| // 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 { |
| nic *NIC |
| route *Route |
| proto tcpip.NetworkProtocolNumber |
| pkt PacketBuffer |
| } |
| |
| type forwardQueue 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 newForwardQueue() *forwardQueue { |
| return &forwardQueue{packets: make(map[<-chan struct{}][]*pendingPacket)} |
| } |
| |
| func (f *forwardQueue) enqueue(ch <-chan struct{}, n *NIC, r *Route, protocol tcpip.NetworkProtocolNumber, pkt PacketBuffer) { |
| shouldWait := false |
| |
| f.Lock() |
| packets, ok := f.packets[ch] |
| if !ok { |
| shouldWait = true |
| } |
| for len(packets) == maxPendingPacketsPerResolution { |
| p := packets[0] |
| packets = packets[1:] |
| p.nic.stack.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{ |
| nic: n, |
| route: r, |
| proto: protocol, |
| pkt: pkt, |
| }) |
| f.Unlock() |
| |
| if !shouldWait { |
| return |
| } |
| |
| // Wait for the link-address resolution to complete. |
| // Start a goroutine with a forwarding-cancel channel so that we can |
| // limit the maximum number of goroutines running concurrently. |
| cancel := f.newCancelChannel() |
| go func() { |
| cancelled := false |
| select { |
| case <-ch: |
| case <-cancel: |
| cancelled = true |
| } |
| |
| f.Lock() |
| packets := f.packets[ch] |
| delete(f.packets, ch) |
| f.Unlock() |
| |
| for _, p := range packets { |
| if cancelled { |
| p.nic.stack.stats.IP.OutgoingPacketErrors.Increment() |
| } else if _, err := p.route.Resolve(nil); err != nil { |
| p.nic.stack.stats.IP.OutgoingPacketErrors.Increment() |
| } else { |
| p.nic.forwardPacket(p.route, 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 *forwardQueue) newCancelChannel() chan struct{} { |
| f.Lock() |
| defer f.Unlock() |
| |
| if len(f.cancelChans) == maxPendingResolutions { |
| ch := f.cancelChans[0] |
| 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 |
| } |