Fragment size re calculation inside fragment funciton

[inoyatov]

Can somebody explain why fragment size is re-calculating in line 554? I need payload exactly 100 bytes. But after re-calculation i got 104 bytes. What is reason? Thank you in advance.

scapy/scapy/layers/inet.py

Lines 552 to 577 in 90c8d82

	def fragment(self, fragsize=1480):
	"""Fragment IP datagrams"""
	fragsize = (fragsize + 7) // 8 * 8
	lst = []
	fnb = 0
	fl = self
	while fl.underlayer is not None:
	fnb += 1
	fl = fl.underlayer
	for p in fl:
	s = raw(p[fnb].payload)
	nb = (len(s) + fragsize - 1) // fragsize
	for i in range(nb):
	q = p.copy()
	del(q[fnb].payload)
	del(q[fnb].chksum)
	del(q[fnb].len)
	if i != nb - 1:
	q[fnb].flags |= 1
	q[fnb].frag += i * fragsize // 8
	r = conf.raw_layer(load=s[i * fragsize:(i + 1) * fragsize])
	r.overload_fields = p[fnb].payload.overload_fields.copy()
	q.add_payload(r)
	lst.append(q)
	return lst

[gpotter2]

From https://tools.ietf.org/html/rfc791#section-3.2 (page 25, top):

If an internet datagram is fragmented, its data portion must be broken on 8 octet boundaries.

To answer your question, fragment size must be a multiple of 8.