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<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"/><link rel="stylesheet" type="text/css" href="ca65-doc-style.css"/></head><body><a href="ref_index.html"><h1>ip65 technical reference</h1></a><h1>File : ip65/tcp.s</h1><pre>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.
</pre><h2 id="functions">functions</h2><table><tr><th>function</th><th>description</th></tr><tr><td id="tcp_close">tcp_close</td><td><pre/></td></tr><tr><td id="tcp_connect">tcp_connect</td><td><pre>make outbound tcp connection
inputs:
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
</pre></td></tr><tr><td id="tcp_init">tcp_init</td><td><pre> initialize tcp
called automatically by ip_init if "ip.s" was compiled with -DTCP
inputs: none
outputs: none
</pre></td></tr><tr><td id="tcp_listen">tcp_listen</td><td><pre>listen for an inbound tcp connection
this is a 'blocking' call, i.e. it will not return until a connection has been made
inputs:
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
</pre></td></tr><tr><td id="tcp_process">tcp_process</td><td><pre>process incoming tcp packet
called automatically by ip_process if "ip.s" was compiled with -DTCP
inputs:
eth_inp: should contain an ethernet frame encapsulating an inbound tcp packet
outputs:
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
</pre></td></tr><tr><td id="tcp_send">tcp_send</td><td><pre>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
</pre></td></tr><tr><td id="tcp_send_keep_alive">tcp_send_keep_alive</td><td><pre>send an empty ACK packet on the current connection
inputs:
none
outputs:
carry flag is set if an error occured, clear otherwise
</pre></td></tr><tr><td id="tcp_send_string">tcp_send_string</td><td><pre>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)
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
</pre></td></tr></table><h2 id="variables">variables</h2><table><tr><th>variable</th><th>description</th><th>size (bytes)</th></tr><tr><td id="tcp_callback">tcp_callback</td><td>vector to routine to be called when data is received over tcp connection
</td><td>2</td></tr><tr><td id="tcp_connect_ip">tcp_connect_ip</td><td>ip address of remote server to connect to
</td><td>4</td></tr><tr><td id="tcp_connect_remote_port">tcp_connect_remote_port</td><td></td><td>2</td></tr><tr><td id="tcp_inbound_data_length">tcp_inbound_data_length</td><td>length of data just received over tcp connection
</td><td>2</td></tr><tr><td id="tcp_inbound_data_ptr">tcp_inbound_data_ptr</td><td>pointer to data just recieved over tcp connection
</td><td>2</td></tr><tr><td id="tcp_send_data_len">tcp_send_data_len</td><td>length (in bytes) of data to be sent over tcp connection
</td><td>2</td></tr><tr><td id="tcp_state">tcp_state</td><td></td><td>1</td></tr></table><h2 id="constants">constants</h2><table><tr><th>constants</th><th>description</th><th>value</th></tr><tr><td id="tcp_remote_ip">tcp_remote_ip</td><td></td><td></td></tr></table><h2>implementation</h2><pre id="code">;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.
MAX_TCP_PACKETS_SENT=8 ;timeout after sending 8 messages will be about 7 seconds (1+2+3+4+5+6+7+8)/4
.include "../inc/common.i"
.ifndef KPR_API_VERSION_NUMBER
.define EQU =
.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 ;
; 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
; 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
;
tcp_flag_FIN =1
tcp_flag_SYN =2
tcp_flag_RST =4
tcp_flag_PSH =8
tcp_flag_ACK =16
tcp_flag_URG =32
.segment "TCP_VARS"
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
.code
; initialize tcp
;called automatically by ip_init if "ip.s" was compiled with -DTCP
; 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:
; 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
tcp_listen:
stax tcp_listen_port
lda #tcp_cxn_state_listening
sta tcp_state
lda #0 ;reset the "packet sent" counter
sta tcp_packet_sent_count
sta tcp_fin_sent
;set the low word of seq number to $0000, high word to something random
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
@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
cmp tcp_state
beq @listen_loop
jmp tcp_connection_established
rts
;make outbound tcp connection
;inputs:
; 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
tcp_connect:
stax tcp_connect_remote_port
jsr ip65_random_word
stax tcp_connect_local_port
lda #tcp_cxn_state_syn_sent
sta tcp_state
lda #0 ;reset the "packet sent" counter
sta tcp_packet_sent_count
sta tcp_fin_sent
;set the low word of seq number to $0000, high word to something random
sta tcp_connect_sequence_number
sta tcp_connect_sequence_number+1
jsr ip65_random_word
stax tcp_connect_sequence_number+2
@tcp_polling_loop:
;create a SYN packet
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
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
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:
jsr timer_read
stx tcp_timer ;we only care about the high byte
@inner_delay_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_state
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
beq @inner_delay_loop
dec tcp_loop_count
bne @outer_delay_loop
inc tcp_packet_sent_count
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
rts
@got_a_response:
lda tcp_state
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
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
jsr add_16_32
set_expected_ack:
;set the expected ack number with current seq number
ldx #3 ;
: lda tcp_connect_sequence_number,x
sta tcp_connect_expected_ack_number,x
dex
bpl :-
clc
rts
tcp_close:
;close the current connection
;inputs:
; none
;outputs:
; carry flag is set if an error occured, clear otherwise
lda tcp_state
cmp #tcp_cxn_state_established
beq :+
@connection_closed:
lda #tcp_cxn_state_closed
sta tcp_state
clc
rts
:
;increment the expected sequence number for the SYN we are about to send
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
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
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:
jsr timer_read
stx tcp_timer ;we only care about the high byte
@inner_delay_loop:
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
beq @inner_delay_loop
dec tcp_loop_count
bne @outer_delay_loop
inc tcp_packet_sent_count
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
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)
; 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
tcp_send_string:
stax tcp_send_data_ptr
stax copy_src
lda #0
tay
sta tcp_send_data_len
sta tcp_send_data_len+1
lda (copy_src),y
bne @find_end_of_string
rts ; if the string is empty, don't send anything!
@find_end_of_string:
lda (copy_src),y
beq @done
inc tcp_send_data_len
iny
bne @find_end_of_string
@done:
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
tcp_send:
stax tcp_send_data_ptr
lda tcp_state
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
sta tcp_packet_sent_count
@connection_established:
;increment the expected sequence number
ldax #tcp_connect_expected_ack_number
stax acc32
ldax tcp_send_data_len
jsr add_16_32
@tcp_polling_loop:
;create a data packet
lda #tcp_flag_ACK+tcp_flag_PSH
sta tcp_flags
ldax tcp_send_data_len
stax tcp_data_len
ldax tcp_send_data_ptr
stax tcp_data_ptr
ldx #3 ;
: lda tcp_connect_ip,x
sta tcp_remote_ip,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
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:
jsr timer_read
stx tcp_timer ;we only care about the high byte
@inner_delay_loop:
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:
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
beq @inner_delay_loop
dec tcp_loop_count
bne @outer_delay_loop
inc tcp_packet_sent_count
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
rts
@got_ack:
;finished - now we need to advance the sequence number for the data we just sent
ldax #tcp_connect_sequence_number
stax acc32
ldax tcp_send_data_len
jsr add_16_32
clc
rts
;send a single tcp packet
;inputs:
; tcp_remote_ip: IP address of destination server
; tcp_remote_port: destination tcp port
; 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
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)
ldy #0
: lda tcp_sequence_number,x
sta tcp_outp + tcp_seq,y
lda #tcp_flag_ACK
bit tcp_flags
bne @ack_set
lda #0
beq @sta_ack
@ack_set:
lda tcp_ack_number,x
@sta_ack:
sta tcp_outp + tcp_ack,y
iny
dex
bpl :-
lda #$50 ;4 bit header length in 32bit words + 4 bits of zero
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
ldax #$0010 ;$1000 in network byte order
stax tcp_outp+tcp_window_size
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
ldax #tcp_vh ; checksum pointer to virtual header
stax ip_cksum_ptr
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
tax ; length to A/X
tya
clc ; add 12 bytes for virtual header
adc #12
bcc :+
inx
:
jsr ip_calc_cksum ; calculate checksum
stax tcp_outp + tcp_checksum
ldx #3 ; copy addresses
: lda tcp_remote_ip,x
sta ip_outp + ip_dest,x ; set ip destination address
dex
bpl :-
jsr ip_create_packet ; create ip packet template
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
ldax #$1234 ; set ID
stax ip_outp + ip_id
lda #ip_proto_tcp ; set protocol
sta ip_outp + ip_proto
jmp ip_send ; send packet, sec on error
check_current_connection:
;see if the ip packet we just got is for a valid (non-closed) tcp connection
;inputs:
; eth_inp: should contain an ethernet frame encapsulating an inbound tcp packet
;outputs:
; carry flag clear if inbound tcp packet part of existing connection
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
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
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
sec
rts
@local_port_matches:
clc
rts
;process incoming tcp packet
;called automatically by ip_process if "ip.s" was compiled with -DTCP
;inputs:
; eth_inp: should contain an ethernet frame encapsulating an inbound tcp packet
;outputs:
; 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
lda ip_inp+ip_id
cmp #$34
bne @not_invalid_reset
lda ip_inp+ip_id+1
cmp #$12
bne @not_invalid_reset
jmp @send_ack
@not_invalid_reset:
;connection has been reset so mark it as closed
lda #tcp_cxn_state_closed
sta tcp_state
lda #KPR_ERROR_CONNECTION_RESET_BY_PEER
sta ip65_error
lda #$ff
sta tcp_inbound_data_length
sta tcp_inbound_data_length+1
jsr jmp_to_callback ;let the caller see the connection has closed
@not_current_connection_on_rst:
;if we get a reset for a closed or nonexistent connection, then ignore it
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
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:
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)
ldy #0
: lda tcp_inp + tcp_seq,y
sta tcp_connect_ack_number,x
iny
dex
bpl :-
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
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
jmp @send_ack
@not_syn_ack:
;is it an ACK - alone or with PSH/URGENT but not a SYN/ACK?
lda #tcp_flag_ACK
bit tcp_inp+tcp_flags_field
bne @ack
jmp @not_ack
@ack:
;is this the current connection?
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
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)
ldy #0
: lda tcp_inp + tcp_ack,y
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)
sta acc16
lda ip_inp+ip_len ;payload length (hi byte)
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
ldx #0
sta tcp_header_length
jsr sub_16_16
;acc16 now contains the length of data in this TCP packet
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
@not_empty_packet:
;calculate ptr to tcp data
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
jsr jmp_to_callback
; move ack ptr along
ldax #tcp_connect_ack_number
stax acc32
ldax tcp_inbound_data_length
jsr add_16_32
@not_expected_seq_number: ;send an ACK with the sequence number we expect
;send the ACK for any data in this packet, then return to check for FIN flag
jsr @send_ack
@not_ack:
@empty_packet:
;is it a FIN?
lda #tcp_flag_FIN
bit tcp_inp+tcp_flags_field
bne @fin
jmp @not_fin
@fin:
;is this the current connection?
jsr check_current_connection
bcc :+
jmp @send_rst ;reset if not current connection
:
ldx #3 ; copy seq field (in reverse order)
ldy #0
: 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
beq :+
rts ;bail if not expected sequence number
:
;set the length to $ffff
lda #$ff
sta tcp_inbound_data_length
sta tcp_inbound_data_length+1
jsr jmp_to_callback ;let the caller see the connection has closed
lda #tcp_cxn_state_closed
sta tcp_state
;send a FIN/ACK
; move ack ptr along for the inbound FIN
ldax #tcp_connect_ack_number
stax acc32
ldax #$01
sta tcp_fin_sent
jsr add_16_32
;if we've already sent a FIN then just send back an ACK
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.
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
lda #tcp_flag_ACK
jmp @send_packet
@send_fin_ack:
lda #tcp_flag_FIN+tcp_flag_ACK
jmp @send_packet
@not_fin:
lda tcp_inp+tcp_flags_field
cmp #tcp_flag_SYN
beq @syn
jmp @not_syn
@syn:
;is this the port we are listening on?
lda tcp_inp+tcp_dest_port+1
cmp tcp_listen_port
bne @decline_syn_with_reset
lda tcp_inp+tcp_dest_port
cmp tcp_listen_port+1
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
beq @this_is_connection_we_are_waiting_for
;is this the current connection? that would mean our ACK got lost, so resend
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.
@this_is_connection_we_are_waiting_for:
; copy sequence number to ack (in reverse order) and remote IP
ldx #3
ldy #0
: lda tcp_inp + tcp_seq,y
sta tcp_connect_ack_number,x
lda ip_inp+ip_src,x
sta tcp_connect_ip,x
iny
dex
bpl :-
;copy ports
ldax tcp_listen_port
stax tcp_connect_local_port
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
stax acc32
ldax #$0001 ;
jsr add_16_32 ;increment the ACK counter by 1, for the SYN we just received
lda #tcp_flag_SYN+tcp_flag_ACK
jmp @send_packet
@decline_syn_with_reset:
;create a RST packet
ldx #3 ; copy sequence number to ack (in reverse order)
ldy #0
: lda tcp_inp + tcp_seq,y
sta tcp_ack_number,x
iny
dex
bpl :-
ldax #tcp_ack_number
stax acc32
ldax #$0001 ;
jsr add_16_32 ;increment the ACK counter by 1, for the SYN we just received
@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
lda tcp_inp+tcp_src_port
sta tcp_remote_port+1
lda tcp_inp+tcp_src_port+1
sta tcp_remote_port
lda tcp_inp+tcp_dest_port
sta tcp_local_port+1
lda tcp_inp+tcp_dest_port+1
sta tcp_local_port
jsr tcp_send_packet
rts
@not_syn:
rts
@send_ack:
;create an ACK packet
lda #tcp_flag_ACK
@send_packet:
sta tcp_flags
ldax #0
stax tcp_data_len
ldx #3 ;
: lda tcp_connect_ip,x
sta tcp_remote_ip,x
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
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
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
;-- LICENSE FOR tcp.s --
; 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/
;
; 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.
;
; The Original Code is ip65.
;
; 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.
; -- LICENSE END --
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