Define tcpip.Payloader in terms of io.Reader

Fixes #1509.

PiperOrigin-RevId: 353295589

30 files changed, 372 insertions, 373 deletions

diff --git a/pkg/sentry/kernel/task_block.go b/pkg/sentry/kernel/task_block.go
index 9419f2e95..ecbe8f920 100644
--- a/pkg/sentry/kernel/task_block.go
+++ b/pkg/sentry/kernel/task_block.go
@@ -69,7 +69,7 @@ func (t *Task) BlockWithTimeout(C chan struct{}, haveTimeout bool, timeout time.
 // syserror.ErrInterrupted if t is interrupted.
 //
 // Preconditions: The caller must be running on the task goroutine.
-func (t *Task) BlockWithDeadline(C chan struct{}, haveDeadline bool, deadline ktime.Time) error {
+func (t *Task) BlockWithDeadline(C <-chan struct{}, haveDeadline bool, deadline ktime.Time) error {
 	if !haveDeadline {
 		return t.block(C, nil)
 	}
diff --git a/pkg/sentry/socket/netstack/BUILD b/pkg/sentry/socket/netstack/BUILD
index f820467c5..915134b41 100644
--- a/pkg/sentry/socket/netstack/BUILD
+++ b/pkg/sentry/socket/netstack/BUILD
@@ -41,7 +41,6 @@ go_library(
         "//pkg/syserr",
         "//pkg/syserror",
         "//pkg/tcpip",
-        "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
         "//pkg/tcpip/network/ipv4",
         "//pkg/tcpip/network/ipv6",
diff --git a/pkg/sentry/socket/netstack/netstack.go b/pkg/sentry/socket/netstack/netstack.go
index 4c9d335c0..65111154b 100644
--- a/pkg/sentry/socket/netstack/netstack.go
+++ b/pkg/sentry/socket/netstack/netstack.go
@@ -19,7 +19,7 @@
 // be used to expose certain endpoints to the sentry while leaving others out,
 // for example, TCP endpoints and Unix-domain endpoints.
 //
-// Lock ordering: netstack => mm: ioSequencePayload copies user memory inside
+// Lock ordering: netstack => mm: ioSequenceReadWriter copies user memory inside
 // tcpip.Endpoint.Write(). Netstack is allowed to (and does) hold locks during
 // this operation.
 package netstack
@@ -55,7 +55,6 @@ import (
 	"gvisor.dev/gvisor/pkg/syserr"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"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/tcpip/transport/tcp"
@@ -440,45 +439,10 @@ func (s *SocketOperations) WriteTo(ctx context.Context, _ *fs.File, dst io.Write
 	return int64(res.Count), nil
 }
 
-// ioSequencePayload implements tcpip.Payload.
-//
-// t copies user memory bytes on demand based on the requested size.
-type ioSequencePayload struct {
-	ctx context.Context
-	src usermem.IOSequence
-}
-
-// FullPayload implements tcpip.Payloader.FullPayload
-func (i *ioSequencePayload) FullPayload() ([]byte, *tcpip.Error) {
-	return i.Payload(int(i.src.NumBytes()))
-}
-
-// Payload implements tcpip.Payloader.Payload.
-func (i *ioSequencePayload) Payload(size int) ([]byte, *tcpip.Error) {
-	if max := int(i.src.NumBytes()); size > max {
-		size = max
-	}
-	v := buffer.NewView(size)
-	if _, err := i.src.CopyIn(i.ctx, v); err != nil {
-		// EOF can be returned only if src is a file and this means it
-		// is in a splice syscall and the error has to be ignored.
-		if err == io.EOF {
-			return v, nil
-		}
-		return nil, tcpip.ErrBadAddress
-	}
-	return v, nil
-}
-
-// DropFirst drops the first n bytes from underlying src.
-func (i *ioSequencePayload) DropFirst(n int) {
-	i.src = i.src.DropFirst(int(n))
-}
-
 // Write implements fs.FileOperations.Write.
 func (s *SocketOperations) Write(ctx context.Context, _ *fs.File, src usermem.IOSequence, _ int64) (int64, error) {
-	f := &ioSequencePayload{ctx: ctx, src: src}
-	n, err := s.Endpoint.Write(f, tcpip.WriteOptions{})
+	r := src.Reader(ctx)
+	n, err := s.Endpoint.Write(r, tcpip.WriteOptions{})
 	if err == tcpip.ErrWouldBlock {
 		return 0, syserror.ErrWouldBlock
 	}
@@ -486,69 +450,40 @@ func (s *SocketOperations) Write(ctx context.Context, _ *fs.File, src usermem.IO
 		return 0, syserr.TranslateNetstackError(err).ToError()
 	}
 
-	if int64(n) < src.NumBytes() {
-		return int64(n), syserror.ErrWouldBlock
+	if n < src.NumBytes() {
+		return n, syserror.ErrWouldBlock
 	}
 
-	return int64(n), nil
+	return n, nil
 }
 
-// readerPayload implements tcpip.Payloader.
-//
-// It allocates a view and reads from a reader on-demand, based on available
-// capacity in the endpoint.
-type readerPayload struct {
-	ctx   context.Context
-	r     io.Reader
-	count int64
-	err   error
-}
+var _ tcpip.Payloader = (*limitedPayloader)(nil)
 
-// FullPayload implements tcpip.Payloader.FullPayload.
-func (r *readerPayload) FullPayload() ([]byte, *tcpip.Error) {
-	return r.Payload(int(r.count))
+type limitedPayloader struct {
+	io.LimitedReader
 }
 
-// Payload implements tcpip.Payloader.Payload.
-func (r *readerPayload) Payload(size int) ([]byte, *tcpip.Error) {
-	if size > int(r.count) {
-		size = int(r.count)
-	}
-	v := buffer.NewView(size)
-	n, err := r.r.Read(v)
-	if n > 0 {
-		// We ignore the error here. It may re-occur on subsequent
-		// reads, but for now we can enqueue some amount of data.
-		r.count -= int64(n)
-		return v[:n], nil
-	}
-	if err == syserror.ErrWouldBlock {
-		return nil, tcpip.ErrWouldBlock
-	} else if err != nil {
-		r.err = err // Save for propation.
-		return nil, tcpip.ErrBadAddress
-	}
-
-	// There is no data and no error. Return an error, which will propagate
-	// r.err, which will be nil. This is the desired result: (0, nil).
-	return nil, tcpip.ErrBadAddress
+func (l limitedPayloader) Len() int {
+	return int(l.N)
 }
 
 // ReadFrom implements fs.FileOperations.ReadFrom.
 func (s *SocketOperations) ReadFrom(ctx context.Context, _ *fs.File, r io.Reader, count int64) (int64, error) {
-	f := &readerPayload{ctx: ctx, r: r, count: count}
-	n, err := s.Endpoint.Write(f, tcpip.WriteOptions{
+	f := limitedPayloader{
+		LimitedReader: io.LimitedReader{
+			R: r,
+			N: count,
+		},
+	}
+	n, err := s.Endpoint.Write(&f, tcpip.WriteOptions{
 		// Reads may be destructive but should be very fast,
 		// so we can't release the lock while copying data.
 		Atomic: true,
 	})
-	if err == tcpip.ErrWouldBlock {
-		return n, syserror.ErrWouldBlock
-	} else if err != nil {
-		return int64(n), f.err // Propagate error.
+	if err == tcpip.ErrBadBuffer {
+		err = nil
 	}
-
-	return int64(n), nil
+	return n, syserr.TranslateNetstackError(err).ToError()
 }
 
 // Readiness returns a mask of ready events for socket s.
@@ -2836,45 +2771,46 @@ func (s *socketOpsCommon) SendMsg(t *kernel.Task, src usermem.IOSequence, to []b
 		EndOfRecord: flags&linux.MSG_EOR != 0,
 	}
 
-	v := &ioSequencePayload{t, src}
-	n, err := s.Endpoint.Write(v, opts)
-	dontWait := flags&linux.MSG_DONTWAIT != 0
-	if err == nil && (n >= v.src.NumBytes() || dontWait) {
-		// Complete write.
-		return int(n), nil
-	}
-	if err != nil && (err != tcpip.ErrWouldBlock || dontWait) {
-		return int(n), syserr.TranslateNetstackError(err)
-	}
-
-	// We'll have to block. Register for notification and keep trying to
-	// send all the data.
-	e, ch := waiter.NewChannelEntry(nil)
-	s.EventRegister(&e, waiter.EventOut)
-	defer s.EventUnregister(&e)
-
-	v.DropFirst(int(n))
-	total := n
+	r := src.Reader(t)
+	var (
+		total int64
+		entry waiter.Entry
+		ch    <-chan struct{}
+	)
 	for {
-		n, err = s.Endpoint.Write(v, opts)
-		v.DropFirst(int(n))
+		n, err := s.Endpoint.Write(r, opts)
 		total += n
-
-		if err != nil && err != tcpip.ErrWouldBlock && total == 0 {
-			return 0, syserr.TranslateNetstackError(err)
-		}
-
-		if err == nil && v.src.NumBytes() == 0 || err != nil && err != tcpip.ErrWouldBlock {
-			return int(total), nil
+		if flags&linux.MSG_DONTWAIT != 0 {
+			return int(total), syserr.TranslateNetstackError(err)
 		}
-
-		if err := t.BlockWithDeadline(ch, haveDeadline, deadline); err != nil {
-			if err == syserror.ETIMEDOUT {
-				return int(total), syserr.ErrTryAgain
+		switch err {
+		case nil:
+			if total == src.NumBytes() {
+				break
+			}
+			fallthrough
+		case tcpip.ErrWouldBlock:
+			if ch == nil {
+				// We'll have to block. Register for notification and keep trying to
+				// send all the data.
+				entry, ch = waiter.NewChannelEntry(nil)
+				s.EventRegister(&entry, waiter.EventOut)
+				defer s.EventUnregister(&entry)
+			} else {
+				// Don't wait immediately after registration in case more data
+				// became available between when we last checked and when we setup
+				// the notification.
+				if err := t.BlockWithDeadline(ch, haveDeadline, deadline); err != nil {
+					if err == syserror.ETIMEDOUT {
+						return int(total), syserr.ErrTryAgain
+					}
+					// handleIOError will consume errors from t.Block if needed.
+					return int(total), syserr.FromError(err)
+				}
 			}
-			// handleIOError will consume errors from t.Block if needed.
-			return int(total), syserr.FromError(err)
+			continue
 		}
+		return int(total), syserr.TranslateNetstackError(err)
 	}
 }
 
diff --git a/pkg/sentry/socket/netstack/netstack_vfs2.go b/pkg/sentry/socket/netstack/netstack_vfs2.go
index 9600a64e1..3bbdf552e 100644
--- a/pkg/sentry/socket/netstack/netstack_vfs2.go
+++ b/pkg/sentry/socket/netstack/netstack_vfs2.go
@@ -128,8 +128,8 @@ func (s *SocketVFS2) Write(ctx context.Context, src usermem.IOSequence, opts vfs
 		return 0, syserror.EOPNOTSUPP
 	}
 
-	f := &ioSequencePayload{ctx: ctx, src: src}
-	n, err := s.Endpoint.Write(f, tcpip.WriteOptions{})
+	r := src.Reader(ctx)
+	n, err := s.Endpoint.Write(r, tcpip.WriteOptions{})
 	if err == tcpip.ErrWouldBlock {
 		return 0, syserror.ErrWouldBlock
 	}
@@ -137,11 +137,11 @@ func (s *SocketVFS2) Write(ctx context.Context, src usermem.IOSequence, opts vfs
 		return 0, syserr.TranslateNetstackError(err).ToError()
 	}
 
-	if int64(n) < src.NumBytes() {
-		return int64(n), syserror.ErrWouldBlock
+	if n < src.NumBytes() {
+		return n, syserror.ErrWouldBlock
 	}
 
-	return int64(n), nil
+	return n, nil
 }
 
 // Accept implements the linux syscall accept(2) for sockets backed by
diff --git a/pkg/tcpip/adapters/gonet/gonet.go b/pkg/tcpip/adapters/gonet/gonet.go
index fdeec12d3..7c7495c30 100644
--- a/pkg/tcpip/adapters/gonet/gonet.go
+++ b/pkg/tcpip/adapters/gonet/gonet.go
@@ -16,6 +16,7 @@
 package gonet
 
 import (
+	"bytes"
 	"context"
 	"errors"
 	"io"
@@ -354,8 +355,6 @@ func (c *TCPConn) Write(b []byte) (int, error) {
 	default:
 	}
 
-	v := buffer.NewViewFromBytes(b)
-
 	// We must handle two soft failure conditions simultaneously:
 	//  1. Write may write nothing and return tcpip.ErrWouldBlock.
 	//     If this happens, we need to register for notifications if we have
@@ -368,22 +367,23 @@ func (c *TCPConn) Write(b []byte) (int, error) {
 	// There is no guarantee that all of the condition #1s will occur before
 	// all of the condition #2s or visa-versa.
 	var (
-		err      *tcpip.Error
-		nbytes   int
-		reg      bool
-		notifyCh chan struct{}
+		r      bytes.Reader
+		nbytes int
+		entry  waiter.Entry
+		ch     <-chan struct{}
 	)
-	for nbytes < len(b) && (err == tcpip.ErrWouldBlock || err == nil) {
-		if err == tcpip.ErrWouldBlock {
-			if !reg {
-				// Only register once.
-				reg = true
-
-				// Create wait queue entry that notifies a channel.
-				var waitEntry waiter.Entry
-				waitEntry, notifyCh = waiter.NewChannelEntry(nil)
-				c.wq.EventRegister(&waitEntry, waiter.EventOut)
-				defer c.wq.EventUnregister(&waitEntry)
+	for nbytes != len(b) {
+		r.Reset(b[nbytes:])
+		n, err := c.ep.Write(&r, tcpip.WriteOptions{})
+		nbytes += int(n)
+		switch err {
+		case nil:
+		case tcpip.ErrWouldBlock:
+			if ch == nil {
+				entry, ch = waiter.NewChannelEntry(nil)
+
+				c.wq.EventRegister(&entry, waiter.EventOut)
+				defer c.wq.EventUnregister(&entry)
 			} else {
 				// Don't wait immediately after registration in case more data
 				// became available between when we last checked and when we setup
@@ -391,22 +391,15 @@ func (c *TCPConn) Write(b []byte) (int, error) {
 				select {
 				case <-deadline:
 					return nbytes, c.newOpError("write", &timeoutError{})
-				case <-notifyCh:
+				case <-ch:
+					continue
 				}
 			}
+		default:
+			return nbytes, c.newOpError("write", errors.New(err.String()))
 		}
-
-		var n int64
-		n, err = c.ep.Write(tcpip.SlicePayload(v), tcpip.WriteOptions{})
-		nbytes += int(n)
-		v.TrimFront(int(n))
-	}
-
-	if err == nil {
-		return nbytes, nil
 	}
-
-	return nbytes, c.newOpError("write", errors.New(err.String()))
+	return nbytes, nil
 }
 
 // Close implements net.Conn.Close.
@@ -644,16 +637,18 @@ func (c *UDPConn) WriteTo(b []byte, addr net.Addr) (int, error) {
 	}
 
 	// If we're being called by Write, there is no addr
-	wopts := tcpip.WriteOptions{}
+	writeOptions := tcpip.WriteOptions{}
 	if addr != nil {
 		ua := addr.(*net.UDPAddr)
-		wopts.To = &tcpip.FullAddress{Addr: tcpip.Address(ua.IP), Port: uint16(ua.Port)}
+		writeOptions.To = &tcpip.FullAddress{
+			Addr: tcpip.Address(ua.IP),
+			Port: uint16(ua.Port),
+		}
 	}
 
-	v := buffer.NewView(len(b))
-	copy(v, b)
-
-	n, err := c.ep.Write(tcpip.SlicePayload(v), wopts)
+	var r bytes.Reader
+	r.Reset(b)
+	n, err := c.ep.Write(&r, writeOptions)
 	if err == tcpip.ErrWouldBlock {
 		// Create wait queue entry that notifies a channel.
 		waitEntry, notifyCh := waiter.NewChannelEntry(nil)
@@ -666,7 +661,7 @@ func (c *UDPConn) WriteTo(b []byte, addr net.Addr) (int, error) {
 			case <-notifyCh:
 			}
 
-			n, err = c.ep.Write(tcpip.SlicePayload(v), wopts)
+			n, err = c.ep.Write(&r, writeOptions)
 			if err != tcpip.ErrWouldBlock {
 				break
 			}
diff --git a/pkg/tcpip/network/ipv6/icmp_test.go b/pkg/tcpip/network/ipv6/icmp_test.go
index defea46b0..3fd1bacae 100644
--- a/pkg/tcpip/network/ipv6/icmp_test.go
+++ b/pkg/tcpip/network/ipv6/icmp_test.go
@@ -15,6 +15,7 @@
 package ipv6
 
 import (
+	"bytes"
 	"context"
 	"net"
 	"reflect"
@@ -638,7 +639,6 @@ func TestLinkResolution(t *testing.T) {
 	pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6EchoMinimumSize))
 	pkt.SetType(header.ICMPv6EchoRequest)
 	pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, buffer.VectorisedView{}))
-	payload := tcpip.SlicePayload(hdr.View())
 
 	// We can't send our payload directly over the route because that
 	// doesn't provoke NDP discovery.
@@ -648,8 +648,12 @@ func TestLinkResolution(t *testing.T) {
 		t.Fatalf("NewEndpoint(_) = (_, %s), want = (_, nil)", err)
 	}
 
-	if _, err := ep.Write(payload, tcpip.WriteOptions{To: &tcpip.FullAddress{NIC: nicID, Addr: lladdr1}}); err != nil {
-		t.Fatalf("ep.Write(_): %s", err)
+	{
+		var r bytes.Reader
+		r.Reset(hdr.View())
+		if _, err := ep.Write(&r, tcpip.WriteOptions{To: &tcpip.FullAddress{NIC: nicID, Addr: lladdr1}}); err != nil {
+			t.Fatalf("ep.Write(_): %s", err)
+		}
 	}
 	for _, args := range []routeArgs{
 		{src: c.linkEP0, dst: c.linkEP1, typ: header.ICMPv6NeighborSolicit, remoteLinkAddr: header.EthernetAddressFromMulticastIPv6Address(header.SolicitedNodeAddr(lladdr1))},
diff --git a/pkg/tcpip/sample/tun_tcp_connect/BUILD b/pkg/tcpip/sample/tun_tcp_connect/BUILD
index cf0a5fefe..db9b91815 100644
--- a/pkg/tcpip/sample/tun_tcp_connect/BUILD
+++ b/pkg/tcpip/sample/tun_tcp_connect/BUILD
@@ -8,7 +8,6 @@ go_binary(
     visibility = ["//:sandbox"],
     deps = [
         "//pkg/tcpip",
-        "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
         "//pkg/tcpip/link/fdbased",
         "//pkg/tcpip/link/rawfile",
diff --git a/pkg/tcpip/sample/tun_tcp_connect/main.go b/pkg/tcpip/sample/tun_tcp_connect/main.go
index 3b4f900e3..3d9954c84 100644
--- a/pkg/tcpip/sample/tun_tcp_connect/main.go
+++ b/pkg/tcpip/sample/tun_tcp_connect/main.go
@@ -41,7 +41,7 @@
 package main
 
 import (
-	"bufio"
+	"bytes"
 	"fmt"
 	"log"
 	"math/rand"
@@ -51,7 +51,6 @@ import (
 	"time"
 
 	"gvisor.dev/gvisor/pkg/tcpip"
-	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/link/fdbased"
 	"gvisor.dev/gvisor/pkg/tcpip/link/rawfile"
@@ -71,24 +70,21 @@ func writer(ch chan struct{}, ep tcpip.Endpoint) {
 		close(ch)
 	}()
 
-	r := bufio.NewReader(os.Stdin)
-	for {
-		v := buffer.NewView(1024)
-		n, err := r.Read(v)
-		if err != nil {
-			return
-		}
-
-		v.CapLength(n)
-		for len(v) > 0 {
-			n, err := ep.Write(tcpip.SlicePayload(v), tcpip.WriteOptions{})
-			if err != nil {
-				fmt.Println("Write failed:", err)
-				return
+	var b bytes.Buffer
+	if err := func() error {
+		for {
+			if _, err := b.ReadFrom(os.Stdin); err != nil {
+				return fmt.Errorf("b.ReadFrom failed: %w", err)
 			}
 
-			v.TrimFront(int(n))
+			for b.Len() != 0 {
+				if _, err := ep.Write(&b, tcpip.WriteOptions{Atomic: true}); err != nil {
+					return fmt.Errorf("ep.Write failed: %s", err)
+				}
+			}
 		}
+	}(); err != nil {
+		fmt.Println(err)
 	}
 }
 
diff --git a/pkg/tcpip/sample/tun_tcp_echo/main.go b/pkg/tcpip/sample/tun_tcp_echo/main.go
index 3ac562756..ae9cf44e7 100644
--- a/pkg/tcpip/sample/tun_tcp_echo/main.go
+++ b/pkg/tcpip/sample/tun_tcp_echo/main.go
@@ -20,6 +20,7 @@
 package main
 
 import (
+	"bytes"
 	"flag"
 	"io"
 	"log"
@@ -58,7 +59,9 @@ func (e *tcpipError) Error() string {
 }
 
 func (e *endpointWriter) Write(p []byte) (int, error) {
-	n, err := e.ep.Write(tcpip.SlicePayload(p), tcpip.WriteOptions{})
+	var r bytes.Reader
+	r.Reset(p)
+	n, err := e.ep.Write(&r, tcpip.WriteOptions{})
 	if err != nil {
 		return int(n), &tcpipError{
 			inner: err,
diff --git a/pkg/tcpip/stack/transport_test.go b/pkg/tcpip/stack/transport_test.go
index 9d39533a1..dbf8b4db1 100644
--- a/pkg/tcpip/stack/transport_test.go
+++ b/pkg/tcpip/stack/transport_test.go
@@ -15,6 +15,7 @@
 package stack_test
 
 import (
+	"bytes"
 	"io"
 	"testing"
 
@@ -95,10 +96,11 @@ func (f *fakeTransportEndpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions
 		return 0, tcpip.ErrNoRoute
 	}
 
-	v, err := p.FullPayload()
-	if err != nil {
-		return 0, err
+	v := make([]byte, p.Len())
+	if _, err := io.ReadFull(p, v); err != nil {
+		return 0, tcpip.ErrBadBuffer
 	}
+
 	pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
 		ReserveHeaderBytes: int(f.route.MaxHeaderLength()) + fakeTransHeaderLen,
 		Data:               buffer.View(v).ToVectorisedView(),
@@ -520,8 +522,10 @@ func TestTransportSend(t *testing.T) {
 	}
 
 	// Create buffer that will hold the payload.
-	view := buffer.NewView(30)
-	if _, err := ep.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	b := make([]byte, 30)
+	var r bytes.Reader
+	r.Reset(b)
+	if _, err := ep.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("write failed: %v", err)
 	}
 
diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go
index 4f59e4ff7..fe01029ad 100644
--- a/pkg/tcpip/tcpip.go
+++ b/pkg/tcpip/tcpip.go
@@ -29,6 +29,7 @@
 package tcpip
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
 	"io"
@@ -471,30 +472,15 @@ type FullAddress struct {
 // This interface allows the endpoint to request the amount of data it needs
 // based on internal buffers without exposing them.
 type Payloader interface {
-	// FullPayload returns all available bytes.
-	FullPayload() ([]byte, *Error)
+	io.Reader
 
-	// Payload returns a slice containing at most size bytes.
-	Payload(size int) ([]byte, *Error)
+	// Len returns the number of bytes of the unread portion of the
+	// Reader.
+	Len() int
 }
 
-// SlicePayload implements Payloader for slices.
-//
-// This is typically used for tests.
-type SlicePayload []byte
-
-// FullPayload implements Payloader.FullPayload.
-func (s SlicePayload) FullPayload() ([]byte, *Error) {
-	return s, nil
-}
-
-// Payload implements Payloader.Payload.
-func (s SlicePayload) Payload(size int) ([]byte, *Error) {
-	if size > len(s) {
-		size = len(s)
-	}
-	return s[:size], nil
-}
+var _ Payloader = (*bytes.Buffer)(nil)
+var _ Payloader = (*bytes.Reader)(nil)
 
 var _ io.Writer = (*SliceWriter)(nil)
 
diff --git a/pkg/tcpip/tests/integration/forward_test.go b/pkg/tcpip/tests/integration/forward_test.go
index ac9670f9a..aedf1845e 100644
--- a/pkg/tcpip/tests/integration/forward_test.go
+++ b/pkg/tcpip/tests/integration/forward_test.go
@@ -436,9 +436,10 @@ func TestForwarding(t *testing.T) {
 					write := func(ep tcpip.Endpoint, data []byte) {
 						t.Helper()
 
-						dataPayload := tcpip.SlicePayload(data)
+						var r bytes.Reader
+						r.Reset(data)
 						var wOpts tcpip.WriteOptions
-						n, err := ep.Write(dataPayload, wOpts)
+						n, err := ep.Write(&r, wOpts)
 						if err != nil {
 							t.Fatalf("ep.Write(_, %#v): %s", wOpts, err)
 						}
@@ -486,7 +487,7 @@ func TestForwarding(t *testing.T) {
 
 					read(serverCH, serverEP, data, clientAddr)
 
-					data = tcpip.SlicePayload([]byte{5, 6, 7, 8, 9, 10, 11, 12})
+					data = []byte{5, 6, 7, 8, 9, 10, 11, 12}
 					write(serverEP, data)
 					read(epsAndAddrs.clientReadableCH, epsAndAddrs.clientEP, data, serverAddr)
 				})
diff --git a/pkg/tcpip/tests/integration/link_resolution_test.go b/pkg/tcpip/tests/integration/link_resolution_test.go
index 1e13fd6d6..d0d0e4ef2 100644
--- a/pkg/tcpip/tests/integration/link_resolution_test.go
+++ b/pkg/tcpip/tests/integration/link_resolution_test.go
@@ -209,8 +209,10 @@ func TestPing(t *testing.T) {
 			defer ep.Close()
 
 			icmpBuf := test.icmpBuf(t)
+			var r bytes.Reader
+			r.Reset(icmpBuf)
 			wOpts := tcpip.WriteOptions{To: &tcpip.FullAddress{Addr: test.remoteAddr}}
-			if n, err := ep.Write(tcpip.SlicePayload(icmpBuf), wOpts); err != nil {
+			if n, err := ep.Write(&r, wOpts); err != nil {
 				t.Fatalf("ep.Write(_, _): %s", err)
 			} else if want := int64(len(icmpBuf)); n != want {
 				t.Fatalf("got ep.Write(_, _) = (%d, _), want = (%d, _)", n, want)
@@ -360,9 +362,11 @@ func TestTCPLinkResolutionFailure(t *testing.T) {
 			// Wait for an error due to link resolution failing, or the endpoint to be
 			// writable.
 			<-ch
+			var r bytes.Reader
+			r.Reset([]byte{0})
 			var wOpts tcpip.WriteOptions
-			if n, err := clientEP.Write(tcpip.SlicePayload(nil), wOpts); err != test.expectedWriteErr {
-				t.Errorf("got clientEP.Write(nil, %#v) = (%d, %s), want = (_, %s)", wOpts, n, err, test.expectedWriteErr)
+			if n, err := clientEP.Write(&r, wOpts); err != test.expectedWriteErr {
+				t.Errorf("got clientEP.Write(_, %#v) = (%d, %s), want = (_, %s)", wOpts, n, err, test.expectedWriteErr)
 			}
 
 			if test.expectedWriteErr == nil {
diff --git a/pkg/tcpip/tests/integration/loopback_test.go b/pkg/tcpip/tests/integration/loopback_test.go
index 3b13ba04d..761283b66 100644
--- a/pkg/tcpip/tests/integration/loopback_test.go
+++ b/pkg/tcpip/tests/integration/loopback_test.go
@@ -232,7 +232,9 @@ func TestLoopbackAcceptAllInSubnetUDP(t *testing.T) {
 					Port: localPort,
 				},
 			}
-			n, err := sep.Write(tcpip.SlicePayload(data), wopts)
+			var r bytes.Reader
+			r.Reset(data)
+			n, err := sep.Write(&r, wopts)
 			if err != nil {
 				t.Fatalf("sep.Write(_, _): %s", err)
 			}
diff --git a/pkg/tcpip/tests/integration/multicast_broadcast_test.go b/pkg/tcpip/tests/integration/multicast_broadcast_test.go
index ce7c16bd1..9cc12fa58 100644
--- a/pkg/tcpip/tests/integration/multicast_broadcast_test.go
+++ b/pkg/tcpip/tests/integration/multicast_broadcast_test.go
@@ -586,8 +586,10 @@ func TestReuseAddrAndBroadcast(t *testing.T) {
 						Port: localPort,
 					},
 				}
-				data := tcpip.SlicePayload([]byte{byte(i), 2, 3, 4})
-				if n, err := wep.ep.Write(data, writeOpts); err != nil {
+				data := []byte{byte(i), 2, 3, 4}
+				var r bytes.Reader
+				r.Reset(data)
+				if n, err := wep.ep.Write(&r, writeOpts); err != nil {
 					t.Fatalf("eps[%d].Write(_, _): %s", i, err)
 				} else if want := int64(len(data)); n != want {
 					t.Fatalf("got eps[%d].Write(_, _) = (%d, nil), want = (%d, nil)", i, n, want)
diff --git a/pkg/tcpip/tests/integration/route_test.go b/pkg/tcpip/tests/integration/route_test.go
index b222d2b05..35ee7437a 100644
--- a/pkg/tcpip/tests/integration/route_test.go
+++ b/pkg/tcpip/tests/integration/route_test.go
@@ -194,9 +194,11 @@ func TestLocalPing(t *testing.T) {
 				return
 			}
 
-			payload := tcpip.SlicePayload(test.icmpBuf(t))
+			payload := test.icmpBuf(t)
+			var r bytes.Reader
+			r.Reset(payload)
 			var wOpts tcpip.WriteOptions
-			if n, err := ep.Write(payload, wOpts); err != nil {
+			if n, err := ep.Write(&r, wOpts); err != nil {
 				t.Fatalf("ep.Write(%#v, %#v): %s", payload, wOpts, err)
 			} else if n != int64(len(payload)) {
 				t.Fatalf("got ep.Write(%#v, %#v) = (%d, nil), want = (%d, nil)", payload, wOpts, n, len(payload))
@@ -329,12 +331,14 @@ func TestLocalUDP(t *testing.T) {
 						Port: 80,
 					}
 
-					clientPayload := tcpip.SlicePayload([]byte{1, 2, 3, 4})
+					clientPayload := []byte{1, 2, 3, 4}
 					{
+						var r bytes.Reader
+						r.Reset(clientPayload)
 						wOpts := tcpip.WriteOptions{
 							To: &serverAddr,
 						}
-						if n, err := client.Write(clientPayload, wOpts); err != subTest.expectedWriteErr {
+						if n, err := client.Write(&r, wOpts); err != subTest.expectedWriteErr {
 							t.Fatalf("got client.Write(%#v, %#v) = (%d, %s), want = (_, %s)", clientPayload, wOpts, n, err, subTest.expectedWriteErr)
 						} else if subTest.expectedWriteErr != nil {
 							// Nothing else to test if we expected not to be able to send the
@@ -376,12 +380,14 @@ func TestLocalUDP(t *testing.T) {
 						}
 					}
 
-					serverPayload := tcpip.SlicePayload([]byte{1, 2, 3, 4})
+					serverPayload := []byte{1, 2, 3, 4}
 					{
+						var r bytes.Reader
+						r.Reset(serverPayload)
 						wOpts := tcpip.WriteOptions{
 							To: &clientAddr,
 						}
-						if n, err := server.Write(serverPayload, wOpts); err != nil {
+						if n, err := server.Write(&r, wOpts); err != nil {
 							t.Fatalf("server.Write(%#v, %#v): %s", serverPayload, wOpts, err)
 						} else if n != int64(len(serverPayload)) {
 							t.Fatalf("got server.Write(%#v, %#v) = (%d, nil), want = (%d, nil)", serverPayload, wOpts, n, len(serverPayload))
diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go
index 256e19296..af00ed548 100644
--- a/pkg/tcpip/transport/icmp/endpoint.go
+++ b/pkg/tcpip/transport/icmp/endpoint.go
@@ -313,11 +313,12 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 		route = r
 	}
 
-	v, err := p.FullPayload()
-	if err != nil {
-		return 0, err
+	v := make([]byte, p.Len())
+	if _, err := io.ReadFull(p, v); err != nil {
+		return 0, tcpip.ErrBadBuffer
 	}
 
+	var err *tcpip.Error
 	switch e.NetProto {
 	case header.IPv4ProtocolNumber:
 		err = send4(route, e.ID.LocalPort, v, e.ttl, e.owner)
diff --git a/pkg/tcpip/transport/packet/endpoint.go b/pkg/tcpip/transport/packet/endpoint.go
index c0d6fb442..6fd116a98 100644
--- a/pkg/tcpip/transport/packet/endpoint.go
+++ b/pkg/tcpip/transport/packet/endpoint.go
@@ -207,7 +207,7 @@ func (ep *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResul
 	return res, nil
 }
 
-func (*endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tcpip.Error) {
+func (*endpoint) Write(tcpip.Payloader, tcpip.WriteOptions) (int64, *tcpip.Error) {
 	// TODO(gvisor.dev/issue/173): Implement.
 	return 0, tcpip.ErrInvalidOptionValue
 }
diff --git a/pkg/tcpip/transport/raw/endpoint.go b/pkg/tcpip/transport/raw/endpoint.go
index ae743f75e..2dacf5a64 100644
--- a/pkg/tcpip/transport/raw/endpoint.go
+++ b/pkg/tcpip/transport/raw/endpoint.go
@@ -280,9 +280,9 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 		return 0, tcpip.ErrInvalidEndpointState
 	}
 
-	payloadBytes, err := p.FullPayload()
-	if err != nil {
-		return 0, err
+	payloadBytes := make([]byte, p.Len())
+	if _, err := io.ReadFull(p, payloadBytes); err != nil {
+		return 0, tcpip.ErrBadBuffer
 	}
 
 	// If this is an unassociated socket and callee provided a nonzero
diff --git a/pkg/tcpip/transport/tcp/BUILD b/pkg/tcpip/transport/tcp/BUILD
index 7e81203ba..fcdd032c5 100644
--- a/pkg/tcpip/transport/tcp/BUILD
+++ b/pkg/tcpip/transport/tcp/BUILD
@@ -99,7 +99,6 @@ go_test(
         "//pkg/rand",
         "//pkg/sync",
         "//pkg/tcpip",
-        "//pkg/tcpip/buffer",
         "//pkg/tcpip/checker",
         "//pkg/tcpip/header",
         "//pkg/tcpip/link/loopback",
diff --git a/pkg/tcpip/transport/tcp/dual_stack_test.go b/pkg/tcpip/transport/tcp/dual_stack_test.go
index 1d1b01a6c..809c88732 100644
--- a/pkg/tcpip/transport/tcp/dual_stack_test.go
+++ b/pkg/tcpip/transport/tcp/dual_stack_test.go
@@ -15,11 +15,11 @@
 package tcp_test
 
 import (
+	"strings"
 	"testing"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/tcpip"
-	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/checker"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/network/ipv4"
@@ -415,8 +415,10 @@ func testV4Accept(t *testing.T, c *context.Context) {
 		t.Fatalf("Unexpected remote address: got %v, want %v", addr.Addr, context.TestAddr)
 	}
 
+	var r strings.Reader
 	data := "Don't panic"
-	nep.Write(tcpip.SlicePayload(buffer.NewViewFromBytes([]byte(data))), tcpip.WriteOptions{})
+	r.Reset(data)
+	nep.Write(&r, tcpip.WriteOptions{})
 	b = c.GetPacket()
 	tcp = header.TCP(header.IPv4(b).Payload())
 	if string(tcp.Payload()) != data {
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index ea509ac73..8d27d43c2 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -1534,14 +1534,19 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 	}
 
 	// Fetch data.
-	v, perr := p.Payload(avail)
-	if perr != nil || len(v) == 0 {
-		// Note that perr may be nil if len(v) == 0.
+	if l := p.Len(); l < avail {
+		avail = l
+	}
+	if avail == 0 {
+		return 0, nil
+	}
+	v := make([]byte, avail)
+	if _, err := io.ReadFull(p, v); err != nil {
 		if opts.Atomic {
 			e.sndBufMu.Unlock()
 			e.UnlockUser()
 		}
-		return 0, perr
+		return 0, tcpip.ErrBadBuffer
 	}
 
 	if !opts.Atomic {
diff --git a/pkg/tcpip/transport/tcp/tcp_noracedetector_test.go b/pkg/tcpip/transport/tcp/tcp_noracedetector_test.go
index f7aaee23f..ced3a9c58 100644
--- a/pkg/tcpip/transport/tcp/tcp_noracedetector_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_noracedetector_test.go
@@ -21,13 +21,13 @@
 package tcp_test
 
 import (
+	"bytes"
 	"fmt"
 	"math"
 	"testing"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/tcpip"
-	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/transport/tcp"
 	"gvisor.dev/gvisor/pkg/tcpip/transport/tcp/testing/context"
@@ -42,14 +42,16 @@ func TestFastRecovery(t *testing.T) {
 	c.CreateConnected(789, 30000, -1 /* epRcvBuf */)
 
 	const iterations = 3
-	data := buffer.NewView(2 * maxPayload * (tcp.InitialCwnd << (iterations + 1)))
+	data := make([]byte, 2*maxPayload*(tcp.InitialCwnd<<(iterations+1)))
 	for i := range data {
 		data[i] = byte(i)
 	}
 
 	// Write all the data in one shot. Packets will only be written at the
 	// MTU size though.
-	if _, err := c.EP.Write(tcpip.SlicePayload(data), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -207,14 +209,16 @@ func TestExponentialIncreaseDuringSlowStart(t *testing.T) {
 	c.CreateConnected(789, 30000, -1 /* epRcvBuf */)
 
 	const iterations = 3
-	data := buffer.NewView(maxPayload * (tcp.InitialCwnd << (iterations + 1)))
+	data := make([]byte, maxPayload*(tcp.InitialCwnd<<(iterations+1)))
 	for i := range data {
 		data[i] = byte(i)
 	}
 
 	// Write all the data in one shot. Packets will only be written at the
 	// MTU size though.
-	if _, err := c.EP.Write(tcpip.SlicePayload(data), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -249,14 +253,16 @@ func TestCongestionAvoidance(t *testing.T) {
 	c.CreateConnected(789, 30000, -1 /* epRcvBuf */)
 
 	const iterations = 3
-	data := buffer.NewView(2 * maxPayload * (tcp.InitialCwnd << (iterations + 1)))
+	data := make([]byte, 2*maxPayload*(tcp.InitialCwnd<<(iterations+1)))
 	for i := range data {
 		data[i] = byte(i)
 	}
 
 	// Write all the data in one shot. Packets will only be written at the
 	// MTU size though.
-	if _, err := c.EP.Write(tcpip.SlicePayload(data), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -353,15 +359,16 @@ func TestCubicCongestionAvoidance(t *testing.T) {
 	c.CreateConnected(789, 30000, -1 /* epRcvBuf */)
 
 	const iterations = 3
-	data := buffer.NewView(2 * maxPayload * (tcp.InitialCwnd << (iterations + 1)))
-
+	data := make([]byte, 2*maxPayload*(tcp.InitialCwnd<<(iterations+1)))
 	for i := range data {
 		data[i] = byte(i)
 	}
 
 	// Write all the data in one shot. Packets will only be written at the
 	// MTU size though.
-	if _, err := c.EP.Write(tcpip.SlicePayload(data), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -462,19 +469,20 @@ func TestRetransmit(t *testing.T) {
 	c.CreateConnected(789, 30000, -1 /* epRcvBuf */)
 
 	const iterations = 3
-	data := buffer.NewView(maxPayload * (tcp.InitialCwnd << (iterations + 1)))
+	data := make([]byte, maxPayload*(tcp.InitialCwnd<<(iterations+1)))
 	for i := range data {
 		data[i] = byte(i)
 	}
 
 	// Write all the data in two shots. Packets will only be written at the
 	// MTU size though.
-	half := data[:len(data)/2]
-	if _, err := c.EP.Write(tcpip.SlicePayload(half), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data[:len(data)/2])
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
-	half = data[len(data)/2:]
-	if _, err := c.EP.Write(tcpip.SlicePayload(half), tcpip.WriteOptions{}); err != nil {
+	r.Reset(data[len(data)/2:])
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
diff --git a/pkg/tcpip/transport/tcp/tcp_rack_test.go b/pkg/tcpip/transport/tcp/tcp_rack_test.go
index 342eb5eb8..af915203b 100644
--- a/pkg/tcpip/transport/tcp/tcp_rack_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_rack_test.go
@@ -15,11 +15,11 @@
 package tcp_test
 
 import (
+	"bytes"
 	"testing"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/tcpip"
-	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/seqnum"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
@@ -61,14 +61,16 @@ func TestRACKUpdate(t *testing.T) {
 	setStackSACKPermitted(t, c, true)
 	createConnectedWithSACKAndTS(c)
 
-	data := buffer.NewView(maxPayload)
+	data := make([]byte, maxPayload)
 	for i := range data {
 		data[i] = byte(i)
 	}
 
 	// Write the data.
 	xmitTime = time.Now()
-	if _, err := c.EP.Write(tcpip.SlicePayload(data), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -114,13 +116,15 @@ func TestRACKDetectReorder(t *testing.T) {
 	})
 	setStackSACKPermitted(t, c, true)
 	createConnectedWithSACKAndTS(c)
-	data := buffer.NewView(ackNumToVerify * maxPayload)
+	data := make([]byte, ackNumToVerify*maxPayload)
 	for i := range data {
 		data[i] = byte(i)
 	}
 
 	// Write the data.
-	if _, err := c.EP.Write(tcpip.SlicePayload(data), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -141,17 +145,19 @@ func TestRACKDetectReorder(t *testing.T) {
 	<-probeDone
 }
 
-func sendAndReceive(t *testing.T, c *context.Context, numPackets int) buffer.View {
+func sendAndReceive(t *testing.T, c *context.Context, numPackets int) []byte {
 	setStackSACKPermitted(t, c, true)
 	createConnectedWithSACKAndTS(c)
 
-	data := buffer.NewView(numPackets * maxPayload)
+	data := make([]byte, numPackets*maxPayload)
 	for i := range data {
 		data[i] = byte(i)
 	}
 
 	// Write the data.
-	if _, err := c.EP.Write(tcpip.SlicePayload(data), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
diff --git a/pkg/tcpip/transport/tcp/tcp_sack_test.go b/pkg/tcpip/transport/tcp/tcp_sack_test.go
index 6635bb815..5024bc925 100644
--- a/pkg/tcpip/transport/tcp/tcp_sack_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_sack_test.go
@@ -15,6 +15,7 @@
 package tcp_test
 
 import (
+	"bytes"
 	"fmt"
 	"log"
 	"reflect"
@@ -22,7 +23,6 @@ import (
 	"time"
 
 	"gvisor.dev/gvisor/pkg/tcpip"
-	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/seqnum"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
@@ -395,14 +395,16 @@ func TestSACKRecovery(t *testing.T) {
 	createConnectedWithSACKAndTS(c)
 
 	const iterations = 3
-	data := buffer.NewView(2 * maxPayload * (tcp.InitialCwnd << (iterations + 1)))
+	data := make([]byte, 2*maxPayload*(tcp.InitialCwnd<<(iterations+1)))
 	for i := range data {
 		data[i] = byte(i)
 	}
 
 	// Write all the data in one shot. Packets will only be written at the
 	// MTU size though.
-	if _, err := c.EP.Write(tcpip.SlicePayload(data), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
diff --git a/pkg/tcpip/transport/tcp/tcp_test.go b/pkg/tcpip/transport/tcp/tcp_test.go
index 93683b921..db9dc4e25 100644
--- a/pkg/tcpip/transport/tcp/tcp_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_test.go
@@ -19,6 +19,7 @@ import (
 	"fmt"
 	"io/ioutil"
 	"math"
+	"strings"
 	"testing"
 	"time"
 
@@ -26,7 +27,6 @@ import (
 	"gvisor.dev/gvisor/pkg/rand"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
-	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/checker"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/link/loopback"
@@ -1347,10 +1347,9 @@ func TestTOSV4(t *testing.T) {
 	testV4Connect(t, c, checker.TOS(tos, 0))
 
 	data := []byte{1, 2, 3}
-	view := buffer.NewView(len(data))
-	copy(view, data)
-
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -1396,10 +1395,9 @@ func TestTrafficClassV6(t *testing.T) {
 	testV6Connect(t, c, checker.TOS(tos, 0))
 
 	data := []byte{1, 2, 3}
-	view := buffer.NewView(len(data))
-	copy(view, data)
-
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -2176,10 +2174,9 @@ func TestSimpleSend(t *testing.T) {
 	c.CreateConnected(789, 30000, -1 /* epRcvBuf */)
 
 	data := []byte{1, 2, 3}
-	view := buffer.NewView(len(data))
-	copy(view, data)
-
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -2217,10 +2214,9 @@ func TestZeroWindowSend(t *testing.T) {
 	c.CreateConnected(789 /* iss */, 0 /* rcvWnd */, -1 /* epRcvBuf */)
 
 	data := []byte{1, 2, 3}
-	view := buffer.NewView(len(data))
-	copy(view, data)
-
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -2285,10 +2281,9 @@ func TestScaledWindowConnect(t *testing.T) {
 	})
 
 	data := []byte{1, 2, 3}
-	view := buffer.NewView(len(data))
-	copy(view, data)
-
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -2317,10 +2312,9 @@ func TestNonScaledWindowConnect(t *testing.T) {
 	c.CreateConnected(789, 30000, 65535*3)
 
 	data := []byte{1, 2, 3}
-	view := buffer.NewView(len(data))
-	copy(view, data)
-
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -2391,10 +2385,9 @@ func TestScaledWindowAccept(t *testing.T) {
 	}
 
 	data := []byte{1, 2, 3}
-	view := buffer.NewView(len(data))
-	copy(view, data)
-
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -2465,10 +2458,9 @@ func TestNonScaledWindowAccept(t *testing.T) {
 	}
 
 	data := []byte{1, 2, 3}
-	view := buffer.NewView(len(data))
-	copy(view, data)
-
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -2632,9 +2624,10 @@ func TestSegmentMerging(t *testing.T) {
 			// Send tcp.InitialCwnd number of segments to fill up
 			// InitialWindow but don't ACK. That should prevent
 			// anymore packets from going out.
+			var r bytes.Reader
 			for i := 0; i < tcp.InitialCwnd; i++ {
-				view := buffer.NewViewFromBytes([]byte{0})
-				if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+				r.Reset([]byte{0})
+				if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 					t.Fatalf("Write #%d failed: %s", i+1, err)
 				}
 			}
@@ -2644,8 +2637,8 @@ func TestSegmentMerging(t *testing.T) {
 			var allData []byte
 			for i, data := range [][]byte{{1, 2, 3, 4}, {5, 6, 7}, {8, 9}, {10}, {11}} {
 				allData = append(allData, data...)
-				view := buffer.NewViewFromBytes(data)
-				if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+				r.Reset(data)
+				if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 					t.Fatalf("Write #%d failed: %s", i+1, err)
 				}
 			}
@@ -2714,8 +2707,9 @@ func TestDelay(t *testing.T) {
 	var allData []byte
 	for i, data := range [][]byte{{0}, {1, 2, 3, 4}, {5, 6, 7}, {8, 9}, {10}, {11}} {
 		allData = append(allData, data...)
-		view := buffer.NewViewFromBytes(data)
-		if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+		var r bytes.Reader
+		r.Reset(data)
+		if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 			t.Fatalf("Write #%d failed: %s", i+1, err)
 		}
 	}
@@ -2761,8 +2755,9 @@ func TestUndelay(t *testing.T) {
 
 	allData := [][]byte{{0}, {1, 2, 3}}
 	for i, data := range allData {
-		view := buffer.NewViewFromBytes(data)
-		if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+		var r bytes.Reader
+		r.Reset(data)
+		if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 			t.Fatalf("Write #%d failed: %s", i+1, err)
 		}
 	}
@@ -2845,8 +2840,9 @@ func TestMSSNotDelayed(t *testing.T) {
 
 			allData := [][]byte{{0}, make([]byte, maxPayload), make([]byte, maxPayload)}
 			for i, data := range allData {
-				view := buffer.NewViewFromBytes(data)
-				if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+				var r bytes.Reader
+				r.Reset(data)
+				if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 					t.Fatalf("Write #%d failed: %s", i+1, err)
 				}
 			}
@@ -2894,10 +2890,9 @@ func testBrokenUpWrite(t *testing.T, c *context.Context, maxPayload int) {
 		data[i] = byte(i)
 	}
 
-	view := buffer.NewView(len(data))
-	copy(view, data)
-
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -3328,8 +3323,9 @@ func TestSendOnResetConnection(t *testing.T) {
 	time.Sleep(1 * time.Second)
 
 	// Try to write.
-	view := buffer.NewView(10)
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != tcpip.ErrConnectionReset {
+	var r bytes.Reader
+	r.Reset(make([]byte, 10))
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != tcpip.ErrConnectionReset {
 		t.Fatalf("got c.EP.Write(...) = %s, want = %s", err, tcpip.ErrConnectionReset)
 	}
 }
@@ -3352,7 +3348,9 @@ func TestMaxRetransmitsTimeout(t *testing.T) {
 	c.WQ.EventRegister(&waitEntry, waiter.EventHUp)
 	defer c.WQ.EventUnregister(&waitEntry)
 
-	_, err := c.EP.Write(tcpip.SlicePayload(buffer.NewView(1)), tcpip.WriteOptions{})
+	var r bytes.Reader
+	r.Reset(make([]byte, 1))
+	_, err := c.EP.Write(&r, tcpip.WriteOptions{})
 	if err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
@@ -3409,7 +3407,9 @@ func TestMaxRTO(t *testing.T) {
 
 	c.CreateConnected(789 /* iss */, 30000 /* rcvWnd */, -1 /* epRcvBuf */)
 
-	_, err := c.EP.Write(tcpip.SlicePayload(buffer.NewView(1)), tcpip.WriteOptions{})
+	var r bytes.Reader
+	r.Reset(make([]byte, 1))
+	_, err := c.EP.Write(&r, tcpip.WriteOptions{})
 	if err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
@@ -3458,7 +3458,9 @@ func TestRetransmitIPv4IDUniqueness(t *testing.T) {
 				t.Fatalf("disabling PMTU discovery via sockopt to force DF=0 failed: %s", err)
 			}
 
-			if _, err := c.EP.Write(tcpip.SlicePayload(buffer.NewView(tc.size)), tcpip.WriteOptions{}); err != nil {
+			var r bytes.Reader
+			r.Reset(make([]byte, tc.size))
+			if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 				t.Fatalf("Write failed: %s", err)
 			}
 			pkt := c.GetPacket()
@@ -3595,8 +3597,10 @@ func TestFinWithNoPendingData(t *testing.T) {
 	c.CreateConnected(789, 30000, -1 /* epRcvBuf */)
 
 	// Write something out, and have it acknowledged.
-	view := buffer.NewView(10)
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	view := make([]byte, 10)
+	var r bytes.Reader
+	r.Reset(view)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -3667,9 +3671,11 @@ func TestFinWithPendingDataCwndFull(t *testing.T) {
 
 	// Write enough segments to fill the congestion window before ACK'ing
 	// any of them.
-	view := buffer.NewView(10)
+	view := make([]byte, 10)
+	var r bytes.Reader
 	for i := tcp.InitialCwnd; i > 0; i-- {
-		if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+		r.Reset(view)
+		if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 			t.Fatalf("Write failed: %s", err)
 		}
 	}
@@ -3754,8 +3760,10 @@ func TestFinWithPendingData(t *testing.T) {
 	c.CreateConnected(789, 30000, -1 /* epRcvBuf */)
 
 	// Write something out, and acknowledge it to get cwnd to 2.
-	view := buffer.NewView(10)
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	view := make([]byte, 10)
+	var r bytes.Reader
+	r.Reset(view)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -3781,7 +3789,8 @@ func TestFinWithPendingData(t *testing.T) {
 	})
 
 	// Write new data, but don't acknowledge it.
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	r.Reset(view)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -3841,8 +3850,10 @@ func TestFinWithPartialAck(t *testing.T) {
 
 	// Write something out, and acknowledge it to get cwnd to 2. Also send
 	// FIN from the test side.
-	view := buffer.NewView(10)
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	view := make([]byte, 10)
+	var r bytes.Reader
+	r.Reset(view)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -3879,7 +3890,8 @@ func TestFinWithPartialAck(t *testing.T) {
 	)
 
 	// Write new data, but don't acknowledge it.
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	r.Reset(view)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -3985,8 +3997,10 @@ func scaledSendWindow(t *testing.T, scale uint8) {
 	})
 
 	// Send some data. Check that it's capped by the window size.
-	view := buffer.NewView(65535)
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	view := make([]byte, 65535)
+	var r bytes.Reader
+	r.Reset(view)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -4610,9 +4624,9 @@ func TestSelfConnect(t *testing.T) {
 
 	// Write something.
 	data := []byte{1, 2, 3}
-	view := buffer.NewView(len(data))
-	copy(view, data)
-	if _, err := ep.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := ep.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -4785,12 +4799,13 @@ func TestPathMTUDiscovery(t *testing.T) {
 
 	// Send 3200 bytes of data.
 	const writeSize = 3200
-	data := buffer.NewView(writeSize)
+	data := make([]byte, writeSize)
 	for i := range data {
 		data[i] = byte(i)
 	}
-
-	if _, err := c.EP.Write(tcpip.SlicePayload(data), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -5078,8 +5093,10 @@ func TestKeepalive(t *testing.T) {
 
 	// Send some data and wait before ACKing it. Keepalives should be disabled
 	// during this period.
-	view := buffer.NewView(3)
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	view := make([]byte, 3)
+	var r bytes.Reader
+	r.Reset(view)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -5358,7 +5375,9 @@ func TestListenBacklogFull(t *testing.T) {
 
 	// Now verify that the TCP socket is usable and in a connected state.
 	data := "Don't panic"
-	newEP.Write(tcpip.SlicePayload(buffer.NewViewFromBytes([]byte(data))), tcpip.WriteOptions{})
+	var r strings.Reader
+	r.Reset(data)
+	newEP.Write(&r, tcpip.WriteOptions{})
 	b := c.GetPacket()
 	tcp := header.TCP(header.IPv4(b).Payload())
 	if string(tcp.Payload()) != data {
@@ -5674,7 +5693,9 @@ func TestListenSynRcvdQueueFull(t *testing.T) {
 
 	// Now verify that the TCP socket is usable and in a connected state.
 	data := "Don't panic"
-	newEP.Write(tcpip.SlicePayload(buffer.NewViewFromBytes([]byte(data))), tcpip.WriteOptions{})
+	var r strings.Reader
+	r.Reset(data)
+	newEP.Write(&r, tcpip.WriteOptions{})
 	pkt := c.GetPacket()
 	tcp = header.TCP(header.IPv4(pkt).Payload())
 	if string(tcp.Payload()) != data {
@@ -5908,7 +5929,9 @@ func TestSynRcvdBadSeqNumber(t *testing.T) {
 
 	// Now verify that the TCP socket is usable and in a connected state.
 	data := "Don't panic"
-	if _, err := newEP.Write(tcpip.SlicePayload(buffer.NewViewFromBytes([]byte(data))), tcpip.WriteOptions{}); err != nil {
+	var r strings.Reader
+	r.Reset(data)
+	if _, err := newEP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -7103,10 +7126,10 @@ func TestTCPCloseWithData(t *testing.T) {
 
 	// Now write a few bytes and then close the endpoint.
 	data := []byte{1, 2, 3}
-	view := buffer.NewView(len(data))
-	copy(view, data)
 
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
@@ -7204,8 +7227,10 @@ func TestTCPUserTimeout(t *testing.T) {
 	}
 
 	// Send some data and wait before ACKing it.
-	view := buffer.NewView(3)
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	view := make([]byte, 3)
+	var r bytes.Reader
+	r.Reset(view)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Write failed: %s", err)
 	}
 
diff --git a/pkg/tcpip/transport/tcp/tcp_timestamp_test.go b/pkg/tcpip/transport/tcp/tcp_timestamp_test.go
index b65091c3c..5a9745ad7 100644
--- a/pkg/tcpip/transport/tcp/tcp_timestamp_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_timestamp_test.go
@@ -22,7 +22,6 @@ import (
 
 	"github.com/google/go-cmp/cmp"
 	"gvisor.dev/gvisor/pkg/tcpip"
-	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/checker"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/transport/tcp"
@@ -152,10 +151,10 @@ func timeStampEnabledAccept(t *testing.T, cookieEnabled bool, wndScale int, wndS
 
 	// Now send some data and validate that timestamp is echoed correctly in the ACK.
 	data := []byte{1, 2, 3}
-	view := buffer.NewView(len(data))
-	copy(view, data)
 
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Unexpected error from Write: %s", err)
 	}
 
@@ -215,10 +214,10 @@ func timeStampDisabledAccept(t *testing.T, cookieEnabled bool, wndScale int, wnd
 	// Now send some data with the accepted connection endpoint and validate
 	// that no timestamp option is sent in the TCP segment.
 	data := []byte{1, 2, 3}
-	view := buffer.NewView(len(data))
-	copy(view, data)
 
-	if _, err := c.EP.Write(tcpip.SlicePayload(view), tcpip.WriteOptions{}); err != nil {
+	var r bytes.Reader
+	r.Reset(data)
+	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != nil {
 		t.Fatalf("Unexpected error from Write: %s", err)
 	}
 
diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index 9f9b3d510..8544fcb08 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -514,9 +514,9 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 		return 0, tcpip.ErrBroadcastDisabled
 	}
 
-	v, err := p.FullPayload()
-	if err != nil {
-		return 0, err
+	v := make([]byte, p.Len())
+	if _, err := io.ReadFull(p, v); err != nil {
+		return 0, tcpip.ErrBadBuffer
 	}
 	if len(v) > header.UDPMaximumPacketSize {
 		// Payload can't possibly fit in a packet.
diff --git a/pkg/tcpip/transport/udp/udp_test.go b/pkg/tcpip/transport/udp/udp_test.go
index 4e2123fe9..c4794e876 100644
--- a/pkg/tcpip/transport/udp/udp_test.go
+++ b/pkg/tcpip/transport/udp/udp_test.go
@@ -966,8 +966,9 @@ func testFailingWrite(c *testContext, flow testFlow, wantErr *tcpip.Error) {
 	h := flow.header4Tuple(outgoing)
 	writeDstAddr := flow.mapAddrIfApplicable(h.dstAddr.Addr)
 
-	payload := buffer.View(newPayload())
-	_, gotErr := c.ep.Write(tcpip.SlicePayload(payload), tcpip.WriteOptions{
+	var r bytes.Reader
+	r.Reset(newPayload())
+	_, gotErr := c.ep.Write(&r, tcpip.WriteOptions{
 		To: &tcpip.FullAddress{Addr: writeDstAddr, Port: h.dstAddr.Port},
 	})
 	c.checkEndpointWriteStats(1, epstats, gotErr)
@@ -1007,8 +1008,10 @@ func testWriteNoVerify(c *testContext, flow testFlow, setDest bool) buffer.View
 			To: &tcpip.FullAddress{Addr: writeDstAddr, Port: h.dstAddr.Port},
 		}
 	}
-	payload := buffer.View(newPayload())
-	n, err := c.ep.Write(tcpip.SlicePayload(payload), writeOpts)
+	var r bytes.Reader
+	payload := newPayload()
+	r.Reset(payload)
+	n, err := c.ep.Write(&r, writeOpts)
 	if err != nil {
 		c.t.Fatalf("Write failed: %s", err)
 	}
@@ -1183,8 +1186,10 @@ func TestWriteOnConnectedInvalidPort(t *testing.T) {
 			writeOpts := tcpip.WriteOptions{
 				To: &tcpip.FullAddress{Addr: stackAddr, Port: invalidPort},
 			}
-			payload := buffer.View(newPayload())
-			n, err := c.ep.Write(tcpip.SlicePayload(payload), writeOpts)
+			var r bytes.Reader
+			payload := newPayload()
+			r.Reset(payload)
+			n, err := c.ep.Write(&r, writeOpts)
 			if err != nil {
 				c.t.Fatalf("c.ep.Write(...) = %+s, want nil", err)
 			}
@@ -2497,7 +2502,8 @@ func TestOutgoingSubnetBroadcast(t *testing.T) {
 			}
 			defer ep.Close()
 
-			data := tcpip.SlicePayload([]byte{1, 2, 3, 4})
+			var r bytes.Reader
+			data := []byte{1, 2, 3, 4}
 			to := tcpip.FullAddress{
 				Addr: test.remoteAddr,
 				Port: 80,
@@ -2508,19 +2514,22 @@ func TestOutgoingSubnetBroadcast(t *testing.T) {
 				expectedErrWithoutBcastOpt = nil
 			}
 
-			if n, err := ep.Write(data, opts); err != expectedErrWithoutBcastOpt {
+			r.Reset(data)
+			if n, err := ep.Write(&r, opts); err != expectedErrWithoutBcastOpt {
 				t.Fatalf("got ep.Write(_, %#v) = (%d, %s), want = (_, %s)", opts, n, err, expectedErrWithoutBcastOpt)
 			}
 
 			ep.SocketOptions().SetBroadcast(true)
 
-			if n, err := ep.Write(data, opts); err != nil {
+			r.Reset(data)
+			if n, err := ep.Write(&r, opts); err != nil {
 				t.Fatalf("got ep.Write(_, %#v) = (%d, %s), want = (_, nil)", opts, n, err)
 			}
 
 			ep.SocketOptions().SetBroadcast(false)
 
-			if n, err := ep.Write(data, opts); err != expectedErrWithoutBcastOpt {
+			r.Reset(data)
+			if n, err := ep.Write(&r, opts); err != expectedErrWithoutBcastOpt {
 				t.Fatalf("got ep.Write(_, %#v) = (%d, %s), want = (_, %s)", opts, n, err, expectedErrWithoutBcastOpt)
 			}
 		})
diff --git a/pkg/usermem/usermem.go b/pkg/usermem/usermem.go
index 79db8895b..dc2571154 100644
--- a/pkg/usermem/usermem.go
+++ b/pkg/usermem/usermem.go
@@ -517,28 +517,29 @@ func (s IOSequence) CopyInTo(ctx context.Context, dst safemem.Writer) (int64, er
 // Reader returns an io.Reader that reads from s. Reads beyond the end of s
 // return io.EOF. The preconditions that apply to s.CopyIn also apply to the
 // returned io.Reader.Read.
-func (s IOSequence) Reader(ctx context.Context) io.Reader {
-	return &ioSequenceReadWriter{ctx, s}
+func (s IOSequence) Reader(ctx context.Context) *IOSequenceReadWriter {
+	return &IOSequenceReadWriter{ctx, s}
 }
 
 // Writer returns an io.Writer that writes to s. Writes beyond the end of s
 // return ErrEndOfIOSequence. The preconditions that apply to s.CopyOut also
 // apply to the returned io.Writer.Write.
-func (s IOSequence) Writer(ctx context.Context) io.Writer {
-	return &ioSequenceReadWriter{ctx, s}
+func (s IOSequence) Writer(ctx context.Context) *IOSequenceReadWriter {
+	return &IOSequenceReadWriter{ctx, s}
 }
 
 // ErrEndOfIOSequence is returned by IOSequence.Writer().Write() when
 // attempting to write beyond the end of the IOSequence.
 var ErrEndOfIOSequence = errors.New("write beyond end of IOSequence")
 
-type ioSequenceReadWriter struct {
+// IOSequenceReadWriter implements io.Reader and io.Writer for an IOSequence.
+type IOSequenceReadWriter struct {
 	ctx context.Context
 	s   IOSequence
 }
 
 // Read implements io.Reader.Read.
-func (rw *ioSequenceReadWriter) Read(dst []byte) (int, error) {
+func (rw *IOSequenceReadWriter) Read(dst []byte) (int, error) {
 	n, err := rw.s.CopyIn(rw.ctx, dst)
 	rw.s = rw.s.DropFirst(n)
 	if err == nil && rw.s.NumBytes() == 0 {
@@ -547,8 +548,13 @@ func (rw *ioSequenceReadWriter) Read(dst []byte) (int, error) {
 	return n, err
 }
 
+// Len implements tcpip.Payloader.
+func (rw *IOSequenceReadWriter) Len() int {
+	return int(rw.s.NumBytes())
+}
+
 // Write implements io.Writer.Write.
-func (rw *ioSequenceReadWriter) Write(src []byte) (int, error) {
+func (rw *IOSequenceReadWriter) Write(src []byte) (int, error) {
 	n, err := rw.s.CopyOut(rw.ctx, src)
 	rw.s = rw.s.DropFirst(n)
 	if err == nil && n < len(src) {