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: 1249 $

TCB_LISTEN		equ 1

TCB_SYN_SENT		equ 2

TCB_SYN_RECEIVED	equ 3

TCB_ESTABLISHED 	equ 4

TCB_FIN_WAIT_1		equ 5

TCB_FIN_WAIT_2		equ 6

TCB_CLOSE_WAIT		equ 7

TCB_CLOSING		equ 8

TCB_LAST_ACK		equ 9

TCB_TIMED_WAIT		equ 10

TCB_CLOSED		equ 11

TH_FIN			equ 1 shl 0

TH_SYN			equ 1 shl 1

TH_RST			equ 1 shl 2

TH_PUSH 		equ 1 shl 3

TH_ACK			equ 1 shl 4

TH_URG			equ 1 shl 5

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

TCP_RETRIES		equ 5		; Number of times to resend a Packet

TCP_TIMEOUT		equ 10		; resend if not replied to in 1/100 s

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

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

TCBStateHandler:

  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

macro inc_INET reg {

	inc	byte [reg + 0]

	adc	byte [reg + 1], 0

	adc	byte [reg + 2], 0

	adc	byte [reg + 3], 0

}

macro add_INET reg {

	rol	ecx, 16

	adc	byte [reg + 0], ch

	adc	byte [reg + 1], cl

	rol	ecx, 16

	adc	byte [reg + 2], ch

	adc	byte [reg + 3], cl

}

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

;

; 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

	init_queue TCP_OUT_QUEUE

	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.TCBState]

	cmp	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.TCBTimer], 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.TCBTimer]

	jnz	.next_socket

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

	jne	.next_socket

	push	[ebx + SOCKET_head.PrevPtr]

	stdcall net_socket_free, ebx

	pop	ebx

	jmp	.next_socket

  .decrement_wnd:

	; TODO - prove it works!

	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:

	dec	eax

	jz	.exit

	jmp	.loop

  .send_it:

	push	eax ecx esi

	push	[esi + tcp_out_queue_entry.data_size]

	push	[esi + tcp_out_queue_entry.data_ptr]

	mov	ebx, [esi + tcp_out_queue_entry.owner]

	call	[esi + tcp_out_queue_entry.sendproc]

	pop	esi ecx eax

	dec	[esi + tcp_out_queue_entry.retries]

	jz	.remove_it

	mov	[esi + tcp_out_queue_entry.ttl], TCP_TIMEOUT

	jmp	.find_next

  .remove_it:

	push	[esi + tcp_out_queue_entry.data_ptr]

	mov	[esi + tcp_out_queue_entry.data_ptr], 0

	dec	[TCP_OUT_QUEUE]

	call	kernel_free

	jmp	.find_next

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

;

; TCP_add_to_queue:

;

;  Queue a TCP packet for sending

;

;  IN:  [esp] pointer to buffer

;       [esp + 4] size of buffer

;       ebx = driver struct

;       esi = sender proc

;       edx = acknum

;  OUT: /

;

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

align 4

TCP_add_to_queue:

	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

	call	kernel_free

	add	esp, 4

	ret

  .found_it:			; eax point 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.ack_num], edx

	ret

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

;

; 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 data in edx

;       SourceAddres in esi

;  OUT: /

;

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

align 4

TCP_handler :

       DEBUGF 1,"TCP_Handler\n"

	; 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	.change_state

	test	ax, ax

	jne	.socket_loop

  .change_state:

	push	ebx

	lea	ebx, [ebx + SOCKET_head.lock]

	call	wait_mutex

	pop	ebx

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

; ebx is pointer to socket

; ecx is size of tcp packet

; edx is pointer to tcp packet

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

	mov	[ebx +	SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.TCBTimer], TWOMSL

	; 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	.call_handler					; No ACK, so no data yet

	mov	eax, [edx + TCP_Packet.SequenceNumber]		; Calculate sequencenumber in eax

	bswap	eax						;

	add	eax, ecx					;

	cmp	[TCP_OUT_QUEUE], 0

	je	.call_handler

	push	ecx

	mov	ecx, TCP_QUEUE_SIZE

	mov	esi, TCP_OUT_QUEUE+4

  .loop:

	cmp	[esi + tcp_out_queue_entry.data_ptr], 0

	jne	.maybe_next

	cmp	[esi + tcp_out_queue_entry.ack_num], eax

	jg	.maybe_next

	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

  .call_handler:

	; Call handler for given TCB state

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

	cmp	eax, TCB_LISTEN

	jb	.exit

	cmp	eax, TCB_CLOSED

	ja	.exit

	shl	eax, 2

	add	eax, TCBStateHandler - 4

	push	.exit

	jmp	eax

  .exit:

	mov	[ebx + SOCKET_head.lock], 0

  .dump:

	DEBUGF 1,"Dumping TCP packet\n"

	call	kernel_free

	add	esp, 4 ; pop (balance stack)

	ret

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

;

; TCP_socket_send

;

; IN: eax = socket pointer

;     ecx = number of bytes to send

;     esi = pointer to data

;

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

align 4

TCP_socket_send:

	DEBUGF 1,"Creating TCP Packet\n"

	mov	di , IP_PROTO_TCP

; Create an IPv4 Packet of the correct size

	push	eax

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

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

; meanwhile, create the pseudoheader in stack,

; (now that we still have all the variables that are needed.)

	push	cx

	push	di

	push	eax

	push	ebx

	push	ecx esi eax		; save some variables for later

	add	ecx, TCP_Packet.Data

	call	IPv4_create_packet

	cmp	edi, -1

	je	.fail

	pop	esi

; Now add the TCP header to the IPv4 packet

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

	pop	[edi + TCP_Packet.SequenceNumber]

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

	pop	dword [edi + TCP_Packet.SourcePort]

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

	pop	[edi + TCP_Packet.AckNumber]

	mov	al, [eax + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.flags]

	mov	[edi + TCP_Packet.Flags], al

	mov	[edi + TCP_Packet.Window], 0x0005	   ; 1280 bytes               ;;; TODO: read RFC !

	mov	[edi + TCP_Packet.UrgentPointer], 0

	mov	[edi + TCP_Packet.DataOffset], 0x50

	mov	[edi + TCP_Packet.Checksum], 0

; Copy the data

	mov	esi, [esp]

	mov	ecx, [esp+4]

	add	edi, TCP_Packet.Data

	shr	ecx, 1

	jnc	.nb

	movsb

.nb:	shr	ecx, 1

	jnc	.nw

	movsw

.nw:	rep movsd

; Now, calculate the checksum for pseudoheader

	xor	edx, edx

	mov	ecx, 12

	mov	esi, esp

	call	checksum_1

	add	esp, 12 				   ; remove the pseudoheader from stack

; And that of the data

	pop	esi

	pop	ecx

	call	checksum_1

; Now create the final checksum and store it in TCP header

	call	checksum_2

	mov	[edi + TCP_Packet.Checksum], dx

; And now, send it!

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

	mov	esi, ETH_sender

	mov	edx, [edi + TCP_Packet.AckNumber]

	jmp	TCP_add_to_queue

  .fail:

	add	esp, 12+4

	ret

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

;

; TCP_send_ack

;

; IN: eax = socket pointer

;      bl = flags

;

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

align 4

TCP_send_ack:

	DEBUGF 1,"Creating TCP ACK\n"

	mov	di , IP_PROTO_TCP

	mov	cx , TCP_Packet.Data

	push	bx eax

; 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

; Fill in the TCP header

	pop	esi

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

	pop	[edi + TCP_Packet.SequenceNumber]

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

	pop	dword [edi + TCP_Packet.SourcePort]

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

	pop	[edi + TCP_Packet.AckNumber]

	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

	push	eax edx

	push	word TCP_Packet.Data shl 8

	push	IP_PROTO_TCP

	push	[esi + SOCKET_head.end + SOCKET_head.end + IPv4_SOCKET.RemoteIP]

	push	[esi + SOCKET_head.end + SOCKET_head.end + IPv4_SOCKET.LocalIP]

; Now, calculate the checksum for pseudoheader

	xor	edx, edx

	mov	ecx, 12

	mov	esi, esp

	call	checksum_1

	add	esp, 12 				   ; remove the pseudoheader from stack

; Now create the final checksum and store it in TCP header

	call	checksum_2

	mov	[edi + TCP_Packet.Checksum], dx

; And now, send it!

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

	mov	esi, ETH_sender

	mov	edx, [edi + TCP_Packet.AckNumber]

	jmp	TCP_add_to_queue

  .fail:

	add	esp, 12+4

	ret

align 4

stateTCB_LISTEN:

	; In this case, we are expecting a SYN Packet

	; For now, if the Packet is a SYN, process it, and send a response

	; If not, ignore it

	; Look at control flags

	test	[edx + TCP_Packet.Flags], TH_SYN

	jz	.exit

	; We have a SYN. update the socket with this IP Packets details,

	; And send a response

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

	mov	ax, [edx + TCP_Packet.SourcePort]

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

	mov	eax, [edx + TCP_Packet.SequenceNumber]

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

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

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

	inc_INET esi ; RCV.NXT

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

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

	; Now construct the response

	mov	bl, TH_SYN + TH_ACK

	call	TCP_send_ack

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

	; increment SND.NXT in socket

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

	inc_INET esi

  .exit:

	ret

align 4

stateTCB_SYN_SENT:

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

	; Look at control flags - expecting an ACK

	mov	al, [edx + TCP_Packet.Flags]

	and	al, TH_SYN + TH_ACK

	cmp	al, TH_SYN + TH_ACK

	je	.syn_ack

	test	al, TH_SYN

	jz	.exit

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

	push	TH_SYN + TH_ACK

	jmp	.send

  .syn_ack:

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

	push	TH_ACK

  .send:

	; Store the recv.nxt field

	mov	eax, [edx + TCP_Packet.SequenceNumber]

	; Update our recv.nxt field

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

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

	inc_INET esi

	; Send an ACK

	pop	ebx

	call	TCP_send_ack

  .exit:

	ret

align 4

stateTCB_SYN_RECEIVED:

	; In this case, we are expecting an ACK Packet

	; For now, if the Packet is an ACK, process it,

	; If not, ignore it

	test	[edx + TCP_Packet.Flags], TH_RST

	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.TCBState], TCB_LISTEN

	jmp	.exit

  .check_ack:

	; Look at control flags - expecting an ACK

	test	[edx + TCP_Packet.Flags], TH_ACK

	jz	.exit

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

  .exit:

	ret

align 4

stateTCB_ESTABLISHED:

	; Here we are expecting data, or a request to close

	; OR both...

	; Did we receive a FIN or RST?

	test	[edx + TCP_Packet.Flags], TH_FIN

	jz	.check_ack

	; It was a fin or reset.

	; Remove resend entries from the queue  - I dont want to send any more data

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

  .check_ack:

	; Check that we received an ACK

	test	[edx + TCP_Packet.Flags], TH_ACK

	jz	.exit

	; 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

	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

    @@: ; OK, here is the deal

	; My recv.nct field holds the seq of the expected next rec byte

	; if the recevied sequence number is not equal to this, do not

	; increment the recv.nxt field, do not copy data - just send a

	; repeat ack.

	; recv.nxt is in dword [edx+24], in inet format

	; recv seq is in [sktAddr]+56, in inet format

	; just do a comparision

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

	cmp	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.TCBState], TCB_CLOSE_WAIT

	jne	@f

	mov	ecx, eax

    @@: cmp	ecx, [edx + TCP_Packet.SequenceNumber]

	jne	.ack

	test	ecx, ecx

	jnz	.data

	; If we had received a fin, we need to ACK it.

	cmp	[ebx + SOCKET_head.end + IPv4_SOCKET.end + TCP_SOCKET.TCBState], TCB_CLOSE_WAIT

	je	.ack

	jmp	.exit

  .data:

	mov	esi, [esp + 4]

	sub	edx, esi

	mov	edi, edx

	call	socket_internal_receiver

  .ack:

	; Send an ACK

	mov	bl, TH_ACK

	call	TCP_send_ack

  .exit:

	ret

align 4

stateTCB_FIN_WAIT_1:

	; 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.TCBState], TCB_FIN_WAIT_2

	jmp	.exit

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

	cmp	al, TH_FIN

	je	@f

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

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

	inc_INET esi

	; Send an ACK

	mov	bl, TH_ACK

	call	TCP_send_ack

  .exit:

	ret

align 4

stateTCB_FIN_WAIT_2:

	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.TCBState], TCB_TIMED_WAIT

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

	inc_INET esi

	; Send an ACK

	mov	bl, TH_ACK

	call	TCP_send_ack

  .exit:

	ret

align 4

stateTCB_CLOSE_WAIT:

	; Intentionally left empty

	; socket_close_tcp handles this

	ret

align 4

stateTCB_CLOSING:

	; 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.TCBState], TCB_TIMED_WAIT

  .exit:

	ret

align 4

stateTCB_LAST_ACK:

	; Look at control flags - expecting an ACK

	test	[edx + TCP_Packet.Flags], TH_ACK

	jz	.exit

	; delete the socket

	stdcall net_socket_free, ebx

  .exit:

	ret

align 4

stateTCB_TIME_WAIT:

	ret

align 4

stateTCB_CLOSED:

	ret