Merge 216da0b7 (automated)

6 files changed, 1601 insertions, 0 deletions

diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
new file mode 100644
index 000000000..3d52a4f31
--- /dev/null
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -0,0 +1,1002 @@
+// 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.
+
+package udp
+
+import (
+	"math"
+	"sync"
+
+	"gvisor.googlesource.com/gvisor/pkg/tcpip"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/header"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/stack"
+	"gvisor.googlesource.com/gvisor/pkg/waiter"
+)
+
+// +stateify savable
+type udpPacket struct {
+	udpPacketEntry
+	senderAddress tcpip.FullAddress
+	data          buffer.VectorisedView `state:".(buffer.VectorisedView)"`
+	timestamp     int64
+	// views is used as buffer for data when its length is large
+	// enough to store a VectorisedView.
+	views [8]buffer.View `state:"nosave"`
+}
+
+type endpointState int
+
+const (
+	stateInitial endpointState = iota
+	stateBound
+	stateConnected
+	stateClosed
+)
+
+// endpoint represents a UDP endpoint. This struct serves as the interface
+// between users of the endpoint and the protocol implementation; it is legal to
+// have concurrent goroutines make calls into the endpoint, they are properly
+// synchronized.
+//
+// It implements tcpip.Endpoint.
+//
+// +stateify savable
+type endpoint struct {
+	// The following fields are initialized at creation time and do not
+	// change throughout the lifetime of the endpoint.
+	stack       *stack.Stack `state:"manual"`
+	netProto    tcpip.NetworkProtocolNumber
+	waiterQueue *waiter.Queue
+
+	// The following fields are used to manage the receive queue, and are
+	// protected by rcvMu.
+	rcvMu         sync.Mutex `state:"nosave"`
+	rcvReady      bool
+	rcvList       udpPacketList
+	rcvBufSizeMax int `state:".(int)"`
+	rcvBufSize    int
+	rcvClosed     bool
+
+	// The following fields are protected by the mu mutex.
+	mu             sync.RWMutex `state:"nosave"`
+	sndBufSize     int
+	id             stack.TransportEndpointID
+	state          endpointState
+	bindNICID      tcpip.NICID
+	regNICID       tcpip.NICID
+	route          stack.Route `state:"manual"`
+	dstPort        uint16
+	v6only         bool
+	multicastTTL   uint8
+	multicastAddr  tcpip.Address
+	multicastNICID tcpip.NICID
+	multicastLoop  bool
+	reusePort      bool
+	broadcast      bool
+
+	// shutdownFlags represent the current shutdown state of the endpoint.
+	shutdownFlags tcpip.ShutdownFlags
+
+	// multicastMemberships that need to be remvoed when the endpoint is
+	// closed. Protected by the mu mutex.
+	multicastMemberships []multicastMembership
+
+	// effectiveNetProtos contains the network protocols actually in use. In
+	// most cases it will only contain "netProto", but in cases like IPv6
+	// endpoints with v6only set to false, this could include multiple
+	// protocols (e.g., IPv6 and IPv4) or a single different protocol (e.g.,
+	// IPv4 when IPv6 endpoint is bound or connected to an IPv4 mapped
+	// address).
+	effectiveNetProtos []tcpip.NetworkProtocolNumber
+}
+
+// +stateify savable
+type multicastMembership struct {
+	nicID         tcpip.NICID
+	multicastAddr tcpip.Address
+}
+
+func newEndpoint(stack *stack.Stack, netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) *endpoint {
+	return &endpoint{
+		stack:       stack,
+		netProto:    netProto,
+		waiterQueue: waiterQueue,
+		// RFC 1075 section 5.4 recommends a TTL of 1 for membership
+		// requests.
+		//
+		// RFC 5135 4.2.1 appears to assume that IGMP messages have a
+		// TTL of 1.
+		//
+		// RFC 5135 Appendix A defines TTL=1: A multicast source that
+		// wants its traffic to not traverse a router (e.g., leave a
+		// home network) may find it useful to send traffic with IP
+		// TTL=1.
+		//
+		// Linux defaults to TTL=1.
+		multicastTTL:  1,
+		multicastLoop: true,
+		rcvBufSizeMax: 32 * 1024,
+		sndBufSize:    32 * 1024,
+	}
+}
+
+// Close puts the endpoint in a closed state and frees all resources
+// associated with it.
+func (e *endpoint) Close() {
+	e.mu.Lock()
+	e.shutdownFlags = tcpip.ShutdownRead | tcpip.ShutdownWrite
+
+	switch e.state {
+	case stateBound, stateConnected:
+		e.stack.UnregisterTransportEndpoint(e.regNICID, e.effectiveNetProtos, ProtocolNumber, e.id, e)
+		e.stack.ReleasePort(e.effectiveNetProtos, ProtocolNumber, e.id.LocalAddress, e.id.LocalPort)
+	}
+
+	for _, mem := range e.multicastMemberships {
+		e.stack.LeaveGroup(e.netProto, mem.nicID, mem.multicastAddr)
+	}
+	e.multicastMemberships = nil
+
+	// Close the receive list and drain it.
+	e.rcvMu.Lock()
+	e.rcvClosed = true
+	e.rcvBufSize = 0
+	for !e.rcvList.Empty() {
+		p := e.rcvList.Front()
+		e.rcvList.Remove(p)
+	}
+	e.rcvMu.Unlock()
+
+	e.route.Release()
+
+	// Update the state.
+	e.state = stateClosed
+
+	e.mu.Unlock()
+
+	e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.EventIn | waiter.EventOut)
+}
+
+// Read reads data from the endpoint. This method does not block if
+// there is no data pending.
+func (e *endpoint) Read(addr *tcpip.FullAddress) (buffer.View, tcpip.ControlMessages, *tcpip.Error) {
+	e.rcvMu.Lock()
+
+	if e.rcvList.Empty() {
+		err := tcpip.ErrWouldBlock
+		if e.rcvClosed {
+			err = tcpip.ErrClosedForReceive
+		}
+		e.rcvMu.Unlock()
+		return buffer.View{}, tcpip.ControlMessages{}, err
+	}
+
+	p := e.rcvList.Front()
+	e.rcvList.Remove(p)
+	e.rcvBufSize -= p.data.Size()
+
+	e.rcvMu.Unlock()
+
+	if addr != nil {
+		*addr = p.senderAddress
+	}
+
+	return p.data.ToView(), tcpip.ControlMessages{HasTimestamp: true, Timestamp: p.timestamp}, nil
+}
+
+// prepareForWrite prepares the endpoint for sending data. In particular, it
+// binds it if it's still in the initial state. To do so, it must first
+// reacquire the mutex in exclusive mode.
+//
+// Returns true for retry if preparation should be retried.
+func (e *endpoint) prepareForWrite(to *tcpip.FullAddress) (retry bool, err *tcpip.Error) {
+	switch e.state {
+	case stateInitial:
+	case stateConnected:
+		return false, nil
+
+	case stateBound:
+		if to == nil {
+			return false, tcpip.ErrDestinationRequired
+		}
+		return false, nil
+	default:
+		return false, tcpip.ErrInvalidEndpointState
+	}
+
+	e.mu.RUnlock()
+	defer e.mu.RLock()
+
+	e.mu.Lock()
+	defer e.mu.Unlock()
+
+	// The state changed when we released the shared locked and re-acquired
+	// it in exclusive mode. Try again.
+	if e.state != stateInitial {
+		return true, nil
+	}
+
+	// The state is still 'initial', so try to bind the endpoint.
+	if err := e.bindLocked(tcpip.FullAddress{}); err != nil {
+		return false, err
+	}
+
+	return true, nil
+}
+
+// connectRoute establishes a route to the specified interface or the
+// configured multicast interface if no interface is specified and the
+// specified address is a multicast address.
+func (e *endpoint) connectRoute(nicid tcpip.NICID, addr tcpip.FullAddress) (stack.Route, tcpip.NICID, tcpip.NetworkProtocolNumber, *tcpip.Error) {
+	netProto, err := e.checkV4Mapped(&addr, false)
+	if err != nil {
+		return stack.Route{}, 0, 0, err
+	}
+
+	localAddr := e.id.LocalAddress
+	if header.IsV4MulticastAddress(addr.Addr) || header.IsV6MulticastAddress(addr.Addr) {
+		if nicid == 0 {
+			nicid = e.multicastNICID
+		}
+		if localAddr == "" {
+			localAddr = e.multicastAddr
+		}
+	}
+
+	// Find a route to the desired destination.
+	r, err := e.stack.FindRoute(nicid, localAddr, addr.Addr, netProto, e.multicastLoop)
+	if err != nil {
+		return stack.Route{}, 0, 0, err
+	}
+	return r, nicid, netProto, nil
+}
+
+// Write writes data to the endpoint's peer. This method does not block
+// if the data cannot be written.
+func (e *endpoint) Write(p tcpip.Payload, opts tcpip.WriteOptions) (uintptr, <-chan struct{}, *tcpip.Error) {
+	// MSG_MORE is unimplemented. (This also means that MSG_EOR is a no-op.)
+	if opts.More {
+		return 0, nil, tcpip.ErrInvalidOptionValue
+	}
+
+	if p.Size() > math.MaxUint16 {
+		// Payload can't possibly fit in a packet.
+		return 0, nil, tcpip.ErrMessageTooLong
+	}
+
+	to := opts.To
+
+	e.mu.RLock()
+	defer e.mu.RUnlock()
+
+	// If we've shutdown with SHUT_WR we are in an invalid state for sending.
+	if e.shutdownFlags&tcpip.ShutdownWrite != 0 {
+		return 0, nil, tcpip.ErrClosedForSend
+	}
+
+	// Prepare for write.
+	for {
+		retry, err := e.prepareForWrite(to)
+		if err != nil {
+			return 0, nil, err
+		}
+
+		if !retry {
+			break
+		}
+	}
+
+	var route *stack.Route
+	var dstPort uint16
+	if to == nil {
+		route = &e.route
+		dstPort = e.dstPort
+
+		if route.IsResolutionRequired() {
+			// Promote lock to exclusive if using a shared route, given that it may need to
+			// change in Route.Resolve() call below.
+			e.mu.RUnlock()
+			defer e.mu.RLock()
+
+			e.mu.Lock()
+			defer e.mu.Unlock()
+
+			// Recheck state after lock was re-acquired.
+			if e.state != stateConnected {
+				return 0, nil, tcpip.ErrInvalidEndpointState
+			}
+		}
+	} else {
+		// Reject destination address if it goes through a different
+		// NIC than the endpoint was bound to.
+		nicid := to.NIC
+		if e.bindNICID != 0 {
+			if nicid != 0 && nicid != e.bindNICID {
+				return 0, nil, tcpip.ErrNoRoute
+			}
+
+			nicid = e.bindNICID
+		}
+
+		if to.Addr == header.IPv4Broadcast && !e.broadcast {
+			return 0, nil, tcpip.ErrBroadcastDisabled
+		}
+
+		r, _, _, err := e.connectRoute(nicid, *to)
+		if err != nil {
+			return 0, nil, err
+		}
+		defer r.Release()
+
+		route = &r
+		dstPort = to.Port
+	}
+
+	if route.IsResolutionRequired() {
+		if ch, err := route.Resolve(nil); err != nil {
+			if err == tcpip.ErrWouldBlock {
+				return 0, ch, tcpip.ErrNoLinkAddress
+			}
+			return 0, nil, err
+		}
+	}
+
+	v, err := p.Get(p.Size())
+	if err != nil {
+		return 0, nil, err
+	}
+
+	ttl := route.DefaultTTL()
+	if header.IsV4MulticastAddress(route.RemoteAddress) || header.IsV6MulticastAddress(route.RemoteAddress) {
+		ttl = e.multicastTTL
+	}
+
+	if err := sendUDP(route, buffer.View(v).ToVectorisedView(), e.id.LocalPort, dstPort, ttl); err != nil {
+		return 0, nil, err
+	}
+	return uintptr(len(v)), nil, nil
+}
+
+// Peek only returns data from a single datagram, so do nothing here.
+func (e *endpoint) Peek([][]byte) (uintptr, tcpip.ControlMessages, *tcpip.Error) {
+	return 0, tcpip.ControlMessages{}, nil
+}
+
+// SetSockOpt sets a socket option. Currently not supported.
+func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
+	switch v := opt.(type) {
+	case tcpip.V6OnlyOption:
+		// We only recognize this option on v6 endpoints.
+		if e.netProto != header.IPv6ProtocolNumber {
+			return tcpip.ErrInvalidEndpointState
+		}
+
+		e.mu.Lock()
+		defer e.mu.Unlock()
+
+		// We only allow this to be set when we're in the initial state.
+		if e.state != stateInitial {
+			return tcpip.ErrInvalidEndpointState
+		}
+
+		e.v6only = v != 0
+
+	case tcpip.MulticastTTLOption:
+		e.mu.Lock()
+		e.multicastTTL = uint8(v)
+		e.mu.Unlock()
+
+	case tcpip.MulticastInterfaceOption:
+		e.mu.Lock()
+		defer e.mu.Unlock()
+
+		fa := tcpip.FullAddress{Addr: v.InterfaceAddr}
+		netProto, err := e.checkV4Mapped(&fa, false)
+		if err != nil {
+			return err
+		}
+		nic := v.NIC
+		addr := fa.Addr
+
+		if nic == 0 && addr == "" {
+			e.multicastAddr = ""
+			e.multicastNICID = 0
+			break
+		}
+
+		if nic != 0 {
+			if !e.stack.CheckNIC(nic) {
+				return tcpip.ErrBadLocalAddress
+			}
+		} else {
+			nic = e.stack.CheckLocalAddress(0, netProto, addr)
+			if nic == 0 {
+				return tcpip.ErrBadLocalAddress
+			}
+		}
+
+		if e.bindNICID != 0 && e.bindNICID != nic {
+			return tcpip.ErrInvalidEndpointState
+		}
+
+		e.multicastNICID = nic
+		e.multicastAddr = addr
+
+	case tcpip.AddMembershipOption:
+		if !header.IsV4MulticastAddress(v.MulticastAddr) && !header.IsV6MulticastAddress(v.MulticastAddr) {
+			return tcpip.ErrInvalidOptionValue
+		}
+
+		nicID := v.NIC
+		if v.InterfaceAddr == header.IPv4Any {
+			if nicID == 0 {
+				r, err := e.stack.FindRoute(0, "", v.MulticastAddr, header.IPv4ProtocolNumber, false /* multicastLoop */)
+				if err == nil {
+					nicID = r.NICID()
+					r.Release()
+				}
+			}
+		} else {
+			nicID = e.stack.CheckLocalAddress(nicID, e.netProto, v.InterfaceAddr)
+		}
+		if nicID == 0 {
+			return tcpip.ErrUnknownDevice
+		}
+
+		memToInsert := multicastMembership{nicID: nicID, multicastAddr: v.MulticastAddr}
+
+		e.mu.Lock()
+		defer e.mu.Unlock()
+
+		for _, mem := range e.multicastMemberships {
+			if mem == memToInsert {
+				return tcpip.ErrPortInUse
+			}
+		}
+
+		if err := e.stack.JoinGroup(e.netProto, nicID, v.MulticastAddr); err != nil {
+			return err
+		}
+
+		e.multicastMemberships = append(e.multicastMemberships, memToInsert)
+
+	case tcpip.RemoveMembershipOption:
+		if !header.IsV4MulticastAddress(v.MulticastAddr) && !header.IsV6MulticastAddress(v.MulticastAddr) {
+			return tcpip.ErrInvalidOptionValue
+		}
+
+		nicID := v.NIC
+		if v.InterfaceAddr == header.IPv4Any {
+			if nicID == 0 {
+				r, err := e.stack.FindRoute(0, "", v.MulticastAddr, header.IPv4ProtocolNumber, false /* multicastLoop */)
+				if err == nil {
+					nicID = r.NICID()
+					r.Release()
+				}
+			}
+		} else {
+			nicID = e.stack.CheckLocalAddress(nicID, e.netProto, v.InterfaceAddr)
+		}
+		if nicID == 0 {
+			return tcpip.ErrUnknownDevice
+		}
+
+		memToRemove := multicastMembership{nicID: nicID, multicastAddr: v.MulticastAddr}
+		memToRemoveIndex := -1
+
+		e.mu.Lock()
+		defer e.mu.Unlock()
+
+		for i, mem := range e.multicastMemberships {
+			if mem == memToRemove {
+				memToRemoveIndex = i
+				break
+			}
+		}
+		if memToRemoveIndex == -1 {
+			return tcpip.ErrBadLocalAddress
+		}
+
+		if err := e.stack.LeaveGroup(e.netProto, nicID, v.MulticastAddr); err != nil {
+			return err
+		}
+
+		e.multicastMemberships[memToRemoveIndex] = e.multicastMemberships[len(e.multicastMemberships)-1]
+		e.multicastMemberships = e.multicastMemberships[:len(e.multicastMemberships)-1]
+
+	case tcpip.MulticastLoopOption:
+		e.mu.Lock()
+		e.multicastLoop = bool(v)
+		e.mu.Unlock()
+
+	case tcpip.ReusePortOption:
+		e.mu.Lock()
+		e.reusePort = v != 0
+		e.mu.Unlock()
+
+	case tcpip.BroadcastOption:
+		e.mu.Lock()
+		e.broadcast = v != 0
+		e.mu.Unlock()
+
+		return nil
+	}
+	return nil
+}
+
+// GetSockOpt implements tcpip.Endpoint.GetSockOpt.
+func (e *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
+	switch o := opt.(type) {
+	case tcpip.ErrorOption:
+		return nil
+
+	case *tcpip.SendBufferSizeOption:
+		e.mu.Lock()
+		*o = tcpip.SendBufferSizeOption(e.sndBufSize)
+		e.mu.Unlock()
+		return nil
+
+	case *tcpip.ReceiveBufferSizeOption:
+		e.rcvMu.Lock()
+		*o = tcpip.ReceiveBufferSizeOption(e.rcvBufSizeMax)
+		e.rcvMu.Unlock()
+		return nil
+
+	case *tcpip.V6OnlyOption:
+		// We only recognize this option on v6 endpoints.
+		if e.netProto != header.IPv6ProtocolNumber {
+			return tcpip.ErrUnknownProtocolOption
+		}
+
+		e.mu.Lock()
+		v := e.v6only
+		e.mu.Unlock()
+
+		*o = 0
+		if v {
+			*o = 1
+		}
+		return nil
+
+	case *tcpip.ReceiveQueueSizeOption:
+		e.rcvMu.Lock()
+		if e.rcvList.Empty() {
+			*o = 0
+		} else {
+			p := e.rcvList.Front()
+			*o = tcpip.ReceiveQueueSizeOption(p.data.Size())
+		}
+		e.rcvMu.Unlock()
+		return nil
+
+	case *tcpip.MulticastTTLOption:
+		e.mu.Lock()
+		*o = tcpip.MulticastTTLOption(e.multicastTTL)
+		e.mu.Unlock()
+		return nil
+
+	case *tcpip.MulticastInterfaceOption:
+		e.mu.Lock()
+		*o = tcpip.MulticastInterfaceOption{
+			e.multicastNICID,
+			e.multicastAddr,
+		}
+		e.mu.Unlock()
+		return nil
+
+	case *tcpip.MulticastLoopOption:
+		e.mu.RLock()
+		v := e.multicastLoop
+		e.mu.RUnlock()
+
+		*o = tcpip.MulticastLoopOption(v)
+		return nil
+
+	case *tcpip.ReusePortOption:
+		e.mu.RLock()
+		v := e.reusePort
+		e.mu.RUnlock()
+
+		*o = 0
+		if v {
+			*o = 1
+		}
+		return nil
+
+	case *tcpip.KeepaliveEnabledOption:
+		*o = 0
+		return nil
+
+	case *tcpip.BroadcastOption:
+		e.mu.RLock()
+		v := e.broadcast
+		e.mu.RUnlock()
+
+		*o = 0
+		if v {
+			*o = 1
+		}
+		return nil
+
+	default:
+		return tcpip.ErrUnknownProtocolOption
+	}
+}
+
+// sendUDP sends a UDP segment via the provided network endpoint and under the
+// provided identity.
+func sendUDP(r *stack.Route, data buffer.VectorisedView, localPort, remotePort uint16, ttl uint8) *tcpip.Error {
+	// Allocate a buffer for the UDP header.
+	hdr := buffer.NewPrependable(header.UDPMinimumSize + int(r.MaxHeaderLength()))
+
+	// Initialize the header.
+	udp := header.UDP(hdr.Prepend(header.UDPMinimumSize))
+
+	length := uint16(hdr.UsedLength() + data.Size())
+	udp.Encode(&header.UDPFields{
+		SrcPort: localPort,
+		DstPort: remotePort,
+		Length:  length,
+	})
+
+	// Only calculate the checksum if offloading isn't supported.
+	if r.Capabilities()&stack.CapabilityTXChecksumOffload == 0 {
+		xsum := r.PseudoHeaderChecksum(ProtocolNumber, length)
+		for _, v := range data.Views() {
+			xsum = header.Checksum(v, xsum)
+		}
+		udp.SetChecksum(^udp.CalculateChecksum(xsum))
+	}
+
+	// Track count of packets sent.
+	r.Stats().UDP.PacketsSent.Increment()
+
+	return r.WritePacket(nil /* gso */, hdr, data, ProtocolNumber, ttl)
+}
+
+func (e *endpoint) checkV4Mapped(addr *tcpip.FullAddress, allowMismatch bool) (tcpip.NetworkProtocolNumber, *tcpip.Error) {
+	netProto := e.netProto
+	if header.IsV4MappedAddress(addr.Addr) {
+		// Fail if using a v4 mapped address on a v6only endpoint.
+		if e.v6only {
+			return 0, tcpip.ErrNoRoute
+		}
+
+		netProto = header.IPv4ProtocolNumber
+		addr.Addr = addr.Addr[header.IPv6AddressSize-header.IPv4AddressSize:]
+		if addr.Addr == "\x00\x00\x00\x00" {
+			addr.Addr = ""
+		}
+
+		// Fail if we are bound to an IPv6 address.
+		if !allowMismatch && len(e.id.LocalAddress) == 16 {
+			return 0, tcpip.ErrNetworkUnreachable
+		}
+	}
+
+	// Fail if we're bound to an address length different from the one we're
+	// checking.
+	if l := len(e.id.LocalAddress); l != 0 && l != len(addr.Addr) {
+		return 0, tcpip.ErrInvalidEndpointState
+	}
+
+	return netProto, nil
+}
+
+// Connect connects the endpoint to its peer. Specifying a NIC is optional.
+func (e *endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error {
+	if addr.Port == 0 {
+		// We don't support connecting to port zero.
+		return tcpip.ErrInvalidEndpointState
+	}
+
+	e.mu.Lock()
+	defer e.mu.Unlock()
+
+	nicid := addr.NIC
+	var localPort uint16
+	switch e.state {
+	case stateInitial:
+	case stateBound, stateConnected:
+		localPort = e.id.LocalPort
+		if e.bindNICID == 0 {
+			break
+		}
+
+		if nicid != 0 && nicid != e.bindNICID {
+			return tcpip.ErrInvalidEndpointState
+		}
+
+		nicid = e.bindNICID
+	default:
+		return tcpip.ErrInvalidEndpointState
+	}
+
+	r, nicid, netProto, err := e.connectRoute(nicid, addr)
+	if err != nil {
+		return err
+	}
+	defer r.Release()
+
+	id := stack.TransportEndpointID{
+		LocalAddress:  r.LocalAddress,
+		LocalPort:     localPort,
+		RemotePort:    addr.Port,
+		RemoteAddress: r.RemoteAddress,
+	}
+
+	// Even if we're connected, this endpoint can still be used to send
+	// packets on a different network protocol, so we register both even if
+	// v6only is set to false and this is an ipv6 endpoint.
+	netProtos := []tcpip.NetworkProtocolNumber{netProto}
+	if netProto == header.IPv6ProtocolNumber && !e.v6only {
+		netProtos = []tcpip.NetworkProtocolNumber{
+			header.IPv4ProtocolNumber,
+			header.IPv6ProtocolNumber,
+		}
+	}
+
+	id, err = e.registerWithStack(nicid, netProtos, id)
+	if err != nil {
+		return err
+	}
+
+	// Remove the old registration.
+	if e.id.LocalPort != 0 {
+		e.stack.UnregisterTransportEndpoint(e.regNICID, e.effectiveNetProtos, ProtocolNumber, e.id, e)
+	}
+
+	e.id = id
+	e.route = r.Clone()
+	e.dstPort = addr.Port
+	e.regNICID = nicid
+	e.effectiveNetProtos = netProtos
+
+	e.state = stateConnected
+
+	e.rcvMu.Lock()
+	e.rcvReady = true
+	e.rcvMu.Unlock()
+
+	return nil
+}
+
+// ConnectEndpoint is not supported.
+func (*endpoint) ConnectEndpoint(tcpip.Endpoint) *tcpip.Error {
+	return tcpip.ErrInvalidEndpointState
+}
+
+// Shutdown closes the read and/or write end of the endpoint connection
+// to its peer.
+func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) *tcpip.Error {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+
+	// A socket in the bound state can still receive multicast messages,
+	// so we need to notify waiters on shutdown.
+	if e.state != stateBound && e.state != stateConnected {
+		return tcpip.ErrNotConnected
+	}
+
+	e.shutdownFlags |= flags
+
+	if flags&tcpip.ShutdownRead != 0 {
+		e.rcvMu.Lock()
+		wasClosed := e.rcvClosed
+		e.rcvClosed = true
+		e.rcvMu.Unlock()
+
+		if !wasClosed {
+			e.waiterQueue.Notify(waiter.EventIn)
+		}
+	}
+
+	return nil
+}
+
+// Listen is not supported by UDP, it just fails.
+func (*endpoint) Listen(int) *tcpip.Error {
+	return tcpip.ErrNotSupported
+}
+
+// Accept is not supported by UDP, it just fails.
+func (*endpoint) Accept() (tcpip.Endpoint, *waiter.Queue, *tcpip.Error) {
+	return nil, nil, tcpip.ErrNotSupported
+}
+
+func (e *endpoint) registerWithStack(nicid tcpip.NICID, netProtos []tcpip.NetworkProtocolNumber, id stack.TransportEndpointID) (stack.TransportEndpointID, *tcpip.Error) {
+	if e.id.LocalPort == 0 {
+		port, err := e.stack.ReservePort(netProtos, ProtocolNumber, id.LocalAddress, id.LocalPort, e.reusePort)
+		if err != nil {
+			return id, err
+		}
+		id.LocalPort = port
+	}
+
+	err := e.stack.RegisterTransportEndpoint(nicid, netProtos, ProtocolNumber, id, e, e.reusePort)
+	if err != nil {
+		e.stack.ReleasePort(netProtos, ProtocolNumber, id.LocalAddress, id.LocalPort)
+	}
+	return id, err
+}
+
+func (e *endpoint) bindLocked(addr tcpip.FullAddress) *tcpip.Error {
+	// Don't allow binding once endpoint is not in the initial state
+	// anymore.
+	if e.state != stateInitial {
+		return tcpip.ErrInvalidEndpointState
+	}
+
+	netProto, err := e.checkV4Mapped(&addr, true)
+	if err != nil {
+		return err
+	}
+
+	// Expand netProtos to include v4 and v6 if the caller is binding to a
+	// wildcard (empty) address, and this is an IPv6 endpoint with v6only
+	// set to false.
+	netProtos := []tcpip.NetworkProtocolNumber{netProto}
+	if netProto == header.IPv6ProtocolNumber && !e.v6only && addr.Addr == "" {
+		netProtos = []tcpip.NetworkProtocolNumber{
+			header.IPv6ProtocolNumber,
+			header.IPv4ProtocolNumber,
+		}
+	}
+
+	nicid := addr.NIC
+	if len(addr.Addr) != 0 {
+		// A local address was specified, verify that it's valid.
+		nicid = e.stack.CheckLocalAddress(addr.NIC, netProto, addr.Addr)
+		if nicid == 0 {
+			return tcpip.ErrBadLocalAddress
+		}
+	}
+
+	id := stack.TransportEndpointID{
+		LocalPort:    addr.Port,
+		LocalAddress: addr.Addr,
+	}
+	id, err = e.registerWithStack(nicid, netProtos, id)
+	if err != nil {
+		return err
+	}
+
+	e.id = id
+	e.regNICID = nicid
+	e.effectiveNetProtos = netProtos
+
+	// Mark endpoint as bound.
+	e.state = stateBound
+
+	e.rcvMu.Lock()
+	e.rcvReady = true
+	e.rcvMu.Unlock()
+
+	return nil
+}
+
+// Bind binds the endpoint to a specific local address and port.
+// Specifying a NIC is optional.
+func (e *endpoint) Bind(addr tcpip.FullAddress) *tcpip.Error {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+
+	err := e.bindLocked(addr)
+	if err != nil {
+		return err
+	}
+
+	// Save the effective NICID generated by bindLocked.
+	e.bindNICID = e.regNICID
+
+	return nil
+}
+
+// GetLocalAddress returns the address to which the endpoint is bound.
+func (e *endpoint) GetLocalAddress() (tcpip.FullAddress, *tcpip.Error) {
+	e.mu.RLock()
+	defer e.mu.RUnlock()
+
+	return tcpip.FullAddress{
+		NIC:  e.regNICID,
+		Addr: e.id.LocalAddress,
+		Port: e.id.LocalPort,
+	}, nil
+}
+
+// GetRemoteAddress returns the address to which the endpoint is connected.
+func (e *endpoint) GetRemoteAddress() (tcpip.FullAddress, *tcpip.Error) {
+	e.mu.RLock()
+	defer e.mu.RUnlock()
+
+	if e.state != stateConnected {
+		return tcpip.FullAddress{}, tcpip.ErrNotConnected
+	}
+
+	return tcpip.FullAddress{
+		NIC:  e.regNICID,
+		Addr: e.id.RemoteAddress,
+		Port: e.id.RemotePort,
+	}, nil
+}
+
+// Readiness returns the current readiness of the endpoint. For example, if
+// waiter.EventIn is set, the endpoint is immediately readable.
+func (e *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
+	// The endpoint is always writable.
+	result := waiter.EventOut & mask
+
+	// Determine if the endpoint is readable if requested.
+	if (mask & waiter.EventIn) != 0 {
+		e.rcvMu.Lock()
+		if !e.rcvList.Empty() || e.rcvClosed {
+			result |= waiter.EventIn
+		}
+		e.rcvMu.Unlock()
+	}
+
+	return result
+}
+
+// HandlePacket is called by the stack when new packets arrive to this transport
+// endpoint.
+func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, vv buffer.VectorisedView) {
+	// Get the header then trim it from the view.
+	hdr := header.UDP(vv.First())
+	if int(hdr.Length()) > vv.Size() {
+		// Malformed packet.
+		e.stack.Stats().UDP.MalformedPacketsReceived.Increment()
+		return
+	}
+
+	vv.TrimFront(header.UDPMinimumSize)
+
+	e.rcvMu.Lock()
+	e.stack.Stats().UDP.PacketsReceived.Increment()
+
+	// Drop the packet if our buffer is currently full.
+	if !e.rcvReady || e.rcvClosed || e.rcvBufSize >= e.rcvBufSizeMax {
+		e.stack.Stats().UDP.ReceiveBufferErrors.Increment()
+		e.rcvMu.Unlock()
+		return
+	}
+
+	wasEmpty := e.rcvBufSize == 0
+
+	// Push new packet into receive list and increment the buffer size.
+	pkt := &udpPacket{
+		senderAddress: tcpip.FullAddress{
+			NIC:  r.NICID(),
+			Addr: id.RemoteAddress,
+			Port: hdr.SourcePort(),
+		},
+	}
+	pkt.data = vv.Clone(pkt.views[:])
+	e.rcvList.PushBack(pkt)
+	e.rcvBufSize += vv.Size()
+
+	pkt.timestamp = e.stack.NowNanoseconds()
+
+	e.rcvMu.Unlock()
+
+	// Notify any waiters that there's data to be read now.
+	if wasEmpty {
+		e.waiterQueue.Notify(waiter.EventIn)
+	}
+}
+
+// HandleControlPacket implements stack.TransportEndpoint.HandleControlPacket.
+func (e *endpoint) HandleControlPacket(id stack.TransportEndpointID, typ stack.ControlType, extra uint32, vv buffer.VectorisedView) {
+}
diff --git a/pkg/tcpip/transport/udp/endpoint_state.go b/pkg/tcpip/transport/udp/endpoint_state.go
new file mode 100644
index 000000000..74e8e9fd5
--- /dev/null
+++ b/pkg/tcpip/transport/udp/endpoint_state.go
@@ -0,0 +1,112 @@
+// 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.
+
+package udp
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/tcpip"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/header"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/stack"
+)
+
+// saveData saves udpPacket.data field.
+func (u *udpPacket) saveData() buffer.VectorisedView {
+	// We cannot save u.data directly as u.data.views may alias to u.views,
+	// which is not allowed by state framework (in-struct pointer).
+	return u.data.Clone(nil)
+}
+
+// loadData loads udpPacket.data field.
+func (u *udpPacket) loadData(data buffer.VectorisedView) {
+	// NOTE: We cannot do the u.data = data.Clone(u.views[:]) optimization
+	// here because data.views is not guaranteed to be loaded by now. Plus,
+	// data.views will be allocated anyway so there really is little point
+	// of utilizing u.views for data.views.
+	u.data = data
+}
+
+// beforeSave is invoked by stateify.
+func (e *endpoint) beforeSave() {
+	// Stop incoming packets from being handled (and mutate endpoint state).
+	// The lock will be released after savercvBufSizeMax(), which would have
+	// saved e.rcvBufSizeMax and set it to 0 to continue blocking incoming
+	// packets.
+	e.rcvMu.Lock()
+}
+
+// saveRcvBufSizeMax is invoked by stateify.
+func (e *endpoint) saveRcvBufSizeMax() int {
+	max := e.rcvBufSizeMax
+	// Make sure no new packets will be handled regardless of the lock.
+	e.rcvBufSizeMax = 0
+	// Release the lock acquired in beforeSave() so regular endpoint closing
+	// logic can proceed after save.
+	e.rcvMu.Unlock()
+	return max
+}
+
+// loadRcvBufSizeMax is invoked by stateify.
+func (e *endpoint) loadRcvBufSizeMax(max int) {
+	e.rcvBufSizeMax = max
+}
+
+// afterLoad is invoked by stateify.
+func (e *endpoint) afterLoad() {
+	e.stack = stack.StackFromEnv
+
+	for _, m := range e.multicastMemberships {
+		if err := e.stack.JoinGroup(e.netProto, m.nicID, m.multicastAddr); err != nil {
+			panic(err)
+		}
+	}
+
+	if e.state != stateBound && e.state != stateConnected {
+		return
+	}
+
+	netProto := e.effectiveNetProtos[0]
+	// Connect() and bindLocked() both assert
+	//
+	//     netProto == header.IPv6ProtocolNumber
+	//
+	// before creating a multi-entry effectiveNetProtos.
+	if len(e.effectiveNetProtos) > 1 {
+		netProto = header.IPv6ProtocolNumber
+	}
+
+	var err *tcpip.Error
+	if e.state == stateConnected {
+		e.route, err = e.stack.FindRoute(e.regNICID, e.id.LocalAddress, e.id.RemoteAddress, netProto, e.multicastLoop)
+		if err != nil {
+			panic(*err)
+		}
+
+		e.id.LocalAddress = e.route.LocalAddress
+	} else if len(e.id.LocalAddress) != 0 { // stateBound
+		if e.stack.CheckLocalAddress(e.regNICID, netProto, e.id.LocalAddress) == 0 {
+			panic(tcpip.ErrBadLocalAddress)
+		}
+	}
+
+	// Our saved state had a port, but we don't actually have a
+	// reservation. We need to remove the port from our state, but still
+	// pass it to the reservation machinery.
+	id := e.id
+	e.id.LocalPort = 0
+	e.id, err = e.registerWithStack(e.regNICID, e.effectiveNetProtos, id)
+	if err != nil {
+		panic(*err)
+	}
+}
diff --git a/pkg/tcpip/transport/udp/forwarder.go b/pkg/tcpip/transport/udp/forwarder.go
new file mode 100644
index 000000000..25bdd2929
--- /dev/null
+++ b/pkg/tcpip/transport/udp/forwarder.go
@@ -0,0 +1,96 @@
+// 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 udp
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/tcpip"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/stack"
+	"gvisor.googlesource.com/gvisor/pkg/waiter"
+)
+
+// Forwarder is a session request forwarder, which allows clients to decide
+// what to do with a session request, for example: ignore it, or process it.
+//
+// The canonical way of using it is to pass the Forwarder.HandlePacket function
+// to stack.SetTransportProtocolHandler.
+type Forwarder struct {
+	handler func(*ForwarderRequest)
+
+	stack *stack.Stack
+}
+
+// NewForwarder allocates and initializes a new forwarder.
+func NewForwarder(s *stack.Stack, handler func(*ForwarderRequest)) *Forwarder {
+	return &Forwarder{
+		stack:   s,
+		handler: handler,
+	}
+}
+
+// HandlePacket handles all packets.
+//
+// This function is expected to be passed as an argument to the
+// stack.SetTransportProtocolHandler function.
+func (f *Forwarder) HandlePacket(r *stack.Route, id stack.TransportEndpointID, netHeader buffer.View, vv buffer.VectorisedView) bool {
+	f.handler(&ForwarderRequest{
+		stack: f.stack,
+		route: r,
+		id:    id,
+		vv:    vv,
+	})
+
+	return true
+}
+
+// ForwarderRequest represents a session request received by the forwarder and
+// passed to the client. Clients may optionally create an endpoint to represent
+// it via CreateEndpoint.
+type ForwarderRequest struct {
+	stack *stack.Stack
+	route *stack.Route
+	id    stack.TransportEndpointID
+	vv    buffer.VectorisedView
+}
+
+// ID returns the 4-tuple (src address, src port, dst address, dst port) that
+// represents the session request.
+func (r *ForwarderRequest) ID() stack.TransportEndpointID {
+	return r.id
+}
+
+// CreateEndpoint creates a connected UDP endpoint for the session request.
+func (r *ForwarderRequest) CreateEndpoint(queue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+	ep := newEndpoint(r.stack, r.route.NetProto, queue)
+	if err := r.stack.RegisterTransportEndpoint(r.route.NICID(), []tcpip.NetworkProtocolNumber{r.route.NetProto}, ProtocolNumber, r.id, ep, ep.reusePort); err != nil {
+		ep.Close()
+		return nil, err
+	}
+
+	ep.id = r.id
+	ep.route = r.route.Clone()
+	ep.dstPort = r.id.RemotePort
+	ep.regNICID = r.route.NICID()
+
+	ep.state = stateConnected
+
+	ep.rcvMu.Lock()
+	ep.rcvReady = true
+	ep.rcvMu.Unlock()
+
+	ep.HandlePacket(r.route, r.id, r.vv)
+
+	return ep, nil
+}
diff --git a/pkg/tcpip/transport/udp/protocol.go b/pkg/tcpip/transport/udp/protocol.go
new file mode 100644
index 000000000..3d31dfbf1
--- /dev/null
+++ b/pkg/tcpip/transport/udp/protocol.go
@@ -0,0 +1,90 @@
+// 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.
+
+// Package udp contains the implementation of the UDP transport protocol. To use
+// it in the networking stack, this package must be added to the project, and
+// activated on the stack by passing udp.ProtocolName (or "udp") as one of the
+// transport protocols when calling stack.New(). Then endpoints can be created
+// by passing udp.ProtocolNumber as the transport protocol number when calling
+// Stack.NewEndpoint().
+package udp
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/tcpip"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/header"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/stack"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/transport/raw"
+	"gvisor.googlesource.com/gvisor/pkg/waiter"
+)
+
+const (
+	// ProtocolName is the string representation of the udp protocol name.
+	ProtocolName = "udp"
+
+	// ProtocolNumber is the udp protocol number.
+	ProtocolNumber = header.UDPProtocolNumber
+)
+
+type protocol struct{}
+
+// Number returns the udp protocol number.
+func (*protocol) Number() tcpip.TransportProtocolNumber {
+	return ProtocolNumber
+}
+
+// NewEndpoint creates a new udp endpoint.
+func (*protocol) NewEndpoint(stack *stack.Stack, netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+	return newEndpoint(stack, netProto, waiterQueue), nil
+}
+
+// NewRawEndpoint creates a new raw UDP endpoint. It implements
+// stack.TransportProtocol.NewRawEndpoint.
+func (p *protocol) NewRawEndpoint(stack *stack.Stack, netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+	return raw.NewEndpoint(stack, netProto, header.UDPProtocolNumber, waiterQueue)
+}
+
+// MinimumPacketSize returns the minimum valid udp packet size.
+func (*protocol) MinimumPacketSize() int {
+	return header.UDPMinimumSize
+}
+
+// ParsePorts returns the source and destination ports stored in the given udp
+// packet.
+func (*protocol) ParsePorts(v buffer.View) (src, dst uint16, err *tcpip.Error) {
+	h := header.UDP(v)
+	return h.SourcePort(), h.DestinationPort(), nil
+}
+
+// HandleUnknownDestinationPacket handles packets targeted at this protocol but
+// that don't match any existing endpoint.
+func (p *protocol) HandleUnknownDestinationPacket(*stack.Route, stack.TransportEndpointID, buffer.VectorisedView) bool {
+	return true
+}
+
+// SetOption implements TransportProtocol.SetOption.
+func (p *protocol) SetOption(option interface{}) *tcpip.Error {
+	return tcpip.ErrUnknownProtocolOption
+}
+
+// Option implements TransportProtocol.Option.
+func (p *protocol) Option(option interface{}) *tcpip.Error {
+	return tcpip.ErrUnknownProtocolOption
+}
+
+func init() {
+	stack.RegisterTransportProtocolFactory(ProtocolName, func() stack.TransportProtocol {
+		return &protocol{}
+	})
+}
diff --git a/pkg/tcpip/transport/udp/udp_packet_list.go b/pkg/tcpip/transport/udp/udp_packet_list.go
new file mode 100755
index 000000000..673a9373b
--- /dev/null
+++ b/pkg/tcpip/transport/udp/udp_packet_list.go
@@ -0,0 +1,173 @@
+package udp
+
+// ElementMapper provides an identity mapping by default.
+//
+// This can be replaced to provide a struct that maps elements to linker
+// objects, if they are not the same. An ElementMapper is not typically
+// required if: Linker is left as is, Element is left as is, or Linker and
+// Element are the same type.
+type udpPacketElementMapper struct{}
+
+// linkerFor maps an Element to a Linker.
+//
+// This default implementation should be inlined.
+//
+//go:nosplit
+func (udpPacketElementMapper) linkerFor(elem *udpPacket) *udpPacket { return elem }
+
+// List is an intrusive list. Entries can be added to or removed from the list
+// in O(1) time and with no additional memory allocations.
+//
+// The zero value for List is an empty list ready to use.
+//
+// To iterate over a list (where l is a List):
+//      for e := l.Front(); e != nil; e = e.Next() {
+// 		// do something with e.
+//      }
+//
+// +stateify savable
+type udpPacketList struct {
+	head *udpPacket
+	tail *udpPacket
+}
+
+// Reset resets list l to the empty state.
+func (l *udpPacketList) Reset() {
+	l.head = nil
+	l.tail = nil
+}
+
+// Empty returns true iff the list is empty.
+func (l *udpPacketList) Empty() bool {
+	return l.head == nil
+}
+
+// Front returns the first element of list l or nil.
+func (l *udpPacketList) Front() *udpPacket {
+	return l.head
+}
+
+// Back returns the last element of list l or nil.
+func (l *udpPacketList) Back() *udpPacket {
+	return l.tail
+}
+
+// PushFront inserts the element e at the front of list l.
+func (l *udpPacketList) PushFront(e *udpPacket) {
+	udpPacketElementMapper{}.linkerFor(e).SetNext(l.head)
+	udpPacketElementMapper{}.linkerFor(e).SetPrev(nil)
+
+	if l.head != nil {
+		udpPacketElementMapper{}.linkerFor(l.head).SetPrev(e)
+	} else {
+		l.tail = e
+	}
+
+	l.head = e
+}
+
+// PushBack inserts the element e at the back of list l.
+func (l *udpPacketList) PushBack(e *udpPacket) {
+	udpPacketElementMapper{}.linkerFor(e).SetNext(nil)
+	udpPacketElementMapper{}.linkerFor(e).SetPrev(l.tail)
+
+	if l.tail != nil {
+		udpPacketElementMapper{}.linkerFor(l.tail).SetNext(e)
+	} else {
+		l.head = e
+	}
+
+	l.tail = e
+}
+
+// PushBackList inserts list m at the end of list l, emptying m.
+func (l *udpPacketList) PushBackList(m *udpPacketList) {
+	if l.head == nil {
+		l.head = m.head
+		l.tail = m.tail
+	} else if m.head != nil {
+		udpPacketElementMapper{}.linkerFor(l.tail).SetNext(m.head)
+		udpPacketElementMapper{}.linkerFor(m.head).SetPrev(l.tail)
+
+		l.tail = m.tail
+	}
+
+	m.head = nil
+	m.tail = nil
+}
+
+// InsertAfter inserts e after b.
+func (l *udpPacketList) InsertAfter(b, e *udpPacket) {
+	a := udpPacketElementMapper{}.linkerFor(b).Next()
+	udpPacketElementMapper{}.linkerFor(e).SetNext(a)
+	udpPacketElementMapper{}.linkerFor(e).SetPrev(b)
+	udpPacketElementMapper{}.linkerFor(b).SetNext(e)
+
+	if a != nil {
+		udpPacketElementMapper{}.linkerFor(a).SetPrev(e)
+	} else {
+		l.tail = e
+	}
+}
+
+// InsertBefore inserts e before a.
+func (l *udpPacketList) InsertBefore(a, e *udpPacket) {
+	b := udpPacketElementMapper{}.linkerFor(a).Prev()
+	udpPacketElementMapper{}.linkerFor(e).SetNext(a)
+	udpPacketElementMapper{}.linkerFor(e).SetPrev(b)
+	udpPacketElementMapper{}.linkerFor(a).SetPrev(e)
+
+	if b != nil {
+		udpPacketElementMapper{}.linkerFor(b).SetNext(e)
+	} else {
+		l.head = e
+	}
+}
+
+// Remove removes e from l.
+func (l *udpPacketList) Remove(e *udpPacket) {
+	prev := udpPacketElementMapper{}.linkerFor(e).Prev()
+	next := udpPacketElementMapper{}.linkerFor(e).Next()
+
+	if prev != nil {
+		udpPacketElementMapper{}.linkerFor(prev).SetNext(next)
+	} else {
+		l.head = next
+	}
+
+	if next != nil {
+		udpPacketElementMapper{}.linkerFor(next).SetPrev(prev)
+	} else {
+		l.tail = prev
+	}
+}
+
+// Entry is a default implementation of Linker. Users can add anonymous fields
+// of this type to their structs to make them automatically implement the
+// methods needed by List.
+//
+// +stateify savable
+type udpPacketEntry struct {
+	next *udpPacket
+	prev *udpPacket
+}
+
+// Next returns the entry that follows e in the list.
+func (e *udpPacketEntry) Next() *udpPacket {
+	return e.next
+}
+
+// Prev returns the entry that precedes e in the list.
+func (e *udpPacketEntry) Prev() *udpPacket {
+	return e.prev
+}
+
+// SetNext assigns 'entry' as the entry that follows e in the list.
+func (e *udpPacketEntry) SetNext(elem *udpPacket) {
+	e.next = elem
+}
+
+// SetPrev assigns 'entry' as the entry that precedes e in the list.
+func (e *udpPacketEntry) SetPrev(elem *udpPacket) {
+	e.prev = elem
+}
diff --git a/pkg/tcpip/transport/udp/udp_state_autogen.go b/pkg/tcpip/transport/udp/udp_state_autogen.go
new file mode 100755
index 000000000..711e2feeb
--- /dev/null
+++ b/pkg/tcpip/transport/udp/udp_state_autogen.go
@@ -0,0 +1,128 @@
+// automatically generated by stateify.
+
+package udp
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/state"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
+)
+
+func (x *udpPacket) beforeSave() {}
+func (x *udpPacket) save(m state.Map) {
+	x.beforeSave()
+	var data buffer.VectorisedView = x.saveData()
+	m.SaveValue("data", data)
+	m.Save("udpPacketEntry", &x.udpPacketEntry)
+	m.Save("senderAddress", &x.senderAddress)
+	m.Save("timestamp", &x.timestamp)
+}
+
+func (x *udpPacket) afterLoad() {}
+func (x *udpPacket) load(m state.Map) {
+	m.Load("udpPacketEntry", &x.udpPacketEntry)
+	m.Load("senderAddress", &x.senderAddress)
+	m.Load("timestamp", &x.timestamp)
+	m.LoadValue("data", new(buffer.VectorisedView), func(y interface{}) { x.loadData(y.(buffer.VectorisedView)) })
+}
+
+func (x *endpoint) save(m state.Map) {
+	x.beforeSave()
+	var rcvBufSizeMax int = x.saveRcvBufSizeMax()
+	m.SaveValue("rcvBufSizeMax", rcvBufSizeMax)
+	m.Save("netProto", &x.netProto)
+	m.Save("waiterQueue", &x.waiterQueue)
+	m.Save("rcvReady", &x.rcvReady)
+	m.Save("rcvList", &x.rcvList)
+	m.Save("rcvBufSize", &x.rcvBufSize)
+	m.Save("rcvClosed", &x.rcvClosed)
+	m.Save("sndBufSize", &x.sndBufSize)
+	m.Save("id", &x.id)
+	m.Save("state", &x.state)
+	m.Save("bindNICID", &x.bindNICID)
+	m.Save("regNICID", &x.regNICID)
+	m.Save("dstPort", &x.dstPort)
+	m.Save("v6only", &x.v6only)
+	m.Save("multicastTTL", &x.multicastTTL)
+	m.Save("multicastAddr", &x.multicastAddr)
+	m.Save("multicastNICID", &x.multicastNICID)
+	m.Save("multicastLoop", &x.multicastLoop)
+	m.Save("reusePort", &x.reusePort)
+	m.Save("broadcast", &x.broadcast)
+	m.Save("shutdownFlags", &x.shutdownFlags)
+	m.Save("multicastMemberships", &x.multicastMemberships)
+	m.Save("effectiveNetProtos", &x.effectiveNetProtos)
+}
+
+func (x *endpoint) load(m state.Map) {
+	m.Load("netProto", &x.netProto)
+	m.Load("waiterQueue", &x.waiterQueue)
+	m.Load("rcvReady", &x.rcvReady)
+	m.Load("rcvList", &x.rcvList)
+	m.Load("rcvBufSize", &x.rcvBufSize)
+	m.Load("rcvClosed", &x.rcvClosed)
+	m.Load("sndBufSize", &x.sndBufSize)
+	m.Load("id", &x.id)
+	m.Load("state", &x.state)
+	m.Load("bindNICID", &x.bindNICID)
+	m.Load("regNICID", &x.regNICID)
+	m.Load("dstPort", &x.dstPort)
+	m.Load("v6only", &x.v6only)
+	m.Load("multicastTTL", &x.multicastTTL)
+	m.Load("multicastAddr", &x.multicastAddr)
+	m.Load("multicastNICID", &x.multicastNICID)
+	m.Load("multicastLoop", &x.multicastLoop)
+	m.Load("reusePort", &x.reusePort)
+	m.Load("broadcast", &x.broadcast)
+	m.Load("shutdownFlags", &x.shutdownFlags)
+	m.Load("multicastMemberships", &x.multicastMemberships)
+	m.Load("effectiveNetProtos", &x.effectiveNetProtos)
+	m.LoadValue("rcvBufSizeMax", new(int), func(y interface{}) { x.loadRcvBufSizeMax(y.(int)) })
+	m.AfterLoad(x.afterLoad)
+}
+
+func (x *multicastMembership) beforeSave() {}
+func (x *multicastMembership) save(m state.Map) {
+	x.beforeSave()
+	m.Save("nicID", &x.nicID)
+	m.Save("multicastAddr", &x.multicastAddr)
+}
+
+func (x *multicastMembership) afterLoad() {}
+func (x *multicastMembership) load(m state.Map) {
+	m.Load("nicID", &x.nicID)
+	m.Load("multicastAddr", &x.multicastAddr)
+}
+
+func (x *udpPacketList) beforeSave() {}
+func (x *udpPacketList) save(m state.Map) {
+	x.beforeSave()
+	m.Save("head", &x.head)
+	m.Save("tail", &x.tail)
+}
+
+func (x *udpPacketList) afterLoad() {}
+func (x *udpPacketList) load(m state.Map) {
+	m.Load("head", &x.head)
+	m.Load("tail", &x.tail)
+}
+
+func (x *udpPacketEntry) beforeSave() {}
+func (x *udpPacketEntry) save(m state.Map) {
+	x.beforeSave()
+	m.Save("next", &x.next)
+	m.Save("prev", &x.prev)
+}
+
+func (x *udpPacketEntry) afterLoad() {}
+func (x *udpPacketEntry) load(m state.Map) {
+	m.Load("next", &x.next)
+	m.Load("prev", &x.prev)
+}
+
+func init() {
+	state.Register("udp.udpPacket", (*udpPacket)(nil), state.Fns{Save: (*udpPacket).save, Load: (*udpPacket).load})
+	state.Register("udp.endpoint", (*endpoint)(nil), state.Fns{Save: (*endpoint).save, Load: (*endpoint).load})
+	state.Register("udp.multicastMembership", (*multicastMembership)(nil), state.Fns{Save: (*multicastMembership).save, Load: (*multicastMembership).load})
+	state.Register("udp.udpPacketList", (*udpPacketList)(nil), state.Fns{Save: (*udpPacketList).save, Load: (*udpPacketList).load})
+	state.Register("udp.udpPacketEntry", (*udpPacketEntry)(nil), state.Fns{Save: (*udpPacketEntry).save, Load: (*udpPacketEntry).load})
+}