The Tcpdump Group git mirrors - libpcap/blob - msdos/pkt_rx1.s

   1 ;
   2 ; This file requires NASM 0.97+ to assemble
   3 ;
   4 ; Currently used only for djgpp + DOS4GW targets
   5 ;
   6 ; these sizes MUST be equal to the sizes in PKTDRVR.H
   7 ;
   8 %define  ETH_MTU     1500                  ; max data size on Ethernet
   9 %define  ETH_MIN     60                    ; min/max total frame size
  10 %define  ETH_MAX     (ETH_MTU+2*6+2)
  11 %define  NUM_RX_BUF  32                    ; # of RX element buffers
  12 %define  RX_SIZE     (ETH_MAX+6)           ; sizeof(RX_ELEMENT) = 1514+6
  13 %idefine offset
  14
  15 struc RX_ELEMENT
  16       .firstCount  resw 1                  ; # of bytes on 1st call
  17       .secondCount resw 1                  ; # of bytes on 2nd call
  18       .handle      resw 1                  ; handle for upcall
  19     ; .timeStamp   resw 4                  ; 64-bit RDTSC value
  20       .destinAdr   resb 6                  ; packet destination address
  21       .sourceAdr   resb 6                  ; packet source address
  22       .protocol    resw 1                  ; packet protocol number
  23       .rxBuffer    resb ETH_MTU            ; RX buffer
  24 endstruc
  25
  26 ;-------------------------------------------
  27
  28 [org 0]  ; assemble to .bin file
  29
  30 _rxOutOfs   dw   offset _pktRxBuf          ; ring buffer offsets
  31 _rxInOfs    dw   offset _pktRxBuf          ; into _pktRxBuf
  32 _pktDrop    dw   0,0                       ; packet drop counter
  33 _pktTemp    resb 20                        ; temp work area
  34 _pktTxBuf   resb (ETH_MAX)                 ; TX buffer
  35 _pktRxBuf   resb (RX_SIZE*NUM_RX_BUF)      ; RX structures
  36  LAST_OFS   equ  $
  37
  38 screenSeg   dw  0B800h
  39 newInOffset dw  0
  40
  41 fanChars    db  '-\|/'
  42 fanIndex    dw  0
  43
  44 %macro SHOW_RX 0
  45        push es
  46        push bx
  47        mov bx, [screenSeg]
  48        mov es, bx                    ;; r-mode segment of colour screen
  49        mov di, 158                   ;; upper right corner - 1
  50        mov bx, [fanIndex]
  51        mov al, [fanChars+bx]         ;; get write char
  52        mov ah, 15                    ;;  and white colour
  53        cld                           ;; Needed?
  54        stosw                         ;; write to screen at ES:EDI
  55        inc word [fanIndex]           ;; update next index
  56        and word [fanIndex], 3
  57        pop bx
  58        pop es
  59 %endmacro
  60
  61 ;PutTimeStamp
  62 ;       rdtsc
  63 ;       mov [si].timeStamp, eax
  64 ;       mov [si+4].timeStamp, edx
  65 ;       ret
  66
  67
  68 ;------------------------------------------------------------------------
  69 ;
  70 ; This routine gets called by the packet driver twice:
  71 ;   1st time (AX=0) it requests an address where to put the packet
  72 ;
  73 ;   2nd time (AX=1) the packet has been copied to this location (DS:SI)
  74 ;   BX has client handle (stored in RX_ELEMENT.handle).
  75 ;   CX has # of bytes in packet on both call. They should be equal.
  76 ; A test for equality is done by putting CX in _pktRxBuf [n].firstCount
  77 ; and _pktRxBuf[n].secondCount, and CL on first call in
  78 ; _pktRxBuf[n].rxBuffer[CX]. These values are checked in "PktReceive"
  79 ; (PKTDRVR.C)
  80 ;
  81 ;---------------------------------------------------------------------
  82
  83 _PktReceiver:
  84          pushf
  85          cli                         ; no distraction wanted !
  86          push ds
  87          push bx
  88          mov bx, cs
  89          mov ds, bx
  90          mov es, bx                  ; ES = DS = CS or seg _DATA
  91          pop bx                      ; restore handle
  92
  93          cmp ax, 0                   ; first call? (AX=0)
  94          jne @post                   ; AX=1: second call, do post process
  95
  96 %ifdef DEBUG
  97          SHOW_RX                     ; show that a packet is received
  98 %endif
  99
 100          cmp cx, ETH_MAX             ; size OK ?
 101          ja  @skip                   ; no, too big
 102
 103          mov ax, [_rxInOfs]
 104          add ax, RX_SIZE
 105          cmp ax, LAST_OFS
 106          jb  @noWrap
 107          mov ax, offset _pktRxBuf
 108 @noWrap:
 109          cmp ax, [_rxOutOfs]
 110          je  @dump
 111          mov di, [_rxInOfs]          ; ES:DI -> _pktRxBuf[n]
 112          mov [newInOffset], ax
 113
 114          mov [di], cx                ; remember firstCount.
 115          mov [di+4], bx              ; remember handle.
 116          add di, 6                   ; ES:DI -> _pktRxBuf[n].destinAdr
 117          pop ds
 118          popf
 119          retf                        ; far return to driver with ES:DI
 120
 121 @dump:   add word [_pktDrop+0], 1    ; discard the packet on 1st call
 122          adc word [_pktDrop+2], 0    ; increment packets lost
 123
 124 @skip:   xor di, di                  ; return ES:DI = NIL pointer
 125          xor ax, ax
 126          mov es, ax
 127          pop ds
 128          popf
 129          retf
 130
 131 @post:   or si, si                   ; DS:SI->_pktRxBuf[n][n].destinAdr
 132          jz @discard                 ; make sure we don't use NULL-pointer
 133
 134        ;
 135        ; push si
 136        ; call bpf_filter_match       ; run the filter here some day
 137        ; pop si
 138        ; cmp ax, 0
 139        ; je  @discard
 140
 141          mov [si-6+2], cx            ; store _pktRxBuf[n].secondCount
 142          mov ax, [newInOffset]
 143          mov [_rxInOfs], ax          ; update _pktRxBuf input offset
 144
 145        ; call PutTimeStamp
 146
 147 @discard:
 148          pop ds
 149          popf
 150          retf
 151
 152 _pktRxEnd  db 0                      ; marker for end of r-mode code/data
 153
 154 END
 155