path: root/rpc/websocket.go

// Copyright 2015 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 (
    "fmt"
    "net/http"
    "os"
    "strings"
    "sync"

    "github.com/ethereum/go-ethereum/logger"
    "github.com/ethereum/go-ethereum/logger/glog"
    "golang.org/x/net/websocket"
    "gopkg.in/fatih/set.v0"
)

// wsReaderWriterCloser reads and write payloads from and to a websocket  connection.
type wsReaderWriterCloser struct {
    c *websocket.Conn
}

// Read will read incoming payload data into p.
func (rw *wsReaderWriterCloser) Read(p []byte) (int, error) {
    return rw.c.Read(p)
}

// Write writes p to the websocket.
func (rw *wsReaderWriterCloser) Write(p []byte) (int, error) {
    return rw.c.Write(p)
}

// Close closes the websocket connection.
func (rw *wsReaderWriterCloser) Close() error {
    return rw.c.Close()
}

// wsHandshakeValidator returns a handler that verifies the origin during the
// websocket upgrade process. When a '*' is specified as an allowed origins all
// connections are accepted.
func wsHandshakeValidator(allowedOrigins []string) func(*websocket.Config, *http.Request) error {
    origins := set.New()
    allowAllOrigins := false

    for _, origin := range allowedOrigins {
        if origin == "*" {
            allowAllOrigins = true
        }
        if origin != "" {
            origins.Add(origin)
        }
    }

    // allow localhost if no allowedOrigins are specified
    if len(origins.List()) == 0 {
        origins.Add("http://localhost")
        if hostname, err := os.Hostname(); err == nil {
            origins.Add("http://" + hostname)
        }
    }

    glog.V(logger.Debug).Infof("Allowed origin(s) for WS RPC interface %v\n", origins.List())

    f := func(cfg *websocket.Config, req *http.Request) error {
        origin := req.Header.Get("Origin")
        if allowAllOrigins || origins.Has(origin) {
            return nil
        }
        glog.V(logger.Debug).Infof("origin '%s' not allowed on WS-RPC interface\n", origin)
        return fmt.Errorf("origin %s not allowed", origin)
    }

    return f
}

// NewWSServer creates a new websocket RPC server around an API provider.
func NewWSServer(cors string, handler *Server) *http.Server {
    return &http.Server{
        Handler: websocket.Server{
            Handshake: wsHandshakeValidator(strings.Split(cors, ",")),
            Handler: func(conn *websocket.Conn) {
                handler.ServeCodec(NewJSONCodec(&wsReaderWriterCloser{conn}))
            },
        },
    }
}

// wsClient represents a RPC client that communicates over websockets with a
// RPC server.
type wsClient struct {
    endpoint string
    connMu   sync.Mutex
    conn     *websocket.Conn
}

// NewWSClientj creates a new RPC client that communicates with a RPC server
// that is listening on the given endpoint using JSON encoding.
func NewWSClient(endpoint string) (Client, error) {
    return &wsClient{endpoint: endpoint}, nil
}

// connection will return a websocket connection to the RPC server. It will
// (re)connect when necessary.
func (client *wsClient) connection() (*websocket.Conn, error) {
    if client.conn != nil {
        return client.conn, nil
    }

    origin, err := os.Hostname()
    if err != nil {
        return nil, err
    }

    origin = "http://" + origin
    client.conn, err = websocket.Dial(client.endpoint, "", origin)

    return client.conn, err
}

// SupportedModules is the collection of modules the RPC server offers.
func (client *wsClient) SupportedModules() (map[string]string, error) {
    return SupportedModules(client)
}

// Send writes the JSON serialized msg to the websocket. It will create a new
// websocket connection to the server if the client is currently not connected.
func (client *wsClient) Send(msg interface{}) (err error) {
    client.connMu.Lock()
    defer client.connMu.Unlock()

    var conn *websocket.Conn
    if conn, err = client.connection(); err == nil {
        if err = websocket.JSON.Send(conn, msg); err != nil {
            client.conn.Close()
            client.conn = nil
        }
    }

    return err
}

// Recv reads a JSON message from the websocket and unmarshals it into msg.
func (client *wsClient) Recv(msg interface{}) (err error) {
    client.connMu.Lock()
    defer client.connMu.Unlock()

    var conn *websocket.Conn
    if conn, err = client.connection(); err == nil {
        if err = websocket.JSON.Receive(conn, msg); err != nil {
            client.conn.Close()
            client.conn = nil
        }
    }
    return
}

// Close closes the underlaying websocket connection.
func (client *wsClient) Close() {
    client.connMu.Lock()
    defer client.connMu.Unlock()

    if client.conn != nil {
        client.conn.Close()
        client.conn = nil
    }

}