| // 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 { |
| route *Route |
| proto tcpip.NetworkProtocolNumber |
| pkt *PacketBuffer |
| } |
| |
| // packetsPendingLinkResolution is a queue of packets pending link resolution. |
| // |
| // Once link resolution completes successfully, the packets will be written. |
| type packetsPendingLinkResolution struct { |
| sync.Mutex |
| |
| // The packets to send once the resolver completes. |
| packets map[<-chan struct{}][]pendingPacket |
| |
| // FIFO of channels used to cancel the oldest goroutine waiting for |
| // link-address resolution. |
| cancelChans []chan struct{} |
| } |
| |
| func (f *packetsPendingLinkResolution) init() { |
| f.Lock() |
| defer f.Unlock() |
| f.packets = make(map[<-chan struct{}][]pendingPacket) |
| } |
| |
| func (f *packetsPendingLinkResolution) enqueue(ch <-chan struct{}, r *Route, proto tcpip.NetworkProtocolNumber, pkt *PacketBuffer) { |
| f.Lock() |
| defer f.Unlock() |
| |
| packets, ok := f.packets[ch] |
| if len(packets) == maxPendingPacketsPerResolution { |
| p := packets[0] |
| packets[0] = pendingPacket{} |
| packets = packets[1:] |
| p.route.Stats().IP.OutgoingPacketErrors.Increment() |
| p.route.Release() |
| } |
| |
| if l := len(packets); l >= maxPendingPacketsPerResolution { |
| panic(fmt.Sprintf("max pending packets for resolution reached; got %d packets, max = %d", l, maxPendingPacketsPerResolution)) |
| } |
| |
| f.packets[ch] = append(packets, pendingPacket{ |
| route: r, |
| proto: proto, |
| pkt: pkt, |
| }) |
| |
| if ok { |
| return |
| } |
| |
| // Wait for the link-address resolution to complete. |
| cancel := f.newCancelChannelLocked() |
| go func() { |
| cancelled := false |
| select { |
| case <-ch: |
| case <-cancel: |
| cancelled = true |
| } |
| |
| f.Lock() |
| packets, ok := f.packets[ch] |
| delete(f.packets, ch) |
| f.Unlock() |
| |
| if !ok { |
| panic(fmt.Sprintf("link-resolution goroutine woke up but no entry exists in the queue of packets")) |
| } |
| |
| for _, p := range packets { |
| if cancelled || p.route.IsResolutionRequired() { |
| p.route.Stats().IP.OutgoingPacketErrors.Increment() |
| |
| if linkResolvableEP, ok := p.route.outgoingNIC.getNetworkEndpoint(p.route.NetProto).(LinkResolvableNetworkEndpoint); ok { |
| linkResolvableEP.HandleLinkResolutionFailure(pkt) |
| } |
| } else { |
| p.route.outgoingNIC.writePacket(p.route.Fields(), nil /* gso */, p.proto, p.pkt) |
| } |
| p.route.Release() |
| } |
| }() |
| } |
| |
| // newCancelChannel creates a channel that can cancel a pending forwarding |
| // activity. The oldest channel is closed if the number of open channels would |
| // exceed maxPendingResolutions. |
| func (f *packetsPendingLinkResolution) newCancelChannelLocked() chan struct{} { |
| if len(f.cancelChans) == maxPendingResolutions { |
| ch := f.cancelChans[0] |
| f.cancelChans[0] = nil |
| f.cancelChans = f.cancelChans[1:] |
| close(ch) |
| } |
| if l := len(f.cancelChans); l >= maxPendingResolutions { |
| panic(fmt.Sprintf("max pending resolutions reached; got %d active resolutions, max = %d", l, maxPendingResolutions)) |
| } |
| |
| ch := make(chan struct{}) |
| f.cancelChans = append(f.cancelChans, ch) |
| return ch |
| } |