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endpoint.go
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endpoint.go
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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 xdp provides link layer endpoints backed by AF_XDP sockets.
package xdp
import (
"fmt"
"github.com/MerlinKodo/gvisor/pkg/buffer"
"github.com/MerlinKodo/gvisor/pkg/sync"
"github.com/MerlinKodo/gvisor/pkg/tcpip"
"github.com/MerlinKodo/gvisor/pkg/tcpip/header"
"github.com/MerlinKodo/gvisor/pkg/tcpip/link/qdisc/fifo"
"github.com/MerlinKodo/gvisor/pkg/tcpip/link/rawfile"
"github.com/MerlinKodo/gvisor/pkg/tcpip/link/stopfd"
"github.com/MerlinKodo/gvisor/pkg/tcpip/stack"
"github.com/MerlinKodo/gvisor/pkg/xdp"
"golang.org/x/sys/unix"
)
// TODO(b/240191988): Turn off GSO, GRO, and LRO. Limit veth MTU to 1500.
// MTU is sized to ensure packets fit inside a 2048 byte XDP frame.
const MTU = 1500
var _ stack.LinkEndpoint = (*endpoint)(nil)
type endpoint struct {
// fd is the underlying AF_XDP socket.
fd int
// addr is the address of the endpoint.
addr tcpip.LinkAddress
// caps holds the endpoint capabilities.
caps stack.LinkEndpointCapabilities
// closed is a function to be called when the FD's peer (if any) closes
// its end of the communication pipe.
closed func(tcpip.Error)
mu sync.RWMutex
// +checkloks:mu
networkDispatcher stack.NetworkDispatcher
// wg keeps track of running goroutines.
wg sync.WaitGroup
// control is used to control the AF_XDP socket.
control *xdp.ControlBlock
// stopFD is used to stop the dispatch loop.
stopFD stopfd.StopFD
}
// Options specify the details about the fd-based endpoint to be created.
type Options struct {
// FD is used to read/write packets.
FD int
// ClosedFunc is a function to be called when an endpoint's peer (if
// any) closes its end of the communication pipe.
ClosedFunc func(tcpip.Error)
// Address is the link address for this endpoint.
Address tcpip.LinkAddress
// SaveRestore if true, indicates that this NIC capability set should
// include CapabilitySaveRestore
SaveRestore bool
// DisconnectOk if true, indicates that this NIC capability set should
// include CapabilityDisconnectOk.
DisconnectOk bool
// TXChecksumOffload if true, indicates that this endpoints capability
// set should include CapabilityTXChecksumOffload.
TXChecksumOffload bool
// RXChecksumOffload if true, indicates that this endpoints capability
// set should include CapabilityRXChecksumOffload.
RXChecksumOffload bool
// InterfaceIndex is the interface index of the underlying device.
InterfaceIndex int
}
// New creates a new endpoint from an AF_XDP socket.
func New(opts *Options) (stack.LinkEndpoint, error) {
caps := stack.CapabilityResolutionRequired
if opts.RXChecksumOffload {
caps |= stack.CapabilityRXChecksumOffload
}
if opts.TXChecksumOffload {
caps |= stack.CapabilityTXChecksumOffload
}
if opts.SaveRestore {
caps |= stack.CapabilitySaveRestore
}
if opts.DisconnectOk {
caps |= stack.CapabilityDisconnectOk
}
if err := unix.SetNonblock(opts.FD, true); err != nil {
return nil, fmt.Errorf("unix.SetNonblock(%v) failed: %v", opts.FD, err)
}
ep := &endpoint{
fd: opts.FD,
caps: caps,
closed: opts.ClosedFunc,
addr: opts.Address,
}
stopFD, err := stopfd.New()
if err != nil {
return nil, err
}
ep.stopFD = stopFD
// Use a 2MB UMEM to match the PACKET_MMAP dispatcher. There will be
// 1024 UMEM frames, and each queue will have 512 descriptors. Having
// fewer descriptors than frames prevents RX and TX from starving each
// other.
// TODO(b/240191988): Consider different numbers of descriptors for
// different queues.
const (
frameSize = 2048
umemSize = 1 << 21
nFrames = umemSize / frameSize
)
xdpOpts := xdp.ReadOnlySocketOpts{
NFrames: nFrames,
FrameSize: frameSize,
NDescriptors: nFrames / 2,
}
ep.control, err = xdp.ReadOnlyFromSocket(opts.FD, uint32(opts.InterfaceIndex), 0 /* queueID */, xdpOpts)
if err != nil {
return nil, fmt.Errorf("failed to create AF_XDP dispatcher: %v", err)
}
ep.control.UMEM.Lock()
defer ep.control.UMEM.Unlock()
ep.control.Fill.FillAll(&ep.control.UMEM)
return ep, nil
}
// Attach launches the goroutine that reads packets from the file descriptor and
// dispatches them via the provided dispatcher. If one is already attached,
// then nothing happens.
//
// Attach implements stack.LinkEndpoint.Attach.
func (ep *endpoint) Attach(networkDispatcher stack.NetworkDispatcher) {
ep.mu.Lock()
defer ep.mu.Unlock()
// nil means the NIC is being removed.
if networkDispatcher == nil && ep.IsAttached() {
ep.stopFD.Stop()
ep.Wait()
ep.networkDispatcher = nil
return
}
if networkDispatcher != nil && ep.networkDispatcher == nil {
ep.networkDispatcher = networkDispatcher
// Link endpoints are not savable. When transportation endpoints are
// saved, they stop sending outgoing packets and all incoming packets
// are rejected.
ep.wg.Add(1)
go func() { // S/R-SAFE: See above.
defer ep.wg.Done()
for {
cont, err := ep.dispatch()
if err != nil || !cont {
if ep.closed != nil {
ep.closed(err)
}
return
}
}
}()
}
}
// IsAttached implements stack.LinkEndpoint.IsAttached.
func (ep *endpoint) IsAttached() bool {
ep.mu.RLock()
defer ep.mu.RUnlock()
return ep.networkDispatcher != nil
}
// MTU implements stack.LinkEndpoint.MTU. It returns the value initialized
// during construction.
func (ep *endpoint) MTU() uint32 {
return MTU
}
// Capabilities implements stack.LinkEndpoint.Capabilities.
func (ep *endpoint) Capabilities() stack.LinkEndpointCapabilities {
return ep.caps
}
// MaxHeaderLength returns the maximum size of the link-layer header.
func (ep *endpoint) MaxHeaderLength() uint16 {
return uint16(header.EthernetMinimumSize)
}
// LinkAddress returns the link address of this endpoint.
func (ep *endpoint) LinkAddress() tcpip.LinkAddress {
return ep.addr
}
// Wait implements stack.LinkEndpoint.Wait. It waits for the endpoint to stop
// reading from its FD.
func (ep *endpoint) Wait() {
ep.wg.Wait()
}
// AddHeader implements stack.LinkEndpoint.AddHeader.
func (ep *endpoint) AddHeader(pkt stack.PacketBufferPtr) {
// Add ethernet header if needed.
eth := header.Ethernet(pkt.LinkHeader().Push(header.EthernetMinimumSize))
eth.Encode(&header.EthernetFields{
SrcAddr: pkt.EgressRoute.LocalLinkAddress,
DstAddr: pkt.EgressRoute.RemoteLinkAddress,
Type: pkt.NetworkProtocolNumber,
})
}
// ParseHeader implements stack.LinkEndpoint.ParseHeader.
func (ep *endpoint) ParseHeader(pkt stack.PacketBufferPtr) bool {
_, ok := pkt.LinkHeader().Consume(header.EthernetMinimumSize)
return ok
}
// ARPHardwareType implements stack.LinkEndpoint.ARPHardwareType.
func (ep *endpoint) ARPHardwareType() header.ARPHardwareType {
return header.ARPHardwareEther
}
// WritePackets writes outbound packets to the underlying file descriptors. If
// one is not currently writable, the packet is dropped.
//
// Each packet in pkts should have the following fields populated:
// - pkt.EgressRoute
// - pkt.NetworkProtocolNumber
//
// The following should not be populated, as GSO is not supported with XDP.
// - pkt.GSOOptions
func (ep *endpoint) WritePackets(pkts stack.PacketBufferList) (int, tcpip.Error) {
// We expect to be called via fifo, which imposes a limit of
// fifo.BatchSize.
var preallocatedBatch [fifo.BatchSize]unix.XDPDesc
batch := preallocatedBatch[:0]
ep.control.UMEM.Lock()
ep.control.Completion.FreeAll(&ep.control.UMEM)
// Reserve TX queue descriptors and umem buffers
nReserved, index := ep.control.TX.Reserve(&ep.control.UMEM, uint32(pkts.Len()))
if nReserved == 0 {
ep.control.UMEM.Unlock()
return 0, &tcpip.ErrNoBufferSpace{}
}
// Allocate UMEM space. In order to release the UMEM lock as soon as
// possible, we allocate up-front and copy data in after releasing.
for _, pkt := range pkts.AsSlice() {
batch = append(batch, unix.XDPDesc{
Addr: ep.control.UMEM.AllocFrame(),
Len: uint32(pkt.Size()),
})
}
ep.control.UMEM.Unlock()
for i, pkt := range pkts.AsSlice() {
// Copy packets into UMEM frame.
frame := ep.control.UMEM.Get(batch[i])
offset := 0
for _, buf := range pkt.AsSlices() {
offset += copy(frame[offset:], buf)
}
ep.control.TX.Set(index+uint32(i), batch[i])
}
// Notify the kernel that there're packets to write.
ep.control.TX.Notify()
return pkts.Len(), nil
}
func (ep *endpoint) dispatch() (bool, tcpip.Error) {
var views []*buffer.View
for {
stopped, errno := rawfile.BlockingPollUntilStopped(ep.stopFD.EFD, ep.fd, unix.POLLIN|unix.POLLERR)
if errno != 0 {
if errno == unix.EINTR {
continue
}
return !stopped, rawfile.TranslateErrno(errno)
}
if stopped {
return true, nil
}
// Avoid the cost of the poll syscall if possible by peeking
// until there are no packets left.
for {
// We can receive multiple packets at once.
nReceived, rxIndex := ep.control.RX.Peek()
if nReceived == 0 {
break
}
// Reuse views to avoid allocating.
views = views[:0]
// Populate views quickly so that we can release frames
// back to the kernel.
ep.control.UMEM.Lock()
for i := uint32(0); i < nReceived; i++ {
// Copy packet bytes into a view and free up the
// buffer.
descriptor := ep.control.RX.Get(rxIndex + i)
data := ep.control.UMEM.Get(descriptor)
view := buffer.NewViewWithData(data)
views = append(views, view)
ep.control.UMEM.FreeFrame(descriptor.Addr)
}
ep.control.Fill.FillAll(&ep.control.UMEM)
ep.control.UMEM.Unlock()
// Process each packet.
ep.mu.RLock()
d := ep.networkDispatcher
ep.mu.RUnlock()
for i := uint32(0); i < nReceived; i++ {
view := views[i]
data := view.AsSlice()
netProto := header.Ethernet(data).Type()
// Wrap the packet in a PacketBuffer and send it up the stack.
pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
Payload: buffer.MakeWithView(view),
})
// AF_XDP packets always have a link header.
if !ep.ParseHeader(pkt) {
panic("ParseHeader(_) must succeed")
}
d.DeliverNetworkPacket(netProto, pkt)
pkt.DecRef()
}
// Tell the kernel that we're done with these
// descriptors in the RX queue.
ep.control.RX.Release(nReceived)
}
return true, nil
}
}