Media Share 9/MEDIASHARE_09.ISO/network/pcb121.zip/BRIDGE.INC

Text File | 1992-01-23 | 11KB | 329 lines

;;******************************************************************************
;;                         bridge.inc      bridge.inc
;;******************************************************************************
;;
;;  Copyright (C) 1989 Northwestern University, Vance Morrison
;;
;;
;; Permission to view, compile, and modify for LOCAL (intra-organization)
;; USE ONLY is hereby granted, provided that this copyright and permission
;; notice appear on all copies.  Any other use by permission only.
;;
;; Northwestern University makes no representations about the suitability
;; of this software for any purpose.  It is provided "as is" without expressed
;; or implied warranty.  See the copywrite notice file for complete details.
;;
;;******************************************************************************
;;
;; Bridge.inc provides ethernet bridge cababilities.  Bridge will do bridging
;; between the interfaces provided to it.  It will also act like a IF object
;; and return packets that are directed to any of its interfaces.
;;
;; The functions provided by this file are
;;
;;   BDG_DECLARE name, start_ifs, end_ifs, forward_ip
;;   BDG_DEFINE name
;;   BDG_IF_R_ACCESS_out_BX_CX_ES name, no_packet
;;   BDG_IF_R_CONT_in_BX_CX_ES_const_BX_CX_DX_BP_SI_DI_ES name, ok
;;   BDG_IF_R_FREE_const_BX_CX_BP_SI_DI_ES name
;;   BDG_IF_W_ACCESS_in_CX_out_DI_ES_const_BX_CX_BP name, no_buffer
;;   BDG_IF_W_WRITE_in_CX_const_BX_BP_ES name
;;   BDG_IF_SET_ADDRESS_in_SI_const_BX_CX_BP_DI_ES name
;;   BDG_IF_COPY_in_CX_SI_DI_ES_out_SI_DI_const_BX_BP_ES name
;;
;; Variables set by this module
;;
;;   bdg_&name&_declared                       ;; one if this interface exists
;;   if_&name&_address                         ;; the hardware address
;;   if_&name&_mtu                             ;; the maximum trans unit
;;
;;******************************************************************************


;;******************************************************************************
;;   BDG_DECLARE name, start_ifs, end_ifs, forward_ip
;;      BDG_DECLARE declares a bridge made up of the ifs [start_ifs..end_ifs].
;;  All of these ifs are assumed to be declared to be PROMISCUOUS and
;;  if 'forward_ip' is not blank, then IP broadcasts and ARPS will be
;;      forwarded, otherwize they will not
;;
BDG_DECLARE MACRO name, start_ifs, end_ifs, forward_ip
    .errb <name>
    .errb <start_ifs>
    .errb <end_ifs>

    if name ne 1
        .err                ;; you are only alowed 1 bridge and it must be
                            ;; named '1'
    endif

    .DATA
    bdg_&name&_declared  = 1
    bdg_&name&_start_ifs = start_ifs
    bdg_&name&_end_ifs = end_ifs
    global bdg_&name&_table_ptr:word        ;; holds segement for table

    bdg_&name&_forw_ip   = 0&forward_ip
    .CODE
ENDM


;;******************************************************************************
;;   BDG_DEFINE name
;;      sets asside memory for the bridge and initializes it.
;;      routine is a no-op if 'name' was not declared
;;
BDG_DEFINE MACRO name
    LOCAL loop1, loop2, loop3, table
    .errb <name>

ifdef bdg_&name&_declared
    .data
    bdg_&name&_table_ptr dw ?                   ;; holds segment address of tab
    .FarData?
    table db 65535 dup (?)                      ;; set aside a whole segment
                                                ;; for the bridge table

    .CODE
    mov AX, SEG table
    mov bdg_&name&_table_ptr, AX                ;; remember where the table is

    mov ES, AX
    xor DI, DI
    mov CX, 32768
    xor AX, AX
    rep
    stosw                                       ;; null the bridge table

endif
ENDM


;;******************************************************************************
;;   IF_R_ACCESS_out_BX_ES name, no_packet
;;       IF_R_ACCESS waits for the next packet to come from the the board
;;       associated with 'name' and returns a pointer to the begining of
;;       an ethernet packet in BX:ES.  CX holds the length of the packet
;;       R_ACCESS jumps to 'no_packet' if there are no packets waiting to
;;       be read in
;;
BDG_IF_R_ACCESS_out_BX_CX_ES MACRO name, no_packet
    local got_packet, forward_all, forward, not_me, drop
    local broadcast, broadcast_drop, around
    .errb <no_packet>

    IF_R_ACCESS_out_BX_CX_ES name, no_packet

    mov AX, ES:[BX+4]       ;; is this my ethernet address?
    cmp AX, word ptr if_&name&_address+4
    jnz not_me
    mov AX, ES:[BX+2]
    cmp AX, word ptr if_&name&_address+2
    jnz not_me
    mov AX, ES:[BX]
    cmp AX, word ptr if_&name&_address
    jz got_packet
    not_me:

    if bdg_1_forw_ip eq 0       ;; drop because it is an IP or ARP packet?
        mov AX, word ptr ES:[BX+12]
        cmp AX, 0008H           ;; is it an IP packet
        jz drop
        cmp AX, 0608H           ;; is it an ARP packet
        jz drop
    endif

    mov BP, DS                  ;; save DS
    mov SI, BX

    mov AX, ES
    mov ES, bdg_1_table_ptr     ;; ES:0 points to the table
    mov DS, AX                  ;; DS:SI points to the packet

    add SI, 6                   ;; skip to source address of the packet

    mov DI, [SI+4]              ;; compute hash function ((LSB+MSB) * 8 mod 65k)
    xor DI, [SI+2]
    shl DI, 1
    shl DI, 1
    shl DI, 1
    movsw                       ;; save the ethernet address
    movsw
    movsw
    mov AL, name            ;; and the fact that it is on this interface
    stosb

    sub SI, 12                  ;; restore SI to the begining of the packet

    test byte ptr [SI], 1H      ;; is it a broadcast

    jnz broadcast

    mov DI, [SI+4]              ;; compute hash function ((LSB+MSB) * 8 mod 65k)
    xor DI, [SI+2]
    shl DI, 1
    shl DI, 1
    shl DI, 1

    cmpsw
    jnz forward_all         ;; didn't find in table
    cmpsw
    jnz forward_all         ;; didn't find in table
    cmpsw
    jnz forward_all         ;; didn't find in table
    mov DS, BP              ;; restore DS
    mov AL, ES:[DI]
    cmp AL, name
    jnz forward
        drop:
        IF_R_FREE_const_BX_CX_BP_SI_DI_ES name
        jmp no_packet

    forward:
        mov BP, CX
        IRP idx, <1,2,3,4,5,6,7,8>
        local next
        if (idx le bdg_1_end_ifs) and (idx ge bdg_1_start_ifs)
        if idx ne name
            cmp AL, idx
            jnz next
                IF_W_ACCESS_in_CX_out_DI_ES_const_BX_CX_BP idx, drop
                mov SI, BX
                IF_COPY_in_CX_SI_DI_ES_out_SI_DI_const_BX_BP_ES name
                mov CX, BP
                IF_W_WRITE_in_CX_const_BX_BP_ES idx
            next:
        endif
        endif
        endm
       jmp drop

    forward_all:
        mov DS, BP              ;; restore DS
        mov BP, CX
        IRP idx, <1,2,3,4,5,6,7,8>
        if (idx le bdg_1_end_ifs) and (idx ge bdg_1_start_ifs)
        if idx ne name
            mov CX, BP
            IF_W_ACCESS_in_CX_out_DI_ES_const_BX_CX_BP idx, drop
            mov SI, BX
            IF_COPY_in_CX_SI_DI_ES_out_SI_DI_const_BX_BP_ES name
            mov CX, BP
            IF_W_WRITE_in_CX_const_BX_BP_ES idx
        endif
        endif
        endm
       jmp drop

    broadcast:
    mov AX, DS                  ;; restore ES
    mov ES, AX
    mov DS, BP                  ;; restore DS

    ;; if we don't drop it, then we must send it to all the interfaces
    push ES
    mov BP, CX
    IRP idx, <1,2,3,4,5,6,7,8>
    if (idx le bdg_1_end_ifs) and (idx ge bdg_1_start_ifs)
    if idx ne name
        mov CX, BP
        IF_W_ACCESS_in_CX_out_DI_ES_const_BX_CX_BP idx, drop
        mov SI, BX
        IF_COPY_in_CX_SI_DI_ES_out_SI_DI_const_BX_BP_ES name
        mov CX, BP
        IF_W_WRITE_in_CX_const_BX_BP_ES idx
    endif
    endif
    endm
    pop ES

    broadcast_drop:
    ;; in either case, we also send the packet up to the higher level protocols
    mov CX, BP          ;; restore the length
    got_packet:
ENDM


;;******************************************************************************
;;   IF_R_FREE_const_BX_CX_BP_SI_DI_ES  name
;;       After the client is through processing the packet returned by
;;       IF_R_ACCESS, IF_R_FREE must be called to inform 'name' that the
;;       memory that the packet was in can be reused for future packets.
;;
BDG_IF_R_FREE_const_BX_CX_BP_SI_DI_ES MACRO name
    local inside
    .errb <name>

    IF_R_FREE_const_BX_CX_BP_SI_DI_ES name
ENDM


;;******************************************************************************
;;   BDG_IF_R_CONT_in_BX_CX_ES name, ok
;;       IF_R_CONT determines if the packet returned by R_ACCESS in BX:ES
;;       of length CX is continuous.  If it is it jumps to 'ok' otherwise
;;       it just returns
;;
BDG_IF_R_CONT_in_BX_CX_ES_const_BX_CX_DX_BP_SI_DI_ES MACRO name, ok
    .errb <ok>

    IF_R_CONT_in_BX_CX_ES_const_BX_CX_DX_BP_SI_DI_ES name, ok
ENDM


;;******************************************************************************
;;   IF_W_ACCESS_in_CX_out_DI_ES name, no_buffer
;;       IF_W_ACCESS returns a pointer to an output buffer for a packet.  The
;;       pointer is returned in DI:ES.  If the ouptut buffer is busy, this
;;       routine will jump to 'no_buffer'.  The output buffer  min(CX, 1536)
;;       bytes long
;;
BDG_IF_W_ACCESS_in_CX_out_DI_ES_const_BX_CX_BP MACRO name, no_buffer
    .errb <no_buffer>

    IF_W_ACCESS_in_CX_out_DI_ES_const_BX_CX_BP name,no_buffer
ENDM


;;******************************************************************************
;;   IF_W_WRITE_in_CX name
;;       IF_W_WRITE actually signals the ethernet board to write a packet to
;;       the ethernet.  The packet is assumed to be in the buffer returned by
;;       IF_W_ACCESS. CX is the length of the packet to send.
;;
BDG_IF_W_WRITE_in_CX_const_BX_BP_ES MACRO name
    .errb <name>

    IF_W_WRITE_in_CX_const_BX_BP_ES name
ENDM


;;******************************************************************************
;;   IF_SET_ADDRESS_in_SI name
;;       IF_SET_ADDRESS_in_SI sets the hardware address to be the value
;;       pointed to by SI.  Note this function may be a no-op if the
;;       hardware address cannot be set (ETHERNET for example)
;;
BDG_IF_SET_ADDRESS_in_SI_const_BX_CX_BP_DI_ES MACRO name
    .errb <name>

    IF_SET_ADDRESS_in_SI_const_BX_CX_BP_DI_ES name
ENDM


;;******************************************************************************
;;   IF_COPY_in_CX_SI_DI_ES name
;;      IF_COPY_in_CX_SI_DI_ES copys a packet from the input buffer (pointed
;;      to by SI and the segement register given in IF_DECLARE) to an output
;;      buffer (pointed to by DI and dest_reg) of length CX.   It assumes the
;;      output buffer is contiguous.  (and the caller shouln't care if the
;;      input buffer is contiguous)
;;
BDG_IF_COPY_in_CX_SI_DI_ES_out_SI_DI_const_BX_BP_ES MACRO name
    local wrap, done
    .errb <name>

    IF_COPY_in_CX_SI_DI_ES_out_SI_DI_const_BX_BP_ES name
ENDM