path: root/p2p/server.go

// Copyright 2014 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 p2p implements the Ethereum p2p network protocols.
package p2p

import (
    "crypto/ecdsa"
    "errors"
    "fmt"
    "net"
    "sync"
    "time"

    "github.com/ethereum/go-ethereum/logger"
    "github.com/ethereum/go-ethereum/logger/glog"
    "github.com/ethereum/go-ethereum/p2p/discover"
    "github.com/ethereum/go-ethereum/p2p/nat"
)

const (
    defaultDialTimeout      = 15 * time.Second
    refreshPeersInterval    = 30 * time.Second
    staticPeerCheckInterval = 15 * time.Second

    // Maximum number of concurrently handshaking inbound connections.
    maxAcceptConns = 50

    // Maximum number of concurrently dialing outbound connections.
    maxActiveDialTasks = 16

    // Maximum time allowed for reading a complete message.
    // This is effectively the amount of time a connection can be idle.
    frameReadTimeout = 30 * time.Second

    // Maximum amount of time allowed for writing a complete message.
    frameWriteTimeout = 20 * time.Second
)

var errServerStopped = errors.New("server stopped")

var srvjslog = logger.NewJsonLogger()

// Config holds Server options.
type Config struct {
    // This field must be set to a valid secp256k1 private key.
    PrivateKey *ecdsa.PrivateKey

    // MaxPeers is the maximum number of peers that can be
    // connected. It must be greater than zero.
    MaxPeers int

    // MaxPendingPeers is the maximum number of peers that can be pending in the
    // handshake phase, counted separately for inbound and outbound connections.
    // Zero defaults to preset values.
    MaxPendingPeers int

    // Discovery specifies whether the peer discovery mechanism should be started
    // or not. Disabling is usually useful for protocol debugging (manual topology).
    Discovery bool

    // Name sets the node name of this server.
    // Use common.MakeName to create a name that follows existing conventions.
    Name string

    // Bootstrap nodes are used to establish connectivity
    // with the rest of the network.
    BootstrapNodes []*discover.Node

    // Static nodes are used as pre-configured connections which are always
    // maintained and re-connected on disconnects.
    StaticNodes []*discover.Node

    // Trusted nodes are used as pre-configured connections which are always
    // allowed to connect, even above the peer limit.
    TrustedNodes []*discover.Node

    // NodeDatabase is the path to the database containing the previously seen
    // live nodes in the network.
    NodeDatabase string

    // Protocols should contain the protocols supported
    // by the server. Matching protocols are launched for
    // each peer.
    Protocols []Protocol

    // If ListenAddr is set to a non-nil address, the server
    // will listen for incoming connections.
    //
    // If the port is zero, the operating system will pick a port. The
    // ListenAddr field will be updated with the actual address when
    // the server is started.
    ListenAddr string

    // If set to a non-nil value, the given NAT port mapper
    // is used to make the listening port available to the
    // Internet.
    NAT nat.Interface

    // If Dialer is set to a non-nil value, the given Dialer
    // is used to dial outbound peer connections.
    Dialer *net.Dialer

    // If NoDial is true, the server will not dial any peers.
    NoDial bool
}

// Server manages all peer connections.
type Server struct {
    // Config fields may not be modified while the server is running.
    Config

    // Hooks for testing. These are useful because we can inhibit
    // the whole protocol stack.
    newTransport func(net.Conn) transport
    newPeerHook  func(*Peer)

    lock    sync.Mutex // protects running
    running bool

    ntab         discoverTable
    listener     net.Listener
    ourHandshake *protoHandshake
    lastLookup   time.Time

    // These are for Peers, PeerCount (and nothing else).
    peerOp     chan peerOpFunc
    peerOpDone chan struct{}

    quit          chan struct{}
    addstatic     chan *discover.Node
    removestatic  chan *discover.Node
    posthandshake chan *conn
    addpeer       chan *conn
    delpeer       chan *Peer
    loopWG        sync.WaitGroup // loop, listenLoop
}

type peerOpFunc func(map[discover.NodeID]*Peer)

type connFlag int

const (
    dynDialedConn connFlag = 1 << iota
    staticDialedConn
    inboundConn
    trustedConn
)

// conn wraps a network connection with information gathered
// during the two handshakes.
type conn struct {
    fd net.Conn
    transport
    flags connFlag
    cont  chan error      // The run loop uses cont to signal errors to setupConn.
    id    discover.NodeID // valid after the encryption handshake
    caps  []Cap           // valid after the protocol handshake
    name  string          // valid after the protocol handshake
}

type transport interface {
    // The two handshakes.
    doEncHandshake(prv *ecdsa.PrivateKey, dialDest *discover.Node) (discover.NodeID, error)
    doProtoHandshake(our *protoHandshake) (*protoHandshake, error)
    // The MsgReadWriter can only be used after the encryption
    // handshake has completed. The code uses conn.id to track this
    // by setting it to a non-nil value after the encryption handshake.
    MsgReadWriter
    // transports must provide Close because we use MsgPipe in some of
    // the tests. Closing the actual network connection doesn't do
    // anything in those tests because NsgPipe doesn't use it.
    close(err error)
}

func (c *conn) String() string {
    s := c.flags.String() + " conn"
    if (c.id != discover.NodeID{}) {
        s += fmt.Sprintf(" %x", c.id[:8])
    }
    s += " " + c.fd.RemoteAddr().String()
    return s
}

func (f connFlag) String() string {
    s := ""
    if f&trustedConn != 0 {
        s += " trusted"
    }
    if f&dynDialedConn != 0 {
        s += " dyn dial"
    }
    if f&staticDialedConn != 0 {
        s += " static dial"
    }
    if f&inboundConn != 0 {
        s += " inbound"
    }
    if s != "" {
        s = s[1:]
    }
    return s
}

func (c *conn) is(f connFlag) bool {
    return c.flags&f != 0
}

// Peers returns all connected peers.
func (srv *Server) Peers() []*Peer {
    var ps []*Peer
    select {
    // Note: We'd love to put this function into a variable but
    // that seems to cause a weird compiler error in some
    // environments.
    case srv.peerOp <- func(peers map[discover.NodeID]*Peer) {
        for _, p := range peers {
            ps = append(ps, p)
        }
    }:
        <-srv.peerOpDone
    case <-srv.quit:
    }
    return ps
}

// PeerCount returns the number of connected peers.
func (srv *Server) PeerCount() int {
    var count int
    select {
    case srv.peerOp <- func(ps map[discover.NodeID]*Peer) { count = len(ps) }:
        <-srv.peerOpDone
    case <-srv.quit:
    }
    return count
}

// AddPeer connects to the given node and maintains the connection until the
// server is shut down. If the connection fails for any reason, the server will
// attempt to reconnect the peer.
func (srv *Server) AddPeer(node *discover.Node) {
    select {
    case srv.addstatic <- node:
    case <-srv.quit:
    }
}

// RemovePeer disconnects from the given node
func (srv *Server) RemovePeer(node *discover.Node) {
    select {
    case srv.removestatic <- node:
    case <-srv.quit:
    }
}

// Self returns the local node's endpoint information.
func (srv *Server) Self() *discover.Node {
    srv.lock.Lock()
    defer srv.lock.Unlock()

    // If the server's not running, return an empty node
    if !srv.running {
        return &discover.Node{IP: net.ParseIP("0.0.0.0")}
    }
    // If the node is running but discovery is off, manually assemble the node infos
    if srv.ntab == nil {
        // Inbound connections disabled, use zero address
        if srv.listener == nil {
            return &discover.Node{IP: net.ParseIP("0.0.0.0"), ID: discover.PubkeyID(&srv.PrivateKey.PublicKey)}
        }
        // Otherwise inject the listener address too
        addr := srv.listener.Addr().(*net.TCPAddr)
        return &discover.Node{
            ID:  discover.PubkeyID(&srv.PrivateKey.PublicKey),
            IP:  addr.IP,
            TCP: uint16(addr.Port),
        }
    }
    // Otherwise return the live node infos
    return srv.ntab.Self()
}

// Stop terminates the server and all active peer connections.
// It blocks until all active connections have been closed.
func (srv *Server) Stop() {
    srv.lock.Lock()
    defer srv.lock.Unlock()
    if !srv.running {
        return
    }
    srv.running = false
    if srv.listener != nil {
        // this unblocks listener Accept
        srv.listener.Close()
    }
    close(srv.quit)
    srv.loopWG.Wait()
}

// Start starts running the server.
// Servers can not be re-used after stopping.
func (srv *Server) Start() (err error) {
    srv.lock.Lock()
    defer srv.lock.Unlock()
    if srv.running {
        return errors.New("server already running")
    }
    srv.running = true
    glog.V(logger.Info).Infoln("Starting Server")

    // static fields
    if srv.PrivateKey == nil {
        return fmt.Errorf("Server.PrivateKey must be set to a non-nil key")
    }
    if srv.newTransport == nil {
        srv.newTransport = newRLPX
    }
    if srv.Dialer == nil {
        srv.Dialer = &net.Dialer{Timeout: defaultDialTimeout}
    }
    srv.quit = make(chan struct{})
    srv.addpeer = make(chan *conn)
    srv.delpeer = make(chan *Peer)
    srv.posthandshake = make(chan *conn)
    srv.addstatic = make(chan *discover.Node)
    srv.removestatic = make(chan *discover.Node)
    srv.peerOp = make(chan peerOpFunc)
    srv.peerOpDone = make(chan struct{})

    // node table
    if srv.Discovery {
        ntab, err := discover.ListenUDP(srv.PrivateKey, srv.ListenAddr, srv.NAT, srv.NodeDatabase)
        if err != nil {
            return err
        }
        if err := ntab.SetFallbackNodes(srv.BootstrapNodes); err != nil {
            return err
        }
        srv.ntab = ntab
    }

    dynPeers := (srv.MaxPeers + 1) / 2
    if !srv.Discovery {
        dynPeers = 0
    }
    dialer := newDialState(srv.StaticNodes, srv.ntab, dynPeers)

    // handshake
    srv.ourHandshake = &protoHandshake{Version: baseProtocolVersion, Name: srv.Name, ID: discover.PubkeyID(&srv.PrivateKey.PublicKey)}
    for _, p := range srv.Protocols {
        srv.ourHandshake.Caps = append(srv.ourHandshake.Caps, p.cap())
    }
    // listen/dial
    if srv.ListenAddr != "" {
        if err := srv.startListening(); err != nil {
            return err
        }
    }
    if srv.NoDial && srv.ListenAddr == "" {
        glog.V(logger.Warn).Infoln("I will be kind-of useless, neither dialing nor listening.")
    }

    srv.loopWG.Add(1)
    go srv.run(dialer)
    srv.running = true
    return nil
}

func (srv *Server) startListening() error {
    // Launch the TCP listener.
    listener, err := net.Listen("tcp", srv.ListenAddr)
    if err != nil {
        return err
    }
    laddr := listener.Addr().(*net.TCPAddr)
    srv.ListenAddr = laddr.String()
    srv.listener = listener
    srv.loopWG.Add(1)
    go srv.listenLoop()
    // Map the TCP listening port if NAT is configured.
    if !laddr.IP.IsLoopback() && srv.NAT != nil {
        srv.loopWG.Add(1)
        go func() {
            nat.Map(srv.NAT, srv.quit, "tcp", laddr.Port, laddr.Port, "ethereum p2p")
            srv.loopWG.Done()
        }()
    }
    return nil
}

type dialer interface {
    newTasks(running int, peers map[discover.NodeID]*Peer, now time.Time) []task
    taskDone(task, time.Time)
    addStatic(*discover.Node)
    removeStatic(*discover.Node)
}

func (srv *Server) run(dialstate dialer) {
    defer srv.loopWG.Done()
    var (
        peers        = make(map[discover.NodeID]*Peer)
        trusted      = make(map[discover.NodeID]bool, len(srv.TrustedNodes))
        taskdone     = make(chan task, maxActiveDialTasks)
        runningTasks []task
        queuedTasks  []task // tasks that can't run yet
    )
    // Put trusted nodes into a map to speed up checks.
    // Trusted peers are loaded on startup and cannot be
    // modified while the server is running.
    for _, n := range srv.TrustedNodes {
        trusted[n.ID] = true
    }

    // removes t from runningTasks
    delTask := func(t task) {
        for i := range runningTasks {
            if runningTasks[i] == t {
                runningTasks = append(runningTasks[:i], runningTasks[i+1:]...)
                break
            }
        }
    }
    // starts until max number of active tasks is satisfied
    startTasks := func(ts []task) (rest []task) {
        i := 0
        for ; len(runningTasks) < maxActiveDialTasks && i < len(ts); i++ {
            t := ts[i]
            glog.V(logger.Detail).Infoln("new task:", t)
            go func() { t.Do(srv); taskdone <- t }()
            runningTasks = append(runningTasks, t)
        }
        return ts[i:]
    }
    scheduleTasks := func() {
        // Start from queue first.
        queuedTasks = append(queuedTasks[:0], startTasks(queuedTasks)...)
        // Query dialer for new tasks and start as many as possible now.
        if len(runningTasks) < maxActiveDialTasks {
            nt := dialstate.newTasks(len(runningTasks)+len(queuedTasks), peers, time.Now())
            queuedTasks = append(queuedTasks, startTasks(nt)...)
        }
    }

running:
    for {
        scheduleTasks()

        select {
        case <-srv.quit:
            // The server was stopped. Run the cleanup logic.
            glog.V(logger.Detail).Infoln("<-quit: spinning down")
            break running
        case n := <-srv.addstatic:
            // This channel is used by AddPeer to add to the
            // ephemeral static peer list. Add it to the dialer,
            // it will keep the node connected.
            glog.V(logger.Detail).Infoln("<-addstatic:", n)
            dialstate.addStatic(n)
        case n := <-srv.removestatic:
            // This channel is used by RemovePeer to send a
            // disconnect request to a peer and begin the
            // stop keeping the node connected
            glog.V(logger.Detail).Infoln("<-removestatic:", n)
            dialstate.removeStatic(n)
            if p, ok := peers[n.ID]; ok {
                p.Disconnect(DiscRequested)
            }
        case op := <-srv.peerOp:
            // This channel is used by Peers and PeerCount.
            op(peers)
            srv.peerOpDone <- struct{}{}
        case t := <-taskdone:
            // A task got done. Tell dialstate about it so it
            // can update its state and remove it from the active
            // tasks list.
            glog.V(logger.Detail).Infoln("<-taskdone:", t)
            dialstate.taskDone(t, time.Now())
            delTask(t)
        case c := <-srv.posthandshake:
            // A connection has passed the encryption handshake so
            // the remote identity is known (but hasn't been verified yet).
            if trusted[c.id] {
                // Ensure that the trusted flag is set before checking against MaxPeers.
                c.flags |= trustedConn
            }
            glog.V(logger.Detail).Infoln("<-posthandshake:", c)
            // TODO: track in-progress inbound node IDs (pre-Peer) to avoid dialing them.
            c.cont <- srv.encHandshakeChecks(peers, c)
        case c := <-srv.addpeer:
            // At this point the connection is past the protocol handshake.
            // Its capabilities are known and the remote identity is verified.
            glog.V(logger.Detail).Infoln("<-addpeer:", c)
            err := srv.protoHandshakeChecks(peers, c)
            if err != nil {
                glog.V(logger.Detail).Infof("Not adding %v as peer: %v", c, err)
            } else {
                // The handshakes are done and it passed all checks.
                p := newPeer(c, srv.Protocols)
                peers[c.id] = p
                go srv.runPeer(p)
            }
            // The dialer logic relies on the assumption that
            // dial tasks complete after the peer has been added or
            // discarded. Unblock the task last.
            c.cont <- err
        case p := <-srv.delpeer:
            // A peer disconnected.
            glog.V(logger.Detail).Infoln("<-delpeer:", p)
            delete(peers, p.ID())
        }
    }

    // Terminate discovery. If there is a running lookup it will terminate soon.
    if srv.ntab != nil {
        srv.ntab.Close()
    }
    // Disconnect all peers.
    for _, p := range peers {
        p.Disconnect(DiscQuitting)
    }
    // Wait for peers to shut down. Pending connections and tasks are
    // not handled here and will terminate soon-ish because srv.quit
    // is closed.
    glog.V(logger.Detail).Infof("ignoring %d pending tasks at spindown", len(runningTasks))
    for len(peers) > 0 {
        p := <-srv.delpeer
        glog.V(logger.Detail).Infoln("<-delpeer (spindown):", p)
        delete(peers, p.ID())
    }
}

func (srv *Server) protoHandshakeChecks(peers map[discover.NodeID]*Peer, c *conn) error {
    // Drop connections with no matching protocols.
    if len(srv.Protocols) > 0 && countMatchingProtocols(srv.Protocols, c.caps) == 0 {
        return DiscUselessPeer
    }
    // Repeat the encryption handshake checks because the
    // peer set might have changed between the handshakes.
    return srv.encHandshakeChecks(peers, c)
}

func (srv *Server) encHandshakeChecks(peers map[discover.NodeID]*Peer, c *conn) error {
    switch {
    case !c.is(trustedConn|staticDialedConn) && len(peers) >= srv.MaxPeers:
        return DiscTooManyPeers
    case peers[c.id] != nil:
        return DiscAlreadyConnected
    case c.id == srv.Self().ID:
        return DiscSelf
    default:
        return nil
    }
}

type tempError interface {
    Temporary() bool
}

// listenLoop runs in its own goroutine and accepts
// inbound connections.
func (srv *Server) listenLoop() {
    defer srv.loopWG.Done()
    glog.V(logger.Info).Infoln("Listening on", srv.listener.Addr())

    // This channel acts as a semaphore limiting
    // active inbound connections that are lingering pre-handshake.
    // If all slots are taken, no further connections are accepted.
    tokens := maxAcceptConns
    if srv.MaxPendingPeers > 0 {
        tokens = srv.MaxPendingPeers
    }
    slots := make(chan struct{}, tokens)
    for i := 0; i < tokens; i++ {
        slots <- struct{}{}
    }

    for {
        // Wait for a handshake slot before accepting.
        <-slots

        var (
            fd  net.Conn
            err error
        )
        for {
            fd, err = srv.listener.Accept()
            if tempErr, ok := err.(tempError); ok && tempErr.Temporary() {
                glog.V(logger.Debug).Infof("Temporary read error: %v", err)
                continue
            } else if err != nil {
                glog.V(logger.Debug).Infof("Read error: %v", err)
                return
            }
            break
        }
        fd = newMeteredConn(fd, true)
        glog.V(logger.Debug).Infof("Accepted conn %v\n", fd.RemoteAddr())

        // Spawn the handler. It will give the slot back when the connection
        // has been established.
        go func() {
            srv.setupConn(fd, inboundConn, nil)
            slots <- struct{}{}
        }()
    }
}

// setupConn runs the handshakes and attempts to add the connection
// as a peer. It returns when the connection has been added as a peer
// or the handshakes have failed.
func (srv *Server) setupConn(fd net.Conn, flags connFlag, dialDest *discover.Node) {
    // Prevent leftover pending conns from entering the handshake.
    srv.lock.Lock()
    running := srv.running
    srv.lock.Unlock()
    c := &conn{fd: fd, transport: srv.newTransport(fd), flags: flags, cont: make(chan error)}
    if !running {
        c.close(errServerStopped)
        return
    }
    // Run the encryption handshake.
    var err error
    if c.id, err = c.doEncHandshake(srv.PrivateKey, dialDest); err != nil {
        glog.V(logger.Debug).Infof("%v faild enc handshake: %v", c, err)
        c.close(err)
        return
    }
    // For dialed connections, check that the remote public key matches.
    if dialDest != nil && c.id != dialDest.ID {
        c.close(DiscUnexpectedIdentity)
        glog.V(logger.Debug).Infof("%v dialed identity mismatch, want %x", c, dialDest.ID[:8])
        return
    }
    if err := srv.checkpoint(c, srv.posthandshake); err != nil {
        glog.V(logger.Debug).Infof("%v failed checkpoint posthandshake: %v", c, err)
        c.close(err)
        return
    }
    // Run the protocol handshake
    phs, err := c.doProtoHandshake(srv.ourHandshake)
    if err != nil {
        glog.V(logger.Debug).Infof("%v failed proto handshake: %v", c, err)
        c.close(err)
        return
    }
    if phs.ID != c.id {
        glog.V(logger.Debug).Infof("%v wrong proto handshake identity: %x", c, phs.ID[:8])
        c.close(DiscUnexpectedIdentity)
        return
    }
    c.caps, c.name = phs.Caps, phs.Name
    if err := srv.checkpoint(c, srv.addpeer); err != nil {
        glog.V(logger.Debug).Infof("%v failed checkpoint addpeer: %v", c, err)
        c.close(err)
        return
    }
    // If the checks completed successfully, runPeer has now been
    // launched by run.
}

// checkpoint sends the conn to run, which performs the
// post-handshake checks for the stage (posthandshake, addpeer).
func (srv *Server) checkpoint(c *conn, stage chan<- *conn) error {
    select {
    case stage <- c:
    case <-srv.quit:
        return errServerStopped
    }
    select {
    case err := <-c.cont:
        return err
    case <-srv.quit:
        return errServerStopped
    }
}

// runPeer runs in its own goroutine for each peer.
// it waits until the Peer logic returns and removes
// the peer.
func (srv *Server) runPeer(p *Peer) {
    glog.V(logger.Debug).Infof("Added %v\n", p)
    srvjslog.LogJson(&logger.P2PConnected{
        RemoteId:            p.ID().String(),
        RemoteAddress:       p.RemoteAddr().String(),
        RemoteVersionString: p.Name(),
        NumConnections:      srv.PeerCount(),
    })

    if srv.newPeerHook != nil {
        srv.newPeerHook(p)
    }
    discreason := p.run()
    // Note: run waits for existing peers to be sent on srv.delpeer
    // before returning, so this send should not select on srv.quit.
    srv.delpeer <- p

    glog.V(logger.Debug).Infof("Removed %v (%v)\n", p, discreason)
    srvjslog.LogJson(&logger.P2PDisconnected{
        RemoteId:       p.ID().String(),
        NumConnections: srv.PeerCount(),
    })
}

// NodeInfo represents a short summary of the information known about the host.
type NodeInfo struct {
    ID    string `json:"id"`    // Unique node identifier (also the encryption key)
    Name  string `json:"name"`  // Name of the node, including client type, version, OS, custom data
    Enode string `json:"enode"` // Enode URL for adding this peer from remote peers
    IP    string `json:"ip"`    // IP address of the node
    Ports struct {
        Discovery int `json:"discovery"` // UDP listening port for discovery protocol
        Listener  int `json:"listener"`  // TCP listening port for RLPx
    } `json:"ports"`
    ListenAddr string                 `json:"listenAddr"`
    Protocols  map[string]interface{} `json:"protocols"`
}

// Info gathers and returns a collection of metadata known about the host.
func (srv *Server) NodeInfo() *NodeInfo {
    node := srv.Self()

    // Gather and assemble the generic node infos
    info := &NodeInfo{
        Name:       srv.Name,
        Enode:      node.String(),
        ID:         node.ID.String(),
        IP:         node.IP.String(),
        ListenAddr: srv.ListenAddr,
        Protocols:  make(map[string]interface{}),
    }
    info.Ports.Discovery = int(node.UDP)
    info.Ports.Listener = int(node.TCP)

    // Gather all the running protocol infos (only once per protocol type)
    for _, proto := range srv.Protocols {
        if _, ok := info.Protocols[proto.Name]; !ok {
            nodeInfo := interface{}("unknown")
            if query := proto.NodeInfo; query != nil {
                nodeInfo = proto.NodeInfo()
            }
            info.Protocols[proto.Name] = nodeInfo
        }
    }
    return info
}

// PeersInfo returns an array of metadata objects describing connected peers.
func (srv *Server) PeersInfo() []*PeerInfo {
    // Gather all the generic and sub-protocol specific infos
    infos := make([]*PeerInfo, 0, srv.PeerCount())
    for _, peer := range srv.Peers() {
        if peer != nil {
            infos = append(infos, peer.Info())
        }
    }
    // Sort the result array alphabetically by node identifier
    for i := 0; i < len(infos); i++ {
        for j := i + 1; j < len(infos); j++ {
            if infos[i].ID > infos[j].ID {
                infos[i], infos[j] = infos[j], infos[i]
            }
        }
    }
    return infos
}