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// Copyright 2018 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/eventfd"
"gvisor.dev/gvisor/pkg/tcpip/link/sharedmem/queue"
)
// rx holds all state associated with an rx queue.
type rx struct {
data []byte
sharedData []byte
q queue.Rx
eventFD eventfd.Eventfd
}
// init initializes all state needed by the rx 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 (r *rx) init(mtu uint32, c *QueueConfig) error {
// Map in all buffers.
txPipe, err := getBuffer(c.TxPipeFD)
if err != nil {
return err
}
rxPipe, err := getBuffer(c.RxPipeFD)
if err != nil {
unix.Munmap(txPipe)
return err
}
data, err := getBuffer(c.DataFD)
if err != nil {
unix.Munmap(txPipe)
unix.Munmap(rxPipe)
return err
}
sharedData, err := getBuffer(c.SharedDataFD)
if err != nil {
unix.Munmap(txPipe)
unix.Munmap(rxPipe)
unix.Munmap(data)
return err
}
// Duplicate the eventFD so that caller can close it but we can still
// use it.
efd, err := c.EventFD.Dup()
if err != nil {
unix.Munmap(txPipe)
unix.Munmap(rxPipe)
unix.Munmap(data)
unix.Munmap(sharedData)
return err
}
// Initialize state based on buffers.
r.q.Init(txPipe, rxPipe, sharedDataPointer(sharedData))
r.data = data
r.eventFD = efd
r.sharedData = sharedData
return nil
}
// cleanup releases all resources allocated during init() except r.eventFD. It
// must only be called if init() has previously succeeded.
func (r *rx) cleanup() {
a, b := r.q.Bytes()
unix.Munmap(a)
unix.Munmap(b)
unix.Munmap(r.data)
unix.Munmap(r.sharedData)
}
// notify writes to the tx.eventFD to indicate to the peer that there is data to
// be read.
func (r *rx) notify() {
r.eventFD.Notify()
}
// postAndReceive posts the provided buffers (if any), and then tries to read
// from the receive queue.
//
// Capacity permitting, it reuses the posted buffer slice to store the buffers
// that were read as well.
//
// This function will block if there aren't any available packets.
func (r *rx) postAndReceive(b []queue.RxBuffer, stopRequested *atomicbitops.Uint32) ([]queue.RxBuffer, uint32) {
// Post the buffers first. If we cannot post, sleep until we can. We
// never post more than will fit concurrently, so it's safe to wait
// until enough room is available.
if len(b) != 0 && !r.q.PostBuffers(b) {
r.q.EnableNotification()
for !r.q.PostBuffers(b) {
r.eventFD.Wait()
if stopRequested.Load() != 0 {
r.q.DisableNotification()
return nil, 0
}
}
r.q.DisableNotification()
}
// Read the next set of descriptors.
b, n := r.q.Dequeue(b[:0])
if len(b) != 0 {
return b, n
}
// Data isn't immediately available. Enable eventfd notifications.
r.q.EnableNotification()
for {
b, n = r.q.Dequeue(b)
if len(b) != 0 {
break
}
// Wait for notification.
r.eventFD.Wait()
if stopRequested.Load() != 0 {
r.q.DisableNotification()
return nil, 0
}
}
r.q.DisableNotification()
return b, n
}
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