syncthing/cmd/stdiscosrv/replication.go
2024-06-03 19:50:28 +02:00

326 lines
8.1 KiB
Go

// Copyright (C) 2018 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
package main
import (
"context"
"crypto/tls"
"encoding/binary"
"fmt"
io "io"
"log"
"net"
"time"
"github.com/syncthing/syncthing/lib/protocol"
)
const (
replicationReadTimeout = time.Minute
replicationWriteTimeout = 30 * time.Second
replicationHeartbeatInterval = time.Second * 30
)
type replicator interface {
send(key string, addrs []DatabaseAddress, seen int64)
}
// a replicationSender tries to connect to the remote address and provide
// them with a feed of replication updates.
type replicationSender struct {
dst string
cert tls.Certificate // our certificate
allowedIDs []protocol.DeviceID
outbox chan ReplicationRecord
}
func newReplicationSender(dst string, cert tls.Certificate, allowedIDs []protocol.DeviceID) *replicationSender {
return &replicationSender{
dst: dst,
cert: cert,
allowedIDs: allowedIDs,
outbox: make(chan ReplicationRecord, replicationOutboxSize),
}
}
func (s *replicationSender) Serve(ctx context.Context) error {
// Sleep a little at startup. Peers often restart at the same time, and
// this avoid the service failing and entering backoff state
// unnecessarily, while also reducing the reconnect rate to something
// reasonable by default.
time.Sleep(2 * time.Second)
tlsCfg := &tls.Config{
Certificates: []tls.Certificate{s.cert},
MinVersion: tls.VersionTLS12,
InsecureSkipVerify: true,
}
// Dial the TLS connection.
conn, err := tls.Dial("tcp", s.dst, tlsCfg)
if err != nil {
log.Println("Replication connect:", err)
return err
}
defer func() {
conn.SetWriteDeadline(time.Now().Add(time.Second))
conn.Close()
}()
// The replication stream is not especially latency sensitive, but it is
// quite a lot of data in small writes. Make it more efficient.
if tcpc, ok := conn.NetConn().(*net.TCPConn); ok {
_ = tcpc.SetNoDelay(false)
}
// Get the other side device ID.
remoteID, err := deviceID(conn)
if err != nil {
log.Println("Replication connect:", err)
return err
}
// Verify it's in the set of allowed device IDs.
if !deviceIDIn(remoteID, s.allowedIDs) {
log.Println("Replication connect: unexpected device ID:", remoteID)
return err
}
heartBeatTicker := time.NewTicker(replicationHeartbeatInterval)
defer heartBeatTicker.Stop()
// Send records.
buf := make([]byte, 1024)
for {
select {
case <-heartBeatTicker.C:
if len(s.outbox) > 0 {
// No need to send heartbeats if there are events/prevrious
// heartbeats to send, they will keep the connection alive.
continue
}
// Empty replication message is the heartbeat:
s.outbox <- ReplicationRecord{}
case rec := <-s.outbox:
// Buffer must hold record plus four bytes for size
size := rec.Size()
if len(buf) < size+4 {
buf = make([]byte, size+4)
}
// Record comes after the four bytes size
n, err := rec.MarshalTo(buf[4:])
if err != nil {
// odd to get an error here, but we haven't sent anything
// yet so it's not fatal
replicationSendsTotal.WithLabelValues("error").Inc()
log.Println("Replication marshal:", err)
continue
}
binary.BigEndian.PutUint32(buf, uint32(n))
// Send
conn.SetWriteDeadline(time.Now().Add(replicationWriteTimeout))
if _, err := conn.Write(buf[:4+n]); err != nil {
replicationSendsTotal.WithLabelValues("error").Inc()
log.Println("Replication write:", err)
// Yes, we are losing the replication event here.
return err
}
replicationSendsTotal.WithLabelValues("success").Inc()
case <-ctx.Done():
return nil
}
}
}
func (s *replicationSender) String() string {
return fmt.Sprintf("replicationSender(%q)", s.dst)
}
func (s *replicationSender) send(key string, ps []DatabaseAddress, seen int64) {
item := ReplicationRecord{
Key: key,
Addresses: ps,
Seen: seen,
}
// The send should never block. The inbox is suitably buffered for at
// least a few seconds of stalls, which shouldn't happen in practice.
select {
case s.outbox <- item:
default:
replicationSendsTotal.WithLabelValues("drop").Inc()
}
}
// a replicationMultiplexer sends to multiple replicators
type replicationMultiplexer []replicator
func (m replicationMultiplexer) send(key string, ps []DatabaseAddress, seen int64) {
for _, s := range m {
// each send is nonblocking
s.send(key, ps, seen)
}
}
// replicationListener accepts incoming connections and reads replication
// items from them. Incoming items are applied to the KV store.
type replicationListener struct {
addr string
cert tls.Certificate
allowedIDs []protocol.DeviceID
db database
}
func newReplicationListener(addr string, cert tls.Certificate, allowedIDs []protocol.DeviceID, db database) *replicationListener {
return &replicationListener{
addr: addr,
cert: cert,
allowedIDs: allowedIDs,
db: db,
}
}
func (l *replicationListener) Serve(ctx context.Context) error {
tlsCfg := &tls.Config{
Certificates: []tls.Certificate{l.cert},
ClientAuth: tls.RequestClientCert,
MinVersion: tls.VersionTLS12,
InsecureSkipVerify: true,
}
lst, err := tls.Listen("tcp", l.addr, tlsCfg)
if err != nil {
log.Println("Replication listen:", err)
return err
}
defer lst.Close()
for {
select {
case <-ctx.Done():
return nil
default:
}
// Accept a connection
conn, err := lst.Accept()
if err != nil {
log.Println("Replication accept:", err)
return err
}
// Figure out the other side device ID
remoteID, err := deviceID(conn.(*tls.Conn))
if err != nil {
log.Println("Replication accept:", err)
conn.SetWriteDeadline(time.Now().Add(time.Second))
conn.Close()
continue
}
// Verify it is in the set of allowed device IDs
if !deviceIDIn(remoteID, l.allowedIDs) {
log.Println("Replication accept: unexpected device ID:", remoteID)
conn.SetWriteDeadline(time.Now().Add(time.Second))
conn.Close()
continue
}
go l.handle(ctx, conn)
}
}
func (l *replicationListener) String() string {
return fmt.Sprintf("replicationListener(%q)", l.addr)
}
func (l *replicationListener) handle(ctx context.Context, conn net.Conn) {
defer func() {
conn.SetWriteDeadline(time.Now().Add(time.Second))
conn.Close()
}()
buf := make([]byte, 1024)
for {
select {
case <-ctx.Done():
return
default:
}
conn.SetReadDeadline(time.Now().Add(replicationReadTimeout))
// First four bytes are the size
if _, err := io.ReadFull(conn, buf[:4]); err != nil {
log.Println("Replication read size:", err)
replicationRecvsTotal.WithLabelValues("error").Inc()
return
}
// Read the rest of the record
size := int(binary.BigEndian.Uint32(buf[:4]))
if len(buf) < size {
buf = make([]byte, size)
}
if size == 0 {
// Heartbeat, ignore
continue
}
if _, err := io.ReadFull(conn, buf[:size]); err != nil {
log.Println("Replication read record:", err)
replicationRecvsTotal.WithLabelValues("error").Inc()
return
}
// Unmarshal
var rec ReplicationRecord
if err := rec.Unmarshal(buf[:size]); err != nil {
log.Println("Replication unmarshal:", err)
replicationRecvsTotal.WithLabelValues("error").Inc()
continue
}
// Store
l.db.merge(rec.Key, rec.Addresses, rec.Seen)
replicationRecvsTotal.WithLabelValues("success").Inc()
}
}
func deviceID(conn *tls.Conn) (protocol.DeviceID, error) {
// Handshake may not be complete on the server side yet, which we need
// to get the client certificate.
if !conn.ConnectionState().HandshakeComplete {
if err := conn.Handshake(); err != nil {
return protocol.DeviceID{}, err
}
}
// We expect exactly one certificate.
certs := conn.ConnectionState().PeerCertificates
if len(certs) != 1 {
return protocol.DeviceID{}, fmt.Errorf("unexpected number of certificates (%d != 1)", len(certs))
}
return protocol.NewDeviceID(certs[0].Raw), nil
}
func deviceIDIn(id protocol.DeviceID, ids []protocol.DeviceID) bool {
for _, candidate := range ids {
if id == candidate {
return true
}
}
return false
}