plugeth/p2p/discover/table.go

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2015-07-07 00:54:22 +00:00
// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
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//
// The go-ethereum library is free software: you can redistribute it and/or modify
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// 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,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// 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/>.
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// Package discover implements the Node Discovery Protocol.
//
// The Node Discovery protocol provides a way to find RLPx nodes that
// can be connected to. It uses a Kademlia-like protocol to maintain a
// distributed database of the IDs and endpoints of all listening
// nodes.
package discover
import (
crand "crypto/rand"
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"encoding/binary"
"fmt"
mrand "math/rand"
"net"
"sort"
"sync"
"time"
"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/p2p/netutil"
)
const (
alpha = 3 // Kademlia concurrency factor
bucketSize = 16 // Kademlia bucket size
maxReplacements = 10 // Size of per-bucket replacement list
// We keep buckets for the upper 1/15 of distances because
// it's very unlikely we'll ever encounter a node that's closer.
hashBits = len(common.Hash{}) * 8
nBuckets = hashBits / 15 // Number of buckets
bucketMinDistance = hashBits - nBuckets // Log distance of closest bucket
// IP address limits.
bucketIPLimit, bucketSubnet = 2, 24 // at most 2 addresses from the same /24
tableIPLimit, tableSubnet = 10, 24
p2p/discover: move bond logic from table to transport (#17048) * p2p/discover: move bond logic from table to transport This commit moves node endpoint verification (bonding) from the table to the UDP transport implementation. Previously, adding a node to the table entailed pinging the node if needed. With this change, the ping-back logic is embedded in the packet handler at a lower level. It is easy to verify that the basic protocol is unchanged: we still require a valid pong reply from the node before findnode is accepted. The node database tracked the time of last ping sent to the node and time of last valid pong received from the node. Node endpoints are considered verified when a valid pong is received and the time of last pong was called 'bond time'. The time of last ping sent was unused. In this commit, the last ping database entry is repurposed to mean last ping _received_. This entry is now used to track whether the node needs to be pinged back. The other big change is how nodes are added to the table. We used to add nodes in Table.bond, which ran when a remote node pinged us or when we encountered the node in a neighbors reply. The transport now adds to the table directly after the endpoint is verified through ping. To ensure that the Table can't be filled just by pinging the node repeatedly, we retain the isInitDone check. During init, only nodes from neighbors replies are added. * p2p/discover: reduce findnode failure counter on success * p2p/discover: remove unused parameter of loadSeedNodes * p2p/discover: improve ping-back check and comments * p2p/discover: add neighbors reply nodes always, not just during init
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maxFindnodeFailures = 5 // Nodes exceeding this limit are dropped
refreshInterval = 30 * time.Minute
revalidateInterval = 10 * time.Second
copyNodesInterval = 30 * time.Second
seedMinTableTime = 5 * time.Minute
seedCount = 30
seedMaxAge = 5 * 24 * time.Hour
)
type Table struct {
mutex sync.Mutex // protects buckets, bucket content, nursery, rand
buckets [nBuckets]*bucket // index of known nodes by distance
nursery []*Node // bootstrap nodes
rand *mrand.Rand // source of randomness, periodically reseeded
ips netutil.DistinctNetSet
db *nodeDB // database of known nodes
refreshReq chan chan struct{}
initDone chan struct{}
closeReq chan struct{}
closed chan struct{}
nodeAddedHook func(*Node) // for testing
net transport
self *Node // metadata of the local node
}
// transport is implemented by the UDP transport.
// it is an interface so we can test without opening lots of UDP
// sockets and without generating a private key.
type transport interface {
ping(NodeID, *net.UDPAddr) error
findnode(toid NodeID, addr *net.UDPAddr, target NodeID) ([]*Node, error)
close()
}
// bucket contains nodes, ordered by their last activity. the entry
// that was most recently active is the first element in entries.
type bucket struct {
entries []*Node // live entries, sorted by time of last contact
replacements []*Node // recently seen nodes to be used if revalidation fails
ips netutil.DistinctNetSet
}
func newTable(t transport, ourID NodeID, ourAddr *net.UDPAddr, nodeDBPath string, bootnodes []*Node) (*Table, error) {
// If no node database was given, use an in-memory one
p2p/discover: move bond logic from table to transport (#17048) * p2p/discover: move bond logic from table to transport This commit moves node endpoint verification (bonding) from the table to the UDP transport implementation. Previously, adding a node to the table entailed pinging the node if needed. With this change, the ping-back logic is embedded in the packet handler at a lower level. It is easy to verify that the basic protocol is unchanged: we still require a valid pong reply from the node before findnode is accepted. The node database tracked the time of last ping sent to the node and time of last valid pong received from the node. Node endpoints are considered verified when a valid pong is received and the time of last pong was called 'bond time'. The time of last ping sent was unused. In this commit, the last ping database entry is repurposed to mean last ping _received_. This entry is now used to track whether the node needs to be pinged back. The other big change is how nodes are added to the table. We used to add nodes in Table.bond, which ran when a remote node pinged us or when we encountered the node in a neighbors reply. The transport now adds to the table directly after the endpoint is verified through ping. To ensure that the Table can't be filled just by pinging the node repeatedly, we retain the isInitDone check. During init, only nodes from neighbors replies are added. * p2p/discover: reduce findnode failure counter on success * p2p/discover: remove unused parameter of loadSeedNodes * p2p/discover: improve ping-back check and comments * p2p/discover: add neighbors reply nodes always, not just during init
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db, err := newNodeDB(nodeDBPath, nodeDBVersion, ourID)
if err != nil {
return nil, err
}
tab := &Table{
net: t,
db: db,
self: NewNode(ourID, ourAddr.IP, uint16(ourAddr.Port), uint16(ourAddr.Port)),
refreshReq: make(chan chan struct{}),
initDone: make(chan struct{}),
closeReq: make(chan struct{}),
closed: make(chan struct{}),
rand: mrand.New(mrand.NewSource(0)),
ips: netutil.DistinctNetSet{Subnet: tableSubnet, Limit: tableIPLimit},
}
if err := tab.setFallbackNodes(bootnodes); err != nil {
return nil, err
}
for i := range tab.buckets {
tab.buckets[i] = &bucket{
ips: netutil.DistinctNetSet{Subnet: bucketSubnet, Limit: bucketIPLimit},
}
}
tab.seedRand()
p2p/discover: move bond logic from table to transport (#17048) * p2p/discover: move bond logic from table to transport This commit moves node endpoint verification (bonding) from the table to the UDP transport implementation. Previously, adding a node to the table entailed pinging the node if needed. With this change, the ping-back logic is embedded in the packet handler at a lower level. It is easy to verify that the basic protocol is unchanged: we still require a valid pong reply from the node before findnode is accepted. The node database tracked the time of last ping sent to the node and time of last valid pong received from the node. Node endpoints are considered verified when a valid pong is received and the time of last pong was called 'bond time'. The time of last ping sent was unused. In this commit, the last ping database entry is repurposed to mean last ping _received_. This entry is now used to track whether the node needs to be pinged back. The other big change is how nodes are added to the table. We used to add nodes in Table.bond, which ran when a remote node pinged us or when we encountered the node in a neighbors reply. The transport now adds to the table directly after the endpoint is verified through ping. To ensure that the Table can't be filled just by pinging the node repeatedly, we retain the isInitDone check. During init, only nodes from neighbors replies are added. * p2p/discover: reduce findnode failure counter on success * p2p/discover: remove unused parameter of loadSeedNodes * p2p/discover: improve ping-back check and comments * p2p/discover: add neighbors reply nodes always, not just during init
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tab.loadSeedNodes()
// Start the background expiration goroutine after loading seeds so that the search for
// seed nodes also considers older nodes that would otherwise be removed by the
// expiration.
tab.db.ensureExpirer()
go tab.loop()
return tab, nil
}
func (tab *Table) seedRand() {
var b [8]byte
crand.Read(b[:])
tab.mutex.Lock()
tab.rand.Seed(int64(binary.BigEndian.Uint64(b[:])))
tab.mutex.Unlock()
}
// Self returns the local node.
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// The returned node should not be modified by the caller.
func (tab *Table) Self() *Node {
return tab.self
}
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// ReadRandomNodes fills the given slice with random nodes from the
// table. It will not write the same node more than once. The nodes in
// the slice are copies and can be modified by the caller.
func (tab *Table) ReadRandomNodes(buf []*Node) (n int) {
if !tab.isInitDone() {
return 0
}
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tab.mutex.Lock()
defer tab.mutex.Unlock()
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// Find all non-empty buckets and get a fresh slice of their entries.
var buckets [][]*Node
for _, b := range &tab.buckets {
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if len(b.entries) > 0 {
buckets = append(buckets, b.entries)
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}
}
if len(buckets) == 0 {
return 0
}
// Shuffle the buckets.
for i := len(buckets) - 1; i > 0; i-- {
j := tab.rand.Intn(len(buckets))
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buckets[i], buckets[j] = buckets[j], buckets[i]
}
// Move head of each bucket into buf, removing buckets that become empty.
var i, j int
for ; i < len(buf); i, j = i+1, (j+1)%len(buckets) {
b := buckets[j]
buf[i] = &(*b[0])
buckets[j] = b[1:]
if len(b) == 1 {
buckets = append(buckets[:j], buckets[j+1:]...)
}
if len(buckets) == 0 {
break
}
}
return i + 1
}
// Close terminates the network listener and flushes the node database.
func (tab *Table) Close() {
select {
case <-tab.closed:
// already closed.
case tab.closeReq <- struct{}{}:
<-tab.closed // wait for refreshLoop to end.
}
}
// setFallbackNodes sets the initial points of contact. These nodes
// are used to connect to the network if the table is empty and there
// are no known nodes in the database.
func (tab *Table) setFallbackNodes(nodes []*Node) error {
for _, n := range nodes {
if err := n.validateComplete(); err != nil {
return fmt.Errorf("bad bootstrap/fallback node %q (%v)", n, err)
}
}
tab.nursery = make([]*Node, 0, len(nodes))
for _, n := range nodes {
cpy := *n
// Recompute cpy.sha because the node might not have been
// created by NewNode or ParseNode.
cpy.sha = crypto.Keccak256Hash(n.ID[:])
tab.nursery = append(tab.nursery, &cpy)
}
return nil
}
// isInitDone returns whether the table's initial seeding procedure has completed.
func (tab *Table) isInitDone() bool {
select {
case <-tab.initDone:
return true
default:
return false
}
}
// Resolve searches for a specific node with the given ID.
// It returns nil if the node could not be found.
func (tab *Table) Resolve(targetID NodeID) *Node {
// If the node is present in the local table, no
// network interaction is required.
hash := crypto.Keccak256Hash(targetID[:])
tab.mutex.Lock()
cl := tab.closest(hash, 1)
tab.mutex.Unlock()
if len(cl.entries) > 0 && cl.entries[0].ID == targetID {
return cl.entries[0]
}
// Otherwise, do a network lookup.
result := tab.Lookup(targetID)
for _, n := range result {
if n.ID == targetID {
return n
}
}
return nil
}
// 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.
func (tab *Table) Lookup(targetID NodeID) []*Node {
return tab.lookup(targetID, true)
}
func (tab *Table) lookup(targetID NodeID, refreshIfEmpty bool) []*Node {
var (
target = crypto.Keccak256Hash(targetID[:])
asked = make(map[NodeID]bool)
seen = make(map[NodeID]bool)
reply = make(chan []*Node, alpha)
pendingQueries = 0
result *nodesByDistance
)
// don't query further if we hit ourself.
// unlikely to happen often in practice.
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asked[tab.self.ID] = true
for {
tab.mutex.Lock()
// generate initial result set
result = tab.closest(target, bucketSize)
tab.mutex.Unlock()
if len(result.entries) > 0 || !refreshIfEmpty {
break
}
// The result set is empty, all nodes were dropped, refresh.
// We actually wait for the refresh to complete here. The very
// first query will hit this case and run the bootstrapping
// logic.
<-tab.refresh()
refreshIfEmpty = false
}
for {
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// ask the alpha closest nodes that we haven't asked yet
for i := 0; i < len(result.entries) && pendingQueries < alpha; i++ {
n := result.entries[i]
if !asked[n.ID] {
asked[n.ID] = true
pendingQueries++
p2p/discover: move bond logic from table to transport (#17048) * p2p/discover: move bond logic from table to transport This commit moves node endpoint verification (bonding) from the table to the UDP transport implementation. Previously, adding a node to the table entailed pinging the node if needed. With this change, the ping-back logic is embedded in the packet handler at a lower level. It is easy to verify that the basic protocol is unchanged: we still require a valid pong reply from the node before findnode is accepted. The node database tracked the time of last ping sent to the node and time of last valid pong received from the node. Node endpoints are considered verified when a valid pong is received and the time of last pong was called 'bond time'. The time of last ping sent was unused. In this commit, the last ping database entry is repurposed to mean last ping _received_. This entry is now used to track whether the node needs to be pinged back. The other big change is how nodes are added to the table. We used to add nodes in Table.bond, which ran when a remote node pinged us or when we encountered the node in a neighbors reply. The transport now adds to the table directly after the endpoint is verified through ping. To ensure that the Table can't be filled just by pinging the node repeatedly, we retain the isInitDone check. During init, only nodes from neighbors replies are added. * p2p/discover: reduce findnode failure counter on success * p2p/discover: remove unused parameter of loadSeedNodes * p2p/discover: improve ping-back check and comments * p2p/discover: add neighbors reply nodes always, not just during init
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go tab.findnode(n, targetID, reply)
}
}
if pendingQueries == 0 {
// we have asked all closest nodes, stop the search
break
}
// wait for the next reply
for _, n := range <-reply {
if n != nil && !seen[n.ID] {
seen[n.ID] = true
result.push(n, bucketSize)
}
}
pendingQueries--
}
return result.entries
}
p2p/discover: move bond logic from table to transport (#17048) * p2p/discover: move bond logic from table to transport This commit moves node endpoint verification (bonding) from the table to the UDP transport implementation. Previously, adding a node to the table entailed pinging the node if needed. With this change, the ping-back logic is embedded in the packet handler at a lower level. It is easy to verify that the basic protocol is unchanged: we still require a valid pong reply from the node before findnode is accepted. The node database tracked the time of last ping sent to the node and time of last valid pong received from the node. Node endpoints are considered verified when a valid pong is received and the time of last pong was called 'bond time'. The time of last ping sent was unused. In this commit, the last ping database entry is repurposed to mean last ping _received_. This entry is now used to track whether the node needs to be pinged back. The other big change is how nodes are added to the table. We used to add nodes in Table.bond, which ran when a remote node pinged us or when we encountered the node in a neighbors reply. The transport now adds to the table directly after the endpoint is verified through ping. To ensure that the Table can't be filled just by pinging the node repeatedly, we retain the isInitDone check. During init, only nodes from neighbors replies are added. * p2p/discover: reduce findnode failure counter on success * p2p/discover: remove unused parameter of loadSeedNodes * p2p/discover: improve ping-back check and comments * p2p/discover: add neighbors reply nodes always, not just during init
2018-07-03 13:24:12 +00:00
func (tab *Table) findnode(n *Node, targetID NodeID, reply chan<- []*Node) {
fails := tab.db.findFails(n.ID)
r, err := tab.net.findnode(n.ID, n.addr(), targetID)
if err != nil || len(r) == 0 {
fails++
tab.db.updateFindFails(n.ID, fails)
log.Trace("Findnode failed", "id", n.ID, "failcount", fails, "err", err)
if fails >= maxFindnodeFailures {
log.Trace("Too many findnode failures, dropping", "id", n.ID, "failcount", fails)
tab.delete(n)
}
} else if fails > 0 {
tab.db.updateFindFails(n.ID, fails-1)
}
// 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 {
tab.add(n)
}
reply <- r
}
func (tab *Table) refresh() <-chan struct{} {
done := make(chan struct{})
select {
case tab.refreshReq <- done:
case <-tab.closed:
close(done)
}
return done
}
// loop schedules refresh, revalidate runs and coordinates shutdown.
func (tab *Table) loop() {
var (
revalidate = time.NewTimer(tab.nextRevalidateTime())
refresh = time.NewTicker(refreshInterval)
copyNodes = time.NewTicker(copyNodesInterval)
revalidateDone = make(chan struct{})
refreshDone = make(chan struct{}) // where doRefresh reports completion
waiting = []chan struct{}{tab.initDone} // holds waiting callers while doRefresh runs
)
defer refresh.Stop()
defer revalidate.Stop()
defer copyNodes.Stop()
// Start initial refresh.
go tab.doRefresh(refreshDone)
loop:
for {
select {
case <-refresh.C:
tab.seedRand()
if refreshDone == nil {
refreshDone = make(chan struct{})
go tab.doRefresh(refreshDone)
}
case req := <-tab.refreshReq:
waiting = append(waiting, req)
if refreshDone == nil {
refreshDone = make(chan struct{})
go tab.doRefresh(refreshDone)
}
case <-refreshDone:
for _, ch := range waiting {
close(ch)
}
waiting, refreshDone = nil, nil
case <-revalidate.C:
go tab.doRevalidate(revalidateDone)
case <-revalidateDone:
revalidate.Reset(tab.nextRevalidateTime())
case <-copyNodes.C:
p2p/discover: move bond logic from table to transport (#17048) * p2p/discover: move bond logic from table to transport This commit moves node endpoint verification (bonding) from the table to the UDP transport implementation. Previously, adding a node to the table entailed pinging the node if needed. With this change, the ping-back logic is embedded in the packet handler at a lower level. It is easy to verify that the basic protocol is unchanged: we still require a valid pong reply from the node before findnode is accepted. The node database tracked the time of last ping sent to the node and time of last valid pong received from the node. Node endpoints are considered verified when a valid pong is received and the time of last pong was called 'bond time'. The time of last ping sent was unused. In this commit, the last ping database entry is repurposed to mean last ping _received_. This entry is now used to track whether the node needs to be pinged back. The other big change is how nodes are added to the table. We used to add nodes in Table.bond, which ran when a remote node pinged us or when we encountered the node in a neighbors reply. The transport now adds to the table directly after the endpoint is verified through ping. To ensure that the Table can't be filled just by pinging the node repeatedly, we retain the isInitDone check. During init, only nodes from neighbors replies are added. * p2p/discover: reduce findnode failure counter on success * p2p/discover: remove unused parameter of loadSeedNodes * p2p/discover: improve ping-back check and comments * p2p/discover: add neighbors reply nodes always, not just during init
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go tab.copyLiveNodes()
case <-tab.closeReq:
break loop
}
}
if tab.net != nil {
tab.net.close()
}
if refreshDone != nil {
<-refreshDone
}
for _, ch := range waiting {
close(ch)
}
tab.db.close()
close(tab.closed)
}
// doRefresh performs a lookup for a random target to keep buckets
// full. seed nodes are inserted if the table is empty (initial
// bootstrap or discarded faulty peers).
func (tab *Table) doRefresh(done chan struct{}) {
defer close(done)
// Load nodes from the database and insert
// them. This should yield a few previously seen nodes that are
// (hopefully) still alive.
p2p/discover: move bond logic from table to transport (#17048) * p2p/discover: move bond logic from table to transport This commit moves node endpoint verification (bonding) from the table to the UDP transport implementation. Previously, adding a node to the table entailed pinging the node if needed. With this change, the ping-back logic is embedded in the packet handler at a lower level. It is easy to verify that the basic protocol is unchanged: we still require a valid pong reply from the node before findnode is accepted. The node database tracked the time of last ping sent to the node and time of last valid pong received from the node. Node endpoints are considered verified when a valid pong is received and the time of last pong was called 'bond time'. The time of last ping sent was unused. In this commit, the last ping database entry is repurposed to mean last ping _received_. This entry is now used to track whether the node needs to be pinged back. The other big change is how nodes are added to the table. We used to add nodes in Table.bond, which ran when a remote node pinged us or when we encountered the node in a neighbors reply. The transport now adds to the table directly after the endpoint is verified through ping. To ensure that the Table can't be filled just by pinging the node repeatedly, we retain the isInitDone check. During init, only nodes from neighbors replies are added. * p2p/discover: reduce findnode failure counter on success * p2p/discover: remove unused parameter of loadSeedNodes * p2p/discover: improve ping-back check and comments * p2p/discover: add neighbors reply nodes always, not just during init
2018-07-03 13:24:12 +00:00
tab.loadSeedNodes()
// Run self lookup to discover new neighbor nodes.
tab.lookup(tab.self.ID, false)
// The Kademlia paper specifies that the bucket refresh should
// perform a lookup in the least recently used bucket. We cannot
// adhere to this because the findnode target is a 512bit value
// (not hash-sized) and it is not easily possible to generate a
// sha3 preimage that falls into a chosen bucket.
// We perform a few lookups with a random target instead.
for i := 0; i < 3; i++ {
var target NodeID
crand.Read(target[:])
tab.lookup(target, false)
}
}
p2p/discover: move bond logic from table to transport (#17048) * p2p/discover: move bond logic from table to transport This commit moves node endpoint verification (bonding) from the table to the UDP transport implementation. Previously, adding a node to the table entailed pinging the node if needed. With this change, the ping-back logic is embedded in the packet handler at a lower level. It is easy to verify that the basic protocol is unchanged: we still require a valid pong reply from the node before findnode is accepted. The node database tracked the time of last ping sent to the node and time of last valid pong received from the node. Node endpoints are considered verified when a valid pong is received and the time of last pong was called 'bond time'. The time of last ping sent was unused. In this commit, the last ping database entry is repurposed to mean last ping _received_. This entry is now used to track whether the node needs to be pinged back. The other big change is how nodes are added to the table. We used to add nodes in Table.bond, which ran when a remote node pinged us or when we encountered the node in a neighbors reply. The transport now adds to the table directly after the endpoint is verified through ping. To ensure that the Table can't be filled just by pinging the node repeatedly, we retain the isInitDone check. During init, only nodes from neighbors replies are added. * p2p/discover: reduce findnode failure counter on success * p2p/discover: remove unused parameter of loadSeedNodes * p2p/discover: improve ping-back check and comments * p2p/discover: add neighbors reply nodes always, not just during init
2018-07-03 13:24:12 +00:00
func (tab *Table) loadSeedNodes() {
seeds := tab.db.querySeeds(seedCount, seedMaxAge)
seeds = append(seeds, tab.nursery...)
for i := range seeds {
seed := seeds[i]
p2p/discover: move bond logic from table to transport (#17048) * p2p/discover: move bond logic from table to transport This commit moves node endpoint verification (bonding) from the table to the UDP transport implementation. Previously, adding a node to the table entailed pinging the node if needed. With this change, the ping-back logic is embedded in the packet handler at a lower level. It is easy to verify that the basic protocol is unchanged: we still require a valid pong reply from the node before findnode is accepted. The node database tracked the time of last ping sent to the node and time of last valid pong received from the node. Node endpoints are considered verified when a valid pong is received and the time of last pong was called 'bond time'. The time of last ping sent was unused. In this commit, the last ping database entry is repurposed to mean last ping _received_. This entry is now used to track whether the node needs to be pinged back. The other big change is how nodes are added to the table. We used to add nodes in Table.bond, which ran when a remote node pinged us or when we encountered the node in a neighbors reply. The transport now adds to the table directly after the endpoint is verified through ping. To ensure that the Table can't be filled just by pinging the node repeatedly, we retain the isInitDone check. During init, only nodes from neighbors replies are added. * p2p/discover: reduce findnode failure counter on success * p2p/discover: remove unused parameter of loadSeedNodes * p2p/discover: improve ping-back check and comments * p2p/discover: add neighbors reply nodes always, not just during init
2018-07-03 13:24:12 +00:00
age := log.Lazy{Fn: func() interface{} { return time.Since(tab.db.lastPongReceived(seed.ID)) }}
log.Debug("Found seed node in database", "id", seed.ID, "addr", seed.addr(), "age", age)
tab.add(seed)
}
}
// doRevalidate checks that the last node in a random bucket is still live
// and replaces or deletes the node if it isn't.
func (tab *Table) doRevalidate(done chan<- struct{}) {
defer func() { done <- struct{}{} }()
last, bi := tab.nodeToRevalidate()
if last == nil {
// No non-empty bucket found.
return
}
// Ping the selected node and wait for a pong.
p2p/discover: move bond logic from table to transport (#17048) * p2p/discover: move bond logic from table to transport This commit moves node endpoint verification (bonding) from the table to the UDP transport implementation. Previously, adding a node to the table entailed pinging the node if needed. With this change, the ping-back logic is embedded in the packet handler at a lower level. It is easy to verify that the basic protocol is unchanged: we still require a valid pong reply from the node before findnode is accepted. The node database tracked the time of last ping sent to the node and time of last valid pong received from the node. Node endpoints are considered verified when a valid pong is received and the time of last pong was called 'bond time'. The time of last ping sent was unused. In this commit, the last ping database entry is repurposed to mean last ping _received_. This entry is now used to track whether the node needs to be pinged back. The other big change is how nodes are added to the table. We used to add nodes in Table.bond, which ran when a remote node pinged us or when we encountered the node in a neighbors reply. The transport now adds to the table directly after the endpoint is verified through ping. To ensure that the Table can't be filled just by pinging the node repeatedly, we retain the isInitDone check. During init, only nodes from neighbors replies are added. * p2p/discover: reduce findnode failure counter on success * p2p/discover: remove unused parameter of loadSeedNodes * p2p/discover: improve ping-back check and comments * p2p/discover: add neighbors reply nodes always, not just during init
2018-07-03 13:24:12 +00:00
err := tab.net.ping(last.ID, last.addr())
tab.mutex.Lock()
defer tab.mutex.Unlock()
b := tab.buckets[bi]
if err == nil {
// The node responded, move it to the front.
log.Trace("Revalidated node", "b", bi, "id", last.ID)
b.bump(last)
return
}
// No reply received, pick a replacement or delete the node if there aren't
// any replacements.
if r := tab.replace(b, last); r != nil {
log.Trace("Replaced dead node", "b", bi, "id", last.ID, "ip", last.IP, "r", r.ID, "rip", r.IP)
} else {
log.Trace("Removed dead node", "b", bi, "id", last.ID, "ip", last.IP)
}
}
// nodeToRevalidate returns the last node in a random, non-empty bucket.
func (tab *Table) nodeToRevalidate() (n *Node, bi int) {
tab.mutex.Lock()
defer tab.mutex.Unlock()
for _, bi = range tab.rand.Perm(len(tab.buckets)) {
b := tab.buckets[bi]
if len(b.entries) > 0 {
last := b.entries[len(b.entries)-1]
return last, bi
}
}
return nil, 0
}
func (tab *Table) nextRevalidateTime() time.Duration {
tab.mutex.Lock()
defer tab.mutex.Unlock()
return time.Duration(tab.rand.Int63n(int64(revalidateInterval)))
}
p2p/discover: move bond logic from table to transport (#17048) * p2p/discover: move bond logic from table to transport This commit moves node endpoint verification (bonding) from the table to the UDP transport implementation. Previously, adding a node to the table entailed pinging the node if needed. With this change, the ping-back logic is embedded in the packet handler at a lower level. It is easy to verify that the basic protocol is unchanged: we still require a valid pong reply from the node before findnode is accepted. The node database tracked the time of last ping sent to the node and time of last valid pong received from the node. Node endpoints are considered verified when a valid pong is received and the time of last pong was called 'bond time'. The time of last ping sent was unused. In this commit, the last ping database entry is repurposed to mean last ping _received_. This entry is now used to track whether the node needs to be pinged back. The other big change is how nodes are added to the table. We used to add nodes in Table.bond, which ran when a remote node pinged us or when we encountered the node in a neighbors reply. The transport now adds to the table directly after the endpoint is verified through ping. To ensure that the Table can't be filled just by pinging the node repeatedly, we retain the isInitDone check. During init, only nodes from neighbors replies are added. * p2p/discover: reduce findnode failure counter on success * p2p/discover: remove unused parameter of loadSeedNodes * p2p/discover: improve ping-back check and comments * p2p/discover: add neighbors reply nodes always, not just during init
2018-07-03 13:24:12 +00:00
// copyLiveNodes adds nodes from the table to the database if they have been in the table
// longer then minTableTime.
p2p/discover: move bond logic from table to transport (#17048) * p2p/discover: move bond logic from table to transport This commit moves node endpoint verification (bonding) from the table to the UDP transport implementation. Previously, adding a node to the table entailed pinging the node if needed. With this change, the ping-back logic is embedded in the packet handler at a lower level. It is easy to verify that the basic protocol is unchanged: we still require a valid pong reply from the node before findnode is accepted. The node database tracked the time of last ping sent to the node and time of last valid pong received from the node. Node endpoints are considered verified when a valid pong is received and the time of last pong was called 'bond time'. The time of last ping sent was unused. In this commit, the last ping database entry is repurposed to mean last ping _received_. This entry is now used to track whether the node needs to be pinged back. The other big change is how nodes are added to the table. We used to add nodes in Table.bond, which ran when a remote node pinged us or when we encountered the node in a neighbors reply. The transport now adds to the table directly after the endpoint is verified through ping. To ensure that the Table can't be filled just by pinging the node repeatedly, we retain the isInitDone check. During init, only nodes from neighbors replies are added. * p2p/discover: reduce findnode failure counter on success * p2p/discover: remove unused parameter of loadSeedNodes * p2p/discover: improve ping-back check and comments * p2p/discover: add neighbors reply nodes always, not just during init
2018-07-03 13:24:12 +00:00
func (tab *Table) copyLiveNodes() {
tab.mutex.Lock()
defer tab.mutex.Unlock()
now := time.Now()
for _, b := range &tab.buckets {
for _, n := range b.entries {
if now.Sub(n.addedAt) >= seedMinTableTime {
tab.db.updateNode(n)
}
}
}
}
// closest returns the n nodes in the table that are closest to the
// given id. The caller must hold tab.mutex.
func (tab *Table) closest(target common.Hash, nresults int) *nodesByDistance {
// This is a very wasteful way to find the closest nodes but
// obviously correct. I believe that tree-based buckets would make
// this easier to implement efficiently.
close := &nodesByDistance{target: target}
for _, b := range &tab.buckets {
for _, n := range b.entries {
close.push(n, nresults)
}
}
return close
}
func (tab *Table) len() (n int) {
for _, b := range &tab.buckets {
n += len(b.entries)
}
return n
}
// bucket returns the bucket for the given node ID hash.
func (tab *Table) bucket(sha common.Hash) *bucket {
d := logdist(tab.self.sha, sha)
if d <= bucketMinDistance {
return tab.buckets[0]
}
return tab.buckets[d-bucketMinDistance-1]
}
p2p/discover: move bond logic from table to transport (#17048) * p2p/discover: move bond logic from table to transport This commit moves node endpoint verification (bonding) from the table to the UDP transport implementation. Previously, adding a node to the table entailed pinging the node if needed. With this change, the ping-back logic is embedded in the packet handler at a lower level. It is easy to verify that the basic protocol is unchanged: we still require a valid pong reply from the node before findnode is accepted. The node database tracked the time of last ping sent to the node and time of last valid pong received from the node. Node endpoints are considered verified when a valid pong is received and the time of last pong was called 'bond time'. The time of last ping sent was unused. In this commit, the last ping database entry is repurposed to mean last ping _received_. This entry is now used to track whether the node needs to be pinged back. The other big change is how nodes are added to the table. We used to add nodes in Table.bond, which ran when a remote node pinged us or when we encountered the node in a neighbors reply. The transport now adds to the table directly after the endpoint is verified through ping. To ensure that the Table can't be filled just by pinging the node repeatedly, we retain the isInitDone check. During init, only nodes from neighbors replies are added. * p2p/discover: reduce findnode failure counter on success * p2p/discover: remove unused parameter of loadSeedNodes * p2p/discover: improve ping-back check and comments * p2p/discover: add neighbors reply nodes always, not just during init
2018-07-03 13:24:12 +00:00
// add attempts to add the given node to its corresponding bucket. If the bucket has space
// available, adding the node succeeds immediately. Otherwise, the node is added if the
// least recently active node in the bucket does not respond to a ping packet.
//
// The caller must not hold tab.mutex.
p2p/discover: move bond logic from table to transport (#17048) * p2p/discover: move bond logic from table to transport This commit moves node endpoint verification (bonding) from the table to the UDP transport implementation. Previously, adding a node to the table entailed pinging the node if needed. With this change, the ping-back logic is embedded in the packet handler at a lower level. It is easy to verify that the basic protocol is unchanged: we still require a valid pong reply from the node before findnode is accepted. The node database tracked the time of last ping sent to the node and time of last valid pong received from the node. Node endpoints are considered verified when a valid pong is received and the time of last pong was called 'bond time'. The time of last ping sent was unused. In this commit, the last ping database entry is repurposed to mean last ping _received_. This entry is now used to track whether the node needs to be pinged back. The other big change is how nodes are added to the table. We used to add nodes in Table.bond, which ran when a remote node pinged us or when we encountered the node in a neighbors reply. The transport now adds to the table directly after the endpoint is verified through ping. To ensure that the Table can't be filled just by pinging the node repeatedly, we retain the isInitDone check. During init, only nodes from neighbors replies are added. * p2p/discover: reduce findnode failure counter on success * p2p/discover: remove unused parameter of loadSeedNodes * p2p/discover: improve ping-back check and comments * p2p/discover: add neighbors reply nodes always, not just during init
2018-07-03 13:24:12 +00:00
func (tab *Table) add(n *Node) {
tab.mutex.Lock()
defer tab.mutex.Unlock()
p2p/discover: move bond logic from table to transport (#17048) * p2p/discover: move bond logic from table to transport This commit moves node endpoint verification (bonding) from the table to the UDP transport implementation. Previously, adding a node to the table entailed pinging the node if needed. With this change, the ping-back logic is embedded in the packet handler at a lower level. It is easy to verify that the basic protocol is unchanged: we still require a valid pong reply from the node before findnode is accepted. The node database tracked the time of last ping sent to the node and time of last valid pong received from the node. Node endpoints are considered verified when a valid pong is received and the time of last pong was called 'bond time'. The time of last ping sent was unused. In this commit, the last ping database entry is repurposed to mean last ping _received_. This entry is now used to track whether the node needs to be pinged back. The other big change is how nodes are added to the table. We used to add nodes in Table.bond, which ran when a remote node pinged us or when we encountered the node in a neighbors reply. The transport now adds to the table directly after the endpoint is verified through ping. To ensure that the Table can't be filled just by pinging the node repeatedly, we retain the isInitDone check. During init, only nodes from neighbors replies are added. * p2p/discover: reduce findnode failure counter on success * p2p/discover: remove unused parameter of loadSeedNodes * p2p/discover: improve ping-back check and comments * p2p/discover: add neighbors reply nodes always, not just during init
2018-07-03 13:24:12 +00:00
b := tab.bucket(n.sha)
if !tab.bumpOrAdd(b, n) {
// Node is not in table. Add it to the replacement list.
p2p/discover: move bond logic from table to transport (#17048) * p2p/discover: move bond logic from table to transport This commit moves node endpoint verification (bonding) from the table to the UDP transport implementation. Previously, adding a node to the table entailed pinging the node if needed. With this change, the ping-back logic is embedded in the packet handler at a lower level. It is easy to verify that the basic protocol is unchanged: we still require a valid pong reply from the node before findnode is accepted. The node database tracked the time of last ping sent to the node and time of last valid pong received from the node. Node endpoints are considered verified when a valid pong is received and the time of last pong was called 'bond time'. The time of last ping sent was unused. In this commit, the last ping database entry is repurposed to mean last ping _received_. This entry is now used to track whether the node needs to be pinged back. The other big change is how nodes are added to the table. We used to add nodes in Table.bond, which ran when a remote node pinged us or when we encountered the node in a neighbors reply. The transport now adds to the table directly after the endpoint is verified through ping. To ensure that the Table can't be filled just by pinging the node repeatedly, we retain the isInitDone check. During init, only nodes from neighbors replies are added. * p2p/discover: reduce findnode failure counter on success * p2p/discover: remove unused parameter of loadSeedNodes * p2p/discover: improve ping-back check and comments * p2p/discover: add neighbors reply nodes always, not just during init
2018-07-03 13:24:12 +00:00
tab.addReplacement(b, n)
}
}
// addThroughPing adds the given node to the table. Compared to plain
// 'add' there is an additional safety measure: if the table is still
// initializing the node is not added. This prevents an attack where the
// table could be filled by just sending ping repeatedly.
//
// The caller must not hold tab.mutex.
func (tab *Table) addThroughPing(n *Node) {
if !tab.isInitDone() {
return
}
p2p/discover: move bond logic from table to transport (#17048) * p2p/discover: move bond logic from table to transport This commit moves node endpoint verification (bonding) from the table to the UDP transport implementation. Previously, adding a node to the table entailed pinging the node if needed. With this change, the ping-back logic is embedded in the packet handler at a lower level. It is easy to verify that the basic protocol is unchanged: we still require a valid pong reply from the node before findnode is accepted. The node database tracked the time of last ping sent to the node and time of last valid pong received from the node. Node endpoints are considered verified when a valid pong is received and the time of last pong was called 'bond time'. The time of last ping sent was unused. In this commit, the last ping database entry is repurposed to mean last ping _received_. This entry is now used to track whether the node needs to be pinged back. The other big change is how nodes are added to the table. We used to add nodes in Table.bond, which ran when a remote node pinged us or when we encountered the node in a neighbors reply. The transport now adds to the table directly after the endpoint is verified through ping. To ensure that the Table can't be filled just by pinging the node repeatedly, we retain the isInitDone check. During init, only nodes from neighbors replies are added. * p2p/discover: reduce findnode failure counter on success * p2p/discover: remove unused parameter of loadSeedNodes * p2p/discover: improve ping-back check and comments * p2p/discover: add neighbors reply nodes always, not just during init
2018-07-03 13:24:12 +00:00
tab.add(n)
}
// stuff adds nodes the table to the end of their corresponding bucket
// if the bucket is not full. The caller must not hold tab.mutex.
func (tab *Table) stuff(nodes []*Node) {
tab.mutex.Lock()
defer tab.mutex.Unlock()
for _, n := range nodes {
2015-04-23 10:11:21 +00:00
if n.ID == tab.self.ID {
continue // don't add self
}
b := tab.bucket(n.sha)
if len(b.entries) < bucketSize {
tab.bumpOrAdd(b, n)
}
}
}
p2p/discover: move bond logic from table to transport (#17048) * p2p/discover: move bond logic from table to transport This commit moves node endpoint verification (bonding) from the table to the UDP transport implementation. Previously, adding a node to the table entailed pinging the node if needed. With this change, the ping-back logic is embedded in the packet handler at a lower level. It is easy to verify that the basic protocol is unchanged: we still require a valid pong reply from the node before findnode is accepted. The node database tracked the time of last ping sent to the node and time of last valid pong received from the node. Node endpoints are considered verified when a valid pong is received and the time of last pong was called 'bond time'. The time of last ping sent was unused. In this commit, the last ping database entry is repurposed to mean last ping _received_. This entry is now used to track whether the node needs to be pinged back. The other big change is how nodes are added to the table. We used to add nodes in Table.bond, which ran when a remote node pinged us or when we encountered the node in a neighbors reply. The transport now adds to the table directly after the endpoint is verified through ping. To ensure that the Table can't be filled just by pinging the node repeatedly, we retain the isInitDone check. During init, only nodes from neighbors replies are added. * p2p/discover: reduce findnode failure counter on success * p2p/discover: remove unused parameter of loadSeedNodes * p2p/discover: improve ping-back check and comments * p2p/discover: add neighbors reply nodes always, not just during init
2018-07-03 13:24:12 +00:00
// delete removes an entry from the node table. It is used to evacuate dead nodes.
func (tab *Table) delete(node *Node) {
tab.mutex.Lock()
defer tab.mutex.Unlock()
tab.deleteInBucket(tab.bucket(node.sha), node)
}
func (tab *Table) addIP(b *bucket, ip net.IP) bool {
if netutil.IsLAN(ip) {
return true
}
if !tab.ips.Add(ip) {
log.Debug("IP exceeds table limit", "ip", ip)
return false
}
if !b.ips.Add(ip) {
log.Debug("IP exceeds bucket limit", "ip", ip)
tab.ips.Remove(ip)
return false
}
return true
}
func (tab *Table) removeIP(b *bucket, ip net.IP) {
if netutil.IsLAN(ip) {
return
}
tab.ips.Remove(ip)
b.ips.Remove(ip)
}
func (tab *Table) addReplacement(b *bucket, n *Node) {
for _, e := range b.replacements {
if e.ID == n.ID {
return // already in list
}
}
if !tab.addIP(b, n.IP) {
return
}
var removed *Node
b.replacements, removed = pushNode(b.replacements, n, maxReplacements)
if removed != nil {
tab.removeIP(b, removed.IP)
}
}
// replace removes n from the replacement list and replaces 'last' with it if it is the
// last entry in the bucket. If 'last' isn't the last entry, it has either been replaced
// with someone else or became active.
func (tab *Table) replace(b *bucket, last *Node) *Node {
2018-02-13 18:59:43 +00:00
if len(b.entries) == 0 || b.entries[len(b.entries)-1].ID != last.ID {
// Entry has moved, don't replace it.
return nil
}
// Still the last entry.
if len(b.replacements) == 0 {
tab.deleteInBucket(b, last)
return nil
}
r := b.replacements[tab.rand.Intn(len(b.replacements))]
b.replacements = deleteNode(b.replacements, r)
b.entries[len(b.entries)-1] = r
tab.removeIP(b, last.IP)
return r
}
// bump moves the given node to the front of the bucket entry list
// if it is contained in that list.
func (b *bucket) bump(n *Node) bool {
for i := range b.entries {
if b.entries[i].ID == n.ID {
// move it to the front
copy(b.entries[1:], b.entries[:i])
b.entries[0] = n
return true
}
}
return false
}
// bumpOrAdd moves n to the front of the bucket entry list or adds it if the list isn't
// full. The return value is true if n is in the bucket.
func (tab *Table) bumpOrAdd(b *bucket, n *Node) bool {
if b.bump(n) {
return true
}
if len(b.entries) >= bucketSize || !tab.addIP(b, n.IP) {
return false
}
b.entries, _ = pushNode(b.entries, n, bucketSize)
b.replacements = deleteNode(b.replacements, n)
n.addedAt = time.Now()
if tab.nodeAddedHook != nil {
tab.nodeAddedHook(n)
}
return true
}
func (tab *Table) deleteInBucket(b *bucket, n *Node) {
b.entries = deleteNode(b.entries, n)
tab.removeIP(b, n.IP)
}
// pushNode adds n to the front of list, keeping at most max items.
func pushNode(list []*Node, n *Node, max int) ([]*Node, *Node) {
if len(list) < max {
list = append(list, nil)
}
removed := list[len(list)-1]
copy(list[1:], list)
list[0] = n
return list, removed
}
// deleteNode removes n from list.
func deleteNode(list []*Node, n *Node) []*Node {
for i := range list {
if list[i].ID == n.ID {
return append(list[:i], list[i+1:]...)
}
}
return list
}
// nodesByDistance is a list of nodes, ordered by
// distance to target.
type nodesByDistance struct {
entries []*Node
target common.Hash
}
// push adds the given node to the list, keeping the total size below maxElems.
func (h *nodesByDistance) push(n *Node, maxElems int) {
ix := sort.Search(len(h.entries), func(i int) bool {
return distcmp(h.target, h.entries[i].sha, n.sha) > 0
})
if len(h.entries) < maxElems {
h.entries = append(h.entries, n)
}
if ix == len(h.entries) {
// farther away than all nodes we already have.
// if there was room for it, the node is now the last element.
} else {
// slide existing entries down to make room
// this will overwrite the entry we just appended.
copy(h.entries[ix+1:], h.entries[ix:])
h.entries[ix] = n
}
}