net, os, internal/poll: test for use of sendfile

The net package's sendfile tests exercise various paths where
we expect sendfile to be used, but don't verify that sendfile
was in fact used.

Add a hook to internal/poll.SendFile to let us verify that
sendfile was called when expected. Update os package tests
(which use their own hook mechanism) to use this hook as well.

For #66988

Change-Id: I7afb130dcfe0063d60c6ea0f8560cf8665ad5a81
Reviewed-on: https://go-review.googlesource.com/c/go/+/581778
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

5 files changed, 19 insertions, 0 deletions

diff --git a/src/internal/poll/sendfile.go b/src/internal/poll/sendfile.go
new file mode 100644
index 0000000000..41b0481c1a
--- /dev/null
+++ b/src/internal/poll/sendfile.go
@@ -0,0 +1,7 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package poll
+
+var TestHookDidSendFile = func(dstFD *FD, src int, written int64, err error, handled bool) {}
diff --git a/src/internal/poll/sendfile_bsd.go b/src/internal/poll/sendfile_bsd.go
index 8fcdb1c22e..669df94cc1 100644
--- a/src/internal/poll/sendfile_bsd.go
+++ b/src/internal/poll/sendfile_bsd.go
@@ -14,6 +14,9 @@ const maxSendfileSize int = 4 << 20
 
 // SendFile wraps the sendfile system call.
 func SendFile(dstFD *FD, src int, pos, remain int64) (written int64, err error, handled bool) {
+	defer func() {
+		TestHookDidSendFile(dstFD, src, written, err, handled)
+	}()
 	if err := dstFD.writeLock(); err != nil {
 		return 0, err, false
 	}
diff --git a/src/internal/poll/sendfile_linux.go b/src/internal/poll/sendfile_linux.go
index c2a0653294..d1c4d5c0d3 100644
--- a/src/internal/poll/sendfile_linux.go
+++ b/src/internal/poll/sendfile_linux.go
@@ -12,6 +12,9 @@ const maxSendfileSize int = 4 << 20
 
 // SendFile wraps the sendfile system call.
 func SendFile(dstFD *FD, src int, remain int64) (written int64, err error, handled bool) {
+	defer func() {
+		TestHookDidSendFile(dstFD, src, written, err, handled)
+	}()
 	if err := dstFD.writeLock(); err != nil {
 		return 0, err, false
 	}
diff --git a/src/internal/poll/sendfile_solaris.go b/src/internal/poll/sendfile_solaris.go
index 1ba0c8d064..ec675833a2 100644
--- a/src/internal/poll/sendfile_solaris.go
+++ b/src/internal/poll/sendfile_solaris.go
@@ -17,6 +17,9 @@ const maxSendfileSize int = 4 << 20
 
 // SendFile wraps the sendfile system call.
 func SendFile(dstFD *FD, src int, pos, remain int64) (written int64, err error, handled bool) {
+	defer func() {
+		TestHookDidSendFile(dstFD, src, written, err, handled)
+	}()
 	if err := dstFD.writeLock(); err != nil {
 		return 0, err, false
 	}
diff --git a/src/internal/poll/sendfile_windows.go b/src/internal/poll/sendfile_windows.go
index 8c3353bc6f..2ae8a8d1d7 100644
--- a/src/internal/poll/sendfile_windows.go
+++ b/src/internal/poll/sendfile_windows.go
@@ -11,6 +11,9 @@ import (
 
 // SendFile wraps the TransmitFile call.
 func SendFile(fd *FD, src syscall.Handle, n int64) (written int64, err error) {
+	defer func() {
+		TestHookDidSendFile(fd, 0, written, err, written > 0)
+	}()
 	if fd.kind == kindPipe {
 		// TransmitFile does not work with pipes
 		return 0, syscall.ESPIPE