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;;                                                                 ;;

;;  IP.INC                                                         ;;

;;                                                                 ;;

;;  IP Processes for Menuet OS  TCP/IP stack                       ;;

;;                                                                 ;;

;;  Version 0.3  29 August 2002                                    ;;

;;                                                                 ;;

;;  Copyright 2002 Mike Hibbett, mikeh@oceanfree.net               ;;

;;                                                                 ;;

;;  See file COPYING for details                                   ;;

;;                                                                 ;;

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$Revision: 593 $

; IP underlying protocols numbers

PROTOCOL_ICMP     equ      1

PROTOCOL_TCP      equ      6

PROTOCOL_UDP      equ      17

struc IP_PACKET

{  .VersionAndIHL           db   ?  ;+00 - Version[0-3 bits] and IHL(header length)[4-7 bits]

   .TypeOfService           db   ?  ;+01

   .TotalLength             dw   ?  ;+02

   .Identification          dw   ?  ;+04

   .FlagsAndFragmentOffset  dw   ?  ;+06 - Flags[0-2] and FragmentOffset[3-15]

   .TimeToLive              db   ?  ;+08

   .Protocol                db   ?  ;+09

   .HeaderChecksum          dw   ?  ;+10

   .SourceAddress           dd   ?  ;+12

   .DestinationAddress      dd   ?  ;+16

   .DataOrOptional          dd   ?  ;+20

}

virtual at 0

  IP_PACKET IP_PACKET

end virtual

;*******************************************************************

;   Interface

;

;       ip_rx       processes all packets received by the network layer

;                   It calls the appropriate protocol handler

;

;

;

;*******************************************************************

;

;   IP Packet after reception - Normal IP packet format

;

;           0               1               2               3

;    0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7

;

;   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

;0  |Version|  IHL  |Type of Service|       Total Length            |

;   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

;4  |         Identification        |Flags|      Fragment Offset    |

;   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

;8  |  Time to Live |    Protocol   |         Header Checksum       |

;   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

;12 |                       Source Address                          |

;   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

;16 |                    Destination Address                        |

;   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

;20 |      Data                                                     |

;   +-+-+-..........                                               -+

;

;

;    [smb] attention! according to RFC 791 IP packet may have 'options' sections,

; so we can't simply think, that data have offset 20. We must calculate offset from

; IHL field

;

macro	GET_IHL reg, header_addr

{

	movzx	reg, byte [header_addr]

	; we need 4-7 bits, so....

	and	reg, 0x0000000F

	; IHL keeps number of octets, so we need to << 2 'reg'

	shl     reg, 2

}

;***************************************************************************

;   Function

;      ip_rx

;

;   Description

;       This is a kernel function, called by stack_handler

;       Processes all IP-packets received by the network layer

;       It calls the appropriate protocol handler

;

;***************************************************************************

proc ip_rx stdcall

local buffer_number dd ?

    ; Look for a buffer to tx

    mov     eax, IPIN_QUEUE

    call    dequeue

    cmp     ax, NO_BUFFER

    je      .exit         ; Exit if no buffer available

    mov     [buffer_number], eax    ;save buffer number

    ; convert buffer pointer eax to the absolute address

    imul    eax, IPBUFFSIZE

    add     eax, IPbuffs

    mov     ebx, eax  ; ebx=pointer to IP_PACKET

    ; Validate the IP checksum

    mov     dx, word[ebx + IP_PACKET.HeaderChecksum]

    xchg    dh,dl          ; Get the checksum in intel format

    mov     [ebx + IP_PACKET.HeaderChecksum], word 0  ; clear checksum field - need to when

                                ; recalculating checksum

    ;  this needs two data pointers and two size #.

    ;  2nd pointer can be of length 0

    GET_IHL ecx, ebx + IP_PACKET.VersionAndIHL ;get packet length in ecx

    stdcall checksum_jb, ebx, ecx   ;buf_ptr, buf_size

    cmp     dx, ax

    mov     edx, ebx ; EDX (IP-BUFFER POINTER) WILL BE USED FOR *_rx HANDLERS BELOW!!!

    jnz     .dump  ;if CHECKSUM isn't valid then dump packet

    ; Validate the IP address, if it isn't broadcast

    mov     eax, [stack_ip]

    cmp     dword[ebx + IP_PACKET.DestinationAddress], eax

    je      @f

    ; If the IP address is 255.255.255.255, accept it

    ; - it is a broadcast packet, which we need for dhcp

    cmp     dword[ebx + IP_PACKET.DestinationAddress], 0xffffffff

    jne     .dump

  @@:

    mov     al, [ebx + IP_PACKET.VersionAndIHL]

    and     al, 0x0f  ;get IHL(header length)

    cmp     al, 0x05  ;if IHL!= 5*4(20 bytes)

    jnz     .dump     ;then dump it

    cmp     byte[ebx + IP_PACKET.TimeToLive], byte 0

    je      .dump     ;if TTL==0 then dump it

    mov     ax, word[ebx + IP_PACKET.FlagsAndFragmentOffset]

    and     ax, 0xFFBF   ;get flags

    cmp     ax, 0        ;if some flags was set then we dump this packet

    jnz     .dump        ;the flags should be used for fragmented packets

    ; Check the protocol, and call the appropriate handler

    ; Each handler will re-use or free the queue buffer as appropriate

    mov     al, [ebx + IP_PACKET.Protocol]

    cmp     al , PROTOCOL_TCP

    jne     .not_tcp

    DEBUGF  1,"K : ip_rx - TCP packet\n"

    mov     eax, dword[buffer_number]

    call    tcp_rx

    jmp     .exit

  .not_tcp:

    cmp     al, PROTOCOL_UDP

    jne     .not_udp

    DEBUGF  1,"K : ip_rx - UDP packet\n"

    mov     eax, dword[buffer_number]

    call    udp_rx

    jmp     .exit

  .not_udp:

    cmp     al , PROTOCOL_ICMP

    jne     .dump              ;protocol ain't supported

    DEBUGF  1,"K : ip_rx - ICMP packet\n"

    ;GET_IHL ecx, ebx + IP_PACKET.VersionAndIHL ;get packet length in ecx

    mov     eax, dword[buffer_number]

    stdcall icmp_rx,eax,ebx,ecx  ;buffer_number,IPPacketBase,IPHeaderLength

    jmp     .exit

.dump:

    ; No protocol handler available, so

    ; silently dump the packet, freeing up the queue buffer

    inc     dword [dumped_rx_count]

    mov     eax, dword[buffer_number]

    call    freeBuff

  .exit:

    ret

endp