diff options
| -rw-r--r-- | p2p/discover/table.go | 54 |
1 files changed, 41 insertions, 13 deletions
diff --git a/p2p/discover/table.go b/p2p/discover/table.go index ee1d58cae..38bdea0ca 100644 --- a/p2p/discover/table.go +++ b/p2p/discover/table.go @@ -191,6 +191,12 @@ func (tab *Table) Lookup(targetID NodeID) []*Node { result := tab.closest(target, bucketSize) tab.mutex.Unlock() + // If the result set is empty, all nodes were dropped, refresh + if len(result.entries) == 0 { + tab.refresh() + return nil + } + for { // ask the alpha closest nodes that we haven't asked yet for i := 0; i < len(result.entries) && pendingQueries < alpha; i++ { @@ -207,7 +213,7 @@ func (tab *Table) Lookup(targetID NodeID) []*Node { tab.db.updateFindFails(n.ID, fails) glog.V(logger.Detail).Infof("Bumping failures for %x: %d", n.ID[:8], fails) - if fails > maxFindnodeFailures { + if fails >= maxFindnodeFailures { glog.V(logger.Detail).Infof("Evacuating node %x: %d findnode failures", n.ID[:8], fails) tab.del(n) } @@ -232,19 +238,41 @@ func (tab *Table) Lookup(targetID NodeID) []*Node { return result.entries } -// refresh performs a lookup for a random target to keep buckets full. +// refresh performs a lookup for a random target to keep buckets full, or seeds +// the table if it is empty (initial bootstrap or discarded faulty peers). func (tab *Table) refresh() { - // The Kademlia paper specifies that the bucket refresh should - // perform a refresh in the least recently used bucket. We cannot - // adhere to this because the findnode target is a 512bit value - // (not hash-sized) and it is not easily possible to generate a - // sha3 preimage that falls into a chosen bucket. - // - // We perform a lookup with a random target instead. - var target NodeID - rand.Read(target[:]) - result := tab.Lookup(target) - if len(result) == 0 { + seed := true + + // If the discovery table is empty, seed with previously known nodes + tab.mutex.Lock() + for _, bucket := range tab.buckets { + if len(bucket.entries) > 0 { + seed = false + break + } + } + tab.mutex.Unlock() + + // If the table is not empty, try to refresh using the live entries + if !seed { + // The Kademlia paper specifies that the bucket refresh should + // perform a refresh in the least recently used bucket. We cannot + // adhere to this because the findnode target is a 512bit value + // (not hash-sized) and it is not easily possible to generate a + // sha3 preimage that falls into a chosen bucket. + // + // We perform a lookup with a random target instead. + var target NodeID + rand.Read(target[:]) + + result := tab.Lookup(target) + if len(result) == 0 { + // Lookup failed, seed after all + seed = true + } + } + + if seed { // Pick a batch of previously know seeds to lookup with seeds := tab.db.querySeeds(10) for _, seed := range seeds { |