emailler/ip65/tcp.s

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; TCP (transmission control protocol) functions
; NB to use these functions, you must pass "-DTCP" to ca65 when assembling "ip.s"
; otherwise inbound tcp packets won't get passed in to tcp_process
; currently only a single outbound (client) connection is supported
; to use, first call "tcp_connect" to create a connection. to send data on that connection, call "tcp_send".
; whenever data arrives, a call will be made to the routine pointed at by tcp_callback.
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MAX_TCP_PACKETS_SENT = 8 ; timeout after sending 8 messages will be about 7 seconds (1+2+3+4+5+6+7+8)/4
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.include "zeropage.inc"
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.include "../inc/common.i"
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.ifndef KPR_API_VERSION_NUMBER
.define EQU =
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.include "../inc/kipper_constants.i"
.endif
.import ip65_error
.export tcp_init
.export tcp_process
.export tcp_connect
.export tcp_callback
.export tcp_connect_ip
.export tcp_send_data_len
.export tcp_send
.export tcp_send_string
.export tcp_close
.export tcp_listen
.export tcp_send_keep_alive
.export tcp_connect_remote_port
.export tcp_remote_ip
.export tcp_state
.export tcp_inbound_data_ptr
.export tcp_inbound_data_length
.import ip_calc_cksum
.import ip_send
.import ip_create_packet
.import ip_inp
.import ip_outp
.import ip65_process
.import check_for_abort_key
.import timer_read
.import ip65_random_word
.importzp acc32
.importzp op32
.importzp acc16
.import add_32_32
.import add_16_32
.import cmp_32_32
.import cmp_16_16
.import sub_16_16
.importzp ip_cksum_ptr
.importzp ip_header_cksum
.importzp ip_src
.importzp ip_dest
.importzp ip_data
.importzp ip_proto
.importzp ip_proto_tcp
.importzp ip_id
.importzp ip_len
.import copymem
.importzp copy_src
.importzp copy_dest
.import cfg_ip
tcp_cxn_state_closed = 0
tcp_cxn_state_listening = 1 ; (waiting for an inbound SYN)
tcp_cxn_state_syn_sent = 2 ; (waiting for an inbound SYN/ACK)
tcp_cxn_state_established = 3
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; tcp packet offsets
tcp_inp = ip_inp + ip_data ; pointer to tcp packet inside inbound ethernet frame
tcp_outp = ip_outp + ip_data ; pointer to tcp packet inside outbound ethernet frame
tcp_src_port = 0 ; offset of source port field in tcp packet
tcp_dest_port = 2 ; offset of destination port field in tcp packet
tcp_seq = 4 ; offset of sequence number field in tcp packet
tcp_ack = 8 ; offset of acknowledgement field in tcp packet
tcp_header_length = 12 ; offset of header length field in tcp packet
tcp_flags_field = 13 ; offset of flags field in tcp packet
tcp_window_size = 14 ; offset of window size field in tcp packet
tcp_checksum = 16 ; offset of checksum field in tcp packet
tcp_urgent_pointer = 18 ; offset of urgent pointer field in tcp packet
tcp_data = 20 ; offset of data in tcp packet
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; virtual header
tcp_vh = tcp_outp - 12
tcp_vh_src = 0
tcp_vh_dest = 4
tcp_vh_zero = 8
tcp_vh_proto = 9
tcp_vh_len = 10
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tcp_flag_FIN = 1
tcp_flag_SYN = 2
tcp_flag_RST = 4
tcp_flag_PSH = 8
tcp_flag_ACK = 16
tcp_flag_URG = 32
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2014-04-27 16:59:58 +00:00
.bss
tcp_state: .res 1
tcp_local_port: .res 2
tcp_remote_port: .res 2
tcp_remote_ip: .res 4
tcp_sequence_number: .res 4
tcp_ack_number: .res 4
tcp_data_ptr: .res 2
tcp_data_len: .res 2
tcp_send_data_ptr: .res 2
tcp_send_data_len: .res 2 ; length (in bytes) of data to be sent over tcp connection
tcp_callback: .res 2 ; vector to routine to be called when data is received over tcp connection
tcp_flags: .res 1
tcp_fin_sent: .res 1
tcp_listen_port: .res 2
tcp_inbound_data_ptr: .res 2 ; pointer to data just recieved over tcp connection
tcp_inbound_data_length: .res 2 ; length of data just received over tcp connection
; (if this is $ffff, that means "end of file", i.e. remote end has closed connection)
tcp_connect_sequence_number: .res 4 ; the seq number we will next send out
tcp_connect_expected_ack_number: .res 4 ; what we expect to see in the next inbound ack
tcp_connect_ack_number: .res 4 ; what we will next ack
tcp_connect_last_received_seq_number: .res 4 ; the seq field in the last inbound packet for this connection
tcp_connect_last_ack: .res 4 ; ack field in the last inbound packet for this connection
tcp_connect_local_port: .res 2
tcp_connect_remote_port: .res 2
tcp_connect_ip: .res 4 ; ip address of remote server to connect to
tcp_timer: .res 1
tcp_loop_count: .res 1
tcp_packet_sent_count: .res 1
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.code
; initialize tcp
; called automatically by ip_init if "ip.s" was compiled with -DTCP
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; inputs: none
; outputs: none
tcp_init:
rts
jmp_to_callback:
jmp (tcp_callback)
; listen for an inbound tcp connection
; this is a 'blocking' call, i.e. it will not return until a connection has been made
; inputs:
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; AX: destination port (2 bytes)
; tcp_callback: vector to call when data arrives on this connection
; outputs:
; carry flag is set if an error occured, clear otherwise
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tcp_listen:
stax tcp_listen_port
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lda #tcp_cxn_state_listening
sta tcp_state
lda #0 ; reset the "packet sent" counter
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sta tcp_packet_sent_count
sta tcp_fin_sent
; set the low word of seq number to $0000, high word to something random
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sta tcp_connect_sequence_number
sta tcp_connect_sequence_number+1
jsr ip65_random_word
stax tcp_connect_sequence_number+2
jsr set_expected_ack; ; due to various ugly hacks, the 'expected ack' value is now what is put into the 'SEQ' field in outbound packets
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@listen_loop:
jsr ip65_process
jsr check_for_abort_key
bcc @no_abort
lda #KPR_ERROR_ABORTED_BY_USER
sta ip65_error
rts
@no_abort:
lda #tcp_cxn_state_listening
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cmp tcp_state
beq @listen_loop
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jmp tcp_connection_established
rts
; make outbound tcp connection
; inputs:
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; tcp_connect_ip: destination ip address (4 bytes)
; AX: destination port (2 bytes)
; tcp_callback: vector to call when data arrives on this connection
; outputs:
; carry flag is set if an error occured, clear otherwise
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tcp_connect:
stax tcp_connect_remote_port
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jsr ip65_random_word
stax tcp_connect_local_port
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lda #tcp_cxn_state_syn_sent
sta tcp_state
lda #0 ; reset the "packet sent" counter
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sta tcp_packet_sent_count
sta tcp_fin_sent
; set the low word of seq number to $0000, high word to something random
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sta tcp_connect_sequence_number
sta tcp_connect_sequence_number+1
jsr ip65_random_word
stax tcp_connect_sequence_number+2
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@tcp_polling_loop:
; create a SYN packet
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lda #tcp_flag_SYN
sta tcp_flags
lda #0
sta tcp_data_len
sta tcp_data_len+1
ldx #3
: lda tcp_connect_ip,x
sta tcp_remote_ip,x
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lda tcp_connect_sequence_number,x
sta tcp_sequence_number,x
dex
bpl :-
ldax tcp_connect_local_port
stax tcp_local_port
ldax tcp_connect_remote_port
stax tcp_remote_port
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jsr tcp_send_packet
lda tcp_packet_sent_count
adc #1
sta tcp_loop_count ; we wait a bit longer between each resend
@outer_delay_loop:
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jsr timer_read
stx tcp_timer ; we only care about the high byte
@inner_delay_loop:
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jsr ip65_process
jsr check_for_abort_key
bcc @no_abort
lda #KPR_ERROR_ABORTED_BY_USER
sta ip65_error
rts
@no_abort:
lda tcp_state
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cmp #tcp_cxn_state_syn_sent
bne @got_a_response
jsr timer_read
cpx tcp_timer ; this will tick over after about 1/4 of a second
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beq @inner_delay_loop
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dec tcp_loop_count
bne @outer_delay_loop
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inc tcp_packet_sent_count
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lda tcp_packet_sent_count
cmp #MAX_TCP_PACKETS_SENT-1
bpl @too_many_messages_sent
jmp @tcp_polling_loop
@too_many_messages_sent:
@failed:
lda #tcp_cxn_state_closed
sta tcp_state
lda #KPR_ERROR_TIMEOUT_ON_RECEIVE
sta ip65_error
sec ; signal an error
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rts
@got_a_response:
lda tcp_state
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cmp #tcp_cxn_state_closed
bne @was_accepted
sec ; if we got here, then the other side sent a RST or FIN, so signal an error to the caller
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rts
@was_accepted:
tcp_connection_established:
; inc the sequence number to cover the SYN we have sent
ldax #tcp_connect_sequence_number
stax acc32
ldax #$01
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jsr add_16_32
set_expected_ack:
; set the expected ack number with current seq number
ldx #3
: lda tcp_connect_sequence_number,x
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sta tcp_connect_expected_ack_number,x
dex
bpl :-
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clc
rts
tcp_close:
; close the current connection
; inputs:
; none
; outputs:
; carry flag is set if an error occured, clear otherwise
lda tcp_state
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cmp #tcp_cxn_state_established
beq :+
@connection_closed:
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lda #tcp_cxn_state_closed
sta tcp_state
clc
rts
: ; increment the expected sequence number for the SYN we are about to send
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ldax #tcp_connect_expected_ack_number
stax acc32
ldax #1
sta tcp_fin_sent
jsr add_16_32
@send_fin_loop:
lda #tcp_flag_FIN+tcp_flag_ACK
sta tcp_flags
ldax #0
stax tcp_data_len
ldx #3
: lda tcp_connect_ip,x
sta tcp_remote_ip,x
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lda tcp_connect_ack_number,x
sta tcp_ack_number,x
lda tcp_connect_sequence_number,x
sta tcp_sequence_number,x
dex
bpl :-
ldax tcp_connect_local_port
stax tcp_local_port
ldax tcp_connect_remote_port
stax tcp_remote_port
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jsr tcp_send_packet
lda tcp_packet_sent_count
adc #1
sta tcp_loop_count ; we wait a bit longer between each resend
@outer_delay_loop:
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jsr timer_read
stx tcp_timer ; we only care about the high byte
@inner_delay_loop:
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jsr ip65_process
lda tcp_state
cmp #tcp_cxn_state_established
bne @connection_closed
jsr timer_read
cpx tcp_timer ; this will tick over after about 1/4 of a second
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beq @inner_delay_loop
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dec tcp_loop_count
bne @outer_delay_loop
inc tcp_packet_sent_count
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lda tcp_packet_sent_count
cmp #MAX_TCP_PACKETS_SENT-1
bpl @too_many_messages_sent
jmp @send_fin_loop
@too_many_messages_sent:
@failed:
lda #tcp_cxn_state_closed
sta tcp_state
lda #KPR_ERROR_TIMEOUT_ON_RECEIVE
sta ip65_error
sec ; signal an error
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rts
; send a string over the current tcp connection
; inputs:
; tcp connection should already be opened
; AX: pointer to buffer - data up to (but not including)
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; the first nul byte will be sent. max of 255 bytes will be sent.
; outputs:
; carry flag is set if an error occured, clear otherwise
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tcp_send_string:
stax tcp_send_data_ptr
stax ptr1
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lda #0
tay
sta tcp_send_data_len
sta tcp_send_data_len+1
lda (ptr1),y
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bne @find_end_of_string
rts ; if the string is empty, don't send anything!
@find_end_of_string:
lda (ptr1),y
beq @done
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inc tcp_send_data_len
iny
bne @find_end_of_string
@done:
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ldax tcp_send_data_ptr
; now we can fall through into tcp_send
; send tcp data
; inputs:
; tcp connection should already be opened
; tcp_send_data_len: length of data to send (exclusive of any headers)
; AX: pointer to buffer containing data to be sent
; outputs:
; carry flag is set if an error occured, clear otherwise
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tcp_send:
stax tcp_send_data_ptr
lda tcp_state
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cmp #tcp_cxn_state_established
beq @connection_established
lda #KPR_ERROR_CONNECTION_CLOSED
sta ip65_error
sec
rts
lda #0 ; reset the "packet sent" counter
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sta tcp_packet_sent_count
@connection_established:
; increment the expected sequence number
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ldax #tcp_connect_expected_ack_number
stax acc32
ldax tcp_send_data_len
jsr add_16_32
@tcp_polling_loop:
; create a data packet
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lda #tcp_flag_ACK+tcp_flag_PSH
sta tcp_flags
ldax tcp_send_data_len
stax tcp_data_len
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ldax tcp_send_data_ptr
stax tcp_data_ptr
ldx #3
: lda tcp_connect_ip,x
sta tcp_remote_ip,x
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lda tcp_connect_sequence_number,x
sta tcp_sequence_number,x
dex
bpl :-
ldax tcp_connect_local_port
stax tcp_local_port
ldax tcp_connect_remote_port
stax tcp_remote_port
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jsr tcp_send_packet
lda tcp_packet_sent_count
adc #1
sta tcp_loop_count ; we wait a bit longer between each resend
@outer_delay_loop:
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jsr timer_read
stx tcp_timer ; we only care about the high byte
@inner_delay_loop:
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jsr ip65_process
jsr check_for_abort_key
bcc @no_abort
lda #KPR_ERROR_ABORTED_BY_USER
sta ip65_error
lda #tcp_cxn_state_closed
sta tcp_state
rts
@no_abort:
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ldax #tcp_connect_last_ack
stax acc32
ldax #tcp_connect_expected_ack_number
stax op32
jsr cmp_32_32
beq @got_ack
jsr timer_read
cpx tcp_timer ; this will tick over after about 1/4 of a second
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beq @inner_delay_loop
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dec tcp_loop_count
bne @outer_delay_loop
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inc tcp_packet_sent_count
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lda tcp_packet_sent_count
cmp #MAX_TCP_PACKETS_SENT-1
bpl @too_many_messages_sent
jmp @tcp_polling_loop
@too_many_messages_sent:
@failed:
lda #tcp_cxn_state_closed
sta tcp_state
lda #KPR_ERROR_TIMEOUT_ON_RECEIVE
sta ip65_error
sec ; signal an error
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rts
@got_ack:
; finished - now we need to advance the sequence number for the data we just sent
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ldax #tcp_connect_sequence_number
stax acc32
ldax tcp_send_data_len
jsr add_16_32
clc
rts
; send a single tcp packet
; inputs:
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; tcp_remote_ip: IP address of destination server
; tcp_remote_port: destination tcp port
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; tcp_local_port: source tcp port
; tcp_flags: 6 bit flags
; tcp_data_ptr: pointer to data to include in this packet
; tcp_data_len: length of data pointed at by tcp_data_ptr
; outputs:
; carry flag is set if an error occured, clear otherwise
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tcp_send_packet:
ldax tcp_data_ptr
stax copy_src ; copy data to output buffer
ldax #tcp_outp + tcp_data
stax copy_dest
ldax tcp_data_len
jsr copymem
ldx #3 ; copy virtual header addresses
: lda tcp_remote_ip,x
sta tcp_vh + tcp_vh_dest,x ; set virtual header destination
lda cfg_ip,x
sta tcp_vh + tcp_vh_src,x ; set virtual header source
dex
bpl :-
lda tcp_local_port ; copy source port
sta tcp_outp + tcp_src_port + 1
lda tcp_local_port + 1
sta tcp_outp + tcp_src_port
lda tcp_remote_port ; copy destination port
sta tcp_outp + tcp_dest_port + 1
lda tcp_remote_port + 1
sta tcp_outp + tcp_dest_port
ldx #3 ; copy sequence and ack (if ACK flag set) numbers (in reverse order)
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ldy #0
: lda tcp_sequence_number,x
sta tcp_outp + tcp_seq,y
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lda #tcp_flag_ACK
bit tcp_flags
bne @ack_set
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lda #0
beq @sta_ack
@ack_set:
lda tcp_ack_number,x
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@sta_ack:
sta tcp_outp + tcp_ack,y
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iny
dex
bpl :-
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lda #$50 ; 4 bit header length in 32bit words + 4 bits of zero
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sta tcp_outp+tcp_header_length
lda tcp_flags
sta tcp_outp+tcp_flags_field
lda #ip_proto_tcp
sta tcp_vh + tcp_vh_proto
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ldax #$0010 ; $1000 in network byte order
stax tcp_outp+tcp_window_size
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lda #0 ; clear checksum
sta tcp_outp + tcp_checksum
sta tcp_outp + tcp_checksum + 1
sta tcp_vh + tcp_vh_zero ; clear virtual header zero byte
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ldax #tcp_vh ; checksum pointer to virtual header
stax ip_cksum_ptr
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lda tcp_data_len ; copy length + 20
clc
adc #20
sta tcp_vh + tcp_vh_len + 1 ; lsb for virtual header
tay
lda tcp_data_len + 1
adc #0
sta tcp_vh + tcp_vh_len ; msb for virtual header
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tax ; length to A/X
tya
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clc ; add 12 bytes for virtual header
adc #12
bcc :+
inx
: jsr ip_calc_cksum ; calculate checksum
stax tcp_outp + tcp_checksum
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ldx #3 ; copy addresses
: lda tcp_remote_ip,x
sta ip_outp + ip_dest,x ; set ip destination address
dex
bpl :-
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jsr ip_create_packet ; create ip packet template
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lda tcp_data_len ; ip len = tcp data length + 20 byte ip header + 20 byte tcp header
ldx tcp_data_len + 1
clc
adc #40
bcc :+
inx
: sta ip_outp + ip_len + 1 ; set length
stx ip_outp + ip_len
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ldax #$1234 ; set ID
stax ip_outp + ip_id
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lda #ip_proto_tcp ; set protocol
sta ip_outp + ip_proto
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jmp ip_send ; send packet, sec on error
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; see if the ip packet we just got is for a valid (non-closed) tcp connection
; inputs:
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; eth_inp: should contain an ethernet frame encapsulating an inbound tcp packet
; outputs:
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; carry flag clear if inbound tcp packet part of existing connection
check_current_connection:
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lda tcp_state
cmp #tcp_cxn_state_closed
bne @connection_not_closed
sec
rts
@connection_not_closed:
ldax #ip_inp+ip_src
stax acc32
ldax #tcp_connect_ip
stax op32
jsr cmp_32_32
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beq @remote_ip_matches
sec
rts
@remote_ip_matches:
ldax tcp_inp+tcp_src_port
stax acc16
lda tcp_connect_remote_port+1 ; this value in reverse byte order to how it is presented in the TCP header
ldx tcp_connect_remote_port
jsr cmp_16_16
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beq @remote_port_matches
sec
rts
@remote_port_matches:
ldax tcp_inp+tcp_dest_port
stax acc16
lda tcp_connect_local_port+1 ; this value in reverse byte order to how it is presented in the TCP header
ldx tcp_connect_local_port
jsr cmp_16_16
beq @local_port_matches
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sec
rts
@local_port_matches:
clc
rts
; process incoming tcp packet
; called automatically by ip_process if "ip.s" was compiled with -DTCP
; inputs:
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; eth_inp: should contain an ethernet frame encapsulating an inbound tcp packet
; outputs:
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; none but if connection was found, an outbound message may be created, overwriting eth_outp
; also tcp_state and other tcp variables may be modified
tcp_process:
lda #tcp_flag_RST
bit tcp_inp+tcp_flags_field
beq @not_reset
jsr check_current_connection
bcs @not_current_connection_on_rst
; for some reason, search.twitter.com is sending RSTs with ID=$1234 (i.e. echoing the inbound ID)
; but then keeps the connection open and ends up sending the file.
; so lets ignore a reset with ID=$1234
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lda ip_inp+ip_id
cmp #$34
bne @not_invalid_reset
lda ip_inp+ip_id+1
cmp #$12
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bne @not_invalid_reset
jmp @send_ack
@not_invalid_reset:
; connection has been reset so mark it as closed
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lda #tcp_cxn_state_closed
sta tcp_state
lda #KPR_ERROR_CONNECTION_RESET_BY_PEER
sta ip65_error
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lda #$ff
sta tcp_inbound_data_length
sta tcp_inbound_data_length+1
jsr jmp_to_callback ; let the caller see the connection has closed
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@not_current_connection_on_rst:
; if we get a reset for a closed or nonexistent connection, then ignore it
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rts
@not_reset:
lda tcp_inp+tcp_flags_field
cmp #tcp_flag_SYN+tcp_flag_ACK
bne @not_syn_ack
; it's a SYN/ACK
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jsr check_current_connection
bcc @current_connection_on_syn_ack
; if we get a SYN/ACK for something that aint the connection we're expecting,
; terminate with extreme prejudice
jmp @send_rst
@current_connection_on_syn_ack:
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lda tcp_state
cmp #tcp_cxn_state_syn_sent
bne @not_expecting_syn_ack
; this IS the syn/ack we are waiting for :-)
ldx #3 ; copy sequence number to ack (in reverse order)
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ldy #0
: lda tcp_inp + tcp_seq,y
sta tcp_connect_ack_number,x
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iny
dex
bpl :-
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ldax #tcp_connect_ack_number
stax acc32
ldax #$0001
jsr add_16_32 ; increment the ACK counter by 1, for the SYN we just received
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lda #tcp_cxn_state_established
sta tcp_state
@not_expecting_syn_ack:
; we get a SYN/ACK for the current connection,
; but we're not expecting it, it's probably
; a retransmist - just ACK it
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jmp @send_ack
@not_syn_ack:
; is it an ACK - alone or with PSH/URGENT but not a SYN/ACK?
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lda #tcp_flag_ACK
bit tcp_inp+tcp_flags_field
bne @ack
jmp @not_ack
@ack:
; is this the current connection?
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jsr check_current_connection
bcc @current_connection_on_ack
; if we get an ACK for something that is not the current connection
; we should send a RST
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jmp @send_rst
@current_connection_on_ack:
; if it's an ACK, then record the last ACK (reorder the bytes in the process)
ldx #3 ; copy seq & ack fields (in reverse order)
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ldy #0
: lda tcp_inp + tcp_ack,y
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sta tcp_connect_last_ack,x
lda tcp_inp + tcp_seq,y
sta tcp_connect_last_received_seq_number,x
iny
dex
bpl :-
; was this the next sequence number we're waiting for?
ldax #tcp_connect_ack_number
stax acc32
ldax #tcp_connect_last_received_seq_number
stax op32
jsr cmp_32_32
bne @not_expected_seq_number
; what is the size of data in this packet?
lda ip_inp+ip_len+1 ; payload length (lo byte)
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sta acc16
lda ip_inp+ip_len ; payload length (hi byte)
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sta acc16+1
lda tcp_inp+tcp_header_length ; high 4 bits is header length in 32 bit words
lsr ; A=A/2
lsr ; A=A/2
clc ; A now equal to tcp header length in bytes
adc #20 ; add 20 bytes for IP header, this gives length of IP +TCP headers
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ldx #0
sta tcp_header_length
jsr sub_16_16
; acc16 now contains the length of data in this TCP packet
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lda acc16
sta tcp_inbound_data_length
lda acc16+1
sta tcp_inbound_data_length+1
bne @not_empty_packet
lda acc16
bne @not_empty_packet
jmp @empty_packet
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@not_empty_packet:
; calculate ptr to tcp data
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clc
lda tcp_header_length
adc #<ip_inp
sta tcp_inbound_data_ptr
lda #>ip_inp
adc #0
sta tcp_inbound_data_ptr+1
; do a callback
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jsr jmp_to_callback
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; move ack ptr along
ldax #tcp_connect_ack_number
stax acc32
ldax tcp_inbound_data_length
jsr add_16_32
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; send an ACK with the sequence number we expect
@not_expected_seq_number:
; send the ACK for any data in this packet, then return to check for FIN flag
jsr @send_ack
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@not_ack:
@empty_packet:
; is it a FIN?
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lda #tcp_flag_FIN
bit tcp_inp+tcp_flags_field
bne @fin
jmp @not_fin
@fin:
; is this the current connection?
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jsr check_current_connection
bcc :+
jmp @send_rst ; reset if not current connection
: ldx #3 ; copy seq field (in reverse order)
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ldy #0
: lda tcp_inp + tcp_seq,y
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sta tcp_connect_last_received_seq_number,x
iny
dex
bpl :-
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; was this the next sequence number we're waiting for?
ldax #tcp_connect_ack_number
stax acc32
ldax #tcp_connect_last_received_seq_number
stax op32
jsr cmp_32_32
beq :+
rts ; bail if not expected sequence number
: ; set the length to $ffff
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lda #$ff
sta tcp_inbound_data_length
sta tcp_inbound_data_length+1
jsr jmp_to_callback ; let the caller see the connection has closed
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lda #tcp_cxn_state_closed
sta tcp_state
; send a FIN/ACK
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; move ack ptr along for the inbound FIN
ldax #tcp_connect_ack_number
stax acc32
ldax #$01
sta tcp_fin_sent
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jsr add_16_32
; if we've already sent a FIN then just send back an ACK
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lda tcp_fin_sent
beq @send_fin_ack
; if we get here, we've sent a FIN, and just received an inbound FIN.
; when we sent the fin, we didn't update the sequence number, since
; we want to use the old sequence on every resend of that FIN
; now that our fin has been ACKed, we need to inc the sequence number
; and then send another ACK.
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ldax #tcp_connect_sequence_number
stax acc32
ldax #$0001
jsr add_16_32 ; increment the SEQ counter by 1, for the FIN we have been sending
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lda #tcp_flag_ACK
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jmp @send_packet
@send_fin_ack:
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lda #tcp_flag_FIN+tcp_flag_ACK
jmp @send_packet
@not_fin:
lda tcp_inp+tcp_flags_field
cmp #tcp_flag_SYN
beq @syn
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jmp @not_syn
@syn:
; is this the port we are listening on?
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lda tcp_inp+tcp_dest_port+1
cmp tcp_listen_port
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bne @decline_syn_with_reset
lda tcp_inp+tcp_dest_port
cmp tcp_listen_port+1
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bne @decline_syn_with_reset
; it's the right port - are we actually waiting for a connecting?
lda #tcp_cxn_state_listening
cmp tcp_state
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beq @this_is_connection_we_are_waiting_for
; is this the current connection? that would mean our ACK got lost, so resend
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jsr check_current_connection
bcc @this_is_connection_we_are_waiting_for
rts ; if we've currently got a connection open, then ignore any new requests
; the sender will timeout and resend the SYN, by which time we may be
; ready to accept it again.
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@this_is_connection_we_are_waiting_for:
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; copy sequence number to ack (in reverse order) and remote IP
ldx #3
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ldy #0
: lda tcp_inp + tcp_seq,y
sta tcp_connect_ack_number,x
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lda ip_inp+ip_src,x
sta tcp_connect_ip,x
iny
dex
bpl :-
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; copy ports
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ldax tcp_listen_port
stax tcp_connect_local_port
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lda tcp_inp+tcp_src_port+1
sta tcp_connect_remote_port
lda tcp_inp+tcp_src_port
sta tcp_connect_remote_port+1
lda #tcp_cxn_state_established
sta tcp_state
ldax #tcp_connect_ack_number
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stax acc32
ldax #$0001
jsr add_16_32 ; increment the ACK counter by 1, for the SYN we just received
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lda #tcp_flag_SYN+tcp_flag_ACK
jmp @send_packet
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@decline_syn_with_reset:
; create a RST packet
ldx #3 ; copy sequence number to ack (in reverse order)
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ldy #0
: lda tcp_inp + tcp_seq,y
sta tcp_ack_number,x
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iny
dex
bpl :-
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ldax #tcp_ack_number
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stax acc32
ldax #$0001
jsr add_16_32 ; increment the ACK counter by 1, for the SYN we just received
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@send_rst:
lda #tcp_flag_RST+tcp_flag_ACK
sta tcp_flags
ldax #0
stax tcp_data_len
ldx #3
: lda ip_inp+ip_src,x
sta tcp_remote_ip,x
dex
bpl :-
; copy src/dest ports in inverted byte order
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lda tcp_inp+tcp_src_port
sta tcp_remote_port+1
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lda tcp_inp+tcp_src_port+1
sta tcp_remote_port
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lda tcp_inp+tcp_dest_port
sta tcp_local_port+1
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lda tcp_inp+tcp_dest_port+1
sta tcp_local_port
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jsr tcp_send_packet
@not_syn:
rts
@send_ack:
; create an ACK packet
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lda #tcp_flag_ACK
@send_packet:
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sta tcp_flags
ldax #0
stax tcp_data_len
ldx #3
: lda tcp_connect_ip,x
sta tcp_remote_ip,x
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lda tcp_connect_ack_number,x
sta tcp_ack_number,x
; if we have just sent a packet out, we may not yet have updated tcp_connect_sequence_number yet
; so use current value of tcp_connect_expected_ack_number as outbound sequence number instead
lda tcp_connect_expected_ack_number,x
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sta tcp_sequence_number,x
dex
bpl :-
ldax tcp_connect_local_port
stax tcp_local_port
ldax tcp_connect_remote_port
stax tcp_remote_port
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jmp tcp_send_packet
; send an empty ACK packet on the current connection
; inputs:
; none
; outputs:
; carry flag is set if an error occured, clear otherwise
tcp_send_keep_alive = @send_ack
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; -- LICENSE FOR tcp.s --
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; The contents of this file are subject to the Mozilla Public License
; Version 1.1 (the "License"); you may not use this file except in
; compliance with the License. You may obtain a copy of the License at
; http://www.mozilla.org/MPL/
;
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; Software distributed under the License is distributed on an "AS IS"
; basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
; License for the specific language governing rights and limitations
; under the License.
;
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; The Original Code is ip65.
;
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; The Initial Developer of the Original Code is Jonno Downes,
; jonno@jamtronix.com.
; Portions created by the Initial Developer are Copyright (C) 2009
; Jonno Downes. All Rights Reserved.
2013-12-13 21:24:03 +00:00
; -- LICENSE END --