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p2p/discover: new package implementing the Node Discovery Protocol

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This commit is contained in:
Felix Lange 2015-01-27 14:33:26 +01:00
parent 8c3095faf0
commit 12224c7f59
4 changed files with 1428 additions and 0 deletions
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447
p2p/discover/table.go Normal file
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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 (
"crypto/ecdsa"
"crypto/elliptic"
"encoding/hex"
"fmt"
"io"
"math/rand"
"net"
"sort"
"strings"
"sync"
"time"
"github.com/ethereum/go-ethereum/crypto/secp256k1"
"github.com/ethereum/go-ethereum/rlp"
)
const (
alpha = 3 // Kademlia concurrency factor
bucketSize = 16 // Kademlia bucket size
nBuckets = len(NodeID{})*8 + 1 // Number of buckets
)
type Table struct {
mutex sync.Mutex // protects buckets, their content, and nursery
buckets [nBuckets]*bucket // index of known nodes by distance
nursery []*Node // bootstrap nodes
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(*Node) error
findnode(e *Node, target NodeID) ([]*Node, error)
close()
}
// bucket contains nodes, ordered by their last activity.
type bucket struct {
lastLookup time.Time
entries []*Node
}
// Node represents node metadata that is stored in the table.
type Node struct {
Addr *net.UDPAddr
ID NodeID
active time.Time
}
type rpcNode struct {
IP string
Port uint16
ID NodeID
}
func (n Node) EncodeRLP(w io.Writer) error {
return rlp.Encode(w, rpcNode{IP: n.Addr.IP.String(), Port: uint16(n.Addr.Port), ID: n.ID})
}
func (n *Node) DecodeRLP(s *rlp.Stream) (err error) {
var ext rpcNode
if err = s.Decode(&ext); err == nil {
n.Addr = &net.UDPAddr{IP: net.ParseIP(ext.IP), Port: int(ext.Port)}
n.ID = ext.ID
}
return err
}
func newTable(t transport, ourID NodeID, ourAddr *net.UDPAddr) *Table {
tab := &Table{net: t, self: &Node{ID: ourID, Addr: ourAddr}}
for i := range tab.buckets {
tab.buckets[i] = &bucket{}
}
return tab
}
// Bootstrap sets the bootstrap nodes. These nodes are used to connect
// to the network if the table is empty. Bootstrap will also attempt to
// fill the table by performing random lookup operations on the
// network.
func (tab *Table) Bootstrap(nodes []Node) {
tab.mutex.Lock()
// TODO: maybe filter nodes with bad fields (nil, etc.) to avoid strange crashes
tab.nursery = make([]*Node, 0, len(nodes))
for _, n := range nodes {
cpy := n
tab.nursery = append(tab.nursery, &cpy)
}
tab.mutex.Unlock()
tab.refresh()
}
// 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.
func (tab *Table) Lookup(target NodeID) []*Node {
var (
asked = make(map[NodeID]bool)
seen = make(map[NodeID]bool)
reply = make(chan []*Node, alpha)
pendingQueries = 0
)
// don't query further if we hit the target.
// unlikely to happen often in practice.
asked[target] = true
tab.mutex.Lock()
// update last lookup stamp (for refresh logic)
tab.buckets[logdist(tab.self.ID, target)].lastLookup = time.Now()
// generate initial result set
result := tab.closest(target, bucketSize)
tab.mutex.Unlock()
for {
// ask the 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++
go func() {
result, _ := tab.net.findnode(n, target)
reply <- result
}()
}
}
if pendingQueries == 0 {
// we have asked all closest nodes, stop the search
break
}
// wait for the next reply
for _, n := range <-reply {
cn := n
if !seen[n.ID] {
seen[n.ID] = true
result.push(cn, bucketSize)
}
}
pendingQueries--
}
return result.entries
}
// refresh performs a lookup for a random target to keep buckets full.
func (tab *Table) refresh() {
ld := -1 // logdist of chosen bucket
tab.mutex.Lock()
for i, b := range tab.buckets {
if i > 0 && b.lastLookup.Before(time.Now().Add(-1*time.Hour)) {
ld = i
break
}
}
tab.mutex.Unlock()
result := tab.Lookup(randomID(tab.self.ID, ld))
if len(result) == 0 {
// bootstrap the table with a self lookup
tab.mutex.Lock()
tab.add(tab.nursery)
tab.mutex.Unlock()
tab.Lookup(tab.self.ID)
// TODO: the Kademlia paper says that we're supposed to perform
// random lookups in all buckets further away than our closest neighbor.
}
}
// 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 NodeID, 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
}
// bumpOrAdd updates the activity timestamp for the given node and
// attempts to insert the node into a bucket. The returned Node might
// not be part of the table. The caller must hold tab.mutex.
func (tab *Table) bumpOrAdd(node NodeID, from *net.UDPAddr) (n *Node) {
b := tab.buckets[logdist(tab.self.ID, node)]
if n = b.bump(node); n == nil {
n = &Node{ID: node, Addr: from, active: time.Now()}
if len(b.entries) == bucketSize {
tab.pingReplace(n, b)
} else {
b.entries = append(b.entries, n)
}
}
return n
}
func (tab *Table) pingReplace(n *Node, b *bucket) {
old := b.entries[bucketSize-1]
go func() {
if err := tab.net.ping(old); err == nil {
// it responded, we don't need to replace it.
return
}
// it didn't respond, replace the node if it is still the oldest node.
tab.mutex.Lock()
if len(b.entries) > 0 && b.entries[len(b.entries)-1] == old {
// slide down other entries and put the new one in front.
copy(b.entries[1:], b.entries)
b.entries[0] = n
}
tab.mutex.Unlock()
}()
}
// bump updates the activity timestamp for the given node.
// The caller must hold tab.mutex.
func (tab *Table) bump(node NodeID) {
tab.buckets[logdist(tab.self.ID, node)].bump(node)
}
// add puts the entries into the table if their corresponding
// bucket is not full. The caller must hold tab.mutex.
func (tab *Table) add(entries []*Node) {
outer:
for _, n := range entries {
if n == nil || n.ID == tab.self.ID {
// skip bad entries. The RLP decoder returns nil for empty
// input lists.
continue
}
bucket := tab.buckets[logdist(tab.self.ID, n.ID)]
for i := range bucket.entries {
if bucket.entries[i].ID == n.ID {
// already in bucket
continue outer
}
}
if len(bucket.entries) < bucketSize {
bucket.entries = append(bucket.entries, n)
}
}
}
func (b *bucket) bump(id NodeID) *Node {
for i, n := range b.entries {
if n.ID == id {
n.active = time.Now()
// move it to the front
copy(b.entries[1:], b.entries[:i+1])
b.entries[0] = n
return n
}
}
return nil
}
// nodesByDistance is a list of nodes, ordered by
// distance to target.
type nodesByDistance struct {
entries []*Node
target NodeID
}
// 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].ID, n.ID) > 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
}
}
// NodeID is a unique identifier for each node.
// The node identifier is a marshaled elliptic curve public key.
type NodeID [512 / 8]byte
// NodeID prints as a long hexadecimal number.
func (n NodeID) String() string {
return fmt.Sprintf("%#x", n[:])
}
// The Go syntax representation of a NodeID is a call to HexID.
func (n NodeID) GoString() string {
return fmt.Sprintf("HexID(\"%#x\")", n[:])
}
// HexID converts a hex string to a NodeID.
// The string may be prefixed with 0x.
func HexID(in string) NodeID {
if strings.HasPrefix(in, "0x") {
in = in[2:]
}
var id NodeID
b, err := hex.DecodeString(in)
if err != nil {
panic(err)
} else if len(b) != len(id) {
panic("wrong length")
}
copy(id[:], b)
return id
}
func newNodeID(priv *ecdsa.PrivateKey) (id NodeID) {
pubkey := elliptic.Marshal(priv.Curve, priv.X, priv.Y)
if len(pubkey)-1 != len(id) {
panic(fmt.Errorf("invalid key: need %d bit pubkey, got %d bits", (len(id)+1)*8, len(pubkey)))
}
copy(id[:], pubkey[1:])
return id
}
// recoverNodeID computes the public key used to sign the
// given hash from the signature.
func recoverNodeID(hash, sig []byte) (id NodeID, err error) {
pubkey, err := secp256k1.RecoverPubkey(hash, sig)
if err != nil {
return id, err
}
if len(pubkey)-1 != len(id) {
return id, fmt.Errorf("recovered pubkey has %d bits, want %d bits", len(pubkey)*8, (len(id)+1)*8)
}
for i := range id {
id[i] = pubkey[i+1]
}
return id, nil
}
// distcmp compares the distances a->target and b->target.
// Returns -1 if a is closer to target, 1 if b is closer to target
// and 0 if they are equal.
func distcmp(target, a, b NodeID) int {
for i := range target {
da := a[i] ^ target[i]
db := b[i] ^ target[i]
if da > db {
return 1
} else if da < db {
return -1
}
}
return 0
}
// table of leading zero counts for bytes [0..255]
var lzcount = [256]int{
8, 7, 6, 6, 5, 5, 5, 5,
4, 4, 4, 4, 4, 4, 4, 4,
3, 3, 3, 3, 3, 3, 3, 3,
3, 3, 3, 3, 3, 3, 3, 3,
2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
}
// logdist returns the logarithmic distance between a and b, log2(a ^ b).
func logdist(a, b NodeID) int {
lz := 0
for i := range a {
x := a[i] ^ b[i]
if x == 0 {
lz += 8
} else {
lz += lzcount[x]
break
}
}
return len(a)*8 - lz
}
// randomID returns a random NodeID such that logdist(a, b) == n
func randomID(a NodeID, n int) (b NodeID) {
if n == 0 {
return a
}
// flip bit at position n, fill the rest with random bits
b = a
pos := len(a) - n/8 - 1
bit := byte(0x01) << (byte(n%8) - 1)
if bit == 0 {
pos++
bit = 0x80
}
b[pos] = a[pos]&^bit | ^a[pos]&bit // TODO: randomize end bits
for i := pos + 1; i < len(a); i++ {
b[i] = byte(rand.Intn(255))
}
return b
}

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p2p/discover/table_test.go Normal file
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package discover
import (
"crypto/ecdsa"
"errors"
"fmt"
"math/big"
"math/rand"
"net"
"reflect"
"testing"
"testing/quick"
"time"
"github.com/ethereum/go-ethereum/crypto"
)
var (
quickrand = rand.New(rand.NewSource(time.Now().Unix()))
quickcfg = &quick.Config{MaxCount: 5000, Rand: quickrand}
)
func TestHexID(t *testing.T) {
ref := NodeID{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 128, 106, 217, 182, 31, 165, 174, 1, 67, 7, 235, 220, 150, 66, 83, 173, 205, 159, 44, 10, 57, 42, 161, 26, 188}
id1 := HexID("0x000000000000000000000000000000000000000000000000000000000000000000000000000000806ad9b61fa5ae014307ebdc964253adcd9f2c0a392aa11abc")
id2 := HexID("000000000000000000000000000000000000000000000000000000000000000000000000000000806ad9b61fa5ae014307ebdc964253adcd9f2c0a392aa11abc")
if id1 != ref {
t.Errorf("wrong id1\ngot %v\nwant %v", id1[:], ref[:])
}
if id2 != ref {
t.Errorf("wrong id2\ngot %v\nwant %v", id2[:], ref[:])
}
}
func TestNodeID_recover(t *testing.T) {
prv := newkey()
hash := make([]byte, 32)
sig, err := crypto.Sign(hash, prv)
if err != nil {
t.Fatalf("signing error: %v", err)
}
pub := newNodeID(prv)
recpub, err := recoverNodeID(hash, sig)
if err != nil {
t.Fatalf("recovery error: %v", err)
}
if pub != recpub {
t.Errorf("recovered wrong pubkey:\ngot: %v\nwant: %v", recpub, pub)
}
}
func TestNodeID_distcmp(t *testing.T) {
distcmpBig := func(target, a, b NodeID) int {
tbig := new(big.Int).SetBytes(target[:])
abig := new(big.Int).SetBytes(a[:])
bbig := new(big.Int).SetBytes(b[:])
return new(big.Int).Xor(tbig, abig).Cmp(new(big.Int).Xor(tbig, bbig))
}
if err := quick.CheckEqual(distcmp, distcmpBig, quickcfg); err != nil {
t.Error(err)
}
}
// the random tests is likely to miss the case where they're equal.
func TestNodeID_distcmpEqual(t *testing.T) {
base := NodeID{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}
x := NodeID{15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0}
if distcmp(base, x, x) != 0 {
t.Errorf("distcmp(base, x, x) != 0")
}
}
func TestNodeID_logdist(t *testing.T) {
logdistBig := func(a, b NodeID) int {
abig, bbig := new(big.Int).SetBytes(a[:]), new(big.Int).SetBytes(b[:])
return new(big.Int).Xor(abig, bbig).BitLen()
}
if err := quick.CheckEqual(logdist, logdistBig, quickcfg); err != nil {
t.Error(err)
}
}
// the random tests is likely to miss the case where they're equal.
func TestNodeID_logdistEqual(t *testing.T) {
x := NodeID{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}
if logdist(x, x) != 0 {
t.Errorf("logdist(x, x) != 0")
}
}
func TestNodeID_randomID(t *testing.T) {
// we don't use quick.Check here because its output isn't
// very helpful when the test fails.
for i := 0; i < quickcfg.MaxCount; i++ {
a := gen(NodeID{}, quickrand).(NodeID)
dist := quickrand.Intn(len(NodeID{}) * 8)
result := randomID(a, dist)
actualdist := logdist(result, a)
if dist != actualdist {
t.Log("a: ", a)
t.Log("result:", result)
t.Fatalf("#%d: distance of result is %d, want %d", i, actualdist, dist)
}
}
}
func (NodeID) Generate(rand *rand.Rand, size int) reflect.Value {
var id NodeID
m := rand.Intn(len(id))
for i := len(id) - 1; i > m; i-- {
id[i] = byte(rand.Uint32())
}
return reflect.ValueOf(id)
}
func TestTable_bumpOrAddPingReplace(t *testing.T) {
pingC := make(pingC)
tab := newTable(pingC, NodeID{}, &net.UDPAddr{})
last := fillBucket(tab, 200)
// this bumpOrAdd should not replace the last node
// because the node replies to ping.
new := tab.bumpOrAdd(randomID(tab.self.ID, 200), nil)
pinged := <-pingC
if pinged != last.ID {
t.Fatalf("pinged wrong node: %v\nwant %v", pinged, last.ID)
}
tab.mutex.Lock()
defer tab.mutex.Unlock()
if l := len(tab.buckets[200].entries); l != bucketSize {
t.Errorf("wrong bucket size after bumpOrAdd: got %d, want %d", bucketSize, l)
}
if !contains(tab.buckets[200].entries, last.ID) {
t.Error("last entry was removed")
}
if contains(tab.buckets[200].entries, new.ID) {
t.Error("new entry was added")
}
}
func TestTable_bumpOrAddPingTimeout(t *testing.T) {
tab := newTable(pingC(nil), NodeID{}, &net.UDPAddr{})
last := fillBucket(tab, 200)
// this bumpOrAdd should replace the last node
// because the node does not reply to ping.
new := tab.bumpOrAdd(randomID(tab.self.ID, 200), nil)
// wait for async bucket update. damn. this needs to go away.
time.Sleep(2 * time.Millisecond)
tab.mutex.Lock()
defer tab.mutex.Unlock()
if l := len(tab.buckets[200].entries); l != bucketSize {
t.Errorf("wrong bucket size after bumpOrAdd: got %d, want %d", bucketSize, l)
}
if contains(tab.buckets[200].entries, last.ID) {
t.Error("last entry was not removed")
}
if !contains(tab.buckets[200].entries, new.ID) {
t.Error("new entry was not added")
}
}
func fillBucket(tab *Table, ld int) (last *Node) {
b := tab.buckets[ld]
for len(b.entries) < bucketSize {
b.entries = append(b.entries, &Node{ID: randomID(tab.self.ID, ld)})
}
return b.entries[bucketSize-1]
}
type pingC chan NodeID
func (t pingC) findnode(n *Node, target NodeID) ([]*Node, error) {
panic("findnode called on pingRecorder")
}
func (t pingC) close() {
panic("close called on pingRecorder")
}
func (t pingC) ping(n *Node) error {
if t == nil {
return errTimeout
}
t <- n.ID
return nil
}
func TestTable_bump(t *testing.T) {
tab := newTable(nil, NodeID{}, &net.UDPAddr{})
// add an old entry and two recent ones
oldactive := time.Now().Add(-2 * time.Minute)
old := &Node{ID: randomID(tab.self.ID, 200), active: oldactive}
others := []*Node{
&Node{ID: randomID(tab.self.ID, 200), active: time.Now()},
&Node{ID: randomID(tab.self.ID, 200), active: time.Now()},
}
tab.add(append(others, old))
if tab.buckets[200].entries[0] == old {
t.Fatal("old entry is at front of bucket")
}
// bumping the old entry should move it to the front
tab.bump(old.ID)
if old.active == oldactive {
t.Error("activity timestamp not updated")
}
if tab.buckets[200].entries[0] != old {
t.Errorf("bumped entry did not move to the front of bucket")
}
}
func TestTable_closest(t *testing.T) {
t.Parallel()
test := func(test *closeTest) bool {
// for any node table, Target and N
tab := newTable(nil, test.Self, &net.UDPAddr{})
tab.add(test.All)
// check that doClosest(Target, N) returns nodes
result := tab.closest(test.Target, test.N).entries
if hasDuplicates(result) {
t.Errorf("result contains duplicates")
return false
}
if !sortedByDistanceTo(test.Target, result) {
t.Errorf("result is not sorted by distance to target")
return false
}
// check that the number of results is min(N, tablen)
wantN := test.N
if tlen := tab.len(); tlen < test.N {
wantN = tlen
}
if len(result) != wantN {
t.Errorf("wrong number of nodes: got %d, want %d", len(result), wantN)
return false
} else if len(result) == 0 {
return true // no need to check distance
}
// check that the result nodes have minimum distance to target.
for _, b := range tab.buckets {
for _, n := range b.entries {
if contains(result, n.ID) {
continue // don't run the check below for nodes in result
}
farthestResult := result[len(result)-1].ID
if distcmp(test.Target, n.ID, farthestResult) < 0 {
t.Errorf("table contains node that is closer to target but it's not in result")
t.Logf(" Target: %v", test.Target)
t.Logf(" Farthest Result: %v", farthestResult)
t.Logf(" ID: %v", n.ID)
return false
}
}
}
return true
}
if err := quick.Check(test, quickcfg); err != nil {
t.Error(err)
}
}
type closeTest struct {
Self NodeID
Target NodeID
All []*Node
N int
}
func (*closeTest) Generate(rand *rand.Rand, size int) reflect.Value {
t := &closeTest{
Self: gen(NodeID{}, rand).(NodeID),
Target: gen(NodeID{}, rand).(NodeID),
N: rand.Intn(bucketSize),
}
for _, id := range gen([]NodeID{}, rand).([]NodeID) {
t.All = append(t.All, &Node{ID: id})
}
return reflect.ValueOf(t)
}
func TestTable_Lookup(t *testing.T) {
self := gen(NodeID{}, quickrand).(NodeID)
target := randomID(self, 200)
transport := findnodeOracle{t, target}
tab := newTable(transport, self, &net.UDPAddr{})
// lookup on empty table returns no nodes
if results := tab.Lookup(target); len(results) > 0 {
t.Fatalf("lookup on empty table returned %d results: %#v", len(results), results)
}
// seed table with initial node (otherwise lookup will terminate immediately)
tab.bumpOrAdd(randomID(target, 200), &net.UDPAddr{Port: 200})
results := tab.Lookup(target)
t.Logf("results:")
for _, e := range results {
t.Logf(" ld=%d, %v", logdist(target, e.ID), e.ID)
}
if len(results) != bucketSize {
t.Errorf("wrong number of results: got %d, want %d", len(results), bucketSize)
}
if hasDuplicates(results) {
t.Errorf("result set contains duplicate entries")
}
if !sortedByDistanceTo(target, results) {
t.Errorf("result set not sorted by distance to target")
}
if !contains(results, target) {
t.Errorf("result set does not contain target")
}
}
// findnode on this transport always returns at least one node
// that is one bucket closer to the target.
type findnodeOracle struct {
t *testing.T
target NodeID
}
func (t findnodeOracle) findnode(n *Node, target NodeID) ([]*Node, error) {
t.t.Logf("findnode query at dist %d", n.Addr.Port)
// current log distance is encoded in port number
var result []*Node
switch port := n.Addr.Port; port {
case 0:
panic("query to node at distance 0")
case 1:
result = append(result, &Node{ID: t.target, Addr: &net.UDPAddr{Port: 0}})
default:
// TODO: add more randomness to distances
port--
for i := 0; i < bucketSize; i++ {
result = append(result, &Node{ID: randomID(t.target, port), Addr: &net.UDPAddr{Port: port}})
}
}
return result, nil
}
func (t findnodeOracle) close() {}
func (t findnodeOracle) ping(n *Node) error {
return errors.New("ping is not supported by this transport")
}
func hasDuplicates(slice []*Node) bool {
seen := make(map[NodeID]bool)
for _, e := range slice {
if seen[e.ID] {
return true
}
seen[e.ID] = true
}
return false
}
func sortedByDistanceTo(distbase NodeID, slice []*Node) bool {
var last NodeID
for i, e := range slice {
if i > 0 && distcmp(distbase, e.ID, last) < 0 {
return false
}
last = e.ID
}
return true
}
func contains(ns []*Node, id NodeID) bool {
for _, n := range ns {
if n.ID == id {
return true
}
}
return false
}
// gen wraps quick.Value so it's easier to use.
// it generates a random value of the given value's type.
func gen(typ interface{}, rand *rand.Rand) interface{} {
v, ok := quick.Value(reflect.TypeOf(typ), rand)
if !ok {
panic(fmt.Sprintf("couldn't generate random value of type %T", typ))
}
return v.Interface()
}
func newkey() *ecdsa.PrivateKey {
key, err := crypto.GenerateKey()
if err != nil {
panic("couldn't generate key: " + err.Error())
}
return key
}

422
p2p/discover/udp.go Normal file
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package discover
import (
"bytes"
"crypto/ecdsa"
"errors"
"fmt"
"net"
"time"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/logger"
"github.com/ethereum/go-ethereum/rlp"
)
var log = logger.NewLogger("P2P Discovery")
// Errors
var (
errPacketTooSmall = errors.New("too small")
errBadHash = errors.New("bad hash")
errExpired = errors.New("expired")
errTimeout = errors.New("RPC timeout")
errClosed = errors.New("socket closed")
)
// Timeouts
const (
respTimeout = 300 * time.Millisecond
sendTimeout = 300 * time.Millisecond
expiration = 3 * time.Second
refreshInterval = 1 * time.Hour
)
// RPC packet types
const (
pingPacket = iota + 1 // zero is 'reserved'
pongPacket
findnodePacket
neighborsPacket
)
// RPC request structures
type (
ping struct {
IP string // our IP
Port uint16 // our port
Expiration uint64
}
// reply to Ping
pong struct {
ReplyTok []byte
Expiration uint64
}
findnode struct {
// Id to look up. The responding node will send back nodes
// closest to the target.
Target NodeID
Expiration uint64
}
// reply to findnode
neighbors struct {
Nodes []*Node
Expiration uint64
}
)
// udp implements the RPC protocol.
type udp struct {
conn *net.UDPConn
priv *ecdsa.PrivateKey
addpending chan *pending
replies chan reply
closing chan struct{}
*Table
}
// pending represents a pending reply.
//
// some implementations of the protocol wish to send more than one
// reply packet to findnode. in general, any neighbors packet cannot
// be matched up with a specific findnode packet.
//
// our implementation handles this by storing a callback function for
// each pending reply. incoming packets from a node are dispatched
// to all the callback functions for that node.
type pending struct {
// these fields must match in the reply.
from NodeID
ptype byte
// time when the request must complete
deadline time.Time
// callback is called when a matching reply arrives. if it returns
// true, the callback is removed from the pending reply queue.
// if it returns false, the reply is considered incomplete and
// the callback will be invoked again for the next matching reply.
callback func(resp interface{}) (done bool)
// errc receives nil when the callback indicates completion or an
// error if no further reply is received within the timeout.
errc chan<- error
}
type reply struct {
from NodeID
ptype byte
data interface{}
}
// ListenUDP returns a new table that listens for UDP packets on laddr.
func ListenUDP(priv *ecdsa.PrivateKey, laddr string) (*Table, error) {
net, realaddr, err := listen(priv, laddr)
if err != nil {
return nil, err
}
net.Table = newTable(net, newNodeID(priv), realaddr)
log.DebugDetailf("Listening on %v, my ID %x\n", realaddr, net.self.ID[:])
return net.Table, nil
}
func listen(priv *ecdsa.PrivateKey, laddr string) (*udp, *net.UDPAddr, error) {
addr, err := net.ResolveUDPAddr("udp", laddr)
if err != nil {
return nil, nil, err
}
conn, err := net.ListenUDP("udp", addr)
if err != nil {
return nil, nil, err
}
realaddr := conn.LocalAddr().(*net.UDPAddr)
udp := &udp{
conn: conn,
priv: priv,
closing: make(chan struct{}),
addpending: make(chan *pending),
replies: make(chan reply),
}
go udp.loop()
go udp.readLoop()
return udp, realaddr, nil
}
func (t *udp) close() {
close(t.closing)
t.conn.Close()
// TODO: wait for the loops to end.
}
// ping sends a ping message to the given node and waits for a reply.
func (t *udp) ping(e *Node) error {
// TODO: maybe check for ReplyTo field in callback to measure RTT
errc := t.pending(e.ID, pongPacket, func(interface{}) bool { return true })
t.send(e, pingPacket, ping{
IP: t.self.Addr.String(),
Port: uint16(t.self.Addr.Port),
Expiration: uint64(time.Now().Add(expiration).Unix()),
})
return <-errc
}
// findnode sends a findnode request to the given node and waits until
// the node has sent up to k neighbors.
func (t *udp) findnode(to *Node, target NodeID) ([]*Node, error) {
nodes := make([]*Node, 0, bucketSize)
nreceived := 0
errc := t.pending(to.ID, neighborsPacket, func(r interface{}) bool {
reply := r.(*neighbors)
for i := 0; i < len(reply.Nodes); i++ {
nreceived++
n := reply.Nodes[i]
if validAddr(n.Addr) && n.ID != t.self.ID {
nodes = append(nodes, n)
}
}
return nreceived == bucketSize
})
t.send(to, findnodePacket, findnode{
Target: target,
Expiration: uint64(time.Now().Add(expiration).Unix()),
})
err := <-errc
return nodes, err
}
func validAddr(a *net.UDPAddr) bool {
return !a.IP.IsMulticast() && !a.IP.IsUnspecified() && a.Port != 0
}
// pending adds a reply callback to the pending reply queue.
// see the documentation of type pending for a detailed explanation.
func (t *udp) pending(id NodeID, ptype byte, callback func(interface{}) bool) <-chan error {
ch := make(chan error, 1)
p := &pending{from: id, ptype: ptype, callback: callback, errc: ch}
select {
case t.addpending <- p:
// loop will handle it
case <-t.closing:
ch <- errClosed
}
return ch
}
// loop runs in its own goroutin. it keeps track of
// the refresh timer and the pending reply queue.
func (t *udp) loop() {
var (
pending []*pending
nextDeadline time.Time
timeout = time.NewTimer(0)
refresh = time.NewTicker(refreshInterval)
)
<-timeout.C // ignore first timeout
defer refresh.Stop()
defer timeout.Stop()
rearmTimeout := func() {
if len(pending) == 0 || nextDeadline == pending[0].deadline {
return
}
nextDeadline = pending[0].deadline
timeout.Reset(nextDeadline.Sub(time.Now()))
}
for {
select {
case <-refresh.C:
go t.refresh()
case <-t.closing:
for _, p := range pending {
p.errc <- errClosed
}
return
case p := <-t.addpending:
p.deadline = time.Now().Add(respTimeout)
pending = append(pending, p)
rearmTimeout()
case reply := <-t.replies:
// run matching callbacks, remove if they return false.
for i, p := range pending {
if reply.from == p.from && reply.ptype == p.ptype && p.callback(reply.data) {
p.errc <- nil
copy(pending[i:], pending[i+1:])
pending = pending[:len(pending)-1]
i--
}
}
rearmTimeout()
case now := <-timeout.C:
// notify and remove callbacks whose deadline is in the past.
i := 0
for ; i < len(pending) && now.After(pending[i].deadline); i++ {
pending[i].errc <- errTimeout
}
if i > 0 {
copy(pending, pending[i:])
pending = pending[:len(pending)-i]
}
rearmTimeout()
}
}
}
const (
macSize = 256 / 8
sigSize = 520 / 8
headSize = macSize + sigSize // space of packet frame data
)
var headSpace = make([]byte, headSize)
func (t *udp) send(to *Node, ptype byte, req interface{}) error {
b := new(bytes.Buffer)
b.Write(headSpace)
b.WriteByte(ptype)
if err := rlp.Encode(b, req); err != nil {
log.Errorln("error encoding packet:", err)
return err
}
packet := b.Bytes()
sig, err := crypto.Sign(crypto.Sha3(packet[headSize:]), t.priv)
if err != nil {
log.Errorln("could not sign packet:", err)
return err
}
copy(packet[macSize:], sig)
// add the hash to the front. Note: this doesn't protect the
// packet in any way. Our public key will be part of this hash in
// the future.
copy(packet, crypto.Sha3(packet[macSize:]))
log.DebugDetailf(">>> %v %T %v\n", to.Addr, req, req)
if _, err = t.conn.WriteToUDP(packet, to.Addr); err != nil {
log.DebugDetailln("UDP send failed:", err)
}
return err
}
// readLoop runs in its own goroutine. it handles incoming UDP packets.
func (t *udp) readLoop() {
defer t.conn.Close()
buf := make([]byte, 4096) // TODO: good buffer size
for {
nbytes, from, err := t.conn.ReadFromUDP(buf)
if err != nil {
return
}
if err := t.packetIn(from, buf[:nbytes]); err != nil {
log.Debugf("Bad packet from %v: %v\n", from, err)
}
}
}
func (t *udp) packetIn(from *net.UDPAddr, buf []byte) error {
if len(buf) < headSize+1 {
return errPacketTooSmall
}
hash, sig, sigdata := buf[:macSize], buf[macSize:headSize], buf[headSize:]
shouldhash := crypto.Sha3(buf[macSize:])
if !bytes.Equal(hash, shouldhash) {
return errBadHash
}
fromID, err := recoverNodeID(crypto.Sha3(buf[headSize:]), sig)
if err != nil {
return err
}
var req interface {
handle(t *udp, from *net.UDPAddr, fromID NodeID, mac []byte) error
}
switch ptype := sigdata[0]; ptype {
case pingPacket:
req = new(ping)
case pongPacket:
req = new(pong)
case findnodePacket:
req = new(findnode)
case neighborsPacket:
req = new(neighbors)
default:
return fmt.Errorf("unknown type: %d", ptype)
}
if err := rlp.Decode(bytes.NewReader(sigdata[1:]), req); err != nil {
return err
}
log.DebugDetailf("<<< %v %T %v\n", from, req, req)
return req.handle(t, from, fromID, hash)
}
func (req *ping) handle(t *udp, from *net.UDPAddr, fromID NodeID, mac []byte) error {
if expired(req.Expiration) {
return errExpired
}
t.mutex.Lock()
// Note: we're ignoring the provided IP/Port right now.
e := t.bumpOrAdd(fromID, from)
t.mutex.Unlock()
t.send(e, pongPacket, pong{
ReplyTok: mac,
Expiration: uint64(time.Now().Add(expiration).Unix()),
})
return nil
}
func (req *pong) handle(t *udp, from *net.UDPAddr, fromID NodeID, mac []byte) error {
if expired(req.Expiration) {
return errExpired
}
t.mutex.Lock()
t.bump(fromID)
t.mutex.Unlock()
t.replies <- reply{fromID, pongPacket, req}
return nil
}
func (req *findnode) handle(t *udp, from *net.UDPAddr, fromID NodeID, mac []byte) error {
if expired(req.Expiration) {
return errExpired
}
t.mutex.Lock()
e := t.bumpOrAdd(fromID, from)
closest := t.closest(req.Target, bucketSize).entries
t.mutex.Unlock()
t.send(e, neighborsPacket, neighbors{
Nodes: closest,
Expiration: uint64(time.Now().Add(expiration).Unix()),
})
return nil
}
func (req *neighbors) handle(t *udp, from *net.UDPAddr, fromID NodeID, mac []byte) error {
if expired(req.Expiration) {
return errExpired
}
t.mutex.Lock()
t.bump(fromID)
t.add(req.Nodes)
t.mutex.Unlock()
t.replies <- reply{fromID, neighborsPacket, req}
return nil
}
func expired(ts uint64) bool {
return time.Unix(int64(ts), 0).Before(time.Now())
}

156
p2p/discover/udp_test.go Normal file
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package discover
import (
logpkg "log"
"net"
"os"
"testing"
"time"
"github.com/ethereum/go-ethereum/logger"
)
func init() {
logger.AddLogSystem(logger.NewStdLogSystem(os.Stdout, logpkg.LstdFlags, logger.DebugLevel))
}
func TestUDP_ping(t *testing.T) {
t.Parallel()
n1, _ := ListenUDP(newkey(), "127.0.0.1:0")
n2, _ := ListenUDP(newkey(), "127.0.0.1:0")
defer n1.net.close()
defer n2.net.close()
if err := n1.net.ping(n2.self); err != nil {
t.Fatalf("ping error: %v", err)
}
if find(n2, n1.self.ID) == nil {
t.Errorf("node 2 does not contain id of node 1")
}
if e := find(n1, n2.self.ID); e != nil {
t.Errorf("node 1 does contains id of node 2: %v", e)
}
}
func find(tab *Table, id NodeID) *Node {
for _, b := range tab.buckets {
for _, e := range b.entries {
if e.ID == id {
return e
}
}
}
return nil
}
func TestUDP_findnode(t *testing.T) {
t.Parallel()
n1, _ := ListenUDP(newkey(), "127.0.0.1:0")
n2, _ := ListenUDP(newkey(), "127.0.0.1:0")
defer n1.net.close()
defer n2.net.close()
entry := &Node{ID: NodeID{1}, Addr: &net.UDPAddr{IP: net.IP{1, 2, 3, 4}, Port: 15}}
n2.add([]*Node{entry})
target := randomID(n1.self.ID, 100)
result, _ := n1.net.findnode(n2.self, target)
if len(result) != 1 {
t.Fatalf("wrong number of results: got %d, want 1", len(result))
}
if result[0].ID != entry.ID {
t.Errorf("wrong result: got %v, want %v", result[0], entry)
}
}
func TestUDP_replytimeout(t *testing.T) {
t.Parallel()
// reserve a port so we don't talk to an existing service by accident
addr, _ := net.ResolveUDPAddr("udp", "127.0.0.1:0")
fd, err := net.ListenUDP("udp", addr)
if err != nil {
t.Fatal(err)
}
defer fd.Close()
n1, _ := ListenUDP(newkey(), "127.0.0.1:0")
defer n1.net.close()
n2 := n1.bumpOrAdd(randomID(n1.self.ID, 10), fd.LocalAddr().(*net.UDPAddr))
if err := n1.net.ping(n2); err != errTimeout {
t.Error("expected timeout error, got", err)
}
if result, err := n1.net.findnode(n2, n1.self.ID); err != errTimeout {
t.Error("expected timeout error, got", err)
} else if len(result) > 0 {
t.Error("expected empty result, got", result)
}
}
func TestUDP_findnodeMultiReply(t *testing.T) {
t.Parallel()
n1, _ := ListenUDP(newkey(), "127.0.0.1:0")
n2, _ := ListenUDP(newkey(), "127.0.0.1:0")
udp2 := n2.net.(*udp)
defer n1.net.close()
defer n2.net.close()
nodes := make([]*Node, bucketSize)
for i := range nodes {
nodes[i] = &Node{
Addr: &net.UDPAddr{IP: net.IP{1, 2, 3, 4}, Port: i + 1},
ID: randomID(n2.self.ID, i+1),
}
}
// ask N2 for neighbors. it will send an empty reply back.
// the request will wait for up to bucketSize replies.
resultC := make(chan []*Node)
go func() {
ns, err := n1.net.findnode(n2.self, n1.self.ID)
if err != nil {
t.Error("findnode error:", err)
}
resultC <- ns
}()
// send a few more neighbors packets to N1.
// it should collect those.
for end := 0; end < len(nodes); {
off := end
if end = end + 5; end > len(nodes) {
end = len(nodes)
}
udp2.send(n1.self, neighborsPacket, neighbors{
Nodes: nodes[off:end],
Expiration: uint64(time.Now().Add(10 * time.Second).Unix()),
})
}
// check that they are all returned. we cannot just check for
// equality because they might not be returned in the order they
// were sent.
result := <-resultC
if hasDuplicates(result) {
t.Error("result slice contains duplicates")
}
if len(result) != len(nodes) {
t.Errorf("wrong number of nodes returned: got %d, want %d", len(result), len(nodes))
}
matched := make(map[NodeID]bool)
for _, n := range result {
for _, expn := range nodes {
if n.ID == expn.ID { // && bytes.Equal(n.Addr.IP, expn.Addr.IP) && n.Addr.Port == expn.Addr.Port {
matched[n.ID] = true
}
}
}
if len(matched) != len(nodes) {
t.Errorf("wrong number of matching nodes: got %d, want %d", len(matched), len(nodes))
}
}