package net.i2p.router.transport.udp;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.net.UnknownHostException;
import java.security.GeneralSecurityException;
import java.util.Arrays;
import java.util.ArrayList;
import java.util.List;

import com.southernstorm.noise.protocol.ChaChaPolyCipherState;
import com.southernstorm.noise.protocol.CipherState;
import com.southernstorm.noise.protocol.CipherStatePair;
import com.southernstorm.noise.protocol.HandshakeState;

import net.i2p.crypto.HKDF;
import net.i2p.data.Base64;
import net.i2p.data.DataFormatException;
import net.i2p.data.DataHelper;
import net.i2p.data.Hash;
import net.i2p.data.SessionKey;
import net.i2p.data.i2np.I2NPMessage;
import net.i2p.data.router.RouterAddress;
import net.i2p.data.router.RouterInfo;
import net.i2p.router.Router;
import net.i2p.router.RouterContext;
import net.i2p.router.networkdb.kademlia.FloodfillNetworkDatabaseFacade;
import net.i2p.router.transport.TransportImpl;
import static net.i2p.router.transport.udp.SSU2Util.*;
import net.i2p.util.Addresses;
import net.i2p.util.Log;
import net.i2p.util.VersionComparator;

/**
 * Data for a new connection being established, where the remote peer has
 * initiated the connection with us.  In other words, they are Alice and
 * we are Bob.
 *
 * SSU2 only.
 *
 * @since 0.9.54
 */
class InboundEstablishState2 extends InboundEstablishState implements SSU2Payload.PayloadCallback {
    private final UDPTransport _transport;
    private final InetSocketAddress _aliceSocketAddress;
    private final long _rcvConnID;
    private final long _sendConnID;
    private final long _token;
    private final HandshakeState _handshakeState;
    private byte[] _sendHeaderEncryptKey1;
    private byte[] _sendHeaderEncryptKey2;
    private byte[] _rcvHeaderEncryptKey2;
    private byte[] _sessCrForReTX;
    private byte[][] _sessConfFragments;
    private long _timeReceived;
    // not adjusted for RTT
    private long _skew;
    private int _mtu;
    private PeerState2 _pstate;
    private List<UDPPacket> _queuedDataPackets;
    
    // testing
    private static final boolean ENFORCE_TOKEN = true;
    private static final long MAX_SKEW = 2*60*1000L;
    // SSU2 fixes (2.1.0)
    private static final String MIN_RELAY_VERSION = "0.9.57";


    /**
     *  Start a new handshake with the given incoming packet,
     *  which must be a Session Request or Token Request.
     *
     *  Caller must then check getState() and build a
     *  Retry or Session Created in response.
     *
     *  @param packet with all header encryption removed,
     *                either a SessionRequest OR a TokenRequest.
     */
    public InboundEstablishState2(RouterContext ctx, UDPTransport transport,
                                  UDPPacket packet) throws GeneralSecurityException {
        super(ctx, (InetSocketAddress) packet.getPacket().getSocketAddress());
        _transport = transport;
        DatagramPacket pkt = packet.getPacket();
        _aliceSocketAddress = (InetSocketAddress) pkt.getSocketAddress();
        _handshakeState = new HandshakeState(HandshakeState.PATTERN_ID_XK_SSU2, HandshakeState.RESPONDER, transport.getXDHFactory());
        _handshakeState.getLocalKeyPair().setKeys(transport.getSSU2StaticPrivKey(), 0,
                                                  transport.getSSU2StaticPubKey(), 0);
        byte[] introKey = transport.getSSU2StaticIntroKey();
        _sendHeaderEncryptKey1 = introKey;
        //_sendHeaderEncryptKey2 set below
        //_rcvHeaderEncryptKey2 set below
        int off = pkt.getOffset();
        int len = pkt.getLength();
        byte data[] = pkt.getData();
        _rcvConnID = DataHelper.fromLong8(data, off);
        _sendConnID = DataHelper.fromLong8(data, off + SRC_CONN_ID_OFFSET);
        if (_rcvConnID == _sendConnID)
            throw new GeneralSecurityException("Identical Conn IDs");
        int type = data[off + TYPE_OFFSET] & 0xff;
        long token = DataHelper.fromLong8(data, off + TOKEN_OFFSET);
        if (type == TOKEN_REQUEST_FLAG_BYTE) {
            if (_log.shouldDebug())
                _log.debug("Got token request from: " + _aliceSocketAddress);
            _currentState = InboundState.IB_STATE_TOKEN_REQUEST_RECEIVED;
            // decrypt in-place
            ChaChaPolyCipherState chacha = new ChaChaPolyCipherState();
            chacha.initializeKey(introKey, 0);
            long n = DataHelper.fromLong(data, off + PKT_NUM_OFFSET, 4);
            chacha.setNonce(n);
            chacha.decryptWithAd(data, off, LONG_HEADER_SIZE,
                                 data, off + LONG_HEADER_SIZE, data, off + LONG_HEADER_SIZE, len - LONG_HEADER_SIZE);
            chacha.destroy();
            processPayload(data, off + LONG_HEADER_SIZE, len - (LONG_HEADER_SIZE + MAC_LEN), true);
            _sendHeaderEncryptKey2 = introKey;
            do {
                token = ctx.random().nextLong();
            } while (token == 0);
            _token = token;
        } else if (type == SESSION_REQUEST_FLAG_BYTE &&
                   (token == 0 ||
                    (ENFORCE_TOKEN && !_transport.getEstablisher().isInboundTokenValid(_remoteHostId, token)))) {
            // i2pd thru 0.9.55 ignores zero token + termination in retry
            if (_log.shouldInfo())
                _log.info("Invalid token " + token + " in session request from: " + _aliceSocketAddress);
            if (token == 0)
                throw new GeneralSecurityException("Zero token in session request from: " + _aliceSocketAddress);
            _currentState = InboundState.IB_STATE_REQUEST_BAD_TOKEN_RECEIVED;
            _sendHeaderEncryptKey2 = introKey;
            // Generate token for the retry.
            // We do NOT register it with the EstablishmentManager, it must be used immediately.
            do {
                token = ctx.random().nextLong();
            } while (token == 0);
            _token = token;
            // do NOT bother to init the handshake state and decrypt the payload
            _timeReceived = _establishBegin;
        } else {
            // fast MSB check for key < 2^255
            if ((data[off + LONG_HEADER_SIZE + KEY_LEN - 1] & 0x80) != 0)
                throw new GeneralSecurityException("Bad PK msg 1");
            // probably don't need again
            _token = token;
            _handshakeState.start();
            //if (_log.shouldDebug())
            //    _log.debug("State after start: " + _handshakeState);
            _handshakeState.mixHash(data, off, LONG_HEADER_SIZE);
            //if (_log.shouldDebug())
            //    _log.debug("State after mixHash 1: " + _handshakeState);

            // decrypt in-place
            try {
                _handshakeState.readMessage(data, off + LONG_HEADER_SIZE, len - LONG_HEADER_SIZE, data, off + LONG_HEADER_SIZE);
            } catch (GeneralSecurityException gse) {
                if (_log.shouldDebug())
                    _log.debug("Session request error, State at failure: " + _handshakeState + '\n' + net.i2p.util.HexDump.dump(data, off, len), gse);
                throw gse;
            }
            //if (_log.shouldDebug())
            //    _log.debug("State after sess req: " + _handshakeState);
            processPayload(data, off + LONG_HEADER_SIZE, len - (LONG_HEADER_SIZE + KEY_LEN + MAC_LEN), true);
            _sendHeaderEncryptKey2 = SSU2Util.hkdf(_context, _handshakeState.getChainingKey(), "SessCreateHeader");
            _currentState = InboundState.IB_STATE_REQUEST_RECEIVED;
        }
        if (_currentState == InboundState.IB_STATE_FAILED) {
            // termination block received
            throw new GeneralSecurityException("Termination block in Session/Token Request");
        }
        if (_timeReceived == 0) {
            _currentState = InboundState.IB_STATE_FAILED;
            throw new GeneralSecurityException("No DateTime block in Session/Token Request");
        }
        _skew = _establishBegin - _timeReceived;
        if (_skew > MAX_SKEW || _skew < 0 - MAX_SKEW) {
            _currentState = InboundState.IB_STATE_FAILED;
            // send retry with termination
            UDPPacket retry = _transport.getBuilder2().buildRetryPacket(this, SSU2Util.REASON_SKEW);
            _transport.send(retry);
            throw new GeneralSecurityException("Skew exceeded in Session/Token Request (retry sent): " + _skew);
        }
        packetReceived();
        if (_log.shouldDebug())
            _log.debug("New req type " + type + " len " + len + " on " + this);
    }

    @Override
    public int getVersion() { return 2; }
    
    private void processPayload(byte[] payload, int offset, int length, boolean isHandshake) throws GeneralSecurityException {
        try {
            int blocks = SSU2Payload.processPayload(_context, this, payload, offset, length, isHandshake, null);
            if (_log.shouldDebug())
                _log.debug("Processed " + blocks + " blocks on " + this);
        } catch (RIException rie) {
            if (_log.shouldWarn())
                _log.warn("RouterInfo error: " + rie.getMessage());
            int reason = rie.getReason();
            PeerStateDestroyed psd = createPeerStateDestroyed(reason);
            _transport.addRecentlyClosed(psd);
            try {
                UDPPacket pkt = _transport.getBuilder2().buildSessionDestroyPacket(reason, psd);
                _transport.send(pkt);
                if (_log.shouldWarn()) {
                    if (_log.shouldDebug())
                        _log.debug("Sending TERMINATION reason " + reason + " to " + psd);
                    _log.warn("IES2 payload error", rie);
                }
            } catch (IOException ioe) {}
            throw new GeneralSecurityException("IES2 payload error: " + this, rie);
        } catch (DataFormatException dfe) {
            // no in-session response possible
            if (_log.shouldWarn())
                _log.warn("IES2 payload error", dfe);
            throw new GeneralSecurityException("IES2 payload error: " + this, dfe);
        } catch (Exception e) {
            if (_log.shouldWarn())
                _log.warn("IES2 payload error\n" + net.i2p.util.HexDump.dump(payload, 0, length), e);
            throw new GeneralSecurityException("IES2 payload error", e);
        }
    }

    /////////////////////////////////////////////////////////
    // begin payload callbacks
    /////////////////////////////////////////////////////////

    public void gotDateTime(long time) {
        _timeReceived = time;
    }

    public void gotOptions(byte[] options, boolean isHandshake) {
        if (_log.shouldDebug())
            _log.debug("Got OPTIONS block");
    }

    /**
     *   For most errors here we throw a RIException with a reason code,
     *   which is caught in processPayload() to create a PeerStateDestroyed
     *   and send a termination with that reason.
     *
     *   Plain DataFormatExceptions indicate you may not respond in-session.
     */
    public void gotRI(RouterInfo ri, boolean isHandshake, boolean flood) throws DataFormatException {
        //if (_log.shouldDebug())
        //    _log.debug("Got RI block: " + ri);
        if (isHandshake)
            throw new DataFormatException("RI in Sess Req");
        if (_receivedUnconfirmedIdentity != null)
            throw new DataFormatException("DUP RI in Sess Conf");
        _receivedUnconfirmedIdentity = ri.getIdentity();

        // try to find the right address, because we need the MTU
        boolean isIPv6 = _aliceIP.length == 16;
        List<RouterAddress> addrs = _transport.getTargetAddresses(ri);
        RouterAddress ra = null;
        String mismatchMessage = null;
        for (RouterAddress addr : addrs) {
            // skip SSU 1 address w/o "s"
            if (addrs.size() > 1 && addr.getTransportStyle().equals("SSU") && addr.getOption("s") == null)
                continue;
            String host = addr.getHost();
            if (host == null)
                host = "";
            String caps = addr.getOption(UDPAddress.PROP_CAPACITY);
            if (caps == null)
                caps = "";
            if (isIPv6) {
                if (!host.contains(":") && !caps.contains(TransportImpl.CAP_IPV6))
                    continue;
            } else {
                if (!host.contains(".") && !caps.contains(TransportImpl.CAP_IPV4))
                    continue;
            }
            ra = addr;
            byte[] infoIP = ra.getIP();
            if (infoIP != null && infoIP.length == _aliceIP.length) {
                if (isIPv6) {
                    if ((((int) infoIP[0]) & 0xfe) == 0x02)
                        continue; // ygg
                    if (DataHelper.eq(_aliceIP, 0, infoIP, 0, 8))
                        continue;
                } else {
                    if (DataHelper.eq(_aliceIP, infoIP))
                        continue;
                }
                // We will ban and throw below after checking signature
                mismatchMessage = "IP mismatch actual IP " + Addresses.toString(_aliceIP) + " in RI: ";
            }
            break;
        }

        if (ra == null)
            throw new DataFormatException("no SSU2 addr, ipv6? " + isIPv6 + ": " + ri);
        String siv = ra.getOption("i");
        if (siv == null)
            throw new DataFormatException("no SSU2 IKey");
        byte[] ik = Base64.decode(siv);
        if (ik == null)
            throw new DataFormatException("bad SSU2 IKey");
        if (ik.length != 32)
            throw new DataFormatException("bad SSU2 IKey len");
        String ss = ra.getOption("s");
        if (ss == null)
            throw new DataFormatException("no SSU2 S");
        byte[] s = Base64.decode(ss);
        if (s == null)
            throw new DataFormatException("bad SSU2 S");
        if (s.length != 32)
            throw new DataFormatException("bad SSU2 S len");
        byte[] nb = new byte[32];
        // compare to the _handshakeState
        _handshakeState.getRemotePublicKey().getPublicKey(nb, 0);
        if (!DataHelper.eqCT(s, 0, nb, 0, KEY_LEN))
            throw new DataFormatException("s mismatch in RI: " + ri);

        _sendHeaderEncryptKey1 = ik;

        // only after here can we throw RIExceptions and send a response in-session
        // because we have his ikey and we verified he's the owner of the RI

        Hash h = _receivedUnconfirmedIdentity.calculateHash();
        boolean isBanned = _context.banlist().isBanlistedForever(h);
        if (isBanned) {
            // validate sig to prevent spoofing
            if (ri.verifySignature())
               _context.blocklist().add(_aliceIP);
            throw new RIException("Router is banned: " + h.toBase64(), REASON_BANNED);
        }
        if (ri.getNetworkId() != _context.router().getNetworkID()) {
            if (ri.verifySignature())
               _context.blocklist().add(_aliceIP);
            throw new RIException("SSU2 network ID mismatch", REASON_NETID);
        }

        if (mismatchMessage != null) {
            _context.banlist().banlistRouter(h, "IP mismatch", null,
                                             //_context.banlist().BANLIST_CODE_FOREVER,
                                             null, _context.clock().now() + 2*60*60*1000);
            if (ri.verifySignature())
                _context.blocklist().add(_aliceIP);
            throw new RIException(mismatchMessage + ri, REASON_BANNED);
        }

        if (!"2".equals(ra.getOption("v")))
            throw new RIException("bad SSU2 v", REASON_VERSION);

        if (ri.getCapabilities().equals("LU") && ri.getVersion().equals("0.9.56")) {
            _context.banlist().banlistRouter(h, "Slow", null,
                                             null, _context.clock().now() + 2*60*60*1000);
            if (ri.verifySignature())
                _context.blocklist().add(_aliceIP);
            throw new RIException("Old and slow: " + h, REASON_BANNED);
        }

        String smtu = ra.getOption(UDPAddress.PROP_MTU);
        int mtu = 0;
        try {
            mtu = Integer.parseInt(smtu);
        } catch (NumberFormatException nfe) {}
        if (mtu == 0) {
            if (ra.getTransportStyle().equals(UDPTransport.STYLE2)) {
                mtu = PeerState2.DEFAULT_MTU;
            } else {
                if (isIPv6)
                    mtu = PeerState2.DEFAULT_SSU_IPV6_MTU;
                else
                    mtu = PeerState2.DEFAULT_SSU_IPV4_MTU;
            }
        } else if (mtu == 1276 && ra.getTransportStyle().equals("SSU")) {
            // workaround for bug in 1.9.0
            mtu = PeerState2.MIN_MTU;
        } else {
            // if too small, give up now
            if (mtu < PeerState2.MIN_MTU)
                throw new RIException("MTU too small " + mtu, REASON_OPTIONS);
            if (ra.getTransportStyle().equals(UDPTransport.STYLE2)) {
                mtu = Math.min(Math.max(mtu, PeerState2.MIN_MTU), PeerState2.MAX_MTU);
            } else {
                if (isIPv6)
                    mtu = Math.min(Math.max(mtu, PeerState2.MIN_SSU_IPV6_MTU), PeerState2.MAX_SSU_IPV6_MTU);
                else
                    mtu = Math.min(Math.max(mtu, PeerState2.MIN_SSU_IPV4_MTU), PeerState2.MAX_SSU_IPV4_MTU);
            }
        }
        _mtu = mtu;

        try {
            RouterInfo old = _context.netDb().store(h, ri);
            if (flood && !ri.equals(old)) {
                FloodfillNetworkDatabaseFacade fndf = (FloodfillNetworkDatabaseFacade) _context.netDb();
                if (fndf.floodConditional(ri)) {
                    if (_log.shouldDebug())
                        _log.debug("Flooded the RI: " + h);
                } else {
                    if (_log.shouldInfo())
                        _log.info("Flood request but we didn't: " + h);
                }
            }
        } catch (IllegalArgumentException iae) {
            // generally expired/future RI
            long now = _context.clock().now();
            long published = ri.getPublished();
            int reason;
            if (published > now + 2*60*1000 || published < now - 60*60*1000)
                reason = REASON_SKEW;
            else
                reason = REASON_MSG3;
            throw new RIException("RI store fail: " + ri, reason, iae);
        }

        _receivedConfirmedIdentity = _receivedUnconfirmedIdentity;
        // deferred relay tag request handling, now that we have the RI
        // formerly in EstablishmentManager.receiveSessionOrTokenReques()
        if (_introductionRequested) {
            if (getSentPort() < 1024 ||
                !_transport.canIntroduce(isIPv6)) {
                _introductionRequested = false;
            } else if (VersionComparator.comp(ri.getVersion(), MIN_RELAY_VERSION) < 0) {
                _introductionRequested = false;
                String caps = ri.getCapabilities();
                if (_log.shouldWarn())
                    _log.warn("Not offering to relay to router version " + ri.getVersion() + " caps " + caps + ": " + this);
            } else {
                String caps = ri.getCapabilities();
                // may be requesting relay for ipv4/6 if reachable on the other
                // or may be starting up and not know if reachable or not
                if (caps.indexOf(Router.CAPABILITY_REACHABLE) < 0 ||
                    _context.random().nextInt(4) == 0) {
                    // leave it set to true; createPeerState() will copy to PS2,
                    // who will send the relay tag with ACK 0
                } else {
                    _introductionRequested = false;
                    if (_log.shouldWarn())
                        _log.warn("Not offering to relay to router version " + ri.getVersion() + " caps " + caps + ": " + this);
                }
            }
        }
        createPeerState();
        //_sendHeaderEncryptKey2 calculated below
    }

    public void gotRIFragment(byte[] data, boolean isHandshake, boolean flood, boolean isGzipped, int frag, int totalFrags) {
        if (_log.shouldDebug())
            _log.debug("Got RI fragment " + frag + " of " + totalFrags);
        // not supported, we fragment the whole message now
        throw new IllegalStateException("fragmented RI");
    }

    public void gotAddress(byte[] ip, int port) {
        if (_log.shouldDebug())
            _log.debug("Got Address: " + Addresses.toString(ip, port));
        _bobIP = ip;
        // final, see super
        //_bobPort = port;
    }

    public void gotRelayTagRequest() {
        if (_log.shouldDebug())
            _log.debug("Got relay tag request on " + this);
        _introductionRequested = true;
    }

    public void gotRelayTag(long tag) {
        // shouldn't happen for inbound
    }

    public void gotRelayRequest(byte[] data) {
        if (_receivedConfirmedIdentity == null)
            throw new IllegalStateException("RI must be first");
    }

    public void gotRelayResponse(int status, byte[] data) {
        if (_receivedConfirmedIdentity == null)
            throw new IllegalStateException("RI must be first");
    }

    public void gotRelayIntro(Hash aliceHash, byte[] data) {
        if (_receivedConfirmedIdentity == null)
            throw new IllegalStateException("RI must be first");
    }

    public void gotPeerTest(int msg, int status, Hash h, byte[] data) {
        if (_receivedConfirmedIdentity == null)
            throw new IllegalStateException("RI must be first");
        _transport.getPeerTestManager().receiveTest(_remoteHostId, _pstate, msg, status, h, data);
    }

    public void gotToken(long token, long expires) {
        if (_log.shouldDebug())
            _log.debug("Got token: " + token + " expires " + DataHelper.formatTime(expires) + " on " + this);
        if (_receivedConfirmedIdentity == null)
            throw new IllegalStateException("RI must be first");
        _transport.getEstablisher().addOutboundToken(_remoteHostId, token, expires);
    }

    public void gotI2NP(I2NPMessage msg) {
        if (_log.shouldDebug())
            _log.debug("Got I2NP block: " + msg);
        if (getState() != InboundState.IB_STATE_CREATED_SENT)
            throw new IllegalStateException("I2NP in Sess Req");
        if (_receivedConfirmedIdentity == null)
            throw new IllegalStateException("RI must be first");
        // pass to PeerState2
        _pstate.gotI2NP(msg);
    }

    public void gotFragment(byte[] data, int off, int len, long messageID, int frag, boolean isLast) throws DataFormatException {
        if (_log.shouldDebug())
            _log.debug("Got FRAGMENT block: " + messageID);
        if (getState() != InboundState.IB_STATE_CREATED_SENT)
            throw new IllegalStateException("I2NP in Sess Req");
        if (_receivedConfirmedIdentity == null)
            throw new IllegalStateException("RI must be first");
        // pass to PeerState2
        _pstate.gotFragment(data, off, len, messageID, frag, isLast);
    }

    public void gotACK(long ackThru, int acks, byte[] ranges) {
        throw new IllegalStateException("ACK in Handshake");
    }

    public void gotTermination(int reason, long count) {
        if (_log.shouldWarn())
            _log.warn("Got TERMINATION block, reason: " + reason + " count: " + count + " on " + this);
        // this sets the state to FAILED
        fail();
        _transport.getEstablisher().receiveSessionDestroy(_remoteHostId);
    }

    public void gotPathChallenge(RemoteHostId from, byte[] data) {
        throw new IllegalStateException("Bad block in handshake");
    }

    public void gotPathResponse(RemoteHostId from, byte[] data) {
        throw new IllegalStateException("Bad block in handshake");
    }

    /////////////////////////////////////////////////////////
    // end payload callbacks
    /////////////////////////////////////////////////////////

    // SSU 1 overrides

    /**
     *  Overridden to destroy the handshake state
     *  @since 0.9.56
     */
    @Override
    public synchronized void fail() {
        _handshakeState.destroy();
        super.fail();
    }

    // SSU 2 things

    public long getSendConnID() { return _sendConnID; }
    public long getRcvConnID() { return _rcvConnID; }
    public long getToken() { return _token; }
    /**
     *  @return may be null
     */
    public EstablishmentManager.Token getNextToken() {
        if (_aliceIP.length == 4 && _transport.isSymNatted())
            return null;
        return _transport.getEstablisher().getInboundToken(_remoteHostId);
    }
    public HandshakeState getHandshakeState() { return _handshakeState; }
    public byte[] getSendHeaderEncryptKey1() { return _sendHeaderEncryptKey1; }
    public byte[] getRcvHeaderEncryptKey1() { return _transport.getSSU2StaticIntroKey(); }
    public byte[] getSendHeaderEncryptKey2() { return _sendHeaderEncryptKey2; }
    public synchronized byte[] getRcvHeaderEncryptKey2() { return _rcvHeaderEncryptKey2; }
    public InetSocketAddress getSentAddress() { return _aliceSocketAddress; }

    @Override
    public synchronized void createdPacketSent() {
        /// todo state check
        if (_rcvHeaderEncryptKey2 == null)
            _rcvHeaderEncryptKey2 = SSU2Util.hkdf(_context, _handshakeState.getChainingKey(), "SessionConfirmed");
        _lastSend = _context.clock().now();
        long delay;
        if (_createdSentCount == 0) {
            delay = RETRANSMIT_DELAY;
        } else {
            delay = Math.min(RETRANSMIT_DELAY << _createdSentCount, MAX_DELAY);
        }
        _createdSentCount++;
        _nextSend = _lastSend + delay;
        _currentState = InboundState.IB_STATE_CREATED_SENT;
    }

    
    /** note that we just sent a Retry packet */
    public synchronized void retryPacketSent() {
        // retry after clock skew
        if (_currentState == InboundState.IB_STATE_FAILED)
            return;
        if (_currentState != InboundState.IB_STATE_RETRY_SENT &&
            _currentState != InboundState.IB_STATE_REQUEST_BAD_TOKEN_RECEIVED &&
            _currentState != InboundState.IB_STATE_TOKEN_REQUEST_RECEIVED)
            throw new IllegalStateException("Bad state for Retry Sent: " + _currentState);
        _lastSend = _context.clock().now();
        if (_currentState == InboundState.IB_STATE_RETRY_SENT) {
            // We received a retransmtted token request and resent the retry.
            // Won't really be retransmitted, they have 5 sec to respond
            // ensure we expire before retransmitting
            _nextSend = _establishBegin + (5 * RETRANSMIT_DELAY);
            if (_log.shouldWarn())
                _log.warn("Retransmit retry on " + this);
        } else {
            _currentState = InboundState.IB_STATE_RETRY_SENT;
            // Won't really be retransmitted, they have 5 sec to respond or
            // EstablishmentManager.handleInbound() will fail the connection
            // Alice will retransmit at 1 and 3 seconds, so wait 5
            // We're not going to wait for the 3rd retx at 7 seconds.
            _nextSend = _lastSend + (5 * RETRANSMIT_DELAY);
        }
    }

    /**
     *  All exceptions thrown from here will be fatal. fail() will be called before throwing.
     */
    public synchronized void receiveSessionOrTokenRequestAfterRetry(UDPPacket packet) throws GeneralSecurityException {
        try {
            locked_receiveSessionOrTokenRequestAfterRetry(packet);
        } catch (GeneralSecurityException gse) {
            if (_log.shouldDebug())
                _log.debug("Session/Token request error after retry", gse);
            // fail inside synch rather than have Est. Mgr. do it to prevent races
            fail();
            throw gse;
        }
    }

    /**
     * @since 0.9.56
     */
    private void locked_receiveSessionOrTokenRequestAfterRetry(UDPPacket packet) throws GeneralSecurityException {
        DatagramPacket pkt = packet.getPacket();
        SocketAddress from = pkt.getSocketAddress();
        if (!from.equals(_aliceSocketAddress))
            throw new GeneralSecurityException("Address mismatch: req: " + _aliceSocketAddress + " conf: " + from);
        int off = pkt.getOffset();
        int len = pkt.getLength();
        byte data[] = pkt.getData();
        long rid = DataHelper.fromLong8(data, off);
        if (rid != _rcvConnID)
            throw new GeneralSecurityException("Conn ID mismatch: 1: " + _rcvConnID + " 2: " + rid);
        long sid = DataHelper.fromLong8(data, off + 16);
        if (sid != _sendConnID)
            throw new GeneralSecurityException("Conn ID mismatch: 1: " + _sendConnID + " 2: " + sid);

        int type = data[off + TYPE_OFFSET] & 0xff;
        if (_currentState != InboundState.IB_STATE_RETRY_SENT) {
            // not fatal
            if (_log.shouldWarn())
                _log.warn("Got out-of-order or retx msg " + type + " on: " + this);
            return;
        }
        if (type == TOKEN_REQUEST_FLAG_BYTE) {
            // retransmitted token request
            if (_log.shouldWarn())
                _log.warn("Got retx token request on: " + this);
            // Est. mgr will resend retry and call retryPacketSent()
            // Note that Java I2P < 0.9.57 doesn't handle retransmitted retries correctly,
            // so this won't work for them
            long now = _context.clock().now();
            // rate limit
            _nextSend = Math.max(now, _lastSend + 750);
            return;
        }
        if (_log.shouldDebug())
            _log.debug("Got session request after retry on: " + this);
        long token = DataHelper.fromLong8(data, off + 24);
        if (token != _token) {
            // most likely a retransmitted session request with the old invalid token
            // TODO should we retransmit retry in this case?
            throw new GeneralSecurityException("Token mismatch: expected: " + _token + " got: " + token);
        }
        _handshakeState.start();
        _handshakeState.mixHash(data, off, 32);
        //if (_log.shouldDebug())
        //    _log.debug("State after mixHash 1: " + _handshakeState);

        // decrypt in-place
        try {
            _handshakeState.readMessage(data, off + LONG_HEADER_SIZE, len - LONG_HEADER_SIZE, data, off + LONG_HEADER_SIZE);
        } catch (GeneralSecurityException gse) {
            if (_log.shouldDebug())
                _log.debug("Session Request error, State at failure: " + _handshakeState + '\n' + net.i2p.util.HexDump.dump(data, off, len), gse);
            throw gse;
        }
        //if (_log.shouldDebug())
        //    _log.debug("State after sess req: " + _handshakeState);
        _timeReceived = 0;
        processPayload(data, off + LONG_HEADER_SIZE, len - (LONG_HEADER_SIZE + KEY_LEN + MAC_LEN), true);
        packetReceived();
        if (_currentState == InboundState.IB_STATE_FAILED) {
            // termination block received
            throw new GeneralSecurityException("Termination block in Session Request");
        }
        if (_timeReceived == 0)
            throw new GeneralSecurityException("No DateTime block in Session Request");
        // _nextSend is now(), from packetReceived()
        _rtt = (int) (_nextSend - _lastSend);
        _skew = (_nextSend - _timeReceived) - (_rtt / 2);
        if (_skew > MAX_SKEW || _skew < 0 - MAX_SKEW) {
            // send another retry with termination
            UDPPacket retry = _transport.getBuilder2().buildRetryPacket(this, SSU2Util.REASON_SKEW);
            _transport.send(retry);
            throw new GeneralSecurityException("Skew exceeded in Session Request: " + _skew);
        }
        _sendHeaderEncryptKey2 = SSU2Util.hkdf(_context, _handshakeState.getChainingKey(), "SessCreateHeader");
        _currentState = InboundState.IB_STATE_REQUEST_RECEIVED;
    }

    /**
     * Receive the last messages in the handshake, and create the PeerState.
     * If the message is fragmented, store the data for reassembly and return,
     * unless this was the last one.
     *
     * Exceptions thrown from here are fatal.
     *
     * @return the new PeerState2 if are done, may also be retrieved from getPeerState(),
     *         or null if more fragments to go
     */
    public synchronized PeerState2 receiveSessionConfirmed(UDPPacket packet) throws GeneralSecurityException {
        try {
            return locked_receiveSessionConfirmed(packet);
        } catch (GeneralSecurityException gse) {
            if (_log.shouldDebug())
                _log.debug("Session confirmed error", gse);
            // fail inside synch rather than have Est. Mgr. do it to prevent races
            fail();
            throw gse;
        }
    }

    /**
     *  @since 0.9.56
     */
    private PeerState2 locked_receiveSessionConfirmed(UDPPacket packet) throws GeneralSecurityException {
        if (_currentState != InboundState.IB_STATE_CREATED_SENT &&
            _currentState != InboundState.IB_STATE_CONFIRMED_PARTIALLY)
            throw new GeneralSecurityException("Bad state for Session Confirmed: " + _currentState);
        DatagramPacket pkt = packet.getPacket();
        SocketAddress from = pkt.getSocketAddress();
        if (!from.equals(_aliceSocketAddress))
            throw new GeneralSecurityException("Address mismatch: req: " + _aliceSocketAddress + " conf: " + from);
        int off = pkt.getOffset();
        int len = pkt.getLength();
        byte data[] = pkt.getData();
        long rid = DataHelper.fromLong8(data, off);
        if (rid != _rcvConnID)
            throw new GeneralSecurityException("Conn ID mismatch: req: " + _rcvConnID + " conf: " + rid);
        byte fragbyte = data[off + SHORT_HEADER_FLAGS_OFFSET];
        int frag = (fragbyte >> 4) & 0x0f;
        // allow both 0/0 (development) and 0/1 to indicate sole fragment
        int totalfrag = fragbyte & 0x0f;
        if (totalfrag > 0 && frag > totalfrag - 1)
            throw new GeneralSecurityException("Bad sess conf fragment " + frag + " of " + totalfrag);
        if (totalfrag > 1) {
            // Fragment processing. Save fragment.
            // If we have all fragments, reassemble and continue,
            // else return to await more.
            if (_sessConfFragments == null) {
                _sessConfFragments = new byte[totalfrag][];
                // change state so we will no longer retransmit session created
                _currentState = InboundState.IB_STATE_CONFIRMED_PARTIALLY;
                _sessCrForReTX = null;
                // force past expiration, we don't have anything to send until we have everything
                _nextSend = _lastSend + 60*1000;
            } else {
                if (_sessConfFragments.length != totalfrag) // total frag changed
                    throw new GeneralSecurityException("Bad sess conf fragment " + frag + " of " + totalfrag);
                if (_sessConfFragments[frag] != null) {
                    if (_log.shouldWarn())
                        _log.warn("Got dup sess conf frag " + frag + " on " + this);
                    // there is no facility to ack individual fragments
                    //packetReceived();
                    return null;
                }
            }
            if (_log.shouldDebug())
                _log.debug("Got sess conf frag " + frag + '/' + totalfrag + " len " + len + " on " + this);
            byte[] fragdata;
            if (frag == 0) {
                // preserve header
                fragdata = new byte[len];
                System.arraycopy(data, off, fragdata, 0, len);
            } else {
                // discard header
                len -= SHORT_HEADER_SIZE;
                fragdata = new byte[len];
                System.arraycopy(data, off + SHORT_HEADER_SIZE, fragdata, 0, len);
            }
            _sessConfFragments[frag] = fragdata;
            int totalsize = 0;
            for (int i = 0; i < totalfrag; i++) {
                if (_sessConfFragments[i] == null) {
                    if (_log.shouldDebug())
                        _log.debug("Still missing at least one sess conf frag on " + this);
                    // there is no facility to ack individual fragments
                    //packetReceived();
                    return null;
                }
                totalsize += _sessConfFragments[i].length;
            }
            // we have all the fragments
            // make a jumbo packet and process it through noise
            len = totalsize;
            off = 0;
            data = new byte[len];
            int joff = 0;
            for (int i = 0; i < totalfrag; i++) {
                byte[] f = _sessConfFragments[i];
                System.arraycopy(f, 0, data, joff, f.length);
                joff += f.length;
            }
            if (_log.shouldDebug())
                _log.debug("Have all " + totalfrag + " sess conf frags, total length " + len + " on " + this);
        }
        _handshakeState.mixHash(data, off, SHORT_HEADER_SIZE);
        //if (_log.shouldDebug())
        //    _log.debug("State after mixHash 3: " + _handshakeState);

        // decrypt in-place
        try {
            _handshakeState.readMessage(data, off + SHORT_HEADER_SIZE, len - SHORT_HEADER_SIZE, data, off + SHORT_HEADER_SIZE);
        } catch (GeneralSecurityException gse) {
            if (_log.shouldDebug())
                _log.debug("Session Confirmed error, State at failure: " + _handshakeState + '\n' + net.i2p.util.HexDump.dump(data, off, len), gse);
            throw gse;
        }
        //if (_log.shouldDebug())
        //    _log.debug("State after sess conf: " + _handshakeState);
        processPayload(data, off + SHORT_HEADER_SIZE, len - (SHORT_HEADER_SIZE + KEY_LEN + MAC_LEN + MAC_LEN), false);
        packetReceived();
        if (_currentState == InboundState.IB_STATE_FAILED) {
            // termination block received
            throw new GeneralSecurityException("Termination block in Session Confirmed");
        }
        _sessCrForReTX = null;

        if (_receivedConfirmedIdentity == null)
            throw new GeneralSecurityException("No RI in Session Confirmed");

        // createPeerState() called from gotRI()

        _currentState = InboundState.IB_STATE_CONFIRMED_COMPLETELY;
        return _pstate;
    }

    /**
     *  Creates the PeerState and stores in _pstate.
     *  Called from gotRI() so that we can pass any I2NP messages
     *  or fragments immediately to the PeerState.
     */
    private void createPeerState() {
        // split()
        // The CipherStates are from d_ab/d_ba,
        // not from k_ab/k_ba, so there's no use for
        // HandshakeState.split()
        byte[] ckd = _handshakeState.getChainingKey();
        byte[] k_ab = new byte[32];
        byte[] k_ba = new byte[32];
        HKDF hkdf = new HKDF(_context);
        hkdf.calculate(ckd, ZEROLEN, k_ab, k_ba, 0);
        // generate keys
        byte[] d_ab = new byte[32];
        byte[] h_ab = new byte[32];
        byte[] d_ba = new byte[32];
        byte[] h_ba = new byte[32];
        hkdf.calculate(k_ab, ZEROLEN, INFO_DATA, d_ab, h_ab, 0);
        hkdf.calculate(k_ba, ZEROLEN, INFO_DATA, d_ba, h_ba, 0);
        ChaChaPolyCipherState sender = new ChaChaPolyCipherState();
        sender.initializeKey(d_ba, 0);
        ChaChaPolyCipherState rcvr = new ChaChaPolyCipherState();
        rcvr.initializeKey(d_ab, 0);
      /****
        if (_log.shouldDebug())
            _log.debug("split()\nGenerated Chain key:              " + Base64.encode(ckd) +
                       "\nGenerated split key for A->B:     " + Base64.encode(k_ab) +
                       "\nGenerated split key for B->A:     " + Base64.encode(k_ba) +
                       "\nGenerated encrypt key for A->B:   " + Base64.encode(d_ab) +
                       "\nGenerated encrypt key for B->A:   " + Base64.encode(d_ba) +
                       "\nIntro key for Alice:              " + Base64.encode(_sendHeaderEncryptKey1) +
                       "\nIntro key for Bob:                " + Base64.encode(_rcvHeaderEncryptKey1) +
                       "\nGenerated header key 2 for A->B:  " + Base64.encode(h_ab) +
                       "\nGenerated header key 2 for B->A:  " + Base64.encode(h_ba));
       ****/
        Arrays.fill(ckd, (byte) 0);
        Arrays.fill(k_ab, (byte) 0);
        Arrays.fill(k_ba, (byte) 0);
        Arrays.fill(d_ab, (byte) 0);
        Arrays.fill(d_ba, (byte) 0);
        _handshakeState.destroy();
        if (_createdSentCount == 1)
            _rtt = (int) ( _context.clock().now() - _lastSend );
        _pstate = new PeerState2(_context, _transport, _aliceSocketAddress,
                                 _receivedConfirmedIdentity.calculateHash(),
                                 true, _rtt, sender, rcvr,
                                 _sendConnID, _rcvConnID,
                                 _sendHeaderEncryptKey1, h_ba, h_ab);
        // PS2.super adds CLOCK_SKEW_FUDGE that doesn't apply here
        _pstate.adjustClockSkew(_skew - (_rtt / 2) - PeerState.CLOCK_SKEW_FUDGE);
        _pstate.setHisMTU(_mtu);
        // set our address. _bobIP and _bobPort in super are not set for SSU2
        boolean isIPv6 = _aliceIP.length == 16;
        RouterAddress ra = _transport.getCurrentExternalAddress(isIPv6);
        if (ra != null)
            _pstate.setOurAddress(ra.getIP(), ra.getPort());
        if (_introductionRequested) {
            long tag = 1 + _context.random().nextLong(EstablishmentManager.MAX_TAG_VALUE);
            setSentRelayTag(tag);
            _pstate.setWeRelayToThemAs(tag);
        }
        _pstate.sendAck0();
    }

    /**
     *  Creates a PeerStateDestroyed after msg 3 failure,
     *  so we can send a termination and deal with subsequent in-session messages.
     *
     *  @since 0.9.57
     */
    private PeerStateDestroyed createPeerStateDestroyed(int reason) {
        byte[] ckd = _handshakeState.getChainingKey();
        byte[] k_ab = new byte[32];
        byte[] k_ba = new byte[32];
        HKDF hkdf = new HKDF(_context);
        hkdf.calculate(ckd, ZEROLEN, k_ab, k_ba, 0);
        byte[] d_ab = new byte[32];
        byte[] h_ab = new byte[32];
        byte[] d_ba = new byte[32];
        byte[] h_ba = new byte[32];
        hkdf.calculate(k_ab, ZEROLEN, INFO_DATA, d_ab, h_ab, 0);
        hkdf.calculate(k_ba, ZEROLEN, INFO_DATA, d_ba, h_ba, 0);
        ChaChaPolyCipherState sender = new ChaChaPolyCipherState();
        sender.initializeKey(d_ba, 0);
        ChaChaPolyCipherState rcvr = new ChaChaPolyCipherState();
        rcvr.initializeKey(d_ab, 0);
        _handshakeState.destroy();
        return new PeerStateDestroyed(_context, _transport, _remoteHostId,
                                      _sendConnID, _rcvConnID, sender, rcvr,
                                      _sendHeaderEncryptKey1, h_ba, h_ab, reason);
    }

    /**
     * note that we just sent the SessionCreated packet
     * and save it for retransmission
     */
    public synchronized void createdPacketSent(DatagramPacket pkt) {
        if (_sessCrForReTX == null) {
            // store pkt for retx
            byte data[] = pkt.getData();
            int off = pkt.getOffset();
            int len = pkt.getLength();
            _sessCrForReTX = new byte[len];
            System.arraycopy(data, off, _sessCrForReTX, 0, len);
        }
        createdPacketSent();
    }

    /**
     * @return null if not sent or already got the session confirmed
     */
    public synchronized UDPPacket getRetransmitSessionCreatedPacket() {
        if (_sessCrForReTX == null)
            return null;
        if (_log.shouldInfo())
            _log.info("ReTX Sess Created on " + this);
        UDPPacket packet = UDPPacket.acquire(_context, false);
        DatagramPacket pkt = packet.getPacket();
        byte data[] = pkt.getData();
        int off = pkt.getOffset();
        System.arraycopy(_sessCrForReTX, 0, data, off, _sessCrForReTX.length);
        pkt.setLength(_sessCrForReTX.length);
        pkt.setSocketAddress(_aliceSocketAddress);
        packet.setMessageType(PacketBuilder2.TYPE_CONF);
        packet.setPriority(PacketBuilder2.PRIORITY_HIGH);
        createdPacketSent();
        return packet;
    }

    /**
     * @return null if we have not received the session confirmed
     */
    public synchronized PeerState2 getPeerState() {
        if (_pstate != null) {
            _currentState = InboundState.IB_STATE_COMPLETE;
            if (_queuedDataPackets != null) {
                for (UDPPacket packet : _queuedDataPackets) {
                    if (_log.shouldInfo())
                        _log.info("Passing possible data " + packet + " to PeerState2: " + this);
                    _pstate.receivePacket(packet);
                    packet.release();
                }
                _queuedDataPackets.clear();
            }
        }
        return _pstate;
    }

    /**
     * @param packet with header still encrypted
     */
    public synchronized void queuePossibleDataPacket(UDPPacket packet) {
        if (_currentState == InboundState.IB_STATE_FAILED)
            return;
        if (_pstate == null) {
            // case 1, race or out-of-order, queue until we have the peerstate
            if (_queuedDataPackets == null) {
                _queuedDataPackets = new ArrayList<UDPPacket>(4);
            } else if (_queuedDataPackets.size() >= 10) {
                if (_log.shouldWarn())
                    _log.warn("Not queueing possible data " + packet + ", too many queued on " + this);
                return;
            }
            if (_log.shouldInfo())
                _log.info("Queueing possible data " + packet + " on " + this);
            // have to copy it because PacketHandler will release
            DatagramPacket pkt = packet.getPacket();
            UDPPacket packet2 = UDPPacket.acquire(_context, true);
            DatagramPacket pkt2 = packet2.getPacket();
            System.arraycopy(pkt.getData(), pkt.getOffset(), pkt2.getData(), pkt2.getOffset(), pkt.getLength());
            pkt2.setLength(pkt.getLength());
            pkt2.setSocketAddress(pkt.getSocketAddress());
            _queuedDataPackets.add(packet2);
        } else {
            // case 2, race, decrypt header and pass over
            if (_log.shouldInfo())
                _log.info("Passing possible data " + packet + " to PeerState2: " + this);
            _pstate.receivePacket(packet);
        }
    }
    
    @Override
    public String toString() {            
        StringBuilder buf = new StringBuilder(128);
        buf.append("IES2 ");
        buf.append(Addresses.toString(_aliceIP, _alicePort));
        buf.append(" lifetime: ").append(DataHelper.formatDuration(getLifetime()));
        buf.append(" Rcv ID: ").append(_rcvConnID);
        buf.append(" Send ID: ").append(_sendConnID);
        buf.append(" Token: ").append(_token);
        if (_sentRelayTag > 0)
            buf.append(" RelayTag: ").append(_sentRelayTag);
        buf.append(' ').append(_currentState);
        return buf.toString();
    }

    /**
     *  For throwing out of gotRI()
     *  @since 0.9.57
     */
    private static class RIException extends DataFormatException {
        private final int rsn;
        public RIException(String msg, int reason) {
            super(msg);
            rsn = reason;
        }
        public RIException(String msg, int reason, Throwable t) {
            super(msg, t);
            rsn = reason;
        }
        public int getReason() { return rsn; }
        @Override
        public String getMessage() { return "Code " + rsn + ": " + super.getMessage(); }
    }
}
