From 3a0bde75799d99fe866e3afe14a0302ffe4e66a5 Mon Sep 17 00:00:00 2001
From: Joshua Wise <joshua@rebirth.joshuawise.com>
Date: Tue, 27 May 2008 00:35:04 -0400
Subject: [PATCH] ARP responder

---
 ethernet.asm | 233 ++++++++++++++++++++++++++++-----------------------
 serial.inc   | 100 ++++++++++++++++++++++
 2 files changed, 229 insertions(+), 104 deletions(-)
 create mode 100644 serial.inc

diff --git a/ethernet.asm b/ethernet.asm
index 85d66e1..5e49ef6 100644
--- a/ethernet.asm
+++ b/ethernet.asm
@@ -1,35 +1,10 @@
+	INCLUDE "serial.inc"
+
 ETH_STATUS EQU $FF68
 ETH_DATA EQU $FF69
+ARP_ENTRIES EQU 6
+ARP_ENTRY_SIZE EQU 13
 
-PUTC: MACRO
-	ld a, \1
-	call putc
-	ENDM
-
-PUTS: MACRO
-	ld hl, \1
-	call puts
-	ENDM
-
-PUTSI: MACRO
-	push hl
-	call putsi
-	db \1, 0
-	pop hl
-	ENDM
-
-PUTSIL: MACRO
-	push hl
-	call putsi
-	db \1, 13, 10, 0
-	pop hl
-	ENDM
-
-PUTHEX: MACRO
-	ld a, \1
-	call puthex
-	ENDM
-	
 	SECTION "config", HOME[$0]
 myMAC:	db $12, $34, $56, $78, $9A, $00
 myIP:	db $0A, $00, $00, $02
@@ -99,7 +74,7 @@ getpacket:
 	PUTHEX b
 	PUTHEX c
 	PUTSIL " byte packet from hardware."
-	ld hl, $D000
+	ld hl, packet
 	call ether_input
 	ret
 
@@ -192,86 +167,136 @@ ether_input:
 	ret
 
 arp_input:
+	; First, verify that this is an ARP packet that we can handle.
+	ld c, 7
+	ld de, .expectedarp
+.cklp:	xor a
+	cp c
+	jr z, .ckdone
+	ld a, [de]
+	cp [hl]
+	jr nz, .badarp
+	inc de
+	inc hl
+	dec c
+	jr .cklp
+.ckdone:
+	ld a, [hli]
+	cp 1
+	jr z, .req
+	cp 2
+	jp z, .resp
+.badarp:
+	PUTSIL "arp_input: Unknown protocol hardware or request"
+	ret
+.expectedarp:
+	db $00, $01, $08, $00, $06, $04, $00
+
+.req:
+	PUTSIL "arp_input.req: Request"
+	; Is it asking about us?
+	push hl
+	ld b, 0
+	ld c, $10	; SHA + SPA + THA
+	add hl, bc
+	ld de, myIP
+	ld c, 4
+.iplp:	ld a, [de]
+	cp [hl]
+	jp nz, .notourip
+	inc de
+	inc hl
+	dec c
+	jr nz, .iplp
+	PUTSIL "arp_input.req: Aimed at us."
+	pop hl	; Now synthesize a response packet.
+	push hl
+	dec hl
+	ld a, $02	; Reply!
+	ld [hli], a
+	ld d, h
+	ld e, l
+	ld hl, 10	; SHA + SPA
+	add hl, de	; Now DE points at SHA, and HL points at THA
+	ld c, 10
+.dcl:	ld a, [de]
+	ld [hli], a
+	inc de
+	dec c
+	jr nz, .dcl
+	pop hl		; HL now points at SHA
+	ld de, myMAC
+	ld c, $06
+.mcl:	ld a, [de]
+	ld [hli], a
+	inc de
+	dec c
+	jr nz, .mcl
+	ld de, myIP	; HL now points at SPA
+	ld c, $04
+.icl:	ld a, [de]
+	ld [hli], a
+	inc de
+	dec c
+	jr nz, .icl
+	ld d, h
+	ld e, l		; HL now points at THA
+	ld hl, -32
+	add hl, de	; HL has now been backed up to the start of the ethernet header.
+	ld d, h
+	ld e, l		; DE now points at the dest
+	ld hl, 6
+	add hl, de	; HL now points at the source
+	ld c, $06
+.sdcl:	ld a, [hli]
+	ld [de], a
+	inc de
+	dec c
+	jr nz, .sdcl
+	ld hl, myMAC	; DE now points at the source
+	ld c, $06
+.smcl:	ld a, [hli]
+	ld [de], a
+	inc de
+	dec c
+	jr nz, .smcl
+	ld hl, -12
+	add hl, de	; HL now points at the start of the packet -- should be C000!
+	ld b, 0
+	ld c, 64	; Minimum size packet; avoid transmitting a runt
+	call packet_send
+	PUTSIL "arp_input.req: sent response!"
+	ret
+.notourip:
+	PUTSIL "arp_input.req: Not aimed at us; ignoring."
+	pop hl
+	ret
+	
+.resp:
+	PUTSIL "arp_input.resp: Response"
 	ret
 
 ip_input:
 	ret
 
+packet_send:
+	ld a, [ETH_STATUS]	; Wait for the port to become available.
+	and $01
+	jr nz, packet_send
+	ld a, b
+	ld [ETH_DATA], a
+	ld a, c
+	ld [ETH_DATA], a
+.pkts:	ld a, b
+	or c
+	ret z
+	dec bc
+	ld a, [hli]
+	ld [ETH_DATA], a
+	jr .pkts
+
 	SECTION "ethdata", BSS
 bssstart	DS 0
 packet		DS 1552
+arptable	DS ARP_ENTRIES * ARP_ENTRY_SIZE
 bssend		DS 0
-
-
-; SERIAL ROUTINES ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-	SECTION "serial", HOME
-
-putc:
-	push af
-.waitport:
-	ld a,[$FF53]
-	and $01
-	jr nz,.waitport
-	pop af
-	ld [$FF52],a
-	ret
-
-puts:
-	ld a, [hli]
-	cp $00
-	ret z
-	call putc
-	jr puts
-
-EX_SP_HL: MACRO
-	push de
-	di
-	add sp, 2
-	pop de
-	push hl
-	ld l, e
-	ld h, d
-	add sp, -2
-	ei
-	pop de
-	ENDM
-
-putsi:
-	pop hl
-	push af
-	push bc
-	push de
-.lp:	ld a, [hli]
-	or a
-	jr z, .done
-	call putc
-	jr .lp
-.done:	pop de
-	pop bc
-	pop af
-	push hl
-	ret
-
-puthex:				; Put two hex nibbles to the serial console.
-	push bc
-	push hl
-	push af
-	swap a
-	and $0F
-	ld hl,hex
-	ld b,0
-	ld c,a
-	add hl,bc
-	ld a, [hl]
-	call putc
-	pop af
-	and $0F
-	ld hl,hex
-	ld c,a
-	add hl,bc
-	ld a, [hl]
-	call putc
-	pop hl
-	pop bc
-	ret
-hex:	db "0123456789ABCDEF"
diff --git a/serial.inc b/serial.inc
new file mode 100644
index 0000000..c3ca090
--- /dev/null
+++ b/serial.inc
@@ -0,0 +1,100 @@
+PUTC: MACRO
+	ld a, \1
+	call putc
+	ENDM
+
+PUTS: MACRO
+	ld hl, \1
+	call puts
+	ENDM
+
+PUTSI: MACRO
+	push hl
+	call putsi
+	db \1, 0
+	pop hl
+	ENDM
+
+PUTSIL: MACRO
+	push hl
+	call putsi
+	db \1, 13, 10, 0
+	pop hl
+	ENDM
+
+PUTHEX: MACRO
+	ld a, \1
+	call puthex
+	ENDM
+
+	SECTION "serial", HOME
+
+putc:
+	push af
+.waitport:
+	ld a,[$FF53]
+	and $01
+	jr nz,.waitport
+	pop af
+	ld [$FF52],a
+	ret
+
+puts:
+	ld a, [hli]
+	cp $00
+	ret z
+	call putc
+	jr puts
+
+EX_SP_HL: MACRO
+	push de
+	di
+	add sp, 2
+	pop de
+	push hl
+	ld l, e
+	ld h, d
+	add sp, -2
+	ei
+	pop de
+	ENDM
+
+putsi:
+	pop hl
+	push af
+	push bc
+	push de
+.lp:	ld a, [hli]
+	or a
+	jr z, .done
+	call putc
+	jr .lp
+.done:	pop de
+	pop bc
+	pop af
+	push hl
+	ret
+
+puthex:				; Put two hex nibbles to the serial console.
+	push bc
+	push hl
+	push af
+	swap a
+	and $0F
+	ld hl,hex
+	ld b,0
+	ld c,a
+	add hl,bc
+	ld a, [hl]
+	call putc
+	pop af
+	and $0F
+	ld hl,hex
+	ld c,a
+	add hl,bc
+	ld a, [hl]
+	call putc
+	pop hl
+	pop bc
+	ret
+hex:	db "0123456789ABCDEF"
-- 
2.43.0