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icmp.s
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;
; Internet Control Message Protocol (RFC 792)
;
; Steve Maddison, 08/01/2008
;
; ICMP header offsets
icmp_hdr_type: equ 0
icmp_hdr_code: equ 1
icmp_hdr_checksum: equ 2
; Bytes 4 thru 7 have different uses
icmp_hdr_ident: equ 4
icmp_hdr_pointer: equ 4
icmp_hdr_gateway: equ 4
icmp_hdr_seq_number: equ 6
; Byte 8 onwards is used for "data", often the first few
; bytes of the original packet, but sometimes other stuff.
icmp_hdr_data: equ 8
icmp_hdr_orig_timestamp: equ 8
icmp_hdr_rec_timestamp: equ 12
icmp_hdr_tx_timestamp: equ 16
; ICMP Types/codes
; Destination Unreachable
icmp_type_dest_unreachable: equ 3
icmp_code_net_unreachable: equ 0
icmp_code_host_unreachable: equ 1
icmp_code_proto_unreachable: equ 2
icmp_code_port_unreachable: equ 3
icmp_code_fragment_needed: equ 4
icmp_code_source_failed: equ 5
; Source Quench
icmp_type_source_quench: equ 4
; Redirect
icmp_type_redirect: equ 5
icmp_code_redir_network: equ 0
icmp_code_redir_host: equ 1
icmp_code_redir_tos_network: equ 2
icmp_code_redir_tos_host: equ 3
; Echo
icmp_type_echo_request: equ 8
icmp_type_echo_reply: equ 0
; Time Exceeded
icmp_type_time_exceeded: equ 11
icmp_code_ttl_exceeded: equ 0
icmp_code_frag_time_exceeded: equ 1
; Parameter Problem
icmp_type_param_problem: equ 12
; Timestamps
icmp_type_timestamp_request: equ 13
icmp_type_timestamp_reply: equ 14
; Information
icmp_type_info_request: equ 15
icmp_type_info_reply: equ 16
; Data to send with echo messages
icmp_echo_data: defm "abcdefgh"
icmp_echo_data_length: equ 8
; Name: icmp_echo_reply
; Desc: Reply to an ICMP echo message
; In: HL = Address of data buffer
; DE = Data length
; IX = Address of IP header
icmp_echo_reply:
push de ; data length DE => IY
pop iy
; Move get packet's source into BCDE
ld b,(ix+ip_hdr_src_addr+0)
ld c,(ix+ip_hdr_src_addr+1)
ld d,(ix+ip_hdr_src_addr+2)
ld e,(ix+ip_hdr_src_addr+3)
; Set message type
ld (hl),icmp_type_echo_reply
; Set protocol
ld a,ip_proto_icmp
; Send packet back
call ip_tx
ret
; Name: icmp_rx
; Desc: Process ICMP message
; In: HL = Address of data buffer
; DE = Data length
; IX = Address of IP header
icmp_rx:
push hl ; save
push ix
; Check checksum
push de
pop bc
push hl
pop ix
ld hl,0
call ip_calc_checksum
ld a,h
or l
pop ix ; restore
pop hl
jp nz,icmp_rx_discard
; Checksum OK, process message
ld a,(hl) ; get message type
icmp_rx_echo_request:
cp icmp_type_echo_request
jp nz,icmp_rx_echo_reply
call icmp_echo_reply
jp icmp_rx_end
icmp_rx_echo_reply:
; Need socket
icmp_rx_discard:
icmp_rx_end:
ret
; Name: icmp_tx_echo
; Desc: Send an ICMP echo or echo reply message (types 0 or 8)
; In: A = mesage type
; BCDE = destination IP address
icmp_tx_echo:
ld ix,icmp_scratch
ld (ix+icmp_hdr_type),a
ld (ix+icmp_hdr_code),0
ld (ix+icmp_hdr_checksum+0),0
ld (ix+icmp_hdr_checksum+1),0
ld (ix+icmp_hdr_ident+0),0
ld (ix+icmp_hdr_ident+1),0
ld (ix+icmp_hdr_seq_number+0),0
ld (ix+icmp_hdr_seq_number+1),0
push bc
push de
ld hl,icmp_scratch
ld bc,icmp_hdr_data
add hl,bc
push hl
pop de
ld hl,icmp_echo_data
ld bc,icmp_echo_data_length
ldir
ld bc,icmp_hdr_data+icmp_echo_data_length
push bc
ld hl,0
call ip_calc_checksum
ld (ix+icmp_hdr_checksum+0),h
ld (ix+icmp_hdr_checksum+1),l
pop iy
pop de
pop bc
ld hl,icmp_scratch
ld a,ip_proto_icmp
call ip_tx
ret