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

;

; TCP_output

;

; IN:  eax = socket pointer

;

; OUT: /

;

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

align 4

TCP_output:

	DEBUGF 1,"TCP_output, socket: %x\n", eax

; We'll detect the length of the data to be transmitted, and flags to be used

; If there is some data, or any critical controls to send (SYN / RST), then transmit

; Otherwise, investigate further

	mov	ebx, [eax + TCP_SOCKET.SND_MAX]

	cmp	ebx, [eax + TCP_SOCKET.SND_UNA]

	jne	.not_idle

	mov	ebx, [eax + TCP_SOCKET.t_idle]

	cmp	ebx, [eax + TCP_SOCKET.t_rxtcur]

	jle	.not_idle

; We have been idle for a while and no ACKS are expected to clock out any data we send..

; Slow start to get ack "clock" running again.

	mov	ebx, [eax + TCP_SOCKET.t_maxseg]

	mov	[eax + TCP_SOCKET.SND_CWND], ebx

  .not_idle:

  .again:

	mov	ebx, [eax + TCP_SOCKET.SND_NXT] 	; calculate offset (71)

	sub	ebx, [eax + TCP_SOCKET.SND_UNA] 	;

	mov	ecx, [eax + TCP_SOCKET.SND_WND] 	; determine window

	cmp	ecx, [eax + TCP_SOCKET.SND_CWND]	;

	jl	@f					;

	mov	ecx, [eax + TCP_SOCKET.SND_CWND]	;

       @@:						;

	call	TCP_outflags				; flags in dl

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

; data being forced out ?

; If in persist timeout with window of 0, send 1 byte.

; Otherwise, if window is small but nonzero, and timer expired,

; we will send what we can and go to transmit state

	test	[eax + TCP_SOCKET.t_force], -1

	jz	.no_force

	test	ecx, ecx

	jnz	.no_zero_window

	cmp	ebx, [eax + STREAM_SOCKET.snd + RING_BUFFER.size]

	jge	@f

	and	dl, not (TH_FIN)	  ; clear the FIN flag    ??? how can it be set before?

       @@:

	inc	ecx

	jmp	.no_force

  .no_zero_window:

	mov	[eax + TCP_SOCKET.timer_persist], 0

	mov	[eax + TCP_SOCKET.t_rxtshift], 0

  .no_force:

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

; Calculate how much data to send (106)

	mov	esi, [eax + STREAM_SOCKET.snd + RING_BUFFER.size]

	cmp	esi, ecx

	jl	@f

	mov	esi, ecx

       @@:

	sub	esi, ebx

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

; check for window shrink (107)

; If FIN has been set, but not ACKed, but we havent been called to retransmit, esi will be -1

; Otherwise, window shrank after we sent into it.

	jns	.not_negative

; enter persist state

	xor	esi, esi

; If window shrank to 0

	test	ecx, ecx

	jnz	@f

; cancel pending retransmit

	mov	[eax + TCP_SOCKET.timer_retransmission], 0

; pull SND_NXT back to (closed) window, We will enter persist state below.

	push	[eax + TCP_SOCKET.SND_UNA]

	pop	[eax + TCP_SOCKET.SND_NXT]

       @@:

; If window didn't close completely, just wait for an ACK

  .not_negative:

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

; Send one segment at a time (124)

	cmp	esi, [eax + TCP_SOCKET.t_maxseg]

	jle	@f

	mov	esi, [eax + TCP_SOCKET.t_maxseg]

;;; sendalot = 1

       @@:

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

; Turn of FIN flag if send buffer not emptied (128)

	mov	edi, [eax + TCP_SOCKET.SND_NXT]

	add	edi, esi

	sub	edi, [eax + TCP_SOCKET.SND_UNA]

	sub	edi, [eax + STREAM_SOCKET.snd + RING_BUFFER.size]

	jns	@f

	and	dl, not (TH_FIN)

       @@:

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

; calculate window advertisement (130)

	mov	ecx, SOCKET_MAXDATA

	sub	ecx, [eax + STREAM_SOCKET.rcv + RING_BUFFER.size]

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

; Sender silly window avoidance (131)

	test	esi, esi

	jz	.len_zero

	cmp	esi, [eax + TCP_SOCKET.t_maxseg]

	je	.send

;;; if (idle or TF_NODELAY) && (esi + ebx >= so_snd.sb_cc), send

	test	[eax + TCP_SOCKET.t_force], -1	;;;

	jnz	.send

	mov	ebx, [eax + TCP_SOCKET.max_sndwnd]

	shr	ebx, 1

	cmp	esi, ebx

	jge	.send

	mov	ebx, [eax + TCP_SOCKET.SND_NXT]

	cmp	ebx, [eax + TCP_SOCKET.SND_MAX]

	jl	.send

  .len_zero:

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

; Check if a window update should be sent (154)

	test	ecx, ecx

	jz	.no_window

;;; TODO 167-172

  .no_window:

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

; Should a segment be sent? (174)

	test	[eax + TCP_SOCKET.t_flags], TF_ACKNOW	; we need to ACK

	jnz	.send

	test	dl, TH_SYN + TH_RST			; we need to send a SYN or RST

	jnz	.send

	mov	ebx, [eax + TCP_SOCKET.SND_UP]		; when urgent pointer is beyond start of send bufer

	cmp	ebx, [eax + TCP_SOCKET.SND_UNA]

	jg	.send

	test	dl, TH_FIN

	jz	.enter_persist	; no reason to send, enter persist state

; FIN was set, only send if not already sent, or on retransmit

	test	[eax + TCP_SOCKET.t_flags], TF_SENTFIN

	jnz	.send

	mov	ebx, [eax + TCP_SOCKET.SND_NXT]

	cmp	ebx, [eax + TCP_SOCKET.SND_UNA]

	je	.send

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

; Enter persist state (191)

  .enter_persist:

	DEBUGF	1,"Entering persist state\n"

;;; 213 - 217

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

; No reason to send a segment (219)

	DEBUGF	1,"No reason to send a segment\n"

	mov	[eax + SOCKET.lock], 0

	ret

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

;

; Send a segment (222)

;

; eax = socket pointer

; esi = data len

;  dl = flags

;

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

  .send:

	DEBUGF	1,"Preparing to send a segment\n"

	mov	edi, TCP_segment.Data	; edi will contain headersize

	sub	esp, 8			; create some space on stack

	push	eax			; save socket pointer

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

; Send options with first SYN segment

	test	dl, TH_SYN

	jz	.options_done

	push	[eax + TCP_SOCKET.ISS]

	pop	[eax + TCP_SOCKET.SND_NXT]

	test	[eax + TCP_SOCKET.t_flags], TF_NOOPT

	jnz	.options_done

	mov	ecx, 1460

	or	ecx, TCP_OPT_MAXSEG shl 24 + 4 shl 16

	bswap	ecx

	push	ecx

	add	di, 4

	test	[eax + TCP_SOCKET.t_flags], TF_REQ_SCALE

	jz	.no_syn

	test	dl, TH_ACK

	jnz	.scale_opt

	test	[eax + TCP_SOCKET.t_flags], TF_RCVD_SCALE

	jz	.no_syn

  .scale_opt:

	movzx	ecx, byte [eax + TCP_SOCKET.request_r_scale]

	or	ecx, TCP_OPT_WINDOW shl 24 + 4 shl 16 + TCP_OPT_NOP shl 8

	bswap	ecx

	pushd	ecx

	add	di, 4

  .no_syn:

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

; Make the timestamp option if needed

	test	[eax + TCP_SOCKET.t_flags], TF_REQ_TSTMP

	jz	.no_timestamp

	test	dl, TH_RST

	jnz	.no_timestamp

	test	dl, TH_ACK

	jz	.timestamp

	test	[eax + TCP_SOCKET.t_flags], TF_RCVD_TSTMP

	jz	.no_timestamp

  .timestamp:

	mov	ebx, [timer_ticks]

	bswap	ebx

	push	ebx

	pushw	0

	pushd	TCP_OPT_TIMESTAMP + 10 shl 8 + TCP_OPT_NOP shl 16 + TCP_OPT_NOP shl 24

	add	di, 10

  .no_timestamp:

	; 

  .options_done:

; eax = socket ptr

; edx = flags

; edi = header size

; esi = data len

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

; check if we dont exceed the max segment size (270)

	add	esi, edi			; total TCP segment size

	cmp	esi, [eax + TCP_SOCKET.t_maxseg]

	jle	.no_overflow

	mov	esi, [eax + TCP_SOCKET.t_maxseg]

;;; sendalot = 1

  .no_overflow:

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

; Start by pushing all TCP header values in reverse order on stack

; (essentially, creating the tcp header on the stack!)

	pushw	0	;        .UrgentPointer          dw ?

	pushw	0	;        .Checksum               dw ?

	pushw	0x00a0	;        .Window                 dw ?    ;;;;;;;

	shl	edi, 2	;        .DataOffset             db ?  only 4 left-most bits

	shl	dx, 8

	or	dx, di	;        .Flags                  db ?

	pushw	dx

	shr	edi, 2	;        .DataOffset             db ? ;;;;

	push	[eax + TCP_SOCKET.RCV_NXT]	;        .AckNumber              dd ?

	ntohd	[esp]

	push	[eax + TCP_SOCKET.SND_NXT]	;        .SequenceNumber         dd ?

	ntohd	[esp]

	push	[eax + TCP_SOCKET.RemotePort]	;        .DestinationPort        dw ?

	ntohw	[esp]

	push	[eax + TCP_SOCKET.LocalPort]	;        .SourcePort             dw ?

	ntohw	[esp]

	push	edi		; header size

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

; Create the IP packet

	mov	ecx, esi

	mov	ebx, [eax + IP_SOCKET.LocalIP]	; source ip

	mov	eax, [eax + IP_SOCKET.RemoteIP] ; dest ip

	mov	di, IP_PROTO_TCP shl 8 + 128

	call	IPv4_output

	jz	.fail

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

; Move TCP header from stack to TCP packet

	push	ecx

	mov	ecx, [esp+4]

	lea	esi, [esp+4+4]

	shr	ecx, 2

	rep	movsd

	pop	ecx		; full TCP packet size

	pop	esi		; headersize

	add	esp, esi

	mov	[esp + 4], eax		; packet ptr

	mov	[esp + 4+4], edx	; packet size

	mov	edx, edi		; begin of data

	sub	edx, esi		; begin of packet (edi = begin of data)

	push	ecx

	sub	ecx, esi		; data size

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

; Copy the data

; eax = ptr to ring struct

; ecx = buffer size

; edi = ptr to buffer

	mov	eax, [esp+4]			; get socket ptr

	add	[eax + TCP_SOCKET.SND_NXT], ecx ; update sequence number

	add	eax, STREAM_SOCKET.snd

	push	edx

	call	SOCKET_ring_read

	pop	esi				; begin of data

	pop	ecx				; full packet size

	pop	eax				; socket ptr

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

; update sequence number and timers  (400)

	test	[esi + TCP_segment.Flags], TH_SYN + TH_FIN

	jz	@f

	inc	[eax + TCP_SOCKET.SND_NXT]	; syn and fin take a sequence number

	test	[esi + TCP_segment.Flags], TH_FIN

	jz	@f

	or	[eax + TCP_SOCKET.t_flags], TF_SENTFIN	; if we sent a fin, set the sentfin flag

       @@:

	mov	edx, [eax + TCP_SOCKET.SND_NXT]

	cmp	edx, [eax + TCP_SOCKET.SND_MAX]

	jle	@f

	mov	[eax + TCP_SOCKET.SND_MAX], edx

	;;;; TODO: time transmission (420)

       @@:

; set retransmission timer if not already set, and not doing an ACK or keepalive probe

	cmp	[eax + TCP_SOCKET.timer_retransmission], 1000 ;;;;

	jl	.retransmit_set

	cmp	edx, [eax + TCP_SOCKET.SND_UNA] 	; edx = [eax + TCP_SOCKET.SND_NXT]

	je	.retransmit_set

	mov	edx, [eax + TCP_SOCKET.t_rxtcur]

	mov	[eax + TCP_SOCKET.timer_retransmission], dx

	mov	[eax + TCP_SOCKET.timer_persist], 0

	mov	[eax + TCP_SOCKET.t_rxtshift], 0	;;; TODO: only do this if timer_persist was set

  .retransmit_set:

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

; Create the checksum

	DEBUGF	1,"checksum: ptr=%x size=%u\n", esi, ecx

	TCP_checksum (eax + IP_SOCKET.LocalIP), (eax + IP_SOCKET.RemoteIP)

	mov	[esi+TCP_segment.Checksum], dx

; unlock socket

	mov	[eax + SOCKET.lock], 0

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

; Send the packet

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

	call	[ebx + NET_DEVICE.transmit]

	ret

  .fail:

	pop	ecx

	add	esp, ecx

	add	esp, 4+8

	mov	[eax + SOCKET.lock], 0

	DEBUGF 1,"TCP_output: failed\n"

	ret