// Copyright 2015 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 discv5
import (
"bytes"
"crypto/ecdsa"
"errors"
"fmt"
"net"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/logger"
"github.com/ethereum/go-ethereum/logger/glog"
"github.com/ethereum/go-ethereum/p2p/nat"
"github.com/ethereum/go-ethereum/rlp"
)
const Version = 4
// Errors
var (
errPacketTooSmall = errors.New("too small")
errBadHash = errors.New("bad hash")
errExpired = errors.New("expired")
errUnsolicitedReply = errors.New("unsolicited reply")
errUnknownNode = errors.New("unknown node")
errTimeout = errors.New("RPC timeout")
errClockWarp = errors.New("reply deadline too far in the future")
errClosed = errors.New("socket closed")
)
// Timeouts
const (
respTimeout = 500 * time.Millisecond
sendTimeout = 500 * time.Millisecond
expiration = 20 * time.Second
ntpFailureThreshold = 32 // Continuous timeouts after which to check NTP
ntpWarningCooldown = 10 * time.Minute // Minimum amount of time to pass before repeating NTP warning
driftThreshold = 10 * time.Second // Allowed clock drift before warning user
)
// RPC request structures
type (
ping struct {
Version uint
From, To rpcEndpoint
Expiration uint64
// v5
Topics []Topic
// Ignore additional fields (for forward compatibility).
Rest []rlp.RawValue `rlp:"tail"`
}
// pong is the reply to ping.
pong struct {
// This field should mirror the UDP envelope address
// of the ping packet, which provides a way to discover the
// the external address (after NAT).
To rpcEndpoint
ReplyTok []byte // This contains the hash of the ping packet.
Expiration uint64 // Absolute timestamp at which the packet becomes invalid.
// v5
TopicHash common.Hash
TicketSerial uint32
WaitPeriods []uint32
// Ignore additional fields (for forward compatibility).
Rest []rlp.RawValue `rlp:"tail"`
}
// findnode is a query for nodes close to the given target.
findnode struct {
Target NodeID // doesn't need to be an actual public key
Expiration uint64
// Ignore additional fields (for forward compatibility).
Rest []rlp.RawValue `rlp:"tail"`
}
// findnode is a query for nodes close to the given target.
findnodeHash struct {
Target common.Hash
Expiration uint64
// Ignore additional fields (for forward compatibility).
Rest []rlp.RawValue `rlp:"tail"`
}
// reply to findnode
neighbors struct {
Nodes []rpcNode
Expiration uint64
// Ignore additional fields (for forward compatibility).
Rest []rlp.RawValue `rlp:"tail"`
}
topicRegister struct {
Topics []Topic
Idx uint
Pong []byte
}
topicQuery struct {
Topic Topic
Expiration uint64
}
// reply to topicQuery
topicNodes struct {
Echo common.Hash
Nodes []rpcNode
}
rpcNode struct {
IP net.IP // len 4 for IPv4 or 16 for IPv6
UDP uint16 // for discovery protocol
TCP uint16 // for RLPx protocol
ID NodeID
}
rpcEndpoint struct {
IP net.IP // len 4 for IPv4 or 16 for IPv6
UDP uint16 // for discovery protocol
TCP uint16 // for RLPx protocol
}
)
const (
macSize = 256 / 8
sigSize = 520 / 8
headSize = macSize + sigSize // space of packet frame data
)
// Neighbors replies are sent across multiple packets to
// stay below the 1280 byte limit. We compute the maximum number
// of entries by stuffing a packet until it grows too large.
var maxNeighbors = func() int {
p := neighbors{Expiration: ^uint64(0)}
maxSizeNode := rpcNode{IP: make(net.IP, 16), UDP: ^uint16(0), TCP: ^uint16(0)}
for n := 0; ; n++ {
p.Nodes = append(p.Nodes, maxSizeNode)
size, _, err := rlp.EncodeToReader(p)
if err != nil {
// If this ever happens, it will be caught by the unit tests.
panic("cannot encode: " + err.Error())
}
if headSize+size+1 >= 1280 {
return n
}
}
}()
var maxTopicNodes = func() int {
p := topicNodes{}
maxSizeNode := rpcNode{IP: make(net.IP, 16), UDP: ^uint16(0), TCP: ^uint16(0)}
for n := 0; ; n++ {
p.Nodes = append(p.Nodes, maxSizeNode)
size, _, err := rlp.EncodeToReader(p)
if err != nil {
// If this ever happens, it will be caught by the unit tests.
panic("cannot encode: " + err.Error())
}
if headSize+size+1 >= 1280 {
return n
}
}
}()
func makeEndpoint(addr *net.UDPAddr, tcpPort uint16) rpcEndpoint {
ip := addr.IP.To4()
if ip == nil {
ip = addr.IP.To16()
}
return rpcEndpoint{IP: ip, UDP: uint16(addr.Port), TCP: tcpPort}
}
func (e1 rpcEndpoint) equal(e2 rpcEndpoint) bool {
return e1.UDP == e2.UDP && e1.TCP == e2.TCP && bytes.Equal(e1.IP, e2.IP)
}
func nodeFromRPC(rn rpcNode) (*Node, error) {
// TODO: don't accept localhost, LAN addresses from internet hosts
n := NewNode(rn.ID, rn.IP, rn.UDP, rn.TCP)
err := n.validateComplete()
return n, err
}
func nodeToRPC(n *Node) rpcNode {
return rpcNode{ID: n.ID, IP: n.IP, UDP: n.UDP, TCP: n.TCP}
}
type ingressPacket struct {
remoteID NodeID
remoteAddr *net.UDPAddr
ev nodeEvent
hash []byte
data interface{} // one of the RPC structs
rawData []byte
}
type conn interface {
ReadFromUDP(b []byte) (n int, addr *net.UDPAddr, err error)
WriteToUDP(b []byte, addr *net.UDPAddr) (n int, err error)
Close() error
LocalAddr() net.Addr
}
// udp implements the RPC protocol.
type udp struct {
conn conn
priv *ecdsa.PrivateKey
ourEndpoint rpcEndpoint
nat nat.Interface
net *Network
}
// ListenUDP returns a new table that listens for UDP packets on laddr.
func ListenUDP(priv *ecdsa.PrivateKey, laddr string, natm nat.Interface, nodeDBPath string) (*Network, error) {
transport, err := listenUDP(priv, laddr)
if err != nil {
return nil, err
}
net, err := newNetwork(transport, priv.PublicKey, natm, nodeDBPath)
if err != nil {
return nil, err
}
transport.net = net
go transport.readLoop()
return net, nil
}
func listenUDP(priv *ecdsa.PrivateKey, laddr string) (*udp, error) {
addr, err := net.ResolveUDPAddr("udp", laddr)
if err != nil {
return nil, err
}
conn, err := net.ListenUDP("udp", addr)
if err != nil {
return nil, err
}
return &udp{conn: conn, priv: priv, ourEndpoint: makeEndpoint(addr, uint16(addr.Port))}, nil
}
func (t *udp) localAddr() *net.UDPAddr {
return t.conn.LocalAddr().(*net.UDPAddr)
}
func (t *udp) Close() {
t.conn.Close()
}
func (t *udp) send(remote *Node, ptype nodeEvent, data interface{}) (hash []byte) {
hash, _ = t.sendPacket(remote.ID, remote.addr(), byte(ptype), data)
return hash
}
func (t *udp) sendPing(remote *Node, toaddr *net.UDPAddr, topics []Topic) (hash []byte) {
hash, _ = t.sendPacket(remote.ID, toaddr, byte(pingPacket), ping{
Version: Version,
From: t.ourEndpoint,
To: makeEndpoint(toaddr, uint16(toaddr.Port)), // TODO: maybe use known TCP port from DB
Expiration: uint64(time.Now().Add(expiration).Unix()),
Topics: topics,
})
return hash
}
func (t *udp) sendFindnode(remote *Node, target NodeID) {
t.sendPacket(remote.ID, remote.addr(), byte(findnodePacket), findnode{
Target: target,
Expiration: uint64(time.Now().Add(expiration).Unix()),
})
}
func (t *udp) sendNeighbours(remote *Node, results []*Node) {
// Send neighbors in chunks with at most maxNeighbors per packet
// to stay below the 1280 byte limit.
p := neighbors{Expiration: uint64(time.Now().Add(expiration).Unix())}
for i, result := range results {
p.Nodes = append(p.Nodes, nodeToRPC(result))
if len(p.Nodes) == maxNeighbors || i == len(results)-1 {
t.sendPacket(remote.ID, remote.addr(), byte(neighborsPacket), p)
p.Nodes = p.Nodes[:0]
}
}
}
func (t *udp) sendFindnodeHash(remote *Node, target common.Hash) {
t.sendPacket(remote.ID, remote.addr(), byte(findnodeHashPacket), findnodeHash{
Target: target,
Expiration: uint64(time.Now().Add(expiration).Unix()),
})
}
func (t *udp) sendTopicRegister(remote *Node, topics []Topic, idx int, pong []byte) {
t.sendPacket(remote.ID, remote.addr(), byte(topicRegisterPacket), topicRegister{
Topics: topics,
Idx: uint(idx),
Pong: pong,
})
}
func (t *udp) sendTopicNodes(remote *Node, queryHash common.Hash, nodes []*Node) {
p := topicNodes{Echo: queryHash}
if len(nodes) == 0 {
t.sendPacket(remote.ID, remote.addr(), byte(topicNodesPacket), p)
return
}
for i, result := range nodes {
p.Nodes = append(p.Nodes, nodeToRPC(result))
if len(p.Nodes) == maxTopicNodes || i == len(nodes)-1 {
t.sendPacket(remote.ID, remote.addr(), byte(topicNodesPacket), p)
p.Nodes = p.Nodes[:0]
}
}
}
func (t *udp) sendPacket(toid NodeID, toaddr *net.UDPAddr, ptype byte, req interface{}) (hash []byte, err error) {
packet, hash, err := encodePacket(t.priv, ptype, req)
if err != nil {
return hash, err
}
glog.V(logger.Detail).Infof(">>> %v to %x@%v\n", nodeEvent(ptype), toid[:8], toaddr)
if _, err = t.conn.WriteToUDP(packet, toaddr); err != nil {
glog.V(logger.Detail).Infoln("UDP send failed:", err)
}
return hash, err
}
// zeroed padding space for encodePacket.
var headSpace = make([]byte, headSize)
func encodePacket(priv *ecdsa.PrivateKey, ptype byte, req interface{}) (p, hash []byte, err error) {
b := new(bytes.Buffer)
b.Write(headSpace)
b.WriteByte(ptype)
if err := rlp.Encode(b, req); err != nil {
glog.V(logger.Error).Infoln("error encoding packet:", err)
return nil, nil, err
}
packet := b.Bytes()
sig, err := crypto.Sign(crypto.Keccak256(packet[headSize:]), priv)
if err != nil {
glog.V(logger.Error).Infoln("could not sign packet:", err)
return nil, nil, err
}
copy(packet[macSize:], sig)
// add the hash to the front. Note: this doesn't protect the
// packet in any way.
hash = crypto.Keccak256(packet[macSize:])
copy(packet, hash)
return packet, hash, nil
}
// readLoop runs in its own goroutine. it injects ingress UDP packets
// into the network loop.
func (t *udp) readLoop() {
defer t.conn.Close()
// Discovery packets are defined to be no larger than 1280 bytes.
// Packets larger than this size will be cut at the end and treated
// as invalid because their hash won't match.
buf := make([]byte, 1280)
for {
nbytes, from, err := t.conn.ReadFromUDP(buf)
if isTemporaryError(err) {
// Ignore temporary read errors.
glog.V(logger.Debug).Infof("Temporary read error: %v", err)
continue
} else if err != nil {
// Shut down the loop for permament errors.
glog.V(logger.Debug).Infof("Read error: %v", err)
return
}
t.handlePacket(from, buf[:nbytes])
}
}
func isTemporaryError(err error) bool {
tempErr, ok := err.(interface {
Temporary() bool
})
return ok && tempErr.Temporary() || isPacketTooBig(err)
}
func (t *udp) handlePacket(from *net.UDPAddr, buf []byte) error {
pkt := ingressPacket{remoteAddr: from}
if err := decodePacket(buf, &pkt); err != nil {
glog.V(logger.Debug).Infof("Bad packet from %v: %v\n", from, err)
return err
}
t.net.reqReadPacket(pkt)
return nil
}
func decodePacket(buffer []byte, pkt *ingressPacket) error {
if len(buffer) < headSize+1 {
return errPacketTooSmall
}
buf := make([]byte, len(buffer))
copy(buf, buffer)
hash, sig, sigdata := buf[:macSize], buf[macSize:headSize], buf[headSize:]
shouldhash := crypto.Keccak256(buf[macSize:])
if !bytes.Equal(hash, shouldhash) {
return errBadHash
}
fromID, err := recoverNodeID(crypto.Keccak256(buf[headSize:]), sig)
if err != nil {
return err
}
pkt.rawData = buf
pkt.hash = hash
pkt.remoteID = fromID
switch pkt.ev = nodeEvent(sigdata[0]); pkt.ev {
case pingPacket:
pkt.data = new(ping)
case pongPacket:
pkt.data = new(pong)
case findnodePacket:
pkt.data = new(findnode)
case neighborsPacket:
pkt.data = new(neighbors)
case findnodeHashPacket:
pkt.data = new(findnodeHash)
case topicRegisterPacket:
pkt.data = new(topicRegister)
case topicQueryPacket:
pkt.data = new(topicQuery)
case topicNodesPacket:
pkt.data = new(topicNodes)
default:
return fmt.Errorf("unknown packet type: %d", sigdata[0])
}
s := rlp.NewStream(bytes.NewReader(sigdata[1:]), 0)
err = s.Decode(pkt.data)
return err
}
