + // Must only be read from or written to while protected by the lock of + // the NIC this dadState is associated with. + done *bool +} + +// defaultRouterState holds data associated with a default router discovered by +// a Router Advertisement (RA). +type defaultRouterState struct { + invalidationTimer *time.Timer + + // Used to inform the timer not to invalidate the default router (R) in + // a race condition (T1 is a goroutine that handles an RA from R and T2 + // is the goroutine that handles R's invalidation timer firing): + // T1: Receive a new RA from R + // T1: Obtain the NIC's lock before processing the RA + // T2: R's invalidation timer fires, and gets blocked on obtaining the + // NIC's lock + // T1: Refreshes/extends R's lifetime & releases NIC's lock + // T2: Obtains NIC's lock & invalidates R immediately + // + // To resolve this, T1 will check to see if the timer already fired, and + // inform the timer using doNotInvalidate to not invalidate R, so that + // once T2 obtains the lock, it will see that it is set to true and do + // nothing further. + doNotInvalidate *bool +} + +// onLinkPrefixState holds data associated with an on-link prefix discovered by +// a Router Advertisement's Prefix Information option (PI) when the NDP +// configurations was configured to do so. +type onLinkPrefixState struct { + invalidationTimer *time.Timer + + // Used to signal the timer not to invalidate the on-link prefix (P) in + // a race condition (T1 is a goroutine that handles a PI for P and T2 + // is the goroutine that handles P's invalidation timer firing): + // T1: Receive a new PI for P + // T1: Obtain the NIC's lock before processing the PI + // T2: P's invalidation timer fires, and gets blocked on obtaining the + // NIC's lock + // T1: Refreshes/extends P's lifetime & releases NIC's lock + // T2: Obtains NIC's lock & invalidates P immediately + // + // To resolve this, T1 will check to see if the timer already fired, and + // inform the timer using doNotInvalidate to not invalidate P, so that + // once T2 obtains the lock, it will see that it is set to true and do + // nothing further. + doNotInvalidate *bool +} + +// autoGenAddressState holds data associated with an address generated via +// SLAAC. +type autoGenAddressState struct { + invalidationTimer *time.Timer + + // Used to signal the timer not to invalidate the SLAAC address (A) in + // a race condition (T1 is a goroutine that handles a PI for A and T2 + // is the goroutine that handles A's invalidation timer firing): + // T1: Receive a new PI for A + // T1: Obtain the NIC's lock before processing the PI + // T2: A's invalidation timer fires, and gets blocked on obtaining the + // NIC's lock + // T1: Refreshes/extends A's lifetime & releases NIC's lock + // T2: Obtains NIC's lock & invalidates A immediately + // + // To resolve this, T1 will check to see if the timer already fired, and + // inform the timer using doNotInvalidate to not invalidate A, so that + // once T2 obtains the lock, it will see that it is set to true and do + // nothing further. + doNotInvalidate *bool + + // Nonzero only when the address is not valid forever (invalidationTimer + // is not nil). + validUntil time.Time +} + +// startDuplicateAddressDetection performs Duplicate Address Detection. +// +// This function must only be called by IPv6 addresses that are currently +// tentative. +// +// The NIC that ndp belongs to MUST be locked. +func (ndp *ndpState) startDuplicateAddressDetection(addr tcpip.Address, ref *referencedNetworkEndpoint) *tcpip.Error { + // addr must be a valid unicast IPv6 address. + if !header.IsV6UnicastAddress(addr) { + return tcpip.ErrAddressFamilyNotSupported + } + + // Should not attempt to perform DAD on an address that is currently in + // the DAD process. + if _, ok := ndp.dad[addr]; ok { + // Should never happen because we should only ever call this + // function for newly created addresses. If we attemped to + // "add" an address that already existed, we would returned an + // error since we attempted to add a duplicate address, or its + // reference count would have been increased without doing the + // work that would have been done for an address that was brand + // new. See NIC.addPermanentAddressLocked. + panic(fmt.Sprintf("ndpdad: already performing DAD for addr %s on NIC(%d)", addr, ndp.nic.ID())) + } + + remaining := ndp.configs.DupAddrDetectTransmits + + { + done, err := ndp.doDuplicateAddressDetection(addr, remaining, ref) + if err != nil { + return err + } + if done { + return nil + } + } + + remaining-- + + var done bool + var timer *time.Timer + timer = time.AfterFunc(ndp.configs.RetransmitTimer, func() { + var d bool + var err *tcpip.Error + + // doDadIteration does a single iteration of the DAD loop. + // + // Returns true if the integrator needs to be informed of DAD + // completing. + doDadIteration := func() bool { + ndp.nic.mu.Lock() + defer ndp.nic.mu.Unlock() + + if done { + // If we reach this point, it means that the DAD + // timer fired after another goroutine already + // obtained the NIC lock and stopped DAD before + // this function obtained the NIC lock. Simply + // return here and do nothing further. + return false + } + + ref, ok := ndp.nic.endpoints[NetworkEndpointID{addr}] + if !ok { + // This should never happen. + // We should have an endpoint for addr since we + // are still performing DAD on it. If the + // endpoint does not exist, but we are doing DAD + // on it, then we started DAD at some point, but + // forgot to stop it when the endpoint was + // deleted. + panic(fmt.Sprintf("ndpdad: unrecognized addr %s for NIC(%d)", addr, ndp.nic.ID())) + } + + d, err = ndp.doDuplicateAddressDetection(addr, remaining, ref) + if err != nil || d { + delete(ndp.dad, addr) + + if err != nil { + log.Printf("ndpdad: Error occured during DAD iteration for addr (%s) on NIC(%d); err = %s", addr, ndp.nic.ID(), err) + } + + // Let the integrator know DAD has completed. + return true + } + + remaining-- + timer.Reset(ndp.nic.stack.ndpConfigs.RetransmitTimer) + return false + } + + if doDadIteration() && ndp.nic.stack.ndpDisp != nil { + ndp.nic.stack.ndpDisp.OnDuplicateAddressDetectionStatus(ndp.nic.ID(), addr, d, err) + } + }) + + ndp.dad[addr] = dadState{ + timer: timer, + done: &done, + } + + return nil +} + +// doDuplicateAddressDetection is called on every iteration of the timer, and +// when DAD starts. +// +// It handles resolving the address (if there are no more NS to send), or +// sending the next NS if there are more NS to send. +// +// This function must only be called by IPv6 addresses that are currently +// tentative. +// +// The NIC that ndp belongs to (n) MUST be locked. +// +// Returns true if DAD has resolved; false if DAD is still ongoing. +func (ndp *ndpState) doDuplicateAddressDetection(addr tcpip.Address, remaining uint8, ref *referencedNetworkEndpoint) (bool, *tcpip.Error) { + if ref.getKind() != permanentTentative { + // The endpoint should still be marked as tentative + // since we are still performing DAD on it. + panic(fmt.Sprintf("ndpdad: addr %s is not tentative on NIC(%d)", addr, ndp.nic.ID())) + } + + if remaining == 0 { + // DAD has resolved. + ref.setKind(permanent) + return true, nil + } + + // Send a new NS. + snmc := header.SolicitedNodeAddr(addr) + snmcRef, ok := ndp.nic.endpoints[NetworkEndpointID{snmc}] + if !ok { + // This should never happen as if we have the + // address, we should have the solicited-node + // address. + panic(fmt.Sprintf("ndpdad: NIC(%d) is not in the solicited-node multicast group (%s) but it has addr %s", ndp.nic.ID(), snmc, addr)) + } + + // Use the unspecified address as the source address when performing + // DAD. + r := makeRoute(header.IPv6ProtocolNumber, header.IPv6Any, snmc, ndp.nic.linkEP.LinkAddress(), snmcRef, false, false) + + hdr := buffer.NewPrependable(int(r.MaxHeaderLength()) + header.ICMPv6NeighborSolicitMinimumSize) + pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6NeighborSolicitMinimumSize)) + pkt.SetType(header.ICMPv6NeighborSolicit) + ns := header.NDPNeighborSolicit(pkt.NDPPayload()) + ns.SetTargetAddress(addr) + pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, buffer.VectorisedView{})) + + sent := r.Stats().ICMP.V6PacketsSent + if err := r.WritePacket(nil, NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: header.NDPHopLimit, TOS: DefaultTOS}, tcpip.PacketBuffer{ + Header: hdr, + }); err != nil { + sent.Dropped.Increment() + return false, err + } + sent.NeighborSolicit.Increment() + + return false, nil +} + +// stopDuplicateAddressDetection ends a running Duplicate Address Detection +// process. Note, this may leave the DAD process for a tentative address in +// such a state forever, unless some other external event resolves the DAD +// process (receiving an NA from the true owner of addr, or an NS for addr +// (implying another node is attempting to use addr)). It is up to the caller +// of this function to handle such a scenario. Normally, addr will be removed +// from n right after this function returns or the address successfully +// resolved. +// +// The NIC that ndp belongs to MUST be locked. +func (ndp *ndpState) stopDuplicateAddressDetection(addr tcpip.Address) { + dad, ok := ndp.dad[addr] + if !ok { + // Not currently performing DAD on addr, just return. + return + } + + if dad.timer != nil { + dad.timer.Stop() + dad.timer = nil + + *dad.done = true + dad.done = nil + } + + delete(ndp.dad, addr) + + // Let the integrator know DAD did not resolve. + if ndp.nic.stack.ndpDisp != nil { + go ndp.nic.stack.ndpDisp.OnDuplicateAddressDetectionStatus(ndp.nic.ID(), addr, false, nil) + } +} + +// handleRA handles a Router Advertisement message that arrived on the NIC +// this ndp is for. Does nothing if the NIC is configured to not handle RAs. +// +// The NIC that ndp belongs to and its associated stack MUST be locked. +func (ndp *ndpState) handleRA(ip tcpip.Address, ra header.NDPRouterAdvert) { + // Is the NIC configured to handle RAs at all? + // + // Currently, the stack does not determine router interface status on a + // per-interface basis; it is a stack-wide configuration, so we check + // stack's forwarding flag to determine if the NIC is a routing + // interface. + if !ndp.configs.HandleRAs || ndp.nic.stack.forwarding { + return + } + + // Is the NIC configured to discover default routers? + if ndp.configs.DiscoverDefaultRouters { + rtr, ok := ndp.defaultRouters[ip] + rl := ra.RouterLifetime() + switch { + case !ok && rl != 0: + // This is a new default router we are discovering. + // + // Only remember it if we currently know about less than + // MaxDiscoveredDefaultRouters routers. + if len(ndp.defaultRouters) < MaxDiscoveredDefaultRouters { + ndp.rememberDefaultRouter(ip, rl) + } + + case ok && rl != 0: + // This is an already discovered default router. Update + // the invalidation timer. + timer := rtr.invalidationTimer + + // We should ALWAYS have an invalidation timer for a + // discovered router. + if timer == nil { + panic("ndphandlera: RA invalidation timer should not be nil") + } + + if !timer.Stop() { + // If we reach this point, then we know the + // timer fired after we already took the NIC + // lock. Inform the timer not to invalidate the + // router when it obtains the lock as we just + // got a new RA that refreshes its lifetime to a + // non-zero value. See + // defaultRouterState.doNotInvalidate for more + // details. + *rtr.doNotInvalidate = true + } + + timer.Reset(rl) + + case ok && rl == 0: + // We know about the router but it is no longer to be + // used as a default router so invalidate it. + ndp.invalidateDefaultRouter(ip) + } + } + + // TODO(b/141556115): Do (RetransTimer, ReachableTime)) Parameter + // Discovery. + + // We know the options is valid as far as wire format is concerned since + // we got the Router Advertisement, as documented by this fn. Given this + // we do not check the iterator for errors on calls to Next. + it, _ := ra.Options().Iter(false) + for opt, done, _ := it.Next(); !done; opt, done, _ = it.Next() { + switch opt := opt.(type) { + case header.NDPRecursiveDNSServer: + if ndp.nic.stack.ndpDisp == nil { + continue + } + + ndp.nic.stack.ndpDisp.OnRecursiveDNSServerOption(ndp.nic.ID(), opt.Addresses(), opt.Lifetime()) + + case header.NDPPrefixInformation: + prefix := opt.Subnet() + + // Is the prefix a link-local? + if header.IsV6LinkLocalAddress(prefix.ID()) { + // ...Yes, skip as per RFC 4861 section 6.3.4, + // and RFC 4862 section 5.5.3.b (for SLAAC). + continue + } + + // Is the Prefix Length 0? + if prefix.Prefix() == 0 { + // ...Yes, skip as this is an invalid prefix + // as all IPv6 addresses cannot be on-link. + continue + } + + if opt.OnLinkFlag() { + ndp.handleOnLinkPrefixInformation(opt) + } + + if opt.AutonomousAddressConfigurationFlag() { + ndp.handleAutonomousPrefixInformation(opt) + } + } + + // TODO(b/141556115): Do (MTU) Parameter Discovery. + } +} + +// invalidateDefaultRouter invalidates a discovered default router. +// +// The NIC that ndp belongs to MUST be locked. +func (ndp *ndpState) invalidateDefaultRouter(ip tcpip.Address) { + rtr, ok := ndp.defaultRouters[ip] + + // Is the router still discovered? + if !ok { + // ...Nope, do nothing further. + return + } + + rtr.invalidationTimer.Stop() + rtr.invalidationTimer = nil + *rtr.doNotInvalidate = true + rtr.doNotInvalidate = nil + + delete(ndp.defaultRouters, ip) + + // Let the integrator know a discovered default router is invalidated. + if ndpDisp := ndp.nic.stack.ndpDisp; ndpDisp != nil { + ndpDisp.OnDefaultRouterInvalidated(ndp.nic.ID(), ip) + } +} + +// rememberDefaultRouter remembers a newly discovered default router with IPv6 +// link-local address ip with lifetime rl. +// +// The router identified by ip MUST NOT already be known by the NIC. +// +// The NIC that ndp belongs to MUST be locked. +func (ndp *ndpState) rememberDefaultRouter(ip tcpip.Address, rl time.Duration) { + ndpDisp := ndp.nic.stack.ndpDisp + if ndpDisp == nil { + return + } + + // Inform the integrator when we discovered a default router. + if !ndpDisp.OnDefaultRouterDiscovered(ndp.nic.ID(), ip) { + // Informed by the integrator to not remember the router, do + // nothing further. + return + } + + // Used to signal the timer not to invalidate the default router (R) in + // a race condition. See defaultRouterState.doNotInvalidate for more + // details. + var doNotInvalidate bool + + ndp.defaultRouters[ip] = defaultRouterState{ + invalidationTimer: time.AfterFunc(rl, func() { + ndp.nic.stack.mu.Lock() + defer ndp.nic.stack.mu.Unlock() + ndp.nic.mu.Lock() + defer ndp.nic.mu.Unlock() + + if doNotInvalidate { + doNotInvalidate = false + return + } + + ndp.invalidateDefaultRouter(ip) + }), + doNotInvalidate: &doNotInvalidate, + } +} + +// rememberOnLinkPrefix remembers a newly discovered on-link prefix with IPv6 +// address with prefix prefix with lifetime l. +// +// The prefix identified by prefix MUST NOT already be known. +// +// The NIC that ndp belongs to MUST be locked. +func (ndp *ndpState) rememberOnLinkPrefix(prefix tcpip.Subnet, l time.Duration) { + ndpDisp := ndp.nic.stack.ndpDisp + if ndpDisp == nil { + return + } + + // Inform the integrator when we discovered an on-link prefix. + if !ndpDisp.OnOnLinkPrefixDiscovered(ndp.nic.ID(), prefix) { + // Informed by the integrator to not remember the prefix, do + // nothing further. + return + } + + // Used to signal the timer not to invalidate the on-link prefix (P) in + // a race condition. See onLinkPrefixState.doNotInvalidate for more + // details. + var doNotInvalidate bool + var timer *time.Timer + + // Only create a timer if the lifetime is not infinite. + if l < header.NDPInfiniteLifetime { + timer = ndp.prefixInvalidationCallback(prefix, l, &doNotInvalidate) + } + + ndp.onLinkPrefixes[prefix] = onLinkPrefixState{ + invalidationTimer: timer, + doNotInvalidate: &doNotInvalidate, + } +} + +// invalidateOnLinkPrefix invalidates a discovered on-link prefix. +// +// The NIC that ndp belongs to MUST be locked. +func (ndp *ndpState) invalidateOnLinkPrefix(prefix tcpip.Subnet) { + s, ok := ndp.onLinkPrefixes[prefix] + + // Is the on-link prefix still discovered? + if !ok { + // ...Nope, do nothing further. + return + } + + if s.invalidationTimer != nil { + s.invalidationTimer.Stop() + s.invalidationTimer = nil + *s.doNotInvalidate = true + } + + s.doNotInvalidate = nil + + delete(ndp.onLinkPrefixes, prefix) + + // Let the integrator know a discovered on-link prefix is invalidated. + if ndpDisp := ndp.nic.stack.ndpDisp; ndpDisp != nil { + ndpDisp.OnOnLinkPrefixInvalidated(ndp.nic.ID(), prefix) + } +} + +// prefixInvalidationCallback returns a new on-link prefix invalidation timer +// for prefix that fires after vl. +// +// doNotInvalidate is used to signal the timer when it fires at the same time +// that a prefix's valid lifetime gets refreshed. See +// onLinkPrefixState.doNotInvalidate for more details. +func (ndp *ndpState) prefixInvalidationCallback(prefix tcpip.Subnet, vl time.Duration, doNotInvalidate *bool) *time.Timer { + return time.AfterFunc(vl, func() { + ndp.nic.stack.mu.Lock() + defer ndp.nic.stack.mu.Unlock() + ndp.nic.mu.Lock() + defer ndp.nic.mu.Unlock() + + if *doNotInvalidate { + *doNotInvalidate = false + return + } + + ndp.invalidateOnLinkPrefix(prefix) + }) +} + +// handleOnLinkPrefixInformation handles a Prefix Information option with +// its on-link flag set, as per RFC 4861 section 6.3.4. +// +// handleOnLinkPrefixInformation assumes that the prefix this pi is for is +// not the link-local prefix and the on-link flag is set. +// +// The NIC that ndp belongs to MUST be locked. +func (ndp *ndpState) handleOnLinkPrefixInformation(pi header.NDPPrefixInformation) { + prefix := pi.Subnet() + prefixState, ok := ndp.onLinkPrefixes[prefix] + vl := pi.ValidLifetime() + + if !ok && vl == 0 { + // Don't know about this prefix but it has a zero valid + // lifetime, so just ignore. + return + } + + if !ok && vl != 0 { + // This is a new on-link prefix we are discovering + // + // Only remember it if we currently know about less than + // MaxDiscoveredOnLinkPrefixes on-link prefixes. + if ndp.configs.DiscoverOnLinkPrefixes && len(ndp.onLinkPrefixes) < MaxDiscoveredOnLinkPrefixes { + ndp.rememberOnLinkPrefix(prefix, vl) + } + return + } + + if ok && vl == 0 { + // We know about the on-link prefix, but it is + // no longer to be considered on-link, so + // invalidate it. + ndp.invalidateOnLinkPrefix(prefix) + return + } + + // This is an already discovered on-link prefix with a + // new non-zero valid lifetime. + // Update the invalidation timer. + timer := prefixState.invalidationTimer + + if timer == nil && vl >= header.NDPInfiniteLifetime { + // Had infinite valid lifetime before and + // continues to have an invalid lifetime. Do + // nothing further. + return + } + + if timer != nil && !timer.Stop() { + // If we reach this point, then we know the timer alread fired + // after we took the NIC lock. Inform the timer to not + // invalidate the prefix once it obtains the lock as we just + // got a new PI that refreshes its lifetime to a non-zero value. + // See onLinkPrefixState.doNotInvalidate for more details. + *prefixState.doNotInvalidate = true + } + + if vl >= header.NDPInfiniteLifetime { + // Prefix is now valid forever so we don't need + // an invalidation timer. + prefixState.invalidationTimer = nil + ndp.onLinkPrefixes[prefix] = prefixState + return + } + + if timer != nil { + // We already have a timer so just reset it to + // expire after the new valid lifetime. + timer.Reset(vl) + return + } + + // We do not have a timer so just create a new one. + prefixState.invalidationTimer = ndp.prefixInvalidationCallback(prefix, vl, prefixState.doNotInvalidate) + ndp.onLinkPrefixes[prefix] = prefixState +} + +// handleAutonomousPrefixInformation handles a Prefix Information option with +// its autonomous flag set, as per RFC 4862 section 5.5.3. +// +// handleAutonomousPrefixInformation assumes that the prefix this pi is for is +// not the link-local prefix and the autonomous flag is set. +// +// The NIC that ndp belongs to and its associated stack MUST be locked. +func (ndp *ndpState) handleAutonomousPrefixInformation(pi header.NDPPrefixInformation) { + vl := pi.ValidLifetime() + pl := pi.PreferredLifetime() + + // If the preferred lifetime is greater than the valid lifetime, + // silently ignore the Prefix Information option, as per RFC 4862 + // section 5.5.3.c. + if pl > vl { + return + } + + prefix := pi.Subnet() + + // Check if we already have an auto-generated address for prefix. + for _, ref := range ndp.nic.endpoints { + if ref.protocol != header.IPv6ProtocolNumber { + continue + } + + if ref.configType != slaac { + continue + } + + addr := ref.ep.ID().LocalAddress + refAddrWithPrefix := tcpip.AddressWithPrefix{Address: addr, PrefixLen: ref.ep.PrefixLen()} + if refAddrWithPrefix.Subnet() != prefix { + continue + } + + // + // At this point, we know we are refreshing a SLAAC generated + // IPv6 address with the prefix, prefix. Do the work as outlined + // by RFC 4862 section 5.5.3.e. + // + + addrState, ok := ndp.autoGenAddresses[addr] + if !ok { + panic(fmt.Sprintf("must have an autoGenAddressess entry for the SLAAC generated IPv6 address %s", addr)) + } + + // TODO(b/143713887): Handle deprecating auto-generated address + // after the preferred lifetime. + + // As per RFC 4862 section 5.5.3.e, the valid lifetime of the + // address generated by SLAAC is as follows: + // + // 1) If the received Valid Lifetime is greater than 2 hours or + // greater than RemainingLifetime, set the valid lifetime of + // the address to the advertised Valid Lifetime. + // + // 2) If RemainingLifetime is less than or equal to 2 hours, + // ignore the advertised Valid Lifetime. + // + // 3) Otherwise, reset the valid lifetime of the address to 2 + // hours. + + // Handle the infinite valid lifetime separately as we do not + // keep a timer in this case. + if vl >= header.NDPInfiniteLifetime { + if addrState.invalidationTimer != nil { + // Valid lifetime was finite before, but now it + // is valid forever. + if !addrState.invalidationTimer.Stop() { + *addrState.doNotInvalidate = true + } + addrState.invalidationTimer = nil + addrState.validUntil = time.Time{} + ndp.autoGenAddresses[addr] = addrState + } + + return + } + + var effectiveVl time.Duration + var rl time.Duration + + // If the address was originally set to be valid forever, + // assume the remaining time to be the maximum possible value. + if addrState.invalidationTimer == nil { + rl = header.NDPInfiniteLifetime + } else { + rl = time.Until(addrState.validUntil) + } + + if vl > MinPrefixInformationValidLifetimeForUpdate || vl > rl { + effectiveVl = vl + } else if rl <= MinPrefixInformationValidLifetimeForUpdate { + ndp.autoGenAddresses[addr] = addrState + return + } else { + effectiveVl = MinPrefixInformationValidLifetimeForUpdate + } + + if addrState.invalidationTimer == nil { + addrState.invalidationTimer = ndp.autoGenAddrInvalidationTimer(addr, effectiveVl, addrState.doNotInvalidate) + } else { + if !addrState.invalidationTimer.Stop() { + *addrState.doNotInvalidate = true + } + addrState.invalidationTimer.Reset(effectiveVl) + } + + addrState.validUntil = time.Now().Add(effectiveVl) + ndp.autoGenAddresses[addr] = addrState + return + } + + // We do not already have an address within the prefix, prefix. Do the + // work as outlined by RFC 4862 section 5.5.3.d if n is configured + // to auto-generated global addresses by SLAAC. + + // Are we configured to auto-generate new global addresses? + if !ndp.configs.AutoGenGlobalAddresses { + return + } + + // If we do not already have an address for this prefix and the valid + // lifetime is 0, no need to do anything further, as per RFC 4862 + // section 5.5.3.d. + if vl == 0 { + return + } + + // Make sure the prefix is valid (as far as its length is concerned) to + // generate a valid IPv6 address from an interface identifier (IID), as + // per RFC 4862 sectiion 5.5.3.d. + if prefix.Prefix() != validPrefixLenForAutoGen { + return + } + + // Only attempt to generate an interface-specific IID if we have a valid + // link address. + // + // TODO(b/141011931): Validate a LinkEndpoint's link address + // (provided by LinkEndpoint.LinkAddress) before reaching this + // point. + linkAddr := ndp.nic.linkEP.LinkAddress() + if !header.IsValidUnicastEthernetAddress(linkAddr) { + return + } + + // Generate an address within prefix from the modified EUI-64 of ndp's + // NIC's Ethernet MAC address. + addrBytes := make([]byte, header.IPv6AddressSize) + copy(addrBytes[:header.IIDOffsetInIPv6Address], prefix.ID()[:header.IIDOffsetInIPv6Address]) + header.EthernetAdddressToModifiedEUI64IntoBuf(linkAddr, addrBytes[header.IIDOffsetInIPv6Address:]) + addr := tcpip.Address(addrBytes) + addrWithPrefix := tcpip.AddressWithPrefix{ + Address: addr, + PrefixLen: validPrefixLenForAutoGen, + } + + // If the nic already has this address, do nothing further. + if ndp.nic.hasPermanentAddrLocked(addr) { + return + } + + // Inform the integrator that we have a new SLAAC address. + ndpDisp := ndp.nic.stack.ndpDisp + if ndpDisp == nil { + return + } + if !ndpDisp.OnAutoGenAddress(ndp.nic.ID(), addrWithPrefix) { + // Informed by the integrator not to add the address. + return + } + + if _, err := ndp.nic.addAddressLocked(tcpip.ProtocolAddress{ + Protocol: header.IPv6ProtocolNumber, + AddressWithPrefix: addrWithPrefix, + }, FirstPrimaryEndpoint, permanent, slaac); err != nil { + panic(err) + } + + // Setup the timers to deprecate and invalidate this newly generated + // address. + + // TODO(b/143713887): Handle deprecating auto-generated addresses + // after the preferred lifetime. + + var doNotInvalidate bool + var vTimer *time.Timer + if vl < header.NDPInfiniteLifetime { + vTimer = ndp.autoGenAddrInvalidationTimer(addr, vl, &doNotInvalidate) + } + + ndp.autoGenAddresses[addr] = autoGenAddressState{ + invalidationTimer: vTimer, + doNotInvalidate: &doNotInvalidate, + validUntil: time.Now().Add(vl), + } +} + +// invalidateAutoGenAddress invalidates an auto-generated address. +// +// The NIC that ndp belongs to MUST be locked. +func (ndp *ndpState) invalidateAutoGenAddress(addr tcpip.Address) { + if !ndp.cleanupAutoGenAddrResourcesAndNotify(addr) { + return + } + + ndp.nic.removePermanentAddressLocked(addr) +} + +// cleanupAutoGenAddrResourcesAndNotify cleans up an invalidated auto-generated +// address's resources from ndp. If the stack has an NDP dispatcher, it will +// be notified that addr has been invalidated. +// +// Returns true if ndp had resources for addr to cleanup. +// +// The NIC that ndp belongs to MUST be locked. +func (ndp *ndpState) cleanupAutoGenAddrResourcesAndNotify(addr tcpip.Address) bool { + state, ok := ndp.autoGenAddresses[addr] + + if !ok { + return false + } + + if state.invalidationTimer != nil { + state.invalidationTimer.Stop() + state.invalidationTimer = nil + *state.doNotInvalidate = true + } + + state.doNotInvalidate = nil + + delete(ndp.autoGenAddresses, addr) + + if ndpDisp := ndp.nic.stack.ndpDisp; ndpDisp != nil { + ndpDisp.OnAutoGenAddressInvalidated(ndp.nic.ID(), tcpip.AddressWithPrefix{ + Address: addr, + PrefixLen: validPrefixLenForAutoGen, + }) + } + + return true +} + +// autoGenAddrInvalidationTimer returns a new invalidation timer for an +// auto-generated address that fires after vl. +// +// doNotInvalidate is used to inform the timer when it fires at the same time +// that an auto-generated address's valid lifetime gets refreshed. See +// autoGenAddrState.doNotInvalidate for more details. +func (ndp *ndpState) autoGenAddrInvalidationTimer(addr tcpip.Address, vl time.Duration, doNotInvalidate *bool) *time.Timer { + return time.AfterFunc(vl, func() { + ndp.nic.mu.Lock() + defer ndp.nic.mu.Unlock() + + if *doNotInvalidate { + *doNotInvalidate = false + return + } + + ndp.invalidateAutoGenAddress(addr) + }) +} |