Subversion Repositories Kolibri OS

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;;                                                                 ;;

;; Copyright (C) KolibriOS team 2004-2009. All rights reserved.    ;;

;; Distributed under terms of the GNU General Public License       ;;

;;                                                                 ;;

;;  IPv4.INC                                                       ;;

;;                                                                 ;;

;;  Part of the tcp/ip network stack for KolibriOS                 ;;

;;                                                                 ;;

;;  Based on the work of [Johnny_B] and [smb]                      ;;

;;                                                                 ;;

;;    Written by hidnplayr@kolibrios.org                           ;;

;;                                                                 ;;

;;          GNU GENERAL PUBLIC LICENSE                             ;;

;;             Version 2, June 1991                                ;;

;;                                                                 ;;

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

$Revision: 1254 $

; IP underlying protocols numbers

ETHER_IPv4	equ 0x0008	; Reversed from 0800 for intel

MAX_FRAGMENTS	equ 16

MAX_IP		equ MAX_NET_DEVICES

struct	IPv4_Packet

	.VersionAndIHL		db  ?  ; Version[0-3 bits] and IHL(header length)[4-7 bits]

	.TypeOfService		db  ?

	.TotalLength		dw  ?

	.Identification 	dw  ?

	.FlagsAndFragmentOffset dw  ?  ; Flags[0-2] and FragmentOffset[3-15]

	.TimeToLive		db  ?  ;

	.Protocol		db  ?

	.HeaderChecksum 	dw  ?

	.SourceAddress		dd  ?

	.DestinationAddress	dd  ?

	.DataOrOptional:

ends

struct	FRAGMENT_slot

	.ttl			dw  ?  ; Time to live for this entry, 0 for empty slot's

	.id			dw  ?  ; Identification field from IP header

	.SrcIP			dd  ?  ; .. from IP header

	.DstIP			dd  ?  ; .. from IP header

	.ptr			dd  ?  ; Pointer to first packet

	.size:

ends

struct	FRAGMENT_entry		       ; This structure will replace the ethernet header in fragmented ip packets

	.PrevPtr		dd  ?  ; Pointer to previous fragment entry  (-1 for first packet)

	.NextPtr		dd  ?  ; Pointer to next fragment entry (-1 for last packet)

	.Owner			dd  ?  ; Pointer to structure of driver

				rb  2  ; to match ethernet header size          ; TODO: fix this hack

	.Data:			       ; Ip header begins here (we will need the IP header to re-construct the complete packet)

ends

align 4

uglobal

	BROADCAST	dd  ?

	IP_LIST 	rd  MAX_IP

	SUBNET_LIST	rd  MAX_IP

	DNS_LIST	rd  MAX_IP

	GATEWAY_LIST	rd  MAX_IP

	IP_PACKETS_TX	rd  MAX_IP

	IP_PACKETS_RX	rd  MAX_IP

	FRAGMENT_LIST	rb  MAX_FRAGMENTS*FRAGMENT_slot.size

endg

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

;

; IPv4_init

;

;  This function resets all IP variables

;

;  IN:  /

;  OUT: /

;

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

align 4

IPv4_init:

	or	eax, -1

	mov	edi, BROADCAST

	mov	ecx, 4*MAX_IP+1

	rep	stosd

	xor	eax, eax

	mov	edi, FRAGMENT_LIST

	mov	ecx, FRAGMENT_slot.size*MAX_FRAGMENTS/4 + 2*MAX_IP

	rep	stosd

	ret

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

;

; IPv4_Handler:

;

;  Will check if IP Packet isnt damaged

;  and call appropriate handler. (TCP/UDP/ICMP/..)

;

;  It will also re-construct fragmented packets

;

;  IN:  Pointer to buffer in [esp]

;       size of buffer in [esp+4]

;       pointer to device struct in ebx

;       pointer to IP Packet data in edx

;  OUT: /

;

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

align 4

IPv4_handler:

	DEBUGF	1,"IP_Handler - start\n"

	push	edx ebx

	; save checksum, and clear it in original packet

	mov	di , [edx + IPv4_Packet.HeaderChecksum]

	mov	word [edx + IPv4_Packet.HeaderChecksum], 0

	; Re-calculate checksum

	movzx	ecx, byte [edx + IPv4_Packet.VersionAndIHL]	; Calculate Header length by using IHL field

	and	ecx, 0x0000000F  ;

	shl	cx , 2		 ;

	mov	esi, edx

	xor	edx, edx

	call	checksum_1

	call	checksum_2

	; now compare the two..

	cmp	dx, di

	pop	ebx edx

	jne	.dump						; if checksum isn't valid then dump packet

	DEBUGF	1,"IPv4 Checksum is correct\n",di

	mov	eax, [edx + IPv4_Packet.DestinationAddress]

	mov	edi, BROADCAST

	mov	ecx, MAX_IP+1

	repnz	scasd

	jz	.ip_ok

	not	eax

	test	eax, 127 shl 24 ; 127.x.x.x

	jz	.ip_ok

;  TODO: we need to check for broadcasts (other then 255.255.255.255)

	jmp	.dump

  .ip_ok:

	call	ETH_struc2dev					; TODO: make this work on other protocols too!

	inc	[IP_PACKETS_RX+4*edi]

	DEBUGF	1,"packet comes from %u.%u.%u.%u\n",\

	[edx + IPv4_Packet.SourceAddress]:1,[edx + IPv4_Packet.SourceAddress + 1]:1,[edx + IPv4_Packet.SourceAddress + 2]:1,[edx + IPv4_Packet.SourceAddress + 3]:1

	mov	al , [edx + IPv4_Packet.VersionAndIHL]

	and	al , 0x0f					; get IHL(header length)

	cmp	al , 0x05					; IHL!= 5*4(20 bytes)

	jnz	.dump						; TODO: dont dump packets wich have optional fiels !!!                   /!\

	cmp	byte [edx + IPv4_Packet.TimeToLive], 0

	je	.dump

	movzx	eax, word [edx + IPv4_Packet.FlagsAndFragmentOffset]

	xchg	al , ah

	test	ax , 1 shl 13					; Is 'more fragments' flag set ?

	jnz	.yes_fragments					; If so, we definately have a fragmented packet

	test	ax , 0x1fff					; If flag is not set, but there is a fragment offset, the packet is last in series of fragmented packets

	jnz	.last_fragment

   .handle_it:							; We reach here if packet hasnt been fragmented, or when it already has been re-constructed

	movzx	eax, byte [edx + IPv4_Packet.VersionAndIHL]	; Calculate Header length by using IHL field

	and	eax, 0x0000000F 				;

	shl	eax, 2						;

	movzx	ecx, word [edx + IPv4_Packet.TotalLength]	; Calculate length of encapsulated Packet

	xchg	cl , ch 					;

	sub	ecx, eax					;

	add	eax, edx

	push	eax

	mov	al , [edx + IPv4_Packet.Protocol]

	mov	esi, [edx + IPv4_Packet.SourceAddress]

	mov	edi, [edx + IPv4_Packet.DestinationAddress]

	pop	edx						; Offset to data (tcp/udp/icmp/.. Packet)

	cmp	al , IP_PROTO_TCP

	je	TCP_handler

	cmp	al , IP_PROTO_UDP

	je	UDP_handler

	cmp	al , IP_PROTO_ICMP

	je	ICMP_handler

	DEBUGF	1,"unknown protocol: %u\n",al

  .dump:

	DEBUGF	1,"IP_Handler - done\n"

;        inc     [dumped_rx_count]

	call	kernel_free

	add	esp, 4						; pop (balance stack)

	ret

  .yes_fragments:

	shl	ax , 3

	DEBUGF	1,"Fragmented packet, offset:%u, id:%x\n", ax, [edx + IPv4_Packet.Identification]:4

	test	ax , ax 					; Is this the first packet of the fragment?

	jnz	.not_first_fragment

	DEBUGF	1,"First fragmented packet received!\n"

								; try to locate a free slot..

	mov	ecx, MAX_FRAGMENTS

	mov	esi, FRAGMENT_LIST

     .find_free_slot:

	cmp	word [esi + FRAGMENT_slot.ttl], 0

	je	.found_free_slot

	add	esi, FRAGMENT_slot.size

	loop	.find_free_slot

	jmp	.dump						; If no free slot was found, dump the packet

     .found_free_slot:						; We found a free slot, let's fill in the FRAGMENT_slot structure

	mov	word [esi + FRAGMENT_slot.ttl], 15		; RFC recommends 15 secs as ttl

	mov	ax , word [edx + IPv4_Packet.Identification]

	mov	word [esi + FRAGMENT_slot.id], ax

	mov	eax, dword [edx + IPv4_Packet.SourceAddress]

	mov	dword [esi + FRAGMENT_slot.SrcIP], eax

	mov	eax, dword [edx + IPv4_Packet.DestinationAddress]

	mov	dword [esi + FRAGMENT_slot.DstIP], eax

	pop	eax

	mov	dword [esi + FRAGMENT_slot.ptr], eax

								; Now, replace ethernet header in original buffer with a FRAGMENT_entry structure

	mov	[eax + FRAGMENT_entry.NextPtr], -1

	mov	[eax + FRAGMENT_entry.PrevPtr], -1

	mov	[eax + FRAGMENT_entry.Owner], ebx

	add	esp, 4						; balance stack and exit

	ret

  .not_first_fragment:

	DEBUGF	1,"Middle fragmented packet received!\n"

	call	.find_fragment_slot

	cmp	esi, -1

	je	.dump

	mov	word [esi + FRAGMENT_slot.ttl], 15		; Reset the ttl

	mov	esi, [esi + FRAGMENT_slot.ptr]

	or	edi, -1

     .find_last_entry:						; The following routine will try to find the last entry

	cmp	edi, [esi + FRAGMENT_entry.PrevPtr]

	jne	.destroy_slot					; Damn, something screwed up, remove the whole slot (and free buffers too if possible!)

	mov	edi, esi

	mov	esi, [esi + FRAGMENT_entry.NextPtr]

	cmp	esi, -1

	jne	.find_last_entry

								; We found the last entry (pointer is noww in edi)

								; We are going to overwrite the ethernet header in received packet with a FRAGMENT_entry structure

	pop	eax						; pointer to packet

	mov	[edi + FRAGMENT_entry.NextPtr], eax		; update pointer of previous entry to the new entry

	mov	[eax + FRAGMENT_entry.NextPtr], -1

	mov	[eax + FRAGMENT_entry.PrevPtr], edi

	mov	[eax + FRAGMENT_entry.Owner], ebx

	add	esp, 4

	ret

  .last_fragment:

	DEBUGF	1,"Last fragmented packet received!\n"

	call	.find_fragment_slot

	cmp	esi, -1

	je	.dump

	mov	esi, [esi + FRAGMENT_slot.ptr]			; We found the first entry, let's calculate total size of the packet in eax, so we can allocate a buffer

	push	esi

	xor	eax, eax					;

	or	edi, -1

     .count_bytes:

	cmp	[esi + FRAGMENT_entry.PrevPtr], edi

	jne	.destroy_slot_pop						; Damn, something screwed up, remove the whole slot (and free buffers too if possible!)

	mov	cx, word [esi + FRAGMENT_entry.Data + IPv4_Packet.TotalLength]	  ; Add total length

	xchg	cl, ch

	DEBUGF	1,"Packet size: %u\n", cx

	add	ax, cx

	movzx	cx, byte [esi + FRAGMENT_entry.Data + IPv4_Packet.VersionAndIHL]  ; Sub Header length

	and	cx, 0x000F

	shl	cx, 2

	DEBUGF	1,"Header size: %u\n", cx

	sub	ax, cx

	mov	edi, esi

	mov	esi, [esi + FRAGMENT_entry.NextPtr]

	cmp	esi, -1

	jne	.count_bytes

	mov	esi, [esp+4]  ;;;

	mov	[edi + FRAGMENT_entry.NextPtr], esi			       ; Add this packet to the chain, this simplifies the following code

	mov	[esi + FRAGMENT_entry.NextPtr], -1

	mov	[esi + FRAGMENT_entry.PrevPtr], edi

	mov	[esi + FRAGMENT_entry.Owner], ebx

	mov	cx, [edx + IPv4_Packet.TotalLength]			       ; Note: This time we dont substract Header length

	xchg	cl , ch

	DEBUGF	1,"Packet size: %u\n", cx

	add	ax , cx

	DEBUGF	1,"Total Received data size: %u\n", eax

	push	eax

	mov	ax , [edx + IPv4_Packet.FlagsAndFragmentOffset]

	xchg	al , ah

	shl	ax , 3

	add	cx , ax

	pop	eax

	DEBUGF	1,"Total Fragment size: %u\n", ecx

	cmp	ax, cx

	jne	.destroy_slot_pop

	push	eax

	push	eax

	call	kernel_alloc

	test	eax, eax

	je	.destroy_slot_pop							; If we dont have enough space to allocate the buffer, discard all packets in slot

	mov	edx, [esp+4]								; Get pointer to first fragment entry back in edx

     .rebuild_packet_loop:

	movzx	ecx, word [edx + FRAGMENT_entry.Data + IPv4_Packet.FlagsAndFragmentOffset]	; Calculate the fragment offset

	xchg	cl , ch 									;   intel byte order

	shl	cx , 3										;   multiply by 8 and clear first 3 bits

	DEBUGF	1,"Fragment offset: %u\n", cx

	lea	edi, [eax + ecx]								; Notice that edi will be equal to eax for first fragment

	movzx	ebx, byte [edx + FRAGMENT_entry.Data + IPv4_Packet.VersionAndIHL]		; Find header size (in ebx) of fragment

	and	bx , 0x000F									;

	shl	bx , 2										;

	lea	esi, [edx + FRAGMENT_entry.Data]						; Set esi to the correct begin of fragment

	movzx	ecx, word [edx + FRAGMENT_entry.Data + IPv4_Packet.TotalLength] 		; Calculate total length of fragment

	xchg	cl, ch										;  intel byte order

	cmp	edi, eax									; Is this packet the first fragment ?

	je	.first_fragment

	sub	cx, bx										; If not, dont copy the header

	add	esi, ebx									;

     .first_fragment:

	push	cx										; First copy dword-wise, then byte-wise

	shr	cx, 2										;

	rep	movsd										;

	pop	cx										;

	and	cx, 3										;

	rep	movsb										;

	push	eax

	push	edx										; Push pointer to fragment onto stack

	mov	edx, [edx + FRAGMENT_entry.NextPtr]						; Set edx to the next pointer

	call	kernel_free									; free the previous fragment buffer (this uses the value from stack)

	pop	eax

	cmp	edx, -1 									; Check if it is last fragment in chain

	jne	.rebuild_packet_loop

	pop	ecx										;

	xchg	cl, ch

	mov	edx, eax

	mov	word [edx + IPv4_Packet.TotalLength], cx

	add	esp, 8

	xchg	cl, ch		   ;  This prints the IP packet to the debug board (usefull when using serial output debug..)

	push	ecx  ;;;;

	push	eax	;;;;

;        mov     esi, edx           ;

;                                   ;

;       @@:                         ;

;        lodsb                      ;

;        DEBUGF  1,"%x ", eax:2     ;

;        loop    @r                 ;

	movzx	eax, byte [edx + IPv4_Packet.VersionAndIHL]	; Calculate Header length by using IHL field

	and	ax, 0x000F					;

	shl	ax, 2						;

	sub	ecx, eax

	add	eax, edx

	push	eax

	mov	al , [edx + IPv4_Packet.Protocol]

	mov	esi, [edx + IPv4_Packet.SourceAddress]

	mov	edi, [edx + IPv4_Packet.DestinationAddress]

	pop	edx						; Offset to data (tcp/udp/icmp/.. Packet)

	cmp	al , IP_PROTO_TCP

	je	TCP_handler

	cmp	al , IP_PROTO_UDP

	je	UDP_handler

	cmp	al , IP_PROTO_ICMP

	je	ICMP_handler_fragments

	DEBUGF	1,"IP_Handler - unknown protocol:%u\n",al

	call	kernel_free

	add	esp, 8						; pop (balance stack)

	ret

  .destroy_slot_pop:

	add	esp, 4

  .destroy_slot:

	DEBUGF	1,"Destroy fragment slot!\n"

	; TODO!

	jmp	.dump

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

;

; find fragment slot

;

; IN: pointer to fragmented packet in edx         ; TODO: the RFC says we should check protocol too

; OUT: pointer to slot in edi, -1 on error

;

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

  .find_fragment_slot:

	push	eax ebx ecx edx

	mov	ax , word [edx + IPv4_Packet.Identification]

	mov	ecx, MAX_FRAGMENTS

	mov	esi, FRAGMENT_LIST

	mov	ebx, dword [edx + IPv4_Packet.SourceAddress]

	mov	edx, dword [edx + IPv4_Packet.DestinationAddress]

  .find_slot:

	cmp	word [esi + FRAGMENT_slot.id], ax

	jne	.try_next

	cmp	dword [esi + FRAGMENT_slot.SrcIP], ebx

	jne	.try_next

	cmp	dword [esi + FRAGMENT_slot.DstIP], edx

	je	.found_slot

  .try_next:

	add	esi, FRAGMENT_slot.size

	loop	.find_slot

 ;       pop     edx ebx

	or	esi, -1

;        ret

  .found_slot:

	pop	edx ecx ebx eax

	ret

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

;

; Decrease TimeToLive of all fragment slots

;

; IN: /

; OUT: /

;

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

align 4

IPv4_decrease_fragment_ttls:

	mov	esi, FRAGMENT_LIST

	mov	ecx, MAX_FRAGMENTS

  .loop:

	cmp	[esi + FRAGMENT_slot.ttl], 0

	je	.try_next

	dec	[esi + FRAGMENT_slot.ttl]

	jnz	.try_next

	DEBUGF 1,"Fragment slot timed-out!\n"

	; TODO: clear all entry's of timed-out slot

  .try_next:

	add	esi, 4

	loop	.loop

	ret

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

;

; Create_IPv4_Packet

;

; IN: eax = dest ip

;     ebx = source ip

;     ecx = data length

;     dx  = fragment id

;     di  = protocol

;

; OUT: eax = pointer to buffer start

;      ebx = pointer to device struct (needed for sending procedure)

;      ecx = unchanged (packet size of embedded data)

;      edx = size of complete buffer

;      esi = pointer to sending procedure

;      edi = pointer to start of data (-1 on error)

;

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

;;; TODO: create fragmented packets

align 4

IPv4_create_packet:

	DEBUGF 1,"Create IPv4 Packet (size=%u)\n", ecx

	cmp	ecx, 1480

	jg	.exit_

	test	ebx, ebx	      ; if dest ip = 0

	jnz	.ip_ok		      ; and local ip is valid

				      ; use local ip instead

	cmp	[IP_LIST],0xffffffff  ;

	je	.ip_ok		      ; TODO: find solution to send broadcast

				      ; on device other then device 0

	mov	ebx, [IP_LIST]	      ;

				      ;

  .ip_ok:			      ;

	push	ecx eax ebx dx di

	cmp	eax, -1

	je	.broadcast		  ; If it is broadcast, just send

	call	ARP_IP_to_MAC

	cmp	eax, -1

	je	.not_found

	push	ebx

	push	ax

	jmp	.send

  .broadcast:

	push	word -1

	push	dword -1

  .send:

	call	IPv4_dest_to_dev

	inc	[IP_PACKETS_TX+4*edi]

	mov	edx, [ETH_DRV_LIST + 4*edi]

	lea	eax, [edx + ETH_DEVICE.mac]

	mov	ebx, esp

	mov	ecx, [esp+18]	 ;; 18 or  22 ??

	add	ecx, IPv4_Packet.DataOrOptional

	mov	di , ETHER_IPv4

	call	ETH_create_packet		   ; TODO: figure out a way to make this work with other protocols too

	add	esp, 6

	cmp	edi, -1

	je	.exit

	mov	[edi + IPv4_Packet.VersionAndIHL], 0x45   ; IPv4, normal length (no Optional header)

	mov	[edi + IPv4_Packet.TypeOfService], 0

	xchg	ch, cl

	mov	[edi + IPv4_Packet.TotalLength], cx

	mov	[edi + IPv4_Packet.FlagsAndFragmentOffset], 0x0000

	mov	[edi + IPv4_Packet.TimeToLive], 128

	mov	[edi + IPv4_Packet.HeaderChecksum], 0

	pop	cx

	mov	[edi + IPv4_Packet.Protocol], cl

	pop	cx

	mov	[edi + IPv4_Packet.Identification], cx

	pop	ecx

	mov	[edi + IPv4_Packet.SourceAddress], ecx

	pop	ecx

	mov	[edi + IPv4_Packet.DestinationAddress], ecx

	push	eax ebx edx

	; calculate checksum

	xor	edx, edx

	mov	esi, edi

	mov	ecx, IPv4_Packet.DataOrOptional

	call	checksum_1

	call	checksum_2

	mov	[edi + IPv4_Packet.HeaderChecksum], dx

	pop	edx ebx eax ecx

	add	edi, IPv4_Packet.DataOrOptional

	DEBUGF 1,"IPv4 Packet for device %x created successfully\n", ebx

	ret

  .not_found:

	DEBUGF 1,"Create IPv4 Packet - ARP entry not found!\n"

	; TODO: QUEUE the packet to resend later!

  .exit:

	add	esp, 16

  .exit_:

	DEBUGF 1,"Create IPv4 Packet - failed\n"

	or	edi, -1

	ret

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

;

; IPv4_dest_to_dev

;

; IN: Destination IP in eax

; OUT: device id in edi

;

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

align 4

IPv4_dest_to_dev:

	DEBUGF 1,"IPv4 destination to device: "

	xor	edi, edi

	mov	ecx, MAX_IP

  .loop:

	mov	ebx, [IP_LIST+edi]		; we dont need to worry about non exisiting ip interfaces

	and	ebx, [SUBNET_LIST+edi]		; they have IP and SUBNET set to all one's, so they will have no match except 255.255.255.255

						; (only a moron would insert that ip into this function..)

	mov	edx, eax

	and	edx, [SUBNET_LIST+edi]

	cmp	ebx, edx

	je	.found_it

	add	edi, 4

	loop	.loop

	xor	edi, edi	; if none found, use device 0 as default device

  .found_it:

	shr	edi, 2

	DEBUGF 1,"%u\n",edi

	ret

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

;

; IPv4_get_frgmnt_num

;

; IN: /

; OUT: fragment number in ax

;

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

align 4

IPv4_get_frgmnt_num:

	xor	ax, ax	;;; TODO: replace this with real code

	ret

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

;

; IPv4_API

;

; This function is called by system function 75

;

; IN:  subfunction number in bl

;      device number in bh

;      ecx, edx, .. depends on subfunction

;

; OUT:

;

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

align 4

IPv4_API:

	movzx	eax, bh

	shl	eax, 2

	test	bl, bl

	jz	.packets_tx	; 0

	dec	bl

	jz	.packets_rx	; 1

	dec	bl

	jz	.read_ip	; 2

	dec	bl

	jz	.write_ip	; 3

	dec	bl

	jz	.read_dns	; 4

	dec	bl

	jz	.write_dns	; 5

	dec	bl

	jz	.read_subnet	; 6

	dec	bl

	jz	.write_subnet	; 7

	dec	bl

	jz	.read_gateway	; 8

	dec	bl

	jz	.write_gateway	; 9

.error:

	mov	eax, -1

	ret

.packets_tx:

	add	eax, IP_PACKETS_TX

	mov	eax, [eax]

	ret

.packets_rx:

	add	eax, IP_PACKETS_RX

	mov	eax, [eax]

	ret

.read_ip:

	add	eax, IP_LIST

	mov	eax, [eax]

	ret

.write_ip:

	add	eax, IP_LIST

	mov	[eax], ecx

	xor	eax, eax

	ret

.read_dns:

	add	eax, DNS_LIST

	mov	eax, [eax]

	ret

.write_dns:

	add	eax, DNS_LIST

	mov	[eax], ecx

	xor	eax, eax

	ret

.read_subnet:

	add	eax, SUBNET_LIST

	mov	eax, [eax]

	ret

.write_subnet:

	add	eax, SUBNET_LIST

	mov	[eax], ecx

	xor	eax, eax

	ret

.read_gateway:

	add	eax, GATEWAY_LIST

	mov	eax, [eax]

	ret

.write_gateway:

	add	eax, GATEWAY_LIST

	mov	[eax], ecx

	xor	eax, eax

	ret