cmd, eth, les: enable serving light clients when non-synced (#22250)

This PR adds a more CLI flag, so that the les-server can serve light clients even the local node is not synced yet.

This functionality is needed in some testing environments(e.g. hive). After launching the les server, no more blocks will be imported so the node is always marked as "non-synced".

cmd/geth/main.go

@@ -102,6 +102,7 @@ var (
 		utils.UltraLightServersFlag,
 		utils.UltraLightFractionFlag,
 		utils.UltraLightOnlyAnnounceFlag,
+		utils.LightNoSyncServeFlag,
 		utils.WhitelistFlag,
 		utils.BloomFilterSizeFlag,
 		utils.CacheFlag,

cmd/geth/usage.go

@@ -68,6 +68,7 @@ var AppHelpFlagGroups = []flags.FlagGroup{
 			utils.UltraLightFractionFlag,
 			utils.UltraLightOnlyAnnounceFlag,
 			utils.LightNoPruneFlag,
+			utils.LightNoSyncServeFlag,
 		},
 	},
 	{

cmd/utils/flags.go

@@ -269,6 +269,10 @@ var (
 		Name:  "light.nopruning",
 		Usage: "Disable ancient light chain data pruning",
 	}
+	LightNoSyncServeFlag = cli.BoolFlag{
+		Name:  "light.nosyncserve",
+		Usage: "Enables serving light clients before syncing",
+	}
 	// Ethash settings
 	EthashCacheDirFlag = DirectoryFlag{
 		Name:  "ethash.cachedir",
@@ -1042,6 +1046,9 @@ func setLes(ctx *cli.Context, cfg *ethconfig.Config) {
 	if ctx.GlobalIsSet(LightNoPruneFlag.Name) {
 		cfg.LightNoPrune = ctx.GlobalBool(LightNoPruneFlag.Name)
 	}
+	if ctx.GlobalIsSet(LightNoSyncServeFlag.Name) {
+		cfg.LightNoSyncServe = ctx.GlobalBool(LightNoSyncServeFlag.Name)
+	}
 }
 
 // MakeDatabaseHandles raises out the number of allowed file handles per process

eth/ethconfig/config.go

@@ -140,6 +140,7 @@ type Config struct {
 	LightEgress        int  `toml:",omitempty"` // Outgoing bandwidth limit for light servers
 	LightPeers         int  `toml:",omitempty"` // Maximum number of LES client peers
 	LightNoPrune       bool `toml:",omitempty"` // Whether to disable light chain pruning
+	LightNoSyncServe   bool `toml:",omitempty"` // Whether to serve light clients before syncing
 	SyncFromCheckpoint bool `toml:",omitempty"` // Whether to sync the header chain from the configured checkpoint
 
 	// Ultra Light client options

les/server.go

@@ -118,7 +118,11 @@ func NewLesServer(node *node.Node, e ethBackend, config *ethconfig.Config) (*Les
 		threadsIdle:  threads,
 		p2pSrv:       node.Server(),
 	}
-	srv.handler = newServerHandler(srv, e.BlockChain(), e.ChainDb(), e.TxPool(), e.Synced)
+	issync := e.Synced
+	if config.LightNoSyncServe {
+		issync = func() bool { return true }
+	}
+	srv.handler = newServerHandler(srv, e.BlockChain(), e.ChainDb(), e.TxPool(), issync)
 	srv.costTracker, srv.minCapacity = newCostTracker(e.ChainDb(), config)
 	srv.oracle = srv.setupOracle(node, e.BlockChain().Genesis().Hash(), config)