From ce4f4283badb6b07baf9f8e6d99e7a5fd15c92db Mon Sep 17 00:00:00 2001
From: Ayush Ranjan <ayushranjan@google.com>
Date: Fri, 5 Nov 2021 10:40:53 -0700
Subject: Make {Un}Marshal{Bytes/Unsafe} return remaining buffer.

Change marshal.Marshallable method signatures to return the remaining buffer.
This makes it easier to implement these method manually. Without this, we would
have to manually do buffer shifting which is error prone.

tools/go_marshal/test:benchmark test does not show change in performance.
Additionally fixed some marshalling bugs in fsimpl/fuse.

Updated multiple callpoints to get rid of redundant slice indexing work and
simplified code using this new signature.

Updates #6450

PiperOrigin-RevId: 407857019
---
 pkg/sentry/socket/netlink/message_test.go | 45 +++++++------------------------
 pkg/sentry/socket/netlink/socket.go       |  2 +-
 2 files changed, 10 insertions(+), 37 deletions(-)

(limited to 'pkg/sentry/socket/netlink')

diff --git a/pkg/sentry/socket/netlink/message_test.go b/pkg/sentry/socket/netlink/message_test.go
index 968968469..1604b2792 100644
--- a/pkg/sentry/socket/netlink/message_test.go
+++ b/pkg/sentry/socket/netlink/message_test.go
@@ -25,33 +25,14 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/socket/netlink"
 )
 
-type dummyNetlinkMsg struct {
-	marshal.StubMarshallable
-	Foo uint16
-}
-
-func (*dummyNetlinkMsg) SizeBytes() int {
-	return 2
-}
-
-func (m *dummyNetlinkMsg) MarshalUnsafe(dst []byte) {
-	p := primitive.Uint16(m.Foo)
-	p.MarshalUnsafe(dst)
-}
-
-func (m *dummyNetlinkMsg) UnmarshalUnsafe(src []byte) {
-	var p primitive.Uint16
-	p.UnmarshalUnsafe(src)
-	m.Foo = uint16(p)
-}
-
 func TestParseMessage(t *testing.T) {
+	dummyNetlinkMsg := primitive.Uint16(0x3130)
 	tests := []struct {
 		desc  string
 		input []byte
 
 		header  linux.NetlinkMessageHeader
-		dataMsg *dummyNetlinkMsg
+		dataMsg marshal.Marshallable
 		restLen int
 		ok      bool
 	}{
@@ -72,9 +53,7 @@ func TestParseMessage(t *testing.T) {
 				Seq:    3,
 				PortID: 4,
 			},
-			dataMsg: &dummyNetlinkMsg{
-				Foo: 0x3130,
-			},
+			dataMsg: &dummyNetlinkMsg,
 			restLen: 0,
 			ok:      true,
 		},
@@ -96,9 +75,7 @@ func TestParseMessage(t *testing.T) {
 				Seq:    3,
 				PortID: 4,
 			},
-			dataMsg: &dummyNetlinkMsg{
-				Foo: 0x3130,
-			},
+			dataMsg: &dummyNetlinkMsg,
 			restLen: 1,
 			ok:      true,
 		},
@@ -119,9 +96,7 @@ func TestParseMessage(t *testing.T) {
 				Seq:    3,
 				PortID: 4,
 			},
-			dataMsg: &dummyNetlinkMsg{
-				Foo: 0x3130,
-			},
+			dataMsg: &dummyNetlinkMsg,
 			restLen: 0,
 			ok:      true,
 		},
@@ -143,9 +118,7 @@ func TestParseMessage(t *testing.T) {
 				Seq:    3,
 				PortID: 4,
 			},
-			dataMsg: &dummyNetlinkMsg{
-				Foo: 0x3130,
-			},
+			dataMsg: &dummyNetlinkMsg,
 			restLen: 0,
 			ok:      true,
 		},
@@ -199,11 +172,11 @@ func TestParseMessage(t *testing.T) {
 			t.Errorf("%v: got hdr = %+v, want = %+v", test.desc, msg.Header(), test.header)
 		}
 
-		dataMsg := &dummyNetlinkMsg{}
-		_, dataOk := msg.GetData(dataMsg)
+		var dataMsg primitive.Uint16
+		_, dataOk := msg.GetData(&dataMsg)
 		if !dataOk {
 			t.Errorf("%v: GetData.ok = %v, want = true", test.desc, dataOk)
-		} else if !reflect.DeepEqual(dataMsg, test.dataMsg) {
+		} else if !reflect.DeepEqual(&dataMsg, test.dataMsg) {
 			t.Errorf("%v: GetData.msg = %+v, want = %+v", test.desc, dataMsg, test.dataMsg)
 		}
 
diff --git a/pkg/sentry/socket/netlink/socket.go b/pkg/sentry/socket/netlink/socket.go
index 267155807..19c8f340d 100644
--- a/pkg/sentry/socket/netlink/socket.go
+++ b/pkg/sentry/socket/netlink/socket.go
@@ -223,7 +223,7 @@ func ExtractSockAddr(b []byte) (*linux.SockAddrNetlink, *syserr.Error) {
 	}
 
 	var sa linux.SockAddrNetlink
-	sa.UnmarshalUnsafe(b[:sa.SizeBytes()])
+	sa.UnmarshalUnsafe(b)
 
 	if sa.Family != linux.AF_NETLINK {
 		return nil, syserr.ErrInvalidArgument
-- 
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