peer+server: add new config option to optionally disable stall detection

In this commit, we add a new config options that allows one to start
`btcd` in an operating mode that disables the stall detection. This can
be useful in simnet/regtest integration tests settings where it's
important that `btcd` holds on to its possibly sole connection to the
only other node in the test harness.

A new config flag has been added to gate this behavior, which is off by
default.

config.go

@@ -29,6 +29,7 @@ import (
 	_ "github.com/btcsuite/btcd/database/ffldb"
 	"github.com/btcsuite/btcd/mempool"
 	"github.com/btcsuite/btcd/peer"
+	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/btcutil"
 	"github.com/btcsuite/go-socks/socks"
 	flags "github.com/jessevdk/go-flags"
@@ -135,6 +136,7 @@ type config struct {
 	NoRelayPriority      bool          `long:"norelaypriority" description:"Do not require free or low-fee transactions to have high priority for relaying"`
 	NoWinService         bool          `long:"nowinservice" description:"Do not start as a background service on Windows -- NOTE: This flag only works on the command line, not in the config file"`
 	DisableRPC           bool          `long:"norpc" description:"Disable built-in RPC server -- NOTE: The RPC server is disabled by default if no rpcuser/rpcpass or rpclimituser/rpclimitpass is specified"`
+	DisableStallHandler  bool          `long:"nostalldetect" description:"Disables the stall handler system for each peer, useful in simnet/regtest integration tests frameworks"`
 	DisableTLS           bool          `long:"notls" description:"Disable TLS for the RPC server -- NOTE: This is only allowed if the RPC server is bound to localhost"`
 	OnionProxy           string        `long:"onion" description:"Connect to tor hidden services via SOCKS5 proxy (eg. 127.0.0.1:9050)"`
 	OnionProxyPass       string        `long:"onionpass" default-mask:"-" description:"Password for onion proxy server"`
@@ -603,6 +605,16 @@ func loadConfig() (*config, []string, error) {
 		return nil, nil, err
 	}
 
+	// If mainnet is active, then we won't allow the stall handler to be
+	// disabled.
+	if activeNetParams.Params.Net == wire.MainNet && cfg.DisableStallHandler {
+		str := "%s: stall handler cannot be disabled on mainnet"
+		err := fmt.Errorf(str, funcName)
+		fmt.Fprintln(os.Stderr, err)
+		fmt.Fprintln(os.Stderr, usageMessage)
+		return nil, nil, err
+	}
+
 	// Set the default policy for relaying non-standard transactions
 	// according to the default of the active network. The set
 	// configuration value takes precedence over the default value for the

peer/peer.go

@@ -276,6 +276,13 @@ type Config struct {
 	// connection detecting and disconnect logic since they intentionally
 	// do so for testing purposes.
 	AllowSelfConns bool
+
+	// DisableStallHandler if true, then the stall handler that attempts to
+	// disconnect from peers that appear to be taking too long to respond
+	// to requests won't be activated. This can be useful in certain simnet
+	// scenarios where the stall behavior isn't important to the system
+	// under test.
+	DisableStallHandler bool
 }
 
 // minUint32 is a helper function to return the minimum of two uint32s.
@@ -1202,6 +1209,10 @@ out:
 	for {
 		select {
 		case msg := <-p.stallControl:
+			if p.cfg.DisableStallHandler {
+				continue
+			}
+
 			switch msg.command {
 			case sccSendMessage:
 				// Add a deadline for the expected response
@@ -1264,6 +1275,10 @@ out:
 			}
 
 		case <-stallTicker.C:
+			if p.cfg.DisableStallHandler {
+				continue
+			}
+
 			// Calculate the offset to apply to the deadline based
 			// on how long the handlers have taken to execute since
 			// the last tick.

server.go

@@ -2054,17 +2054,18 @@ func newPeerConfig(sp *serverPeer) *peer.Config {
 			// other implementations' alert messages, we will not relay theirs.
 			OnAlert: nil,
 		},
-		NewestBlock:       sp.newestBlock,
-		HostToNetAddress:  sp.server.addrManager.HostToNetAddress,
-		Proxy:             cfg.Proxy,
-		UserAgentName:     userAgentName,
-		UserAgentVersion:  userAgentVersion,
-		UserAgentComments: cfg.UserAgentComments,
-		ChainParams:       sp.server.chainParams,
-		Services:          sp.server.services,
-		DisableRelayTx:    cfg.BlocksOnly,
-		ProtocolVersion:   peer.MaxProtocolVersion,
-		TrickleInterval:   cfg.TrickleInterval,
+		NewestBlock:         sp.newestBlock,
+		HostToNetAddress:    sp.server.addrManager.HostToNetAddress,
+		Proxy:               cfg.Proxy,
+		UserAgentName:       userAgentName,
+		UserAgentVersion:    userAgentVersion,
+		UserAgentComments:   cfg.UserAgentComments,
+		ChainParams:         sp.server.chainParams,
+		Services:            sp.server.services,
+		DisableRelayTx:      cfg.BlocksOnly,
+		ProtocolVersion:     peer.MaxProtocolVersion,
+		TrickleInterval:     cfg.TrickleInterval,
+		DisableStallHandler: cfg.DisableStallHandler,
 	}
 }