Subversion Repositories Kolibri OS

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

;;                                                              ;;

;; Copyright (C) KolibriOS team 2004-2007. All rights reserved. ;;

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

;;                                                              ;;

;;  TCP.INC                                                     ;;

;;                                                              ;;

;;  TCP Processes for Menuet OS  TCP/IP stack                   ;;

;;                                                              ;;

;;  Version 0.6  4th July 2004                                  ;;

;;                                                              ;;

;;  Copyright 2002 Mike Hibbett, mikeh@oceanfree.net            ;;

;;                                                              ;;

;;  See file COPYING for details                                ;;

;;  v0.6 : Added reset handling in the established state        ;;

;;         Added a timer per socket to allow delays when        ;;

;;         rx window gets below 1KB                             ;;

;;                                                              ;;

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

$Revision: 914 $

; TCP TCB states

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	= 0x01

TH_SYN	= 0x02

TH_RST	= 0x04

TH_PUSH = 0x08

TH_ACK	= 0x10

TH_URG	= 0x20

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 x hs

;*******************************************************************

;   Interface

;

;       tcp_tx_handler      Handles the TCP transmit queue

;       tcp_rx              The protocol handler for received data

;       buildTCPPacket      fills in the packet headers and data

;       tcpStateMachine     Main state machine for received TCP packets

;       tcp_tcb_handler     1s timer, to erase tcb's in TIME_WAIT state

;

;*******************************************************************

;   TCP Payload ( Data field in IP datagram )

;

;    0                   1                   2                   3

;    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

;   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

;20 |          Source Port          |       Destination Port        |

;   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

;24 |                        Sequence Number                        |

;   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

;28 |                    Acknowledgment Number                      |

;   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

;32 |  Data |           |U|A|P|R|S|F|                               |

;   | Offset| Reserved  |R|C|S|S|Y|I|            Window             |

;   |       |           |G|K|H|T|N|N|                               |

;   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

;36 |           Checksum            |         Urgent Pointer        |

;   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

;40 |                    Options                    |    Padding    |

;   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

;   |                             data

struc TCP_PACKET

{  .SourcePort       dw  ?  ;+00

   .DestinationPort  dw  ?  ;+02

   .SequenceNumber   dd  ?  ;+04

   .AckNumber        dd  ?  ;+08

   .DataOffset       db  ?  ;+12 - DataOffset[0-3 bits] and Reserved[4-7]

   .Flags            db  ?  ;+13 - Reserved[0-1 bits]|URG|ACK|PSH|RST|SYN|FIN

   .Window           dw  ?  ;+14

   .Checksum         dw  ?  ;+16

   .UrgentPointer    dw  ?  ;+18

   .Options          rb  3  ;+20

   .Padding          db  ?  ;+23

   .Data             db  ?  ;+24

}

virtual at 0

  TCP_PACKET TCP_PACKET

end virtual

;***************************************************************************

;   Function

;      tcp_tcb_handler

;

;   Description

;       Handles sockets in the timewait state, closing them

;       when the TCB timer expires

;

;***************************************************************************

proc tcp_tcb_handler stdcall uses ebx

    ; scan through all the sockets, decrementing active timers

	mov	ebx, net_sockets

	cmp	[ebx + SOCKET.NextPtr], 0

	je	.exit

	DEBUGF	1, "K : sockets:\n"

  .next_socket:

	mov	ebx, [ebx + SOCKET.NextPtr]

	or	ebx, ebx

	jz	.exit

	DEBUGF	1, "K :   %x: %x-%x-%x-%u\n", ebx, [ebx + SOCKET.LocalPort]:4, [ebx + SOCKET.RemoteIP], [ebx + SOCKET.RemotePort]:4, [ebx + SOCKET.TCBState]

	cmp	[ebx + SOCKET.TCBTimer], 0

	jne	.decrement_tcb

	cmp	[ebx + 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.TCBTimer]

	jnz	.next_socket

	cmp	[ebx + SOCKET.TCBState], TCB_TIMED_WAIT

	jne	.next_socket

	push	[ebx + SOCKET.PrevPtr]

	stdcall net_socket_free, ebx

	pop	ebx

	jmp	.next_socket

  .decrement_wnd:

    ; TODO - prove it works!

	dec	[ebx + SOCKET.wndsizeTimer]

	jmp	.next_socket

  .exit:

    ret

endp

;***************************************************************************

;   Function

;      tcp_tx_handler

;

;   Description

;       Handles queued TCP data

;       This is a kernel function, called by stack_handler

;

;***************************************************************************

proc tcp_tx_handler stdcall

    ; decrement all resend buffers timers. If they

    ; expire, queue them for sending, and restart the timer.

    ; If the retries counter reach 0, delete the entry

    mov     esi, resendQ

    mov     ecx, 0

  .next_resendq:

    cmp     ecx, NUMRESENDENTRIES

	je	.exit		    ; None left

	;cmp     [esi], byte 0xFF                                    ; XTODO: 0xff -> 0

	cmp	dword[esi + 4], 0

	jne	@f		     ; found one

    inc     ecx

	add	esi, 8

	jmp	.next_resendq

    @@: ; we have one. decrement it's timer by 1

	dec	word[esi + 2]

	jz	@f

    inc     ecx

	add	esi, 8

	jmp	.next_resendq	    ; Timer not zero, so move on

    @@:

	;mov     bl, 0xff                                             ; XTODO: bl -> ebx, 0xff -> 0

	xor	ebx, ebx

    ; restart timer, and decrement retries

    ; After the first resend, back of on next, by a factor of 5

	mov	[esi + 2], word TCP_TIMEOUT * 5

	dec	byte[esi + 1]

	jnz	@f

    ; retries now 0, so delete from queue

	;xchg     [esi], bl                                          ; XTODO: bl -> ebx

	xchg	 [esi + 4], ebx

    @@: ; resend packet

	pushad

    mov     eax, EMPTY_QUEUE

    call    dequeue

    cmp     ax, NO_BUFFER

	jne	.tth004z

    ; TODO - try again in 10ms.

	;cmp     bl, 0xff                                            ; XTODO: 0xff -> 0

	test	ebx, ebx

	jnz	@f

	;mov     [esi], bl                                            ; XTODO: bl -> ebx

	mov	[esi + 4], ebx

    @@: ; Mark it to expire in 10ms - 1 tick

	mov	byte[esi + 1], 1

	mov	word[esi + 2], 1

	jmp	.tth005

  .tth004z:

    ; we have a buffer # in ax

	push	eax ecx

    mov     ecx, IPBUFFSIZE

    mul     ecx

    add     eax, IPbuffs

    ; we have the buffer address in eax

    mov     edi, eax

    pop     ecx

    ; Now get buffer location, and copy buffer across. argh! more copying,,

	mov	esi, resendBuffer

    @@: add	esi, IPBUFFSIZE

	loop	@b

    ; we have resend buffer location in esi

    mov     ecx, IPBUFFSIZE

    ; copy data across

	push	edi

    cld

    rep     movsb

	pop	edi

    ; queue packet

    mov     eax, NET1OUT_QUEUE

    mov     edx, [stack_ip]

	cmp	edx, [edi + IP_PACKET.DestinationAddress]

	jne	.not_local

    mov     eax, IPIN_QUEUE

  .not_local:

    pop     ebx

    call    queue

  .tth005:

	popad

    inc     ecx

	add	esi, 8

	jmp	.next_resendq

  .exit:

    ret

endp

;***************************************************************************

;   Function

;      tcp_rx

;

;   Description

;       TCP protocol handler

;       This is a kernel function, called by ip_rx

;       IP buffer address given in edx

;          IP buffer number in eax

;          Free up (or re-use) IP buffer when finished

;

;***************************************************************************

proc tcp_rx stdcall uses ebx

    ; The process is as follows.

    ; Look for a socket with matching remote IP, remote port, local port

    ; if not found, then

    ; look for remote IP + local port match ( where sockets remote port = 0)

    ; if not found, then

    ; look for a socket where local socket port == IP packets remote port

    ; where sockets remote port, remote IP = 0

    ; discard if not found

    ; Call sockets tcbStateMachine, with pointer to packet.

    ; the state machine will not delete the packet, so do that here.

    push        eax

    ; Look for a socket where

    ; IP Packet TCP Destination Port = local Port

    ; IP Packet SA = Remote IP

    ; IP Packet TCP Source Port = remote Port

	mov	ebx, net_sockets

  .next_socket.1:

	mov	ebx, [ebx + SOCKET.NextPtr]

	or	ebx, ebx

	jz	.next_socket.1.exit

	cmp	[ebx + SOCKET.Status], SOCK_OPEN

	jne	.next_socket.1

;        DEBUGF  1, "K : tcp_rx - 1.dport: %x - %x\n", [edx + 20 + TCP_PACKET.DestinationPort]:4, [ebx + SOCKET.LocalPort]:4

	mov	ax, [edx + 20 + TCP_PACKET.DestinationPort]  ; get the dest. port from the TCP hdr

	cmp	[ebx + SOCKET.LocalPort], ax		; get the dest. port from the TCP hdr

	jne	.next_socket.1				; different - try next socket

;        DEBUGF  1, "K : tcp_rx - 1.addr: %x - %x\n", [edx + IP_PACKET.SourceAddress], [ebx + SOCKET.RemoteIP]

	mov	eax, [edx + IP_PACKET.SourceAddress]	; get the source IP Addr from the IP hdr

	cmp	[ebx + SOCKET.RemoteIP], eax		; compare with socket's remote IP

	jne	.next_socket.1				; different - try next socket

;        DEBUGF  1, "K : tcp_rx - 1.sport: %x - %x\n", [edx + 20 + TCP_PACKET.SourcePort]:4, [ebx + SOCKET.RemotePort]:4

	mov	ax, [edx + 20 + TCP_PACKET.SourcePort]	; get the source port from the TCP hdr

	cmp	[ebx + SOCKET.RemotePort], ax		; compare with socket's remote port

	jne	.next_socket.1				; different - try next socket

    ; We have a complete match - use this socket

	jmp	.change_state

  .next_socket.1.exit:

    ; If we got here, there was no match

    ; Look for a socket where

    ; IP Packet TCP Destination Port = local Port

    ; IP Packet SA = Remote IP

    ; socket remote Port = 0

	mov	ebx, net_sockets

  .next_socket.2:

	mov	ebx, [ebx + SOCKET.NextPtr]

	or	ebx, ebx

	jz	.next_socket.2.exit

	cmp	[ebx + SOCKET.Status], SOCK_OPEN

	jne	.next_socket.2

;        DEBUGF  1, "K : tcp_rx - 2.dport: %x - %x\n", [edx + 20 + TCP_PACKET.DestinationPort]:4, [ebx + SOCKET.LocalPort]:4

	mov	ax, [edx + 20 + TCP_PACKET.DestinationPort]  ; get the dest. port from the TCP hdr

	cmp	[ebx + SOCKET.LocalPort], ax		; compare with socket's local port

	jne	.next_socket.2				; different - try next socket

;        DEBUGF  1, "K : tcp_rx - 2.addr: %x - %x\n", [edx + IP_PACKET.SourceAddress], [ebx + SOCKET.RemoteIP]

	mov	eax, [edx + IP_PACKET.SourceAddress]	; get the source IP Addr from the IP hdr

	cmp	[ebx + SOCKET.RemoteIP], eax		; compare with socket's remote IP

	jne	.next_socket.2				; different - try next socket

;        DEBUGF  1, "K : tcp_rx - 2.sport: 0000 - %x\n", [ebx + SOCKET.RemotePort]:4

	cmp	[ebx + SOCKET.RemotePort], 0		; only match a remote socket of 0

	jne	.next_socket.2				; different - try next socket

    ; We have a complete match - use this socket

	jmp	.change_state

  .next_socket.2.exit:

    ; If we got here, there was no match

    ; Look for a socket where

    ; IP Packet TCP Destination Port = local Port

    ; socket Remote IP = 0

    ; socket remote Port = 0

	mov	ebx, net_sockets

  .next_socket.3:

	mov	ebx, [ebx + SOCKET.NextPtr]

	or	ebx, ebx

	jz	.next_socket.3.exit

	cmp	[ebx + SOCKET.Status], SOCK_OPEN

	jne	.next_socket.3

;        DEBUGF  1, "K : tcp_rx - 3.dport: %x - %x\n", [edx + 20 + TCP_PACKET.DestinationPort]:4, [ebx + SOCKET.LocalPort]:4

	mov	ax, [edx + 20 + TCP_PACKET.DestinationPort]  ; get destination port from the TCP hdr

	cmp	[ebx + SOCKET.LocalPort], ax		; compare with socket's local port

	jne	.next_socket.3				; different - try next socket

;        DEBUGF  1, "K : tcp_rx - 3.addr: 00000000 - %x\n", [ebx + SOCKET.RemoteIP]

	cmp	[ebx + SOCKET.RemoteIP], 0		; only match a socket remote IP of 0

	jne	.next_socket.3				; different - try next socket

;        DEBUGF  1, "K : tcp_rx - 3.sport: 0000 - %x\n", [ebx + SOCKET.RemotePort]:4

	cmp	[ebx + SOCKET.RemotePort], 0		; only match a remote socket of 0

	jne	.next_socket.3				; different - try next socket

    ; We have a complete match - use this socket

	jmp	.change_state

  .next_socket.3.exit:

    ; If we got here, we need to reject the packet

	DEBUGF	1, "K : tcp_rx - dumped\n"

	DEBUGF	1, "K :   --------: %x-%x-%x (flags: %x)\n", [edx + 20 + TCP_PACKET.DestinationPort]:4, [edx + IP_PACKET.SourceAddress], [edx + 20 + TCP_PACKET.SourcePort]:4, [edx + 20 + TCP_PACKET.Flags]:2

;       mov     ebx, net_sockets

;

; .next_socket.4:

;       mov     ebx, [ebx + SOCKET.NextPtr]

;       or      ebx, ebx

;       jz      .next_socket.4.exit

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

;       jne     .next_socket.4

;

; .next_socket.4.exit:

	inc	[dumped_rx_count]

	jmp	.exit

  .change_state:

    ; We have a valid socket/TCB, so call the TCB State Machine for that skt.

	; socket is pointed to by ebx

	; IP packet is pointed to by edx

    ; IP buffer number is on stack ( it will be popped at the end)

	stdcall tcpStateMachine, ebx

  .exit:

    pop     eax

    call    freeBuff

    ret

endp

;***************************************************************************

;   Function

;      buildTCPPacket

;

;   Description

;       builds an IP Packet with TCP data fully populated for transmission

;       You may destroy any and all registers

;          TCP control flags specified in bl

;          This TCB is in [sktAddr]

;          User data pointed to by esi

;       Data length in ecx

;          Transmit buffer number in eax

;

;***************************************************************************

proc build_tcp_packet stdcall, sockAddr:DWORD

    push    ecx                        ; Save data length

    ; convert buffer pointer eax to the absolute address

    mov     ecx, IPBUFFSIZE

    mul     ecx

    add     eax, IPbuffs

    mov     edx, eax

	mov	[edx + 20 + TCP_PACKET.Flags], bl		; TCP flags

	mov	ebx, [sockAddr]

    ; So, ebx holds the socket ptr, edx holds the IPbuffer ptr

    ; Fill in the IP header ( some data is in the socket descriptor)

	mov	eax, [ebx + SOCKET.LocalIP]

	mov	[edx + IP_PACKET.SourceAddress], eax

	mov	eax, [ebx + SOCKET.RemoteIP]

	mov	[edx + IP_PACKET.DestinationAddress], eax

	mov	[edx + IP_PACKET.VersionAndIHL], 0x45

	mov	[edx + IP_PACKET.TypeOfService], 0

    pop     eax                   ; Get the TCP data length

    push    eax

    add     eax, 20 + 20           ; add IP header and TCP header lengths

	rol	ax, 8

	mov	[edx + IP_PACKET.TotalLength], ax

	mov	[edx + IP_PACKET.Identification], 0

	mov	[edx + IP_PACKET.FlagsAndFragmentOffset], 0x0040

	mov	[edx + IP_PACKET.TimeToLive], 0x20

	mov	[edx + IP_PACKET.Protocol], PROTOCOL_TCP

    ; Checksum left unfilled

	mov	[edx + IP_PACKET.HeaderChecksum], 0

	; Fill in the TCP header (some data is in the socket descriptor)

	mov	ax, [ebx + SOCKET.LocalPort]

	mov	[edx + 20 + TCP_PACKET.SourcePort], ax		; Local Port

	mov	ax, [ebx + SOCKET.RemotePort]

	mov	[edx + 20 + TCP_PACKET.DestinationPort], ax	; desitination Port

    ; Checksum left unfilled

	mov	[edx + 20 + TCP_PACKET.Checksum], 0

    ; sequence number

	mov	eax, [ebx + SOCKET.SND_NXT]

	mov	[edx + 20 + TCP_PACKET.SequenceNumber], eax

    ; ack number

	mov	eax, [ebx + SOCKET.RCV_NXT]

	mov	[edx + 20 + TCP_PACKET.AckNumber], eax

    ; window ( 0x2000 is default ).I could accept 4KB, fa0, ( skt buffer size)

    ; 768 bytes seems better

	mov	[edx + 20 + TCP_PACKET.Window], 0x0003

    ; Urgent pointer (0)

	mov	[edx + 20 + TCP_PACKET.UrgentPointer], 0

    ; data offset ( 0x50 )

	mov	[edx + 20 + TCP_PACKET.DataOffset], 0x50

    pop     ecx                  ; count of bytes to send

    mov     ebx, ecx            ; need the length later

    cmp     ebx, 0

	jz	@f

    mov     edi, edx

    add     edi, 40

    cld

    rep     movsb               ; copy the data across

    @@: ; we have edx as IPbuffer ptr.

    ; Fill in the TCP checksum

    ; First, fill in pseudoheader

	mov	eax, [edx + IP_PACKET.SourceAddress]

    mov     [pseudoHeader], eax

	mov	eax, [edx + IP_PACKET.DestinationAddress]

	mov	[pseudoHeader + 4], eax

	mov	word[pseudoHeader + 8], PROTOCOL_TCP shl 8 + 0

    add     ebx, 20

	mov	[pseudoHeader + 10], bh

	mov	[pseudoHeader + 11], bl

    mov     eax, pseudoHeader

    mov     [checkAdd1], eax

	mov	word[checkSize1], 12

    mov     eax, edx

    add     eax, 20

    mov     [checkAdd2], eax

    mov     eax, ebx

    mov     [checkSize2], ax

    call    checksum

    ; store it in the TCP checksum ( in the correct order! )

    mov     ax, [checkResult]

	rol	ax, 8

	mov	[edx + 20 + TCP_PACKET.Checksum], ax

    ; Fill in the IP header checksum

	GET_IHL eax, edx	       ; get IP-Header length

	stdcall checksum_jb, edx, eax  ; buf_ptr, buf_size

	rol	ax, 8

	mov	[edx + IP_PACKET.HeaderChecksum], ax

    ret

endp

; Increments the 32 bit value pointed to by esi in internet order

proc inc_inet_esi stdcall

    push    eax

	mov	eax, [esi]

	bswap	eax

	inc	eax

	bswap	eax

	mov	[esi], eax

    pop     eax

    ret

endp

; Increments the 32 bit value pointed to by esi in internet order

; by the value in ecx

proc add_inet_esi stdcall

    push    eax

	mov	eax, [esi]

	bswap	eax

    add     eax, ecx

	bswap	eax

	mov	[esi], eax

    pop     eax

    ret

endp

iglobal

  TCBStateHandler dd \

    stateTCB_LISTEN, \

    stateTCB_SYN_SENT, \

    stateTCB_SYN_RECEIVED, \

    stateTCB_ESTABLISHED, \

    stateTCB_FIN_WAIT_1, \

    stateTCB_FIN_WAIT_2, \

    stateTCB_CLOSE_WAIT, \

    stateTCB_CLOSING, \

    stateTCB_LAST_ACK, \

    stateTCB_TIME_WAIT, \

    stateTCB_CLOSED

endg

;***************************************************************************

;   Function

;      tcpStateMachine

;

;   Description

;       TCP state machine

;       This is a kernel function, called by tcp_rx

;

;       IP buffer address given in edx

;          Socket/TCB address in ebx

;

;       The IP buffer will be released by the caller

;***************************************************************************

proc tcpStateMachine stdcall, sockAddr:DWORD

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

	mov	[ebx + SOCKET.TCBTimer], TWOMSL

    ; If the received packet has an ACK bit set,

    ; remove any packets in the resend queue that this

    ; received packet acknowledges

	pushad

	test	[edx + 20 + TCP_PACKET.Flags], TH_ACK

	jz	.call_handler					; No ACK, so no data yet

	; get skt number in eax

	stdcall net_socket_addr_to_num, ebx

    ; The ack number is in [edx + 28], inet format

	; skt in eax

    mov     esi, resendQ

	xor	ecx, ecx

  .next_resendq:

    cmp     ecx, NUMRESENDENTRIES

	je	.call_handler	  ; None left

	;cmp     [esi], al                                       ; XTODO: al -> eax

	cmp	[esi + 4], eax

	je	@f		  ; found one

    inc     ecx

	add	esi, 8

	jmp	.next_resendq

    @@: 		  ; Can we delete this buffer?

			  ; If yes, goto @@. No, goto .next_resendq

    ; Get packet data address

    push    ecx

    ; Now get buffer location, and copy buffer across. argh! more copying,,

	imul	edi, ecx, IPBUFFSIZE

	add	edi, resendBuffer

    ; we have dest buffer location in edi. incoming packet in edx.

    ; Get this packets sequence number

    ; preserve al, ecx, esi, edx

	mov	ecx, [edi + 20 + TCP_PACKET.SequenceNumber]

	bswap	ecx

	movzx	ebx, word[edi + 2]

	xchg	bl, bh

    sub     ebx, 40

    add     ecx, ebx          ; ecx is now seq# of last byte +1, intel format

    ; get recievd ack #, in intel format

	mov	ebx, [edx + 20 + TCP_PACKET.AckNumber]

	bswap	ebx

    cmp     ebx, ecx        ; Finally. ecx = rx'ed ack. ebx = last byte in que

                            ; DANGER! need to handle case that we have just

                            ; passed the 2**32, and wrapped round!

    pop     ecx

	jae	@f		; if rx > old, delete old

    inc     ecx

	add	esi, 8

	jmp	.next_resendq

    ;@@: mov     byte[esi], 0xff                                 ; XTODO: 0xff -> 0

    @@: mov	dword[esi + 4], 0

    inc     ecx

	add	esi, 8

	jmp	.next_resendq

  .call_handler:

	popad

	; Call handler for given TCB state

	mov	eax, [ebx + SOCKET.TCBState]

	cmp	eax, TCB_LISTEN

	jb	.exit

	cmp	eax, TCB_CLOSED

	ja	.exit

	stdcall [TCBStateHandler + (eax - 1) * 4], [sockAddr]

  .exit:

    ret

endp

proc stateTCB_LISTEN stdcall, sockAddr:DWORD

    ; 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 + 20 + TCP_PACKET.Flags], TH_SYN

	jz	.exit

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

    ; And send a response

	mov	eax, [edx + IP_PACKET.SourceAddress]

	mov	[ebx + SOCKET.RemoteIP], eax

	mov	ax, [edx + 20 + TCP_PACKET.SourcePort]

	mov	[ebx + SOCKET.RemotePort], ax

	mov	eax, [edx + 20 + TCP_PACKET.SequenceNumber]

	mov	[ebx + SOCKET.IRS], eax

	mov	[ebx + SOCKET.RCV_NXT], eax

	lea	esi, [ebx + SOCKET.RCV_NXT]

    call    inc_inet_esi ; RCV.NXT

	mov	eax, [ebx + SOCKET.ISS]

	mov	[ebx + SOCKET.SND_NXT], eax

    ; Now construct the response, and queue for sending by IP

    mov     eax, EMPTY_QUEUE

    call    dequeue

    cmp     ax, NO_BUFFER

	je	.exit

    push    eax

	mov	bl, TH_SYN + TH_ACK

	xor	ecx, ecx

	xor	esi, esi

	stdcall build_tcp_packet, [sockAddr]

    mov     eax, NET1OUT_QUEUE

    mov     edx, [stack_ip]

	mov	ecx, [sockAddr]

	cmp	edx, [ecx + SOCKET.RemoteIP]

	jne	.not_local

    mov     eax, IPIN_QUEUE

  .not_local:

       ; Send it.

    pop     ebx

    call    queue

	mov	esi, [sockAddr]

	mov	[esi + SOCKET.TCBState], TCB_SYN_RECEIVED

	; increment SND.NXT in socket

	add	esi, SOCKET.SND_NXT

    call    inc_inet_esi

  .exit:

    ret

endp

proc stateTCB_SYN_SENT stdcall, sockAddr:DWORD

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

    ; Look at control flags - expecting an ACK

	mov	al, [edx + 20 + 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.TCBState], TCB_SYN_RECEIVED

	push	TH_SYN + TH_ACK

	jmp	.send

  .syn_ack:

	mov	[ebx + SOCKET.TCBState], TCB_ESTABLISHED

	push	TH_ACK

  .send:

    ; Store the recv.nxt field

	mov	eax, [edx + 20 + TCP_PACKET.SequenceNumber]

    ; Update our recv.nxt field

	mov	[ebx + SOCKET.RCV_NXT], eax

	lea	esi, [ebx + SOCKET.RCV_NXT]

    call    inc_inet_esi

    ; Send an ACK

    ; Now construct the response, and queue for sending by IP

    mov     eax, EMPTY_QUEUE

    call    dequeue

    cmp     ax, NO_BUFFER

	pop	ebx

	je	.exit

    push    eax

	xor	ecx, ecx

	xor	esi, esi

	stdcall build_tcp_packet, [sockAddr]

    mov     eax, NET1OUT_QUEUE

    mov     edx, [stack_ip]

	mov	ecx, [sockAddr]

	cmp	edx, [ecx + SOCKET.RemoteIP]

	jne	.not_local

    mov     eax, IPIN_QUEUE

  .not_local:

       ; Send it.

    pop     ebx

    call    queue

  .exit:

    ret

endp

proc stateTCB_SYN_RECEIVED stdcall, sockAddr:DWORD

    ; 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 + 20 + TCP_PACKET.Flags], TH_RST		;xxx

	jz	.check_ack					;xxx

	push	[ebx + SOCKET.OrigRemotePort] [ebx + SOCKET.OrigRemoteIP]

	pop	[ebx + SOCKET.RemoteIP] [ebx + SOCKET.RemotePort]

	mov	[ebx + SOCKET.TCBState], TCB_LISTEN		;xxx

	jmp	.exit						;xxx

  .check_ack:							;xxx

    ; Look at control flags - expecting an ACK

	test	[edx + 20 + TCP_PACKET.Flags], TH_ACK

	jz	.exit

	mov	[ebx + SOCKET.TCBState], TCB_ESTABLISHED

  .exit:

    ret

endp

proc stateTCB_ESTABLISHED stdcall, sockAddr:DWORD

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

    ; OR both...

    ; Did we receive a FIN or RST?

;xxx    test    [edx + 20 + TCP_PACKET.Flags], TH_FIN + TH_RST

;xxx    jz      .check_ack

	test	[edx + 20 + TCP_PACKET.Flags], TH_FIN		;xxx

	jz	.check_ack					;xxx

    ; It was a fin or reset.

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

	pushad

	; get skt #

	stdcall net_socket_addr_to_num, ebx

    mov     esi, resendQ

    mov     ecx, 0

  .next_resendq:

    cmp     ecx, NUMRESENDENTRIES

	je	.last_resendq	    ; None left

	;cmp     [esi], al                                              ; XTODO: al -> eax

	cmp	[esi + 4], eax

	je	@f		    ; found one

	inc	ecx

	add	esi, 8

	jmp	.next_resendq

    ;@@: mov     byte[esi], 0xff                                         ; XTODO: 0xff -> 0

    @@: mov	dword[esi + 4], 0

    inc     ecx

	add	esi, 8

	jmp	.next_resendq

  .last_resendq:

	popad

;xxx    ; was it a reset?

;xxx    test    [edx + 20 + TCP_PACKET.Flags], TH_RST

;xxx    jz      @f

;xxx    mov     [ebx + SOCKET.TCBState], TCB_CLOSED

;xxx    jmp     .exit

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

	mov	[ebx + SOCKET.TCBState], TCB_CLOSE_WAIT

	lea	esi, [ebx + SOCKET.RCV_NXT]

    mov     eax, [esi]              ; save original

    call    inc_inet_esi

    ;; jmp    ste_ack - NO, there may be data

  .check_ack:

    ; Check that we received an ACK

	test	[edx + 20 + TCP_PACKET.Flags], TH_ACK

	jz	.exit

    ; TODO - done, I think!

    ; 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 + 20 + TCP_PACKET.Window]

	xchg	cl, ch

    cmp     cx, 1024

	ja	@f

	mov	[ebx + 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.RCV_NXT]

	cmp	[ebx + SOCKET.TCBState], TCB_CLOSE_WAIT

	jne	@f

    mov     ecx, eax

    @@: cmp	ecx, [edx + 20 + TCP_PACKET.SequenceNumber]

	jne	.ack

    ; Read the data bytes, store in socket buffer

	movzx	ecx, [edx + IP_PACKET.TotalLength]

	xchg	cl, ch

    sub     ecx, 40                    ; Discard 40 bytes of header

	jnz	.data			   ; Read data, if any

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

	cmp	[ebx + SOCKET.TCBState], TCB_CLOSE_WAIT

	je	.ack

	jmp	.exit

  .data:

    push    ecx

	add	[ebx + SOCKET.rxDataCount], ecx      ; increment the count of bytes in buffer

	mov	eax, [ebx + SOCKET.PID]       ; get socket owner PID

    push    eax

	mov	eax, [ebx + SOCKET.rxDataCount]      ; get # of bytes already in buffer

    ; point to the location to store the data

	lea	edi, [ebx + eax + SOCKETHEADERSIZE]

	sub	edi, ecx

    add     edx, 40        ; edx now points to the data

    mov     esi, edx

    cld

    rep     movsb          ; copy the data across

    ; flag an event to the application

    pop     eax

	mov	ecx, 1

	mov	esi, TASK_DATA + TASKDATA.pid

  .next_pid:

	cmp	[esi], eax

	je	.found_pid

    inc     ecx

	add	esi, 0x20

	cmp	ecx, [TASK_COUNT]

	jbe	.next_pid

  .found_pid:

	shl	ecx, 8

	or	[ecx + SLOT_BASE + APPDATA.event_mask], EVENT_NETWORK ; stack event

    pop     ecx

    ; Update our recv.nxt field

	lea	esi, [ebx + SOCKET.RCV_NXT]

    call    add_inet_esi

  .ack:

    ; Send an ACK

    ; Now construct the response, and queue for sending by IP

    mov     eax, EMPTY_QUEUE

    call    dequeue

    cmp     ax, NO_BUFFER

	je	.exit

    push    eax

	mov	bl, TH_ACK

	xor	ecx, ecx

	xor	esi, esi

	stdcall build_tcp_packet, [sockAddr]

    mov     eax, NET1OUT_QUEUE

    mov     edx, [stack_ip]

	mov	ecx, [sockAddr]

	cmp	edx, [ecx + SOCKET.RemoteIP]

	jne	.not_local

    mov     eax, IPIN_QUEUE

  .not_local:

       ; Send it.

    pop     ebx

    call    queue

  .exit:

    ret

endp

proc stateTCB_FIN_WAIT_1 stdcall, sockAddr:DWORD

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

	mov	al, [edx + 20 + TCP_PACKET.Flags]

	and	al, TH_FIN + TH_ACK

	cmp	al, TH_ACK

	jne	@f

    ; It was an ACK

	mov	[ebx + SOCKET.TCBState], TCB_FIN_WAIT_2

	jmp	.exit

    @@: mov	[ebx + SOCKET.TCBState], TCB_CLOSING

	cmp	al, TH_FIN

	je	@f

	mov	[ebx + SOCKET.TCBState], TCB_TIMED_WAIT

    @@: lea	esi, [ebx + SOCKET.RCV_NXT]

    call    inc_inet_esi