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Delta checksum approach

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Nico Schottelius 2019-06-23 14:19:06 +02:00
commit 408dd6b782
2 changed files with 117 additions and 2 deletions
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doc/plan.org
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@ -2946,6 +2946,62 @@ SimpleSumeSwitch(
TopDeparser()
) main;
**** Understand the different switch models (?)
*** TODO Find out whether delta based checksumming is feasible [in P4]
**** DONE Analysing scapy
CLOSED: [2019-06-23 Sun 14:18]
#+BEGIN_CENTER
[13:51] line:~% dpkg -L python3-scapy | grep inet
/usr/lib/python3/dist-packages/scapy/layers/inet.py
/usr/lib/python3/dist-packages/scapy/layers/inet6.py
if self.chksum is None:
ck = checksum(p)
p = p[:10]+chb(ck>>8)+chb(ck&0xff)+p[12:]
return p+pay
[13:55] line:~% grep checksum -r /usr/lib/python3/dist-packages/scapy/ | grep def
/usr/lib/python3/dist-packages/scapy/contrib/isis.py: def checksum_info(self, hdrlen):
/usr/lib/python3/dist-packages/scapy/contrib/isis.py: def checksum_info(self, hdrlen):
/usr/lib/python3/dist-packages/scapy/contrib/ospf.py:def ospf_lsa_checksum(lsa):
/usr/lib/python3/dist-packages/scapy/utils.py: def checksum(pkt):
/usr/lib/python3/dist-packages/scapy/utils.py: def checksum(pkt):
/usr/lib/python3/dist-packages/scapy/utils.py:def fletcher16_checksum(binbuf):
/usr/lib/python3/dist-packages/scapy/layers/sctp.py:def sctp_checksum(buf):
[13:55] line:~%
if struct.pack("H",1) == b"\x00\x01": # big endian
def checksum(pkt):
if len(pkt) % 2 == 1:
pkt += b"\0"
s = sum(array.array("H", pkt))
s = (s >> 16) + (s & 0xffff)
s += s >> 16
s = ~s
return s & 0xffff
else:
def checksum(pkt):
if len(pkt) % 2 == 1:
pkt += b"\0"
s = sum(array.array("H", pkt))
s = (s >> 16) + (s & 0xffff)
s += s >> 16
s = ~s
return (((s>>8)&0xff)|s<<8) & 0xffff
#+END_CENTER
**** TODO Trying to create a delta diff: AAAA vs. BBAA
#+BEGIN_CENTER
[14:17] line:bin% python3 checksum_from_scapy.py AAAA
b'AAAA'
32125
[14:18] line:bin% python3 checksum_from_scapy.py BBAA
b'BBAA'
31868
#+END_CENTER
*** TODO Get ANY p4 program to successfully run on netpfga
**** TODO mirroring ethernet
***** no packets seen on source interface
@ -3061,6 +3117,9 @@ ERROR: failed to convert p.ethernet.dstAddr of type <type 'str'> to an integer
** Additional features queue (to be discussed)
*** TODO Offset based translation (v4->v6) -> same as range (?)
*** TODO IP address learning (v6/v4) for real life switch? How do hosts find it?
** Netpfga cabling
| eth2 <--> nf0 |
| eth1 <--> nf3 |
* Thesis documentation
** Introduction
*** Related work
@ -4685,9 +4744,21 @@ SerialException: device reports readiness to read but returned no data (device d
"The checksum field is the 16 bit one's complement of the one's
complement sum of all 16-bit words in the header and text."
https://en.wikipedia.org/wiki/Transmission_Control_Protocol#Checksum_computation
*** 2019-06-21: create table entries on new card
#+BEGIN_CENTER
>> table_cam_add_entry lookup_table send_to_port1 ff:ff:ff:ff:ff:ff =>
CAM_Init_ValidateContext() - done
WROTE 0x44020050 = 0xffffffff
WROTE 0x44020054 = 0xffff
WROTE 0x44020080 = 0x0003
READ 0x44020044 = 0x0001
WROTE 0x44020040 = 0x0001
READ 0x44020044 = 0x0001
READ 0x44020044 = 0x0001
success
>>
#+END_CENTER
** References / Follow up
*** RFC 791 IPv4 https://tools.ietf.org/html/rfc791
*** RFC 792 ICMP https://tools.ietf.org/html/rfc792