inet::tcp::TcpCrcInsertionHook Class Reference

#include <TcpCrcInsertionHook.h>

Inheritance diagram for inet::tcp::TcpCrcInsertionHook:

Public Member Functions
virtual Result	datagramPreRoutingHook (Packet *packet) override
	This is the first hook called by the network protocol before it routes a datagram that was received from the lower layer. More...
virtual Result	datagramForwardHook (Packet *packet) override
	This is the second hook called by the network protocol before it sends a datagram to the lower layer. More...
virtual Result	datagramPostRoutingHook (Packet *packet) override
	This is the last hook called by the network protocol before it sends a datagram to the lower layer. More...
virtual Result	datagramLocalInHook (Packet *packet) override
	This is the last hook called by the network protocol before it sends a datagram to the upper layer. More...
virtual Result	datagramLocalOutHook (Packet *packet) override
	This is the first hook called by the network protocol before it routes a datagram that was received from the upper layer. More...
Public Member Functions inherited from inet::NetfilterBase::HookBase
virtual	~HookBase ()
void	registeredTo (INetfilter *nf)
void	unregisteredFrom (INetfilter *nf)
bool	isRegisteredHook (INetfilter *nf)
Public Member Functions inherited from inet::INetfilter::IHook
virtual	~IHook ()

Static Public Member Functions
static void	insertCrc (const Protocol *networkProtocol, const L3Address &srcAddress, const L3Address &destAddress, const Ptr< TcpHeader > &tcpHeader, Packet *tcpPayload)
static uint16_t	computeCrc (const Protocol *networkProtocol, const L3Address &srcAddress, const L3Address &destAddress, const Ptr< const TcpHeader > &tcpHeader, const Ptr< const Chunk > &tcpData)

Additional Inherited Members
Public Types inherited from inet::INetfilter::IHook
enum	Type {   PREROUTING, LOCALIN, FORWARD, POSTROUTING,   LOCALOUT }
enum	Result { ACCEPT, DROP, QUEUE, STOLEN }
Protected Attributes inherited from inet::NetfilterBase::HookBase
std::vector< INetfilter * >	netfilters

Member Function Documentation

computeCrc()

uint16_t inet::tcp::TcpCrcInsertionHook::computeCrc ( const Protocol *  networkProtocol, const L3Address &  srcAddress, const L3Address &  destAddress, const Ptr< const TcpHeader > &  tcpHeader, const Ptr< const Chunk > &  tcpData  )

static

{
    auto pseudoHeader = makeShared<TransportPseudoHeader>();
    pseudoHeader->setSrcAddress(srcAddress);
    pseudoHeader->setDestAddress(destAddress);
    pseudoHeader->setNetworkProtocolId(networkProtocol->getId());
    pseudoHeader->setProtocolId(IP_PROT_TCP);
    pseudoHeader->setPacketLength(tcpHeader->getChunkLength() + tcpData->getChunkLength());
    // pseudoHeader length: ipv4: 12 bytes, ipv6: 40 bytes, generic: ???
    if (networkProtocol == &Protocol::ipv4)
        pseudoHeader->setChunkLength(B(12));
    else if (networkProtocol == &Protocol::ipv6)
        pseudoHeader->setChunkLength(B(40));
    else
        throw cRuntimeError("Unknown network protocol: %s", networkProtocol->getName());
    MemoryOutputStream stream;
    Chunk::serialize(stream, pseudoHeader);
    Chunk::serialize(stream, tcpHeader);
    Chunk::serialize(stream, tcpData);
    uint16_t crc = TcpIpChecksum::checksum(stream.getData());
    return crc;
}

Referenced by insertCrc().

datagramForwardHook()

virtual Result inet::tcp::TcpCrcInsertionHook::datagramForwardHook ( Packet *  datagram )

inlineoverridevirtual

This is the second hook called by the network protocol before it sends a datagram to the lower layer.

This is done after the datagramPreRoutingHook or the datagramLocalInHook is called and the datagram is routed.

Implements inet::INetfilter::IHook.

{ return ACCEPT; }

datagramLocalInHook()

virtual Result inet::tcp::TcpCrcInsertionHook::datagramLocalInHook ( Packet *  datagram )

inlineoverridevirtual

This is the last hook called by the network protocol before it sends a datagram to the upper layer.

This is done after the datagramPreRoutingHook is called and the datagram is routed.

Implements inet::INetfilter::IHook.

{ return ACCEPT; }

datagramLocalOutHook()

virtual Result inet::tcp::TcpCrcInsertionHook::datagramLocalOutHook ( Packet *  datagram )

inlineoverridevirtual

This is the first hook called by the network protocol before it routes a datagram that was received from the upper layer.

The nextHopAddress is ignored when the outputNetworkInterface is a nullptr. After this is done

Implements inet::INetfilter::IHook.

{ return ACCEPT; }

datagramPostRoutingHook()

INetfilter::IHook::Result inet::tcp::TcpCrcInsertionHook::datagramPostRoutingHook ( Packet *  datagram )

overridevirtual

This is the last hook called by the network protocol before it sends a datagram to the lower layer.

Implements inet::INetfilter::IHook.

{
    Enter_Method("datagramPostRoutingHook");
 
    if (packet->findTag<InterfaceInd>())
        return ACCEPT; // FORWARD
    auto networkProtocol = packet->getTag<PacketProtocolTag>()->getProtocol();
    const auto& networkHeader = getNetworkProtocolHeader(packet);
    if (networkHeader->getProtocol() == &Protocol::tcp) {
        ASSERT(!networkHeader->isFragment());
        packet->eraseAtFront(networkHeader->getChunkLength());
        auto tcpHeader = packet->removeAtFront<TcpHeader>();
        ASSERT(tcpHeader->getCrcMode() == CRC_COMPUTED);
        const L3Address& srcAddress = networkHeader->getSourceAddress();
        const L3Address& destAddress = networkHeader->getDestinationAddress();
        insertCrc(networkProtocol, srcAddress, destAddress, tcpHeader, packet);
        packet->insertAtFront(tcpHeader);
        packet->insertAtFront(networkHeader);
    }
    return ACCEPT;
}

datagramPreRoutingHook()

virtual Result inet::tcp::TcpCrcInsertionHook::datagramPreRoutingHook ( Packet *  datagram )

inlineoverridevirtual

This is the first hook called by the network protocol before it routes a datagram that was received from the lower layer.

The nextHopAddress is ignored when the outputNetworkInterface is nullptr.

Implements inet::INetfilter::IHook.

{ return ACCEPT; }

insertCrc()

void inet::tcp::TcpCrcInsertionHook::insertCrc ( const Protocol *  networkProtocol, const L3Address &  srcAddress, const L3Address &  destAddress, const Ptr< TcpHeader > &  tcpHeader, Packet *  tcpPayload  )

static

{
    auto crcMode = tcpHeader->getCrcMode();
    switch (crcMode) {
        case CRC_DECLARED_CORRECT:
            // if the CRC mode is declared to be correct, then set the CRC to an easily recognizable value
            tcpHeader->setCrc(0xC00D);
            break;
        case CRC_DECLARED_INCORRECT:
            // if the CRC mode is declared to be incorrect, then set the CRC to an easily recognizable value
            tcpHeader->setCrc(0xBAAD);
            break;
        case CRC_COMPUTED: {
            // if the CRC mode is computed, then compute the CRC and set it
            // this computation is delayed after the routing decision, see INetfilter hook
            tcpHeader->setCrc(0x0000); // make sure that the CRC is 0 in the TCP header before computing the CRC
            auto tcpData = packet->peekData(Chunk::PF_ALLOW_EMPTY);
            auto crc = computeCrc(networkProtocol, srcAddress, destAddress, tcpHeader, tcpData);
            tcpHeader->setCrc(crc);
            break;
        }
        default:
            throw cRuntimeError("Unknown CRC mode");
    }
}

Referenced by datagramPostRoutingHook(), and inet::Ipv4NatTable::processPacket().

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The documentation for this class was generated from the following files:

• TcpCrcInsertionHook.h
• TcpCrcInsertionHook.cc