inet.af/netstack@v0.0.0-20220214151720-7585b01ddccf/tcpip/transport/tcp/segment_state.go (about)

     1  // Copyright 2018 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
    16  
    17  import (
    18  	"inet.af/netstack/tcpip/buffer"
    19  )
    20  
    21  // saveData is invoked by stateify.
    22  func (s *segment) saveData() buffer.VectorisedView {
    23  	// We cannot save s.data directly as s.data.views may alias to s.views,
    24  	// which is not allowed by state framework (in-struct pointer).
    25  	vs := make([]buffer.View, len(s.data.Views()))
    26  	for i, v := range s.data.Views() {
    27  		vs[i] = v
    28  	}
    29  	return buffer.NewVectorisedView(s.data.Size(), vs)
    30  }
    31  
    32  // loadData is invoked by stateify.
    33  func (s *segment) loadData(data buffer.VectorisedView) {
    34  	// NOTE: We cannot do the s.data = data.Clone(s.views[:]) optimization
    35  	// here because data.views is not guaranteed to be loaded by now. Plus,
    36  	// data.views will be allocated anyway so there really is little point
    37  	// of utilizing s.views for data.views.
    38  	s.data = data
    39  }
    40  
    41  // saveOptions is invoked by stateify.
    42  func (s *segment) saveOptions() []byte {
    43  	// We cannot save s.options directly as it may point to s.data's trimmed
    44  	// tail, which is not allowed by state framework (in-struct pointer).
    45  	b := make([]byte, 0, cap(s.options))
    46  	return append(b, s.options...)
    47  }
    48  
    49  // loadOptions is invoked by stateify.
    50  func (s *segment) loadOptions(options []byte) {
    51  	// NOTE: We cannot point s.options back into s.data's trimmed tail. But
    52  	// it is OK as they do not need to aliased. Plus, options is already
    53  	// allocated so there is no cost here.
    54  	s.options = options
    55  }