added --p2p.allowed-port flag (#6263)

Regarding https://github.com/ledgerwatch/erigon/issues/6260

added flag `--p2p.allowed-ports=<porta>,<portb>` to restrict which ports
to use for sentries for different protocol versions.

Default for this flag is `30303, 30304` (first port is inherited from
`--port` flag defaults.
If `--port` is changed and it's new value is not presented in allowed
port list, provided port will be allowed as well as list provided via
`--p2p.allowed-ports`

Port picking is straightforward, we create sentry gRPC server for
protocol over first allowed port that is not already taken.
If there are no allowed ports left, erigon exits with hint.

cmd/sentry/main.go

@@ -28,6 +28,7 @@ var (
 	discoveryDNS []string
 	nodiscover   bool // disable sentry's discovery mechanism
 	protocol     uint
+	allowedPorts []uint
 	netRestrict  string // CIDR to restrict peering to
 	maxPeers     int
 	maxPendPeers int
@@ -46,6 +47,7 @@ func init() {
 	rootCmd.Flags().StringSliceVar(&discoveryDNS, utils.DNSDiscoveryFlag.Name, []string{}, utils.DNSDiscoveryFlag.Usage)
 	rootCmd.Flags().BoolVar(&nodiscover, utils.NoDiscoverFlag.Name, false, utils.NoDiscoverFlag.Usage)
 	rootCmd.Flags().UintVar(&protocol, utils.P2pProtocolVersionFlag.Name, utils.P2pProtocolVersionFlag.Value.Value()[0], utils.P2pProtocolVersionFlag.Usage)
+	rootCmd.Flags().UintSliceVar(&allowedPorts, utils.P2pProtocolAllowedPorts.Name, utils.P2pProtocolAllowedPorts.Value.Value(), utils.P2pProtocolAllowedPorts.Usage)
 	rootCmd.Flags().StringVar(&netRestrict, utils.NetrestrictFlag.Name, utils.NetrestrictFlag.Value, utils.NetrestrictFlag.Usage)
 	rootCmd.Flags().IntVar(&maxPeers, utils.MaxPeersFlag.Name, utils.MaxPeersFlag.Value, utils.MaxPeersFlag.Usage)
 	rootCmd.Flags().IntVar(&maxPendPeers, utils.MaxPendingPeersFlag.Name, utils.MaxPendingPeersFlag.Value, utils.MaxPendingPeersFlag.Usage)
@@ -82,6 +84,7 @@ var rootCmd = &cobra.Command{
 			trustedPeers,
 			uint(port),
 			protocol,
+			allowedPorts,
 		)
 		if err != nil {
 			return err

cmd/utils/flags.go

@@ -478,6 +478,11 @@ var (
 		Usage: "Version of eth p2p protocol",
 		Value: cli.NewUintSlice(nodecfg.DefaultConfig.P2P.ProtocolVersion...),
 	}
+	P2pProtocolAllowedPorts = cli.UintSliceFlag{
+		Name:  "p2p.allowed-ports",
+		Usage: "Allowed ports to pick for different eth p2p protocol versions as follows <porta>,<portb>,..,<porti>",
+		Value: cli.NewUintSlice(uint(ListenPortFlag.Value), 30304, 30305, 30306, 30307),
+	}
 	SentryAddrFlag = cli.StringFlag{
 		Name:  "sentry.api.addr",
 		Usage: "comma separated sentry addresses '<host>:<port>,<host>:<port>'",
@@ -850,6 +855,7 @@ func NewP2PConfig(
 	trustedPeers []string,
 	port,
 	protocol uint,
+	allowedPorts []uint,
 ) (*p2p.Config, error) {
 	var enodeDBPath string
 	switch protocol {
@@ -876,6 +882,7 @@ func NewP2PConfig(
 		Name:            nodeName,
 		Log:             log.New(),
 		NodeDatabase:    enodeDBPath,
+		AllowedPorts:    allowedPorts,
 	}
 	if netRestrict != "" {
 		cfg.NetRestrict = new(netutil.Netlist)
@@ -923,6 +930,26 @@ func setListenAddress(ctx *cli.Context, cfg *p2p.Config) {
 	if ctx.IsSet(SentryAddrFlag.Name) {
 		cfg.SentryAddr = SplitAndTrim(ctx.String(SentryAddrFlag.Name))
 	}
+	// TODO cli lib doesn't store defaults for UintSlice properly so we have to get value directly
+	cfg.AllowedPorts = P2pProtocolAllowedPorts.Value.Value()
+	if ctx.IsSet(P2pProtocolAllowedPorts.Name) {
+		cfg.AllowedPorts = ctx.UintSlice(P2pProtocolAllowedPorts.Name)
+	}
+
+	if ctx.IsSet(ListenPortFlag.Name) {
+		// add non-default port to allowed port list
+		lp := ctx.Int(ListenPortFlag.Name)
+		found := false
+		for _, p := range cfg.AllowedPorts {
+			if int(p) == lp {
+				found = true
+				break
+			}
+		}
+		if !found {
+			cfg.AllowedPorts = append([]uint{uint(lp)}, cfg.AllowedPorts...)
+		}
+	}
 }
 
 // setNAT creates a port mapper from command line flags.

eth/backend.go

@@ -23,6 +23,7 @@ import (
 	"fmt"
 	"io/fs"
 	"math/big"
+	"net"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -316,11 +317,31 @@ func New(stack *node.Node, config *ethconfig.Config, logger log.Logger) (*Ethere
 		if err != nil {
 			return nil, err
 		}
+
+		var pi int // points to next port to be picked from refCfg.AllowedPorts
 		for _, protocol := range refCfg.ProtocolVersion {
 			cfg := refCfg
 			cfg.NodeDatabase = filepath.Join(stack.Config().Dirs.Nodes, eth.ProtocolToString[protocol])
+
+			// pick port from allowed list
+			var picked bool
+			for ; pi < len(refCfg.AllowedPorts) && !picked; pi++ {
+				pc := int(refCfg.AllowedPorts[pi])
+				if !checkPortIsFree(fmt.Sprintf("%s:%d", listenHost, pc)) {
+					log.Warn("bind protocol to port has failed: port is busy", "protocol", fmt.Sprintf("eth/%d", protocol), "port", pc)
+					continue
+				}
+				if listenPort != pc {
+					listenPort = pc
+				}
+				pi++
+				picked = true
+			}
+			if !picked {
+				return nil, fmt.Errorf("run out of allowed ports for p2p eth protocols %v. Extend allowed port list via --p2p.allowed-ports", cfg.AllowedPorts)
+			}
+
 			cfg.ListenAddr = fmt.Sprintf("%s:%d", listenHost, listenPort)
-			listenPort++
 
 			server := sentry.NewGrpcServer(backend.sentryCtx, discovery, readNodeInfo, &cfg, protocol)
 			backend.sentryServers = append(backend.sentryServers, server)
@@ -1066,3 +1087,12 @@ func RemoveContents(dir string) error {
 	}
 	return nil
 }
+
+func checkPortIsFree(addr string) (free bool) {
+	c, err := net.DialTimeout("tcp", addr, 200*time.Millisecond)
+	if err != nil {
+		return true
+	}
+	c.Close()
+	return false
+}

p2p/server.go

@@ -139,6 +139,10 @@ type Config struct {
 	// the server is started.
 	ListenAddr string
 
+	// AllowedPorts is list of ports allowed to pick to create Listener on it (see ListenAddr)
+	// for different protocol versions
+	AllowedPorts []uint
+
 	// eth/66, eth/67, etc
 	ProtocolVersion []uint
 

turbo/cli/default_flags.go

@@ -91,6 +91,7 @@ var DefaultFlags = []cli.Flag{
 	&utils.TorrentVerbosityFlag,
 	&utils.ListenPortFlag,
 	&utils.P2pProtocolVersionFlag,
+	&utils.P2pProtocolAllowedPorts,
 	&utils.NATFlag,
 	&utils.NoDiscoverFlag,
 	&utils.DiscoveryV5Flag,