p2p: if no nodes are connected, attempt dialing bootnodes (#13874)

1 files changed, 26 insertions, 2 deletions

diff --git a/p2p/dial.go b/p2p/dial.go
index bb3befab2..b77971396 100644
--- a/p2p/dial.go
+++ b/p2p/dial.go
@@ -38,6 +38,10 @@ const (
 	// once every few seconds.
 	lookupInterval = 4 * time.Second
 
+	// If no peers are found for this amount of time, the initial bootnodes are
+	// attempted to be connected.
+	fallbackInterval = 20 * time.Second
+
 	// Endpoint resolution is throttled with bounded backoff.
 	initialResolveDelay = 60 * time.Second
 	maxResolveDelay     = time.Hour
@@ -57,6 +61,9 @@ type dialstate struct {
 	randomNodes   []*discover.Node // filled from Table
 	static        map[discover.NodeID]*dialTask
 	hist          *dialHistory
+
+	start     time.Time        // time when the dialer was first used
+	bootnodes []*discover.Node // default dials when there are no peers
 }
 
 type discoverTable interface {
@@ -102,16 +109,18 @@ type waitExpireTask struct {
 	time.Duration
 }
 
-func newDialState(static []*discover.Node, ntab discoverTable, maxdyn int, netrestrict *netutil.Netlist) *dialstate {
+func newDialState(static []*discover.Node, bootnodes []*discover.Node, ntab discoverTable, maxdyn int, netrestrict *netutil.Netlist) *dialstate {
 	s := &dialstate{
 		maxDynDials: maxdyn,
 		ntab:        ntab,
 		netrestrict: netrestrict,
 		static:      make(map[discover.NodeID]*dialTask),
 		dialing:     make(map[discover.NodeID]connFlag),
+		bootnodes:   make([]*discover.Node, len(bootnodes)),
 		randomNodes: make([]*discover.Node, maxdyn/2),
 		hist:        new(dialHistory),
 	}
+	copy(s.bootnodes, bootnodes)
 	for _, n := range static {
 		s.addStatic(n)
 	}
@@ -130,6 +139,10 @@ func (s *dialstate) removeStatic(n *discover.Node) {
 }
 
 func (s *dialstate) newTasks(nRunning int, peers map[discover.NodeID]*Peer, now time.Time) []task {
+	if s.start == (time.Time{}) {
+		s.start = now
+	}
+
 	var newtasks []task
 	addDial := func(flag connFlag, n *discover.Node) bool {
 		if err := s.checkDial(n, peers); err != nil {
@@ -169,7 +182,18 @@ func (s *dialstate) newTasks(nRunning int, peers map[discover.NodeID]*Peer, now
 			newtasks = append(newtasks, t)
 		}
 	}
-
+	// If we don't have any peers whatsoever, try to dial a random bootnode. This
+	// scenario is useful for the testnet (and private networks) where the discovery
+	// table might be full of mostly bad peers, making it hard to find good ones.
+	if len(peers) == 0 && len(s.bootnodes) > 0 && needDynDials > 0 && now.Sub(s.start) > fallbackInterval {
+		bootnode := s.bootnodes[0]
+		s.bootnodes = append(s.bootnodes[:0], s.bootnodes[1:]...)
+		s.bootnodes = append(s.bootnodes, bootnode)
+
+		if addDial(dynDialedConn, bootnode) {
+			needDynDials--
+		}
+	}
 	// Use random nodes from the table for half of the necessary
 	// dynamic dials.
 	randomCandidates := needDynDials / 2