Official Go implementation of the Ethereum protocol
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go-ethereum/p2p/discover/v5_udp.go

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// Copyright 2020 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 (
"bytes"
"context"
"crypto/ecdsa"
crand "crypto/rand"
"errors"
"fmt"
"io"
"net"
"net/netip"
"slices"
"sync"
"time"
"github.com/ethereum/go-ethereum/common/mclock"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/p2p/discover/v5wire"
"github.com/ethereum/go-ethereum/p2p/enode"
"github.com/ethereum/go-ethereum/p2p/enr"
"github.com/ethereum/go-ethereum/p2p/netutil"
)
const (
lookupRequestLimit = 3 // max requests against a single node during lookup
findnodeResultLimit = 16 // applies in FINDNODE handler
totalNodesResponseLimit = 5 // applies in waitForNodes
respTimeoutV5 = 700 * time.Millisecond
)
// codecV5 is implemented by v5wire.Codec (and testCodec).
//
// The UDPv5 transport is split into two objects: the codec object deals with
// encoding/decoding and with the handshake; the UDPv5 object handles higher-level concerns.
type codecV5 interface {
// Encode encodes a packet.
Encode(enode.ID, string, v5wire.Packet, *v5wire.Whoareyou) ([]byte, v5wire.Nonce, error)
// Decode decodes a packet. It returns a *v5wire.Unknown packet if decryption fails.
// The *enode.Node return value is non-nil when the input contains a handshake response.
Decode([]byte, string) (enode.ID, *enode.Node, v5wire.Packet, error)
}
// UDPv5 is the implementation of protocol version 5.
type UDPv5 struct {
// static fields
conn UDPConn
tab *Table
netrestrict *netutil.Netlist
priv *ecdsa.PrivateKey
localNode *enode.LocalNode
db *enode.DB
log log.Logger
clock mclock.Clock
validSchemes enr.IdentityScheme
// misc buffers used during message handling
logcontext []interface{}
// talkreq handler registry
talk *talkSystem
// channels into dispatch
packetInCh chan ReadPacket
readNextCh chan struct{}
callCh chan *callV5
callDoneCh chan *callV5
respTimeoutCh chan *callTimeout
sendCh chan sendRequest
unhandled chan<- ReadPacket
// state of dispatch
codec codecV5
activeCallByNode map[enode.ID]*callV5
activeCallByAuth map[v5wire.Nonce]*callV5
callQueue map[enode.ID][]*callV5
// shutdown stuff
closeOnce sync.Once
closeCtx context.Context
cancelCloseCtx context.CancelFunc
wg sync.WaitGroup
}
type sendRequest struct {
destID enode.ID
destAddr netip.AddrPort
msg v5wire.Packet
}
// callV5 represents a remote procedure call against another node.
type callV5 struct {
id enode.ID
addr netip.AddrPort
node *enode.Node // This is required to perform handshakes.
packet v5wire.Packet
responseType byte // expected packet type of response
reqid []byte
ch chan v5wire.Packet // responses sent here
err chan error // errors sent here
// Valid for active calls only:
nonce v5wire.Nonce // nonce of request packet
handshakeCount int // # times we attempted handshake for this call
challenge *v5wire.Whoareyou // last sent handshake challenge
timeout mclock.Timer
}
// callTimeout is the response timeout event of a call.
type callTimeout struct {
c *callV5
timer mclock.Timer
}
// ListenV5 listens on the given connection.
func ListenV5(conn UDPConn, ln *enode.LocalNode, cfg Config) (*UDPv5, error) {
t, err := newUDPv5(conn, ln, cfg)
if err != nil {
return nil, err
}
go t.tab.loop()
t.wg.Add(2)
go t.readLoop()
go t.dispatch()
return t, nil
}
// newUDPv5 creates a UDPv5 transport, but doesn't start any goroutines.
func newUDPv5(conn UDPConn, ln *enode.LocalNode, cfg Config) (*UDPv5, error) {
closeCtx, cancelCloseCtx := context.WithCancel(context.Background())
cfg = cfg.withDefaults()
t := &UDPv5{
// static fields
conn: newMeteredConn(conn),
localNode: ln,
db: ln.Database(),
netrestrict: cfg.NetRestrict,
priv: cfg.PrivateKey,
log: cfg.Log,
validSchemes: cfg.ValidSchemes,
clock: cfg.Clock,
// channels into dispatch
packetInCh: make(chan ReadPacket, 1),
readNextCh: make(chan struct{}, 1),
callCh: make(chan *callV5),
callDoneCh: make(chan *callV5),
sendCh: make(chan sendRequest),
respTimeoutCh: make(chan *callTimeout),
unhandled: cfg.Unhandled,
// state of dispatch
codec: v5wire.NewCodec(ln, cfg.PrivateKey, cfg.Clock, cfg.V5ProtocolID),
activeCallByNode: make(map[enode.ID]*callV5),
activeCallByAuth: make(map[v5wire.Nonce]*callV5),
callQueue: make(map[enode.ID][]*callV5),
// shutdown
closeCtx: closeCtx,
cancelCloseCtx: cancelCloseCtx,
}
t.talk = newTalkSystem(t)
tab, err := newTable(t, t.db, cfg)
if err != nil {
return nil, err
}
t.tab = tab
return t, nil
}
// Self returns the local node record.
func (t *UDPv5) Self() *enode.Node {
return t.localNode.Node()
}
// Close shuts down packet processing.
func (t *UDPv5) Close() {
t.closeOnce.Do(func() {
t.cancelCloseCtx()
t.conn.Close()
t.talk.wait()
t.wg.Wait()
t.tab.close()
})
}
// Ping sends a ping message to the given node.
func (t *UDPv5) Ping(n *enode.Node) error {
_, err := t.ping(n)
return err
}
// Resolve searches for a specific node with the given ID and tries to get the most recent
// version of the node record for it. It returns n if the node could not be resolved.
func (t *UDPv5) Resolve(n *enode.Node) *enode.Node {
if intable := t.tab.getNode(n.ID()); intable != nil && intable.Seq() > n.Seq() {
n = intable
}
// Try asking directly. This works if the node is still responding on the endpoint we have.
if resp, err := t.RequestENR(n); err == nil {
return resp
}
// Otherwise do a network lookup.
result := t.Lookup(n.ID())
for _, rn := range result {
if rn.ID() == n.ID() && rn.Seq() > n.Seq() {
return rn
}
}
return n
}
// AllNodes returns all the nodes stored in the local table.
func (t *UDPv5) AllNodes() []*enode.Node {
t.tab.mutex.Lock()
defer t.tab.mutex.Unlock()
nodes := make([]*enode.Node, 0)
for _, b := range &t.tab.buckets {
for _, n := range b.entries {
nodes = append(nodes, n.Node)
}
}
return nodes
}
// LocalNode returns the current local node running the
// protocol.
func (t *UDPv5) LocalNode() *enode.LocalNode {
return t.localNode
}
// RegisterTalkHandler adds a handler for 'talk requests'. The handler function is called
// whenever a request for the given protocol is received and should return the response
// data or nil.
func (t *UDPv5) RegisterTalkHandler(protocol string, handler TalkRequestHandler) {
t.talk.register(protocol, handler)
}
// TalkRequest sends a talk request to a node and waits for a response.
func (t *UDPv5) TalkRequest(n *enode.Node, protocol string, request []byte) ([]byte, error) {
req := &v5wire.TalkRequest{Protocol: protocol, Message: request}
resp := t.callToNode(n, v5wire.TalkResponseMsg, req)
defer t.callDone(resp)
select {
case respMsg := <-resp.ch:
return respMsg.(*v5wire.TalkResponse).Message, nil
case err := <-resp.err:
return nil, err
}
}
// TalkRequestToID sends a talk request to a node and waits for a response.
func (t *UDPv5) TalkRequestToID(id enode.ID, addr netip.AddrPort, protocol string, request []byte) ([]byte, error) {
req := &v5wire.TalkRequest{Protocol: protocol, Message: request}
resp := t.callToID(id, addr, v5wire.TalkResponseMsg, req)
defer t.callDone(resp)
select {
case respMsg := <-resp.ch:
return respMsg.(*v5wire.TalkResponse).Message, nil
case err := <-resp.err:
return nil, err
}
}
// RandomNodes returns an iterator that finds random nodes in the DHT.
func (t *UDPv5) RandomNodes() enode.Iterator {
if t.tab.len() == 0 {
// All nodes were dropped, refresh. The very first query will hit this
// case and run the bootstrapping logic.
<-t.tab.refresh()
}
return newLookupIterator(t.closeCtx, t.newRandomLookup)
}
// Lookup performs a recursive lookup for the given target.
// It returns the closest nodes to target.
func (t *UDPv5) Lookup(target enode.ID) []*enode.Node {
return t.newLookup(t.closeCtx, target).run()
}
// lookupRandom looks up a random target.
// This is needed to satisfy the transport interface.
func (t *UDPv5) lookupRandom() []*enode.Node {
return t.newRandomLookup(t.closeCtx).run()
}
// lookupSelf looks up our own node ID.
// This is needed to satisfy the transport interface.
func (t *UDPv5) lookupSelf() []*enode.Node {
return t.newLookup(t.closeCtx, t.Self().ID()).run()
}
func (t *UDPv5) newRandomLookup(ctx context.Context) *lookup {
var target enode.ID
crand.Read(target[:])
return t.newLookup(ctx, target)
}
func (t *UDPv5) newLookup(ctx context.Context, target enode.ID) *lookup {
return newLookup(ctx, t.tab, target, func(n *enode.Node) ([]*enode.Node, error) {
return t.lookupWorker(n, target)
})
}
// lookupWorker performs FINDNODE calls against a single node during lookup.
func (t *UDPv5) lookupWorker(destNode *enode.Node, target enode.ID) ([]*enode.Node, error) {
var (
dists = lookupDistances(target, destNode.ID())
nodes = nodesByDistance{target: target}
err error
)
var r []*enode.Node
r, err = t.findnode(destNode, dists)
if errors.Is(err, errClosed) {
return nil, err
}
for _, n := range r {
if n.ID() != t.Self().ID() {
nodes.push(n, findnodeResultLimit)
}
}
return nodes.entries, err
}
// lookupDistances computes the distance parameter for FINDNODE calls to dest.
// It chooses distances adjacent to logdist(target, dest), e.g. for a target
// with logdist(target, dest) = 255 the result is [255, 256, 254].
func lookupDistances(target, dest enode.ID) (dists []uint) {
td := enode.LogDist(target, dest)
dists = append(dists, uint(td))
for i := 1; len(dists) < lookupRequestLimit; i++ {
if td+i <= 256 {
dists = append(dists, uint(td+i))
}
if td-i > 0 {
dists = append(dists, uint(td-i))
}
}
return dists
}
// ping calls PING on a node and waits for a PONG response.
func (t *UDPv5) ping(n *enode.Node) (uint64, error) {
req := &v5wire.Ping{ENRSeq: t.localNode.Node().Seq()}
resp := t.callToNode(n, v5wire.PongMsg, req)
defer t.callDone(resp)
select {
case pong := <-resp.ch:
return pong.(*v5wire.Pong).ENRSeq, nil
case err := <-resp.err:
return 0, err
}
}
// RequestENR requests n's record.
func (t *UDPv5) RequestENR(n *enode.Node) (*enode.Node, error) {
nodes, err := t.findnode(n, []uint{0})
if err != nil {
return nil, err
}
if len(nodes) != 1 {
return nil, fmt.Errorf("%d nodes in response for distance zero", len(nodes))
}
return nodes[0], nil
}
// findnode calls FINDNODE on a node and waits for responses.
func (t *UDPv5) findnode(n *enode.Node, distances []uint) ([]*enode.Node, error) {
resp := t.callToNode(n, v5wire.NodesMsg, &v5wire.Findnode{Distances: distances})
return t.waitForNodes(resp, distances)
}
// waitForNodes waits for NODES responses to the given call.
func (t *UDPv5) waitForNodes(c *callV5, distances []uint) ([]*enode.Node, error) {
defer t.callDone(c)
var (
nodes []*enode.Node
seen = make(map[enode.ID]struct{})
received, total = 0, -1
)
for {
select {
case responseP := <-c.ch:
response := responseP.(*v5wire.Nodes)
for _, record := range response.Nodes {
node, err := t.verifyResponseNode(c, record, distances, seen)
if err != nil {
t.log.Debug("Invalid record in "+response.Name(), "id", c.node.ID(), "err", err)
continue
}
nodes = append(nodes, node)
}
if total == -1 {
total = min(int(response.RespCount), totalNodesResponseLimit)
}
if received++; received == total {
return nodes, nil
}
case err := <-c.err:
return nodes, err
}
}
}
// verifyResponseNode checks validity of a record in a NODES response.
func (t *UDPv5) verifyResponseNode(c *callV5, r *enr.Record, distances []uint, seen map[enode.ID]struct{}) (*enode.Node, error) {
node, err := enode.New(t.validSchemes, r)
if err != nil {
return nil, err
}
if err := netutil.CheckRelayIP(c.addr.Addr().AsSlice(), node.IP()); err != nil {
return nil, err
}
if t.netrestrict != nil && !t.netrestrict.Contains(node.IP()) {
return nil, errors.New("not contained in netrestrict list")
}
if node.UDP() <= 1024 {
return nil, errLowPort
}
if distances != nil {
nd := enode.LogDist(c.id, node.ID())
if !slices.Contains(distances, uint(nd)) {
return nil, errors.New("does not match any requested distance")
}
}
if _, ok := seen[node.ID()]; ok {
return nil, errors.New("duplicate record")
}
seen[node.ID()] = struct{}{}
return node, nil
}
// callToNode sends the given call and sets up a handler for response packets (of message
// type responseType). Responses are dispatched to the call's response channel.
func (t *UDPv5) callToNode(n *enode.Node, responseType byte, req v5wire.Packet) *callV5 {
addr, _ := n.UDPEndpoint()
c := &callV5{id: n.ID(), addr: addr, node: n}
t.initCall(c, responseType, req)
return c
}
// callToID is like callToNode, but for cases where the node record is not available.
func (t *UDPv5) callToID(id enode.ID, addr netip.AddrPort, responseType byte, req v5wire.Packet) *callV5 {
c := &callV5{id: id, addr: addr}
t.initCall(c, responseType, req)
return c
}
func (t *UDPv5) initCall(c *callV5, responseType byte, packet v5wire.Packet) {
c.packet = packet
c.responseType = responseType
c.reqid = make([]byte, 8)
c.ch = make(chan v5wire.Packet, 1)
c.err = make(chan error, 1)
// Assign request ID.
crand.Read(c.reqid)
packet.SetRequestID(c.reqid)
// Send call to dispatch.
select {
case t.callCh <- c:
case <-t.closeCtx.Done():
c.err <- errClosed
}
}
// callDone tells dispatch that the active call is done.
func (t *UDPv5) callDone(c *callV5) {
// This needs a loop because further responses may be incoming until the
// send to callDoneCh has completed. Such responses need to be discarded
// in order to avoid blocking the dispatch loop.
for {
select {
case <-c.ch:
// late response, discard.
case <-c.err:
// late error, discard.
case t.callDoneCh <- c:
return
case <-t.closeCtx.Done():
return
}
}
}
// dispatch runs in its own goroutine, handles incoming packets and deals with calls.
//
// For any destination node there is at most one 'active call', stored in the t.activeCall*
// maps. A call is made active when it is sent. The active call can be answered by a
// matching response, in which case c.ch receives the response; or by timing out, in which case
// c.err receives the error. When the function that created the call signals the active
// call is done through callDone, the next call from the call queue is started.
//
// Calls may also be answered by a WHOAREYOU packet referencing the call packet's authTag.
// When that happens the call is simply re-sent to complete the handshake. We allow one
// handshake attempt per call.
func (t *UDPv5) dispatch() {
defer t.wg.Done()
// Arm first read.
t.readNextCh <- struct{}{}
for {
select {
case c := <-t.callCh:
t.callQueue[c.id] = append(t.callQueue[c.id], c)
t.sendNextCall(c.id)
case ct := <-t.respTimeoutCh:
active := t.activeCallByNode[ct.c.id]
if ct.c == active && ct.timer == active.timeout {
ct.c.err <- errTimeout
}
case c := <-t.callDoneCh:
active := t.activeCallByNode[c.id]
if active != c {
panic("BUG: callDone for inactive call")
}
c.timeout.Stop()
delete(t.activeCallByAuth, c.nonce)
delete(t.activeCallByNode, c.id)
t.sendNextCall(c.id)
case r := <-t.sendCh:
t.send(r.destID, r.destAddr, r.msg, nil)
case p := <-t.packetInCh:
t.handlePacket(p.Data, p.Addr)
// Arm next read.
t.readNextCh <- struct{}{}
case <-t.closeCtx.Done():
close(t.readNextCh)
for id, queue := range t.callQueue {
for _, c := range queue {
c.err <- errClosed
}
delete(t.callQueue, id)
}
for id, c := range t.activeCallByNode {
c.err <- errClosed
delete(t.activeCallByNode, id)
delete(t.activeCallByAuth, c.nonce)
}
return
}
}
}
// startResponseTimeout sets the response timer for a call.
func (t *UDPv5) startResponseTimeout(c *callV5) {
if c.timeout != nil {
c.timeout.Stop()
}
var (
timer mclock.Timer
done = make(chan struct{})
)
timer = t.clock.AfterFunc(respTimeoutV5, func() {
<-done
select {
case t.respTimeoutCh <- &callTimeout{c, timer}:
case <-t.closeCtx.Done():
}
})
c.timeout = timer
close(done)
}
// sendNextCall sends the next call in the call queue if there is no active call.
func (t *UDPv5) sendNextCall(id enode.ID) {
queue := t.callQueue[id]
if len(queue) == 0 || t.activeCallByNode[id] != nil {
return
}
t.activeCallByNode[id] = queue[0]
t.sendCall(t.activeCallByNode[id])
if len(queue) == 1 {
delete(t.callQueue, id)
} else {
copy(queue, queue[1:])
t.callQueue[id] = queue[:len(queue)-1]
}
}
// sendCall encodes and sends a request packet to the call's recipient node.
// This performs a handshake if needed.
func (t *UDPv5) sendCall(c *callV5) {
// The call might have a nonce from a previous handshake attempt. Remove the entry for
// the old nonce because we're about to generate a new nonce for this call.
if c.nonce != (v5wire.Nonce{}) {
delete(t.activeCallByAuth, c.nonce)
}
newNonce, _ := t.send(c.id, c.addr, c.packet, c.challenge)
c.nonce = newNonce
t.activeCallByAuth[newNonce] = c
t.startResponseTimeout(c)
}
// sendResponse sends a response packet to the given node.
// This doesn't trigger a handshake even if no keys are available.
func (t *UDPv5) sendResponse(toID enode.ID, toAddr netip.AddrPort, packet v5wire.Packet) error {
_, err := t.send(toID, toAddr, packet, nil)
return err
}
func (t *UDPv5) sendFromAnotherThread(toID enode.ID, toAddr netip.AddrPort, packet v5wire.Packet) {
select {
case t.sendCh <- sendRequest{toID, toAddr, packet}:
case <-t.closeCtx.Done():
}
}
// send sends a packet to the given node.
func (t *UDPv5) send(toID enode.ID, toAddr netip.AddrPort, packet v5wire.Packet, c *v5wire.Whoareyou) (v5wire.Nonce, error) {
addr := toAddr.String()
t.logcontext = append(t.logcontext[:0], "id", toID, "addr", addr)
t.logcontext = packet.AppendLogInfo(t.logcontext)
enc, nonce, err := t.codec.Encode(toID, addr, packet, c)
if err != nil {
t.logcontext = append(t.logcontext, "err", err)
t.log.Warn(">> "+packet.Name(), t.logcontext...)
return nonce, err
}
_, err = t.conn.WriteToUDPAddrPort(enc, toAddr)
t.log.Trace(">> "+packet.Name(), t.logcontext...)
return nonce, err
}
// readLoop runs in its own goroutine and reads packets from the network.
func (t *UDPv5) readLoop() {
defer t.wg.Done()
buf := make([]byte, maxPacketSize)
for range t.readNextCh {
nbytes, from, err := t.conn.ReadFromUDPAddrPort(buf)
if netutil.IsTemporaryError(err) {
// Ignore temporary read errors.
t.log.Debug("Temporary UDP read error", "err", err)
continue
} else if err != nil {
// Shut down the loop for permanent errors.
if !errors.Is(err, io.EOF) {
t.log.Debug("UDP read error", "err", err)
}
return
}
t.dispatchReadPacket(from, buf[:nbytes])
}
}
// dispatchReadPacket sends a packet into the dispatch loop.
func (t *UDPv5) dispatchReadPacket(from netip.AddrPort, content []byte) bool {
select {
case t.packetInCh <- ReadPacket{content, from}:
return true
case <-t.closeCtx.Done():
return false
}
}
// handlePacket decodes and processes an incoming packet from the network.
func (t *UDPv5) handlePacket(rawpacket []byte, fromAddr netip.AddrPort) error {
addr := fromAddr.String()
fromID, fromNode, packet, err := t.codec.Decode(rawpacket, addr)
if err != nil {
if t.unhandled != nil && v5wire.IsInvalidHeader(err) {
// The packet seems unrelated to discv5, send it to the next protocol.
// t.log.Trace("Unhandled discv5 packet", "id", fromID, "addr", addr, "err", err)
up := ReadPacket{Data: make([]byte, len(rawpacket)), Addr: fromAddr}
copy(up.Data, rawpacket)
t.unhandled <- up
return nil
}
t.log.Debug("Bad discv5 packet", "id", fromID, "addr", addr, "err", err)
return err
}
if fromNode != nil {
// Handshake succeeded, add to table.
t.tab.addInboundNode(fromNode)
}
if packet.Kind() != v5wire.WhoareyouPacket {
// WHOAREYOU logged separately to report errors.
t.logcontext = append(t.logcontext[:0], "id", fromID, "addr", addr)
t.logcontext = packet.AppendLogInfo(t.logcontext)
t.log.Trace("<< "+packet.Name(), t.logcontext...)
}
t.handle(packet, fromID, fromAddr)
return nil
}
// handleCallResponse dispatches a response packet to the call waiting for it.
func (t *UDPv5) handleCallResponse(fromID enode.ID, fromAddr netip.AddrPort, p v5wire.Packet) bool {
ac := t.activeCallByNode[fromID]
if ac == nil || !bytes.Equal(p.RequestID(), ac.reqid) {
t.log.Debug(fmt.Sprintf("Unsolicited/late %s response", p.Name()), "id", fromID, "addr", fromAddr)
return false
}
if fromAddr != ac.addr {
t.log.Debug(fmt.Sprintf("%s from wrong endpoint", p.Name()), "id", fromID, "addr", fromAddr)
return false
}
if p.Kind() != ac.responseType {
t.log.Debug(fmt.Sprintf("Wrong discv5 response type %s", p.Name()), "id", fromID, "addr", fromAddr)
return false
}
t.startResponseTimeout(ac)
ac.ch <- p
return true
}
// getNode looks for a node record in table and database.
func (t *UDPv5) getNode(id enode.ID) *enode.Node {
if n := t.tab.getNode(id); n != nil {
return n
}
if n := t.localNode.Database().Node(id); n != nil {
return n
}
return nil
}
// handle processes incoming packets according to their message type.
func (t *UDPv5) handle(p v5wire.Packet, fromID enode.ID, fromAddr netip.AddrPort) {
switch p := p.(type) {
case *v5wire.Unknown:
t.handleUnknown(p, fromID, fromAddr)
case *v5wire.Whoareyou:
t.handleWhoareyou(p, fromID, fromAddr)
case *v5wire.Ping:
t.handlePing(p, fromID, fromAddr)
case *v5wire.Pong:
if t.handleCallResponse(fromID, fromAddr, p) {
fromUDPAddr := &net.UDPAddr{IP: fromAddr.Addr().AsSlice(), Port: int(fromAddr.Port())}
toUDPAddr := &net.UDPAddr{IP: p.ToIP, Port: int(p.ToPort)}
t.localNode.UDPEndpointStatement(fromUDPAddr, toUDPAddr)
}
case *v5wire.Findnode:
t.handleFindnode(p, fromID, fromAddr)
case *v5wire.Nodes:
t.handleCallResponse(fromID, fromAddr, p)
case *v5wire.TalkRequest:
t.talk.handleRequest(fromID, fromAddr, p)
case *v5wire.TalkResponse:
t.handleCallResponse(fromID, fromAddr, p)
}
}
// handleUnknown initiates a handshake by responding with WHOAREYOU.
func (t *UDPv5) handleUnknown(p *v5wire.Unknown, fromID enode.ID, fromAddr netip.AddrPort) {
challenge := &v5wire.Whoareyou{Nonce: p.Nonce}
crand.Read(challenge.IDNonce[:])
if n := t.getNode(fromID); n != nil {
challenge.Node = n
challenge.RecordSeq = n.Seq()
}
t.sendResponse(fromID, fromAddr, challenge)
}
var (
errChallengeNoCall = errors.New("no matching call")
errChallengeTwice = errors.New("second handshake")
)
// handleWhoareyou resends the active call as a handshake packet.
func (t *UDPv5) handleWhoareyou(p *v5wire.Whoareyou, fromID enode.ID, fromAddr netip.AddrPort) {
c, err := t.matchWithCall(fromID, p.Nonce)
if err != nil {
t.log.Debug("Invalid "+p.Name(), "addr", fromAddr, "err", err)
return
}
if c.node == nil {
// Can't perform handshake because we don't have the ENR.
t.log.Debug("Can't handle "+p.Name(), "addr", fromAddr, "err", "call has no ENR")
c.err <- errors.New("remote wants handshake, but call has no ENR")
return
}
// Resend the call that was answered by WHOAREYOU.
t.log.Trace("<< "+p.Name(), "id", c.node.ID(), "addr", fromAddr)
c.handshakeCount++
c.challenge = p
p.Node = c.node
t.sendCall(c)
}
// matchWithCall checks whether a handshake attempt matches the active call.
func (t *UDPv5) matchWithCall(fromID enode.ID, nonce v5wire.Nonce) (*callV5, error) {
c := t.activeCallByAuth[nonce]
if c == nil {
return nil, errChallengeNoCall
}
if c.handshakeCount > 0 {
return nil, errChallengeTwice
}
return c, nil
}
// handlePing sends a PONG response.
func (t *UDPv5) handlePing(p *v5wire.Ping, fromID enode.ID, fromAddr netip.AddrPort) {
var remoteIP net.IP
// Handle IPv4 mapped IPv6 addresses in the event the local node is binded
// to an ipv6 interface.
if fromAddr.Addr().Is4() || fromAddr.Addr().Is4In6() {
ip4 := fromAddr.Addr().As4()
remoteIP = ip4[:]
} else {
remoteIP = fromAddr.Addr().AsSlice()
}
t.sendResponse(fromID, fromAddr, &v5wire.Pong{
ReqID: p.ReqID,
ToIP: remoteIP,
ToPort: fromAddr.Port(),
ENRSeq: t.localNode.Node().Seq(),
})
}
// handleFindnode returns nodes to the requester.
func (t *UDPv5) handleFindnode(p *v5wire.Findnode, fromID enode.ID, fromAddr netip.AddrPort) {
nodes := t.collectTableNodes(fromAddr.Addr(), p.Distances, findnodeResultLimit)
for _, resp := range packNodes(p.ReqID, nodes) {
t.sendResponse(fromID, fromAddr, resp)
}
}
// collectTableNodes creates a FINDNODE result set for the given distances.
func (t *UDPv5) collectTableNodes(rip netip.Addr, distances []uint, limit int) []*enode.Node {
ripSlice := rip.AsSlice()
var bn []*enode.Node
var nodes []*enode.Node
var processed = make(map[uint]struct{})
for _, dist := range distances {
// Reject duplicate / invalid distances.
_, seen := processed[dist]
if seen || dist > 256 {
continue
}
processed[dist] = struct{}{}
for _, n := range t.tab.appendLiveNodes(dist, bn[:0]) {
// Apply some pre-checks to avoid sending invalid nodes.
// Note liveness is checked by appendLiveNodes.
if netutil.CheckRelayIP(ripSlice, n.IP()) != nil {
continue
}
nodes = append(nodes, n)
if len(nodes) >= limit {
return nodes
}
}
}
return nodes
}
// packNodes creates NODES response packets for the given node list.
func packNodes(reqid []byte, nodes []*enode.Node) []*v5wire.Nodes {
if len(nodes) == 0 {
return []*v5wire.Nodes{{ReqID: reqid, RespCount: 1}}
}
// This limit represents the available space for nodes in output packets. Maximum
// packet size is 1280, and out of this ~80 bytes will be taken up by the packet
// frame. So limiting to 1000 bytes here leaves 200 bytes for other fields of the
// NODES message, which is a lot.
const sizeLimit = 1000
var resp []*v5wire.Nodes
for len(nodes) > 0 {
p := &v5wire.Nodes{ReqID: reqid}
size := uint64(0)
for len(nodes) > 0 {
r := nodes[0].Record()
if size += r.Size(); size > sizeLimit {
break
}
p.Nodes = append(p.Nodes, r)
nodes = nodes[1:]
}
resp = append(resp, p)
}
for _, msg := range resp {
msg.RespCount = uint8(len(resp))
}
return resp
}