The Tcpdump Group git mirrors - libpcap/blob - msdos/pkt_rx0.asm

   1 PAGE 60,132
   2 NAME PKT_RX
   3
   4 ifdef ??version        ; using TASM
   5   masm
   6   jumps
   7 endif
   8
   9 PUBLIC _pktDrop, _pktRxBuf, _pktTxBuf,    _pktTemp
  10 PUBLIC _rxOutOfs, _rxInOfs, _PktReceiver, _pktRxEnd
  11
  12 ;
  13 ; these sizes MUST be equal to the sizes in PKTDRVR.H
  14 ;
  15
  16 RX_BUF_SIZE = 1500      ; max message size on Ethernet
  17 TX_BUF_SIZE = 1500
  18
  19 ifdef DOSX
  20  .386
  21   NUM_RX_BUF = 32       ; # of RX element buffers
  22   _TEXT   SEGMENT PUBLIC DWORD USE16 'CODE'
  23   _TEXT   ENDS
  24   _DATA   SEGMENT PUBLIC DWORD USE16 'CODE'
  25   _DATA   ENDS
  26   D_SEG   EQU <_TEXT SEGMENT>
  27   D_END   EQU <_TEXT ENDS>
  28   ASSUME  CS:_TEXT,DS:_TEXT
  29 else
  30  .286
  31   NUM_RX_BUF = 10
  32   _TEXT   SEGMENT PUBLIC DWORD 'CODE'
  33   _TEXT   ENDS
  34   _DATA   SEGMENT PUBLIC DWORD 'DATA'
  35   _DATA   ENDS
  36   D_SEG   EQU <_DATA SEGMENT>
  37   D_END   EQU <_DATA ENDS>
  38   ASSUME  CS:_TEXT,DS:_DATA
  39 endif
  40
  41 ;-------------------------------------------
  42
  43 D_SEG
  44
  45 RX_ELEMENT     STRUC
  46    firstCount  dw  0                          ; # of bytes on 1st call
  47    secondCount dw  0                          ; # of bytes on 2nd call
  48    handle      dw  0                          ; handle for upcall
  49    destinAdr   db  6           dup (0)        ; packet destination address
  50    sourceAdr   db  6           dup (0)        ; packet source address
  51    protocol    dw  0                          ; packet protocol number
  52    rxBuffer    db  RX_BUF_SIZE dup (0)        ; RX buffer
  53 ENDS
  54                align 4
  55 _rxOutOfs      dw  offset _pktRxBuf           ; ring buffer offsets
  56 _rxInOfs       dw  offset _pktRxBuf           ; into _pktRxBuf
  57 _pktDrop       dw  0,0                        ; packet drop counter
  58 _pktTemp       db  20                dup (0)  ; temp work area
  59 _pktTxBuf      db  (TX_BUF_SIZE+14)  dup (0)  ; TX buffer
  60 _pktRxBuf      RX_ELEMENT NUM_RX_BUF dup (<>) ; RX structures
  61  LAST_OFS      = offset $
  62
  63  screenSeg     dw  0B800h
  64  newInOffset   dw  0
  65
  66  fanChars      db  '-\|/'
  67  fanIndex      dw  0
  68
  69 D_END
  70
  71 _TEXT SEGMENT
  72
  73
  74 SHOW_RX  MACRO
  75          push es
  76          push bx
  77          mov bx, screenSeg
  78          mov es, bx                    ;; r-mode segment of colour screen
  79          mov di, 158                   ;; upper right corner - 1
  80          mov bx, fanIndex
  81          mov al, fanChars[bx]          ;; get write char
  82          mov ah, 15                    ;;  and white colour
  83          stosw                         ;; write to screen at ES:EDI
  84          inc fanIndex                  ;; update next index
  85          and fanIndex, 3
  86          pop bx
  87          pop es
  88 ENDM
  89
  90 ;------------------------------------------------------------------------
  91 ;
  92 ; This macro return ES:DI to tail of Rx queue
  93
  94 ENQUEUE  MACRO
  95          LOCAL @noWrap
  96          mov ax, _rxInOfs              ;; DI = current in-offset
  97          add ax, SIZE RX_ELEMENT       ;; point to next _pktRxBuf buffer
  98          cmp ax, LAST_OFS              ;; pointing past last ?
  99          jb  @noWrap                   ;; no - jump
 100          lea ax, _pktRxBuf             ;; yes, point to 1st buffer
 101          align 4
 102 @noWrap: cmp ax, _rxOutOfs             ;; in-ofs = out-ofs ?
 103          je  @dump                     ;; yes, queue is full
 104          mov di, _rxInOfs              ;; ES:DI -> buffer at queue input
 105          mov newInOffset, ax           ;; remember new input offset
 106
 107    ;; NOTE. rxInOfs is updated after the packet has been copied
 108    ;; to ES:DI (= DS:SI on 2nd call) by the packet driver
 109
 110 ENDM
 111
 112 ;------------------------------------------------------------------------
 113 ;
 114 ; This routine gets called by the packet driver twice:
 115 ;   1st time (AX=0) it requests an address where to put the packet
 116 ;
 117 ;   2nd time (AX=1) the packet has been copied to this location (DS:SI)
 118 ;   BX has client handle (stored in RX_ELEMENT.handle).
 119 ;   CX has # of bytes in packet on both call. They should be equal.
 120 ;
 121 ; A test for equality is done by putting CX in _pktRxBuf [n].firstCount
 122 ; and _pktRxBuf[n].secondCount, and CL on first call in
 123 ; _pktRxBuf[n].rxBuffer[CX]. These values are checked in "PktReceive"
 124 ; (PKTDRVR.C)
 125 ;
 126 ;---------------------------------------------------------------------
 127
 128 _PktReceiver:
 129          pushf
 130          cli                         ; no distraction wanted !
 131          push ds
 132          push bx
 133 ifdef DOSX
 134          mov bx, cs
 135 else
 136          mov bx, SEG _DATA
 137 endif
 138          mov ds, bx
 139          mov es, bx                  ; ES = DS = CS or seg _DATA
 140          pop bx                      ; restore handle
 141
 142          cmp ax, 0                   ; first call? (AX=0)
 143          jne @post                   ; AX=1: second call, do post process
 144
 145 ifdef DEBUG
 146          SHOW_RX                     ; show that a packet is received
 147 endif
 148          cmp cx, RX_BUF_SIZE+14      ; size OK ?
 149          ja  @skip                   ; no, packet to large for us
 150
 151          ENQUEUE                     ; ES:DI -> _pktRxBuf[n]
 152
 153          mov [di].firstCount, cx     ; remember the first count.
 154          mov [di].handle, bx         ; remember the handle.
 155          add di, 6                   ; ES:DI -> _pktRxBuf[n].destinAdr
 156          pop ds
 157          popf
 158          retf                        ; far return to driver with ES:DI
 159
 160          align 4
 161 @dump:   inc _pktDrop[0]             ; discard the packet on 1st call
 162          adc _pktDrop[2], 0          ; increment packets lost
 163
 164 @skip:   xor di, di                  ; return ES:DI = NIL pointer
 165          xor ax, ax
 166          mov es, ax
 167          pop ds
 168          popf
 169          retf
 170
 171          align 4
 172 @post:   or si, si                   ; DS:SI->_pktRxBuf[n][n].destinAdr
 173          jz @discard                 ; make sure we don't use NULL-pointer
 174
 175          sub si, 6                   ; DS:SI -> _pktRxBuf[n].destinAdr
 176        ;
 177        ; push si
 178        ; push [si].firstCount
 179        ; call bpf_filter_match       ; run the filter here some day?
 180        ; add sp, 4
 181        ; cmp ax, 0
 182        ; je  @discard
 183
 184          mov [si].secondCount, cx
 185          mov ax, newInOffset
 186          mov _rxInOfs, ax            ; update _pktRxBuf input offset
 187
 188          align 4
 189 @discard:pop ds
 190          popf
 191          retf
 192
 193 _pktRxEnd  db 0                      ; marker for end of r-mode code/data
 194
 195 _TEXT ENDS
 196
 197 END