// Copyright 2019 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 rpc import ( "context" "encoding/json" "reflect" "strconv" "strings" "sync" "time" "github.com/ava-labs/go-ethereum/log" ) // handler handles JSON-RPC messages. There is one handler per connection. Note that // handler is not safe for concurrent use. Message handling never blocks indefinitely // because RPCs are processed on background goroutines launched by handler. // // The entry points for incoming messages are: // // h.handleMsg(message) // h.handleBatch(message) // // Outgoing calls use the requestOp struct. Register the request before sending it // on the connection: // // op := &requestOp{ids: ...} // h.addRequestOp(op) // // Now send the request, then wait for the reply to be delivered through handleMsg: // // if err := op.wait(...); err != nil { // h.removeRequestOp(op) // timeout, etc. // } // type handler struct { reg *serviceRegistry unsubscribeCb *callback idgen func() ID // subscription ID generator respWait map[string]*requestOp // active client requests clientSubs map[string]*ClientSubscription // active client subscriptions callWG sync.WaitGroup // pending call goroutines rootCtx context.Context // canceled by close() cancelRoot func() // cancel function for rootCtx conn jsonWriter // where responses will be sent log log.Logger allowSubscribe bool subLock sync.Mutex serverSubs map[ID]*Subscription } type callProc struct { ctx context.Context notifiers []*Notifier } func newHandler(connCtx context.Context, conn jsonWriter, idgen func() ID, reg *serviceRegistry) *handler { rootCtx, cancelRoot := context.WithCancel(connCtx) h := &handler{ reg: reg, idgen: idgen, conn: conn, respWait: make(map[string]*requestOp), clientSubs: make(map[string]*ClientSubscription), rootCtx: rootCtx, cancelRoot: cancelRoot, allowSubscribe: true, serverSubs: make(map[ID]*Subscription), log: log.Root(), } if conn.RemoteAddr() != "" { h.log = h.log.New("conn", conn.RemoteAddr()) } h.unsubscribeCb = newCallback(reflect.Value{}, reflect.ValueOf(h.unsubscribe)) return h } // handleBatch executes all messages in a batch and returns the responses. func (h *handler) handleBatch(msgs []*jsonrpcMessage) { // Emit error response for empty batches: if len(msgs) == 0 { h.startCallProc(func(cp *callProc) { h.conn.Write(cp.ctx, errorMessage(&invalidRequestError{"empty batch"})) }) return } // Handle non-call messages first: calls := make([]*jsonrpcMessage, 0, len(msgs)) for _, msg := range msgs { if handled := h.handleImmediate(msg); !handled { calls = append(calls, msg) } } if len(calls) == 0 { return } // Process calls on a goroutine because they may block indefinitely: h.startCallProc(func(cp *callProc) { answers := make([]*jsonrpcMessage, 0, len(msgs)) for _, msg := range calls { if answer := h.handleCallMsg(cp, msg); answer != nil { answers = append(answers, answer) } } h.addSubscriptions(cp.notifiers) if len(answers) > 0 { h.conn.Write(cp.ctx, answers) } for _, n := range cp.notifiers { n.activate() } }) } // handleMsg handles a single message. func (h *handler) handleMsg(msg *jsonrpcMessage) { if ok := h.handleImmediate(msg); ok { return } h.startCallProc(func(cp *callProc) { answer := h.handleCallMsg(cp, msg) h.addSubscriptions(cp.notifiers) if answer != nil { h.conn.Write(cp.ctx, answer) } for _, n := range cp.notifiers { n.activate() } }) } // close cancels all requests except for inflightReq and waits for // call goroutines to shut down. func (h *handler) close(err error, inflightReq *requestOp) { h.cancelAllRequests(err, inflightReq) h.callWG.Wait() h.cancelRoot() h.cancelServerSubscriptions(err) } // addRequestOp registers a request operation. func (h *handler) addRequestOp(op *requestOp) { for _, id := range op.ids { h.respWait[string(id)] = op } } // removeRequestOps stops waiting for the given request IDs. func (h *handler) removeRequestOp(op *requestOp) { for _, id := range op.ids { delete(h.respWait, string(id)) } } // cancelAllRequests unblocks and removes pending requests and active subscriptions. func (h *handler) cancelAllRequests(err error, inflightReq *requestOp) { didClose := make(map[*requestOp]bool) if inflightReq != nil { didClose[inflightReq] = true } for id, op := range h.respWait { // Remove the op so that later calls will not close op.resp again. delete(h.respWait, id) if !didClose[op] { op.err = err close(op.resp) didClose[op] = true } } for id, sub := range h.clientSubs { delete(h.clientSubs, id) sub.quitWithError(err, false) } } func (h *handler) addSubscriptions(nn []*Notifier) { h.subLock.Lock() defer h.subLock.Unlock() for _, n := range nn { if sub := n.takeSubscription(); sub != nil { h.serverSubs[sub.ID] = sub } } } // cancelServerSubscriptions removes all subscriptions and closes their error channels. func (h *handler) cancelServerSubscriptions(err error) { h.subLock.Lock() defer h.subLock.Unlock() for id, s := range h.serverSubs { s.err <- err close(s.err) delete(h.serverSubs, id) } } // startCallProc runs fn in a new goroutine and starts tracking it in the h.calls wait group. func (h *handler) startCallProc(fn func(*callProc)) { h.callWG.Add(1) go func() { ctx, cancel := context.WithCancel(h.rootCtx) defer h.callWG.Done() defer cancel() fn(&callProc{ctx: ctx}) }() } // handleImmediate executes non-call messages. It returns false if the message is a // call or requires a reply. func (h *handler) handleImmediate(msg *jsonrpcMessage) bool { start := time.Now() switch { case msg.isNotification(): if strings.HasSuffix(msg.Method, notificationMethodSuffix) { h.handleSubscriptionResult(msg) return true } return false case msg.isResponse(): h.handleResponse(msg) h.log.Trace("Handled RPC response", "reqid", idForLog{msg.ID}, "t", time.Since(start)) return true default: return false } } // handleSubscriptionResult processes subscription notifications. func (h *handler) handleSubscriptionResult(msg *jsonrpcMessage) { var result subscriptionResult if err := json.Unmarshal(msg.Params, &result); err != nil { h.log.Debug("Dropping invalid subscription message") return } if h.clientSubs[result.ID] != nil { h.clientSubs[result.ID].deliver(result.Result) } } // handleResponse processes method call responses. func (h *handler) handleResponse(msg *jsonrpcMessage) { op := h.respWait[string(msg.ID)] if op == nil { h.log.Debug("Unsolicited RPC response", "reqid", idForLog{msg.ID}) return } delete(h.respWait, string(msg.ID)) // For normal responses, just forward the reply to Call/BatchCall. if op.sub == nil { op.resp <- msg return } // For subscription responses, start the subscription if the server // indicates success. EthSubscribe gets unblocked in either case through // the op.resp channel. defer close(op.resp) if msg.Error != nil { op.err = msg.Error return } if op.err = json.Unmarshal(msg.Result, &op.sub.subid); op.err == nil { go op.sub.start() h.clientSubs[op.sub.subid] = op.sub } } // handleCallMsg executes a call message and returns the answer. func (h *handler) handleCallMsg(ctx *callProc, msg *jsonrpcMessage) *jsonrpcMessage { start := time.Now() switch { case msg.isNotification(): h.handleCall(ctx, msg) h.log.Debug("Served "+msg.Method, "t", time.Since(start)) return nil case msg.isCall(): resp := h.handleCall(ctx, msg) if resp.Error != nil { h.log.Warn("Served "+msg.Method, "reqid", idForLog{msg.ID}, "t", time.Since(start), "err", resp.Error.Message) } else { h.log.Debug("Served "+msg.Method, "reqid", idForLog{msg.ID}, "t", time.Since(start)) } return resp case msg.hasValidID(): return msg.errorResponse(&invalidRequestError{"invalid request"}) default: return errorMessage(&invalidRequestError{"invalid request"}) } } // handleCall processes method calls. func (h *handler) handleCall(cp *callProc, msg *jsonrpcMessage) *jsonrpcMessage { if msg.isSubscribe() { return h.handleSubscribe(cp, msg) } var callb *callback if msg.isUnsubscribe() { callb = h.unsubscribeCb } else { callb = h.reg.callback(msg.Method) } if callb == nil { return msg.errorResponse(&methodNotFoundError{method: msg.Method}) } args, err := parsePositionalArguments(msg.Params, callb.argTypes) if err != nil { return msg.errorResponse(&invalidParamsError{err.Error()}) } return h.runMethod(cp.ctx, msg, callb, args) } // handleSubscribe processes *_subscribe method calls. func (h *handler) handleSubscribe(cp *callProc, msg *jsonrpcMessage) *jsonrpcMessage { if !h.allowSubscribe { return msg.errorResponse(ErrNotificationsUnsupported) } // Subscription method name is first argument. name, err := parseSubscriptionName(msg.Params) if err != nil { return msg.errorResponse(&invalidParamsError{err.Error()}) } namespace := msg.namespace() callb := h.reg.subscription(namespace, name) if callb == nil { return msg.errorResponse(&subscriptionNotFoundError{namespace, name}) } // Parse subscription name arg too, but remove it before calling the callback. argTypes := append([]reflect.Type{stringType}, callb.argTypes...) args, err := parsePositionalArguments(msg.Params, argTypes) if err != nil { return msg.errorResponse(&invalidParamsError{err.Error()}) } args = args[1:] // Install notifier in context so the subscription handler can find it. n := &Notifier{h: h, namespace: namespace} cp.notifiers = append(cp.notifiers, n) ctx := context.WithValue(cp.ctx, notifierKey{}, n) return h.runMethod(ctx, msg, callb, args) } // runMethod runs the Go callback for an RPC method. func (h *handler) runMethod(ctx context.Context, msg *jsonrpcMessage, callb *callback, args []reflect.Value) *jsonrpcMessage { result, err := callb.call(ctx, msg.Method, args) if err != nil { return msg.errorResponse(err) } return msg.response(result) } // unsubscribe is the callback function for all *_unsubscribe calls. func (h *handler) unsubscribe(ctx context.Context, id ID) (bool, error) { h.subLock.Lock() defer h.subLock.Unlock() s := h.serverSubs[id] if s == nil { return false, ErrSubscriptionNotFound } close(s.err) delete(h.serverSubs, id) return true, nil } type idForLog struct{ json.RawMessage } func (id idForLog) String() string { if s, err := strconv.Unquote(string(id.RawMessage)); err == nil { return s } return string(id.RawMessage) }