github.com/google/netstack@v0.0.0-20191123085552-55fcc16cd0eb/tcpip/packet_buffer.go (about)

     1  // Copyright 2019 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  //     http://www.apache.org/licenses/LICENSE-2.0
     7  //
     8  // Unless required by applicable law or agreed to in writing, software
     9  // distributed under the License is distributed on an "AS IS" BASIS,
    10  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package tcpip
    15  
    16  import "github.com/google/netstack/tcpip/buffer"
    17  
    18  // A PacketBuffer contains all the data of a network packet.
    19  //
    20  // As a PacketBuffer traverses up the stack, it may be necessary to pass it to
    21  // multiple endpoints. Clone() should be called in such cases so that
    22  // modifications to the Data field do not affect other copies.
    23  //
    24  // +stateify savable
    25  type PacketBuffer struct {
    26  	// Data holds the payload of the packet. For inbound packets, it also
    27  	// holds the headers, which are consumed as the packet moves up the
    28  	// stack. Headers are guaranteed not to be split across views.
    29  	//
    30  	// The bytes backing Data are immutable, but Data itself may be trimmed
    31  	// or otherwise modified.
    32  	Data buffer.VectorisedView
    33  
    34  	// Header holds the headers of outbound packets. As a packet is passed
    35  	// down the stack, each layer adds to Header.
    36  	Header buffer.Prependable
    37  
    38  	// These fields are used by both inbound and outbound packets. They
    39  	// typically overlap with the Data and Header fields.
    40  	//
    41  	// The bytes backing these views are immutable. Each field may be nil
    42  	// if either it has not been set yet or no such header exists (e.g.
    43  	// packets sent via loopback may not have a link header).
    44  	//
    45  	// These fields may be Views into other slices (either Data or Header).
    46  	// SR dosen't support this, so deep copies are necessary in some cases.
    47  	LinkHeader      buffer.View
    48  	NetworkHeader   buffer.View
    49  	TransportHeader buffer.View
    50  }
    51  
    52  // Clone makes a copy of pk. It clones the Data field, which creates a new
    53  // VectorisedView but does not deep copy the underlying bytes.
    54  //
    55  // Clone also does not deep copy any of its other fields.
    56  func (pk PacketBuffer) Clone() PacketBuffer {
    57  	pk.Data = pk.Data.Clone(nil)
    58  	return pk
    59  }