github.com/metacubex/gvisor@v0.0.0-20240320004321-933faba989ec/pkg/tcpip/internal/tcp/tcp.go (about)

     1  // Copyright 2021 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  // Package tcp contains internal type definitions that are not expected to be
    16  // used by anyone else outside pkg/tcpip.
    17  package tcp
    18  
    19  import (
    20  	"time"
    21  
    22  	"github.com/metacubex/gvisor/pkg/tcpip"
    23  )
    24  
    25  // TSOffset is an offset applied to the value of the TSVal field in the TCP
    26  // Timestamp option.
    27  //
    28  // +stateify savable
    29  type TSOffset struct {
    30  	milliseconds uint32
    31  }
    32  
    33  // NewTSOffset creates a new TSOffset from milliseconds.
    34  func NewTSOffset(milliseconds uint32) TSOffset {
    35  	return TSOffset{
    36  		milliseconds: milliseconds,
    37  	}
    38  }
    39  
    40  // TSVal applies the offset to now and returns the timestamp in milliseconds.
    41  func (offset TSOffset) TSVal(now tcpip.MonotonicTime) uint32 {
    42  	return uint32(now.Sub(tcpip.MonotonicTime{}).Milliseconds()) + offset.milliseconds
    43  }
    44  
    45  // Elapsed calculates the elapsed time given now and the echoed back timestamp.
    46  func (offset TSOffset) Elapsed(now tcpip.MonotonicTime, tsEcr uint32) time.Duration {
    47  	return time.Duration(offset.TSVal(now)-tsEcr) * time.Millisecond
    48  }