PAGE 60,132
NAME PKT_RX

ifdef ??version        ; using TASM

  masm
  jumps
endif

PUBLIC _pktDrop, _pktRxBuf, _pktTxBuf,    _pktTemp
PUBLIC _rxOutOfs, _rxInOfs, _PktReceiver, _pktRxEnd

;

; these sizes MUST be equal to the sizes in PKTDRVR.H

;


RX_BUF_SIZE = 1500      ; max message size on Ethernet

TX_BUF_SIZE = 1500

ifdef DOSX
 .386
  NUM_RX_BUF = 32       ; # of RX element buffers

  _TEXT   SEGMENT PUBLIC DWORD USE16 'CODE'
  _TEXT   ENDS
  _DATA   SEGMENT PUBLIC DWORD USE16 'CODE'
  _DATA   ENDS
  D_SEG   EQU <_TEXT SEGMENT>
  D_END   EQU <_TEXT ENDS>
  ASSUME  CS:_TEXT,DS:_TEXT
else
 .286
  NUM_RX_BUF = 10
  _TEXT   SEGMENT PUBLIC DWORD 'CODE'
  _TEXT   ENDS
  _DATA   SEGMENT PUBLIC DWORD 'DATA'
  _DATA   ENDS
  D_SEG   EQU <_DATA SEGMENT>
  D_END   EQU <_DATA ENDS>
  ASSUME  CS:_TEXT,DS:_DATA
endif

;-------------------------------------------


D_SEG

RX_ELEMENT     STRUC
   firstCount  dw  0                          ; # of bytes on 1st call

   secondCount dw  0                          ; # of bytes on 2nd call

   handle      dw  0                          ; handle for upcall

   destinAdr   db  6           dup (0)        ; packet destination address

   sourceAdr   db  6           dup (0)        ; packet source address

   protocol    dw  0                          ; packet protocol number

   rxBuffer    db  RX_BUF_SIZE dup (0)        ; RX buffer

ENDS
               align 4
_rxOutOfs      dw  offset _pktRxBuf           ; ring buffer offsets

_rxInOfs       dw  offset _pktRxBuf           ; into _pktRxBuf

_pktDrop       dw  0,0                        ; packet drop counter

_pktTemp       db  20                dup (0)  ; temp work area

_pktTxBuf      db  (TX_BUF_SIZE+14)  dup (0)  ; TX buffer

_pktRxBuf      RX_ELEMENT NUM_RX_BUF dup (<>) ; RX structures

 LAST_OFS      = offset $

 screenSeg     dw  0B800h
 newInOffset   dw  0

 fanChars      db  '-\|/'
 fanIndex      dw  0

D_END

_TEXT SEGMENT


SHOW_RX  MACRO
         push es
         push bx
         mov bx, screenSeg
         mov es, bx                    ;; r-mode segment of colour screen

         mov di, 158                   ;; upper right corner - 1

         mov bx, fanIndex
         mov al, fanChars[bx]          ;; get write char

         mov ah, 15                    ;;  and white colour

         stosw                         ;; write to screen at ES:EDI

         inc fanIndex                  ;; update next index

         and fanIndex, 3
         pop bx
         pop es
ENDM

;------------------------------------------------------------------------

;

; This macro return ES:DI to tail of Rx queue


ENQUEUE  MACRO
         LOCAL @noWrap
         mov ax, _rxInOfs              ;; DI = current in-offset

         add ax, SIZE RX_ELEMENT       ;; point to next _pktRxBuf buffer

         cmp ax, LAST_OFS              ;; pointing past last ?

         jb  @noWrap                   ;; no - jump

         lea ax, _pktRxBuf             ;; yes, point to 1st buffer

         align 4
@noWrap: cmp ax, _rxOutOfs             ;; in-ofs = out-ofs ?

         je  @dump                     ;; yes, queue is full

         mov di, _rxInOfs              ;; ES:DI -> buffer at queue input

         mov newInOffset, ax           ;; remember new input offset


   ;; NOTE. rxInOfs is updated after the packet has been copied

   ;; to ES:DI (= DS:SI on 2nd call) by the packet driver


ENDM

;------------------------------------------------------------------------

;

; This routine gets called by the packet driver twice:

;   1st time (AX=0) it requests an address where to put the packet

;

;   2nd time (AX=1) the packet has been copied to this location (DS:SI)

;   BX has client handle (stored in RX_ELEMENT.handle).

;   CX has # of bytes in packet on both call. They should be equal.

;

; A test for equality is done by putting CX in _pktRxBuf [n].firstCount

; and _pktRxBuf[n].secondCount, and CL on first call in

; _pktRxBuf[n].rxBuffer[CX]. These values are checked in "PktReceive"

; (PKTDRVR.C)

;

;---------------------------------------------------------------------


_PktReceiver:
         pushf
         cli                         ; no distraction wanted !

         push ds
         push bx
ifdef DOSX
         mov bx, cs
else
         mov bx, SEG _DATA
endif
         mov ds, bx
         mov es, bx                  ; ES = DS = CS or seg _DATA

         pop bx                      ; restore handle


         cmp ax, 0                   ; first call? (AX=0)

         jne @post                   ; AX=1: second call, do post process


ifdef DEBUG
         SHOW_RX                     ; show that a packet is received

endif
         cmp cx, RX_BUF_SIZE+14      ; size OK ?

         ja  @skip                   ; no, packet to large for us


         ENQUEUE                     ; ES:DI -> _pktRxBuf[n]


         mov [di].firstCount, cx     ; remember the first count.

         mov [di].handle, bx         ; remember the handle.

         add di, 6                   ; ES:DI -> _pktRxBuf[n].destinAdr

         pop ds
         popf
         retf                        ; far return to driver with ES:DI


         align 4
@dump:   inc _pktDrop[0]             ; discard the packet on 1st call

         adc _pktDrop[2], 0          ; increment packets lost


@skip:   xor di, di                  ; return ES:DI = NIL pointer

         xor ax, ax
         mov es, ax
         pop ds
         popf
         retf

         align 4
@post:   or si, si                   ; DS:SI->_pktRxBuf[n][n].destinAdr

         jz @discard                 ; make sure we don't use NULL-pointer


         sub si, 6                   ; DS:SI -> _pktRxBuf[n].destinAdr

       ;

       ; push si

       ; push [si].firstCount

       ; call bpf_filter_match       ; run the filter here some day?

       ; add sp, 4

       ; cmp ax, 0

       ; je  @discard


         mov [si].secondCount, cx
         mov ax, newInOffset
         mov _rxInOfs, ax            ; update _pktRxBuf input offset


         align 4
@discard:pop ds
         popf
         retf

_pktRxEnd  db 0                      ; marker for end of r-mode code/data


_TEXT ENDS

END