plugeth/p2p/discover/udp.go
Felix Lange fc747ef4a6 p2p/discover: new endpoint format
This commit changes the discovery protocol to use the new "v4" endpoint
format, which allows for separate UDP and TCP ports and makes it
possible to discover the UDP address after NAT.
2015-04-30 14:57:33 +02:00

512 lines
13 KiB
Go

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/logger/glog"
"github.com/ethereum/go-ethereum/p2p/nat"
"github.com/ethereum/go-ethereum/rlp"
)
const Version = 3
// Errors
var (
errPacketTooSmall = errors.New("too small")
errBadHash = errors.New("bad hash")
errExpired = errors.New("expired")
errBadVersion = errors.New("version mismatch")
errUnsolicitedReply = errors.New("unsolicited reply")
errUnknownNode = errors.New("unknown node")
errTimeout = errors.New("RPC timeout")
errClosed = errors.New("socket closed")
)
// Timeouts
const (
respTimeout = 300 * time.Millisecond
sendTimeout = 300 * time.Millisecond
expiration = 20 * 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 {
Version uint
From, To rpcEndpoint
Expiration uint64
}
// 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.
}
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
}
rpcEndpoint struct {
IP net.IP // len 4 for IPv4 or 16 for IPv6
UDP uint16 // for discovery protocol
TCP uint16 // for RLPx protocol
}
)
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 validNode(n *Node) bool {
// TODO: don't accept localhost, LAN addresses from internet hosts
return !n.IP.IsMulticast() && !n.IP.IsUnspecified() && n.UDP != 0
}
type packet interface {
handle(t *udp, from *net.UDPAddr, fromID NodeID, mac []byte) error
}
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
addpending chan *pending
gotreply chan reply
closing chan struct{}
nat nat.Interface
*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{}
// loop indicates whether there was
// a matching request by sending on this channel.
matched chan<- bool
}
// ListenUDP returns a new table that listens for UDP packets on laddr.
func ListenUDP(priv *ecdsa.PrivateKey, laddr string, natm nat.Interface, nodeDBPath string) (*Table, 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
}
tab, _ := newUDP(priv, conn, natm, nodeDBPath)
glog.V(logger.Info).Infoln("Listening,", tab.self)
return tab, nil
}
func newUDP(priv *ecdsa.PrivateKey, c conn, natm nat.Interface, nodeDBPath string) (*Table, *udp) {
udp := &udp{
conn: c,
priv: priv,
closing: make(chan struct{}),
gotreply: make(chan reply),
addpending: make(chan *pending),
}
realaddr := c.LocalAddr().(*net.UDPAddr)
if natm != nil {
if !realaddr.IP.IsLoopback() {
go nat.Map(natm, udp.closing, "udp", realaddr.Port, realaddr.Port, "ethereum discovery")
}
// TODO: react to external IP changes over time.
if ext, err := natm.ExternalIP(); err == nil {
realaddr = &net.UDPAddr{IP: ext, Port: realaddr.Port}
}
}
// TODO: separate TCP port
udp.ourEndpoint = makeEndpoint(realaddr, uint16(realaddr.Port))
udp.Table = newTable(udp, PubkeyID(&priv.PublicKey), realaddr, nodeDBPath)
go udp.loop()
go udp.readLoop()
return udp.Table, udp
}
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(toid NodeID, toaddr *net.UDPAddr) error {
// TODO: maybe check for ReplyTo field in callback to measure RTT
errc := t.pending(toid, pongPacket, func(interface{}) bool { return true })
t.send(toaddr, pingPacket, ping{
Version: Version,
From: t.ourEndpoint,
To: makeEndpoint(toaddr, 0), // TODO: maybe use known TCP port from DB
Expiration: uint64(time.Now().Add(expiration).Unix()),
})
return <-errc
}
func (t *udp) waitping(from NodeID) error {
return <-t.pending(from, pingPacket, func(interface{}) bool { return true })
}
// findnode sends a findnode request to the given node and waits until
// the node has sent up to k neighbors.
func (t *udp) findnode(toid NodeID, toaddr *net.UDPAddr, target NodeID) ([]*Node, error) {
nodes := make([]*Node, 0, bucketSize)
nreceived := 0
errc := t.pending(toid, neighborsPacket, func(r interface{}) bool {
reply := r.(*neighbors)
for _, n := range reply.Nodes {
nreceived++
if validNode(n) {
nodes = append(nodes, n)
}
}
return nreceived >= bucketSize
})
t.send(toaddr, findnodePacket, findnode{
Target: target,
Expiration: uint64(time.Now().Add(expiration).Unix()),
})
err := <-errc
return nodes, err
}
// 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
}
func (t *udp) handleReply(from NodeID, ptype byte, req packet) bool {
matched := make(chan bool)
select {
case t.gotreply <- reply{from, ptype, req, matched}:
// loop will handle it
return <-matched
case <-t.closing:
return false
}
}
// 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() {
now := time.Now()
if len(pending) == 0 || now.Before(nextDeadline) {
return
}
nextDeadline = pending[0].deadline
timeout.Reset(nextDeadline.Sub(now))
}
for {
select {
case <-refresh.C:
go t.refresh()
case <-t.closing:
for _, p := range pending {
p.errc <- errClosed
}
pending = nil
return
case p := <-t.addpending:
p.deadline = time.Now().Add(respTimeout)
pending = append(pending, p)
rearmTimeout()
case r := <-t.gotreply:
var matched bool
for i := 0; i < len(pending); i++ {
if p := pending[i]; p.from == r.from && p.ptype == r.ptype {
matched = true
if p.callback(r.data) {
// callback indicates the request is done, remove it.
p.errc <- nil
copy(pending[i:], pending[i+1:])
pending = pending[:len(pending)-1]
i--
}
}
}
r.matched <- matched
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(toaddr *net.UDPAddr, ptype byte, req interface{}) error {
packet, err := encodePacket(t.priv, ptype, req)
if err != nil {
return err
}
glog.V(logger.Detail).Infof(">>> %v %T\n", toaddr, req)
if _, err = t.conn.WriteToUDP(packet, toaddr); err != nil {
glog.V(logger.Detail).Infoln("UDP send failed:", err)
}
return err
}
func encodePacket(priv *ecdsa.PrivateKey, ptype byte, req interface{}) ([]byte, 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, err
}
packet := b.Bytes()
sig, err := crypto.Sign(crypto.Sha3(packet[headSize:]), priv)
if err != nil {
glog.V(logger.Error).Infoln("could not sign packet:", err)
return nil, 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:]))
return packet, nil
}
// 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
}
t.handlePacket(from, buf[:nbytes])
}
}
func (t *udp) handlePacket(from *net.UDPAddr, buf []byte) error {
packet, fromID, hash, err := decodePacket(buf)
if err != nil {
glog.V(logger.Debug).Infof("Bad packet from %v: %v\n", from, err)
return err
}
status := "ok"
if err = packet.handle(t, from, fromID, hash); err != nil {
status = err.Error()
}
glog.V(logger.Detail).Infof("<<< %v %T: %s\n", from, packet, status)
return err
}
func decodePacket(buf []byte) (packet, NodeID, []byte, error) {
if len(buf) < headSize+1 {
return nil, NodeID{}, nil, errPacketTooSmall
}
hash, sig, sigdata := buf[:macSize], buf[macSize:headSize], buf[headSize:]
shouldhash := crypto.Sha3(buf[macSize:])
if !bytes.Equal(hash, shouldhash) {
return nil, NodeID{}, nil, errBadHash
}
fromID, err := recoverNodeID(crypto.Sha3(buf[headSize:]), sig)
if err != nil {
return nil, NodeID{}, hash, err
}
var req packet
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 nil, fromID, hash, fmt.Errorf("unknown type: %d", ptype)
}
err = rlp.DecodeBytes(sigdata[1:], req)
return req, fromID, hash, err
}
func (req *ping) handle(t *udp, from *net.UDPAddr, fromID NodeID, mac []byte) error {
if expired(req.Expiration) {
return errExpired
}
if req.Version != Version {
return errBadVersion
}
t.send(from, pongPacket, pong{
To: makeEndpoint(from, req.From.TCP),
ReplyTok: mac,
Expiration: uint64(time.Now().Add(expiration).Unix()),
})
if !t.handleReply(fromID, pingPacket, req) {
// Note: we're ignoring the provided IP address right now
go t.bond(true, fromID, from, req.From.TCP)
}
return nil
}
func (req *pong) handle(t *udp, from *net.UDPAddr, fromID NodeID, mac []byte) error {
if expired(req.Expiration) {
return errExpired
}
if !t.handleReply(fromID, pongPacket, req) {
return errUnsolicitedReply
}
return nil
}
func (req *findnode) handle(t *udp, from *net.UDPAddr, fromID NodeID, mac []byte) error {
if expired(req.Expiration) {
return errExpired
}
if t.db.node(fromID) == nil {
// No bond exists, we don't process the packet. This prevents
// an attack vector where the discovery protocol could be used
// to amplify traffic in a DDOS attack. A malicious actor
// would send a findnode request with the IP address and UDP
// port of the target as the source address. The recipient of
// the findnode packet would then send a neighbors packet
// (which is a much bigger packet than findnode) to the victim.
return errUnknownNode
}
t.mutex.Lock()
closest := t.closest(req.Target, bucketSize).entries
t.mutex.Unlock()
t.send(from, 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
}
if !t.handleReply(fromID, neighborsPacket, req) {
return errUnsolicitedReply
}
return nil
}
func expired(ts uint64) bool {
return time.Unix(int64(ts), 0).Before(time.Now())
}