p2p, p2p/discover: add signed ENR generation (#17753)

This PR adds enode.LocalNode and integrates it into the p2p
subsystem. This new object is the keeper of the local node
record. For now, a new version of the record is produced every
time the client restarts. We'll make it smarter to avoid that in
the future.

There are a couple of other changes in this commit: discovery now
waits for all of its goroutines at shutdown and the p2p server
now closes the node database after discovery has shut down. This
fixes a leveldb crash in tests. p2p server startup is faster
because it doesn't need to wait for the external IP query
anymore.

1 files changed, 246 insertions, 0 deletions

diff --git a/p2p/enode/localnode.go b/p2p/enode/localnode.go
new file mode 100644
index 000000000..623f8eae1
--- /dev/null
+++ b/p2p/enode/localnode.go
@@ -0,0 +1,246 @@
+// Copyright 2018 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 enode
+
+import (
+	"crypto/ecdsa"
+	"fmt"
+	"net"
+	"reflect"
+	"strconv"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/p2p/enr"
+	"github.com/ethereum/go-ethereum/p2p/netutil"
+)
+
+const (
+	// IP tracker configuration
+	iptrackMinStatements = 10
+	iptrackWindow        = 5 * time.Minute
+	iptrackContactWindow = 10 * time.Minute
+)
+
+// LocalNode produces the signed node record of a local node, i.e. a node run in the
+// current process. Setting ENR entries via the Set method updates the record. A new version
+// of the record is signed on demand when the Node method is called.
+type LocalNode struct {
+	cur atomic.Value // holds a non-nil node pointer while the record is up-to-date.
+	id  ID
+	key *ecdsa.PrivateKey
+	db  *DB
+
+	// everything below is protected by a lock
+	mu          sync.Mutex
+	seq         uint64
+	entries     map[string]enr.Entry
+	udpTrack    *netutil.IPTracker // predicts external UDP endpoint
+	staticIP    net.IP
+	fallbackIP  net.IP
+	fallbackUDP int
+}
+
+// NewLocalNode creates a local node.
+func NewLocalNode(db *DB, key *ecdsa.PrivateKey) *LocalNode {
+	ln := &LocalNode{
+		id:       PubkeyToIDV4(&key.PublicKey),
+		db:       db,
+		key:      key,
+		udpTrack: netutil.NewIPTracker(iptrackWindow, iptrackContactWindow, iptrackMinStatements),
+		entries:  make(map[string]enr.Entry),
+	}
+	ln.seq = db.localSeq(ln.id)
+	ln.invalidate()
+	return ln
+}
+
+// Database returns the node database associated with the local node.
+func (ln *LocalNode) Database() *DB {
+	return ln.db
+}
+
+// Node returns the current version of the local node record.
+func (ln *LocalNode) Node() *Node {
+	n := ln.cur.Load().(*Node)
+	if n != nil {
+		return n
+	}
+	// Record was invalidated, sign a new copy.
+	ln.mu.Lock()
+	defer ln.mu.Unlock()
+	ln.sign()
+	return ln.cur.Load().(*Node)
+}
+
+// ID returns the local node ID.
+func (ln *LocalNode) ID() ID {
+	return ln.id
+}
+
+// Set puts the given entry into the local record, overwriting
+// any existing value.
+func (ln *LocalNode) Set(e enr.Entry) {
+	ln.mu.Lock()
+	defer ln.mu.Unlock()
+
+	ln.set(e)
+}
+
+func (ln *LocalNode) set(e enr.Entry) {
+	val, exists := ln.entries[e.ENRKey()]
+	if !exists || !reflect.DeepEqual(val, e) {
+		ln.entries[e.ENRKey()] = e
+		ln.invalidate()
+	}
+}
+
+// Delete removes the given entry from the local record.
+func (ln *LocalNode) Delete(e enr.Entry) {
+	ln.mu.Lock()
+	defer ln.mu.Unlock()
+
+	ln.delete(e)
+}
+
+func (ln *LocalNode) delete(e enr.Entry) {
+	_, exists := ln.entries[e.ENRKey()]
+	if exists {
+		delete(ln.entries, e.ENRKey())
+		ln.invalidate()
+	}
+}
+
+// SetStaticIP sets the local IP to the given one unconditionally.
+// This disables endpoint prediction.
+func (ln *LocalNode) SetStaticIP(ip net.IP) {
+	ln.mu.Lock()
+	defer ln.mu.Unlock()
+
+	ln.staticIP = ip
+	ln.updateEndpoints()
+}
+
+// SetFallbackIP sets the last-resort IP address. This address is used
+// if no endpoint prediction can be made and no static IP is set.
+func (ln *LocalNode) SetFallbackIP(ip net.IP) {
+	ln.mu.Lock()
+	defer ln.mu.Unlock()
+
+	ln.fallbackIP = ip
+	ln.updateEndpoints()
+}
+
+// SetFallbackUDP sets the last-resort UDP port. This port is used
+// if no endpoint prediction can be made.
+func (ln *LocalNode) SetFallbackUDP(port int) {
+	ln.mu.Lock()
+	defer ln.mu.Unlock()
+
+	ln.fallbackUDP = port
+	ln.updateEndpoints()
+}
+
+// UDPEndpointStatement should be called whenever a statement about the local node's
+// UDP endpoint is received. It feeds the local endpoint predictor.
+func (ln *LocalNode) UDPEndpointStatement(fromaddr, endpoint *net.UDPAddr) {
+	ln.mu.Lock()
+	defer ln.mu.Unlock()
+
+	ln.udpTrack.AddStatement(fromaddr.String(), endpoint.String())
+	ln.updateEndpoints()
+}
+
+// UDPContact should be called whenever the local node has announced itself to another node
+// via UDP. It feeds the local endpoint predictor.
+func (ln *LocalNode) UDPContact(toaddr *net.UDPAddr) {
+	ln.mu.Lock()
+	defer ln.mu.Unlock()
+
+	ln.udpTrack.AddContact(toaddr.String())
+	ln.updateEndpoints()
+}
+
+func (ln *LocalNode) updateEndpoints() {
+	// Determine the endpoints.
+	newIP := ln.fallbackIP
+	newUDP := ln.fallbackUDP
+	if ln.staticIP != nil {
+		newIP = ln.staticIP
+	} else if ip, port := predictAddr(ln.udpTrack); ip != nil {
+		newIP = ip
+		newUDP = port
+	}
+
+	// Update the record.
+	if newIP != nil && !newIP.IsUnspecified() {
+		ln.set(enr.IP(newIP))
+		if newUDP != 0 {
+			ln.set(enr.UDP(newUDP))
+		} else {
+			ln.delete(enr.UDP(0))
+		}
+	} else {
+		ln.delete(enr.IP{})
+	}
+}
+
+// predictAddr wraps IPTracker.PredictEndpoint, converting from its string-based
+// endpoint representation to IP and port types.
+func predictAddr(t *netutil.IPTracker) (net.IP, int) {
+	ep := t.PredictEndpoint()
+	if ep == "" {
+		return nil, 0
+	}
+	ipString, portString, _ := net.SplitHostPort(ep)
+	ip := net.ParseIP(ipString)
+	port, _ := strconv.Atoi(portString)
+	return ip, port
+}
+
+func (ln *LocalNode) invalidate() {
+	ln.cur.Store((*Node)(nil))
+}
+
+func (ln *LocalNode) sign() {
+	if n := ln.cur.Load().(*Node); n != nil {
+		return // no changes
+	}
+
+	var r enr.Record
+	for _, e := range ln.entries {
+		r.Set(e)
+	}
+	ln.bumpSeq()
+	r.SetSeq(ln.seq)
+	if err := SignV4(&r, ln.key); err != nil {
+		panic(fmt.Errorf("enode: can't sign record: %v", err))
+	}
+	n, err := New(ValidSchemes, &r)
+	if err != nil {
+		panic(fmt.Errorf("enode: can't verify local record: %v", err))
+	}
+	ln.cur.Store(n)
+	log.Info("New local node record", "seq", ln.seq, "id", n.ID(), "ip", n.IP(), "udp", n.UDP(), "tcp", n.TCP())
+}
+
+func (ln *LocalNode) bumpSeq() {
+	ln.seq++
+	ln.db.storeLocalSeq(ln.id, ln.seq)
+}