Implement standard clock safely

Previously, tcpip.StdClock depended on linking with the unexposed method
time.now to implement tcpip.Clock using the time package. This change
updates the standard clock to not require manually linking to this
unexported method and use publicly documented functions from the time
package.

PiperOrigin-RevId: 371805101

1 files changed, 26 insertions, 0 deletions

diff --git a/pkg/tcpip/stdclock_state.go b/pkg/tcpip/stdclock_state.go
new file mode 100644
index 000000000..795db9181
--- /dev/null
+++ b/pkg/tcpip/stdclock_state.go
@@ -0,0 +1,26 @@
+// Copyright 2021 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tcpip
+
+import "time"
+
+// afterLoad is invoked by stateify.
+func (s *stdClock) afterLoad() {
+	s.baseTime = time.Now()
+
+	s.monotonicMU.Lock()
+	defer s.monotonicMU.Unlock()
+	s.monotonicOffset = s.maxMonotonic
+}