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;;                                                                 ;;

;;  UDP.INC                                                        ;;

;;                                                                 ;;

;;  UDP 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

;

;       udp_rx      Handles received IP packets with the UDP protocol

;

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

;

;   UDP Payload ( Data field in IP datagram )

;

;    0                   1                   2                   3

;    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

;

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

;   |       Source Port             |      Destination Port         |

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

;   | Length ( UDP Header + Data )  |           Checksum            |

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

;   |       UDP Data                                                |

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

;

struc UDP_PACKET

{  .SourcePort       dw  ?  ;+00

   .DestinationPort  dw  ?  ;+02

   .Length           dw  ?  ;+04 - Length of (UDP Header + Data)

   .Checksum         dw  ?  ;+06

   .Data             db  ?  ;+08

}

virtual at 0

  UDP_PACKET UDP_PACKET

end virtual

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

;   Function

;      udp_rx  [by Johnny_B]

;

;   Description

;       UDP protocol handler

;       This is a kernel function, called by ip_rx

;       IP buffer address given in edx

;          IP buffer number in eax

;          Free up (or re-use) IP buffer when finished

;

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

udp_rx:

    push    eax

    ; First validate the header & checksum. Discard buffer if error

    ; Look for a socket where

    ; IP Packet UDP Destination Port = local Port

    ; IP Packet SA = Remote IP

    movzx   ebx, word [edx + 22]   ; get the local port from

                                  ; the IP packet's UDP header

    mov     eax, SOCKETBUFFSIZE * NUM_SOCKETS

    mov     ecx, NUM_SOCKETS

fs1:

    sub     eax, SOCKETBUFFSIZE

    cmp     [eax + sockets + 12], bx ; bx will hold the 'wrong' value,

                                    ; but the comparision is correct

    loopnz  fs1                     ; Return back if no match

    jz      fs_done

    ; No match, so exit

    jmp     udprx_001

fs_done:

    ; For dhcp, we must allow any remote server to respond.

    ; I will accept the first incoming response to be the one

    ; I bind to, if the socket is opened with a destination IP address of

    ; 255.255.255.255

    mov     ebx, [eax + sockets + 16]

    cmp     ebx, 0xffffffff

    je      udprx_002

    mov     ebx, [edx + 12]    ; get the Source address from the IP packet

    cmp     [eax + sockets + 16], ebx

    jne     udprx_001          ; Quit if the source IP is not valid

udprx_002:

    ; OK - we have a valid UDP packet for this socket.

    ; First, update the sockets remote port number with the incoming msg

    ; - it will have changed

    ; from the original ( 69 normally ) to allow further connects

    movzx   ebx, word [edx + 20]      ; get the UDP source port

                                     ; ( was 69, now new )

    mov     [eax + sockets + 20], bx

    ; Now, copy data to socket. We have socket address as [eax + sockets].

    ; We have IP packet in edx

    ; get # of bytes in ecx

    movzx   ecx, byte [edx + 3]  ; total length of IP packet. Subtract

    mov     ch, byte [edx + 2]   ; 20 + 8 gives data length

    sub     ecx, 28

    mov     ebx, eax

    add     ebx, sockets         ; ebx = address of actual socket

    mov     eax, [ebx+ 4]       ; get socket owner PID

    push    eax

    mov     eax, [ebx + 24]      ; get # of bytes already in buffer

    add     [ebx + 24], ecx      ; increment the count of bytes in buffer

    ; point to the location to store the data

    add     ebx, eax

    add     ebx, SOCKETHEADERSIZE

    ; ebx = location for first byte, ecx has count,

    ; edx points to data

    add     edx, 28        ; edx now points to the data

    mov     edi, ebx

    mov     esi, edx

    cld

    rep     movsb          ; copy the data across

    ; flag an event to the application

    pop     eax

    mov     ecx,1

    mov     esi,TASK_DATA+TASKDATA.pid

newsearch:

    cmp     [esi],eax

    je      foundPID

    inc     ecx

    add     esi,0x20

    cmp     ecx,[TASK_COUNT]

    jbe     newsearch

foundPID:

    shl     ecx,8

    or      dword [ecx+SLOT_BASE+APPDATA.event_mask],dword 10000000b ; stack event

    mov     [check_idle_semaphore],200

udprx_001:

    pop     eax

    call    freeBuff    ; Discard the packet

    ret