itest+lntest: use system wide unique ports everywhere

With this commit we create a new function that returns system wide
unique ports by using a single file to keep track of previously used
ports. We'll want to use this everywhere whenever we need to listen on a
new, random port during unit or integration tests.
Because we now have a unique source, we don't need to apply the port
offset that was used for the different tranches of parallel running
integration tests before.

lntest/node/config.go

@@ -4,16 +4,16 @@ import (
 	"flag"
 	"fmt"
 	"io"
-	"net"
 	"os"
 	"path"
 	"path/filepath"
-	"sync/atomic"
 
 	"github.com/btcsuite/btcd/chaincfg"
+	"github.com/btcsuite/btcd/integration/rpctest"
 	"github.com/lightningnetwork/lnd"
 	"github.com/lightningnetwork/lnd/chanbackup"
 	"github.com/lightningnetwork/lnd/kvdb/etcd"
+	"github.com/lightningnetwork/lnd/lntest/port"
 	"github.com/lightningnetwork/lnd/lntest/wait"
 )
 
@@ -25,18 +25,9 @@ const (
 	// DefaultCSV is the CSV delay (remotedelay) we will start our test
 	// nodes with.
 	DefaultCSV = 4
-
-	// defaultNodePort is the start of the range for listening ports of
-	// harness nodes. Ports are monotonically increasing starting from this
-	// number and are determined by the results of NextAvailablePort().
-	defaultNodePort = 5555
 )
 
 var (
-	// lastPort is the last port determined to be free for use by a new
-	// node. It should be used atomically.
-	lastPort uint32 = defaultNodePort
-
 	// logOutput is a flag that can be set to append the output from the
 	// seed nodes to log files.
 	logOutput = flag.Bool("logoutput", false,
@@ -171,16 +162,16 @@ func (cfg BaseNodeConfig) ChanBackupPath() string {
 // current lightning network test.
 func (cfg *BaseNodeConfig) GenerateListeningPorts() {
 	if cfg.P2PPort == 0 {
-		cfg.P2PPort = NextAvailablePort()
+		cfg.P2PPort = port.NextAvailablePort()
 	}
 	if cfg.RPCPort == 0 {
-		cfg.RPCPort = NextAvailablePort()
+		cfg.RPCPort = port.NextAvailablePort()
 	}
 	if cfg.RESTPort == 0 {
-		cfg.RESTPort = NextAvailablePort()
+		cfg.RESTPort = port.NextAvailablePort()
 	}
 	if cfg.ProfilePort == 0 {
-		cfg.ProfilePort = NextAvailablePort()
+		cfg.ProfilePort = port.NextAvailablePort()
 	}
 }
 
@@ -259,13 +250,13 @@ func (cfg *BaseNodeConfig) GenArgs() []string {
 		args = append(
 			args, fmt.Sprintf(
 				"--db.etcd.embedded_client_port=%v",
-				NextAvailablePort(),
+				port.NextAvailablePort(),
 			),
 		)
 		args = append(
 			args, fmt.Sprintf(
 				"--db.etcd.embedded_peer_port=%v",
-				NextAvailablePort(),
+				port.NextAvailablePort(),
 			),
 		)
 		args = append(
@@ -333,34 +324,6 @@ func ExtraArgsEtcd(etcdCfg *etcd.Config, name string, cluster bool,
 	return extraArgs
 }
 
-// NextAvailablePort returns the first port that is available for listening by
-// a new node. It panics if no port is found and the maximum available TCP port
-// is reached.
-func NextAvailablePort() int {
-	port := atomic.AddUint32(&lastPort, 1)
-	for port < 65535 {
-		// If there are no errors while attempting to listen on this
-		// port, close the socket and return it as available. While it
-		// could be the case that some other process picks up this port
-		// between the time the socket is closed and it's reopened in
-		// the harness node, in practice in CI servers this seems much
-		// less likely than simply some other process already being
-		// bound at the start of the tests.
-		addr := fmt.Sprintf(ListenerFormat, port)
-		l, err := net.Listen("tcp4", addr)
-		if err == nil {
-			err := l.Close()
-			if err == nil {
-				return int(port)
-			}
-		}
-		port = atomic.AddUint32(&lastPort, 1)
-	}
-
-	// No ports available? Must be a mistake.
-	panic("no ports available for listening")
-}
-
 // GetLogDir returns the passed --logdir flag or the default value if it wasn't
 // set.
 func GetLogDir() string {
@@ -402,16 +365,10 @@ func GetBtcdBinary() string {
 	return ""
 }
 
-// GenerateBtcdListenerAddresses is a function that returns two listener
-// addresses with unique ports and should be used to overwrite rpctest's
-// default generator which is prone to use colliding ports.
-func GenerateBtcdListenerAddresses() (string, string) {
-	return fmt.Sprintf(ListenerFormat, NextAvailablePort()),
-		fmt.Sprintf(ListenerFormat, NextAvailablePort())
-}
-
-// ApplyPortOffset adds the given offset to the lastPort variable, making it
-// possible to run the tests in parallel without colliding on the same ports.
-func ApplyPortOffset(offset uint32) {
-	_ = atomic.AddUint32(&lastPort, offset)
+func init() {
+	// Before we start any node, we need to make sure that any btcd or
+	// bitcoind node that is started through the RPC harness uses a unique
+	// port as well to avoid any port collisions.
+	rpctest.ListenAddressGenerator =
+		port.GenerateSystemUniqueListenerAddresses
 }