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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                                   ;;

;;                                                                 ;;

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

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

;   Interface

;

;       ip_rx       processes all packets received by the network layer

;                   It calls the appropriate protocol handler

;

;

;

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

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

;   Function

;      ip_rx

;

;   Description

;       Handles received IP packets

;       This is a kernel function, called by stack_handler

;

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

ip_rx:

    ; Look for a buffer to tx

    mov     eax, IPIN_QUEUE

    call    dequeue

    cmp     ax, NO_BUFFER

    je      ipr_exit         ; Exit if no buffer available

    push    eax

    ; convert buffer pointer eax to the absolute address

    mov     ecx, IPBUFFSIZE

    mul     ecx

    add     eax, IPbuffs

    mov     edx, eax  ; Save the address in  edx for use by future processes

    ; Validate the IP checksum

    mov     ebx, edx

    mov     ah, [ebx + 10]

    mov     al, [ebx + 11]      ; Get the checksum in intel format

    mov     [ebx + 10], 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

    mov     ebx, edx

    mov     [checkAdd1], ebx

    mov     [checkSize1], word 20

    mov     [checkAdd2], dword 0

    mov     [checkSize2], word 0

    call    checksum           ; Recalculate IP checksum

    cmp     ax, [checkResult]

    jnz     ipr_dump

    ; If the IP address is 255.255.255.255, accept it

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

    mov     eax, [edx + 16]

    cmp     eax, 0xffffffff

    je      ipr_p0

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

    cmp     eax, [stack_ip]

    jnz     ipr_dump

ipr_p0:

    mov     al, [edx]

    and     al, 0x0f

    cmp     al, 0x05

    jnz     ipr_dump

    cmp     [edx+8], byte 0

    jz      ipr_dump

    mov     ax, [edx + 6]

    and     ax, 0xFFBF

    cmp     ax, 0

    jnz     ipr_dump

    ; Check the protocol, and call the appropriate handler

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

    mov     al, [edx + 9]

    cmp     al , PROTOCOL_ICMP

    jnz     ipr_p1

    pop     eax

    call    icmp_rx

    jmp     ipr_exit

ipr_p1:

    cmp     al , PROTOCOL_TCP

    jnz     ipr_p2

    pop     eax

    call    tcp_rx

    jmp     ipr_exit

ipr_p2:

    cmp     al , PROTOCOL_UDP

    jnz     ipr_dump

    pop     eax

    call    udp_rx

    jmp     ipr_exit

ipr_dump:

    ; No protocol handler available, so

    ; silently dump the packet, freeing up the queue buffer

;    inc     dword [dumped_rx_count]

    pop     eax

    call    freeBuff

ipr_exit:

    ret

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

;   Function

;      icmp_rx

;

;   Description

;       ICMP protocol handler

;       This is a kernel function, called by ip_rx

;       edx contains the address of the buffer in use.

;       This buffer must be reused or marked as empty afterwards

;

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

icmp_rx:

    cmp     [edx + 20], byte 8 ; Is this an echo request? discard if not

    jz      icmp_echo

    call    freeBuff

    jmp     icmp_exit

icmp_echo:

    push    eax

    mov     [edx + 10], word 0  ; I think this was already done by IP rx

    ; swap the source and destination addresses

    mov     ecx, [edx + 16]

    mov     eax, [edx + 12]

    mov     [edx + 16], eax

    mov     [edx + 12], ecx

    ; recaluculate the IP header checksum

    mov     ebx, edx

    mov     [checkAdd1], ebx

    mov     [checkSize1], word 20

    mov     [checkAdd2], dword 0

    mov     [checkSize2], word 0

    call    checksum

    mov     ax, [checkResult]

    mov     [edx + 10], ah

    mov     [edx + 11], al      ; ?? correct byte order?

    mov     [edx + 20], byte 0  ; change the request to a response

    mov     [edx + 22], word 0  ; clear ICMP checksum prior to re-calc

    ; Calculate the length of the ICMP data ( IP payload)

    mov     ah, [edx + 2]

    mov     al, [edx + 3]

    sub     ax, 20

    mov     [checkSize1], ax

    mov     ebx, edx

    add     ebx, 20

    mov     [checkAdd1], ebx

    mov     [checkAdd2], dword 0

    mov     [checkSize2], word 0

    call    checksum

    mov     ax, [checkResult]

    mov     [edx + 22], ah

    mov     [edx + 23], al

    ; Queue packet for transmission

    pop     ebx

    mov     eax, NET1OUT_QUEUE

    call    queue

icmp_exit:

    ret