icmp.c

ReactOS是一些高手根据Windows XP的内核编写出的类XP。内核实现机理和API函数调用几乎相同。甚至可以兼容XP的程序。喜欢研究系统内核的人可以看一看。

/*
 * COPYRIGHT:   See COPYING in the top level directory
 * PROJECT:     ReactOS TCP/IP protocol driver
 * FILE:        network/icmp.c
 * PURPOSE:     Internet Control Message Protocol routines
 * PROGRAMMERS: Casper S. Hornstrup ([e-mail])
 * REVISIONS:
 *   CSH 01/08-2000 Created
 */

#include "precomp.h"


VOID SendICMPComplete(
    PVOID Context,
    PNDIS_PACKET Packet,
    NDIS_STATUS NdisStatus)
/*
 * FUNCTION: ICMP datagram transmit completion handler
 * ARGUMENTS:
 *     Context    = Pointer to context infomation (IP_PACKET)
 *     Packet     = Pointer to NDIS packet
 *     NdisStatus = Status of transmit operation
 * NOTES:
 *     This routine is called by IP when a ICMP send completes
 */
{
    TI_DbgPrint(DEBUG_ICMP, ("Freeing NDIS packet (%X).\n", Packet));

    /* Free packet */
    FreeNdisPacket(Packet);

    TI_DbgPrint(DEBUG_ICMP, ("Done\n"));
}


PIP_PACKET PrepareICMPPacket(
    PIP_INTERFACE Interface,
    PIP_PACKET IPPacket,
    PIP_ADDRESS Destination,
    PCHAR Data,
    UINT DataSize)
/*
 * FUNCTION: Prepares an ICMP packet
 * ARGUMENTS:
 *     NTE         = Pointer to net table entry to use
 *     Destination = Pointer to destination address
 *     DataSize    = Size of dataarea
 * RETURNS:
 *     Pointer to IP packet, NULL if there is not enough free resources
 */
{
    PNDIS_PACKET NdisPacket;
    NDIS_STATUS NdisStatus;
    PIPv4_HEADER IPHeader;
    ULONG Size;

    TI_DbgPrint(DEBUG_ICMP, ("Called. DataSize (%d).\n", DataSize));

    /* No special flags */
    IPPacket->Flags = 0;

    Size = MaxLLHeaderSize + sizeof(IPv4_HEADER) + DataSize;

    /* Allocate NDIS packet */
    NdisStatus = AllocatePacketWithBuffer( &NdisPacket, NULL, Size );

    if( !NT_SUCCESS(NdisStatus) ) return NULL;

    IPPacket->NdisPacket = NdisPacket;

    GetDataPtr( IPPacket->NdisPacket, MaxLLHeaderSize,
		(PCHAR *)&IPPacket->Header, &IPPacket->ContigSize );

    IPPacket->Data = ((PCHAR)IPPacket->Header) + IPPacket->HeaderSize;

    TI_DbgPrint(DEBUG_ICMP, ("Size (%d). Data at (0x%X).\n", Size, Data));
    TI_DbgPrint(DEBUG_ICMP, ("NdisPacket at (0x%X).\n", NdisPacket));

    IPPacket->HeaderSize = sizeof(IPv4_HEADER);
    IPPacket->TotalSize  = Size - MaxLLHeaderSize;

    TI_DbgPrint(DEBUG_ICMP, ("Copying Address: %x -> %x\n",
			     &IPPacket->DstAddr, Destination));

    RtlCopyMemory(&IPPacket->DstAddr, Destination, sizeof(IP_ADDRESS));
    RtlCopyMemory(IPPacket->Data, Data, DataSize);

    /* Build IPv4 header. FIXME: IPv4 only */

    IPHeader = (PIPv4_HEADER)IPPacket->Header;

    /* Version = 4, Length = 5 DWORDs */
    IPHeader->VerIHL = 0x45;
    /* Normal Type-of-Service */
    IPHeader->Tos = 0;
    /* Length of data and header */
    IPHeader->TotalLength = WH2N((USHORT)DataSize + sizeof(IPv4_HEADER));
    /* Identification */
    IPHeader->Id = (USHORT)Random();
    /* One fragment at offset 0 */
    IPHeader->FlagsFragOfs = 0;
    /* Time-to-Live is 128 */
    IPHeader->Ttl = 128;
    /* Internet Control Message Protocol */
    IPHeader->Protocol = IPPROTO_ICMP;
    /* Checksum is 0 (for later calculation of this) */
    IPHeader->Checksum = 0;
    /* Source address */
    IPHeader->SrcAddr = Interface->Unicast.Address.IPv4Address;
    /* Destination address */
    IPHeader->DstAddr = Destination->Address.IPv4Address;


    TI_DbgPrint(MID_TRACE,("Leaving\n"));

    return IPPacket;
}


VOID ICMPReceive(
    PIP_INTERFACE Interface,
    PIP_PACKET IPPacket)
/*
 * FUNCTION: Receives an ICMP packet
 * ARGUMENTS:
 *     NTE      = Pointer to net table entry which the packet was received on
 *     IPPacket = Pointer to an IP packet that was received
 */
{
    PICMP_HEADER ICMPHeader;

    TI_DbgPrint(DEBUG_ICMP, ("Called.\n"));

    ICMPHeader = (PICMP_HEADER)IPPacket->Data;

    TI_DbgPrint(DEBUG_ICMP, ("Size (%d).\n", IPPacket->TotalSize));

    TI_DbgPrint(DEBUG_ICMP, ("HeaderSize (%d).\n", IPPacket->HeaderSize));

    TI_DbgPrint(DEBUG_ICMP, ("Type (%d).\n", ICMPHeader->Type));

    TI_DbgPrint(DEBUG_ICMP, ("Code (%d).\n", ICMPHeader->Code));

    TI_DbgPrint(DEBUG_ICMP, ("Checksum (0x%X).\n", ICMPHeader->Checksum));

    /* Checksum ICMP header and data */
    if (!IPv4CorrectChecksum(IPPacket->Data, IPPacket->TotalSize - IPPacket->HeaderSize)) {
        TI_DbgPrint(DEBUG_ICMP, ("Bad ICMP checksum.\n"));
        /* Discard packet */
        return;
    }

    switch (ICMPHeader->Type) {
    case ICMP_TYPE_ECHO_REQUEST:
	ICMPReply( Interface, IPPacket, ICMP_TYPE_ECHO_REPLY, 0 );
        return;

    case ICMP_TYPE_ECHO_REPLY:
        break;

    default:
        TI_DbgPrint(DEBUG_ICMP,
		    ("Discarded ICMP datagram of unknown type %d.\n",
		     ICMPHeader->Type));
        /* Discard packet */
        break;
    }
}


VOID ICMPTransmit(
    PIP_PACKET IPPacket,
    PIP_TRANSMIT_COMPLETE Complete,
    PVOID Context)
/*
 * FUNCTION: Transmits an ICMP packet
 * ARGUMENTS:
 *     NTE      = Pointer to net table entry to use (NULL if don't care)
 *     IPPacket = Pointer to IP packet to transmit
 */
{
    PNEIGHBOR_CACHE_ENTRY NCE;

    TI_DbgPrint(DEBUG_ICMP, ("Called.\n"));

    /* Calculate checksum of ICMP header and data */
    ((PICMP_HEADER)IPPacket->Data)->Checksum = (USHORT)
        IPv4Checksum(IPPacket->Data, IPPacket->TotalSize - IPPacket->HeaderSize, 0);

    /* Get a route to the destination address */
    if ((NCE = RouteGetRouteToDestination(&IPPacket->DstAddr))) {
        /* Send the packet */
	IPSendDatagram(IPPacket, NCE, Complete, Context);
    } else {
        /* No route to destination (or no free resources) */
        TI_DbgPrint(DEBUG_ICMP, ("No route to destination address 0x%X.\n",
				 IPPacket->DstAddr.Address.IPv4Address));
        /* Discard packet */
	Complete( Context, IPPacket->NdisPacket, NDIS_STATUS_NOT_ACCEPTED );
    }
}


VOID ICMPReply(
    PIP_INTERFACE Interface,
    PIP_PACKET IPPacket,
    UCHAR Type,
    UCHAR Code)
/*
 * FUNCTION: Transmits an ICMP packet in response to an incoming packet
 * ARGUMENTS:
 *     NTE      = Pointer to net table entry to use
 *     IPPacket = Pointer to IP packet that was received
 *     Type     = ICMP message type
 *     Code     = ICMP message code
 * NOTES:
 *     We have received a packet from someone and is unable to
 *     process it due to error(s) in the packet or we have run out
 *     of resources. We transmit an ICMP message to the host to
 *     notify him of the problem
 */
{
    UINT DataSize, PayloadSize;
    IP_PACKET NewPacket = *IPPacket;

    TI_DbgPrint(DEBUG_ICMP, ("Called. Type (%d)  Code (%d).\n", Type, Code));

    DataSize = IPPacket->TotalSize - IPPacket->HeaderSize;
    PayloadSize = DataSize - sizeof(ICMP_HEADER);
    if ((PayloadSize) > 576) {
	PayloadSize = 576;
        DataSize = PayloadSize + sizeof(ICMP_HEADER);
    }

    if( !PrepareICMPPacket(Interface, &NewPacket, &IPPacket->SrcAddr,
			   IPPacket->Data, DataSize) ) return;

    ((PICMP_HEADER)NewPacket.Data)->Type     = Type;
    ((PICMP_HEADER)NewPacket.Data)->Code     = Code;
    ((PICMP_HEADER)NewPacket.Data)->Checksum = 0;

    ICMPTransmit(&NewPacket, SendICMPComplete, NULL);
}

/* EOF */