| // Copyright 2020 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" |
| |
| "gvisor.dev/gvisor/pkg/sync" |
| "gvisor.dev/gvisor/pkg/tcpip" |
| ) |
| |
| const ( |
| // maxPendingResolutions is the maximum number of pending link-address |
| // resolutions. |
| maxPendingResolutions = 64 |
| maxPendingPacketsPerResolution = 256 |
| ) |
| |
| type pendingPacket struct { |
| routeInfo RouteInfo |
| pkt *PacketBuffer |
| } |
| |
| // packetsPendingLinkResolution is a queue of packets pending link resolution. |
| // |
| // Once link resolution completes successfully, the packets will be written. |
| type packetsPendingLinkResolution struct { |
| nic *nic |
| |
| mu struct { |
| sync.Mutex |
| |
| // The packets to send once the resolver completes. |
| // |
| // The link resolution channel is used as the key for this map. |
| packets map[<-chan struct{}][]pendingPacket |
| |
| // FIFO of channels used to cancel the oldest goroutine waiting for |
| // link-address resolution. |
| // |
| // cancelChans holds the same channels that are used as keys to packets. |
| cancelChans []<-chan struct{} |
| } |
| } |
| |
| func (f *packetsPendingLinkResolution) incrementOutgoingPacketErrors(pkt *PacketBuffer) { |
| f.nic.stack.stats.IP.OutgoingPacketErrors.Increment() |
| |
| if ipEndpointStats, ok := f.nic.getNetworkEndpoint(pkt.NetworkProtocolNumber).Stats().(IPNetworkEndpointStats); ok { |
| ipEndpointStats.IPStats().OutgoingPacketErrors.Increment() |
| } |
| } |
| |
| func (f *packetsPendingLinkResolution) init(nic *nic) { |
| f.mu.Lock() |
| defer f.mu.Unlock() |
| f.nic = nic |
| f.mu.packets = make(map[<-chan struct{}][]pendingPacket) |
| } |
| |
| // cancel drains all pending packet queues and release all packet |
| // references. |
| func (f *packetsPendingLinkResolution) cancel() { |
| f.mu.Lock() |
| defer f.mu.Unlock() |
| for ch, pendingPackets := range f.mu.packets { |
| for _, p := range pendingPackets { |
| p.pkt.DecRef() |
| } |
| delete(f.mu.packets, ch) |
| } |
| f.mu.cancelChans = nil |
| } |
| |
| // dequeue any pending packets associated with ch. |
| // |
| // If err is nil, packets will be written and sent to the given remote link |
| // address. |
| func (f *packetsPendingLinkResolution) dequeue(ch <-chan struct{}, linkAddr tcpip.LinkAddress, err tcpip.Error) { |
| f.mu.Lock() |
| packets, ok := f.mu.packets[ch] |
| delete(f.mu.packets, ch) |
| |
| if ok { |
| for i, cancelChan := range f.mu.cancelChans { |
| if cancelChan == ch { |
| f.mu.cancelChans = append(f.mu.cancelChans[:i], f.mu.cancelChans[i+1:]...) |
| break |
| } |
| } |
| } |
| |
| f.mu.Unlock() |
| |
| if ok { |
| f.dequeuePackets(packets, linkAddr, err) |
| } |
| } |
| |
| // enqueue a packet to be sent once link resolution completes. |
| // |
| // If the maximum number of pending resolutions is reached, the packets |
| // associated with the oldest link resolution will be dequeued as if they failed |
| // link resolution. |
| func (f *packetsPendingLinkResolution) enqueue(r *Route, pkt *PacketBuffer) tcpip.Error { |
| f.mu.Lock() |
| // Make sure we attempt resolution while holding f's lock so that we avoid |
| // a race where link resolution completes before we enqueue the packets. |
| // |
| // A @ T1: Call ResolvedFields (get link resolution channel) |
| // B @ T2: Complete link resolution, dequeue pending packets |
| // C @ T1: Enqueue packet that already completed link resolution (which will |
| // never dequeue) |
| // |
| // To make sure B does not interleave with A and C, we make sure A and C are |
| // done while holding the lock. |
| routeInfo, ch, err := r.resolvedFields(nil) |
| switch err.(type) { |
| case nil: |
| // The route resolved immediately, so we don't need to wait for link |
| // resolution to send the packet. |
| f.mu.Unlock() |
| pkt.EgressRoute = routeInfo |
| return f.nic.writePacket(pkt) |
| case *tcpip.ErrWouldBlock: |
| // We need to wait for link resolution to complete. |
| default: |
| f.mu.Unlock() |
| return err |
| } |
| |
| defer f.mu.Unlock() |
| |
| packets, ok := f.mu.packets[ch] |
| packets = append(packets, pendingPacket{ |
| routeInfo: routeInfo, |
| pkt: pkt, |
| }) |
| pkt.IncRef() |
| |
| if len(packets) > maxPendingPacketsPerResolution { |
| f.incrementOutgoingPacketErrors(packets[0].pkt) |
| packets[0].pkt.DecRef() |
| packets[0] = pendingPacket{} |
| packets = packets[1:] |
| |
| if numPackets := len(packets); numPackets != maxPendingPacketsPerResolution { |
| panic(fmt.Sprintf("holding more queued packets than expected; got = %d, want <= %d", numPackets, maxPendingPacketsPerResolution)) |
| } |
| } |
| |
| f.mu.packets[ch] = packets |
| |
| if ok { |
| return nil |
| } |
| |
| cancelledPackets := f.newCancelChannelLocked(ch) |
| |
| if len(cancelledPackets) != 0 { |
| // Dequeue the pending packets in a new goroutine to not hold up the current |
| // goroutine as handing link resolution failures may be a costly operation. |
| go f.dequeuePackets(cancelledPackets, "" /* linkAddr */, &tcpip.ErrAborted{}) |
| } |
| |
| return nil |
| } |
| |
| // newCancelChannelLocked appends the link resolution channel to a FIFO. If the |
| // maximum number of pending resolutions is reached, the oldest channel will be |
| // removed and its associated pending packets will be returned. |
| func (f *packetsPendingLinkResolution) newCancelChannelLocked(newCH <-chan struct{}) []pendingPacket { |
| f.mu.cancelChans = append(f.mu.cancelChans, newCH) |
| if len(f.mu.cancelChans) <= maxPendingResolutions { |
| return nil |
| } |
| |
| ch := f.mu.cancelChans[0] |
| f.mu.cancelChans[0] = nil |
| f.mu.cancelChans = f.mu.cancelChans[1:] |
| if l := len(f.mu.cancelChans); l > maxPendingResolutions { |
| panic(fmt.Sprintf("max pending resolutions reached; got %d active resolutions, max = %d", l, maxPendingResolutions)) |
| } |
| |
| packets, ok := f.mu.packets[ch] |
| if !ok { |
| panic("must have a packet queue for an uncancelled channel") |
| } |
| delete(f.mu.packets, ch) |
| |
| return packets |
| } |
| |
| func (f *packetsPendingLinkResolution) dequeuePackets(packets []pendingPacket, linkAddr tcpip.LinkAddress, err tcpip.Error) { |
| for _, p := range packets { |
| if err == nil { |
| p.routeInfo.RemoteLinkAddress = linkAddr |
| p.pkt.EgressRoute = p.routeInfo |
| _ = f.nic.writePacket(p.pkt) |
| } else { |
| f.incrementOutgoingPacketErrors(p.pkt) |
| |
| if linkResolvableEP, ok := f.nic.getNetworkEndpoint(p.pkt.NetworkProtocolNumber).(LinkResolvableNetworkEndpoint); ok { |
| linkResolvableEP.HandleLinkResolutionFailure(p.pkt) |
| } |
| } |
| p.pkt.DecRef() |
| } |
| } |