Use opaque types to represent time

Introduce tcpip.MonotonicTime; replace int64 in tcpip.Clock method
returns with time.Time and MonotonicTime to improve type safety and
ensure that monotonic clock readings are never compared to wall clock
readings.

PiperOrigin-RevId: 375775907

2 files changed, 23 insertions, 10 deletions

diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index 623e069a6..83b589d09 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -17,6 +17,7 @@ package udp
 import (
 	"io"
 	"sync/atomic"
+	"time"
 
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
@@ -34,7 +35,7 @@ type udpPacket struct {
 	destinationAddress tcpip.FullAddress
 	packetInfo         tcpip.IPPacketInfo
 	data               buffer.VectorisedView `state:".(buffer.VectorisedView)"`
-	timestamp          int64
+	receivedAt         time.Time             `state:".(int64)"`
 	// tos stores either the receiveTOS or receiveTClass value.
 	tos uint8
 }
@@ -321,7 +322,7 @@ func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult
 	// Control Messages
 	cm := tcpip.ControlMessages{
 		HasTimestamp: true,
-		Timestamp:    p.timestamp,
+		Timestamp:    p.receivedAt.UnixNano(),
 	}
 	if e.ops.GetReceiveTOS() {
 		cm.HasTOS = true
@@ -1329,7 +1330,7 @@ func (e *endpoint) HandlePacket(id stack.TransportEndpointID, pkt *stack.PacketB
 	packet.packetInfo.LocalAddr = localAddr
 	packet.packetInfo.DestinationAddr = localAddr
 	packet.packetInfo.NIC = pkt.NICID
-	packet.timestamp = e.stack.Clock().NowNanoseconds()
+	packet.receivedAt = e.stack.Clock().Now()
 
 	e.rcvMu.Unlock()
 
diff --git a/pkg/tcpip/transport/udp/endpoint_state.go b/pkg/tcpip/transport/udp/endpoint_state.go
index 4aba68b21..1f638c3f6 100644
--- a/pkg/tcpip/transport/udp/endpoint_state.go
+++ b/pkg/tcpip/transport/udp/endpoint_state.go
@@ -15,26 +15,38 @@
 package udp
 
 import (
+	"time"
+
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
 
+// saveReceivedAt is invoked by stateify.
+func (p *udpPacket) saveReceivedAt() int64 {
+	return p.receivedAt.UnixNano()
+}
+
+// loadReceivedAt is invoked by stateify.
+func (p *udpPacket) loadReceivedAt(nsec int64) {
+	p.receivedAt = time.Unix(0, nsec)
+}
+
 // saveData saves udpPacket.data field.
-func (u *udpPacket) saveData() buffer.VectorisedView {
-	// We cannot save u.data directly as u.data.views may alias to u.views,
+func (p *udpPacket) saveData() buffer.VectorisedView {
+	// We cannot save p.data directly as p.data.views may alias to p.views,
 	// which is not allowed by state framework (in-struct pointer).
-	return u.data.Clone(nil)
+	return p.data.Clone(nil)
 }
 
 // loadData loads udpPacket.data field.
-func (u *udpPacket) loadData(data buffer.VectorisedView) {
-	// NOTE: We cannot do the u.data = data.Clone(u.views[:]) optimization
+func (p *udpPacket) loadData(data buffer.VectorisedView) {
+	// NOTE: We cannot do the p.data = data.Clone(p.views[:]) optimization
 	// here because data.views is not guaranteed to be loaded by now. Plus,
 	// data.views will be allocated anyway so there really is little point
-	// of utilizing u.views for data.views.
-	u.data = data
+	// of utilizing p.views for data.views.
+	p.data = data
 }
 
 // afterLoad is invoked by stateify.