b4374436f3
nodeDB.querySeeds was not safe for concurrent use but could be called concurrenty on multiple goroutines in the following case: - the table was empty - a timed refresh started - a lookup was started and initiated refresh These conditions are unlikely to coincide during normal use, but are much more likely to occur all at once when the user's machine just woke from sleep. The root cause of the issue is that querySeeds reused the same leveldb iterator until it was exhausted. This commit moves the refresh scheduling logic into its own goroutine (so only one refresh is ever active) and changes querySeeds to not use a persistent iterator. The seed node selection is now more random and ignores nodes that have not been contacted in the last 5 days.
595 lines
16 KiB
Go
595 lines
16 KiB
Go
// Copyright 2015 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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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
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// 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
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package discover
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import (
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"bytes"
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"container/list"
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"crypto/ecdsa"
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"errors"
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"fmt"
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"net"
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"time"
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"github.com/ethereum/go-ethereum/crypto"
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"github.com/ethereum/go-ethereum/logger"
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"github.com/ethereum/go-ethereum/logger/glog"
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"github.com/ethereum/go-ethereum/p2p/nat"
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"github.com/ethereum/go-ethereum/rlp"
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)
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const Version = 4
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// Errors
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var (
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errPacketTooSmall = errors.New("too small")
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errBadHash = errors.New("bad hash")
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errExpired = errors.New("expired")
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errBadVersion = errors.New("version mismatch")
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errUnsolicitedReply = errors.New("unsolicited reply")
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errUnknownNode = errors.New("unknown node")
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errTimeout = errors.New("RPC timeout")
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errClockWarp = errors.New("reply deadline too far in the future")
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errClosed = errors.New("socket closed")
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)
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// Timeouts
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const (
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respTimeout = 500 * time.Millisecond
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sendTimeout = 500 * time.Millisecond
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expiration = 20 * time.Second
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)
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// RPC packet types
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const (
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pingPacket = iota + 1 // zero is 'reserved'
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pongPacket
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findnodePacket
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neighborsPacket
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)
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// RPC request structures
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type (
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ping struct {
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Version uint
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From, To rpcEndpoint
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Expiration uint64
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}
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// pong is the reply to ping.
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pong struct {
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// This field should mirror the UDP envelope address
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// of the ping packet, which provides a way to discover the
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// the external address (after NAT).
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To rpcEndpoint
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ReplyTok []byte // This contains the hash of the ping packet.
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Expiration uint64 // Absolute timestamp at which the packet becomes invalid.
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}
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// findnode is a query for nodes close to the given target.
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findnode struct {
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Target NodeID // doesn't need to be an actual public key
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Expiration uint64
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}
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// reply to findnode
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neighbors struct {
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Nodes []rpcNode
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Expiration uint64
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}
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rpcNode struct {
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IP net.IP // len 4 for IPv4 or 16 for IPv6
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UDP uint16 // for discovery protocol
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TCP uint16 // for RLPx protocol
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ID NodeID
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}
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rpcEndpoint struct {
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IP net.IP // len 4 for IPv4 or 16 for IPv6
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UDP uint16 // for discovery protocol
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TCP uint16 // for RLPx protocol
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}
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)
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func makeEndpoint(addr *net.UDPAddr, tcpPort uint16) rpcEndpoint {
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ip := addr.IP.To4()
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if ip == nil {
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ip = addr.IP.To16()
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}
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return rpcEndpoint{IP: ip, UDP: uint16(addr.Port), TCP: tcpPort}
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}
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func nodeFromRPC(rn rpcNode) (n *Node, valid bool) {
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// TODO: don't accept localhost, LAN addresses from internet hosts
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// TODO: check public key is on secp256k1 curve
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if rn.IP.IsMulticast() || rn.IP.IsUnspecified() || rn.UDP == 0 {
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return nil, false
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}
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return newNode(rn.ID, rn.IP, rn.UDP, rn.TCP), true
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}
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func nodeToRPC(n *Node) rpcNode {
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return rpcNode{ID: n.ID, IP: n.IP, UDP: n.UDP, TCP: n.TCP}
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}
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type packet interface {
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handle(t *udp, from *net.UDPAddr, fromID NodeID, mac []byte) error
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}
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type conn interface {
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ReadFromUDP(b []byte) (n int, addr *net.UDPAddr, err error)
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WriteToUDP(b []byte, addr *net.UDPAddr) (n int, err error)
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Close() error
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LocalAddr() net.Addr
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}
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// udp implements the RPC protocol.
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type udp struct {
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conn conn
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priv *ecdsa.PrivateKey
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ourEndpoint rpcEndpoint
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addpending chan *pending
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gotreply chan reply
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closing chan struct{}
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nat nat.Interface
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*Table
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}
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// pending represents a pending reply.
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//
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// some implementations of the protocol wish to send more than one
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// reply packet to findnode. in general, any neighbors packet cannot
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// be matched up with a specific findnode packet.
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//
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// our implementation handles this by storing a callback function for
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// each pending reply. incoming packets from a node are dispatched
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// to all the callback functions for that node.
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type pending struct {
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// these fields must match in the reply.
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from NodeID
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ptype byte
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// time when the request must complete
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deadline time.Time
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// callback is called when a matching reply arrives. if it returns
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// true, the callback is removed from the pending reply queue.
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// if it returns false, the reply is considered incomplete and
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// the callback will be invoked again for the next matching reply.
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callback func(resp interface{}) (done bool)
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// errc receives nil when the callback indicates completion or an
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// error if no further reply is received within the timeout.
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errc chan<- error
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}
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type reply struct {
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from NodeID
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ptype byte
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data interface{}
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// loop indicates whether there was
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// a matching request by sending on this channel.
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matched chan<- bool
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}
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// ListenUDP returns a new table that listens for UDP packets on laddr.
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func ListenUDP(priv *ecdsa.PrivateKey, laddr string, natm nat.Interface, nodeDBPath string) (*Table, error) {
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addr, err := net.ResolveUDPAddr("udp", laddr)
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if err != nil {
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return nil, err
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}
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conn, err := net.ListenUDP("udp", addr)
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if err != nil {
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return nil, err
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}
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tab, _ := newUDP(priv, conn, natm, nodeDBPath)
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glog.V(logger.Info).Infoln("Listening,", tab.self)
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return tab, nil
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}
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func newUDP(priv *ecdsa.PrivateKey, c conn, natm nat.Interface, nodeDBPath string) (*Table, *udp) {
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udp := &udp{
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conn: c,
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priv: priv,
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closing: make(chan struct{}),
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gotreply: make(chan reply),
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addpending: make(chan *pending),
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}
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realaddr := c.LocalAddr().(*net.UDPAddr)
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if natm != nil {
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if !realaddr.IP.IsLoopback() {
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go nat.Map(natm, udp.closing, "udp", realaddr.Port, realaddr.Port, "ethereum discovery")
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}
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// TODO: react to external IP changes over time.
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if ext, err := natm.ExternalIP(); err == nil {
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realaddr = &net.UDPAddr{IP: ext, Port: realaddr.Port}
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}
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}
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// TODO: separate TCP port
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udp.ourEndpoint = makeEndpoint(realaddr, uint16(realaddr.Port))
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udp.Table = newTable(udp, PubkeyID(&priv.PublicKey), realaddr, nodeDBPath)
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go udp.loop()
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go udp.readLoop()
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return udp.Table, udp
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}
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func (t *udp) close() {
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close(t.closing)
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t.conn.Close()
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// TODO: wait for the loops to end.
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}
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// ping sends a ping message to the given node and waits for a reply.
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func (t *udp) ping(toid NodeID, toaddr *net.UDPAddr) error {
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// TODO: maybe check for ReplyTo field in callback to measure RTT
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errc := t.pending(toid, pongPacket, func(interface{}) bool { return true })
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t.send(toaddr, pingPacket, ping{
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Version: Version,
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From: t.ourEndpoint,
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To: makeEndpoint(toaddr, 0), // TODO: maybe use known TCP port from DB
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Expiration: uint64(time.Now().Add(expiration).Unix()),
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})
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return <-errc
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}
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func (t *udp) waitping(from NodeID) error {
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return <-t.pending(from, pingPacket, func(interface{}) bool { return true })
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}
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// findnode sends a findnode request to the given node and waits until
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// the node has sent up to k neighbors.
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func (t *udp) findnode(toid NodeID, toaddr *net.UDPAddr, target NodeID) ([]*Node, error) {
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nodes := make([]*Node, 0, bucketSize)
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nreceived := 0
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errc := t.pending(toid, neighborsPacket, func(r interface{}) bool {
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reply := r.(*neighbors)
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for _, rn := range reply.Nodes {
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nreceived++
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if n, valid := nodeFromRPC(rn); valid {
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nodes = append(nodes, n)
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}
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}
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return nreceived >= bucketSize
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})
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t.send(toaddr, findnodePacket, findnode{
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Target: target,
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Expiration: uint64(time.Now().Add(expiration).Unix()),
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})
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err := <-errc
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return nodes, err
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}
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// pending adds a reply callback to the pending reply queue.
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// see the documentation of type pending for a detailed explanation.
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func (t *udp) pending(id NodeID, ptype byte, callback func(interface{}) bool) <-chan error {
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ch := make(chan error, 1)
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p := &pending{from: id, ptype: ptype, callback: callback, errc: ch}
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select {
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case t.addpending <- p:
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// loop will handle it
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case <-t.closing:
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ch <- errClosed
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}
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return ch
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}
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func (t *udp) handleReply(from NodeID, ptype byte, req packet) bool {
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matched := make(chan bool, 1)
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select {
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case t.gotreply <- reply{from, ptype, req, matched}:
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// loop will handle it
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return <-matched
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case <-t.closing:
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return false
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}
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}
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// loop runs in its own goroutin. it keeps track of
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// the refresh timer and the pending reply queue.
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func (t *udp) loop() {
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var (
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plist = list.New()
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timeout = time.NewTimer(0)
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nextTimeout *pending // head of plist when timeout was last reset
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)
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<-timeout.C // ignore first timeout
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defer timeout.Stop()
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resetTimeout := func() {
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if plist.Front() == nil || nextTimeout == plist.Front().Value {
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return
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}
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// Start the timer so it fires when the next pending reply has expired.
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now := time.Now()
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for el := plist.Front(); el != nil; el = el.Next() {
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nextTimeout = el.Value.(*pending)
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if dist := nextTimeout.deadline.Sub(now); dist < 2*respTimeout {
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timeout.Reset(dist)
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return
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}
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// Remove pending replies whose deadline is too far in the
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// future. These can occur if the system clock jumped
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// backwards after the deadline was assigned.
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nextTimeout.errc <- errClockWarp
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plist.Remove(el)
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}
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nextTimeout = nil
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timeout.Stop()
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}
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for {
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resetTimeout()
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select {
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case <-t.closing:
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for el := plist.Front(); el != nil; el = el.Next() {
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el.Value.(*pending).errc <- errClosed
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}
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return
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case p := <-t.addpending:
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p.deadline = time.Now().Add(respTimeout)
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plist.PushBack(p)
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case r := <-t.gotreply:
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var matched bool
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for el := plist.Front(); el != nil; el = el.Next() {
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p := el.Value.(*pending)
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if p.from == r.from && p.ptype == r.ptype {
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matched = true
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// Remove the matcher if its callback indicates
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// that all replies have been received. This is
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// required for packet types that expect multiple
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// reply packets.
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if p.callback(r.data) {
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p.errc <- nil
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plist.Remove(el)
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}
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}
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}
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r.matched <- matched
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case now := <-timeout.C:
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nextTimeout = nil
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// Notify and remove callbacks whose deadline is in the past.
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for el := plist.Front(); el != nil; el = el.Next() {
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p := el.Value.(*pending)
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if now.After(p.deadline) || now.Equal(p.deadline) {
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p.errc <- errTimeout
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plist.Remove(el)
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}
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}
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}
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}
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}
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const (
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macSize = 256 / 8
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sigSize = 520 / 8
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headSize = macSize + sigSize // space of packet frame data
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)
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var (
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headSpace = make([]byte, headSize)
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// Neighbors replies are sent across multiple packets to
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// stay below the 1280 byte limit. We compute the maximum number
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// of entries by stuffing a packet until it grows too large.
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maxNeighbors int
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)
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func init() {
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p := neighbors{Expiration: ^uint64(0)}
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maxSizeNode := rpcNode{IP: make(net.IP, 16), UDP: ^uint16(0), TCP: ^uint16(0)}
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for n := 0; ; n++ {
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p.Nodes = append(p.Nodes, maxSizeNode)
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size, _, err := rlp.EncodeToReader(p)
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if err != nil {
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// If this ever happens, it will be caught by the unit tests.
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panic("cannot encode: " + err.Error())
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}
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if headSize+size+1 >= 1280 {
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maxNeighbors = n
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break
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}
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}
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}
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func (t *udp) send(toaddr *net.UDPAddr, ptype byte, req interface{}) error {
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packet, err := encodePacket(t.priv, ptype, req)
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if err != nil {
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return err
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}
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glog.V(logger.Detail).Infof(">>> %v %T\n", toaddr, req)
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if _, err = t.conn.WriteToUDP(packet, toaddr); err != nil {
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glog.V(logger.Detail).Infoln("UDP send failed:", err)
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}
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return err
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}
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func encodePacket(priv *ecdsa.PrivateKey, ptype byte, req interface{}) ([]byte, error) {
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b := new(bytes.Buffer)
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b.Write(headSpace)
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b.WriteByte(ptype)
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if err := rlp.Encode(b, req); err != nil {
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glog.V(logger.Error).Infoln("error encoding packet:", err)
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return nil, err
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}
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packet := b.Bytes()
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sig, err := crypto.Sign(crypto.Sha3(packet[headSize:]), priv)
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if err != nil {
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glog.V(logger.Error).Infoln("could not sign packet:", err)
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return nil, err
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}
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copy(packet[macSize:], sig)
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// add the hash to the front. Note: this doesn't protect the
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// packet in any way. Our public key will be part of this hash in
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// The future.
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copy(packet, crypto.Sha3(packet[macSize:]))
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return packet, nil
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}
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type tempError interface {
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Temporary() bool
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}
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|
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// readLoop runs in its own goroutine. it handles incoming UDP packets.
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func (t *udp) readLoop() {
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defer t.conn.Close()
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// Discovery packets are defined to be no larger than 1280 bytes.
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// Packets larger than this size will be cut at the end and treated
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// as invalid because their hash won't match.
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buf := make([]byte, 1280)
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for {
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nbytes, from, err := t.conn.ReadFromUDP(buf)
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if tempErr, ok := err.(tempError); ok && tempErr.Temporary() {
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// Ignore temporary read errors.
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glog.V(logger.Debug).Infof("Temporary read error: %v", err)
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continue
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} else if err != nil {
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// Shut down the loop for permament errors.
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glog.V(logger.Debug).Infof("Read error: %v", err)
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return
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}
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t.handlePacket(from, buf[:nbytes])
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}
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}
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|
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func (t *udp) handlePacket(from *net.UDPAddr, buf []byte) error {
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packet, fromID, hash, err := decodePacket(buf)
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if err != nil {
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glog.V(logger.Debug).Infof("Bad packet from %v: %v\n", from, err)
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return err
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}
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status := "ok"
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if err = packet.handle(t, from, fromID, hash); err != nil {
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status = err.Error()
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}
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glog.V(logger.Detail).Infof("<<< %v %T: %s\n", from, packet, status)
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return err
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}
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|
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func decodePacket(buf []byte) (packet, NodeID, []byte, error) {
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if len(buf) < headSize+1 {
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return nil, NodeID{}, nil, errPacketTooSmall
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}
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hash, sig, sigdata := buf[:macSize], buf[macSize:headSize], buf[headSize:]
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shouldhash := crypto.Sha3(buf[macSize:])
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if !bytes.Equal(hash, shouldhash) {
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return nil, NodeID{}, nil, errBadHash
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}
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fromID, err := recoverNodeID(crypto.Sha3(buf[headSize:]), sig)
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if err != nil {
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return nil, NodeID{}, hash, err
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}
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var req packet
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switch ptype := sigdata[0]; ptype {
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case pingPacket:
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req = new(ping)
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case pongPacket:
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req = new(pong)
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case findnodePacket:
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req = new(findnode)
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case neighborsPacket:
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req = new(neighbors)
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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
|
|
}
|
|
target := crypto.Sha3Hash(req.Target[:])
|
|
t.mutex.Lock()
|
|
closest := t.closest(target, bucketSize).entries
|
|
t.mutex.Unlock()
|
|
|
|
p := neighbors{Expiration: uint64(time.Now().Add(expiration).Unix())}
|
|
// Send neighbors in chunks with at most maxNeighbors per packet
|
|
// to stay below the 1280 byte limit.
|
|
for i, n := range closest {
|
|
p.Nodes = append(p.Nodes, nodeToRPC(n))
|
|
if len(p.Nodes) == maxNeighbors || i == len(closest)-1 {
|
|
t.send(from, neighborsPacket, p)
|
|
p.Nodes = p.Nodes[:0]
|
|
}
|
|
}
|
|
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())
|
|
}
|