github.com/FlowerWrong/netstack@v0.0.0-20191009141956-e5848263af28/tcpip/link/channel/channel.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 channel provides the implemention of channel-based data-link layer
    16  // endpoints. Such endpoints allow injection of inbound packets and store
    17  // outbound packets in a channel.
    18  package channel
    19  
    20  import (
    21  	"github.com/FlowerWrong/netstack/tcpip"
    22  	"github.com/FlowerWrong/netstack/tcpip/buffer"
    23  	"github.com/FlowerWrong/netstack/tcpip/stack"
    24  )
    25  
    26  // PacketInfo holds all the information about an outbound packet.
    27  type PacketInfo struct {
    28  	Header  buffer.View
    29  	Payload buffer.View
    30  	Proto   tcpip.NetworkProtocolNumber
    31  	GSO     *stack.GSO
    32  }
    33  
    34  // Endpoint is link layer endpoint that stores outbound packets in a channel
    35  // and allows injection of inbound packets.
    36  type Endpoint struct {
    37  	dispatcher stack.NetworkDispatcher
    38  	mtu        uint32
    39  	linkAddr   tcpip.LinkAddress
    40  	GSO        bool
    41  
    42  	// C is where outbound packets are queued.
    43  	C chan PacketInfo
    44  }
    45  
    46  // New creates a new channel endpoint.
    47  func New(size int, mtu uint32, linkAddr tcpip.LinkAddress) *Endpoint {
    48  	return &Endpoint{
    49  		C:        make(chan PacketInfo, size),
    50  		mtu:      mtu,
    51  		linkAddr: linkAddr,
    52  	}
    53  }
    54  
    55  // Drain removes all outbound packets from the channel and counts them.
    56  func (e *Endpoint) Drain() int {
    57  	c := 0
    58  	for {
    59  		select {
    60  		case <-e.C:
    61  			c++
    62  		default:
    63  			return c
    64  		}
    65  	}
    66  }
    67  
    68  // Inject injects an inbound packet.
    69  func (e *Endpoint) Inject(protocol tcpip.NetworkProtocolNumber, vv buffer.VectorisedView) {
    70  	e.InjectLinkAddr(protocol, "", vv)
    71  }
    72  
    73  // InjectLinkAddr injects an inbound packet with a remote link address.
    74  func (e *Endpoint) InjectLinkAddr(protocol tcpip.NetworkProtocolNumber, remote tcpip.LinkAddress, vv buffer.VectorisedView) {
    75  	e.dispatcher.DeliverNetworkPacket(e, remote, "" /* local */, protocol, vv.Clone(nil))
    76  }
    77  
    78  // Attach saves the stack network-layer dispatcher for use later when packets
    79  // are injected.
    80  func (e *Endpoint) Attach(dispatcher stack.NetworkDispatcher) {
    81  	e.dispatcher = dispatcher
    82  }
    83  
    84  // IsAttached implements stack.LinkEndpoint.IsAttached.
    85  func (e *Endpoint) IsAttached() bool {
    86  	return e.dispatcher != nil
    87  }
    88  
    89  // MTU implements stack.LinkEndpoint.MTU. It returns the value initialized
    90  // during construction.
    91  func (e *Endpoint) MTU() uint32 {
    92  	return e.mtu
    93  }
    94  
    95  // Capabilities implements stack.LinkEndpoint.Capabilities.
    96  func (e *Endpoint) Capabilities() stack.LinkEndpointCapabilities {
    97  	caps := stack.LinkEndpointCapabilities(0)
    98  	if e.GSO {
    99  		caps |= stack.CapabilityGSO
   100  	}
   101  	return caps
   102  }
   103  
   104  // GSOMaxSize returns the maximum GSO packet size.
   105  func (*Endpoint) GSOMaxSize() uint32 {
   106  	return 1 << 15
   107  }
   108  
   109  // MaxHeaderLength returns the maximum size of the link layer header. Given it
   110  // doesn't have a header, it just returns 0.
   111  func (*Endpoint) MaxHeaderLength() uint16 {
   112  	return 0
   113  }
   114  
   115  // LinkAddress returns the link address of this endpoint.
   116  func (e *Endpoint) LinkAddress() tcpip.LinkAddress {
   117  	return e.linkAddr
   118  }
   119  
   120  // WritePacket stores outbound packets into the channel.
   121  func (e *Endpoint) WritePacket(_ *stack.Route, gso *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
   122  	p := PacketInfo{
   123  		Header:  hdr.View(),
   124  		Proto:   protocol,
   125  		Payload: payload.ToView(),
   126  		GSO:     gso,
   127  	}
   128  
   129  	select {
   130  	case e.C <- p:
   131  	default:
   132  	}
   133  
   134  	return nil
   135  }
   136  
   137  // Wait implements stack.LinkEndpoint.Wait.
   138  func (*Endpoint) Wait() {}