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protocol.go
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/
protocol.go
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// Copyright 2017 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 protocols is an extension to p2p. It offers a user friendly simple way to define
devp2p subprotocols by abstracting away code standardly shared by protocols.
* automate assignments of code indexes to messages
* automate RLP decoding/encoding based on reflecting
* provide the forever loop to read incoming messages
* standardise error handling related to communication
* standardised handshake negotiation
* TODO: automatic generation of wire protocol specification for peers
*/
package protocols
import (
"context"
"errors"
"fmt"
"io"
"reflect"
"strings"
"sync"
"time"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/metrics"
"github.com/ethereum/go-ethereum/p2p"
"github.com/ethereum/go-ethereum/rlp"
"github.com/ethersphere/swarm/tracing"
)
// MsgPauser can be used to pause run execution
// IMPORTANT: should be used only for tests
type MsgPauser interface {
Pause()
Resume()
Wait()
}
//For accounting, the design is to allow the Spec to describe which and how its messages are priced
//To access this functionality, we provide a Hook interface which will call accounting methods
//NOTE: there could be more such (horizontal) hooks in the future
type Hook interface {
// A hook for applying accounting
Apply(peer *Peer, costToLocalNode int64, size uint32) error
// Run some validation before applying accounting
Validate(peer *Peer, size uint32, msg interface{}, payer Payer) (int64, error)
}
// Spec is a protocol specification including its name and version as well as
// the types of messages which are exchanged
type Spec struct {
// Name is the name of the protocol, often a three-letter word
Name string
// Version is the version number of the protocol
Version uint
// MaxMsgSize is the maximum accepted length of the message payload
MaxMsgSize uint32
// Messages is a list of message data types which this protocol uses, with
// each message type being sent with its array index as the code (so
// [&foo{}, &bar{}, &baz{}] would send foo, bar and baz with codes
// 0, 1 and 2 respectively)
// each message must have a single unique data type
Messages []interface{}
//hook for accounting (could be extended to multiple hooks in the future)
Hook Hook
initOnce sync.Once
codes map[reflect.Type]uint64
types map[uint64]reflect.Type
// if the protocol does not allow extending the p2p msg to propagate context
// even if context not disabled, context will propagate only tracing is enabled
DisableContext bool
}
func (s *Spec) init() {
s.initOnce.Do(func() {
s.codes = make(map[reflect.Type]uint64, len(s.Messages))
s.types = make(map[uint64]reflect.Type, len(s.Messages))
for i, msg := range s.Messages {
code := uint64(i)
typ := reflect.TypeOf(msg)
if typ.Kind() == reflect.Ptr {
typ = typ.Elem()
}
s.codes[typ] = code
s.types[code] = typ
}
})
}
// Length returns the number of message types in the protocol
func (s *Spec) Length() uint64 {
return uint64(len(s.Messages))
}
// GetCode returns the message code of a type, and boolean second argument is
// false if the message type is not found
func (s *Spec) GetCode(msg interface{}) (uint64, bool) {
s.init()
typ := reflect.TypeOf(msg)
if typ.Kind() == reflect.Ptr {
typ = typ.Elem()
}
code, ok := s.codes[typ]
return code, ok
}
// NewMsg construct a new message type given the code
func (s *Spec) NewMsg(code uint64) (interface{}, bool) {
s.init()
typ, ok := s.types[code]
if !ok {
return nil, false
}
return reflect.New(typ).Interface(), true
}
// Peer represents a remote peer or protocol instance that is running on a peer connection with
// a remote peer
type Peer struct {
*p2p.Peer // the p2p.Peer object representing the remote
rw p2p.MsgReadWriter // p2p.MsgReadWriter to send messages to and read messages from
spec *Spec
encode func(context.Context, interface{}) (interface{}, int, error)
decode func(p2p.Msg) (context.Context, []byte, error)
wg sync.WaitGroup
running bool // if running is true async go routines are dispatched in the event loop
mtx sync.RWMutex // guards running
handleMsgPauser MsgPauser // message pauser, should be used only in tests
}
// NewPeer constructs a new peer
// this constructor is called by the p2p.Protocol#Run function
// the first two arguments are the arguments passed to p2p.Protocol.Run function
// the third argument is the Spec describing the protocol
func NewPeer(peer *p2p.Peer, rw p2p.MsgReadWriter, spec *Spec) *Peer {
encode := encodeWithContext
decode := decodeWithContext
if spec == nil || spec.DisableContext || !tracing.Enabled {
encode = encodeWithoutContext
decode = decodeWithoutContext
}
return &Peer{
Peer: peer,
rw: rw,
spec: spec,
encode: encode,
decode: decode,
}
}
// Run starts the forever loop that handles incoming messages.
// The handler argument is a function which is called for each message received
// from the remote peer, a returned error causes the loop to exit
// resulting in disconnection of the protocol
func (p *Peer) Run(handler func(ctx context.Context, msg interface{}) error) error {
if err := p.run(handler); err != nil && err != io.EOF {
return err
}
return nil
}
// run receives messages from the peer and dispatches async routines to handle the messages
func (p *Peer) run(handler func(ctx context.Context, msg interface{}) error) error {
p.mtx.Lock()
p.running = true
p.mtx.Unlock()
for {
msg, err := p.readMsg()
if err != nil {
return err
}
p.mtx.RLock()
// if loop has been stopped, we don't dispatch any more async routines and discard (consume) the message
if !p.running {
_ = msg.Discard()
p.mtx.RUnlock()
continue
}
p.mtx.RUnlock()
// handleMsgPauser should not be nil only in tests.
// It does not use mutex lock protection and because of that
// it must be set before the Registry is constructed and
// reset when it is closed, in tests.
// Production performance impact can be considered as
// neglectable as nil check is a ns order operation.
if p.handleMsgPauser != nil {
p.handleMsgPauser.Wait()
}
p.wg.Add(1)
go func() {
defer p.wg.Done()
err := p.handleMsg(msg, handler)
if err != nil {
var e *breakError
if errors.As(err, &e) {
p.Drop(err.Error())
} else {
log.Trace(err.Error())
}
}
}()
}
}
func (p *Peer) readMsg() (p2p.Msg, error) {
msg, err := p.rw.ReadMsg()
if err != nil {
if err != io.EOF {
metrics.GetOrRegisterCounter("peer/readMsg/error", nil).Inc(1)
return msg, fmt.Errorf("peer.readMsg, err: %w", err)
}
}
return msg, err
}
// Drop disconnects a peer
// TODO: may need to implement protocol drop only? don't want to kick off the peer
func (p *Peer) Drop(reason string) {
log.Error("dropping peer with DiscSubprotocolError", "peer", p.ID(), "reason", reason)
p.Disconnect(p2p.DiscSubprotocolError)
}
// Stop stops the execution of new async jobs, and blocks until active jobs are finished or provided timeout passes.
// Returns nil if the active jobs are finished within the timeout duration, or error otherwise.
func (p *Peer) Stop(timeout time.Duration) error {
p.mtx.Lock()
if !p.running {
return nil
}
p.running = false
p.mtx.Unlock()
done := make(chan bool)
go func() {
p.wg.Wait()
close(done)
}()
select {
case <-done:
case <-time.After(timeout):
log.Debug("peer shutdown with still active handlers: {}", p)
return errors.New("shutdown timeout reached")
}
return nil
}
// Send takes a message, encodes it in RLP, finds the right message code and sends the
// message off to the peer
// this low level call will be wrapped by libraries providing routed or broadcast sends
// but often just used to forward and push messages to directly connected peers
func (p *Peer) Send(ctx context.Context, msg interface{}) error {
defer metrics.GetOrRegisterResettingTimer("peer/send_t", nil).UpdateSince(time.Now())
metrics.GetOrRegisterCounter("peer/send", nil).Inc(1)
metrics.GetOrRegisterCounter(strings.ReplaceAll(fmt.Sprintf("peer/send/%T", msg), ".", "/"), nil).Inc(1)
code, found := p.spec.GetCode(msg)
if !found {
return fmt.Errorf("invalid message type %v ", code)
}
wmsg, size, err := p.encode(ctx, msg)
if err != nil {
return err
}
// if size is not set by the wrapper, need to serialise
if size == 0 {
r, err := rlp.EncodeToBytes(msg)
if err != nil {
return err
}
size = len(r)
}
// if the accounting hook is set, do accounting logic
if p.spec.Hook != nil {
// validate that this operation would succeed...
costToLocalNode, err := p.spec.Hook.Validate(p, uint32(size), wmsg, Sender)
if err != nil {
// ...because if it would fail, we return and don't send the message
return err
}
// seems like accounting would succeed, thus send the message first...
err = p2p.Send(p.rw, code, wmsg)
if err != nil {
return err
}
// ...and finally apply (write) the accounting change
if err := p.spec.Hook.Apply(p, costToLocalNode, uint32(size)); err != nil {
return err
}
} else {
err = p2p.Send(p.rw, code, wmsg)
}
return nil
}
// SetMsgPauser sets message pauser for this peer
// IMPORTANT: to be used only for testing
func (p *Peer) SetMsgPauser(pauser MsgPauser) {
p.handleMsgPauser = pauser
}
// receive is a sync call that handles incoming message with provided message handler
func (p *Peer) receive(handler func(ctx context.Context, msg interface{}) error) error {
msg, err := p.readMsg()
if err != nil {
return err
}
return p.handleMsg(msg, handler)
}
// handleMsg is handling message with provided handler. It:
// * checks message size,
// * checks for out-of-range message codes,
// * handles decoding with reflection,
// * call handlers as callbacks
func (p *Peer) handleMsg(msg p2p.Msg, handle func(ctx context.Context, msg interface{}) error) error {
// make sure that the payload has been fully consumed
defer msg.Discard()
if msg.Size > p.spec.MaxMsgSize {
return Break(fmt.Errorf("message too long: %v > %v", msg.Size, p.spec.MaxMsgSize))
}
val, ok := p.spec.NewMsg(msg.Code)
if !ok {
return Break(fmt.Errorf("invalid message code: %v", msg.Code))
}
ctx, msgBytes, err := p.decode(msg)
if err != nil {
return Break(fmt.Errorf("invalid message (RLP error): %v err=%w", msg.Code, err))
}
if err := rlp.DecodeBytes(msgBytes, val); err != nil {
return Break(fmt.Errorf("invalid message (RLP error): <= %v: %w", msg, err))
}
// if the accounting hook is set, do accounting logic
if p.spec.Hook != nil {
size := uint32(len(msgBytes))
// validate that the accounting call would succeed...
costToLocalNode, err := p.spec.Hook.Validate(p, size, val, Receiver)
if err != nil {
// ...because if it would fail, we return and don't handle the message
return Break(err)
}
// seems like accounting would be fine, so handle the message
if err := handle(ctx, val); err != nil {
return fmt.Errorf("message handler: (msg code %v): %w", msg.Code, err)
}
// handling succeeded, finally apply accounting
if err := p.spec.Hook.Apply(p, costToLocalNode, size); err != nil {
return Break(err)
}
} else {
// call the registered handler callbacks
// a registered callback take the decoded message as argument as an interface
// which the handler is supposed to cast to the appropriate type
// it is entirely safe not to check the cast in the handler since the handler is
// chosen based on the proper type in the first place
if err := handle(ctx, val); err != nil {
return fmt.Errorf("message handler: (msg code %v): %w", msg.Code, err)
}
}
return nil
}
// Handshake negotiates a handshake on the peer connection
// * arguments
// * context
// * the local handshake to be sent to the remote peer
// * function to be called on the remote handshake (can be nil)
// * expects a remote handshake back of the same type
// * the dialing peer needs to send the handshake first and then waits for remote
// * the listening peer waits for the remote handshake and then sends it
// returns the remote handshake and an error
func (p *Peer) Handshake(ctx context.Context, hs interface{}, verify func(interface{}) error) (interface{}, error) {
if _, ok := p.spec.GetCode(hs); !ok {
return nil, fmt.Errorf("unknown handshake message type: %T", hs)
}
var rhs interface{}
errc := make(chan error, 2)
send := func() { errc <- p.Send(ctx, hs) }
receive := func() {
errc <- p.receive(func(ctx context.Context, msg interface{}) error {
rhs = msg
if verify != nil {
return verify(rhs)
}
return nil
})
}
go func() {
if p.Inbound() {
receive()
send()
} else {
send()
receive()
}
}()
for i := 0; i < 2; i++ {
var err error
select {
case err = <-errc:
case <-ctx.Done():
err = ctx.Err()
}
if err != nil {
return nil, err
}
}
return rhs, nil
}
// HasCap returns true if Peer has a capability
// with provided name.
func (p *Peer) HasCap(capName string) (yes bool) {
if p == nil || p.Peer == nil {
return false
}
for _, c := range p.Caps() {
if c.Name == capName {
return true
}
}
return false
}