eth_syncing incorrectly reports syncing when it's not

[tersec]

status-im/infra-nimbus#193 (comment)

There are two RPC API implementations with eth_syncing, but the one which the nimbus command appears to run is:

nimbus-eth1/nimbus/rpc/p2p.nim

Lines 101 to 114 in 178d77a

	server.rpc("eth_syncing") do() -> SyncingStatus:
	## Returns SyncObject or false when not syncing.
	# TODO: make sure we are not syncing
	# when we reach the recent block
	let numPeers = node.peerPool.connectedNodes.len
	if numPeers > 0:
	var sync = SyncObject(
	startingBlock: w3Qty com.syncStart,
	currentBlock : w3Qty com.syncCurrent,
	highestBlock : w3Qty com.syncHighest
	)
	result = SyncingStatus(syncing: true, syncObject: sync)
	else:
	result = SyncingStatus(syncing: false)

numPeers > 0 is not correct logic to report syncing happening.

[tersec]

nimbus-eth1/nimbus/rpc/server_api.nim

Lines 145 to 155 in 178d77a

	server.rpc("eth_syncing") do() -> SyncingStatus:
	## Returns SyncObject or false when not syncing.
	if api.com.syncState != Waiting:
	let sync = SyncObject(
	startingBlock: w3Qty api.com.syncStart,
	currentBlock : w3Qty api.com.syncCurrent,
	highestBlock : w3Qty api.com.syncHighest
	)
	return SyncingStatus(syncing: true, syncObject: sync)
	else:
	return SyncingStatus(syncing: false)

looks mostly fine, and doesn't have this incorrect dependency on peer count, but isn't what's used in the application:

nimbus-eth1/nimbus/rpc.nim

Lines 52 to 62 in 178d77a

	proc installRPC(server: RpcServer,
	nimbus: NimbusNode,
	conf: NimbusConf,
	com: CommonRef,
	oracle: Oracle,
	flags: set[RpcFlag]) =
	setupCommonRpc(nimbus.ethNode, conf, server)
	if RpcFlag.Eth in flags:
	setupEthRpc(nimbus.ethNode, nimbus.ctx, com, nimbus.txPool, oracle, server)

sets up the p2p.nim version.

[tersec]

#2619