gvisor.dev/gvisor@v0.0.0-20240520182842-f9d4d51c7e0f/pkg/tcpip/link/nested/nested.go (about)

     1  // Copyright 2020 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 nested provides helpers to implement the pattern of nested
    16  // stack.LinkEndpoints.
    17  package nested
    18  
    19  import (
    20  	"gvisor.dev/gvisor/pkg/sync"
    21  	"gvisor.dev/gvisor/pkg/tcpip"
    22  	"gvisor.dev/gvisor/pkg/tcpip/header"
    23  	"gvisor.dev/gvisor/pkg/tcpip/stack"
    24  )
    25  
    26  // Endpoint is a wrapper around stack.LinkEndpoint and stack.NetworkDispatcher
    27  // that can be used to implement nesting safely by providing lifecycle
    28  // concurrency guards.
    29  //
    30  // See the tests in this package for example usage.
    31  type Endpoint struct {
    32  	child    stack.LinkEndpoint
    33  	embedder stack.NetworkDispatcher
    34  
    35  	// mu protects dispatcher.
    36  	mu         sync.RWMutex
    37  	dispatcher stack.NetworkDispatcher
    38  }
    39  
    40  var _ stack.GSOEndpoint = (*Endpoint)(nil)
    41  var _ stack.LinkEndpoint = (*Endpoint)(nil)
    42  var _ stack.NetworkDispatcher = (*Endpoint)(nil)
    43  
    44  // Init initializes a nested.Endpoint that uses embedder as the dispatcher for
    45  // child on Attach.
    46  //
    47  // See the tests in this package for example usage.
    48  func (e *Endpoint) Init(child stack.LinkEndpoint, embedder stack.NetworkDispatcher) {
    49  	e.child = child
    50  	e.embedder = embedder
    51  }
    52  
    53  // DeliverNetworkPacket implements stack.NetworkDispatcher.
    54  func (e *Endpoint) DeliverNetworkPacket(protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
    55  	e.mu.RLock()
    56  	d := e.dispatcher
    57  	e.mu.RUnlock()
    58  	if d != nil {
    59  		d.DeliverNetworkPacket(protocol, pkt)
    60  	}
    61  }
    62  
    63  // DeliverLinkPacket implements stack.NetworkDispatcher.
    64  func (e *Endpoint) DeliverLinkPacket(protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
    65  	e.mu.RLock()
    66  	d := e.dispatcher
    67  	e.mu.RUnlock()
    68  	if d != nil {
    69  		d.DeliverLinkPacket(protocol, pkt)
    70  	}
    71  }
    72  
    73  // Attach implements stack.LinkEndpoint.
    74  func (e *Endpoint) Attach(dispatcher stack.NetworkDispatcher) {
    75  	e.mu.Lock()
    76  	e.dispatcher = dispatcher
    77  	e.mu.Unlock()
    78  	// If we're attaching to a valid dispatcher, pass embedder as the dispatcher
    79  	// to our child, otherwise detach the child by giving it a nil dispatcher.
    80  	var pass stack.NetworkDispatcher
    81  	if dispatcher != nil {
    82  		pass = e.embedder
    83  	}
    84  	e.child.Attach(pass)
    85  }
    86  
    87  // IsAttached implements stack.LinkEndpoint.
    88  func (e *Endpoint) IsAttached() bool {
    89  	e.mu.RLock()
    90  	isAttached := e.dispatcher != nil
    91  	e.mu.RUnlock()
    92  	return isAttached
    93  }
    94  
    95  // MTU implements stack.LinkEndpoint.
    96  func (e *Endpoint) MTU() uint32 {
    97  	return e.child.MTU()
    98  }
    99  
   100  // Capabilities implements stack.LinkEndpoint.
   101  func (e *Endpoint) Capabilities() stack.LinkEndpointCapabilities {
   102  	return e.child.Capabilities()
   103  }
   104  
   105  // MaxHeaderLength implements stack.LinkEndpoint.
   106  func (e *Endpoint) MaxHeaderLength() uint16 {
   107  	return e.child.MaxHeaderLength()
   108  }
   109  
   110  // LinkAddress implements stack.LinkEndpoint.
   111  func (e *Endpoint) LinkAddress() tcpip.LinkAddress {
   112  	return e.child.LinkAddress()
   113  }
   114  
   115  // WritePackets implements stack.LinkEndpoint.
   116  func (e *Endpoint) WritePackets(pkts stack.PacketBufferList) (int, tcpip.Error) {
   117  	return e.child.WritePackets(pkts)
   118  }
   119  
   120  // Wait implements stack.LinkEndpoint.
   121  func (e *Endpoint) Wait() {
   122  	e.child.Wait()
   123  }
   124  
   125  // GSOMaxSize implements stack.GSOEndpoint.
   126  func (e *Endpoint) GSOMaxSize() uint32 {
   127  	if e, ok := e.child.(stack.GSOEndpoint); ok {
   128  		return e.GSOMaxSize()
   129  	}
   130  	return 0
   131  }
   132  
   133  // SupportedGSO implements stack.GSOEndpoint.
   134  func (e *Endpoint) SupportedGSO() stack.SupportedGSO {
   135  	if e, ok := e.child.(stack.GSOEndpoint); ok {
   136  		return e.SupportedGSO()
   137  	}
   138  	return stack.GSONotSupported
   139  }
   140  
   141  // ARPHardwareType implements stack.LinkEndpoint.ARPHardwareType
   142  func (e *Endpoint) ARPHardwareType() header.ARPHardwareType {
   143  	return e.child.ARPHardwareType()
   144  }
   145  
   146  // AddHeader implements stack.LinkEndpoint.AddHeader.
   147  func (e *Endpoint) AddHeader(pkt *stack.PacketBuffer) {
   148  	e.child.AddHeader(pkt)
   149  }
   150  
   151  // ParseHeader implements stack.LinkEndpoint.ParseHeader.
   152  func (e *Endpoint) ParseHeader(pkt *stack.PacketBuffer) bool {
   153  	return e.child.ParseHeader(pkt)
   154  }