ProfitPress Mega CDROM2 Shareware Freeware (MSDOS)(1992)(Eng)

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Assembly Source File | 1992-05-17 | 15.2 KB | 653 lines

; arp.asm ;======================================================================== ; Copyright (C) 1991 by Jan.Engvald@ldc.lu.se, see file COPYING. ArpStruc struc iArpHtype dw 0 ; 0001 = Ether iArpProt dw 0008h ; 0800 = IP iArpHlen db 0 ; Hw addr length iArpPlen db 4 ; IP addr length iArpOp dw 0100h ; 0001 = request iArpMyHwAd db 2*16+2*4 dup (0) ArpBodyLen = $-iArpHtype ArpStruc ends ArpBegLen equ iArpMyHwAd+8-iArpHtype ArpHandle dw 0 ifndef ARPSLOTS ARPSLOTS equ 12 endif ; The arp table contains information on hosts on this net. ; Slot 0, 1 and 2 (index 0, 2 and 4) are static and contain: ; this net broadcast, this subnet broadcast and my address, respectively. ; ; If we don't RECEIVE packets for more than a minute from a host or gateway, ; its slot is cleared. If we then DO receive a packet, the slot is restored ; by VerifyIpHdr without sending an ARP. On the other hand, if WE want to ; send the next packet, we will do an ARP and can thus detect dead hosts ; or gateways. even ArpTabIp2 dw ARPSLOTS dup (0ffffh) ; IP # (last part) ArpTabIp1 dw ARPSLOTS dup (0ffffh) ; IP # (first part) ArpTabTr dw ARPSLOTS dup (0) ; timer ArpTabFlags dw ARPSLOTS dup (0) ; flags ArpTabTrSq dw ARPSLOTS dup (0) ; source quench timer ArpTabSqDelay dw ARPSLOTS dup (0) ; source quench delay ArpTabHwAdr db ARPSLOTS*16 dup (0ffh) ; hardware addr (max 16 bytes) ArpTabHw3 dw ARPSLOTS dup (0ffffh) ; hw addr for reverse lookup ArpTabHw2 dw ARPSLOTS dup (0ffffh) ; hw addr for reverse lookup ArpTabHw1 dw ARPSLOTS dup (0ffffh) ; hw addr for reverse lookup USE_SNAP equ 1 ; bit in ArpTabFlags SQ_UPDATED equ 2 ; bit in ArptabFlags/RouteTabFl ARPMYIDX equ 4 ArpPutSlot dw ARPMYIDX ArpType dw 0608h ArpBuf ArpStruc <> ArpFixedLen equ $-ArpType aArpOffsSrcIp equ iArpMyHwAd+2-iArpHtype ; *test* MyHwAd equ ArpBuf.iArpMyHwAd ProtType equ ArpBuf.iArpProt ArpFixedPart equ ArpType if DEBUG DbgIntCnt db 1 endif ; DEBUG ;************************************************************************ ;* ArpFindIp ;* ;* Input: DX = first word of IP # (saved) ;* AX = second word of IP # (saved) ;* A PushfDI must be done before calling ;* Output: if found: zero and DI = arp table index ;* Destroys: CX, DI, ES, flags ;************************************************************************ ArpFindIp proc near mov di,offset ArpTabIp2 mov cx,ARPSLOTS ArpFindIpNext: ; look for matching slot repne scasw jnz ArpFindIpRet cmp dx,2*ARPSLOTS-2[di] ; does IP # first part match? jne ArpFindIpNext ; - no, look further sub di,offset ArpTabIp2+2 ; - yes, compute slot index cmp di,di ; set zero flag ArpFindIpRet: ret ArpFindIp endp ;************************************************************************ ;* ArpFindHw ;* ;* Input: SI = first word of HW addr (saved) ;* DX = second word of HW addr (saved) ;* AX = third word of HW addr (saved) ;* A PushfDI must be done before calling ;* Output: if found: zero and DI = arp table index ;* Destroys: CX, DI, ES, flags ;************************************************************************ ArpFindHw proc near mov di,offset ArpTabHw3 mov cx,ARPSLOTS ArpFindHwNext: ; look for matching slot repne scasw jnz ArpFindHwRet cmp dx,2*ARPSLOTS-2[di] ; does HW second part match? jne ArpFindHwNext ; - no, look further cmp si,4*ARPSLOTS-2[di] ; does HW first part match? jne ArpFindHwNext ; - no, look further sub di,offset ArpTabHw3+2 ; - yes, compute slot index cmp di,di ; set zero flag ArpFindHwRet: ret ; zero (found) return ArpFindHw endp ;************************************************************************ ;* ArpPutHwAd ;* ;* Input: SI = pointer to physical address (saved) ;* DI = arp table index ;* A PushfDI must be done before calling ;* Destroys: CX, DI, flags ;************************************************************************ ArpPutHwAd proc near push si mov cx,[si] ; put reverse search mov ArpTabHw1[di],cx ; hw addr into slot mov cx,[si+2] mov ArpTabHw2[di],cx mov cx,[si+4] mov ArpTabHw3[di],cx call CurrentTicks ; get current ticks value mov ArpTabTr[di],cx mov cx,ArpTabFlags[di] and cl,not USE_SNAP or cl,[bx].dSnap ; remember if snaps used mov ArpTabFlags[di],cx ; by that host mov cl,3 ; put hw addr into slot shl di,cl lea di,ArpTabHwAdr[di] mov cx,Hlen push cs pop es rep movsb pop si ret ArpPutHwAd endp ;************************************************************************ ;* ArpPutHwDst ;* ;* Input: DX = first word of IP # (saved) ;* AX = second word of IP # (saved) ;* Output: if found: zero, HW dst addr copied to pkt and CX = 0 ;* Destroys: CX, SI, DI, ES, flags ;************************************************************************ ArpPutHwDst proc near PushfDI call ArpFindIp ; IP # in arp table? jnz ArpPutHwRet ; - no, non-zero (not found) mov cx,ArpTabFlags[di] ; use snap if neeeded and cl,USE_SNAP mov [bx].dSnap,cl ; by dst host if RFCC push ax call CurrentTicks mov ax,ArpTabSqDelay[di] ; move sq delay to descriptor mov [bx].dSqDelay,ax dec ax ; any delay? js ArpNoSqDelay mov ax,ArpTabTrSq[di] ; - yes add ax,18 ; has one second has passed cmp ax,cx ; since we last decremented jns ArpNoSqDelay ; the delay value? mov ArpTabTrSq[di],cx dec ArpTabSqDelay[di] ; - yes, one millisecond off ArpNoSqDelay: pop ax endif ; RFCC mov cl,3 ; - yes, copy HW addr shl di,cl lea si,ArpTabHwAdr[di] mov di,[bx].dPtrPhys mov cx,Hlen push cs pop es rep movsb PopfEI cmp di,di ; zero (found) return ret ArpPutHwRet: PopfEI dec cx ; non-zero return ret ArpPutHwDst endp ;************************************************************************ ;* ArpPutNew ;* ;* Input: DX = first word of IP # (saved) ;* AX = second word of IP # (saved) ;* SI = pointer to physical address (saved) ;* Destroys: CX, DI, ES, flags ;************************************************************************ ArpPutNew proc near PushfDI call ArpFindIp ; already have IP # ? jz ArpPutHere ; - yes, update hw addr ArpPutWrap: ; - no, find next slot mov di,ArpPutSlot add di,2 ; advance index two bytes cmp di,2*ARPSLOTS ; end of arp table? jb ArpPut mov di,ARPMYIDX+2 ; preserve bcast mappings ArpPut: ; (first slots) if TBLBUILD push si mov si,di add si,2 cmp si,2*ARPSLOTS jb ArpPut2 mov si,ARPMYIDX+2 ArpPut2: mov cx,ArpTabTr[di] sub cx,ArpTabTr[si] js ArpPut3 mov di,si ; use elder of next 2 slots ArpPut3: pop si endif ; TBLBUILD mov ArpPutSlot,di mov ArpTabIp1[di],dx ; put IP # into slot mov ArpTabIp2[di],ax xor cx,cx ; clear other fileds mov ArpTabFlags[di],cx mov ArpTabSqDelay[di],cx ArpPutHere: call ArpPutHwAd ; put HW addr into slot PopfEI ret ArpPutNew endp ;************************************************************************ ;* SendArpReq ;* ;* Input: DX = first word of IP # (saved) ;* AX = second word of IP # (saved) ;* BX = IP description buffer ptr (saved) ;* Output: Zero and CX = 0 if OK ;* non-zero and CX = errorcode if error ;* Destroys: CX, SI, DI, ES, flags ;************************************************************************ SendArpReq proc near push dx ; dx,ax has IP # to arp for push ax push bx ; save IP descr addr call BufAlloc ; get a buffer mov cx,SERRNOBUF jz SendArpRet mov si,offset ArpTabHwAdr ; put Ether broadcast dst mov cx,Hlen push cs pop es rep movsb call MakeSendDescr ; set up descriptor call PutPhysSrc ; put Ether src addr push di mov si,offset ArpFixedPart ; copy in static arp part mov cx,ArpFixedLen-2*16 ; *test* add cx,H2len push cs pop es rep movsb sub di,[bx].dPtrPhys ; calculate packet length mov [bx].dPktLen,di pop di ; compute addr to dst IP # add di,aArpOffsSrcIp add di,H2Len mov [di+4],dx ; IP # to arp for mov [di+4+2],ax sub di,Hlen ; fill in My IP # mov dx,MyIpNr mov ax,MyIpNr+2 mov [di],dx mov [di+2],ax pop si ; IP descr addr push si mov cx,[si].dTimOutMsg ; use application timeout msg mov [bx].dTimOutMsg,cx mov cx,[si].dTickTimeout cmp cx,3*18 ; limit arp timeout jbe SendArpOkTim mov cx,3*18 ; to 3 seconds or less SendArpOkTim: mov [bx].dTickTimeout,cx mov [bx].dWaitEvent,GOT_ARPREPLY call SendAndWait ; send arp request packet call BufRelease ; release buffer SendArpRet: or cx,cx pop bx ; restore IP descr addr pop ax ; restore IP # we ARPed for pop dx ret SendArpReq endp ;************************************************************************ ;* InitArp ;************************************************************************ InitArp proc near push ds mov ax,1ffh ; driver_info int_pkt pop ds call fatal_error mov ah,2 ; access all packets. mov al,ch ; their class from driver_info(). mov byte ptr ArpBuf.iArpHtype+1,al mov bx,dx ; their type from driver_info(). mov dl,cl ;their number from driver_info(). mov cx,2 ;type length of two. mov si,offset ArpType push cs ;es:di -> our receiver. pop es mov di,offset ArpRecv push ds int_pkt pop ds call fatal_error mov ArpHandle,ax mov bx,ax push cs pop es mov di,offset MyHwAd mov cx,15 mov ah,6 ; get my Hw addr push ds int_pkt pop ds call fatal_error mov ArpBuf.iArpHlen,cl ; save Hw address length mov Hlen,cx shl cx,1 mov H2Len,cx ret InitArp endp ;************************************************************************ ;* BuildRecDescr ;************************************************************************ BuildRecDescr proc near mov bx,si mov ax,si add ax,cx ; end of packet limit sub bx,2 mov bx,[bx] ; addr of descriptor mov [bx].dPktLen,cx ; fill in descriptor info mov [bx].dPktEnd,ax add si,H2Len mov ax,[si] ; type/length field xchg ah,al xor dl,dl cmp ax,GIANT ; if 802.3 pkt jbe BuildHpOrSnap ; do special handling BuildNotSnap: mov [bx].dSnap,dl lea di,[si+2] mov [bx].dPtrIp,di ; di must point to IP hdr ret BuildHpOrSnap: BuildSnap: inc dl ; -no, assumed to be snap add si,SNAPLEN ; skip over snap bytes jmp short BuildNotSnap BuildRecDescr endp ;************************************************************************ ;* ARP receiver * ;************************************************************************ ArpRecv: pushf ; set segment registers push ds mov dx,cs mov ds,dx mov es,dx cld or ax,ax ; first or second call? jne ArpRecv_1 ; - second, we've got data ; - first, they want a buf cmp cx,GIANT ; packet too long? ja ArpRecTooBig if PINGCLIENT cmp cx,BUFBODYSML ja ArpRecBig call BufAlSml jz ArpRecBig pop ds popf retf ArpRecBig: endif ; PINGCLIENT call BufAlloc ; get a receive buffer jz ArpRecNoBuf ArpRecRet0: pop ds popf retf if DEBUG DbgArpRecv: or GenFlags,DBGINTERR endif ; DEBUG ArpRecNoBuf: ArpRecTooBig: xor di,di ; no buffer available mov es,di jmp short ArpRecRet0 ArpRecv_1: cli ; switch to our mov word ptr SaveSP,sp ; interrupt stack mov word ptr SaveSS,ss mov sp,offset StackEnd mov ss,MySegm sti ; enable interrupts if DEBUG dec DbgIntCnt ; double interrupt? jnz DbgArpRecv endif ; DEBUG call BuildRecDescr cmp [di].iArpProt,0008h ; arp IP protocol? jne ArpRecRet push di mov di,[bx].dPtrPhys add di,Hlen mov si,[di] mov dx,[di+2] mov ax,[di+4] call ArpFindHw pop si jnz ArpRecNew cmp di,ARPMYIDX ; ignore pkts from bcast or me jbe ArpRecRet ; (also helps NDIS) ArpRecNew: lea di,[si].iArpMyHwAd mov cx,[si].iArpOp ; ARP reply? mov si,di add di,Hlen mov dx,word ptr [di] ; get HIS (!) IP # and keep mov ax,word ptr [di+2] ; it for a long while add di,4 cmp di,[bx].dPktEnd ; big enough to be arp pkt? ja ArpRecRet ; The following test is not according to the ARP RFC. The reason for this ; divergence is that if we follow the RFC algorithm, anybody that momentarily ; uses a wrong IP number would disrupt our communication with the original ; owner of that IP number. This would be true even if the program he uses ; is nice (NCSA Telnet for example) and starts by sending an ARP packet for ; itself to see if anybody will answer (a very good thing to do and this ; package does so too). ; ; We do obey an unsolicited arp reply immediately, other cases of changed ; hardware address will be taken care of in a minute automagically by the ; arp table ageing mechanism, so this package should do well even when moving ; hosts in a proxy arp environment. cmp cx,0200h ; ARP reply? jne ArpNotReply PushfDI call ArpFindIp ; if he is in our ARP table we jnz ArpNotThere call ArpPutHwAd ; should update his HW addr ArpNotThere: PopfEI ArpNotReply: mov di,si add di,H2Len mov cx,[di+4] cmp cx,MyIpNr ; is this arp for me? jne ArpRecTbl mov cx,[di+6] cmp cx,MyIpNr+2 jne ArpRecTbl add di,8 cmp di,[bx].dPktEnd ja ArpRecRet call ArpPutNew ; - yes, put his IP # and HW ; addr into the ARP table mov di,[bx].dPtrIp cmp [di].iArpOp,0100h ; arp request? je ArpRecReq or Events,GOT_ARPREPLY ; - no, probably a wanted reply ArpRecTbl: if TBLBUILD test ArgFlags,MAKE_TABLE jnz ArpRecBld endif ; TBLBUILD ArpRecRet: call BufRelease ; release receive buffer ArpRecKeepBuf: if DEBUG inc DbgIntCnt endif ; DEBUG cli ; restore previous stack mov sp, word ptr SaveSP mov ss, word ptr SaveSS pop ds popf retf if TBLBUILD ArpRecBld: cmp FreeBufs.lBufsAvail,NBUFS/4 jbe ArpRecRet test GenFlags,TBL_READY jz ArpRecRet mov si,offset TblToDo call AddToList jmp short ArpRecKeepBuf endif ; TBLBUILD ArpRecReq: mov [di].iArpOp,0200h ; put arp reply code mov di,si push di mov cx,Hlen add cx,4 add di,cx push cs pop es rep movsb ; mov arp dst to arp src pop di mov si,offset MyHwAd mov cx,Hlen rep movsb ; put in my HW addr as arp src mov cx,MyIpNr mov [di],cx ; put my IP # to arp src mov si,MyIpNr+2 mov [di+2],si cmp dx,cx ; is he stealing my IP # ? jne ArpRecNoSteal cmp ax,si jne ArpRecNoSteal mov dx,ArpTabIp1 ; - yes, tell everybody by mov ax,dx ; broadcasting my reply ArpRecNoSteal: mov [bx].dWaitEvent,0 call ArpPutHwDst ; put dst Ether addr fr DX,AX call PutPhysSrc ; put src Ether addr mov word ptr [di],0608h ; arp prot mov si,offset SendToDo ; put buffer on the send list call AddToList ; for non-interrupt handling jmp short ArpRecKeepBuf ;======================================================================== ; endinclude