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// 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 tcp contains internal type definitions that are not expected to be
// used by anyone else outside pkg/tcpip.
package tcp
import (
"time"
"gvisor.dev/gvisor/pkg/tcpip"
)
// TSOffset is an offset applied to the value of the TSVal field in the TCP
// Timestamp option.
//
// +stateify savable
type TSOffset struct {
milliseconds uint32
}
// NewTSOffset creates a new TSOffset from milliseconds.
func NewTSOffset(milliseconds uint32) TSOffset {
return TSOffset{
milliseconds: milliseconds,
}
}
// TSVal applies the offset to now and returns the timestamp in milliseconds.
func (offset TSOffset) TSVal(now tcpip.MonotonicTime) uint32 {
return uint32(now.Sub(tcpip.MonotonicTime{}).Milliseconds()) + offset.milliseconds
}
// Elapsed calculates the elapsed time given now and the echoed back timestamp.
func (offset TSOffset) Elapsed(now tcpip.MonotonicTime, tsEcr uint32) time.Duration {
return time.Duration(offset.TSVal(now)-tsEcr) * time.Millisecond
}
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