net: break up >1GB reads and writes on stream connections

Also fix behavior of Buffers.WriteTo when writev returns an error.

Fixes #16266.

Change-Id: Idc9503408ce2cb460663768fab86035cbab11aef
Reviewed-on: https://go-review.googlesource.com/31584
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

6 files changed, 115 insertions, 4 deletions

diff --git a/src/net/fd_plan9.go b/src/net/fd_plan9.go
index d32b622966..ab5db38dbe 100644
--- a/src/net/fd_plan9.go
+++ b/src/net/fd_plan9.go
@@ -22,6 +22,7 @@ type netFD struct {
 	dir               string
 	listen, ctl, data *os.File
 	laddr, raddr      Addr
+	isStream          bool
 }
 
 var (
diff --git a/src/net/fd_unix.go b/src/net/fd_unix.go
index 1296bc56b2..3c95fc01d4 100644
--- a/src/net/fd_unix.go
+++ b/src/net/fd_unix.go
@@ -24,6 +24,7 @@ type netFD struct {
 	sysfd       int
 	family      int
 	sotype      int
+	isStream    bool
 	isConnected bool
 	net         string
 	laddr       Addr
@@ -40,7 +41,7 @@ func sysInit() {
 }
 
 func newFD(sysfd, family, sotype int, net string) (*netFD, error) {
-	return &netFD{sysfd: sysfd, family: family, sotype: sotype, net: net}, nil
+	return &netFD{sysfd: sysfd, family: family, sotype: sotype, net: net, isStream: sotype == syscall.SOCK_STREAM}, nil
 }
 
 func (fd *netFD) init() error {
@@ -238,6 +239,9 @@ func (fd *netFD) Read(p []byte) (n int, err error) {
 	if err := fd.pd.prepareRead(); err != nil {
 		return 0, err
 	}
+	if fd.isStream && len(p) > 1<<30 {
+		p = p[:1<<30]
+	}
 	for {
 		n, err = syscall.Read(fd.sysfd, p)
 		if err != nil {
@@ -321,7 +325,11 @@ func (fd *netFD) Write(p []byte) (nn int, err error) {
 	}
 	for {
 		var n int
-		n, err = syscall.Write(fd.sysfd, p[nn:])
+		max := len(p)
+		if fd.isStream && max-nn > 1<<30 {
+			max = nn + 1<<30
+		}
+		n, err = syscall.Write(fd.sysfd, p[nn:max])
 		if n > 0 {
 			nn += n
 		}
diff --git a/src/net/fd_windows.go b/src/net/fd_windows.go
index d1c368e883..828da4a2e6 100644
--- a/src/net/fd_windows.go
+++ b/src/net/fd_windows.go
@@ -239,6 +239,7 @@ type netFD struct {
 	sysfd         syscall.Handle
 	family        int
 	sotype        int
+	isStream      bool
 	isConnected   bool
 	skipSyncNotif bool
 	net           string
@@ -257,7 +258,7 @@ func newFD(sysfd syscall.Handle, family, sotype int, net string) (*netFD, error)
 		return nil, initErr
 	}
 	onceStartServer.Do(startServer)
-	return &netFD{sysfd: sysfd, family: family, sotype: sotype, net: net}, nil
+	return &netFD{sysfd: sysfd, family: family, sotype: sotype, net: net, isStream: sotype == syscall.SOCK_STREAM}, nil
 }
 
 func (fd *netFD) init() error {
diff --git a/src/net/tcpsock_test.go b/src/net/tcpsock_test.go
index d80a3736bf..0d283dfa4f 100644
--- a/src/net/tcpsock_test.go
+++ b/src/net/tcpsock_test.go
@@ -5,6 +5,7 @@
 package net
 
 import (
+	"fmt"
 	"internal/testenv"
 	"io"
 	"reflect"
@@ -654,3 +655,58 @@ func TestTCPSelfConnect(t *testing.T) {
 		}
 	}
 }
+
+// Test that >32-bit reads work on 64-bit systems.
+// On 32-bit systems this tests that maxint reads work.
+func TestTCPBig(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping test in short mode")
+	}
+
+	for _, writev := range []bool{false, true} {
+		t.Run(fmt.Sprintf("writev=%v", writev), func(t *testing.T) {
+			ln, err := newLocalListener("tcp")
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer ln.Close()
+
+			x := int(1 << 30)
+			x = x*5 + 1<<20 // just over 5 GB on 64-bit, just over 1GB on 32-bit
+			done := make(chan int)
+			go func() {
+				defer close(done)
+				c, err := ln.Accept()
+				if err != nil {
+					t.Error(err)
+					return
+				}
+				buf := make([]byte, x)
+				var n int
+				if writev {
+					var n64 int64
+					n64, err = (&Buffers{buf}).WriteTo(c)
+					n = int(n64)
+				} else {
+					n, err = c.Write(buf)
+				}
+				if n != len(buf) || err != nil {
+					t.Errorf("Write(buf) = %d, %v, want %d, nil", n, err, x)
+				}
+				c.Close()
+			}()
+
+			c, err := Dial("tcp", ln.Addr().String())
+			if err != nil {
+				t.Fatal(err)
+			}
+			buf := make([]byte, x)
+			n, err := io.ReadFull(c, buf)
+			if n != len(buf) || err != nil {
+				t.Errorf("Read(buf) = %d, %v, want %d, nil", n, err, x)
+			}
+			c.Close()
+			<-done
+		})
+	}
+}
diff --git a/src/net/writev_test.go b/src/net/writev_test.go
index cc53adcdd1..385cc12503 100644
--- a/src/net/writev_test.go
+++ b/src/net/writev_test.go
@@ -169,3 +169,44 @@ func testBuffer_writeTo(t *testing.T, chunks int, useCopy bool) {
 		return nil
 	})
 }
+
+func TestWritevError(t *testing.T) {
+	ln, err := newLocalListener("tcp")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer ln.Close()
+
+	ch := make(chan Conn, 1)
+	go func() {
+		defer close(ch)
+		c, err := ln.Accept()
+		if err != nil {
+			t.Error(err)
+			return
+		}
+		ch <- c
+	}()
+	c1, err := Dial("tcp", ln.Addr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c1.Close()
+	c2 := <-ch
+	if c2 == nil {
+		t.Fatal("no server side connection")
+	}
+	c2.Close()
+
+	// 1 GB of data should be enough to notice the connection is gone.
+	// Just a few bytes is not enough.
+	// Arrange to reuse the same 1 MB buffer so that we don't allocate much.
+	buf := make([]byte, 1<<20)
+	buffers := make(Buffers, 1<<10)
+	for i := range buffers {
+		buffers[i] = buf
+	}
+	if _, err := buffers.WriteTo(c1); err == nil {
+		t.Fatalf("Buffers.WriteTo(closed conn) succeeded, want error", err)
+	}
+}
diff --git a/src/net/writev_unix.go b/src/net/writev_unix.go
index ac4f7cf61a..174e6bc51e 100644
--- a/src/net/writev_unix.go
+++ b/src/net/writev_unix.go
@@ -49,6 +49,10 @@ func (fd *netFD) writeBuffers(v *Buffers) (n int64, err error) {
 				continue
 			}
 			iovecs = append(iovecs, syscall.Iovec{Base: &chunk[0]})
+			if fd.isStream && len(chunk) > 1<<30 {
+				iovecs[len(iovecs)-1].SetLen(1 << 30)
+				break // continue chunk on next writev
+			}
 			iovecs[len(iovecs)-1].SetLen(len(chunk))
 			if len(iovecs) == maxVec {
 				break
@@ -63,7 +67,7 @@ func (fd *netFD) writeBuffers(v *Buffers) (n int64, err error) {
 			uintptr(fd.sysfd),
 			uintptr(unsafe.Pointer(&iovecs[0])),
 			uintptr(len(iovecs)))
-		if wrote < 0 {
+		if wrote == ^uintptr(0) {
 			wrote = 0
 		}
 		testHookDidWritev(int(wrote))