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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 stack
import (
"gvisor.dev/gvisor/pkg/tcpip"
"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.
type PacketBuffer struct {
_ noCopy
// PacketBufferEntry is used to build an intrusive list of
// PacketBuffers.
PacketBufferEntry
// 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
// Header holds the headers of outbound packets. As a packet is passed
// down the stack, each layer adds to Header. Note that forwarded
// packets don't populate Headers on their way out -- their headers and
// payload are never parsed out and remain in Data.
//
// TODO(gvisor.dev/issue/170): Forwarded packets don't currently
// populate Header, but should. This will be doable once early parsing
// (https://github.com/google/gvisor/pull/1995) is supported.
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
// Hash is the transport layer hash of this packet. A value of zero
// indicates no valid hash has been set.
Hash uint32
// Owner is implemented by task to get the uid and gid.
// Only set for locally generated packets.
Owner tcpip.PacketOwner
// The following fields are only set by the qdisc layer when the packet
// is added to a queue.
EgressRoute *Route
GSOOptions *GSO
NetworkProtocolNumber tcpip.NetworkProtocolNumber
// NatDone indicates if the packet has been manipulated as per NAT
// iptables rule.
NatDone bool
}
// 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.
//
// FIXME(b/153685824): Data gets copied but not other header references.
func (pk *PacketBuffer) Clone() *PacketBuffer {
return &PacketBuffer{
PacketBufferEntry: pk.PacketBufferEntry,
Data: pk.Data.Clone(nil),
Header: pk.Header,
LinkHeader: pk.LinkHeader,
NetworkHeader: pk.NetworkHeader,
TransportHeader: pk.TransportHeader,
Hash: pk.Hash,
Owner: pk.Owner,
EgressRoute: pk.EgressRoute,
GSOOptions: pk.GSOOptions,
NetworkProtocolNumber: pk.NetworkProtocolNumber,
NatDone: pk.NatDone,
}
}
// noCopy may be embedded into structs which must not be copied
// after the first use.
//
// See https://golang.org/issues/8005#issuecomment-190753527
// for details.
type noCopy struct{}
// Lock is a no-op used by -copylocks checker from `go vet`.
func (*noCopy) Lock() {}
func (*noCopy) Unlock() {}
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