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// Copyright 2018 Google LLC
//
// 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 channel provides the implemention of channel-based data-link layer
// endpoints. Such endpoints allow injection of inbound packets and store
// outbound packets in a channel.
package channel
import (
"gvisor.googlesource.com/gvisor/pkg/tcpip"
"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
"gvisor.googlesource.com/gvisor/pkg/tcpip/stack"
)
// PacketInfo holds all the information about an outbound packet.
type PacketInfo struct {
Header buffer.View
Payload buffer.View
Proto tcpip.NetworkProtocolNumber
}
// Endpoint is link layer endpoint that stores outbound packets in a channel
// and allows injection of inbound packets.
type Endpoint struct {
dispatcher stack.NetworkDispatcher
mtu uint32
linkAddr tcpip.LinkAddress
// C is where outbound packets are queued.
C chan PacketInfo
}
// New creates a new channel endpoint.
func New(size int, mtu uint32, linkAddr tcpip.LinkAddress) (tcpip.LinkEndpointID, *Endpoint) {
e := &Endpoint{
C: make(chan PacketInfo, size),
mtu: mtu,
linkAddr: linkAddr,
}
return stack.RegisterLinkEndpoint(e), e
}
// Drain removes all outbound packets from the channel and counts them.
func (e *Endpoint) Drain() int {
c := 0
for {
select {
case <-e.C:
c++
default:
return c
}
}
}
// Inject injects an inbound packet.
func (e *Endpoint) Inject(protocol tcpip.NetworkProtocolNumber, vv buffer.VectorisedView) {
e.InjectLinkAddr(protocol, "", vv)
}
// InjectLinkAddr injects an inbound packet with a remote link address.
func (e *Endpoint) InjectLinkAddr(protocol tcpip.NetworkProtocolNumber, remote tcpip.LinkAddress, vv buffer.VectorisedView) {
e.dispatcher.DeliverNetworkPacket(e, remote, "" /* local */, protocol, vv.Clone(nil))
}
// Attach saves the stack network-layer dispatcher for use later when packets
// are injected.
func (e *Endpoint) Attach(dispatcher stack.NetworkDispatcher) {
e.dispatcher = dispatcher
}
// IsAttached implements stack.LinkEndpoint.IsAttached.
func (e *Endpoint) IsAttached() bool {
return e.dispatcher != nil
}
// MTU implements stack.LinkEndpoint.MTU. It returns the value initialized
// during construction.
func (e *Endpoint) MTU() uint32 {
return e.mtu
}
// Capabilities implements stack.LinkEndpoint.Capabilities.
func (*Endpoint) Capabilities() stack.LinkEndpointCapabilities {
return 0
}
// MaxHeaderLength returns the maximum size of the link layer header. Given it
// doesn't have a header, it just returns 0.
func (*Endpoint) MaxHeaderLength() uint16 {
return 0
}
// LinkAddress returns the link address of this endpoint.
func (e *Endpoint) LinkAddress() tcpip.LinkAddress {
return e.linkAddr
}
// WritePacket stores outbound packets into the channel.
func (e *Endpoint) WritePacket(_ *stack.Route, _ *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
p := PacketInfo{
Header: hdr.View(),
Proto: protocol,
Payload: payload.ToView(),
}
select {
case e.C <- p:
default:
}
return nil
}
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