TCP_NSC.cc

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//
// Copyright (C) 2006 Sam Jansen, Andras Varga
//               2009 Zoltan Bojthe
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
//

#ifdef WITH_TCP_NSC

#include "TCP_NSC.h"

#include "headers/defs.h"   // for endian macros

#include "IPControlInfo.h"
#include "IPv6ControlInfo.h"
#include "headers/tcp.h"
#include "TCPCommand_m.h"
#include "TCPIPchecksum.h"
#include "TCP_NSC_Queues.h"
#include "TCPSegment.h"
#include "TCPSerializer.h"

#include <assert.h>
#include <dlfcn.h>
#include <netinet/in.h>


Define_Module(TCP_NSC);


//static member variables:
const IPvXAddress TCP_NSC::localInnerIpS("1.0.0.253");
const IPvXAddress TCP_NSC::localInnerMaskS("255.255.255.0");
const IPvXAddress TCP_NSC::localInnerGwS("1.0.0.254");
const IPvXAddress TCP_NSC::remoteFirstInnerIpS("2.0.0.1");

const char * TCP_NSC::stackNameParamNameS = "stackName";

const char * TCP_NSC::bufferSizeParamNameS = "stackBufferSize";

bool TCP_NSC::testingS;
bool TCP_NSC::logverboseS;

// macro for normal ev<< logging (note: deliberately no parens in macro def)
// FIXME
//#define tcpEV (((ev.disable_tracing) || (TCP_NSC::testingS)) ? ev : std::cout)
#define tcpEV ev
//#define tcpEV std::cout

struct nsc_iphdr
{
#if BYTE_ORDER == LITTLE_ENDIAN
    unsigned int ihl:4;
    unsigned int version:4;
#elif BYTE_ORDER == BIG_ENDIAN
    unsigned int version:4;
    unsigned int ihl:4;
#else
# error "Please check BYTE_ORDER declaration"
#endif
    uint8_t tos;
    uint16_t tot_len;
    uint16_t id;
    uint16_t frag_off;
    uint8_t ttl;
    uint8_t protocol;
    uint16_t check;
    uint32_t saddr;
    uint32_t daddr;
    /*The options start here. */
} __attribute__((packed));

struct nsc_ipv6hdr
{
#if BYTE_ORDER == LITTLE_ENDIAN
    uint32_t flow:20;
    uint32_t ds:8;
    uint32_t version:4;
#elif BYTE_ORDER == BIG_ENDIAN
    uint32_t version:4;
    uint32_t ds:8;
    uint32_t flow:20;
#else
# error "Please check BYTE_ORDER declaration"
#endif
    uint16_t len;
    uint8_t next_header;
    uint8_t hop_limit;
    uint16_t id;
    uint16_t frag_off;
    uint8_t ttl;
    uint8_t protocol;
    uint16_t check;
    uint32_t saddr[4];
    uint32_t daddr[4];
} __attribute__((packed));

static char *flags2str(unsigned char flags)
{
    static char buf[512];
    buf[0]='\0';
    if(flags & TH_FIN) strcat(buf, " FIN");
    if(flags & TH_SYN) strcat(buf, " SYN");
    if(flags & TH_RST) strcat(buf, " RST");
    if(flags & TH_PUSH) strcat(buf, " PUSH");
    if(flags & TH_ACK) strcat(buf, " ACK");
    if(flags & TH_URG) strcat(buf, " URG");
//    if(flags & TH_ECE) strcat(buf, " ECE");
//    if(flags & TH_CWR) strcat(buf, " CWR");

    return buf;
}

static std::ostream& operator<<(std::ostream& osP, const TCP_NSC_Connection& connP)
{
    osP << "Conn={"
        << "connId=" << connP.connIdM
        << " appGateIndex=" << connP.appGateIndexM
        << " nscsocket=" << connP.pNscSocketM
        << " sentEstablishedM=" << connP.sentEstablishedM
        << '}';
    return osP;
}

static std::ostream& operator<<(std::ostream& osP, const TCP_NSC_Connection::SockAddr& sockAddrP)
{
    osP << sockAddrP.ipAddrM << ":" << sockAddrP.portM;
    return osP;
}

static std::ostream& operator<<(std::ostream& osP, const TCP_NSC_Connection::SockPair& sockPairP)
{
    osP << "{loc=" << sockPairP.localM << ", rem=" << sockPairP.remoteM << "}";
    return osP;
}

TCP_NSC::TCP_NSC()
  : pStackM(NULL),
    pNsiTimerM(NULL),
    isAliveM(false),
    curAddrCounterM(0),
    curConnM(NULL),

    // statistics:
    sndWndVector(NULL),
    rcvWndVector(NULL),
    rcvAdvVector(NULL),
    sndNxtVector(NULL),
    sndAckVector(NULL),
    rcvSeqVector(NULL),
    rcvAckVector(NULL),
    unackedVector(NULL),
    dupAcksVector(NULL),
    pipeVector(NULL),
    sndSacksVector(NULL),
    rcvSacksVector(NULL),
    rcvOooSegVector(NULL),
    sackedBytesVector(NULL),
    tcpRcvQueueBytesVector(NULL),
    tcpRcvQueueDropsVector(NULL)
{
    // statistics:
    if (true) // (getTcpMain()->recordStatistics)
    {
        //sndWndVector = new cOutVector("send window");
        //rcvWndVector = new cOutVector("receive window");
        sndNxtVector = new cOutVector("sent seq");
        sndAckVector = new cOutVector("sent ack");
        rcvSeqVector = new cOutVector("rcvd seq");
        rcvAckVector = new cOutVector("rcvd ack");
        //unackedVector = new cOutVector("unacked bytes");
        //dupAcksVector = new cOutVector("rcvd dupAcks");
        //pipeVector = new cOutVector("pipe");
        //sndSacksVector = new cOutVector("sent sacks");
        //rcvSacksVector = new cOutVector("rcvd sacks");
        //rcvOooSegVector = new cOutVector("rcvd oooseg");
        //sackedBytesVector = new cOutVector("rcvd sackedBytes");
        //tcpRcvQueueBytesVector = new cOutVector("tcpRcvQueueBytes");
        //tcpRcvQueueDropsVector = new cOutVector("tcpRcvQueueDrops");
    }
}

// return mapped remote ip in host byte order
// if addrP not exists in map, it's create a new nsc addr
uint32_t TCP_NSC::mapRemote2Nsc(IPvXAddress const& addrP)
{
    Remote2NscMap::iterator i = remote2NscMapM.find(addrP);
    if (i != remote2NscMapM.end())
    {
        return i->second;
    }

    // get first free remote NSC IP
    uint32_t ret = remoteFirstInnerIpS.get4().getInt();
    Nsc2RemoteMap::iterator j;
    for( j = nsc2RemoteMapM.begin(); j != nsc2RemoteMapM.end(); j++)
    {
        if(j->first > ret)
            break;
        ret = j->first + 1;
    }

    // add new pair to maps
    remote2NscMapM[addrP] = ret;
    nsc2RemoteMapM[ret] = addrP;
    ASSERT( remote2NscMapM.find(addrP) != remote2NscMapM.end() );
    ASSERT( nsc2RemoteMapM.find(ret) != nsc2RemoteMapM.end() );
    return ret;
}

// return original remote ip from remote NSC IP
// assert if  IP not exists in map
// nscAddrP in host byte order!
IPvXAddress const & TCP_NSC::mapNsc2Remote(uint32_t nscAddrP)
{
    Nsc2RemoteMap::iterator i = nsc2RemoteMapM.find(nscAddrP);
    if (i != nsc2RemoteMapM.end())
    {
        return i->second;
    }
    ASSERT(0);
    exit(1);
}
// x == mapNsc2Remote(mapRemote2Nsc(x))

void TCP_NSC::decode_tcp(const void *packet_data, int hdr_len)
{
    struct tcphdr const *tcp = (struct tcphdr const*)packet_data;
    char buf[4096];

    sprintf(buf, "Src port:%hu Dst port:%hu Seq:%u Ack:%u Off:%hhu %s\n",
            ntohs(tcp->th_sport), ntohs(tcp->th_dport), ntohl(tcp->th_seq),
            ntohl(tcp->th_ack), (unsigned char)tcp->th_offs,
            flags2str(tcp->th_flags)
          );
    tcpEV << this << ": " << buf;
    sprintf(buf, "Win:%hu Sum:%hu Urg:%hu\n",
            ntohs(tcp->th_win), ntohs(tcp->th_sum), ntohs(tcp->th_urp));
    tcpEV << this << ": " << buf;

    if(hdr_len > 20)
    {
        unsigned char const *opt = (unsigned char const*)packet_data + sizeof(struct tcphdr);
        unsigned int optlen = tcp->th_offs*4 - 20;
        unsigned int optoffs = 0;

        tcpEV << this << ": " << ("Options: ");
        while(
                (opt[optoffs] != 0) &&
                (optoffs < optlen)
             )
        {
            unsigned char len = opt[optoffs+1];
            if(len == 0 && opt[optoffs] != 1)
            {
                sprintf(buf, "0-length option(%u)\n", opt[optoffs]);
                tcpEV << this << ": " << buf;
                break;
            }

            len -= 2;

            switch(opt[optoffs])
            {
                case 1: tcpEV << ("No-Op "); optoffs++; break;
                case 2: {       unsigned short mss = 0;
                            //assert(len == 2);
                            if(len == 2) {
                                mss = (opt[optoffs+2] << 8) + (opt[optoffs+3]);
                                sprintf(buf, "MSS(%u) ", mss);
                                tcpEV << buf;
                            } else {
                                sprintf(buf, "MSS:l:%u ", len);
                                tcpEV << buf;
                            }
                            optoffs += opt[optoffs+1];
                            break;
                        }
                case 3: {
                            unsigned char ws = 0;
                            ASSERT(len == 1);
                            ws = opt[optoffs+2];
                            sprintf(buf, "WS(%u) ", ws);
                            tcpEV << buf;
                            optoffs += opt[optoffs+1];
                            break;
                        }
                case 4: {
                            sprintf(buf, "SACK-Permitted ");
                            tcpEV << buf;
                            optoffs += opt[optoffs+1];
                            break;
                        }
                case 5: {
                            tcpEV << ("SACK ");
                            optoffs += opt[optoffs+1];
                            break;
                        }
                case 8: {
                            int i;
                            tcpEV << ("Timestamp(");
                            for(i = 0; i < len; i++) {
                                sprintf(buf, "%02x", opt[optoffs+2+i]);
                                tcpEV << buf;
                            }
                            tcpEV << (") ");
                            optoffs += opt[optoffs+1];
                            break;
                        }
                default:{
                            sprintf(buf, "%u:%u ", opt[0], opt[1]);
                            tcpEV << buf;
                            optoffs += opt[optoffs+1];
                            break;
                        }
            };

        }
        tcpEV << ("\n");
    }
}

void TCP_NSC::initialize()
{
    tcpEV << this << ": initialize\n";
    WATCH_MAP(tcpAppConnMapM);

    cModule *netw = simulation.getSystemModule();
    testingS = netw->hasPar("testing") && netw->par("testing").boolValue();
    logverboseS = !testingS && netw->hasPar("logverbose") && netw->par("logverbose").boolValue();

    const char* stackName = this->par(stackNameParamNameS).stringValue();

    int bufferSize = (int)(this->par(bufferSizeParamNameS).longValue());

    loadStack(stackName, bufferSize);
    pStackM->if_attach(localInnerIpS.str().c_str(), localInnerMaskS.str().c_str(), 1500);
    pStackM->add_default_gateway(localInnerGwS.str().c_str());

    isAliveM = true;
}

TCP_NSC::~TCP_NSC()
{
    tcpEV << this << ": destructor\n";
    isAliveM = false;
    while (!tcpAppConnMapM.empty())
    {
        TcpAppConnMap::iterator i = tcpAppConnMapM.begin();
        delete (*i).second.pNscSocketM;
        tcpAppConnMapM.erase(i);
    }

    // statistics
    delete sndWndVector;
    delete rcvWndVector;
    delete rcvAdvVector;
    delete sndNxtVector;
    delete sndAckVector;
    delete rcvSeqVector;
    delete rcvAckVector;
    delete unackedVector;
    delete dupAcksVector;
    delete sndSacksVector;
    delete rcvSacksVector;
    delete rcvOooSegVector;
    delete tcpRcvQueueBytesVector;
    delete tcpRcvQueueDropsVector;
    delete pipeVector;
    delete sackedBytesVector;
}

// send a TCP_I_ESTABLISHED msg to Application Layer
void TCP_NSC::sendEstablishedMsg(TCP_NSC_Connection &connP)
{

    cMessage *msg = connP.createEstablishedMsg();
    if(msg)
    {
        send(msg, "appOut", connP.appGateIndexM);
        connP.sentEstablishedM = true;
    }
}

void TCP_NSC::changeAddresses(TCP_NSC_Connection &connP,
        const TCP_NSC_Connection::SockPair &inetSockPairP,
        const TCP_NSC_Connection::SockPair &nscSockPairP)
{
    if (!(connP.inetSockPairM == inetSockPairP))
    {
        tcpEV << "conn:" << connP << " change inetMap from " << connP.inetSockPairM << " to " << inetSockPairP << "\n";
        inetSockPair2ConnIdMapM.erase(connP.inetSockPairM);
        connP.inetSockPairM = inetSockPairP;
        inetSockPair2ConnIdMapM[connP.inetSockPairM] = connP.connIdM;
    }
    if (!(connP.nscSockPairM == nscSockPairP))
    {
        tcpEV << "conn:" << connP << " change nscMap from " << connP.nscSockPairM << " to " << nscSockPairP << "\n";
        // remove old from map:
        nscSockPair2ConnIdMapM.erase(connP.nscSockPairM);
        // change addresses:
        connP.nscSockPairM = nscSockPairP;
        // and add to map:
        nscSockPair2ConnIdMapM[connP.nscSockPairM] = connP.connIdM;
    }
}

void TCP_NSC::handleIpInputMessage(TCPSegment* tcpsegP)
{
    // get src/dest addresses
    TCP_NSC_Connection::SockPair nscSockPair, inetSockPair, inetSockPairAny;

    if (dynamic_cast<IPControlInfo *>(tcpsegP->getControlInfo())!=NULL)
    {
        IPControlInfo *controlInfo = (IPControlInfo *)tcpsegP->removeControlInfo();
        inetSockPair.remoteM.ipAddrM = controlInfo->getSrcAddr();
        inetSockPair.localM.ipAddrM = controlInfo->getDestAddr();
        delete controlInfo;
    }
    else if (dynamic_cast<IPv6ControlInfo *>(tcpsegP->getControlInfo())!=NULL)
    {
        IPv6ControlInfo *controlInfo = (IPv6ControlInfo *)tcpsegP->removeControlInfo();
        inetSockPair.remoteM.ipAddrM = controlInfo->getSrcAddr();
        inetSockPair.localM.ipAddrM = controlInfo->getDestAddr();
        delete controlInfo;
        {
            // HACK: when IPv6, then correcting the TCPOPTION_MAXIMUM_SEGMENT_SIZE option
            //       with IP header size difference
            unsigned short numOptions = tcpsegP->getOptionsArraySize();
            for (unsigned short i=0; i < numOptions; i++)
            {
                TCPOption& option = tcpsegP->getOptions(i);
                if(option.getKind() == TCPOPTION_MAXIMUM_SEGMENT_SIZE)
                {
                    unsigned int value = option.getValues(0);
                    value -= sizeof(struct nsc_ipv6hdr) - sizeof(struct nsc_iphdr);
                    option.setValues(0, value);
                    //tcpsegP->setOptions(i, option);
                }
            }
        }
    }
    else
    {
        error("(%s)%s arrived without control info", tcpsegP->getClassName(), tcpsegP->getName());
    }

    // statistics:
    if (rcvSeqVector)
        rcvSeqVector->record(tcpsegP->getSequenceNo());
    if (rcvAckVector)
        rcvAckVector->record(tcpsegP->getAckNo());

    inetSockPair.remoteM.portM = tcpsegP->getSrcPort();
    inetSockPair.localM.portM = tcpsegP->getDestPort();
    nscSockPair.remoteM.portM = tcpsegP->getSrcPort();
    nscSockPair.localM.portM = tcpsegP->getDestPort();
    inetSockPairAny.localM = inetSockPair.localM;

    // process segment
    size_t ipHdrLen = sizeof(nsc_iphdr);
    size_t const maxBufferSize = 4096;
    char *data = new char[maxBufferSize];
    memset(data, 0, maxBufferSize);
    uint32_t nscSrcAddr = mapRemote2Nsc(inetSockPair.remoteM.ipAddrM);
    nscSockPair.localM.ipAddrM = localInnerIpS;
    nscSockPair.remoteM.ipAddrM.set(nscSrcAddr);

    tcpEV << this << ": data arrived for interface of stack "
        << pStackM << "\n" << "src:"<< inetSockPair.remoteM.ipAddrM <<",dest:"<< inetSockPair.localM.ipAddrM <<"\n";

    nsc_iphdr *ih = (nsc_iphdr *)data;
    tcphdr *tcph = (tcphdr *)(data + ipHdrLen);
    // set IP header:
    ih->version = 4;
    ih->ihl = ipHdrLen/4;
    ih->tos = 0;
    ih->id = htons(tcpsegP->getSequenceNo());
    ih->frag_off = htons(0x4000);   // don't fragment, offset = 0;
    ih->ttl = 64;
    ih->protocol = 6;       // TCP
    ih->check = 0;
    ih->saddr = htonl(nscSrcAddr);
    ih->daddr = htonl(localInnerIpS.get4().getInt());

    tcpEV << this << ": modified to: IP " << ih->version << " len " << ih->ihl
          << " protocol " << (unsigned int)(ih->protocol)
          << " saddr " << (ih->saddr)
          << " daddr " << (ih->daddr)
          << "\n";

    size_t totalTcpLen = maxBufferSize - ipHdrLen;
    TCP_NSC_Connection *conn;
    conn = findConnByInetSockPair(inetSockPair);
    if (!conn)
        conn = findConnByInetSockPair(inetSockPairAny);
    if(conn)
    {
        totalTcpLen = conn->receiveQueueM->insertBytesFromSegment(tcpsegP, (void *)tcph, totalTcpLen);
    }
    else
    {
        totalTcpLen = TCPSerializer().serialize(tcpsegP, (unsigned char *)tcph, totalTcpLen);
        //TODO the PayLoad data are destroyed...
    }

    // calculate TCP checksum
    tcph->th_sum = 0;
    tcph->th_sum = TCPSerializer().checksum(tcph, totalTcpLen, nscSockPair.remoteM.ipAddrM, nscSockPair.localM.ipAddrM);

    size_t totalIpLen = ipHdrLen + totalTcpLen;
    ih->tot_len = htons(totalIpLen);
    ih->check = 0;
    ih->check = TCPIPchecksum::checksum(ih, ipHdrLen);

    decode_tcp( (void *)tcph, totalTcpLen);

    // receive msg from network

    pStackM->if_receive_packet(0, data, totalIpLen);

    // Attempt to read from sockets
    TcpAppConnMap::iterator j;
    int changes = 0;
    for(j = tcpAppConnMapM.begin(); j != tcpAppConnMapM.end(); ++j)
    {
        TCP_NSC_Connection &c = j->second;

        if(c.pNscSocketM && c.isListenerM)
        {
            // accepting socket
            tcpEV << this << ": NSC: attempting to accept:\n";

            INetStreamSocket *sock = NULL;
            int err;

            err = c.pNscSocketM->accept( &sock );

            tcpEV << this << ": accept returned " << err << " , sock is " << sock
                << " socket" << c.pNscSocketM << "\n";

            if(sock)
            {
                ASSERT(changes == 0);
                ASSERT(c.inetSockPairM.localM.portM == inetSockPair.localM.portM);
                ++changes;

                TCP_NSC_Connection *conn;
                int newConnId = ev.getUniqueNumber();
                // add into appConnMap
                conn = &tcpAppConnMapM[newConnId];
                conn->connIdM = newConnId;
                conn->appGateIndexM = c.appGateIndexM;
                conn->pNscSocketM = sock;

                // set sockPairs:
                changeAddresses(*conn, inetSockPair, nscSockPair);

                // following code to be kept consistent with initConnection()
                const char *sendQueueClass = c.sendQueueM->getClassName();
                conn->sendQueueM = check_and_cast<TCP_NSC_SendQueue *>(createOne(sendQueueClass));
                conn->sendQueueM->setConnection(conn);

                const char *receiveQueueClass = c.receiveQueueM->getClassName();
                conn->receiveQueueM = check_and_cast<TCP_NSC_ReceiveQueue *>(createOne(receiveQueueClass));
                conn->receiveQueueM->setConnection(conn);
                tcpEV << this << ": NSC: got accept!\n";

                sendEstablishedMsg(*conn);
            }
        }
        else if(c.pNscSocketM && c.pNscSocketM->is_connected() ) // not listener
        {
            bool hasData = false;
            tcpEV << this << ": NSC: attempting to read from socket " << c.pNscSocketM << "\n";

            if ((!c.sentEstablishedM) && c.pNscSocketM->is_connected())
            {
                ASSERT(changes == 0);
                hasData = true;
                changeAddresses(c, inetSockPair, nscSockPair);
                sendEstablishedMsg(c);
            }
            while(true)
            {
                static char buf[4096];

                int buflen = sizeof(buf);

                int err = c.pNscSocketM->read_data(buf, &buflen);

                tcpEV << this << ": NSC: read: err " << err << " , buflen " << buflen << "\n";

                if(err == 0 && buflen > 0)
                {
                    ASSERT(changes == 0);
                    if(!hasData)
                        changeAddresses(c, inetSockPair, nscSockPair);

                    hasData = true;
                    c.receiveQueueM->enqueueNscData(buf, buflen);
/*
                    struct sockaddr_in peerAddr,sockAddr;
                    size_t peerAddrLen=sizeof(peerAddr),sockAddrLen=sizeof(sockAddr);
                    c.pNscSocketM->getpeername((sockaddr*)&peerAddr, &peerAddrLen);
                    c.pNscSocketM->getsockname((sockaddr*)&sockAddr, &sockAddrLen);
*/
                }
                else
                    break;
            }
            if(hasData)
            {
                while(cPacket *dataMsg = c.receiveQueueM->extractBytesUpTo())
                {
                    // send Msg to Application layer:
                    send(dataMsg, "appOut", c.appGateIndexM);
                }
                ++changes;
                changeAddresses(c, inetSockPair, nscSockPair);
            }
        }
    }

    /*
    ...
    NSC: process segment (data,len); should call removeConnection() if socket has
    closed and completely done

    XXX: probably need to poll sockets to see if they are closed.
    ...
    */

    delete [] data;
    delete tcpsegP;
}

void TCP_NSC::handleAppMessage(cMessage *msgP)
{
    TCPCommand *controlInfo = check_and_cast<TCPCommand *>(msgP->getControlInfo());
    int connId = controlInfo->getConnId();

    TCP_NSC_Connection *conn = findAppConn(connId);
    if (!conn)
    {
        TCPOpenCommand *openCmd = check_and_cast<TCPOpenCommand *>(controlInfo);
        // add into appConnMap
        conn = &tcpAppConnMapM[connId];
        conn->connIdM = connId;
        conn->appGateIndexM = msgP->getArrivalGate()->getIndex();
        conn->pNscSocketM = NULL;  // will be filled in within processAppCommand()

        // create send queue
        const char *sendQueueClass = openCmd->getSendQueueClass();
        if (!sendQueueClass || !sendQueueClass[0])
            sendQueueClass = this->par("sendQueueClass");
        conn->sendQueueM = check_and_cast<TCP_NSC_SendQueue *>(createOne(sendQueueClass));
        conn->sendQueueM->setConnection(conn);

        // create receive queue
        const char *receiveQueueClass = openCmd->getReceiveQueueClass();
        if (!receiveQueueClass || !receiveQueueClass[0])
            receiveQueueClass = this->par("receiveQueueClass");
        conn->receiveQueueM = check_and_cast<TCP_NSC_ReceiveQueue *>(createOne(receiveQueueClass));
        conn->receiveQueueM->setConnection(conn);

        tcpEV << this << ": TCP connection created for " << msgP << "\n";
    }
    processAppCommand(*conn, msgP);
}

void TCP_NSC::handleMessage(cMessage *msgP)
{
    if (msgP->isSelfMessage())
    {
        // timer expired
        /*
        ...
        NSC timer processing
        ...
           Timers are ordinary cMessage objects that are started by
           scheduleAt(simTime()+timeout, msg), and can be cancelled
           via cancelEvent(msg); when they expire (fire) they are delivered
           to the module via handleMessage(), i.e. they end up here.
        */
        if(msgP == pNsiTimerM )
        { // nsc_nsi_timer
            do_SEND_all();

            pStackM->increment_ticks();

            pStackM->timer_interrupt();

            scheduleAt(msgP->getArrivalTime() + 1.0 / (double)pStackM->get_hz(), msgP);
        }
    }
    else if (msgP->arrivedOn("ipIn") || msgP->arrivedOn("ipv6In"))
    {
        tcpEV << this << ": handle msg: " << msgP->getName() << "\n";
        // must be a TCPSegment
        TCPSegment *tcpseg = check_and_cast<TCPSegment *>(msgP);
        handleIpInputMessage(tcpseg);

    }
    else // must be from app
    {
        tcpEV << this << ": handle msg: " << msgP->getName() << "\n";
        handleAppMessage(msgP);
    }

    if (ev.isGUI())
        updateDisplayString();
}

void TCP_NSC::updateDisplayString()
{
    //...
}

TCP_NSC_Connection *TCP_NSC::findAppConn(int connIdP)
{
    TcpAppConnMap::iterator i = tcpAppConnMapM.find(connIdP);
    return i==tcpAppConnMapM.end() ? NULL : &(i->second);
}

TCP_NSC_Connection *TCP_NSC::findConnByInetSockPair(TCP_NSC_Connection::SockPair const & sockPairP)
{
    SockPair2ConnIdMap::iterator i = inetSockPair2ConnIdMapM.find(sockPairP);
    return i==inetSockPair2ConnIdMapM.end() ? NULL : findAppConn(i->second);
}

TCP_NSC_Connection *TCP_NSC::findConnByNscSockPair(TCP_NSC_Connection::SockPair const & sockPairP)
{
    SockPair2ConnIdMap::iterator i = nscSockPair2ConnIdMapM.find(sockPairP);
    return i==nscSockPair2ConnIdMapM.end() ? NULL : findAppConn(i->second);
}

void TCP_NSC::finish()
{
    isAliveM = false;
}

void TCP_NSC::removeConnection(int connIdP)
{
    TcpAppConnMap::iterator i = tcpAppConnMapM.find(connIdP);
    if (i != tcpAppConnMapM.end())
        tcpAppConnMapM.erase(i);
}

void TCP_NSC::printConnBrief(TCP_NSC_Connection& connP)
{
    tcpEV << this << ": connId=" << connP.connIdM << " appGateIndex=" << connP.appGateIndexM;
    tcpEV << " nscsocket=" << connP.pNscSocketM << "\n";
}

void TCP_NSC::loadStack(const char* stacknameP, int bufferSizeP)
{
    void *handle = NULL;
    FCreateStack create = NULL;

    tcpEV << this << ": Loading stack " << stacknameP << "\n";

    handle = dlopen(stacknameP, RTLD_NOW);
    if(!handle) {
        fputs("The loading of NSC stack is unsuccessful: ", stderr);
        fputs(dlerror(), stderr);
        fputs("\nCheck the LD_LIBRARY_PATH or stackname!\n", stderr);
        exit(1);
    }

    create = (FCreateStack)dlsym(handle, "nsc_create_stack");
    if(!create) {
        fputs(dlerror(), stderr);
        fputs("\n", stderr);
        exit(1);
    }

    pStackM = create(this, this, NULL);

    tcpEV << "TCP_NSC " << this << " has stack " << pStackM << "\n";

    fprintf(stderr, "Created stack = %p\n", pStackM);

    fprintf(stderr, "Initialising stack, name=%s\n", pStackM->get_name());

    pStackM->init(pStackM->get_hz());

    pStackM->buffer_size(bufferSizeP);

    fprintf(stderr, "done.\n");

    // set timer for 1.0 / pStackM->get_hz()
    pNsiTimerM = new cMessage("nsc_nsi_timer");
    scheduleAt(1.0 / (double)pStackM->get_hz(), pNsiTimerM);
}

void TCP_NSC::send_callback(const void *dataP, int datalenP)
{
    if(!isAliveM)
        return;
    tcpEV << this << ": NSC: send_callback(" << dataP << ", " << datalenP << ") called\n";

    sendToIP(dataP, datalenP);

    // comment from nsc.cc:
    //   New method: if_send_finish. This should be called by the nic
    //   driver code when there is space in it's queue. Unfortunately
    //   we don't know whether that is the case from here, so we just
    //   call it immediately for now. **THIS IS INCORRECT**. It should
    //   only be called when a space becomes free in the nic queue.
    pStackM->if_send_finish(0);    // XXX: hardcoded inerface id
}

/*
void TCP_NSC::interrupt()
{
}
*/

void TCP_NSC::wakeup()
{
    if(!isAliveM)
        return;
    tcpEV << this << ": wakeup() called\n";
}

void TCP_NSC::gettime(unsigned int *secP, unsigned int *usecP)
{
#if OMNETPP_VERSION < 0x0400
    simtime_t t = simTime();
    *sec = (unsigned int)(t);
    *usec = (unsigned int)((t - *sec) * 1000000 + 0.5);
#else
#ifdef USE_DOUBLE_SIMTIME
    double t = simTime().dbl();
    *sec = (unsigned int)(t);
    *usec = (unsigned int)((t - *sec) * 1000000 + 0.5);
#else
    simtime_t t = simTime();
    int64 raw = t.raw();
    int64 scale = t.getScale();
    int64 secs = raw / scale;
    int64 usecs = (raw - (secs * scale));
    //usecs = usecs * 1000000 / scale;
    if(scale>1000000) // scale always 10^n
        usecs /= (scale / 1000000);
    else
        usecs *= (1000000 / scale);
    *secP = secs;
    *usecP = usecs;
#endif
#endif
    tcpEV << this << ": gettime(" << *secP << "," << *usecP << ") called\n";
}

void TCP_NSC::sendToIP(const void *dataP, int lenP)
{
    IPvXAddress src,dest;
    const nsc_iphdr *iph = (const nsc_iphdr *)dataP;

    int ipHdrLen = 4 * iph->ihl;
    ASSERT(ipHdrLen <= lenP);
    int totalLen = ntohs(iph->tot_len);
    ASSERT(totalLen == lenP);
    tcphdr const *tcph = (tcphdr const*)(((const char *)(iph)) + ipHdrLen);

        // XXX add some info (seqNo, len, etc)

    TCP_NSC_Connection::SockPair nscSockPair;

    TCP_NSC_Connection *conn;

    nscSockPair.localM.ipAddrM.set(ntohl(iph->saddr));
    nscSockPair.localM.portM = ntohs(tcph->th_sport);
    nscSockPair.remoteM.ipAddrM.set(ntohl(iph->daddr));
    nscSockPair.remoteM.portM = ntohs(tcph->th_dport);

    if(curConnM)
    {
        changeAddresses(*curConnM, curConnM->inetSockPairM, nscSockPair);
        conn = curConnM;
    }
    else
    {
        conn = findConnByNscSockPair(nscSockPair);
    }

    TCPSegment *tcpseg;
    if(conn)
    {
        tcpseg = conn->sendQueueM->createSegmentWithBytes(tcph, totalLen-ipHdrLen);
        src = conn->inetSockPairM.localM.ipAddrM;
        dest = conn->inetSockPairM.remoteM.ipAddrM;
    }
    else
    {
        tcpseg = new TCPSegment("tcp-segment");

        TCPSerializer().parse((const unsigned char *)tcph, totalLen-ipHdrLen, tcpseg);
        dest = mapNsc2Remote(ntohl(iph->daddr));
    }
    ASSERT(tcpseg);

    tcpEV << this << ": Sending: conn=" << conn << ", data: " << dataP << " of len " << lenP << " from " << src
       << " to " << dest << "\n";

    const char* output;
    if (!dest.isIPv6())
    {
        // send over IPv4
        IPControlInfo *controlInfo = new IPControlInfo();
        controlInfo->setProtocol(IP_PROT_TCP);
        controlInfo->setSrcAddr(src.get4());
        controlInfo->setDestAddr(dest.get4());
        tcpseg->setControlInfo(controlInfo);

        output = "ipOut";
    }
    else
    {
        // send over IPv6
        IPv6ControlInfo *controlInfo = new IPv6ControlInfo();
        controlInfo->setProtocol(IP_PROT_TCP);
        controlInfo->setSrcAddr(src.get6());
        controlInfo->setDestAddr(dest.get6());
        tcpseg->setControlInfo(controlInfo);

        output ="ipv6Out";
    }
    if(conn)
    {
        conn->receiveQueueM->notifyAboutSending(tcpseg);
    }

    // record seq (only if we do send data) and ackno
    if (sndNxtVector && tcpseg->getPayloadLength()!=0)
        sndNxtVector->record(tcpseg->getSequenceNo());
    if (sndAckVector)
        sndAckVector->record(tcpseg->getAckNo());

    send(tcpseg, output);
}

void TCP_NSC::processAppCommand(TCP_NSC_Connection& connP, cMessage *msgP)
{
    printConnBrief(connP);

    // first do actions
    TCPCommand *tcpCommand = (TCPCommand *)(msgP->removeControlInfo());

    switch (msgP->getKind())
    {
        case TCP_C_OPEN_ACTIVE: process_OPEN_ACTIVE(connP, tcpCommand, msgP); break;
        case TCP_C_OPEN_PASSIVE: process_OPEN_PASSIVE(connP, tcpCommand, msgP); break;
        case TCP_C_SEND: process_SEND(connP, tcpCommand, check_and_cast<cPacket*>(msgP)); break;
        case TCP_C_CLOSE: process_CLOSE(connP, tcpCommand, msgP); break;
        case TCP_C_ABORT: process_ABORT(connP, tcpCommand, msgP); break;
        case TCP_C_STATUS: process_STATUS(connP, tcpCommand, msgP); break;
        default: opp_error("wrong command from app: %d", msgP->getKind());
    }

    /*
    ...
    NSC: should call removeConnection(connP.connIdM) if socket has been destroyed
    ...
    */
}

void TCP_NSC::process_OPEN_ACTIVE(TCP_NSC_Connection& connP, TCPCommand *tcpCommandP, cMessage *msgP)
{
    TCPOpenCommand *openCmd = check_and_cast<TCPOpenCommand *>(tcpCommandP);

    TCP_NSC_Connection::SockPair inetSockPair,nscSockPair;
    inetSockPair.localM.ipAddrM = openCmd->getLocalAddr();
    inetSockPair.remoteM.ipAddrM = openCmd->getRemoteAddr();
    inetSockPair.localM.portM = openCmd->getLocalPort();
    inetSockPair.remoteM.portM = openCmd->getRemotePort();

    if (inetSockPair.remoteM.ipAddrM.isUnspecified() || inetSockPair.remoteM.portM == -1)
        opp_error("Error processing command OPEN_ACTIVE: remote address and port must be specified");

    tcpEV << this << ": OPEN: "
        << inetSockPair.localM.ipAddrM << ":" << inetSockPair.localM.portM << " --> "
        << inetSockPair.remoteM.ipAddrM << ":" << inetSockPair.remoteM.portM << "\n";

    // insert to map:
    uint32_t nscRemoteAddr = mapRemote2Nsc(inetSockPair.remoteM.ipAddrM);

    ASSERT(pStackM);

    nscSockPair.localM.portM = inetSockPair.localM.portM;
    if (nscSockPair.localM.portM == -1)
        nscSockPair.localM.portM = 0; // NSC uses 0 to mean "not specified"
    nscSockPair.remoteM.ipAddrM.set(nscRemoteAddr);
    nscSockPair.remoteM.portM = inetSockPair.remoteM.portM;

    changeAddresses(connP, inetSockPair, nscSockPair);

    ASSERT(!curConnM);
    curConnM = &connP;
    connP.connect(*pStackM, inetSockPair, nscSockPair);
    curConnM = NULL;

    // and add to map:
    // TODO sendToIp already set the addresses.
    //changeAddresses(connP, inetSockPair, nscSockPair);

    delete tcpCommandP;
    delete msgP;
}

void TCP_NSC::process_OPEN_PASSIVE(TCP_NSC_Connection& connP, TCPCommand *tcpCommandP, cMessage *msgP)
{
    ASSERT(pStackM);

    TCPOpenCommand *openCmd = check_and_cast<TCPOpenCommand *>(tcpCommandP);

    ASSERT(openCmd->getFork()==true);

    TCP_NSC_Connection::SockPair inetSockPair, nscSockPair;
    inetSockPair.localM.ipAddrM = openCmd->getLocalAddr();
    inetSockPair.remoteM.ipAddrM = openCmd->getRemoteAddr();
    inetSockPair.localM.portM = openCmd->getLocalPort();
    inetSockPair.remoteM.portM = openCmd->getRemotePort();

    uint32_t nscRemoteAddr = inetSockPair.remoteM.ipAddrM.isUnspecified()
        ? ntohl(INADDR_ANY)
        : mapRemote2Nsc(inetSockPair.remoteM.ipAddrM); // Don't remove! It's insert remoteAddr into MAP.
    (void)nscRemoteAddr; // Eliminate "unused variable" warning.

    if (inetSockPair.localM.portM == -1)
        opp_error("Error processing command OPEN_PASSIVE: local port must be specified");

    tcpEV << this << "Starting to listen on: " << inetSockPair.localM.ipAddrM << ":" << inetSockPair.localM.portM << "\n";

    /*
    ...
    NSC: process passive open request
    ...
    */
    nscSockPair.localM.portM = inetSockPair.localM.portM;

    changeAddresses(connP, inetSockPair, nscSockPair);

    ASSERT(!curConnM);
    curConnM = &connP;
    connP.listen(*pStackM, inetSockPair, nscSockPair);
    curConnM = NULL;

    changeAddresses(connP, inetSockPair, nscSockPair);

    delete openCmd;
    delete msgP;
}

void TCP_NSC::process_SEND(TCP_NSC_Connection& connP, TCPCommand *tcpCommandP, cPacket *msgP)
{
    TCPSendCommand *sendCommand = check_and_cast<TCPSendCommand *>(tcpCommandP);
    delete sendCommand;

    connP.send(msgP);

    connP.do_SEND();
}

void TCP_NSC::do_SEND_all()
{
    TcpAppConnMap::iterator j = tcpAppConnMapM.begin();
    for(; j != tcpAppConnMapM.end(); ++j)
    {
        TCP_NSC_Connection& conn = j->second;
        conn.do_SEND();
    }
}

void TCP_NSC::process_CLOSE(TCP_NSC_Connection& connP, TCPCommand *tcpCommandP, cMessage *msgP)
{
    tcpEV << this << ": process_CLOSE()\n";

    delete tcpCommandP;
    delete msgP;

    connP.close();
}

void TCP_NSC::process_ABORT(TCP_NSC_Connection& connP, TCPCommand *tcpCommandP, cMessage *msgP)
{
    tcpEV << this << ": process_ABORT()\n";

    delete tcpCommandP;
    delete msgP;

    connP.abort();
}

void TCP_NSC::process_STATUS(TCP_NSC_Connection& connP, TCPCommand *tcpCommandP, cMessage *msgP)
{
    delete tcpCommandP; // but we'll reuse msg for reply

    TCPStatusInfo *statusInfo = new TCPStatusInfo();

    /*
    ...
    NSC: fill in status if possible

         Still more work to do here. Some of this needs to be implemented on
         the NSC side, which is fairly trivial, just updating the get_var
         function for each stack.
    ...
    */

    char result[512];

    ASSERT(connP.pNscSocketM);

    connP.pNscSocketM->get_var("cwnd_", result, sizeof(result));
    statusInfo->setSnd_wnd(atoi(result));

    //connP.pNscSocketM->get_var("ssthresh_", result, sizeof(result));
    //connP.pNscSocketM->get_var("rxtcur_", result, sizeof(result));


/* other TCP model:
    statusInfo->setState(fsm.getState());
    statusInfo->setStateName(stateName(fsm.getState()));

    statusInfo->setLocalAddr(localAddr);
    statusInfo->setRemoteAddr(remoteAddr);
    statusInfo->setLocalPort(localPort);
    statusInfo->setRemotePort(remotePort);

    statusInfo->setSnd_mss(state->snd_mss);
    statusInfo->setSnd_una(state->snd_una);
    statusInfo->setSnd_nxt(state->snd_nxt);
    statusInfo->setSnd_max(state->snd_max);
    statusInfo->setSnd_wnd(state->snd_wnd);
    statusInfo->setSnd_up(state->snd_up);
    statusInfo->setSnd_wl1(state->snd_wl1);
    statusInfo->setSnd_wl2(state->snd_wl2);
    statusInfo->setIss(state->iss);
    statusInfo->setRcv_nxt(state->rcv_nxt);
    statusInfo->setRcv_wnd(state->rcv_wnd);
    statusInfo->setRcv_up(state->rcv_up);
    statusInfo->setIrs(state->irs);
    statusInfo->setFin_ack_rcvd(state->fin_ack_rcvd);
*/

    msgP->setControlInfo(statusInfo);
    send(msgP, "appOut", connP.appGateIndexM);
}

#endif // WITH_TCP_NSC