Subversion Repositories Kolibri OS

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

;;                                                                 ;;

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

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

;;                                                                 ;;

;;  TCP.INC                                                        ;;

;;                                                                 ;;

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

;;                                                                 ;;

;;    Written by hidnplayr@kolibrios.org                           ;;

;;                                                                 ;;

;;          GNU GENERAL PUBLIC LICENSE                             ;;

;;             Version 2, June 1991                                ;;

;;                                                                 ;;

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

$Revision: 1274 $

TCP_RETRIES		equ 5		; Number of times to resend a Packet

TCP_PACKET_TTL		equ 50		; resend if not replied to in 1/100 s

TCP_SOCKET_TTL		equ 10		; # of secs to wait before closing socket

TCP_QUEUE_SIZE		equ 16

struct	TCP_Packet

	.SourcePort		dw ?

	.DestinationPort	dw ?

	.SequenceNumber 	dd ?

	.AckNumber		dd ?

	.DataOffset		db ?	; DataOffset[0-3 bits] and Reserved[4-7]

	.Flags			db ?	; Reserved[0-1 bits]|URG|ACK|PSH|RST|SYN|FIN

	.Window 		dw ?

	.Checksum		dw ?

	.UrgentPointer		dw ?

;        .Options                rb 3

;        .Padding                db ?

	.Data:

ends

struct	tcp_in_queue_entry

	.data_ptr	dd ?

	.data_size	dd ?

	.offset 	dd ?

	.size:

ends

struct	tcp_out_queue_entry

	.data_ptr	dd ?

	.data_size	dd ?

	.ttl		dd ?

	.retries	dd ?

	.owner		dd ?

	.sendproc	dd ?

	.seq_num	dd ?

	.socket 	dd ?

	.size:

ends

align 4

uglobal

	TCP_PACKETS_TX		rd  MAX_IP

	TCP_PACKETS_RX		rd  MAX_IP

	TCP_IN_QUEUE		rd  (tcp_in_queue_entry.size*TCP_QUEUE_SIZE+queue.data)/4

	TCP_OUT_QUEUE		dd  ?

				rd  (tcp_out_queue_entry.size*TCP_QUEUE_SIZE)/4

endg

align 4

iglobal

stateHandler:

  dd  stateTCB_LISTEN

  dd  stateTCB_SYN_SENT

  dd  stateTCB_SYN_RECEIVED

  dd  stateTCB_ESTABLISHED

  dd  stateTCB_FIN_WAIT_1

  dd  stateTCB_FIN_WAIT_2

  dd  stateTCB_CLOSE_WAIT

  dd  stateTCB_CLOSING

  dd  stateTCB_LAST_ACK

  dd  stateTCB_TIME_WAIT

  dd  stateTCB_CLOSED

endg

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

;

; TCP_init

;

;  This function resets all TCP variables

;

;  IN:  /

;  OUT: /

;

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

align 4

TCP_init:

	xor	eax, eax

	mov	edi, TCP_PACKETS_TX

	mov	ecx, 2*MAX_IP

	rep	stosd

	init_queue TCP_IN_QUEUE

; tcp_out_queue is a special type of queue:

; The first dword is a counter of total packets queued.

; The remaining bytes are socket 'slots' wich use tcp_out_queue_entry data structure.

; An empty slot is know by the fact that tcp_out_queue_entry.data_ptr (first dword of the slot) is set to 0

; There are TCP_OUT_QUEUE_SIZE number of slots

	xor	eax, eax

	mov	esi, TCP_OUT_QUEUE

	mov	ecx, TCP_QUEUE_SIZE*tcp_out_queue_entry/4+1

	rep	stosd

	ret

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

;

;  TCP_decrease_socket_ttls

;

;  IN:  /

;  OUT: /

;

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

align 4

TCP_decrease_socket_ttls:

; scan through all the sockets, decrementing active timers

	mov	ebx, net_sockets

	cmp	[ebx + SOCKET_head.NextPtr], 0

	je	.exit

  .next_socket:

	mov	ebx, [ebx + SOCKET_head.NextPtr]

	or	ebx, ebx

	jz	.exit

	cmp	[ebx + SOCKET_head.Type], IP_PROTO_TCP

	jne	.next_socket

;        DEBUGF  1, "K :   %x-%x: %x-%x-%x-%u\n", [ebx + SOCKET.PID]:2, [ebx + SOCKET.Number]:2, [ebx + SOCKET.LocalPort]:4, [ebx + SOCKET.RemoteIP], [ebx + SOCKET.RemotePort]:4, [ebx + SOCKET.state]

	cmp	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.timer], 0

	jne	.decrement_tcb

	cmp	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.wndsizeTimer], 0

	jne	.decrement_wnd

	jmp	.next_socket

  .decrement_tcb:

; decrement it, delete socket if TCB timer = 0 & socket in timewait state

	dec	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.timer]

	jnz	.next_socket

	cmp	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.state], TCB_TIMED_WAIT

	jne	.next_socket

	push	[ebx + SOCKET_head.PrevPtr]

	stdcall net_socket_free, ebx

	pop	ebx

	jmp	.next_socket

  .decrement_wnd:

	dec	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.wndsizeTimer]

	jmp	.next_socket

  .exit:

	ret

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

;

; TCP_send_queued:

;

;  Decreases 'ttl' of tcp packets queued.

;  if 'ttl' reaches 0, resend the packet and decrease 'retries'

;  if 'retries' reaches zero, remove the queued packet

;

;  IN:  /

;  OUT: /

;

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

align 4

TCP_send_queued:

	cmp	[TCP_OUT_QUEUE], 0

	je	.exit

	mov	eax, TCP_QUEUE_SIZE

	mov	ecx, [TCP_OUT_QUEUE]

	mov	esi, TCP_OUT_QUEUE+4

  .loop:

	cmp	[esi + tcp_out_queue_entry.data_ptr], 0

	jnz	.found_one

	add	esi, tcp_out_queue_entry.size

	loop	.loop

  .exit:

	ret

  .found_one:

	dec	[esi + tcp_out_queue_entry.ttl]

	jz	.send_it

  .find_next:

	add	esi, tcp_out_queue_entry.size

	dec	eax

	jz	.exit

	test	ecx, ecx

	jnz	.loop

	ret

  .send_it:

	push	eax ecx esi

	mov	ebx, [esi + tcp_out_queue_entry.owner]

	push	[esi + tcp_out_queue_entry.data_size]

	push	[esi + tcp_out_queue_entry.data_ptr]

	DEBUGF 1,"Now sending TCP packet %x, size: %u, owner: %x, sendproc %x\n", [esp], [esp+4], ebx, [esi + tcp_out_queue_entry.sendproc]

	inc	[TCP_PACKETS_TX]

	call	[esi + tcp_out_queue_entry.sendproc]

	add	esp, 8

	pop	esi ecx eax

	dec	[esi + tcp_out_queue_entry.retries]

	jz	.remove_it

	mov	[esi + tcp_out_queue_entry.ttl], TCP_PACKET_TTL

	jmp	.find_next

  .remove_it:

	push	[esi + tcp_out_queue_entry.data_ptr]

	mov	[esi + tcp_out_queue_entry.data_ptr], 0

	call	kernel_free

	jmp	.find_next

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

;

; TCP_handler:

;

;  Called by IPv4_handler,

;  this procedure will inject the tcp data diagrams in the application sockets.

;

;  IN:  Pointer to buffer in [esp]

;       size of buffer in [esp+4]

;       pointer to device struct in ebx

;       TCP Packet size in ecx

;       pointer to TCP Packet in edx

;       SourceAddres (IPv4) in esi

;  OUT: /

;

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

align 4

TCP_handler :

       DEBUGF 1,"TCP_Handler\n"

; TODO: validate checksum

; IP Packet TCP Destination Port = local Port

; IP Packet SA = Remote IP  OR = 0

; IP Packet TCP Source Port = remote Port  OR = 0

	mov	ebx, net_sockets

  .socket_loop:

	mov	ebx, [ebx + SOCKET_head.NextPtr]

	or	ebx, ebx

	jz	.dump

	mov	ax, [edx + TCP_Packet.DestinationPort]

	cmp	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.LocalPort], ax

	jne	.socket_loop

	mov	eax, [ebx + SOCKET_head.end + IPv4_SOCKET.RemoteIP]

	cmp	eax, esi

	je	@f

	test	eax, eax

	jne	.socket_loop

       @@:

	mov	ax, [ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.RemotePort]

	cmp	[edx + TCP_Packet.SourcePort] , ax

	je	.found_socket

	test	ax, ax

	jnz	.socket_loop

  .found_socket:

       DEBUGF 1,"Found valid socket for packet\n"

	inc	[TCP_PACKETS_RX]

	add	ebx, SOCKET_head.lock

	call	wait_mutex

	sub	ebx, SOCKET_head.lock

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

; ebx is pointer to socket

; ecx is size of tcp packet

; edx is pointer to tcp packet

; calculate header length

	movzx	eax, [edx + TCP_Packet.DataOffset]

	and	eax, 11110000b

	shr	eax, 2

       DEBUGF 1,"TCP header size: %u\n", eax

	sub	ecx, eax

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

; ecx is size of tcp data

; as a Packet has been received, update the TCB timer

	mov	[ebx +	SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.timer], TCP_SOCKET_TTL

; If the received Packet has an ACK bit set, remove any Packets in the resend queue that this received Packet acknowledges

	test	[edx + TCP_Packet.Flags], TH_ACK

	jz	.no_ack 				 ; No ACK, so no data yet

; Calculate ACK number

	mov	edi, [edx + TCP_Packet.AckNumber]

	bswap	edi

	mov	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.last_ack_number], edi

       DEBUGF 1,"Setting last_ack_number to %u\n", edi

	bswap	edi

; Dequeue all acknowledged packets

	cmp	[TCP_OUT_QUEUE], 0		; first, check if any packets are queued at all

	je	.no_ack

	push	ecx

       DEBUGF 1,"Removing all queued packets with smaller ACK\n"

	mov	ecx, TCP_QUEUE_SIZE

	mov	esi, TCP_OUT_QUEUE+4

  .loop:

	cmp	[esi + tcp_out_queue_entry.data_ptr], 0

	je	.maybe_next

	cmp	[esi + tcp_out_queue_entry.socket], ebx

	jne	.maybe_next

	cmp	[esi + tcp_out_queue_entry.seq_num], edi

	jg	.maybe_next

       DEBUGF 1,"Removing a queued packet\n"

	push	[esi + tcp_out_queue_entry.data_ptr]

	mov	[esi + tcp_out_queue_entry.data_ptr], 0

	dec	[TCP_OUT_QUEUE]

	call	kernel_free

  .maybe_next:

	add	esi, tcp_out_queue_entry.size

	loop	.loop

	pop	ecx

; Now call the correct handler, depending on the socket state

  .no_ack:

	mov	eax, [ebx +  SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.state]

	cmp	eax, TCB_LISTEN

	jb	.dump

	cmp	eax, TCB_CLOSED

	ja	.dump

	dec	eax

	shl	eax, 2

	add	eax, stateHandler

	call	dword[eax]

  .dump:

	DEBUGF 1,"Dumping TCP packet\n"

	call	kernel_free

	add	esp, 4 ; pop (balance stack)

	ret

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

;

; TCP_send  (Assumes socket mutex set)

;

; IN: eax = socket pointer

;      bl = flags

;      ecx = number of bytes to send, may be set to 0

;      esi = pointer to data

;

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

align 4

TCP_send:

	DEBUGF 1,"Creating TCP packet, socket: %x, flags: %x\n",eax, bl

	mov	di , IP_PROTO_TCP

	add	ecx, TCP_Packet.Data

	push	bx eax esi

; Create an IPv4 Packet of the correct size

	mov	ebx, [eax + SOCKET_head.end + IPv4_SOCKET.LocalIP]

	mov	eax, [eax + SOCKET_head.end + IPv4_SOCKET.RemoteIP]

	call	IPv4_create_packet

	cmp	edi, -1

	je	.fail

; If there is any data, copy it first

	pop	esi

	push	edi

	add	edi, TCP_Packet.Data

	sub	ecx, TCP_Packet.Data

	shr	ecx, 1

	jnc	.nb

	movsb

.nb:	shr	ecx, 1

	jnc	.nw

	movsw

.nw:	test	ecx, ecx

	jz	.nd

	rep	movsd

.nd:

	pop	edi

; Fill in the TCP header

	pop	esi

; fill in tcp sequence number

	push	[esi + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.SND_NXT]

	pop	[edi + TCP_Packet.SequenceNumber]

	inc_INET (ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.SND_NXT) ;;;;;;;;

; Fill in local and remote ports

	push	dword [esi + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.LocalPort]

	pop	dword [edi + TCP_Packet.SourcePort]

; Acknumber

	push	[esi + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.RCV_NXT]

	pop	[edi + TCP_Packet.AckNumber]

; Fill  in other tcp options

	pop	cx

	mov	[edi + TCP_Packet.Flags], cl

	mov	[edi + TCP_Packet.Window], 0x0005	   ; 1280 bytes

	mov	[edi + TCP_Packet.UrgentPointer], 0

	mov	[edi + TCP_Packet.DataOffset], 0x50

	mov	[edi + TCP_Packet.Checksum], 0

; Push pointer to and size of total packet (needed for send procedure)

	push	edx eax

; push socket number (for TCP_add_to_queue)

	push	esi

; Now, calculate the checksum                  ; TODO: calculate correct checksum for packets with data

	pushw	TCP_Packet.Data shl 8

	pushw	IP_PROTO_TCP shl 8

	pushd	[edi-4] ; destination address  ; TODO: fix this, IPv4 packet could have options..

	pushd	[edi-8] ; source address

	xor	edx, edx

	mov	ecx, TCP_Packet.Data

	mov	esi, edi

	call	checksum_1

	mov	ecx, 12

	mov	esi, esp

	call	checksum_1

	add	esp, 12 				   ; remove the pseudoheader from stack

; and store it in TCP header

	call	checksum_2

	mov	[edi + TCP_Packet.Checksum], dx

; At last send the packet!

	DEBUGF 1,"Sending TCP Packet to device %x\n", ebx

	mov	edx, [edi + TCP_Packet.SequenceNumber]

	bswap	edx

	mov	esi, [ebx + ETH_DEVICE.transmit]

	pop	edi

	jmp	TCP_queue

  .fail:

	add	esp, 2+4

	or	eax, -1

	ret

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

;

;  Queue a TCP packet for sending

;

;  IN:  [esp] pointer to buffer

;       [esp + 4] size of buffer

;       ebx = driver struct

;       esi = sender proc

;       edx = sequence number of this packet in normal byte order

;       edi = socket number

;  OUT: /

;

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

align 4

TCP_queue:

	bswap	edx

	DEBUGF 1,"Adding packet to TCP queue, buffer: %x, size: %u, driver: %x, acknum: %u\n", [esp], [esp+4], ebx, edx

	bswap	edx

	cmp	[TCP_OUT_QUEUE], TCP_QUEUE_SIZE

	jge	.full

	mov	ecx, TCP_QUEUE_SIZE

	mov	eax, TCP_OUT_QUEUE+4

  .loop:

	cmp	[eax + tcp_out_queue_entry.data_ptr], 0

	je	.found_it

	add	eax, tcp_out_queue_entry.size

	loop	.loop

  .full:			; silently discard the packet

	DEBUGF 1,"TCP queue is full!\n"

	call	kernel_free

	add	esp, 4

	ret

  .found_it:			; eax points to empty queue entry

	pop	[eax + tcp_out_queue_entry.data_ptr]

	pop	[eax + tcp_out_queue_entry.data_size]

	mov	[eax + tcp_out_queue_entry.ttl], 1			; send immediately

	mov	[eax + tcp_out_queue_entry.retries], TCP_RETRIES

	mov	[eax + tcp_out_queue_entry.owner], ebx

	mov	[eax + tcp_out_queue_entry.sendproc], esi

	mov	[eax + tcp_out_queue_entry.seq_num], edx

	mov	[eax + tcp_out_queue_entry.socket], edi

	inc	[TCP_OUT_QUEUE]

	sub	eax, TCP_OUT_QUEUE+4

	DEBUGF 1,"Added to queue in pos %u\n", eax

	ret

;---------- TCB state handlers start here

align 4

stateTCB_LISTEN:

	DEBUGF	1,"TCBStateHandler: Listen\n"

	test	[edx + TCP_Packet.Flags], TH_SYN	; SYN packet? => send syn+ack, open new socket and set connection to established

	jz	.exit

; Exit if backlog queue is full

	mov	ax, [ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.backlog_cur]

	cmp	ax, [ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.backlog]

	jae	.exit

; Allocate new socket

	push	esi edi

	call	net_socket_alloc

	test	eax, eax

	jz	.fail

; Copy structure from current socket to new, including lock

	lea	esi, [ebx + SOCKET_head.PID]		; yes, PID must also be copied

	lea	edi, [eax + SOCKET_head.PID]

	mov	ecx, ((SOCKET_head.end - SOCKET_head.PID) + IPv4_SOCKET.end + TCP_SOCKET.end + 3)/4

	rep	movsd

	pop	edi esi

; Push pointer to new socket to queue

	movzx	ecx, [ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.backlog_cur]

	inc	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.backlog_cur]

	mov	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.end + ecx*4], eax

	mov	[eax + SOCKET_head.end + IPv4_SOCKET.RemoteIP], esi ; IP source address

	mov	cx, [edx + TCP_Packet.SourcePort]

	mov	[eax + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.RemotePort], cx

	mov	ecx, [edx + TCP_Packet.SequenceNumber]

	mov	[eax + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.IRS], ecx

	mov	[eax + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.RCV_NXT], ecx

	lea	esi, [eax + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.RCV_NXT]

	inc_INET esi ; RCV.NXT

	mov	ecx, [eax + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.ISS]

	mov	[eax + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.SND_NXT], ecx

	mov	[ebx + SOCKET_head.lock], 0

	push	eax

; Now construct the response

	mov	bl, TH_SYN + TH_ACK

	xor	ecx, ecx

	call	TCP_send

	pop	eax

	mov	[eax + SOCKET_head.lock], 0

	mov	[eax +	SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.state], TCB_SYN_RECEIVED

	call	notify_network_event

	ret

  .exit:

	mov	[ebx + SOCKET_head.lock], 0

	ret

  .fail:

	add	esp, 8

	mov	[ebx + SOCKET_head.lock], 0

	ret

align 4

stateTCB_SYN_SENT:

	DEBUGF	1,"TCBStateHandler: Syn_Sent\n"

	; We are awaiting an ACK to our SYN, with a SYM

	; Look at control flags - expecting an ACK

	mov	al, [edx + TCP_Packet.Flags]

	test	al, TH_RST

	jnz	.reset			; jump if RST bit set

	push	[edx + TCP_Packet.SequenceNumber]				     ;;

	pop	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.RCV_NXT]	     ;;

	inc_INET (ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.RCV_NXT)      ;;

	push	[edx + TCP_Packet.AckNumber]					    ;;;;;;

	pop	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.SND_NXT]	    ;;;;;;

	and	al, TH_SYN + TH_ACK

	jz	.exit			; jump if none of the following is set: RST, SYN, ACK

	test	al, TH_ACK

	jz     .onlysyn 		; jump if only SYN bit is set

	; If we arrived here, SYN and ACK are set

	mov	[ebx +	SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.state], TCB_ESTABLISHED

	pushw	TH_ACK

  .send:	; Send an ACK

	mov	eax, ebx

	pop	bx

	push	eax

	xor	ecx, ecx

	call	TCP_send

	pop	ebx

  .exit:

	mov	[ebx + SOCKET_head.lock], 0

	ret

  .reset:

	; TODO: ....

	; remove all queued TCP packets for this connection !

	mov	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.state], TCB_CLOSED

	mov	[ebx + SOCKET_head.lock], 0

	ret

  .onlysyn:

	mov	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.state], TCB_SYN_RECEIVED

	pushw	TH_SYN + TH_ACK

	jmp	.send

align 4

stateTCB_SYN_RECEIVED:

	DEBUGF	1,"TCBStateHandler: Syn_received\n"

	test	[edx + TCP_Packet.Flags], TH_RST	; reset connection? => LISTEN

	jz	.check_ack

	push	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.OrigRemotePort]

	pop	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.RemotePort]

	push	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.OrigRemoteIP]

	pop	[ebx + SOCKET_head.end + IPv4_SOCKET.RemoteIP]

	mov	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.state], TCB_LISTEN

	jmp	.exit

  .check_ack:

	test	[edx + TCP_Packet.Flags], TH_ACK	; ACK? => connection established!

	jz	.exit

	mov	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.state], TCB_ESTABLISHED

	mov	eax, ebx

	call	notify_network_event

  .exit:

	mov	[ebx + SOCKET_head.lock], 0

	ret

align 4

stateTCB_ESTABLISHED:

	DEBUGF	1,"TCBStateHandler: Established\n"

	mov	eax, [ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.RCV_NXT]

	bswap	eax

	DEBUGF	1,"RCV_NXT is set to:%u\n", eax

	bswap	eax

	cmp	eax, [edx + TCP_Packet.SequenceNumber]

	jne	.exit

; Calculate next sequencenumber

	test	ecx, ecx

	jnz	@f

	inc	ecx

       @@:

	add_INET (ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.RCV_NXT)

	test	[edx + TCP_Packet.Flags], TH_FIN

	jnz	.fin

  .check_ack:

	test	[edx + TCP_Packet.Flags], TH_ACK

	jz	.exit

	DEBUGF	1,"Received ACK\n"

; First, look at the incoming window. If this is less than or equal to 1024,

; Set the socket window timer to 1. This will stop an additional Packets being queued.

; ** I may need to tweak this value, since I do not know how many Packets are already queued

	push	ecx

	mov	cx, [edx + TCP_Packet.Window]

	xchg	cl, ch

	cmp	cx, 1024

	ja	@f

	mov	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.wndsizeTimer], 1

      @@:

	pop	ecx

; Now, see if we received any data

	test	ecx, ecx

	jz	.ack

	DEBUGF	1,"Got %u bytes data!\n", ecx

; calculate header length

	movzx	eax, [edx + TCP_Packet.DataOffset]

	and	eax, 11110000b

	shr	eax, 2

       DEBUGF 1,"TCP header size: %u\n", eax

	add	edx, eax

	add	esp, 4

	pop	esi

	add	esp, 4

	sub	edx, esi

	mov	edi, edx

	mov	eax, ebx

	jmp	socket_internal_receiver	; Place the data from packet into socket

  .ack:

	mov	eax, ebx

	mov	bl, TH_ACK

	push	eax

	xor	ecx, ecx

	call	TCP_send		    ; send the ack

	pop	ebx

  .exit:

	mov	[ebx + SOCKET_head.lock], 0

	ret

  .fin:

; Remove all resend entries from the queue

	mov	ecx, TCP_QUEUE_SIZE

	mov	esi, TCP_OUT_QUEUE+4

  .removeloop:

	cmp	[esi + tcp_out_queue_entry.data_ptr], 0

	je	.maybe_next

	; TODO: check if the packets belong to the same tcp connection !

       DEBUGF 1,"Removing a queued packet\n"

	push	[esi + tcp_out_queue_entry.data_ptr]

	mov	[esi + tcp_out_queue_entry.data_ptr], 0

	dec	[TCP_OUT_QUEUE]

	call	kernel_free

  .maybe_next:

	add	esi, tcp_out_queue_entry.size

	loop	.removeloop

; Send an ACK to that fin, and enter closewait state

	mov	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.state], TCB_CLOSE_WAIT

	jmp	.check_ack

align 4

stateTCB_FIN_WAIT_1:

	DEBUGF	1,"TCBStateHandler: Fin_wait_1\n"

	; We can either receive an ACK of a fin, or a fin

	mov	al, [edx + TCP_Packet.Flags]

	and	al, TH_FIN + TH_ACK

	cmp	al, TH_ACK

	jne	@f

	; It was an ACK

	mov	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.state], TCB_FIN_WAIT_2

	jmp	.exit

    @@: mov	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.state], TCB_CLOSING

	cmp	al, TH_FIN

	je	@f

	mov	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.state], TCB_TIMED_WAIT

    @@:

;        lea     esi, [ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.RCV_NXT]

;        inc_INET esi

	; Send an ACK

	mov	eax, ebx

	mov	bl, TH_ACK

	push	eax

	xor	ecx, ecx

	call	TCP_send

	pop	ebx

  .exit:

	mov	[ebx + SOCKET_head.lock], 0

	ret

align 4

stateTCB_FIN_WAIT_2:

	DEBUGF	1,"TCBStateHandler: Fin_wait_2\n"

	test	[edx + TCP_Packet.Flags], TH_FIN

	jz	.exit

	; Change state, as we have a fin

	mov	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.state], TCB_TIMED_WAIT

	lea	esi, [ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.RCV_NXT]

	inc_INET esi

	mov	[ebx + SOCKET_head.lock], 0

	; Send an ACK

	mov	eax, ebx

	mov	bl, TH_ACK

	push	eax

	xor	ecx, ecx

	call	TCP_send

	pop	ebx

  .exit:

	mov	[ebx + SOCKET_head.lock], 0

	ret

align 4

stateTCB_CLOSE_WAIT:

	DEBUGF	1,"TCBStateHandler: close_wait\n"

	; Intentionally left empty

	; socket_close_tcp handles this

	mov	[ebx + SOCKET_head.lock], 0

	ret

align 4

stateTCB_CLOSING:

	DEBUGF	1,"TCBStateHandler: closingn\n"

	; We can either receive an ACK of a fin, or a fin

	test	[edx + TCP_Packet.Flags], TH_ACK

	jz	.exit

	mov	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.state], TCB_TIMED_WAIT

  .exit:

	mov	[ebx + SOCKET_head.lock], 0

	ret

align 4

stateTCB_LAST_ACK:

	DEBUGF	1,"TCBStateHandler: last_ackn\n"

	; Look at control flags - expecting an ACK

	test	[edx + TCP_Packet.Flags], TH_ACK

	jz	.exit

	mov	[ebx + SOCKET_head.lock], 0

	; delete the socket

	stdcall net_socket_free, ebx

  .exit:

	ret

align 4

stateTCB_TIME_WAIT:

	DEBUGF	1,"TCBStateHandler: time_wait\n"

	mov	[ebx + SOCKET_head.lock], 0

	ret

align 4

stateTCB_CLOSED:

	DEBUGF	1,"TCBStateHandler: closed\n"

	mov	[ebx + SOCKET_head.lock], 0

	ret

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

;

; TCP_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

TCP_API:

	movzx	eax, bh

	shl	eax, 2

	test	bl, bl

	jz	.packets_tx	; 0

	dec	bl

	jz	.packets_rx	; 1

.error:

	mov	eax, -1

	ret

.packets_tx:

	add	eax, TCP_PACKETS_TX

	mov	eax, [eax]

	ret

.packets_rx:

	add	eax, TCP_PACKETS_RX

	mov	eax, [eax]

	ret