pkg/tcpip/transport/raw/endpoint.go - third_party/gvisor.dev/gvisor/netstack - Git at Google

 // Copyright 2019 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 raw provides the implementation of raw sockets (see raw(7)). Raw
 // sockets allow applications to:
 //
 //   * manually write and inspect transport layer headers and payloads
 //   * receive all traffic of a given transport protocol (e.g. ICMP or UDP)
 //   * optionally write and inspect network layer headers of packets
 //
 // Raw sockets don't have any notion of ports, and incoming packets are
 // demultiplexed solely by protocol number. Thus, a raw UDP endpoint will
 // receive every UDP packet received by netstack. bind(2) and connect(2) can be
 // used to filter incoming packets by source and destination.
 package raw

 import (
 	"fmt"
 	"io"

 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 	"gvisor.dev/gvisor/pkg/waiter"
 )

 // +stateify savable
 type rawPacket struct {
 	rawPacketEntry
 	// data holds the actual packet data, including any headers and
 	// payload.
 	data buffer.VectorisedView `state:".(buffer.VectorisedView)"`
 	// timestampNS is the unix time at which the packet was received.
 	timestampNS int64
 	// senderAddr is the network address of the sender.
 	senderAddr tcpip.FullAddress
 }

 // endpoint is the raw socket implementation of tcpip.Endpoint. It is legal to
 // have goroutines make concurrent calls into the endpoint.
 //
 // Lock order:
 //   endpoint.mu
 //     endpoint.rcvMu
 //
 // +stateify savable
 type endpoint struct {
 	stack.TransportEndpointInfo
 	tcpip.DefaultSocketOptionsHandler

 	// The following fields are initialized at creation time and are
 	// immutable.
 	stack       *stack.Stack `state:"manual"`
 	waiterQueue *waiter.Queue
 	associated  bool

 	// The following fields are used to manage the receive queue and are
 	// protected by rcvMu.
 	rcvMu         sync.Mutex `state:"nosave"`
 	rcvList       rawPacketList
 	rcvBufSize    int
 	rcvBufSizeMax int `state:".(int)"`
 	rcvClosed     bool

 	// The following fields are protected by mu.
 	mu        sync.RWMutex `state:"nosave"`
 	closed    bool
 	connected bool
 	bound     bool
 	// route is the route to a remote network endpoint. It is set via
 	// Connect(), and is valid only when conneted is true.
 	route *stack.Route                 `state:"manual"`
 	stats tcpip.TransportEndpointStats `state:"nosave"`
 	// owner is used to get uid and gid of the packet.
 	owner tcpip.PacketOwner

 	// ops is used to get socket level options.
 	ops tcpip.SocketOptions
 }

 // NewEndpoint returns a raw  endpoint for the given protocols.
 func NewEndpoint(stack *stack.Stack, netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, tcpip.Error) {
 	return newEndpoint(stack, netProto, transProto, waiterQueue, true /* associated */)
 }

 func newEndpoint(s *stack.Stack, netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, waiterQueue *waiter.Queue, associated bool) (tcpip.Endpoint, tcpip.Error) {
 	if netProto != header.IPv4ProtocolNumber && netProto != header.IPv6ProtocolNumber {
 		return nil, &tcpip.ErrUnknownProtocol{}
 	}

 	e := &endpoint{
 		stack: s,
 		TransportEndpointInfo: stack.TransportEndpointInfo{
 			NetProto:   netProto,
 			TransProto: transProto,
 		},
 		waiterQueue:   waiterQueue,
 		rcvBufSizeMax: 32 * 1024,
 		associated:    associated,
 	}
 	e.ops.InitHandler(e, e.stack, tcpip.GetStackSendBufferLimits)
 	e.ops.SetHeaderIncluded(!associated)
 	e.ops.SetSendBufferSize(32*1024, false /* notify */)

 	// Override with stack defaults.
 	var ss tcpip.SendBufferSizeOption
 	if err := s.Option(&ss); err == nil {
 		e.ops.SetSendBufferSize(int64(ss.Default), false /* notify */)
 	}

 	var rs stack.ReceiveBufferSizeOption
 	if err := s.Option(&rs); err == nil {
 		e.rcvBufSizeMax = rs.Default
 	}

 	// Unassociated endpoints are write-only and users call Write() with IP
 	// headers included. Because they're write-only, We don't need to
 	// register with the stack.
 	if !associated {
 		e.rcvBufSizeMax = 0
 		e.waiterQueue = nil
 		return e, nil
 	}

 	if err := e.stack.RegisterRawTransportEndpoint(e.NetProto, e.TransProto, e); err != nil {
 		return nil, err
 	}

 	return e, nil
 }

 // Abort implements stack.TransportEndpoint.Abort.
 func (e *endpoint) Abort() {
 	e.Close()
 }

 // Close implements tcpip.Endpoint.Close.
 func (e *endpoint) Close() {
 	e.mu.Lock()
 	defer e.mu.Unlock()

 	if e.closed || !e.associated {
 		return
 	}

 	e.stack.UnregisterRawTransportEndpoint(e.NetProto, e.TransProto, e)

 	e.rcvMu.Lock()
 	defer e.rcvMu.Unlock()

 	// Clear the receive list.
 	e.rcvClosed = true
 	e.rcvBufSize = 0
 	for !e.rcvList.Empty() {
 		e.rcvList.Remove(e.rcvList.Front())
 	}

 	e.connected = false

 	if e.route != nil {
 		e.route.Release()
 		e.route = nil
 	}

 	e.closed = true

 	e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.EventIn | waiter.EventOut)
 }

 // ModerateRecvBuf implements tcpip.Endpoint.ModerateRecvBuf.
 func (e *endpoint) ModerateRecvBuf(copied int) {}

 func (e *endpoint) SetOwner(owner tcpip.PacketOwner) {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 	e.owner = owner
 }

 // Read implements tcpip.Endpoint.Read.
 func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult, tcpip.Error) {
 	e.rcvMu.Lock()

 	// If there's no data to read, return that read would block or that the
 	// endpoint is closed.
 	if e.rcvList.Empty() {
 		var err tcpip.Error = &tcpip.ErrWouldBlock{}
 		if e.rcvClosed {
 			e.stats.ReadErrors.ReadClosed.Increment()
 			err = &tcpip.ErrClosedForReceive{}
 		}
 		e.rcvMu.Unlock()
 		return tcpip.ReadResult{}, err
 	}

 	pkt := e.rcvList.Front()
 	if !opts.Peek {
 		e.rcvList.Remove(pkt)
 		e.rcvBufSize -= pkt.data.Size()
 	}

 	e.rcvMu.Unlock()

 	res := tcpip.ReadResult{
 		Total: pkt.data.Size(),
 		ControlMessages: tcpip.ControlMessages{
 			HasTimestamp: true,
 			Timestamp:    pkt.timestampNS,
 		},
 	}
 	if opts.NeedRemoteAddr {
 		res.RemoteAddr = pkt.senderAddr
 	}

 	n, err := pkt.data.ReadTo(dst, opts.Peek)
 	if n == 0 && err != nil {
 		return res, &tcpip.ErrBadBuffer{}
 	}
 	res.Count = n
 	return res, nil
 }

 // Write implements tcpip.Endpoint.Write.
 func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcpip.Error) {
 	// We can create, but not write to, unassociated IPv6 endpoints.
 	if !e.associated && e.TransportEndpointInfo.NetProto == header.IPv6ProtocolNumber {
 		return 0, &tcpip.ErrInvalidOptionValue{}
 	}

 	if opts.To != nil {
 		// Raw sockets do not support sending to a IPv4 address on a IPv6 endpoint.
 		if e.TransportEndpointInfo.NetProto == header.IPv6ProtocolNumber && len(opts.To.Addr) != header.IPv6AddressSize {
 			return 0, &tcpip.ErrInvalidOptionValue{}
 		}
 	}

 	n, err := e.write(p, opts)
 	switch err.(type) {
 	case nil:
 		e.stats.PacketsSent.Increment()
 	case *tcpip.ErrMessageTooLong, *tcpip.ErrInvalidOptionValue:
 		e.stats.WriteErrors.InvalidArgs.Increment()
 	case *tcpip.ErrClosedForSend:
 		e.stats.WriteErrors.WriteClosed.Increment()
 	case *tcpip.ErrInvalidEndpointState:
 		e.stats.WriteErrors.InvalidEndpointState.Increment()
 	case *tcpip.ErrNoRoute, *tcpip.ErrBroadcastDisabled, *tcpip.ErrNetworkUnreachable:
 		// Errors indicating any problem with IP routing of the packet.
 		e.stats.SendErrors.NoRoute.Increment()
 	default:
 		// For all other errors when writing to the network layer.
 		e.stats.SendErrors.SendToNetworkFailed.Increment()
 	}
 	return n, err
 }

 func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcpip.Error) {
 	// MSG_MORE is unimplemented. This also means that MSG_EOR is a no-op.
 	if opts.More {
 		return 0, &tcpip.ErrInvalidOptionValue{}
 	}
 	payloadBytes, route, owner, err := func() ([]byte, *stack.Route, tcpip.PacketOwner, tcpip.Error) {
 		e.mu.RLock()
 		defer e.mu.RUnlock()

 		if e.closed {
 			return nil, nil, nil, &tcpip.ErrInvalidEndpointState{}
 		}

 		payloadBytes := make([]byte, p.Len())
 		if _, err := io.ReadFull(p, payloadBytes); err != nil {
 			return nil, nil, nil, &tcpip.ErrBadBuffer{}
 		}

 		// If this is an unassociated socket and callee provided a nonzero
 		// destination address, route using that address.
 		if e.ops.GetHeaderIncluded() {
 			ip := header.IPv4(payloadBytes)
 			if !ip.IsValid(len(payloadBytes)) {
 				return nil, nil, nil, &tcpip.ErrInvalidOptionValue{}
 			}
 			dstAddr := ip.DestinationAddress()
 			// Update dstAddr with the address in the IP header, unless
 			// opts.To is set (e.g. if sendto specifies a specific
 			// address).
 			if dstAddr != tcpip.Address([]byte{0, 0, 0, 0}) && opts.To == nil {
 				opts.To = &tcpip.FullAddress{
 					NIC:  0,       // NIC is unset.
 					Addr: dstAddr, // The address from the payload.
 					Port: 0,       // There are no ports here.
 				}
 			}
 		}

 		// Did the user caller provide a destination? If not, use the connected
 		// destination.
 		if opts.To == nil {
 			// If the user doesn't specify a destination, they should have
 			// connected to another address.
 			if !e.connected {
 				return nil, nil, nil, &tcpip.ErrDestinationRequired{}
 			}

 			e.route.Acquire()

 			return payloadBytes, e.route, e.owner, nil
 		}

 		// The caller provided a destination. Reject destination address if it
 		// goes through a different NIC than the endpoint was bound to.
 		nic := opts.To.NIC
 		if e.bound && nic != 0 && nic != e.BindNICID {
 			return nil, nil, nil, &tcpip.ErrNoRoute{}
 		}

 		// Find the route to the destination. If BindAddress is 0,
 		// FindRoute will choose an appropriate source address.
 		route, err := e.stack.FindRoute(nic, e.BindAddr, opts.To.Addr, e.NetProto, false)
 		if err != nil {
 			return nil, nil, nil, err
 		}

 		return payloadBytes, route, e.owner, nil
 	}()
 	if err != nil {
 		return 0, err
 	}
 	defer route.Release()

 	if e.ops.GetHeaderIncluded() {
 		pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
 			Data: buffer.View(payloadBytes).ToVectorisedView(),
 		})
 		if err := route.WriteHeaderIncludedPacket(pkt); err != nil {
 			return 0, err
 		}
 	} else {
 		pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
 			ReserveHeaderBytes: int(route.MaxHeaderLength()),
 			Data:               buffer.View(payloadBytes).ToVectorisedView(),
 		})
 		pkt.Owner = owner
 		if err := route.WritePacket(nil /* gso */, stack.NetworkHeaderParams{
 			Protocol: e.TransProto,
 			TTL:      route.DefaultTTL(),
 			TOS:      stack.DefaultTOS,
 		}, pkt); err != nil {
 			return 0, err
 		}
 	}

 	return int64(len(payloadBytes)), nil
 }

 // Disconnect implements tcpip.Endpoint.Disconnect.
 func (*endpoint) Disconnect() tcpip.Error {
 	return &tcpip.ErrNotSupported{}
 }

 // Connect implements tcpip.Endpoint.Connect.
 func (e *endpoint) Connect(addr tcpip.FullAddress) tcpip.Error {
 	// Raw sockets do not support connecting to a IPv4 address on a IPv6 endpoint.
 	if e.TransportEndpointInfo.NetProto == header.IPv6ProtocolNumber && len(addr.Addr) != header.IPv6AddressSize {
 		return &tcpip.ErrAddressFamilyNotSupported{}
 	}

 	e.mu.Lock()
 	defer e.mu.Unlock()

 	if e.closed {
 		return &tcpip.ErrInvalidEndpointState{}
 	}

 	nic := addr.NIC
 	if e.bound {
 		if e.BindNICID == 0 {
 			// If we're bound, but not to a specific NIC, the NIC
 			// in addr will be used. Nothing to do here.
 		} else if addr.NIC == 0 {
 			// If we're bound to a specific NIC, but addr doesn't
 			// specify a NIC, use the bound NIC.
 			nic = e.BindNICID
 		} else if addr.NIC != e.BindNICID {
 			// We're bound and addr specifies a NIC. They must be
 			// the same.
 			return &tcpip.ErrInvalidEndpointState{}
 		}
 	}

 	// Find a route to the destination.
 	route, err := e.stack.FindRoute(nic, tcpip.Address(""), addr.Addr, e.NetProto, false)
 	if err != nil {
 		return err
 	}

 	if e.associated {
 		// Re-register the endpoint with the appropriate NIC.
 		if err := e.stack.RegisterRawTransportEndpoint(e.NetProto, e.TransProto, e); err != nil {
 			route.Release()
 			return err
 		}
 		e.stack.UnregisterRawTransportEndpoint(e.NetProto, e.TransProto, e)
 		e.RegisterNICID = nic
 	}

 	if e.route != nil {
 		// If the endpoint was previously connected then release any previous route.
 		e.route.Release()
 	}
 	e.route = route
 	e.connected = true

 	return nil
 }

 // Shutdown implements tcpip.Endpoint.Shutdown. It's a noop for raw sockets.
 func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) tcpip.Error {
 	e.mu.Lock()
 	defer e.mu.Unlock()

 	if !e.connected {
 		return &tcpip.ErrNotConnected{}
 	}
 	return nil
 }

 // Listen implements tcpip.Endpoint.Listen.
 func (*endpoint) Listen(backlog int) tcpip.Error {
 	return &tcpip.ErrNotSupported{}
 }

 // Accept implements tcpip.Endpoint.Accept.
 func (*endpoint) Accept(*tcpip.FullAddress) (tcpip.Endpoint, *waiter.Queue, tcpip.Error) {
 	return nil, nil, &tcpip.ErrNotSupported{}
 }

 // Bind implements tcpip.Endpoint.Bind.
 func (e *endpoint) Bind(addr tcpip.FullAddress) tcpip.Error {
 	e.mu.Lock()
 	defer e.mu.Unlock()

 	// If a local address was specified, verify that it's valid.
 	if len(addr.Addr) != 0 && e.stack.CheckLocalAddress(e.RegisterNICID, e.NetProto, addr.Addr) == 0 {
 		return &tcpip.ErrBadLocalAddress{}
 	}

 	if e.associated {
 		// Re-register the endpoint with the appropriate NIC.
 		if err := e.stack.RegisterRawTransportEndpoint(e.NetProto, e.TransProto, e); err != nil {
 			return err
 		}
 		e.stack.UnregisterRawTransportEndpoint(e.NetProto, e.TransProto, e)
 		e.RegisterNICID = addr.NIC
 		e.BindNICID = addr.NIC
 	}

 	e.BindAddr = addr.Addr
 	e.bound = true

 	return nil
 }

 // GetLocalAddress implements tcpip.Endpoint.GetLocalAddress.
 func (*endpoint) GetLocalAddress() (tcpip.FullAddress, tcpip.Error) {
 	return tcpip.FullAddress{}, &tcpip.ErrNotSupported{}
 }

 // GetRemoteAddress implements tcpip.Endpoint.GetRemoteAddress.
 func (*endpoint) GetRemoteAddress() (tcpip.FullAddress, tcpip.Error) {
 	// Even a connected socket doesn't return a remote address.
 	return tcpip.FullAddress{}, &tcpip.ErrNotConnected{}
 }

 // Readiness implements tcpip.Endpoint.Readiness.
 func (e *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
 	// The endpoint is always writable.
 	result := waiter.EventOut & mask

 	// Determine whether the endpoint is readable.
 	if (mask & waiter.EventIn) != 0 {
 		e.rcvMu.Lock()
 		if !e.rcvList.Empty() || e.rcvClosed {
 			result |= waiter.EventIn
 		}
 		e.rcvMu.Unlock()
 	}

 	return result
 }

 // SetSockOpt implements tcpip.Endpoint.SetSockOpt.
 func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) tcpip.Error {
 	switch opt.(type) {
 	case *tcpip.SocketDetachFilterOption:
 		return nil

 	default:
 		return &tcpip.ErrUnknownProtocolOption{}
 	}
 }

 // SetSockOptInt implements tcpip.Endpoint.SetSockOptInt.
 func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) tcpip.Error {
 	switch opt {
 	case tcpip.ReceiveBufferSizeOption:
 		// Make sure the receive buffer size is within the min and max
 		// allowed.
 		var rs stack.ReceiveBufferSizeOption
 		if err := e.stack.Option(&rs); err != nil {
 			panic(fmt.Sprintf("s.Option(%#v) = %s", rs, err))
 		}
 		if v > rs.Max {
 			v = rs.Max
 		}
 		if v < rs.Min {
 			v = rs.Min
 		}
 		e.rcvMu.Lock()
 		e.rcvBufSizeMax = v
 		e.rcvMu.Unlock()
 		return nil

 	default:
 		return &tcpip.ErrUnknownProtocolOption{}
 	}
 }

 // GetSockOpt implements tcpip.Endpoint.GetSockOpt.
 func (e *endpoint) GetSockOpt(opt tcpip.GettableSocketOption) tcpip.Error {
 	return &tcpip.ErrUnknownProtocolOption{}
 }

 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
 func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, tcpip.Error) {
 	switch opt {
 	case tcpip.ReceiveQueueSizeOption:
 		v := 0
 		e.rcvMu.Lock()
 		if !e.rcvList.Empty() {
 			p := e.rcvList.Front()
 			v = p.data.Size()
 		}
 		e.rcvMu.Unlock()
 		return v, nil

 	case tcpip.ReceiveBufferSizeOption:
 		e.rcvMu.Lock()
 		v := e.rcvBufSizeMax
 		e.rcvMu.Unlock()
 		return v, nil

 	default:
 		return -1, &tcpip.ErrUnknownProtocolOption{}
 	}
 }

 // HandlePacket implements stack.RawTransportEndpoint.HandlePacket.
 func (e *endpoint) HandlePacket(pkt *stack.PacketBuffer) {
 	e.mu.RLock()
 	e.rcvMu.Lock()

 	// Drop the packet if our buffer is currently full or if this is an unassociated
 	// endpoint (i.e endpoint created  w/ IPPROTO_RAW). Such endpoints are send only
 	// See: https://man7.org/linux/man-pages/man7/raw.7.html
 	//
 	//    An IPPROTO_RAW socket is send only.  If you really want to receive
 	//    all IP packets, use a packet(7) socket with the ETH_P_IP protocol.
 	//    Note that packet sockets don't reassemble IP fragments, unlike raw
 	//    sockets.
 	if e.rcvClosed || !e.associated {
 		e.rcvMu.Unlock()
 		e.mu.RUnlock()
 		e.stack.Stats().DroppedPackets.Increment()
 		e.stats.ReceiveErrors.ClosedReceiver.Increment()
 		return
 	}

 	if e.rcvBufSize >= e.rcvBufSizeMax {
 		e.rcvMu.Unlock()
 		e.mu.RUnlock()
 		e.stack.Stats().DroppedPackets.Increment()
 		e.stats.ReceiveErrors.ReceiveBufferOverflow.Increment()
 		return
 	}

 	remoteAddr := pkt.Network().SourceAddress()

 	if e.bound {
 		// If bound to a NIC, only accept data for that NIC.
 		if e.BindNICID != 0 && e.BindNICID != pkt.NICID {
 			e.rcvMu.Unlock()
 			e.mu.RUnlock()
 			return
 		}
 		// If bound to an address, only accept data for that address.
 		if e.BindAddr != "" && e.BindAddr != remoteAddr {
 			e.rcvMu.Unlock()
 			e.mu.RUnlock()
 			return
 		}
 	}

 	// If connected, only accept packets from the remote address we
 	// connected to.
 	if e.connected && e.route.RemoteAddress != remoteAddr {
 		e.rcvMu.Unlock()
 		e.mu.RUnlock()
 		return
 	}

 	wasEmpty := e.rcvBufSize == 0

 	// Push new packet into receive list and increment the buffer size.
 	packet := &rawPacket{
 		senderAddr: tcpip.FullAddress{
 			NIC:  pkt.NICID,
 			Addr: remoteAddr,
 		},
 	}

 	// Raw IPv4 endpoints return the IP header, but IPv6 endpoints do not.
 	// We copy headers' underlying bytes because pkt.*Header may point to
 	// the middle of a slice, and another struct may point to the "outer"
 	// slice. Save/restore doesn't support overlapping slices and will fail.
 	var combinedVV buffer.VectorisedView
 	if e.TransportEndpointInfo.NetProto == header.IPv4ProtocolNumber {
 		network, transport := pkt.NetworkHeader().View(), pkt.TransportHeader().View()
 		headers := make(buffer.View, 0, len(network)+len(transport))
 		headers = append(headers, network...)
 		headers = append(headers, transport...)
 		combinedVV = headers.ToVectorisedView()
 	} else {
 		combinedVV = append(buffer.View(nil), pkt.TransportHeader().View()...).ToVectorisedView()
 	}
 	combinedVV.Append(pkt.Data().ExtractVV())
 	packet.data = combinedVV
 	packet.timestampNS = e.stack.Clock().NowNanoseconds()

 	e.rcvList.PushBack(packet)
 	e.rcvBufSize += packet.data.Size()
 	e.rcvMu.Unlock()
 	e.mu.RUnlock()
 	e.stats.PacketsReceived.Increment()
 	// Notify waiters that there's data to be read.
 	if wasEmpty {
 		e.waiterQueue.Notify(waiter.EventIn)
 	}
 }

 // State implements socket.Socket.State.
 func (e *endpoint) State() uint32 {
 	return 0
 }

 // Info returns a copy of the endpoint info.
 func (e *endpoint) Info() tcpip.EndpointInfo {
 	e.mu.RLock()
 	// Make a copy of the endpoint info.
 	ret := e.TransportEndpointInfo
 	e.mu.RUnlock()
 	return &ret
 }

 // Stats returns a pointer to the endpoint stats.
 func (e *endpoint) Stats() tcpip.EndpointStats {
 	return &e.stats
 }

 // Wait implements stack.TransportEndpoint.Wait.
 func (*endpoint) Wait() {}

 // LastError implements tcpip.Endpoint.LastError.
 func (*endpoint) LastError() tcpip.Error {
 	return nil
 }

 // SocketOptions implements tcpip.Endpoint.SocketOptions.
 func (e *endpoint) SocketOptions() *tcpip.SocketOptions {
 	return &e.ops
 }
	// Copyright 2019 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 raw provides the implementation of raw sockets (see raw(7)). Raw
	// sockets allow applications to:
	//
	// * manually write and inspect transport layer headers and payloads
	// * receive all traffic of a given transport protocol (e.g. ICMP or UDP)
	// * optionally write and inspect network layer headers of packets
	//
	// Raw sockets don't have any notion of ports, and incoming packets are
	// demultiplexed solely by protocol number. Thus, a raw UDP endpoint will
	// receive every UDP packet received by netstack. bind(2) and connect(2) can be
	// used to filter incoming packets by source and destination.
	package raw

	import (
	"fmt"
	"io"

	"gvisor.dev/gvisor/pkg/sync"
	"gvisor.dev/gvisor/pkg/tcpip"
	"gvisor.dev/gvisor/pkg/tcpip/buffer"
	"gvisor.dev/gvisor/pkg/tcpip/header"
	"gvisor.dev/gvisor/pkg/tcpip/stack"
	"gvisor.dev/gvisor/pkg/waiter"
	)

	// +stateify savable
	type rawPacket struct {
	rawPacketEntry
	// data holds the actual packet data, including any headers and
	// payload.
	data buffer.VectorisedView `state:".(buffer.VectorisedView)"`
	// timestampNS is the unix time at which the packet was received.
	timestampNS int64
	// senderAddr is the network address of the sender.
	senderAddr tcpip.FullAddress
	}

	// endpoint is the raw socket implementation of tcpip.Endpoint. It is legal to
	// have goroutines make concurrent calls into the endpoint.
	//
	// Lock order:
	// endpoint.mu
	// endpoint.rcvMu
	//
	// +stateify savable
	type endpoint struct {
	stack.TransportEndpointInfo
	tcpip.DefaultSocketOptionsHandler

	// The following fields are initialized at creation time and are
	// immutable.
	stack *stack.Stack `state:"manual"`
	waiterQueue *waiter.Queue
	associated bool

	// The following fields are used to manage the receive queue and are
	// protected by rcvMu.
	rcvMu sync.Mutex `state:"nosave"`
	rcvList rawPacketList
	rcvBufSize int
	rcvBufSizeMax int `state:".(int)"`
	rcvClosed bool

	// The following fields are protected by mu.
	mu sync.RWMutex `state:"nosave"`
	closed bool
	connected bool
	bound bool
	// route is the route to a remote network endpoint. It is set via
	// Connect(), and is valid only when conneted is true.
	route *stack.Route `state:"manual"`
	stats tcpip.TransportEndpointStats `state:"nosave"`
	// owner is used to get uid and gid of the packet.
	owner tcpip.PacketOwner

	// ops is used to get socket level options.
	ops tcpip.SocketOptions
	}

	// NewEndpoint returns a raw endpoint for the given protocols.
	func NewEndpoint(stack stack.Stack, netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, waiterQueue waiter.Queue) (tcpip.Endpoint, tcpip.Error) {
	return newEndpoint(stack, netProto, transProto, waiterQueue, true /* associated */)
	}

	func newEndpoint(s stack.Stack, netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, waiterQueue waiter.Queue, associated bool) (tcpip.Endpoint, tcpip.Error) {
	if netProto != header.IPv4ProtocolNumber && netProto != header.IPv6ProtocolNumber {
	return nil, &tcpip.ErrUnknownProtocol{}
	}

	e := &endpoint{
	stack: s,
	TransportEndpointInfo: stack.TransportEndpointInfo{
	NetProto: netProto,
	TransProto: transProto,
	},
	waiterQueue: waiterQueue,
	rcvBufSizeMax: 32 * 1024,
	associated: associated,
	}
	e.ops.InitHandler(e, e.stack, tcpip.GetStackSendBufferLimits)
	e.ops.SetHeaderIncluded(!associated)
	e.ops.SetSendBufferSize(321024, false / notify */)

	// Override with stack defaults.
	var ss tcpip.SendBufferSizeOption
	if err := s.Option(&ss); err == nil {
	e.ops.SetSendBufferSize(int64(ss.Default), false /* notify */)
	}

	var rs stack.ReceiveBufferSizeOption
	if err := s.Option(&rs); err == nil {
	e.rcvBufSizeMax = rs.Default
	}

	// Unassociated endpoints are write-only and users call Write() with IP
	// headers included. Because they're write-only, We don't need to
	// register with the stack.
	if !associated {
	e.rcvBufSizeMax = 0
	e.waiterQueue = nil
	return e, nil
	}

	if err := e.stack.RegisterRawTransportEndpoint(e.NetProto, e.TransProto, e); err != nil {
	return nil, err
	}

	return e, nil
	}

	// Abort implements stack.TransportEndpoint.Abort.
	func (e *endpoint) Abort() {
	e.Close()
	}

	// Close implements tcpip.Endpoint.Close.
	func (e *endpoint) Close() {
	e.mu.Lock()
	defer e.mu.Unlock()

	if e.closed \|\| !e.associated {
	return
	}

	e.stack.UnregisterRawTransportEndpoint(e.NetProto, e.TransProto, e)

	e.rcvMu.Lock()
	defer e.rcvMu.Unlock()

	// Clear the receive list.
	e.rcvClosed = true
	e.rcvBufSize = 0
	for !e.rcvList.Empty() {
	e.rcvList.Remove(e.rcvList.Front())
	}

	e.connected = false

	if e.route != nil {
	e.route.Release()
	e.route = nil
	}

	e.closed = true

	e.waiterQueue.Notify(waiter.EventHUp \| waiter.EventErr \| waiter.EventIn \| waiter.EventOut)
	}

	// ModerateRecvBuf implements tcpip.Endpoint.ModerateRecvBuf.
	func (e *endpoint) ModerateRecvBuf(copied int) {}

	func (e *endpoint) SetOwner(owner tcpip.PacketOwner) {
	e.mu.Lock()
	defer e.mu.Unlock()
	e.owner = owner
	}

	// Read implements tcpip.Endpoint.Read.
	func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult, tcpip.Error) {
	e.rcvMu.Lock()

	// If there's no data to read, return that read would block or that the
	// endpoint is closed.
	if e.rcvList.Empty() {
	var err tcpip.Error = &tcpip.ErrWouldBlock{}
	if e.rcvClosed {
	e.stats.ReadErrors.ReadClosed.Increment()
	err = &tcpip.ErrClosedForReceive{}
	}
	e.rcvMu.Unlock()
	return tcpip.ReadResult{}, err
	}

	pkt := e.rcvList.Front()
	if !opts.Peek {
	e.rcvList.Remove(pkt)
	e.rcvBufSize -= pkt.data.Size()
	}

	e.rcvMu.Unlock()

	res := tcpip.ReadResult{
	Total: pkt.data.Size(),
	ControlMessages: tcpip.ControlMessages{
	HasTimestamp: true,
	Timestamp: pkt.timestampNS,
	},
	}
	if opts.NeedRemoteAddr {
	res.RemoteAddr = pkt.senderAddr
	}

	n, err := pkt.data.ReadTo(dst, opts.Peek)
	if n == 0 && err != nil {
	return res, &tcpip.ErrBadBuffer{}
	}
	res.Count = n
	return res, nil
	}

	// Write implements tcpip.Endpoint.Write.
	func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcpip.Error) {
	// We can create, but not write to, unassociated IPv6 endpoints.
	if !e.associated && e.TransportEndpointInfo.NetProto == header.IPv6ProtocolNumber {
	return 0, &tcpip.ErrInvalidOptionValue{}
	}

	if opts.To != nil {
	// Raw sockets do not support sending to a IPv4 address on a IPv6 endpoint.
	if e.TransportEndpointInfo.NetProto == header.IPv6ProtocolNumber && len(opts.To.Addr) != header.IPv6AddressSize {
	return 0, &tcpip.ErrInvalidOptionValue{}
	}
	}

	n, err := e.write(p, opts)
	switch err.(type) {
	case nil:
	e.stats.PacketsSent.Increment()
	case tcpip.ErrMessageTooLong, tcpip.ErrInvalidOptionValue:
	e.stats.WriteErrors.InvalidArgs.Increment()
	case *tcpip.ErrClosedForSend:
	e.stats.WriteErrors.WriteClosed.Increment()
	case *tcpip.ErrInvalidEndpointState:
	e.stats.WriteErrors.InvalidEndpointState.Increment()
	case tcpip.ErrNoRoute, tcpip.ErrBroadcastDisabled, *tcpip.ErrNetworkUnreachable:
	// Errors indicating any problem with IP routing of the packet.
	e.stats.SendErrors.NoRoute.Increment()
	default:
	// For all other errors when writing to the network layer.
	e.stats.SendErrors.SendToNetworkFailed.Increment()
	}
	return n, err
	}

	func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcpip.Error) {
	// MSG_MORE is unimplemented. This also means that MSG_EOR is a no-op.
	if opts.More {
	return 0, &tcpip.ErrInvalidOptionValue{}
	}
	payloadBytes, route, owner, err := func() ([]byte, *stack.Route, tcpip.PacketOwner, tcpip.Error) {
	e.mu.RLock()
	defer e.mu.RUnlock()

	if e.closed {
	return nil, nil, nil, &tcpip.ErrInvalidEndpointState{}
	}

	payloadBytes := make([]byte, p.Len())
	if _, err := io.ReadFull(p, payloadBytes); err != nil {
	return nil, nil, nil, &tcpip.ErrBadBuffer{}
	}

	// If this is an unassociated socket and callee provided a nonzero
	// destination address, route using that address.
	if e.ops.GetHeaderIncluded() {
	ip := header.IPv4(payloadBytes)
	if !ip.IsValid(len(payloadBytes)) {
	return nil, nil, nil, &tcpip.ErrInvalidOptionValue{}
	}
	dstAddr := ip.DestinationAddress()
	// Update dstAddr with the address in the IP header, unless
	// opts.To is set (e.g. if sendto specifies a specific
	// address).
	if dstAddr != tcpip.Address([]byte{0, 0, 0, 0}) && opts.To == nil {
	opts.To = &tcpip.FullAddress{
	NIC: 0, // NIC is unset.
	Addr: dstAddr, // The address from the payload.
	Port: 0, // There are no ports here.
	}
	}
	}

	// Did the user caller provide a destination? If not, use the connected
	// destination.
	if opts.To == nil {
	// If the user doesn't specify a destination, they should have
	// connected to another address.
	if !e.connected {
	return nil, nil, nil, &tcpip.ErrDestinationRequired{}
	}

	e.route.Acquire()

	return payloadBytes, e.route, e.owner, nil
	}

	// The caller provided a destination. Reject destination address if it
	// goes through a different NIC than the endpoint was bound to.
	nic := opts.To.NIC
	if e.bound && nic != 0 && nic != e.BindNICID {
	return nil, nil, nil, &tcpip.ErrNoRoute{}
	}

	// Find the route to the destination. If BindAddress is 0,
	// FindRoute will choose an appropriate source address.
	route, err := e.stack.FindRoute(nic, e.BindAddr, opts.To.Addr, e.NetProto, false)
	if err != nil {
	return nil, nil, nil, err
	}

	return payloadBytes, route, e.owner, nil
	}()
	if err != nil {
	return 0, err
	}
	defer route.Release()

	if e.ops.GetHeaderIncluded() {
	pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
	Data: buffer.View(payloadBytes).ToVectorisedView(),
	})
	if err := route.WriteHeaderIncludedPacket(pkt); err != nil {
	return 0, err
	}
	} else {
	pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
	ReserveHeaderBytes: int(route.MaxHeaderLength()),
	Data: buffer.View(payloadBytes).ToVectorisedView(),
	})
	pkt.Owner = owner
	if err := route.WritePacket(nil /* gso */, stack.NetworkHeaderParams{
	Protocol: e.TransProto,
	TTL: route.DefaultTTL(),
	TOS: stack.DefaultTOS,
	}, pkt); err != nil {
	return 0, err
	}
	}

	return int64(len(payloadBytes)), nil
	}

	// Disconnect implements tcpip.Endpoint.Disconnect.
	func (*endpoint) Disconnect() tcpip.Error {
	return &tcpip.ErrNotSupported{}
	}

	// Connect implements tcpip.Endpoint.Connect.
	func (e *endpoint) Connect(addr tcpip.FullAddress) tcpip.Error {
	// Raw sockets do not support connecting to a IPv4 address on a IPv6 endpoint.
	if e.TransportEndpointInfo.NetProto == header.IPv6ProtocolNumber && len(addr.Addr) != header.IPv6AddressSize {
	return &tcpip.ErrAddressFamilyNotSupported{}
	}

	e.mu.Lock()
	defer e.mu.Unlock()

	if e.closed {
	return &tcpip.ErrInvalidEndpointState{}
	}

	nic := addr.NIC
	if e.bound {
	if e.BindNICID == 0 {
	// If we're bound, but not to a specific NIC, the NIC
	// in addr will be used. Nothing to do here.
	} else if addr.NIC == 0 {
	// If we're bound to a specific NIC, but addr doesn't
	// specify a NIC, use the bound NIC.
	nic = e.BindNICID
	} else if addr.NIC != e.BindNICID {
	// We're bound and addr specifies a NIC. They must be
	// the same.
	return &tcpip.ErrInvalidEndpointState{}
	}
	}

	// Find a route to the destination.
	route, err := e.stack.FindRoute(nic, tcpip.Address(""), addr.Addr, e.NetProto, false)
	if err != nil {
	return err
	}

	if e.associated {
	// Re-register the endpoint with the appropriate NIC.
	if err := e.stack.RegisterRawTransportEndpoint(e.NetProto, e.TransProto, e); err != nil {
	route.Release()
	return err
	}
	e.stack.UnregisterRawTransportEndpoint(e.NetProto, e.TransProto, e)
	e.RegisterNICID = nic
	}

	if e.route != nil {
	// If the endpoint was previously connected then release any previous route.
	e.route.Release()
	}
	e.route = route
	e.connected = true

	return nil
	}

	// Shutdown implements tcpip.Endpoint.Shutdown. It's a noop for raw sockets.
	func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) tcpip.Error {
	e.mu.Lock()
	defer e.mu.Unlock()

	if !e.connected {
	return &tcpip.ErrNotConnected{}
	}
	return nil
	}

	// Listen implements tcpip.Endpoint.Listen.
	func (*endpoint) Listen(backlog int) tcpip.Error {
	return &tcpip.ErrNotSupported{}
	}

	// Accept implements tcpip.Endpoint.Accept.
	func (endpoint) Accept(tcpip.FullAddress) (tcpip.Endpoint, *waiter.Queue, tcpip.Error) {
	return nil, nil, &tcpip.ErrNotSupported{}
	}

	// Bind implements tcpip.Endpoint.Bind.
	func (e *endpoint) Bind(addr tcpip.FullAddress) tcpip.Error {
	e.mu.Lock()
	defer e.mu.Unlock()

	// If a local address was specified, verify that it's valid.
	if len(addr.Addr) != 0 && e.stack.CheckLocalAddress(e.RegisterNICID, e.NetProto, addr.Addr) == 0 {
	return &tcpip.ErrBadLocalAddress{}
	}

	if e.associated {
	// Re-register the endpoint with the appropriate NIC.
	if err := e.stack.RegisterRawTransportEndpoint(e.NetProto, e.TransProto, e); err != nil {
	return err
	}
	e.stack.UnregisterRawTransportEndpoint(e.NetProto, e.TransProto, e)
	e.RegisterNICID = addr.NIC
	e.BindNICID = addr.NIC
	}

	e.BindAddr = addr.Addr
	e.bound = true

	return nil
	}

	// GetLocalAddress implements tcpip.Endpoint.GetLocalAddress.
	func (*endpoint) GetLocalAddress() (tcpip.FullAddress, tcpip.Error) {
	return tcpip.FullAddress{}, &tcpip.ErrNotSupported{}
	}

	// GetRemoteAddress implements tcpip.Endpoint.GetRemoteAddress.
	func (*endpoint) GetRemoteAddress() (tcpip.FullAddress, tcpip.Error) {
	// Even a connected socket doesn't return a remote address.
	return tcpip.FullAddress{}, &tcpip.ErrNotConnected{}
	}

	// Readiness implements tcpip.Endpoint.Readiness.
	func (e *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
	// The endpoint is always writable.
	result := waiter.EventOut & mask

	// Determine whether the endpoint is readable.
	if (mask & waiter.EventIn) != 0 {
	e.rcvMu.Lock()
	if !e.rcvList.Empty() \|\| e.rcvClosed {
	result \|= waiter.EventIn
	}
	e.rcvMu.Unlock()
	}

	return result
	}

	// SetSockOpt implements tcpip.Endpoint.SetSockOpt.
	func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) tcpip.Error {
	switch opt.(type) {
	case *tcpip.SocketDetachFilterOption:
	return nil

	default:
	return &tcpip.ErrUnknownProtocolOption{}
	}
	}

	// SetSockOptInt implements tcpip.Endpoint.SetSockOptInt.
	func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) tcpip.Error {
	switch opt {
	case tcpip.ReceiveBufferSizeOption:
	// Make sure the receive buffer size is within the min and max
	// allowed.
	var rs stack.ReceiveBufferSizeOption
	if err := e.stack.Option(&rs); err != nil {
	panic(fmt.Sprintf("s.Option(%#v) = %s", rs, err))
	}
	if v > rs.Max {
	v = rs.Max
	}
	if v < rs.Min {
	v = rs.Min
	}
	e.rcvMu.Lock()
	e.rcvBufSizeMax = v
	e.rcvMu.Unlock()
	return nil

	default:
	return &tcpip.ErrUnknownProtocolOption{}
	}
	}

	// GetSockOpt implements tcpip.Endpoint.GetSockOpt.
	func (e *endpoint) GetSockOpt(opt tcpip.GettableSocketOption) tcpip.Error {
	return &tcpip.ErrUnknownProtocolOption{}
	}

	// GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
	func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, tcpip.Error) {
	switch opt {
	case tcpip.ReceiveQueueSizeOption:
	v := 0
	e.rcvMu.Lock()
	if !e.rcvList.Empty() {
	p := e.rcvList.Front()
	v = p.data.Size()
	}
	e.rcvMu.Unlock()
	return v, nil

	case tcpip.ReceiveBufferSizeOption:
	e.rcvMu.Lock()
	v := e.rcvBufSizeMax
	e.rcvMu.Unlock()
	return v, nil

	default:
	return -1, &tcpip.ErrUnknownProtocolOption{}
	}
	}

	// HandlePacket implements stack.RawTransportEndpoint.HandlePacket.
	func (e endpoint) HandlePacket(pkt stack.PacketBuffer) {
	e.mu.RLock()
	e.rcvMu.Lock()

	// Drop the packet if our buffer is currently full or if this is an unassociated
	// endpoint (i.e endpoint created w/ IPPROTO_RAW). Such endpoints are send only
	// See: https://man7.org/linux/man-pages/man7/raw.7.html
	//
	// An IPPROTO_RAW socket is send only. If you really want to receive
	// all IP packets, use a packet(7) socket with the ETH_P_IP protocol.
	// Note that packet sockets don't reassemble IP fragments, unlike raw
	// sockets.
	if e.rcvClosed \|\| !e.associated {
	e.rcvMu.Unlock()
	e.mu.RUnlock()
	e.stack.Stats().DroppedPackets.Increment()
	e.stats.ReceiveErrors.ClosedReceiver.Increment()
	return
	}

	if e.rcvBufSize >= e.rcvBufSizeMax {
	e.rcvMu.Unlock()
	e.mu.RUnlock()
	e.stack.Stats().DroppedPackets.Increment()
	e.stats.ReceiveErrors.ReceiveBufferOverflow.Increment()
	return
	}

	remoteAddr := pkt.Network().SourceAddress()

	if e.bound {
	// If bound to a NIC, only accept data for that NIC.
	if e.BindNICID != 0 && e.BindNICID != pkt.NICID {
	e.rcvMu.Unlock()
	e.mu.RUnlock()
	return
	}
	// If bound to an address, only accept data for that address.
	if e.BindAddr != "" && e.BindAddr != remoteAddr {
	e.rcvMu.Unlock()
	e.mu.RUnlock()
	return
	}
	}

	// If connected, only accept packets from the remote address we
	// connected to.
	if e.connected && e.route.RemoteAddress != remoteAddr {
	e.rcvMu.Unlock()
	e.mu.RUnlock()
	return
	}

	wasEmpty := e.rcvBufSize == 0

	// Push new packet into receive list and increment the buffer size.
	packet := &rawPacket{
	senderAddr: tcpip.FullAddress{
	NIC: pkt.NICID,
	Addr: remoteAddr,
	},
	}

	// Raw IPv4 endpoints return the IP header, but IPv6 endpoints do not.
	// We copy headers' underlying bytes because pkt.*Header may point to
	// the middle of a slice, and another struct may point to the "outer"
	// slice. Save/restore doesn't support overlapping slices and will fail.
	var combinedVV buffer.VectorisedView
	if e.TransportEndpointInfo.NetProto == header.IPv4ProtocolNumber {
	network, transport := pkt.NetworkHeader().View(), pkt.TransportHeader().View()
	headers := make(buffer.View, 0, len(network)+len(transport))
	headers = append(headers, network...)
	headers = append(headers, transport...)
	combinedVV = headers.ToVectorisedView()
	} else {
	combinedVV = append(buffer.View(nil), pkt.TransportHeader().View()...).ToVectorisedView()
	}
	combinedVV.Append(pkt.Data().ExtractVV())
	packet.data = combinedVV
	packet.timestampNS = e.stack.Clock().NowNanoseconds()

	e.rcvList.PushBack(packet)
	e.rcvBufSize += packet.data.Size()
	e.rcvMu.Unlock()
	e.mu.RUnlock()
	e.stats.PacketsReceived.Increment()
	// Notify waiters that there's data to be read.
	if wasEmpty {
	e.waiterQueue.Notify(waiter.EventIn)
	}
	}

	// State implements socket.Socket.State.
	func (e *endpoint) State() uint32 {
	return 0
	}

	// Info returns a copy of the endpoint info.
	func (e *endpoint) Info() tcpip.EndpointInfo {
	e.mu.RLock()
	// Make a copy of the endpoint info.
	ret := e.TransportEndpointInfo
	e.mu.RUnlock()
	return &ret
	}

	// Stats returns a pointer to the endpoint stats.
	func (e *endpoint) Stats() tcpip.EndpointStats {
	return &e.stats
	}

	// Wait implements stack.TransportEndpoint.Wait.
	func (*endpoint) Wait() {}

	// LastError implements tcpip.Endpoint.LastError.
	func (*endpoint) LastError() tcpip.Error {
	return nil
	}

	// SocketOptions implements tcpip.Endpoint.SocketOptions.
	func (e endpoint) SocketOptions() tcpip.SocketOptions {
	return &e.ops
	}