forked from bnb-chain/bsc
-
Notifications
You must be signed in to change notification settings - Fork 0
/
lookup.go
226 lines (205 loc) · 5.96 KB
/
lookup.go
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
217
218
219
220
221
222
223
224
225
226
// Copyright 2019 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package discover
import (
"context"
"time"
"github.com/demindsmr/bsc/p2p/enode"
)
// lookup performs a network search for nodes close to the given target. It approaches the
// target by querying nodes that are closer to it on each iteration. The given target does
// not need to be an actual node identifier.
type lookup struct {
tab *Table
queryfunc func(*node) ([]*node, error)
replyCh chan []*node
cancelCh <-chan struct{}
asked, seen map[enode.ID]bool
result nodesByDistance
replyBuffer []*node
queries int
}
type queryFunc func(*node) ([]*node, error)
func newLookup(ctx context.Context, tab *Table, target enode.ID, q queryFunc) *lookup {
it := &lookup{
tab: tab,
queryfunc: q,
asked: make(map[enode.ID]bool),
seen: make(map[enode.ID]bool),
result: nodesByDistance{target: target},
replyCh: make(chan []*node, alpha),
cancelCh: ctx.Done(),
queries: -1,
}
// Don't query further if we hit ourself.
// Unlikely to happen often in practice.
it.asked[tab.self().ID()] = true
return it
}
// run runs the lookup to completion and returns the closest nodes found.
func (it *lookup) run() []*enode.Node {
for it.advance() {
}
return unwrapNodes(it.result.entries)
}
// advance advances the lookup until any new nodes have been found.
// It returns false when the lookup has ended.
func (it *lookup) advance() bool {
for it.startQueries() {
select {
case nodes := <-it.replyCh:
it.replyBuffer = it.replyBuffer[:0]
for _, n := range nodes {
if n != nil && !it.seen[n.ID()] {
it.seen[n.ID()] = true
it.result.push(n, bucketSize)
it.replyBuffer = append(it.replyBuffer, n)
}
}
it.queries--
if len(it.replyBuffer) > 0 {
return true
}
case <-it.cancelCh:
it.shutdown()
}
}
return false
}
func (it *lookup) shutdown() {
for it.queries > 0 {
<-it.replyCh
it.queries--
}
it.queryfunc = nil
it.replyBuffer = nil
}
func (it *lookup) startQueries() bool {
if it.queryfunc == nil {
return false
}
// The first query returns nodes from the local table.
if it.queries == -1 {
closest := it.tab.findnodeByID(it.result.target, bucketSize, false)
// Avoid finishing the lookup too quickly if table is empty. It'd be better to wait
// for the table to fill in this case, but there is no good mechanism for that
// yet.
if len(closest.entries) == 0 {
it.slowdown()
}
it.queries = 1
it.replyCh <- closest.entries
return true
}
// Ask the closest nodes that we haven't asked yet.
for i := 0; i < len(it.result.entries) && it.queries < alpha; i++ {
n := it.result.entries[i]
if !it.asked[n.ID()] {
it.asked[n.ID()] = true
it.queries++
go it.query(n, it.replyCh)
}
}
// The lookup ends when no more nodes can be asked.
return it.queries > 0
}
func (it *lookup) slowdown() {
sleep := time.NewTimer(1 * time.Second)
defer sleep.Stop()
select {
case <-sleep.C:
case <-it.tab.closeReq:
}
}
func (it *lookup) query(n *node, reply chan<- []*node) {
fails := it.tab.db.FindFails(n.ID(), n.IP())
r, err := it.queryfunc(n)
if err == errClosed {
// Avoid recording failures on shutdown.
reply <- nil
return
} else if len(r) == 0 {
fails++
it.tab.db.UpdateFindFails(n.ID(), n.IP(), fails)
// Remove the node from the local table if it fails to return anything useful too
// many times, but only if there are enough other nodes in the bucket.
dropped := false
if fails >= maxFindnodeFailures && it.tab.bucketLen(n.ID()) >= bucketSize/2 {
dropped = true
it.tab.delete(n)
}
it.tab.log.Trace("FINDNODE failed", "id", n.ID(), "failcount", fails, "dropped", dropped, "err", err)
} else if fails > 0 {
// Reset failure counter because it counts _consecutive_ failures.
it.tab.db.UpdateFindFails(n.ID(), n.IP(), 0)
}
// Grab as many nodes as possible. Some of them might not be alive anymore, but we'll
// just remove those again during revalidation.
for _, n := range r {
it.tab.addSeenNode(n)
}
reply <- r
}
// lookupIterator performs lookup operations and iterates over all seen nodes.
// When a lookup finishes, a new one is created through nextLookup.
type lookupIterator struct {
buffer []*node
nextLookup lookupFunc
ctx context.Context
cancel func()
lookup *lookup
}
type lookupFunc func(ctx context.Context) *lookup
func newLookupIterator(ctx context.Context, next lookupFunc) *lookupIterator {
ctx, cancel := context.WithCancel(ctx)
return &lookupIterator{ctx: ctx, cancel: cancel, nextLookup: next}
}
// Node returns the current node.
func (it *lookupIterator) Node() *enode.Node {
if len(it.buffer) == 0 {
return nil
}
return unwrapNode(it.buffer[0])
}
// Next moves to the next node.
func (it *lookupIterator) Next() bool {
// Consume next node in buffer.
if len(it.buffer) > 0 {
it.buffer = it.buffer[1:]
}
// Advance the lookup to refill the buffer.
for len(it.buffer) == 0 {
if it.ctx.Err() != nil {
it.lookup = nil
it.buffer = nil
return false
}
if it.lookup == nil {
it.lookup = it.nextLookup(it.ctx)
continue
}
if !it.lookup.advance() {
it.lookup = nil
continue
}
it.buffer = it.lookup.replyBuffer
}
return true
}
// Close ends the iterator.
func (it *lookupIterator) Close() {
it.cancel()
}