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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;                                                                 ;;
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;;  UDP.INC                                                        ;;
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;;                                                                 ;;
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;;  UDP Processes for Menuet OS  TCP/IP stack                      ;;
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;;                                                                 ;;
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;;  Version 0.3  29 August 2002                                    ;;
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;;                                                                 ;;
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;;  Copyright 2002 Mike Hibbett, mikeh@oceanfree.net               ;;
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;;                                                                 ;;
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;;  See file COPYING for details                                   ;;
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;;                                                                 ;;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;*******************************************************************
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;   Interface
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;
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;       udp_rx      Handles received IP packets with the UDP protocol
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;
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;*******************************************************************
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;***************************************************************************
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;   Function
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;      udp_rx
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;
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;   Description
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;       UDP protocol handler
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;       This is a kernel function, called by ip_rx
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;       IP buffer address given in edx
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;          Free up (or re-use) IP buffer when finished
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;
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;***************************************************************************
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udp_rx:
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    push    eax
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    ; First validate the header & checksum. Discard buffer if error
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    ; Look for a socket where
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    ; IP Packet UDP Destination Port = local Port
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    ; IP Packet SA = Remote IP
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    movzx   ebx, word [edx + 22]   ; get the local port from
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                                  ; the IP packet's UDP header
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    mov     eax, SOCKETBUFFSIZE * NUM_SOCKETS
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    mov     ecx, NUM_SOCKETS
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fs1:
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    sub     eax, SOCKETBUFFSIZE
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    cmp     [eax + sockets + 12], bx ; bx will hold the 'wrong' value,
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                                    ; but the comparision is correct
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    loopnz  fs1                     ; Return back if no match
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    jz      fs_done
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    ; No match, so exit
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    jmp     udprx_001
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fs_done:
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    ; For dhcp, we must allow any remote server to respond.
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    ; I will accept the first incoming response to be the one
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    ; I bind to, if the socket is opened with a destination IP address of
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    ; 255.255.255.255
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    mov     ebx, [eax + sockets + 16]
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    cmp     ebx, 0xffffffff
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    je      udprx_002
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    mov     ebx, [edx + 12]    ; get the Source address from the IP packet
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    cmp     [eax + sockets + 16], ebx
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    jne     udprx_001          ; Quit if the source IP is not valid
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udprx_002:
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    ; OK - we have a valid UDP packet for this socket.
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    ; First, update the sockets remote port number with the incoming msg
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    ; - it will have changed
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    ; from the original ( 69 normally ) to allow further connects
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    movzx   ebx, word [edx + 20]      ; get the UDP source port
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                                     ; ( was 69, now new )
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    mov     [eax + sockets + 20], bx
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    ; Now, copy data to socket. We have socket address as [eax + sockets].
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    ; We have IP packet in edx
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    ; get # of bytes in ecx
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    movzx   ecx, byte [edx + 3]  ; total length of IP packet. Subtract
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    mov     ch, byte [edx + 2]   ; 20 + 8 gives data length
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    sub     ecx, 28
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    mov     ebx, eax
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    add     ebx, sockets         ; ebx = address of actual socket
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    mov     eax, [ebx+ 4]       ; get socket owner PID
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    push    eax
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    mov     eax, [ebx + 24]      ; get # of bytes already in buffer
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    add     [ebx + 24], ecx      ; increment the count of bytes in buffer
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    ; point to the location to store the data
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    add     ebx, eax
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    add     ebx, SOCKETHEADERSIZE
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    ; ebx = location for first byte, ecx has count,
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    ; edx points to data
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    add     edx, 28        ; edx now points to the data
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    mov     edi, ebx
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    mov     esi, edx
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    cld
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    rep     movsb          ; copy the data across
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    ; flag an event to the application
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    pop     eax
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    mov     ecx,1
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    mov     esi,0x3020+TASKDATA.pid
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newsearch:
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    cmp     [esi],eax
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    je      foundPID
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    inc     ecx
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    add     esi,0x20
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    cmp     ecx,[0x3004]
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    jbe     newsearch
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foundPID:
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    shl     ecx,8
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    or      dword [ecx+0x80000+APPDATA.event_mask],dword 10000000b ; stack event
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    mov     [check_idle_semaphore],200
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udprx_001:
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    pop     eax
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    call    freeBuff    ; Discard the packet
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    ret
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