path: root/p2p/dial_test.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 (
    "encoding/binary"
    "net"
    "reflect"
    "testing"
    "time"

    "github.com/davecgh/go-spew/spew"
    "github.com/ethereum/go-ethereum/p2p/discover"
    "github.com/ethereum/go-ethereum/p2p/netutil"
)

func init() {
    spew.Config.Indent = "\t"
}

type dialtest struct {
    init   *dialstate // state before and after the test.
    rounds []round
}

type round struct {
    peers []*Peer // current peer set
    done  []task  // tasks that got done this round
    new   []task  // the result must match this one
}

func runDialTest(t *testing.T, test dialtest) {
    var (
        vtime   time.Time
        running int
    )
    pm := func(ps []*Peer) map[discover.NodeID]*Peer {
        m := make(map[discover.NodeID]*Peer)
        for _, p := range ps {
            m[p.rw.id] = p
        }
        return m
    }
    for i, round := range test.rounds {
        for _, task := range round.done {
            running--
            if running < 0 {
                panic("running task counter underflow")
            }
            test.init.taskDone(task, vtime)
        }

        new := test.init.newTasks(running, pm(round.peers), vtime)
        if !sametasks(new, round.new) {
            t.Errorf("round %d: new tasks mismatch:\ngot %v\nwant %v\nstate: %v\nrunning: %v\n",
                i, spew.Sdump(new), spew.Sdump(round.new), spew.Sdump(test.init), spew.Sdump(running))
        }

        // Time advances by 16 seconds on every round.
        vtime = vtime.Add(16 * time.Second)
        running += len(new)
    }
}

type fakeTable []*discover.Node

func (t fakeTable) Self() *discover.Node                     { return new(discover.Node) }
func (t fakeTable) Close()                                   {}
func (t fakeTable) Lookup(discover.NodeID) []*discover.Node  { return nil }
func (t fakeTable) Resolve(discover.NodeID) *discover.Node   { return nil }
func (t fakeTable) ReadRandomNodes(buf []*discover.Node) int { return copy(buf, t) }

// This test checks that dynamic dials are launched from discovery results.
func TestDialStateDynDial(t *testing.T) {
    runDialTest(t, dialtest{
        init: newDialState(nil, nil, fakeTable{}, 5, nil),
        rounds: []round{
            // A discovery query is launched.
            {
                peers: []*Peer{
                    {rw: &conn{flags: staticDialedConn, id: uintID(0)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(2)}},
                },
                new: []task{&discoverTask{}},
            },
            // Dynamic dials are launched when it completes.
            {
                peers: []*Peer{
                    {rw: &conn{flags: staticDialedConn, id: uintID(0)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(2)}},
                },
                done: []task{
                    &discoverTask{results: []*discover.Node{
                        {ID: uintID(2)}, // this one is already connected and not dialed.
                        {ID: uintID(3)},
                        {ID: uintID(4)},
                        {ID: uintID(5)},
                        {ID: uintID(6)}, // these are not tried because max dyn dials is 5
                        {ID: uintID(7)}, // ...
                    }},
                },
                new: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(3)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(4)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(5)}},
                },
            },
            // Some of the dials complete but no new ones are launched yet because
            // the sum of active dial count and dynamic peer count is == maxDynDials.
            {
                peers: []*Peer{
                    {rw: &conn{flags: staticDialedConn, id: uintID(0)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(2)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(3)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(4)}},
                },
                done: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(3)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(4)}},
                },
            },
            // No new dial tasks are launched in the this round because
            // maxDynDials has been reached.
            {
                peers: []*Peer{
                    {rw: &conn{flags: staticDialedConn, id: uintID(0)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(2)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(3)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(4)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(5)}},
                },
                done: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(5)}},
                },
                new: []task{
                    &waitExpireTask{Duration: 14 * time.Second},
                },
            },
            // In this round, the peer with id 2 drops off. The query
            // results from last discovery lookup are reused.
            {
                peers: []*Peer{
                    {rw: &conn{flags: staticDialedConn, id: uintID(0)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(3)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(4)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(5)}},
                },
                new: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(6)}},
                },
            },
            // More peers (3,4) drop off and dial for ID 6 completes.
            // The last query result from the discovery lookup is reused
            // and a new one is spawned because more candidates are needed.
            {
                peers: []*Peer{
                    {rw: &conn{flags: staticDialedConn, id: uintID(0)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(5)}},
                },
                done: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(6)}},
                },
                new: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(7)}},
                    &discoverTask{},
                },
            },
            // Peer 7 is connected, but there still aren't enough dynamic peers
            // (4 out of 5). However, a discovery is already running, so ensure
            // no new is started.
            {
                peers: []*Peer{
                    {rw: &conn{flags: staticDialedConn, id: uintID(0)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(5)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(7)}},
                },
                done: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(7)}},
                },
            },
            // Finish the running node discovery with an empty set. A new lookup
            // should be immediately requested.
            {
                peers: []*Peer{
                    {rw: &conn{flags: staticDialedConn, id: uintID(0)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(5)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(7)}},
                },
                done: []task{
                    &discoverTask{},
                },
                new: []task{
                    &discoverTask{},
                },
            },
        },
    })
}

// Tests that bootnodes are dialed if no peers are connectd, but not otherwise.
func TestDialStateDynDialBootnode(t *testing.T) {
    bootnodes := []*discover.Node{
        {ID: uintID(1)},
        {ID: uintID(2)},
        {ID: uintID(3)},
    }
    table := fakeTable{
        {ID: uintID(4)},
        {ID: uintID(5)},
        {ID: uintID(6)},
        {ID: uintID(7)},
        {ID: uintID(8)},
    }
    runDialTest(t, dialtest{
        init: newDialState(nil, bootnodes, table, 5, nil),
        rounds: []round{
            // 2 dynamic dials attempted, bootnodes pending fallback interval
            {
                new: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(4)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(5)}},
                    &discoverTask{},
                },
            },
            // No dials succeed, bootnodes still pending fallback interval
            {
                done: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(4)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(5)}},
                },
            },
            // No dials succeed, bootnodes still pending fallback interval
            {},
            // No dials succeed, 2 dynamic dials attempted and 1 bootnode too as fallback interval was reached
            {
                new: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(1)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(4)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(5)}},
                },
            },
            // No dials succeed, 2nd bootnode is attempted
            {
                done: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(1)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(4)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(5)}},
                },
                new: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(2)}},
                },
            },
            // No dials succeed, 3rd bootnode is attempted
            {
                done: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(2)}},
                },
                new: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(3)}},
                },
            },
            // No dials succeed, 1st bootnode is attempted again, expired random nodes retried
            {
                done: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(3)}},
                },
                new: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(1)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(4)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(5)}},
                },
            },
            // Random dial succeeds, no more bootnodes are attempted
            {
                peers: []*Peer{
                    {rw: &conn{flags: dynDialedConn, id: uintID(4)}},
                },
                done: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(1)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(4)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(5)}},
                },
            },
        },
    })
}

func TestDialStateDynDialFromTable(t *testing.T) {
    // This table always returns the same random nodes
    // in the order given below.
    table := fakeTable{
        {ID: uintID(1)},
        {ID: uintID(2)},
        {ID: uintID(3)},
        {ID: uintID(4)},
        {ID: uintID(5)},
        {ID: uintID(6)},
        {ID: uintID(7)},
        {ID: uintID(8)},
    }

    runDialTest(t, dialtest{
        init: newDialState(nil, nil, table, 10, nil),
        rounds: []round{
            // 5 out of 8 of the nodes returned by ReadRandomNodes are dialed.
            {
                new: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(1)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(2)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(3)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(4)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(5)}},
                    &discoverTask{},
                },
            },
            // Dialing nodes 1,2 succeeds. Dials from the lookup are launched.
            {
                peers: []*Peer{
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(2)}},
                },
                done: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(1)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(2)}},
                    &discoverTask{results: []*discover.Node{
                        {ID: uintID(10)},
                        {ID: uintID(11)},
                        {ID: uintID(12)},
                    }},
                },
                new: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(10)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(11)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(12)}},
                    &discoverTask{},
                },
            },
            // Dialing nodes 3,4,5 fails. The dials from the lookup succeed.
            {
                peers: []*Peer{
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(2)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(10)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(11)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(12)}},
                },
                done: []task{
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(3)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(4)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(5)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(10)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(11)}},
                    &dialTask{flags: dynDialedConn, dest: &discover.Node{ID: uintID(12)}},
                },
            },
            // Waiting for expiry. No waitExpireTask is launched because the
            // discovery query is still running.
            {
                peers: []*Peer{
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(2)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(10)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(11)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(12)}},
                },
            },
            // Nodes 3,4 are not tried again because only the first two
            // returned random nodes (nodes 1,2) are tried and they're
            // already connected.
            {
                peers: []*Peer{
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(2)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(10)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(11)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(12)}},
                },
            },
        },
    })
}

// This test checks that candidates that do not match the netrestrict list are not dialed.
func TestDialStateNetRestrict(t *testing.T) {
    // This table always returns the same random nodes
    // in the order given below.
    table := fakeTable{
        {ID: uintID(1), IP: net.ParseIP("127.0.0.1")},
        {ID: uintID(2), IP: net.ParseIP("127.0.0.2")},
        {ID: uintID(3), IP: net.ParseIP("127.0.0.3")},
        {ID: uintID(4), IP: net.ParseIP("127.0.0.4")},
        {ID: uintID(5), IP: net.ParseIP("127.0.2.5")},
        {ID: uintID(6), IP: net.ParseIP("127.0.2.6")},
        {ID: uintID(7), IP: net.ParseIP("127.0.2.7")},
        {ID: uintID(8), IP: net.ParseIP("127.0.2.8")},
    }
    restrict := new(netutil.Netlist)
    restrict.Add("127.0.2.0/24")

    runDialTest(t, dialtest{
        init: newDialState(nil, nil, table, 10, restrict),
        rounds: []round{
            {
                new: []task{
                    &dialTask{flags: dynDialedConn, dest: table[4]},
                    &discoverTask{},
                },
            },
        },
    })
}

// This test checks that static dials are launched.
func TestDialStateStaticDial(t *testing.T) {
    wantStatic := []*discover.Node{
        {ID: uintID(1)},
        {ID: uintID(2)},
        {ID: uintID(3)},
        {ID: uintID(4)},
        {ID: uintID(5)},
    }

    runDialTest(t, dialtest{
        init: newDialState(wantStatic, nil, fakeTable{}, 0, nil),
        rounds: []round{
            // Static dials are launched for the nodes that
            // aren't yet connected.
            {
                peers: []*Peer{
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(2)}},
                },
                new: []task{
                    &dialTask{flags: staticDialedConn, dest: &discover.Node{ID: uintID(3)}},
                    &dialTask{flags: staticDialedConn, dest: &discover.Node{ID: uintID(4)}},
                    &dialTask{flags: staticDialedConn, dest: &discover.Node{ID: uintID(5)}},
                },
            },
            // No new tasks are launched in this round because all static
            // nodes are either connected or still being dialed.
            {
                peers: []*Peer{
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(2)}},
                    {rw: &conn{flags: staticDialedConn, id: uintID(3)}},
                },
                done: []task{
                    &dialTask{flags: staticDialedConn, dest: &discover.Node{ID: uintID(3)}},
                },
            },
            // No new dial tasks are launched because all static
            // nodes are now connected.
            {
                peers: []*Peer{
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(2)}},
                    {rw: &conn{flags: staticDialedConn, id: uintID(3)}},
                    {rw: &conn{flags: staticDialedConn, id: uintID(4)}},
                    {rw: &conn{flags: staticDialedConn, id: uintID(5)}},
                },
                done: []task{
                    &dialTask{flags: staticDialedConn, dest: &discover.Node{ID: uintID(4)}},
                    &dialTask{flags: staticDialedConn, dest: &discover.Node{ID: uintID(5)}},
                },
                new: []task{
                    &waitExpireTask{Duration: 14 * time.Second},
                },
            },
            // Wait a round for dial history to expire, no new tasks should spawn.
            {
                peers: []*Peer{
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(2)}},
                    {rw: &conn{flags: staticDialedConn, id: uintID(3)}},
                    {rw: &conn{flags: staticDialedConn, id: uintID(4)}},
                    {rw: &conn{flags: staticDialedConn, id: uintID(5)}},
                },
            },
            // If a static node is dropped, it should be immediately redialed,
            // irrespective whether it was originally static or dynamic.
            {
                peers: []*Peer{
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: staticDialedConn, id: uintID(3)}},
                    {rw: &conn{flags: staticDialedConn, id: uintID(5)}},
                },
                new: []task{
                    &dialTask{flags: staticDialedConn, dest: &discover.Node{ID: uintID(2)}},
                    &dialTask{flags: staticDialedConn, dest: &discover.Node{ID: uintID(4)}},
                },
            },
        },
    })
}

// This test checks that past dials are not retried for some time.
func TestDialStateCache(t *testing.T) {
    wantStatic := []*discover.Node{
        {ID: uintID(1)},
        {ID: uintID(2)},
        {ID: uintID(3)},
    }

    runDialTest(t, dialtest{
        init: newDialState(wantStatic, nil, fakeTable{}, 0, nil),
        rounds: []round{
            // Static dials are launched for the nodes that
            // aren't yet connected.
            {
                peers: nil,
                new: []task{
                    &dialTask{flags: staticDialedConn, dest: &discover.Node{ID: uintID(1)}},
                    &dialTask{flags: staticDialedConn, dest: &discover.Node{ID: uintID(2)}},
                    &dialTask{flags: staticDialedConn, dest: &discover.Node{ID: uintID(3)}},
                },
            },
            // No new tasks are launched in this round because all static
            // nodes are either connected or still being dialed.
            {
                peers: []*Peer{
                    {rw: &conn{flags: staticDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: staticDialedConn, id: uintID(2)}},
                },
                done: []task{
                    &dialTask{flags: staticDialedConn, dest: &discover.Node{ID: uintID(1)}},
                    &dialTask{flags: staticDialedConn, dest: &discover.Node{ID: uintID(2)}},
                },
            },
            // A salvage task is launched to wait for node 3's history
            // entry to expire.
            {
                peers: []*Peer{
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(2)}},
                },
                done: []task{
                    &dialTask{flags: staticDialedConn, dest: &discover.Node{ID: uintID(3)}},
                },
                new: []task{
                    &waitExpireTask{Duration: 14 * time.Second},
                },
            },
            // Still waiting for node 3's entry to expire in the cache.
            {
                peers: []*Peer{
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(2)}},
                },
            },
            // The cache entry for node 3 has expired and is retried.
            {
                peers: []*Peer{
                    {rw: &conn{flags: dynDialedConn, id: uintID(1)}},
                    {rw: &conn{flags: dynDialedConn, id: uintID(2)}},
                },
                new: []task{
                    &dialTask{flags: staticDialedConn, dest: &discover.Node{ID: uintID(3)}},
                },
            },
        },
    })
}

func TestDialResolve(t *testing.T) {
    resolved := discover.NewNode(uintID(1), net.IP{127, 0, 55, 234}, 3333, 4444)
    table := &resolveMock{answer: resolved}
    state := newDialState(nil, nil, table, 0, nil)

    // Check that the task is generated with an incomplete ID.
    dest := discover.NewNode(uintID(1), nil, 0, 0)
    state.addStatic(dest)
    tasks := state.newTasks(0, nil, time.Time{})
    if !reflect.DeepEqual(tasks, []task{&dialTask{flags: staticDialedConn, dest: dest}}) {
        t.Fatalf("expected dial task, got %#v", tasks)
    }

    // Now run the task, it should resolve the ID once.
    config := Config{Dialer: &net.Dialer{Deadline: time.Now().Add(-5 * time.Minute)}}
    srv := &Server{ntab: table, Config: config}
    tasks[0].Do(srv)
    if !reflect.DeepEqual(table.resolveCalls, []discover.NodeID{dest.ID}) {
        t.Fatalf("wrong resolve calls, got %v", table.resolveCalls)
    }

    // Report it as done to the dialer, which should update the static node record.
    state.taskDone(tasks[0], time.Now())
    if state.static[uintID(1)].dest != resolved {
        t.Fatalf("state.dest not updated")
    }
}

// compares task lists but doesn't care about the order.
func sametasks(a, b []task) bool {
    if len(a) != len(b) {
        return false
    }
next:
    for _, ta := range a {
        for _, tb := range b {
            if reflect.DeepEqual(ta, tb) {
                continue next
            }
        }
        return false
    }
    return true
}

func uintID(i uint32) discover.NodeID {
    var id discover.NodeID
    binary.BigEndian.PutUint32(id[:], i)
    return id
}

// implements discoverTable for TestDialResolve
type resolveMock struct {
    resolveCalls []discover.NodeID
    answer       *discover.Node
}

func (t *resolveMock) Resolve(id discover.NodeID) *discover.Node {
    t.resolveCalls = append(t.resolveCalls, id)
    return t.answer
}

func (t *resolveMock) Self() *discover.Node                     { return new(discover.Node) }
func (t *resolveMock) Close()                                   {}
func (t *resolveMock) Bootstrap([]*discover.Node)               {}
func (t *resolveMock) Lookup(discover.NodeID) []*discover.Node  { return nil }
func (t *resolveMock) ReadRandomNodes(buf []*discover.Node) int { return 0 }