path: root/p2p/dial.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 p2p

import (
    "container/heap"
    "crypto/rand"
    "fmt"
    "net"
    "time"

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

const (
    // This is the amount of time spent waiting in between
    // redialing a certain node.
    dialHistoryExpiration = 30 * time.Second

    // Discovery lookups are throttled and can only run
    // once every few seconds.
    lookupInterval = 4 * time.Second
)

// dialstate schedules dials and discovery lookups.
// it get's a chance to compute new tasks on every iteration
// of the main loop in Server.run.
type dialstate struct {
    maxDynDials int
    ntab        discoverTable

    lookupRunning bool
    bootstrapped  bool

    dialing     map[discover.NodeID]connFlag
    lookupBuf   []*discover.Node // current discovery lookup results
    randomNodes []*discover.Node // filled from Table
    static      map[discover.NodeID]*discover.Node
    hist        *dialHistory
}

type discoverTable interface {
    Self() *discover.Node
    Close()
    Bootstrap([]*discover.Node)
    Lookup(target discover.NodeID) []*discover.Node
    ReadRandomNodes([]*discover.Node) int
}

// the dial history remembers recent dials.
type dialHistory []pastDial

// pastDial is an entry in the dial history.
type pastDial struct {
    id  discover.NodeID
    exp time.Time
}

type task interface {
    Do(*Server)
}

// A dialTask is generated for each node that is dialed.
type dialTask struct {
    flags connFlag
    dest  *discover.Node
}

// discoverTask runs discovery table operations.
// Only one discoverTask is active at any time.
//
// If bootstrap is true, the task runs Table.Bootstrap,
// otherwise it performs a random lookup and leaves the
// results in the task.
type discoverTask struct {
    bootstrap bool
    results   []*discover.Node
}

// A waitExpireTask is generated if there are no other tasks
// to keep the loop in Server.run ticking.
type waitExpireTask struct {
    time.Duration
}

func newDialState(static []*discover.Node, ntab discoverTable, maxdyn int) *dialstate {
    s := &dialstate{
        maxDynDials: maxdyn,
        ntab:        ntab,
        static:      make(map[discover.NodeID]*discover.Node),
        dialing:     make(map[discover.NodeID]connFlag),
        randomNodes: make([]*discover.Node, maxdyn/2),
        hist:        new(dialHistory),
    }
    for _, n := range static {
        s.static[n.ID] = n
    }
    return s
}

func (s *dialstate) addStatic(n *discover.Node) {
    s.static[n.ID] = n
}

func (s *dialstate) newTasks(nRunning int, peers map[discover.NodeID]*Peer, now time.Time) []task {
    var newtasks []task
    addDial := func(flag connFlag, n *discover.Node) bool {
        _, dialing := s.dialing[n.ID]
        if dialing || peers[n.ID] != nil || s.hist.contains(n.ID) {
            return false
        }
        s.dialing[n.ID] = flag
        newtasks = append(newtasks, &dialTask{flags: flag, dest: n})
        return true
    }

    // Compute number of dynamic dials necessary at this point.
    needDynDials := s.maxDynDials
    for _, p := range peers {
        if p.rw.is(dynDialedConn) {
            needDynDials--
        }
    }
    for _, flag := range s.dialing {
        if flag&dynDialedConn != 0 {
            needDynDials--
        }
    }

    // Expire the dial history on every invocation.
    s.hist.expire(now)

    // Create dials for static nodes if they are not connected.
    for _, n := range s.static {
        addDial(staticDialedConn, n)
    }

    // Use random nodes from the table for half of the necessary
    // dynamic dials.
    randomCandidates := needDynDials / 2
    if randomCandidates > 0 && s.bootstrapped {
        n := s.ntab.ReadRandomNodes(s.randomNodes)
        for i := 0; i < randomCandidates && i < n; i++ {
            if addDial(dynDialedConn, s.randomNodes[i]) {
                needDynDials--
            }
        }
    }
    // Create dynamic dials from random lookup results, removing tried
    // items from the result buffer.
    i := 0
    for ; i < len(s.lookupBuf) && needDynDials > 0; i++ {
        if addDial(dynDialedConn, s.lookupBuf[i]) {
            needDynDials--
        }
    }
    s.lookupBuf = s.lookupBuf[:copy(s.lookupBuf, s.lookupBuf[i:])]
    // Launch a discovery lookup if more candidates are needed. The
    // first discoverTask bootstraps the table and won't return any
    // results.
    if len(s.lookupBuf) < needDynDials && !s.lookupRunning {
        s.lookupRunning = true
        newtasks = append(newtasks, &discoverTask{bootstrap: !s.bootstrapped})
    }

    // Launch a timer to wait for the next node to expire if all
    // candidates have been tried and no task is currently active.
    // This should prevent cases where the dialer logic is not ticked
    // because there are no pending events.
    if nRunning == 0 && len(newtasks) == 0 && s.hist.Len() > 0 {
        t := &waitExpireTask{s.hist.min().exp.Sub(now)}
        newtasks = append(newtasks, t)
    }
    return newtasks
}

func (s *dialstate) taskDone(t task, now time.Time) {
    switch t := t.(type) {
    case *dialTask:
        s.hist.add(t.dest.ID, now.Add(dialHistoryExpiration))
        delete(s.dialing, t.dest.ID)
    case *discoverTask:
        if t.bootstrap {
            s.bootstrapped = true
        }
        s.lookupRunning = false
        s.lookupBuf = append(s.lookupBuf, t.results...)
    }
}

func (t *dialTask) Do(srv *Server) {
    addr := &net.TCPAddr{IP: t.dest.IP, Port: int(t.dest.TCP)}
    glog.V(logger.Debug).Infof("dialing %v\n", t.dest)
    fd, err := srv.Dialer.Dial("tcp", addr.String())
    if err != nil {
        glog.V(logger.Detail).Infof("dial error: %v", err)
        return
    }
    mfd := newMeteredConn(fd, false)

    srv.setupConn(mfd, t.flags, t.dest)
}
func (t *dialTask) String() string {
    return fmt.Sprintf("%v %x %v:%d", t.flags, t.dest.ID[:8], t.dest.IP, t.dest.TCP)
}

func (t *discoverTask) Do(srv *Server) {
    if t.bootstrap {
        srv.ntab.Bootstrap(srv.BootstrapNodes)
        return
    }
    // newTasks generates a lookup task whenever dynamic dials are
    // necessary. Lookups need to take some time, otherwise the
    // event loop spins too fast.
    next := srv.lastLookup.Add(lookupInterval)
    if now := time.Now(); now.Before(next) {
        time.Sleep(next.Sub(now))
    }
    srv.lastLookup = time.Now()
    var target discover.NodeID
    rand.Read(target[:])
    t.results = srv.ntab.Lookup(target)
}

func (t *discoverTask) String() (s string) {
    if t.bootstrap {
        s = "discovery bootstrap"
    } else {
        s = "discovery lookup"
    }
    if len(t.results) > 0 {
        s += fmt.Sprintf(" (%d results)", len(t.results))
    }
    return s
}

func (t waitExpireTask) Do(*Server) {
    time.Sleep(t.Duration)
}
func (t waitExpireTask) String() string {
    return fmt.Sprintf("wait for dial hist expire (%v)", t.Duration)
}

// Use only these methods to access or modify dialHistory.
func (h dialHistory) min() pastDial {
    return h[0]
}
func (h *dialHistory) add(id discover.NodeID, exp time.Time) {
    heap.Push(h, pastDial{id, exp})
}
func (h dialHistory) contains(id discover.NodeID) bool {
    for _, v := range h {
        if v.id == id {
            return true
        }
    }
    return false
}
func (h *dialHistory) expire(now time.Time) {
    for h.Len() > 0 && h.min().exp.Before(now) {
        heap.Pop(h)
    }
}

// heap.Interface boilerplate
func (h dialHistory) Len() int           { return len(h) }
func (h dialHistory) Less(i, j int) bool { return h[i].exp.Before(h[j].exp) }
func (h dialHistory) Swap(i, j int)      { h[i], h[j] = h[j], h[i] }
func (h *dialHistory) Push(x interface{}) {
    *h = append(*h, x.(pastDial))
}
func (h *dialHistory) Pop() interface{} {
    old := *h
    n := len(old)
    x := old[n-1]
    *h = old[0 : n-1]
    return x
}