;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; ;;
;; IP.INC ;;
;; ;;
;; IP Processes for Menuet OS TCP/IP stack ;;
;; ;;
;; Version 0.3 29 August 2002 ;;
;; ;;
;; Copyright 2002 Mike Hibbett, mikeh@oceanfree.net ;;
;; ;;
;; See file COPYING for details ;;
;; ;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;*******************************************************************
; Interface
;
; ip_rx processes all packets received by the network layer
; It calls the appropriate protocol handler
;
;
;
;*******************************************************************
;***************************************************************************
; Function
; ip_rx
;
; Description
; Handles received IP packets
; This is a kernel function, called by stack_handler
;
;***************************************************************************
ip_rx:
; Look for a buffer to tx
mov eax, IPIN_QUEUE
call dequeue
cmp ax, NO_BUFFER
je ipr_exit ; Exit if no buffer available
push eax
; convert buffer pointer eax to the absolute address
mov ecx, IPBUFFSIZE
mul ecx
add eax, IPbuffs
mov edx, eax ; Save the address in edx for use by future processes
; Validate the IP checksum
mov ebx, edx
mov ah, [ebx + 10]
mov al, [ebx + 11] ; Get the checksum in intel format
mov [ebx + 10], word 0 ; clear checksum field - need to when
; recalculating checksum
; this needs two data pointers and two size #.
; 2nd pointer can be of length 0
mov ebx, edx
mov [checkAdd1], ebx
mov [checkSize1], word 20
mov [checkAdd2], dword 0
mov [checkSize2], word 0
call checksum ; Recalculate IP checksum
cmp ax, [checkResult]
jnz ipr_dump
; If the IP address is 255.255.255.255, accept it
; - it is a broadcast packet, which we need for dhcp
mov eax, [edx + 16]
cmp eax, 0xffffffff
je ipr_p0
; Validate the IP address, if it isn't broadcast
cmp eax, [stack_ip]
jnz ipr_dump
ipr_p0:
mov al, [edx]
and al, 0x0f
cmp al, 0x05
jnz ipr_dump
cmp [edx+8], byte 0
jz ipr_dump
mov ax, [edx + 6]
and ax, 0xFFBF
cmp ax, 0
jnz ipr_dump
; Check the protocol, and call the appropriate handler
; Each handler will re-use or free the queue buffer as appropriate
mov al, [edx + 9]
cmp al , PROTOCOL_ICMP
jnz ipr_p1
pop eax
call icmp_rx
jmp ipr_exit
ipr_p1:
cmp al , PROTOCOL_TCP
jnz ipr_p2
pop eax
call tcp_rx
jmp ipr_exit
ipr_p2:
cmp al , PROTOCOL_UDP
jnz ipr_dump
pop eax
call udp_rx
jmp ipr_exit
ipr_dump:
; No protocol handler available, so
; silently dump the packet, freeing up the queue buffer
; inc dword [dumped_rx_count]
pop eax
call freeBuff
ipr_exit:
ret
;***************************************************************************
; Function
; icmp_rx
;
; Description
; ICMP protocol handler
; This is a kernel function, called by ip_rx
; edx contains the address of the buffer in use.
; This buffer must be reused or marked as empty afterwards
;
;***************************************************************************
icmp_rx:
cmp [edx + 20], byte 8 ; Is this an echo request? discard if not
jz icmp_echo
call freeBuff
jmp icmp_exit
icmp_echo:
push eax
mov [edx + 10], word 0 ; I think this was already done by IP rx
; swap the source and destination addresses
mov ecx, [edx + 16]
mov eax, [edx + 12]
mov [edx + 16], eax
mov [edx + 12], ecx
; recaluculate the IP header checksum
mov ebx, edx
mov [checkAdd1], ebx
mov [checkSize1], word 20
mov [checkAdd2], dword 0
mov [checkSize2], word 0
call checksum
mov ax, [checkResult]
mov [edx + 10], ah
mov [edx + 11], al ; ?? correct byte order?
mov [edx + 20], byte 0 ; change the request to a response
mov [edx + 22], word 0 ; clear ICMP checksum prior to re-calc
; Calculate the length of the ICMP data ( IP payload)
mov ah, [edx + 2]
mov al, [edx + 3]
sub ax, 20
mov [checkSize1], ax
mov ebx, edx
add ebx, 20
mov [checkAdd1], ebx
mov [checkAdd2], dword 0
mov [checkSize2], word 0
call checksum
mov ax, [checkResult]
mov [edx + 22], ah
mov [edx + 23], al
; Queue packet for transmission
pop ebx
mov eax, NET1OUT_QUEUE
call queue
icmp_exit:
ret