1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
|
// Copyright 2018 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 arp implements the ARP network protocol. It is used to resolve
// IPv4 addresses into link-local MAC addresses, and advertises IPv4
// addresses of its stack with the local network.
//
// To use it in the networking stack, pass arp.NewProtocol() as one of the
// network protocols when calling stack.New. Then add an "arp" address to every
// NIC on the stack that should respond to ARP requests. That is:
//
// if err := s.AddAddress(1, arp.ProtocolNumber, "arp"); err != nil {
// // handle err
// }
package arp
import (
"gvisor.dev/gvisor/pkg/tcpip"
"gvisor.dev/gvisor/pkg/tcpip/buffer"
"gvisor.dev/gvisor/pkg/tcpip/header"
"gvisor.dev/gvisor/pkg/tcpip/stack"
)
const (
// ProtocolNumber is the ARP protocol number.
ProtocolNumber = header.ARPProtocolNumber
// ProtocolAddress is the address expected by the ARP endpoint.
ProtocolAddress = tcpip.Address("arp")
)
// endpoint implements stack.NetworkEndpoint.
type endpoint struct {
nicID tcpip.NICID
linkEP stack.LinkEndpoint
linkAddrCache stack.LinkAddressCache
}
// DefaultTTL is unused for ARP. It implements stack.NetworkEndpoint.
func (e *endpoint) DefaultTTL() uint8 {
return 0
}
func (e *endpoint) MTU() uint32 {
lmtu := e.linkEP.MTU()
return lmtu - uint32(e.MaxHeaderLength())
}
func (e *endpoint) NICID() tcpip.NICID {
return e.nicID
}
func (e *endpoint) Capabilities() stack.LinkEndpointCapabilities {
return e.linkEP.Capabilities()
}
func (e *endpoint) ID() *stack.NetworkEndpointID {
return &stack.NetworkEndpointID{ProtocolAddress}
}
func (e *endpoint) PrefixLen() int {
return 0
}
func (e *endpoint) MaxHeaderLength() uint16 {
return e.linkEP.MaxHeaderLength() + header.ARPSize
}
func (e *endpoint) Close() {}
func (e *endpoint) WritePacket(*stack.Route, *stack.GSO, stack.NetworkHeaderParams, stack.PacketLooping, tcpip.PacketBuffer) *tcpip.Error {
return tcpip.ErrNotSupported
}
// WritePackets implements stack.NetworkEndpoint.WritePackets.
func (e *endpoint) WritePackets(*stack.Route, *stack.GSO, []tcpip.PacketBuffer, stack.NetworkHeaderParams, stack.PacketLooping) (int, *tcpip.Error) {
return 0, tcpip.ErrNotSupported
}
func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, loop stack.PacketLooping, pkt tcpip.PacketBuffer) *tcpip.Error {
return tcpip.ErrNotSupported
}
func (e *endpoint) HandlePacket(r *stack.Route, pkt tcpip.PacketBuffer) {
v := pkt.Data.First()
h := header.ARP(v)
if !h.IsValid() {
return
}
switch h.Op() {
case header.ARPRequest:
localAddr := tcpip.Address(h.ProtocolAddressTarget())
if e.linkAddrCache.CheckLocalAddress(e.nicID, header.IPv4ProtocolNumber, localAddr) == 0 {
return // we have no useful answer, ignore the request
}
hdr := buffer.NewPrependable(int(e.linkEP.MaxHeaderLength()) + header.ARPSize)
packet := header.ARP(hdr.Prepend(header.ARPSize))
packet.SetIPv4OverEthernet()
packet.SetOp(header.ARPReply)
copy(packet.HardwareAddressSender(), r.LocalLinkAddress[:])
copy(packet.ProtocolAddressSender(), h.ProtocolAddressTarget())
copy(packet.HardwareAddressTarget(), h.HardwareAddressSender())
copy(packet.ProtocolAddressTarget(), h.ProtocolAddressSender())
e.linkEP.WritePacket(r, nil /* gso */, ProtocolNumber, tcpip.PacketBuffer{
Header: hdr,
})
fallthrough // also fill the cache from requests
case header.ARPReply:
addr := tcpip.Address(h.ProtocolAddressSender())
linkAddr := tcpip.LinkAddress(h.HardwareAddressSender())
e.linkAddrCache.AddLinkAddress(e.nicID, addr, linkAddr)
}
}
// protocol implements stack.NetworkProtocol and stack.LinkAddressResolver.
type protocol struct {
}
func (p *protocol) Number() tcpip.NetworkProtocolNumber { return ProtocolNumber }
func (p *protocol) MinimumPacketSize() int { return header.ARPSize }
func (p *protocol) DefaultPrefixLen() int { return 0 }
func (*protocol) ParseAddresses(v buffer.View) (src, dst tcpip.Address) {
h := header.ARP(v)
return tcpip.Address(h.ProtocolAddressSender()), ProtocolAddress
}
func (p *protocol) NewEndpoint(nicID tcpip.NICID, addrWithPrefix tcpip.AddressWithPrefix, linkAddrCache stack.LinkAddressCache, dispatcher stack.TransportDispatcher, sender stack.LinkEndpoint) (stack.NetworkEndpoint, *tcpip.Error) {
if addrWithPrefix.Address != ProtocolAddress {
return nil, tcpip.ErrBadLocalAddress
}
return &endpoint{
nicID: nicID,
linkEP: sender,
linkAddrCache: linkAddrCache,
}, nil
}
// LinkAddressProtocol implements stack.LinkAddressResolver.
func (*protocol) LinkAddressProtocol() tcpip.NetworkProtocolNumber {
return header.IPv4ProtocolNumber
}
// LinkAddressRequest implements stack.LinkAddressResolver.
func (*protocol) LinkAddressRequest(addr, localAddr tcpip.Address, linkEP stack.LinkEndpoint) *tcpip.Error {
r := &stack.Route{
RemoteLinkAddress: broadcastMAC,
}
hdr := buffer.NewPrependable(int(linkEP.MaxHeaderLength()) + header.ARPSize)
h := header.ARP(hdr.Prepend(header.ARPSize))
h.SetIPv4OverEthernet()
h.SetOp(header.ARPRequest)
copy(h.HardwareAddressSender(), linkEP.LinkAddress())
copy(h.ProtocolAddressSender(), localAddr)
copy(h.ProtocolAddressTarget(), addr)
return linkEP.WritePacket(r, nil /* gso */, ProtocolNumber, tcpip.PacketBuffer{
Header: hdr,
})
}
// ResolveStaticAddress implements stack.LinkAddressResolver.
func (*protocol) ResolveStaticAddress(addr tcpip.Address) (tcpip.LinkAddress, bool) {
if addr == header.IPv4Broadcast {
return broadcastMAC, true
}
if header.IsV4MulticastAddress(addr) {
// RFC 1112 Host Extensions for IP Multicasting
//
// 6.4. Extensions to an Ethernet Local Network Module:
//
// An IP host group address is mapped to an Ethernet multicast
// address by placing the low-order 23-bits of the IP address
// into the low-order 23 bits of the Ethernet multicast address
// 01-00-5E-00-00-00 (hex).
return tcpip.LinkAddress([]byte{
0x01,
0x00,
0x5e,
addr[header.IPv4AddressSize-3] & 0x7f,
addr[header.IPv4AddressSize-2],
addr[header.IPv4AddressSize-1],
}), true
}
return "", false
}
// SetOption implements NetworkProtocol.
func (p *protocol) SetOption(option interface{}) *tcpip.Error {
return tcpip.ErrUnknownProtocolOption
}
// Option implements NetworkProtocol.
func (p *protocol) Option(option interface{}) *tcpip.Error {
return tcpip.ErrUnknownProtocolOption
}
var broadcastMAC = tcpip.LinkAddress([]byte{0xff, 0xff, 0xff, 0xff, 0xff, 0xff})
// NewProtocol returns an ARP network protocol.
func NewProtocol() stack.NetworkProtocol {
return &protocol{}
}
|
