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// Copyright 2019 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 "gvisor.dev/gvisor/pkg/tcpip/buffer"
// A PacketBuffer contains all the data of a network packet.
//
// As a PacketBuffer traverses up the stack, it may be necessary to pass it to
// multiple endpoints. Clone() should be called in such cases so that
// modifications to the Data field do not affect other copies.
//
// +stateify savable
type PacketBuffer struct {
// Data holds the payload of the packet. For inbound packets, it also
// holds the headers, which are consumed as the packet moves up the
// stack. Headers are guaranteed not to be split across views.
//
// The bytes backing Data are immutable, but Data itself may be trimmed
// or otherwise modified.
Data buffer.VectorisedView
// DataOffset is used for GSO output. It is the offset into the Data
// field where the payload of this packet starts.
DataOffset int
// DataSize is used for GSO output. It is the size of this packet's
// payload.
DataSize int
// Header holds the headers of outbound packets generated by the netstack. As
// a packet is passed down the stack, each layer adds to Header.
//
// Note, if a packet is being forwarded at the IP layer, the headers for the
// IP layer and above (transport) will be held in Data as the packet was not
// passed down the stack it arrived at before being forwarded.
Header buffer.Prependable
// These fields are used by both inbound and outbound packets. They
// typically overlap with the Data and Header fields.
//
// The bytes backing these views are immutable. Each field may be nil
// if either it has not been set yet or no such header exists (e.g.
// packets sent via loopback may not have a link header).
//
// These fields may be Views into other slices (either Data or Header).
// SR dosen't support this, so deep copies are necessary in some cases.
LinkHeader buffer.View
NetworkHeader buffer.View
TransportHeader buffer.View
}
// Clone makes a copy of pk. It clones the Data field, which creates a new
// VectorisedView but does not deep copy the underlying bytes.
//
// Clone also does not deep copy any of its other fields.
func (pk PacketBuffer) Clone() PacketBuffer {
pk.Data = pk.Data.Clone(nil)
return pk
}
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