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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/arp.s</h1><pre> ARP address resolution
</pre><h2 id="functions">functions</h2><table><tr><th>function</th><th>description</th></tr><tr><td id="arp_add">arp_add</td><td><pre> add arp_mac and arp_ip to the cache
inputs:
arp_ip is ip address to add to cache
arp_mac is corresponding mac address of specified ip
outputs:
arp_cache is updated </pre></td></tr><tr><td id="arp_calculate_gateway_mask">arp_calculate_gateway_mask</td><td></td></tr><tr><td id="arp_init">arp_init</td><td><pre>initialize arp (including clearing the arp cache)
inputs: none
outputs: none </pre></td></tr><tr><td id="arp_lookup">arp_lookup</td><td><pre>lookup the mac address for an ip
inputs: arp_ip should be set to ip address to be resolved
outputs:
if carry flag is clear, then arp_mac will be set to correct mac address
if carry flag is set, then the correct mac address could not be found in
the arp cache, so an arp request was sent. so the caller should wait a while
(to allow time for an arp response message to arrive) and then call arp_lookup again. </pre></td></tr><tr><td id="arp_process">arp_process</td><td><pre>handle incoming arp packets
inputs: eth_inp should contain an arp packet
outputs:
carry flag is set if there was an error processing the arp packet, clear otherwise
the arp_cache will be updated with the mac &amp; ip address (whether the inbound
message was a request or a response). if the incoming packet was an arp
request for this machine, then an arp response will be created (overwriting
eth_outp) and sent out </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="arp_cache">arp_cache</td><td>cache of IP addresses and corresponding MAC addresses </td><td>(6+4)*ac_size</td></tr><tr><td id="arp_ip">arp_ip</td><td> set arp_ip before calling arp_lookup </td><td>4</td></tr><tr><td id="arp_mac">arp_mac</td><td> result is delivered here when arp_lookup returns with carry flag clear </td><td>6</td></tr></table><h2 id="constants">constants</h2><table><tr><th>constants</th><th>description</th><th>value</th></tr><tr><td id="ac_size">ac_size</td><td> lookup cache </td><td>8 </td></tr></table><h2>implementation</h2><pre id="code">; ARP address resolution
.include "../inc/common.i"
.export arp_init
.export arp_lookup
.export arp_process
.export arp_add
.export arp_calculate_gateway_mask
.export arp_ip
.export arp_mac
.export arp_cache
.exportzp ac_size
.import eth_inp
.import eth_inp_len
.import eth_outp
.import eth_outp_len
.import eth_tx
.import eth_set_broadcast_dest
.import eth_set_my_mac_src
.import eth_set_proto
.importzp eth_proto_arp
.import cfg_mac
.import cfg_ip
.import cfg_netmask
.import cfg_gateway
.import timer_read
.import timer_timeout
.segment "IP65ZP" : zeropage
ap: .res 2
ARP_TIMEOUT_MS=100
.bss
; arp state machine
arp_idle = 1 ; idling
arp_wait = 2 ; waiting for reply
arp_state: .res 1 ; current activity
; arguments for lookup and add
arp: ; ptr to mac/ip pair
arp_mac: .res 6 ; result is delivered here when arp_lookup returns with carry flag clear
arp_ip: .res 4 ; set arp_ip before calling arp_lookup
; arp cache
ac_size = 8 ; lookup cache
ac_ip = 6 ; offset for ip
ac_mac = 0 ; offset for mac
arp_cache: .res (6+4)*ac_size ;cache of IP addresses and corresponding MAC addresses
; offsets for arp packet generation
ap_hw = 14 ; hw type (eth = 0001)
ap_proto = 16 ; protocol (ip = 0800)
ap_hwlen = 18 ; hw addr len (eth = 06)
ap_protolen = 19 ; proto addr len (ip = 04)
ap_op = 20 ; request = 0001, reply = 0002
ap_shw = 22 ; sender hw addr
ap_sp = 28 ; sender proto addr
ap_thw = 32 ; target hw addr
ap_tp = 38 ; target protoaddr
ap_packlen = 42 ; total length of packet
; gateway handling
gw_mask: .res 4 ; inverted netmask
gw_test: .res 4 ; gateway ip or:d with inverted netmask
gw_last: .res 1 ; netmask length - 1
; timeout
arptimeout: .res 2 ; time when we will have timed out
.code
;initialize arp (including clearing the arp cache)
;inputs: none
;outputs: none
arp_init:
lda #0
ldx #(6+4)*ac_size - 1 ; clear cache
:
sta arp_cache,x
dex
bpl :-
arp_calculate_gateway_mask:
lda #$ff ; counter for netmask length - 1
sta gw_last
ldx #3
@gw:
lda cfg_netmask,x
eor #$ff
cmp #$ff
bne :+
inc gw_last
: sta gw_mask,x
ora cfg_gateway,x
sta gw_test,x
dex
bpl @gw
lda #arp_idle ; start out idle
sta arp_state
rts
;lookup the mac address for an ip
;inputs: arp_ip should be set to ip address to be resolved
;outputs:
; if carry flag is clear, then arp_mac will be set to correct mac address
; if carry flag is set, then the correct mac address could not be found in
; the arp cache, so an arp request was sent. so the caller should wait a while
; (to allow time for an arp response message to arrive) and then call arp_lookup again.
arp_lookup:
lda arp_ip ; check for broadcast IP (255.255.255.255)
and arp_ip + 1
and arp_ip + 2
and arp_ip + 3
cmp #$ff
bne @notbroadcast
ldx #6 ;copy ff:ff:ff:ff:ff:ff to ap_mac
: sta arp_mac,x
dex
bpl :-
clc
rts
@notbroadcast:
ldx gw_last ; check if address is on our subnet
: lda arp_ip,x
ora gw_mask,x
cmp gw_test,x
bne @notlocal
dex
bpl :-
bmi @local
@notlocal:
ldx #3 ; copy gateway's ip address
: lda cfg_gateway,x
sta arp_ip,x
dex
bpl :-
@local:
jsr findip
bcs @cachemiss
ldy #ac_ip - 1 ; copy mac
: lda (ap),y
sta arp,y
dey
bpl :-
rts
@cachemiss:
lda arp_state ; are we already waiting for a reply?
cmp #arp_idle
beq @sendrequest ; yes, send request
ldax arptimeout ; check if we've timed out
jsr timer_timeout
bcs @notimeout ; no, don't send
@sendrequest: ; send out arp request
jsr eth_set_broadcast_dest
jsr eth_set_my_mac_src
jsr makearppacket ; add arp, eth, ip, hwlen, protolen
lda #0 ; set opcode (request = 0001)
sta eth_outp + ap_op
lda #1
sta eth_outp + ap_op + 1
ldx #5
: lda cfg_mac,x ; set source mac addr
sta eth_outp + ap_shw,x
lda #0 ; set target mac addr
sta eth_outp + ap_thw,x
dex
bpl :-
ldx #3
: lda cfg_ip,x ; set source ip addr
sta eth_outp + ap_sp,x
lda arp_ip,x ; set target ip addr
sta eth_outp + ap_tp,x
dex
bpl :-
lda #<ap_packlen ; set packet length
sta eth_outp_len
lda #>ap_packlen
sta eth_outp_len + 1
jsr eth_tx ; send packet
lda #arp_wait ; waiting for reply
sta arp_state
jsr timer_read ; read current timer value
clc
adc #<ARP_TIMEOUT_MS ; set timeout to now + ARP_TIMEOUT_MS
sta arptimeout
txa
adc #>ARP_TIMEOUT_MS
sta arptimeout + 1
@notimeout:
sec ; set carry to indicate that
rts ; no result is availble
; find arp_ip in the cache
; clc returns pointer to entry in (ap)
findip:
ldax #arp_cache
stax ap
ldx #ac_size
@compare: ; compare cache entry
ldy #ac_ip
lda (ap),y
beq @notfound
: lda (ap),y
cmp arp,y
bne @next
iny
cpy #ac_ip + 4
bne :-
clc ; return
rts
@next: ; next entry
lda ap
clc
adc #10
sta ap
bcc :+
inc ap + 1
: dex
bne @compare
@notfound:
sec
rts
;handle incoming arp packets
;inputs: eth_inp should contain an arp packet
;outputs:
; carry flag is set if there was an error processing the arp packet, clear otherwise
; the arp_cache will be updated with the mac & ip address (whether the inbound
; message was a request or a response). if the incoming packet was an arp
; request for this machine, then an arp response will be created (overwriting
; eth_outp) and sent out
arp_process:
lda eth_inp + ap_op ; should be 0
bne @badpacket
lda eth_inp + ap_op + 1 ; check opcode
cmp #1 ; request?
beq @request
cmp #2 ; reply?
beq @reply
@badpacket:
sec
rts
@request:
ldx #3
: lda eth_inp + ap_tp,x ; check if they're asking for
cmp cfg_ip,x ; my address
bne @done
dex
bpl :-
ldax #eth_inp + ap_shw
jsr ac_add_source ; add them to arp cache
ldx #5 ; send reply
: lda eth_inp + ap_shw,x
sta eth_outp,x ; set sender packet dest
sta eth_outp + ap_thw,x ; and as target
lda cfg_mac,x ; me as source
sta eth_outp + ap_shw,x
dex
bpl :-
jsr eth_set_my_mac_src ; me as packet source
jsr makearppacket ; add arp, eth, ip, hwlen, protolen
lda #0 ; set opcode (reply = 0002)
sta eth_outp + ap_op
lda #2
sta eth_outp + ap_op + 1
ldx #3
: lda eth_inp + ap_sp,x ; sender as target addr
sta eth_outp + ap_tp,x
lda cfg_ip,x ; my ip as source addr
sta eth_outp + ap_sp,x
dex
bpl :-
lda #<ap_packlen ; set packet length
sta eth_outp_len
lda #>ap_packlen
sta eth_outp_len + 1
jsr eth_tx ; send packet
@done:
clc
rts
@reply:
lda arp_state
cmp #arp_wait ; are we waiting for a reply?
bne @badpacket
ldax #eth_inp + ap_shw
jsr ac_add_source ; add to cache
lda #arp_idle
sta arp_state
rts
; add arp_mac and arp_ip to the cache
;inputs:
; arp_ip is ip address to add to cache
; arp_mac is corresponding mac address of specified ip
;outputs:
; arp_cache is updated
arp_add:
jsr findip ; check if ip is already in cache
bcs @add
ldy #9 ; update old entry
: lda arp,y ; move to top as well?
sta (ap),y
dey
bpl :-
rts
@add:
ldax #arp ; add
;add source to cache
ac_add_source:
stax ap
ldx #9 ; make space in the arp cache
:
lda arp_cache + 60,x
sta arp_cache + 70,x
lda arp_cache + 50,x
sta arp_cache + 60,x
lda arp_cache + 40,x
sta arp_cache + 50,x
lda arp_cache + 30,x
sta arp_cache + 40,x
lda arp_cache + 20,x
sta arp_cache + 30,x
lda arp_cache + 10,x
sta arp_cache + 20,x
lda arp_cache,x
sta arp_cache + 10,x
dex
bpl :-
ldy #9
: lda (ap),y ; copy source
sta arp_cache,y
dey
bpl :-
rts
; adds proto = arp, hw = eth, and proto = ip to outgoing packet
makearppacket:
lda #eth_proto_arp
jsr eth_set_proto
lda #0 ; set hw type (eth = 0001)
sta eth_outp + ap_hw
lda #1
sta eth_outp + ap_hw + 1
lda #8 ; set protcol (ip = 0800)
sta eth_outp + ap_proto
lda #0
sta eth_outp + ap_proto + 1
lda #6 ; set hw addr len (eth = 06)
sta eth_outp + ap_hwlen
lda #4 ; set proto addr len (eth = 04)
sta eth_outp + ap_protolen
rts
;-- LICENSE FOR arp.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 Per Olofsson,
; MagerValp@gmail.com.
; Portions created by the Initial Developer are Copyright (C) 2009
; Per Olofsson. All Rights Reserved.
; -- LICENSE END --
</pre></body></html>