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>

1 files changed, 56 insertions, 0 deletions

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
+		})
+	}
+}