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// Copyright 2021 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.
//go:build linux
// +build linux
package sharedmem
import (
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/atomicbitops"
"gvisor.dev/gvisor/pkg/buffer"
"gvisor.dev/gvisor/pkg/cleanup"
"gvisor.dev/gvisor/pkg/eventfd"
"gvisor.dev/gvisor/pkg/tcpip/link/sharedmem/pipe"
"gvisor.dev/gvisor/pkg/tcpip/link/sharedmem/queue"
)
type serverRx struct {
// packetPipe represents the receive end of the pipe that carries the packet
// descriptors sent by the client.
packetPipe pipe.Rx
// completionPipe represents the transmit end of the pipe that will carry
// completion notifications from the server to the client.
completionPipe pipe.Tx
// data represents the buffer area where the packet payload is held.
data []byte
// eventFD is used to notify the peer when transmission is completed.
eventFD eventfd.Eventfd
// sharedData the memory region to use to enable/disable notifications.
sharedData []byte
// sharedEventFDState is the memory region in sharedData used to enable
// disable notifications on eventFD.
sharedEventFDState *atomicbitops.Uint32
}
// init initializes all state needed by the serverTx queue based on the
// information provided.
//
// The caller always retains ownership of all file descriptors passed in. The
// queue implementation will duplicate any that it may need in the future.
func (s *serverRx) init(c *QueueConfig) error {
// Map in all buffers.
packetPipeMem, err := getBuffer(c.TxPipeFD)
if err != nil {
return err
}
cu := cleanup.Make(func() { unix.Munmap(packetPipeMem) })
defer cu.Clean()
completionPipeMem, err := getBuffer(c.RxPipeFD)
if err != nil {
return err
}
cu.Add(func() { unix.Munmap(completionPipeMem) })
data, err := getBuffer(c.DataFD)
if err != nil {
return err
}
cu.Add(func() { unix.Munmap(data) })
sharedData, err := getBuffer(c.SharedDataFD)
if err != nil {
return err
}
cu.Add(func() { unix.Munmap(sharedData) })
// Duplicate the eventFD so that caller can close it but we can still
// use it.
efd, err := c.EventFD.Dup()
if err != nil {
return err
}
cu.Add(func() { efd.Close() })
s.packetPipe.Init(packetPipeMem)
s.completionPipe.Init(completionPipeMem)
s.data = data
s.eventFD = efd
s.sharedData = sharedData
s.sharedEventFDState = sharedDataPointer(sharedData)
cu.Release()
return nil
}
func (s *serverRx) cleanup() {
unix.Munmap(s.packetPipe.Bytes())
unix.Munmap(s.completionPipe.Bytes())
unix.Munmap(s.data)
unix.Munmap(s.sharedData)
s.eventFD.Close()
}
// EnableNotification updates the shared state such that the peer will notify
// the eventfd when there are packets to be dequeued.
func (s *serverRx) EnableNotification() {
s.sharedEventFDState.Store(queue.EventFDEnabled)
}
// DisableNotification updates the shared state such that the peer will not
// notify the eventfd.
func (s *serverRx) DisableNotification() {
s.sharedEventFDState.Store(queue.EventFDDisabled)
}
// completionNotificationSize is size in bytes of a completion notification sent
// on the completion queue after a transmitted packet has been handled.
const completionNotificationSize = 8
// receive receives a single packet from the packetPipe.
func (s *serverRx) receive() *buffer.View {
desc := s.packetPipe.Pull()
if desc == nil {
return nil
}
pktInfo := queue.DecodeTxPacketHeader(desc)
contents := buffer.NewView(int(pktInfo.Size))
toCopy := pktInfo.Size
for i := 0; i < pktInfo.BufferCount; i++ {
txBuf := queue.DecodeTxBufferHeader(desc, i)
if txBuf.Size <= toCopy {
contents.Write(s.data[txBuf.Offset:][:txBuf.Size])
toCopy -= txBuf.Size
continue
}
contents.Write(s.data[txBuf.Offset:][:toCopy])
break
}
// Flush to let peer know that slots queued for transmission have been handled
// and its free to reuse the slots.
s.packetPipe.Flush()
// Encode packet completion.
b := s.completionPipe.Push(completionNotificationSize)
queue.EncodeTxCompletion(b, pktInfo.ID)
s.completionPipe.Flush()
return contents
}
func (s *serverRx) waitForPackets() {
s.eventFD.Wait()
}
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