|
17 | 17 | package diff |
18 | 18 |
|
19 | 19 | import ( |
| 20 | + "container/list" |
| 21 | + "fmt" |
| 22 | + "sync" |
20 | 23 | "time" |
21 | 24 |
|
22 | | - "github.com/ethereum/go-ethereum/p2p/tracker" |
| 25 | + "github.com/ethereum/go-ethereum/log" |
23 | 26 | ) |
24 | 27 |
|
25 | | -// requestTracker is a singleton tracker for request times. |
26 | | -var requestTracker = tracker.New(ProtocolName, time.Minute) |
| 28 | +const ( |
| 29 | + // maxTrackedPackets is a huge number to act as a failsafe on the number of |
| 30 | + // pending requests the node will track. It should never be hit unless an |
| 31 | + // attacker figures out a way to spin requests. |
| 32 | + maxTrackedPackets = 10000 |
| 33 | +) |
| 34 | + |
| 35 | +// request tracks sent network requests which have not yet received a response. |
| 36 | +type request struct { |
| 37 | + peer string |
| 38 | + version uint // Protocol version |
| 39 | + |
| 40 | + reqCode uint64 // Protocol message code of the request |
| 41 | + resCode uint64 // Protocol message code of the expected response |
| 42 | + |
| 43 | + time time.Time // Timestamp when the request was made |
| 44 | + expire *list.Element // Expiration marker to untrack it |
| 45 | +} |
| 46 | + |
| 47 | +type Tracker struct { |
| 48 | + timeout time.Duration // Global timeout after which to drop a tracked packet |
| 49 | + |
| 50 | + pending map[uint64]*request // Currently pending requests |
| 51 | + expire *list.List // Linked list tracking the expiration order |
| 52 | + wake *time.Timer // Timer tracking the expiration of the next item |
| 53 | + |
| 54 | + lock sync.Mutex // Lock protecting from concurrent updates |
| 55 | +} |
| 56 | + |
| 57 | +func NewTracker(timeout time.Duration) *Tracker { |
| 58 | + return &Tracker{ |
| 59 | + timeout: timeout, |
| 60 | + pending: make(map[uint64]*request), |
| 61 | + expire: list.New(), |
| 62 | + } |
| 63 | +} |
| 64 | + |
| 65 | +// Track adds a network request to the tracker to wait for a response to arrive |
| 66 | +// or until the request it cancelled or times out. |
| 67 | +func (t *Tracker) Track(peer string, version uint, reqCode uint64, resCode uint64, id uint64) { |
| 68 | + t.lock.Lock() |
| 69 | + defer t.lock.Unlock() |
| 70 | + |
| 71 | + // If there's a duplicate request, we've just random-collided (or more probably, |
| 72 | + // we have a bug), report it. We could also add a metric, but we're not really |
| 73 | + // expecting ourselves to be buggy, so a noisy warning should be enough. |
| 74 | + if _, ok := t.pending[id]; ok { |
| 75 | + log.Error("Network request id collision", "version", version, "code", reqCode, "id", id) |
| 76 | + return |
| 77 | + } |
| 78 | + // If we have too many pending requests, bail out instead of leaking memory |
| 79 | + if pending := len(t.pending); pending >= maxTrackedPackets { |
| 80 | + log.Error("Request tracker exceeded allowance", "pending", pending, "peer", peer, "version", version, "code", reqCode) |
| 81 | + return |
| 82 | + } |
| 83 | + // Id doesn't exist yet, start tracking it |
| 84 | + t.pending[id] = &request{ |
| 85 | + peer: peer, |
| 86 | + version: version, |
| 87 | + reqCode: reqCode, |
| 88 | + resCode: resCode, |
| 89 | + time: time.Now(), |
| 90 | + expire: t.expire.PushBack(id), |
| 91 | + } |
| 92 | + |
| 93 | + // If we've just inserted the first item, start the expiration timer |
| 94 | + if t.wake == nil { |
| 95 | + t.wake = time.AfterFunc(t.timeout, t.clean) |
| 96 | + } |
| 97 | +} |
| 98 | + |
| 99 | +// clean is called automatically when a preset time passes without a response |
| 100 | +// being dleivered for the first network request. |
| 101 | +func (t *Tracker) clean() { |
| 102 | + t.lock.Lock() |
| 103 | + defer t.lock.Unlock() |
| 104 | + |
| 105 | + // Expire anything within a certain threshold (might be no items at all if |
| 106 | + // we raced with the delivery) |
| 107 | + for t.expire.Len() > 0 { |
| 108 | + // Stop iterating if the next pending request is still alive |
| 109 | + var ( |
| 110 | + head = t.expire.Front() |
| 111 | + id = head.Value.(uint64) |
| 112 | + req = t.pending[id] |
| 113 | + ) |
| 114 | + if time.Since(req.time) < t.timeout+5*time.Millisecond { |
| 115 | + break |
| 116 | + } |
| 117 | + // Nope, dead, drop it |
| 118 | + t.expire.Remove(head) |
| 119 | + delete(t.pending, id) |
| 120 | + } |
| 121 | + t.schedule() |
| 122 | +} |
| 123 | + |
| 124 | +// schedule starts a timer to trigger on the expiration of the first network |
| 125 | +// packet. |
| 126 | +func (t *Tracker) schedule() { |
| 127 | + if t.expire.Len() == 0 { |
| 128 | + t.wake = nil |
| 129 | + return |
| 130 | + } |
| 131 | + t.wake = time.AfterFunc(time.Until(t.pending[t.expire.Front().Value.(uint64)].time.Add(t.timeout)), t.clean) |
| 132 | +} |
| 133 | + |
| 134 | +// Fulfil fills a pending request, if any is available. |
| 135 | +func (t *Tracker) Fulfil(peer string, version uint, code uint64, id uint64) bool { |
| 136 | + t.lock.Lock() |
| 137 | + defer t.lock.Unlock() |
| 138 | + |
| 139 | + // If it's a non existing request, track as stale response |
| 140 | + req, ok := t.pending[id] |
| 141 | + if !ok { |
| 142 | + return false |
| 143 | + } |
| 144 | + // If the response is funky, it might be some active attack |
| 145 | + if req.peer != peer || req.version != version || req.resCode != code { |
| 146 | + log.Warn("Network response id collision", |
| 147 | + "have", fmt.Sprintf("%s:/%d:%d", peer, version, code), |
| 148 | + "want", fmt.Sprintf("%s:/%d:%d", peer, req.version, req.resCode), |
| 149 | + ) |
| 150 | + return false |
| 151 | + } |
| 152 | + // Everything matches, mark the request serviced |
| 153 | + t.expire.Remove(req.expire) |
| 154 | + delete(t.pending, id) |
| 155 | + if req.expire.Prev() == nil { |
| 156 | + if t.wake.Stop() { |
| 157 | + t.schedule() |
| 158 | + } |
| 159 | + } |
| 160 | + return true |
| 161 | +} |
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