net.i2p.router.transport.udp

Class PacketBuilder2

java.lang.Object

net.i2p.router.transport.udp.PacketBuilder2

class PacketBuilder2
extends Object

Builds and encrypts SSU2 protocol packets for UDP transport. Handles all SSU2 message types including data packets, session establishment, peer testing, relay requests, and hole punching. Provides packet fragmentation, padding, and encryption for secure UDP communication.

Field Summary

Fields

Modifier and Type	Field and Description
static int	IP_HEADER_SIZE IPv4 only
static int	IPV6_HEADER_SIZE
static int	MIN_DATA_PACKET_OVERHEAD 60
static int	MIN_IPV6_DATA_PACKET_OVERHEAD 80
(package private) static int	PRIORITY_HIGH
(package private) static int	TYPE_ACK
(package private) static int	TYPE_CONF
(package private) static int	TYPE_CREAT
(package private) static int	TYPE_DESTROY
(package private) static int	TYPE_FIRST For debugging and stats only - does not go out on the wire.
(package private) static int	TYPE_INTRO
(package private) static int	TYPE_PUNCH
(package private) static int	TYPE_RESP
(package private) static int	TYPE_RREQ
(package private) static int	TYPE_SREQ
(package private) static int	TYPE_TBC
(package private) static int	TYPE_TCB
(package private) static int	TYPE_TFA
(package private) static int	TYPE_TTA
static int	UDP_HEADER_SIZE Same for IPv4 and IPv6

Constructor Summary

Constructors

Constructor and Description
PacketBuilder2(RouterContext ctx, UDPTransport transport) No state, all methods are thread-safe.

Method Summary

Modifier and Type	Method and Description
UDPPacket	buildACK(PeerState2 peer) Build the ack packet.
UDPPacket	buildHolePunch(InetAddress to, int port, SessionKey introKey, long sendID, long rcvID, byte[] signedData) Out-of-session, containing a RelayResponse block.
UDPPacket	buildPacket(List<PacketBuilder.Fragment> fragments, List<SSU2Payload.Block> otherBlocks, SSU2Sender peer)
UDPPacket	buildPacket(List<PacketBuilder.Fragment> fragments, PeerState2 peer)
UDPPacket	buildPacket(OutboundMessageState state, int fragment, PeerState2 peer) This builds a data packet (PAYLOAD_TYPE_DATA).
UDPPacket	buildPeerTestFromAlice(byte[] signedData, PeerState2 bob) Build a packet as Alice, to Bob to begin a peer test.
UDPPacket	buildPeerTestFromAlice(InetAddress toIP, int toPort, SessionKey introKey, long sendID, long rcvID, byte[] signedData) Build a packet as Alice to Charlie.
UDPPacket	buildPeerTestToAlice(InetAddress aliceIP, int alicePort, SessionKey introKey, boolean firstSend, long sendID, long rcvID, byte[] signedData) Build a packet as Charlie to Alice.
UDPPacket	buildPeerTestToAlice(int code, Hash charlieHash, byte[] signedData, PeerState2 alice) Build a packet as Bob to Alice, with the response from Charlie, or a rejection by Bob.
UDPPacket	buildPeerTestToAlice(int code, Hash charlieHash, byte[] signedData, SSU2Payload.Block riBlock, PeerState2 alice) Build a packet as Bob to Alice, with the response from Charlie, or a rejection by Bob.
UDPPacket	buildPeerTestToBob(int code, byte[] signedData, PeerState2 bob) Build a packet as Charlie to Bob verifying that we will help test Alice.
UDPPacket	buildPeerTestToCharlie(Hash aliceHash, byte[] signedData, SSU2Payload.Block riBlock, PeerState2 charlie) Build a packet as Bob to Charlie to help test Alice.
UDPPacket	buildPing(PeerState2 peer) A DATA packet with padding only.
(package private) UDPPacket	buildRelayIntro(byte[] signedData, SSU2Payload.Block riBlock, PeerState2 charlie) From Bob to Charlie.
(package private) UDPPacket	buildRelayRequest(byte[] signedData, PeerState2 bob) From Alice to Bob.
(package private) UDPPacket	buildRelayResponse(byte[] signedData, PeerState2 state) From Charlie to Bob or Bob to Alice.
UDPPacket	buildRetryPacket(InboundEstablishState2 state, int terminationCode) Build a new Retry packet for the given peer, encrypting it as necessary.
UDPPacket	buildRetryPacket(RemoteHostId to, SocketAddress toAddr, long destID, long srcID, int terminationCode) Build a new Retry packet with a termination code, for a rejection direct from the EstablishmentManager.
UDPPacket[]	buildSessionConfirmedPackets(OutboundEstablishState2 state, RouterInfo ourInfo) Build a new series of SessionConfirmed packets for the given peer, encrypting it as necessary.
UDPPacket	buildSessionCreatedPacket(InboundEstablishState2 state) Build a new SessionCreated packet for the given peer, encrypting it as necessary.
UDPPacket	buildSessionDestroyPacket(int reason, SSU2Sender peer) Build a data packet with a termination block.
UDPPacket	buildSessionRequestPacket(OutboundEstablishState2 state) Build a new SessionRequest packet for the given peer, encrypting it as necessary.
UDPPacket	buildTokenRequestPacket(OutboundEstablishState2 state) Build a new SessionRequest packet for the given peer, encrypting it as necessary.
static int	getMaxAdditionalFragmentSize(PeerState peer, int numFragments, int curDataSize) Will a packet to 'peer' that already has 'numFragments' fragments totalling 'curDataSize' bytes fit another fragment? This includes the 3 byte block overhead, but NOT the 5 byte followon fragment overhead.
static int	getMaxDataSize(PeerState peer) Calculates the maximum payload size that can be sent to this peer in a single data packet.

Methods inherited from class java.lang.Object

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

Field Detail

IP_HEADER_SIZE

public static final int IP_HEADER_SIZE

IPv4 only

See Also:

Constant Field Values

IPV6_HEADER_SIZE

public static final int IPV6_HEADER_SIZE

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Constant Field Values

MIN_DATA_PACKET_OVERHEAD

public static final int MIN_DATA_PACKET_OVERHEAD

60

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Constant Field Values

MIN_IPV6_DATA_PACKET_OVERHEAD

public static final int MIN_IPV6_DATA_PACKET_OVERHEAD

80

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Constant Field Values

PRIORITY_HIGH

static final int PRIORITY_HIGH

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Constant Field Values

TYPE_ACK

static final int TYPE_ACK

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Constant Field Values

TYPE_CONF

static final int TYPE_CONF

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Constant Field Values

TYPE_CREAT

static final int TYPE_CREAT

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Constant Field Values

TYPE_DESTROY

static final int TYPE_DESTROY

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Constant Field Values

TYPE_FIRST

static final int TYPE_FIRST

For debugging and stats only - does not go out on the wire. These are chosen to be higher than the highest I2NP message type, as a data packet is set to the underlying I2NP message type.

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Constant Field Values

TYPE_INTRO

static final int TYPE_INTRO

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Constant Field Values

TYPE_PUNCH

static final int TYPE_PUNCH

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Constant Field Values

TYPE_RESP

static final int TYPE_RESP

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Constant Field Values

TYPE_RREQ

static final int TYPE_RREQ

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Constant Field Values

TYPE_SREQ

static final int TYPE_SREQ

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Constant Field Values

TYPE_TBC

static final int TYPE_TBC

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Constant Field Values

TYPE_TCB

static final int TYPE_TCB

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Constant Field Values

TYPE_TFA

static final int TYPE_TFA

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Constant Field Values

TYPE_TTA

static final int TYPE_TTA

See Also:

Constant Field Values

UDP_HEADER_SIZE

public static final int UDP_HEADER_SIZE

Same for IPv4 and IPv6

See Also:

Constant Field Values

Constructor Detail

PacketBuilder2

public PacketBuilder2(RouterContext ctx,
                      UDPTransport transport)

No state, all methods are thread-safe.

Parameters:

transport - may be null for unit testing only

Method Detail

buildACK

public UDPPacket buildACK(PeerState2 peer)
                   throws IOException

Build the ack packet. An ack packet is just a data packet with no data. See buildPacket() for format.

Throws:

IOException - if peer is dead

buildHolePunch

public UDPPacket buildHolePunch(InetAddress to,
                                int port,
                                SessionKey introKey,
                                long sendID,
                                long rcvID,
                                byte[] signedData)

Out-of-session, containing a RelayResponse block.

buildPacket

public UDPPacket buildPacket(List<PacketBuilder.Fragment> fragments,
                             List<SSU2Payload.Block> otherBlocks,
                             SSU2Sender peer)
                      throws IOException

Throws:

IOException

buildPacket

public UDPPacket buildPacket(List<PacketBuilder.Fragment> fragments,
                             PeerState2 peer)
                      throws IOException

Throws:

IOException

buildPacket

public UDPPacket buildPacket(OutboundMessageState state,
                             int fragment,
                             PeerState2 peer)
                      throws IOException

This builds a data packet (PAYLOAD_TYPE_DATA). See the methods below for the other message types. Note that while the UDP message spec allows for more than one fragment in a message, this method writes exactly one fragment. For no fragments use buildAck().

Throws:

IOException - if peer is dead

buildPeerTestFromAlice

public UDPPacket buildPeerTestFromAlice(byte[] signedData,
                                        PeerState2 bob)
                                 throws IOException

Build a packet as Alice, to Bob to begin a peer test. In-session, message 1.

Returns:

ready to send packet, non-null

Throws:

IOException - if peer is dead

buildPeerTestFromAlice

public UDPPacket buildPeerTestFromAlice(InetAddress toIP,
                                        int toPort,
                                        SessionKey introKey,
                                        long sendID,
                                        long rcvID,
                                        byte[] signedData)

Build a packet as Alice to Charlie. Out-of-session, message 6.

Returns:

ready to send packet, non-null

buildPeerTestToAlice

public UDPPacket buildPeerTestToAlice(InetAddress aliceIP,
                                      int alicePort,
                                      SessionKey introKey,
                                      boolean firstSend,
                                      long sendID,
                                      long rcvID,
                                      byte[] signedData)

Build a packet as Charlie to Alice. Out-of-session, messages 5 and 7.

Returns:

ready to send packet, non-null

buildPeerTestToAlice

public UDPPacket buildPeerTestToAlice(int code,
                                      Hash charlieHash,
                                      byte[] signedData,
                                      PeerState2 alice)
                               throws IOException

Build a packet as Bob to Alice, with the response from Charlie, or a rejection by Bob. In-session, message 4.

Parameters:

charlieHash - fake hash (all zeros) if rejected by bob

Returns:

ready to send packet, non-null

Throws:

IOException - if peer is dead

buildPeerTestToAlice

public UDPPacket buildPeerTestToAlice(int code,
                                      Hash charlieHash,
                                      byte[] signedData,
                                      SSU2Payload.Block riBlock,
                                      PeerState2 alice)
                               throws IOException

Build a packet as Bob to Alice, with the response from Charlie, or a rejection by Bob. In-session, message 4.

Parameters:

charlieHash - fake hash (all zeros) if rejected by bob

riBlock - to include, may be null

Returns:

ready to send packet, non-null

Throws:

IOException - if peer is dead

buildPeerTestToBob

public UDPPacket buildPeerTestToBob(int code,
                                    byte[] signedData,
                                    PeerState2 bob)
                             throws IOException

Build a packet as Charlie to Bob verifying that we will help test Alice. In-session, message 3.

Returns:

ready to send packet, non-null

Throws:

IOException - if peer is dead

buildPeerTestToCharlie

public UDPPacket buildPeerTestToCharlie(Hash aliceHash,
                                        byte[] signedData,
                                        SSU2Payload.Block riBlock,
                                        PeerState2 charlie)
                                 throws IOException

Build a packet as Bob to Charlie to help test Alice. In-session, message 2.

Parameters:

riBlock - to include, may be null

Returns:

ready to send packet, non-null

Throws:

IOException - if peer is dead

buildPing

public UDPPacket buildPing(PeerState2 peer)
                    throws IOException

A DATA packet with padding only. We use this for keepalive purposes.

Throws:

IOException - if peer is dead

buildRelayIntro

UDPPacket buildRelayIntro(byte[] signedData,
                          SSU2Payload.Block riBlock,
                          PeerState2 charlie)
                   throws IOException

From Bob to Charlie. In-session.

Parameters:

signedData - flag + alice hash + signed data

riBlock - to include, may be null

Returns:

non-null

Throws:

IOException - if peer is dead

buildRelayRequest

UDPPacket buildRelayRequest(byte[] signedData,
                            PeerState2 bob)
                     throws IOException

From Alice to Bob. In-session.

Parameters:

signedData - flag + signed data

Returns:

non-null

Throws:

IOException - if peer is dead

buildRelayResponse

UDPPacket buildRelayResponse(byte[] signedData,
                             PeerState2 state)
                      throws IOException

From Charlie to Bob or Bob to Alice. In-session.

Parameters:

signedData - flag + response code + signed data + optional token

state - Alice or Bob

Returns:

non-null

Throws:

IOException - if peer is dead

buildRetryPacket

public UDPPacket buildRetryPacket(InboundEstablishState2 state,
                                  int terminationCode)

Build a new Retry packet for the given peer, encrypting it as necessary.

Parameters:

terminationCode - 0 normally, nonzero to send termination block

Returns:

ready to send packet, non-null

buildRetryPacket

public UDPPacket buildRetryPacket(RemoteHostId to,
                                  SocketAddress toAddr,
                                  long destID,
                                  long srcID,
                                  int terminationCode)

Build a new Retry packet with a termination code, for a rejection direct from the EstablishmentManager. No InboundEstablishState2 required.

Parameters:

terminationCode - must be greater than zero

Returns:

ready to send packet, non-null

buildSessionConfirmedPackets

public UDPPacket[] buildSessionConfirmedPackets(OutboundEstablishState2 state,
                                                RouterInfo ourInfo)

Build a new series of SessionConfirmed packets for the given peer, encrypting it as necessary. If the RI is large enough that it is fragmented, this will still only return a single Session Confirmed message. The remaining RI blocks will be passed to the establish state via confirmedPacketsSent(), and the state will transmit them via the new PeerState2.

Returns:

ready to send packets, non-null

buildSessionCreatedPacket

public UDPPacket buildSessionCreatedPacket(InboundEstablishState2 state)

Build a new SessionCreated packet for the given peer, encrypting it as necessary.

Returns:

ready to send packet, non-null

buildSessionDestroyPacket

public UDPPacket buildSessionDestroyPacket(int reason,
                                           SSU2Sender peer)
                                    throws IOException

Build a data packet with a termination block. This will also include acks, a new token block, and padding.

Throws:

IOException - if peer is dead

buildSessionRequestPacket

public UDPPacket buildSessionRequestPacket(OutboundEstablishState2 state)

Build a new SessionRequest packet for the given peer, encrypting it as necessary.

Returns:

ready to send packet, non-null

buildTokenRequestPacket

public UDPPacket buildTokenRequestPacket(OutboundEstablishState2 state)

Build a new SessionRequest packet for the given peer, encrypting it as necessary.

Returns:

ready to send packet, non-null

getMaxAdditionalFragmentSize

public static int getMaxAdditionalFragmentSize(PeerState peer,
                                               int numFragments,
                                               int curDataSize)

Will a packet to 'peer' that already has 'numFragments' fragments totalling 'curDataSize' bytes fit another fragment? This includes the 3 byte block overhead, but NOT the 5 byte followon fragment overhead. This doesn't leave anything for acks or anything else.

Parameters:

numFragments - >= 1

Returns:

max additional fragment size

getMaxDataSize

public static int getMaxDataSize(PeerState peer)

Calculates the maximum payload size that can be sent to this peer in a single data packet.