#!/usr/bin/env python3
#
# Copyright (c) 2025 Alexander Bluhm <bluhm@openbsd.org>

from fragcommon import *

#                               index boundary 4096 |
# |--------------|
#                 ....
#                     |--------------|
#                                    |----------|
#                                               |XXXX----------|
#                                          |XXXX----|
#                                                               |---|

# this should trigger "frag tail overlap %d" and "frag head overlap %d"
def send(src, dst, send_if, recv_if):
	pid = os.getpid()
	eid = pid & 0xffff
	payload = b"ABCDEFGHIJKLMNOP"
	dummy = b"01234567"
	fragsize = 1024
	boundary = 4096
	fragnum = int(boundary / fragsize)
	packet = sp.IP(src=src, dst=dst)/ \
	    sp.ICMP(type='echo-request', id=eid)/ \
	    ((int((boundary + fragsize) / len(payload)) + 1) * payload)
	packet_length = len(packet)
	frag = []
	fid = pid & 0xffff
	for i in range(fragnum-1):
		frag.append(sp.IP(src=src, dst=dst, proto=1, id=fid,
		    frag=(i * fragsize)>>3, flags='MF')/
		    bytes(packet)[20 + i * fragsize:20 + (i + 1) * fragsize])
	frag.append(sp.IP(src=src, dst=dst, proto=1, id=fid,
	    frag=(boundary - fragsize) >> 3, flags='MF')/
	    bytes(packet)[20 + boundary - fragsize:20 + boundary - len(dummy)])
	frag.append(sp.IP(src=src, dst=dst, proto=1, id=fid,
	    frag=(boundary - len(dummy)) >> 3, flags='MF')/
	    (dummy+bytes(packet)[20 + boundary:20 + boundary + fragsize]))
	frag.append(sp.IP(src=src, dst=dst, proto=1, id=fid,
	    frag=(boundary - 8 - len(dummy)) >> 3, flags='MF')/
	    (dummy+bytes(packet)[20 + boundary - 8:20 + boundary]))
	frag.append(sp.IP(src=src, dst=dst, proto=1, id=fid,
	    frag=(boundary + fragsize) >> 3)/bytes(packet)[20 + boundary + fragsize:])
	eth=[]
	for f in frag:
		eth.append(sp.Ether() / f)

	if os.fork() == 0:
		time.sleep(1)
		for e in eth:
			sp.sendp(e, iface=send_if)
			time.sleep(0.001)
		os._exit(0)

	ans = sp.sniff(iface=recv_if, timeout=3, filter=
	    "ip and src " + dst + " and dst " + src + " and icmp")
	for a in ans:
		if a and a.type == sp.ETH_P_IP and \
		    a.payload.proto == 1 and \
		    a.payload.frag == 0 and \
		    sp.icmptypes[a.payload.payload.type] == 'echo-reply':
			id = a.payload.payload.id
			print("id=%#x" % (id))
			if id != eid:
				print("WRONG ECHO REPLY ID")
				exit(2)
		if a and a.type == sp.ETH_P_IP and \
		    a.payload.proto == 1 and \
		    a.payload.frag > 0 and \
		    a.payload.flags == '':
			length = (a.payload.frag << 3) + a.payload.len
			print("len=%d" % (length))
			if length != packet_length:
				print("WRONG ECHO REPLY LENGTH")
				exit(1)
			exit(0)
	print("NO ECHO REPLY")
	exit(1)

if __name__ == '__main__':
	main(send)