net.i2p.router.transport.ntcp

Class NTCPTransport

java.lang.Object

net.i2p.router.transport.TransportImpl

net.i2p.router.transport.ntcp.NTCPTransport

All Implemented Interfaces:

Transport

public class NTCPTransport
extends TransportImpl

Non-blocking TCP (NTCP) transport implementation for I2P. This class provides the primary TCP-based transport for I2P communication using Java NIO for non-blocking I/O operations. It supports both NTCP 1 and NTCP 2 protocols with advanced features like connection pooling, bandwidth management, and sophisticated peer management. Protocol Features:

• NTCP 1: Basic encrypted TCP transport
• NTCP 2: Enhanced protocol with improved efficiency
• Configurable bandwidth limits and throttling
• Connection pooling and reuse
• IPv4 and IPv6 support
• Automatic protocol negotiation

Architecture:

• Non-blocking I/O with NIO channels
• Separate reader and writer threads
• Event-driven message processing
• Connection state machines for establishment
• Peer reputation and cost-based routing

Connection Management:

• Multiple bid tiers (fast, slow, high-cost)
• Connection pooling and reuse
• Automatic failover and retry logic
• Peer blacklisting and banlist support

Nested Class Summary

Nested classes/interfaces inherited from interface net.i2p.router.transport.Transport

Transport.AddressSource

Field Summary

Fields

Modifier and Type	Field and Description
static int	ESTABLISH_TIMEOUT how long from initial connection attempt (accept() or connect()) until the con must be established to avoid premature close()ing
static String	MIN_SIGTYPE_VERSION RI sigtypes supported in 0.9.16
(package private) static int	NTCP2_INT_VERSION
(package private) static String	NTCP2_VERSION "2"
(package private) static String	NTCP2_VERSION_ALT "2,"
static String	PROP_BIND_INTERFACE this is rarely if ever used, default is to bind to wildcard address
static String	PROP_I2NP_NTCP_AUTO_IP
static String	PROP_I2NP_NTCP_AUTO_PORT
static String	PROP_I2NP_NTCP_HOSTNAME
static String	PROP_I2NP_NTCP_PORT
static String	PROP_NTCP2_IV b64 static IV
static String	PROP_NTCP2_SP b64 static private key
static String	STYLE
static String	STYLE2

Fields inherited from class net.i2p.router.transport.TransportImpl

_context, ADJUST_COST, CAP_IPV4, CAP_IPV4_IPV6, CAP_IPV6, CONGESTION_COST_ADJUSTMENT, PROP_BOOST_CONNECTION_LIMITS, PROP_IPV6_FIREWALLED, PROP_THROTTLE_NTCP_ATTACK

Constructor Summary

Constructors

Constructor and Description
NTCPTransport(RouterContext ctx, X25519KeyFactory xdh)

Method Summary

Modifier and Type	Method and Description
void	afterSend(OutNetMessage msg, boolean sendSuccessful, boolean allowRequeue, long msToSend) The transport is done sending this message.
boolean	allowConnection()
TransportBid	bid(RouterInfo toAddress, int dataSize) Request to send a message to the specified router.
int	countActivePeers() How many peers have we talked to in the last minute? As of 0.9.20, actually returns active peer count, not total.
int	countActiveSendPeers() How many peers are we actively sending messages to (this minute)
int	countPeers() How many peers are we connected to?
(package private) void	establishing(NTCPConnection con) add us to the establishment timeout process
(package private) void	expireTimedOut() called in the EventPumper no more than once a second or so, closing any unconnected/unestablished connections
void	externalAddressReceived(Transport.AddressSource source, byte[] ip, int port) UDP changed addresses, tell NTCP and (possibly) restart
void	externalAddressRemoved(Transport.AddressSource source, boolean ipv6) Notify a transport of an external address change.
void	forceDisconnect(Hash peer) Tell the transport to disconnect from this peer.
void	forwardPortStatus(byte[] ip, int port, int externalPort, boolean success, String reason) If we didn't used to be forwarded, and we have an address, and we are configured to use UPnP, update our RouterAddress Don't do anything now.
String	getAltStyle() An alternate supported style
List<Long>	getClockSkews() Return our peer clock skews on this transport.
List<Hash>	getEstablished() Connected peers.
(package private) byte[]	getNTCP2StaticIV() The static IV
(package private) byte[]	getNTCP2StaticPrivkey() The static priv key
(package private) byte[]	getNTCP2StaticPubkey() The static priv key
int[]	getPeerCounts() Get detailed peer count statistics by IP version and direction.
Collection<NTCPConnection>	getPeers() For /peers UI only.
(package private) EventPumper	getPumper() Hook for NTCPConnection
CommSystemFacade.Status	getReachabilityStatus() Maybe we should trust UPnP here and report OK if it opened the port, but for now we don't.
(package private) Reader	getReader() Hook for NTCPConnection
int	getRequestedPort() What INTERNAL port would the transport like to have forwarded by UPnP.
String	getStyle() Get the unique style identifier for this transport.
(package private) Writer	getWriter() Hook for NTCPConnection
(package private) X25519KeyFactory	getXDHFactory()
(package private) NTCPConnection	inboundEstablished(NTCPConnection con) Registers a newly established inbound connection, replacing any existing connection for the same peer.
boolean	isAlive()
boolean	isBacklogged(Hash dest)
boolean	isEstablished(Hash dest)
(package private) boolean	isHXHIValid(byte[] hxhi) Incoming connection replay detection.
void	mayDisconnect(Hash peer) Tell the transport that we may disconnect from this peer.
protected void	outboundMessageReady() Processes the next outbound message by retrieving or creating a connection, preparing it for sending, and handling related failures or bans.
(package private) NTCPConnection	removeCon(NTCPConnection con)
(package private) void	sendComplete(OutNetMessage msg) queue up afterSend call, which can take some time w/ jobs, etc
(package private) void	setLastBadSkew(long skew) A positive number means our clock is ahead of theirs.
void	startListening() Starts the NTCP transport listening process, ensuring only one pumper is running by checking existing state since the caller may not stop the transport correctly.
void	stopListening() This doesn't (completely) block, caller should check isAlive() before calling startListening() or restartListening()

Methods inherited from class net.i2p.router.transport.TransportImpl

_t, _t, afterSend, afterSend, afterSend, allowLocal, getCurrentAddress, getCurrentAddresses, getIP, getIPv6Config, getMaxConnections, getMostRecentErrorMessages, getNextMessage, getSavedLocalAddresses, getTargetAddresses, getTransportMaxConnections, hasCurrentAddress, haveCapacity, haveCapacity, isIPv4Firewalled, isIPv6Firewalled, isPubliclyRoutable, isUnreachable, markReachable, markUnreachable, messageReceived, ngettext, removeAddress, removeAddress, renderStatusHTML, renderStatusHTML, replaceAddress, saveLocalAddress, send, setIP, setListener, updateAddress, wasUnreachable

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

ESTABLISH_TIMEOUT

public static final int ESTABLISH_TIMEOUT

how long from initial connection attempt (accept() or connect()) until the con must be established to avoid premature close()ing

See Also:

Constant Field Values

MIN_SIGTYPE_VERSION

public static final String MIN_SIGTYPE_VERSION

RI sigtypes supported in 0.9.16

See Also:

Constant Field Values

NTCP2_INT_VERSION

static final int NTCP2_INT_VERSION

See Also:

Constant Field Values

NTCP2_VERSION

static final String NTCP2_VERSION

"2"

NTCP2_VERSION_ALT

static final String NTCP2_VERSION_ALT

"2,"

PROP_BIND_INTERFACE

public static final String PROP_BIND_INTERFACE

this is rarely if ever used, default is to bind to wildcard address

See Also:

Constant Field Values

PROP_I2NP_NTCP_AUTO_IP

public static final String PROP_I2NP_NTCP_AUTO_IP

See Also:

Constant Field Values

PROP_I2NP_NTCP_AUTO_PORT

public static final String PROP_I2NP_NTCP_AUTO_PORT

See Also:

Constant Field Values

PROP_I2NP_NTCP_HOSTNAME

public static final String PROP_I2NP_NTCP_HOSTNAME

See Also:

Constant Field Values

PROP_I2NP_NTCP_PORT

public static final String PROP_I2NP_NTCP_PORT

See Also:

Constant Field Values

PROP_NTCP2_IV

public static final String PROP_NTCP2_IV

b64 static IV

See Also:

Constant Field Values

PROP_NTCP2_SP

public static final String PROP_NTCP2_SP

b64 static private key

See Also:

Constant Field Values

STYLE

public static final String STYLE

See Also:

Constant Field Values

STYLE2

public static final String STYLE2

See Also:

Constant Field Values

Constructor Detail

NTCPTransport

public NTCPTransport(RouterContext ctx,
                     X25519KeyFactory xdh)

Parameters:

xdh - null to disable NTCP2

Method Detail

afterSend

public void afterSend(OutNetMessage msg,
                      boolean sendSuccessful,
                      boolean allowRequeue,
                      long msToSend)

Description copied from class: TransportImpl

The transport is done sending this message. This is the method that actually does all of the cleanup - firing off jobs, requeueing, updating stats, etc.

Overrides:

afterSend in class TransportImpl

Parameters:

msg - message in question

sendSuccessful - true if the peer received it

allowRequeue - true if we should try other transports if available

msToSend - how long it took to transfer the data to the peer

allowConnection

public boolean allowConnection()

bid

public TransportBid bid(RouterInfo toAddress,
                        int dataSize)

Description copied from interface: Transport

Request to send a message to the specified router. This method allows the transport to evaluate whether it can and wants to send a message to the target router. The transport may decline based on current load, peer reputation, or transport-specific constraints.

Parameters:

toAddress - the target router's contact information

dataSize - size of message payload, assumes full 16-byte header, transports should adjust as necessary for their overhead

Returns:

a TransportBid containing send details, or null if unwilling to send

countActivePeers

public int countActivePeers()

How many peers have we talked to in the last minute? As of 0.9.20, actually returns active peer count, not total.

Specified by:

countActivePeers in interface Transport

Specified by:

countActivePeers in class TransportImpl

countActiveSendPeers

public int countActiveSendPeers()

How many peers are we actively sending messages to (this minute)

Specified by:

countActiveSendPeers in interface Transport

Specified by:

countActiveSendPeers in class TransportImpl

countPeers

public int countPeers()

Description copied from class: TransportImpl

How many peers are we connected to?

Specified by:

countPeers in interface Transport

Specified by:

countPeers in class TransportImpl

establishing

void establishing(NTCPConnection con)

add us to the establishment timeout process

expireTimedOut

void expireTimedOut()

called in the EventPumper no more than once a second or so, closing any unconnected/unestablished connections

externalAddressReceived

public void externalAddressReceived(Transport.AddressSource source,
                                    byte[] ip,
                                    int port)

UDP changed addresses, tell NTCP and (possibly) restart

Specified by:

externalAddressReceived in interface Transport

Specified by:

externalAddressReceived in class TransportImpl

Parameters:

ip - typ. IPv4 or IPv6 non-local; may be null to indicate IPv4 failure or port info only

source - defined in Transport.java

port - 0 for unknown or unchanged

externalAddressRemoved

public void externalAddressRemoved(Transport.AddressSource source,
                                   boolean ipv6)

Notify a transport of an external address change. This may be from a local interface, UPnP, a config change, etc. This should not be called if the ip didn't change (from that source's point of view), or is a local address. May be called multiple times for IPv4 or IPv6. The transport should also do its own checking on whether to accept notifications from this source. This can be called after the transport is running. TODO externalAddressRemoved(source, ip, port)

Specified by:

externalAddressRemoved in interface Transport

Overrides:

externalAddressRemoved in class TransportImpl

Parameters:

source - defined in Transport.java

ipv6 - true for IPv6, false for IPv4

forceDisconnect

public void forceDisconnect(Hash peer)

Tell the transport to disconnect from this peer.

Parameters:

peer - hash of the peer to forcefully disconnect from

forwardPortStatus

public void forwardPortStatus(byte[] ip,
                              int port,
                              int externalPort,
                              boolean success,
                              String reason)

If we didn't used to be forwarded, and we have an address, and we are configured to use UPnP, update our RouterAddress Don't do anything now. If it fails, we don't know if it's because there is no firewall, or if the firewall rejected the request. So we just use the SSU reachability status to decide whether to enable inbound NTCP. SSU will have CSFI build a new NTCP address when it transitions to OK.

Specified by:

forwardPortStatus in interface Transport

Overrides:

forwardPortStatus in class TransportImpl

Parameters:

ip - may be null

port - the internal port

externalPort - the external port, which for now should always be the same as the internal port if the forwarding was successful.

getAltStyle

public String getAltStyle()

An alternate supported style

Overrides:

getAltStyle in class TransportImpl

Returns:

"NTCP2" always

getClockSkews

public List<Long> getClockSkews()

Return our peer clock skews on this transport. List composed of Long, each element representing a peer skew in seconds. A positive number means our clock is ahead of theirs.

Specified by:

getClockSkews in interface Transport

Overrides:

getClockSkews in class TransportImpl

Returns:

list of clock skew measurements in milliseconds, may be empty if no measurements available

getEstablished

public List<Hash> getEstablished()

Connected peers.

Returns:

a copy, modifiable

getNTCP2StaticIV

byte[] getNTCP2StaticIV()

The static IV

getNTCP2StaticPrivkey

byte[] getNTCP2StaticPrivkey()

The static priv key

getNTCP2StaticPubkey

byte[] getNTCP2StaticPubkey()

The static priv key

getPeerCounts

public int[] getPeerCounts()

Description copied from interface: Transport

Get detailed peer count statistics by IP version and direction. This method returns an array containing peer counts broken down by IP version and connection direction. This provides detailed visibility into transport usage patterns and network composition. Array Format:

• Version 1 (8 bytes): IPv4 inbound/outbound counts
• Version 2 (8 bytes): IPv4 inbound/outbound, IPv6 inbound/outbound counts

Returns:

8 bytes: version 1 4 bytes all zeros version 2 ipv4 in/out, ipv6 in/out

getPeers

public Collection<NTCPConnection> getPeers()

For /peers UI only. Not a public API, not for external use.

Returns:

not a copy, do not modify

getPumper

EventPumper getPumper()

Hook for NTCPConnection

getReachabilityStatus

public CommSystemFacade.Status getReachabilityStatus()

Maybe we should trust UPnP here and report OK if it opened the port, but for now we don't. Just go through and if we have one inbound connection, we must be good. As we drop idle connections pretty quickly, this will be fairly accurate. We have to be careful here because much of the router console code assumes that the reachability status is really just the UDP status. This only returns OK, DISABLED, or UNKNOWN for IPv4 and IPv6. We leave the FIREWALLED status for UDP. Previously returned short, now enum as of 0.9.20

Specified by:

getReachabilityStatus in interface Transport

Specified by:

getReachabilityStatus in class TransportImpl

Returns:

current reachability status indicating transport's network accessibility

getReader

Reader getReader()

Hook for NTCPConnection

getRequestedPort

public int getRequestedPort()

Description copied from class: TransportImpl

What INTERNAL port would the transport like to have forwarded by UPnP. This can't be passed via getCurrentAddress(), as we have to open the port before we can publish the address, and that's the external port anyway.

Specified by:

getRequestedPort in interface Transport

Overrides:

getRequestedPort in class TransportImpl

Returns:

current IPv4 port, else NTCP configured port, else -1 (but not UDP port if auto)

getStyle

public String getStyle()

Description copied from interface: Transport

Get the unique style identifier for this transport. This method returns a string that uniquely identifies the transport type (e.g., "NTCP", "UDP", "SSU"). This is used for configuration, logging, and transport selection.

Returns:

always "NTCP"

getWriter

Writer getWriter()

Hook for NTCPConnection

getXDHFactory

X25519KeyFactory getXDHFactory()

Returns:

null if not configured for NTCP2

inboundEstablished

NTCPConnection inboundEstablished(NTCPConnection con)

Registers a newly established inbound connection, replacing any existing connection for the same peer. Updates reachability status and connection statistics.

Parameters:

con - The newly established NTCPConnection.

Returns:

The previous NTCPConnection to the same peer if one existed, or null otherwise.

isAlive

public boolean isAlive()

isBacklogged

public boolean isBacklogged(Hash dest)

Specified by:

isBacklogged in interface Transport

Overrides:

isBacklogged in class TransportImpl

isEstablished

public boolean isEstablished(Hash dest)

Specified by:

isEstablished in interface Transport

Overrides:

isEstablished in class TransportImpl

isHXHIValid

boolean isHXHIValid(byte[] hxhi)

Incoming connection replay detection. As there is no timestamp in the first message, we can't detect something long-delayed. To be fixed in next version of NTCP.

Parameters:

hxhi - using first 8 bytes only

Returns:

valid

mayDisconnect

public void mayDisconnect(Hash peer)

Tell the transport that we may disconnect from this peer. This is advisory only.

Specified by:

mayDisconnect in interface Transport

Overrides:

mayDisconnect in class TransportImpl

Parameters:

peer - hash of the peer that may be disconnected

outboundMessageReady

protected void outboundMessageReady()

Processes the next outbound message by retrieving or creating a connection, preparing it for sending, and handling related failures or bans.

Specified by:

outboundMessageReady in class TransportImpl

removeCon

NTCPConnection removeCon(NTCPConnection con)

Returns:

usually the con passed in, but possibly a second connection with the same peer... only con or null as of 0.9.37

sendComplete

void sendComplete(OutNetMessage msg)

queue up afterSend call, which can take some time w/ jobs, etc

setLastBadSkew

void setLastBadSkew(long skew)

A positive number means our clock is ahead of theirs.

Parameters:

skew - in seconds

startListening

public void startListening()

Starts the NTCP transport listening process, ensuring only one pumper is running by checking existing state since the caller may not stop the transport correctly. It configures and binds local addresses, handles firewall and network interface settings, and sets fallback addresses as needed. This method is synchronized to prevent concurrent starts.

stopListening

public void stopListening()

This doesn't (completely) block, caller should check isAlive() before calling startListening() or restartListening()