checksumming part finish
This commit is contained in:
Nico Schottelius
parent
b757a3c2b0
commit
92e1407729
2 changed files with 112 additions and 11 deletions
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@ -1,7 +1,77 @@
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#!/usr/bin/python3
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#from __future__ import unicode_literals
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import ipaddress
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from scapy.all import *
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import array
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import struct
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# stolen from scapy (little endian system)
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def checksum_scapy(pkt):
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if len(pkt) % 2 == 1:
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pkt += b"\0"
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s = sum(array.array("H", pkt))
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s = (s >> 16) + (s & 0xffff)
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s += s >> 16
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s = ~s
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return (((s>>8)&0xff)|s<<8) & 0xffff
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# 1. convert to array of "bytes"
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# 2. import into an array
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# 3. sum everything up
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def sum_for_udp(packet):
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sums = ""
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sums += struct.pack("H", packet[UDP].sport)
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sums += struct.pack("H", packet[UDP].dport)
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sums += struct.pack("H", packet[UDP].len)
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return sums
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def sum_for_v6(packet):
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# hdr.ipv6.src_addr, /* 128 */
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# hdr.ipv6.dst_addr, /* 128 */
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# meta.length_without_ip_header, /* 32 */
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# 24w0, /* 24 */
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# hdr.ipv6.next_header, /* 8 */
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# /* total: 324 */
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# // UDP header
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# hdr.udp.src_port, /* 16 */
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# hdr.udp.dst_port, /* 16 */
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# hdr.udp.payload_length /* 16 */
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# /* all: 372 */
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# order does not matter!
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sums = ""
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sums += ipaddress.IPv6Address(packet[IPv6].src.decode("utf-8")).packed
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sums += ipaddress.IPv6Address(packet[IPv6].dst.decode("utf-8")).packed
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sums += struct.pack("H", packet[IPv6].plen)
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sums += struct.pack("B", packet[IPv6].nh)
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print("{} - {} - {}".format(len(sums), sums, checksum_scapy(sums)))
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return sums
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def sum_for_v4(packet):
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# Get diffs -- for UDP
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# udp_v4 =
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# hdr.ipv4.src_addr,
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# hdr.ipv4.dst_addr,
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# 8w0,
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# hdr.ipv4.protocol,
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# meta.length_without_ip_header,
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sums = ""
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sums += ipaddress.IPv4Address(packet[IP].src.decode("utf-8")).packed
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sums += ipaddress.IPv4Address(packet[IP].dst.decode("utf-8")).packed
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sums += struct.pack("H", packet[IP].len - 20) # -20 for ip header
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sums += struct.pack("H", packet[IP].proto) # udp / tcp
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return sums
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if __name__ == '__main__':
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p = []
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@ -41,18 +111,16 @@ if __name__ == '__main__':
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chk_new = packet_rebuild[UDP].chksum
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print("chk1 = {} chk2={}".format(chk_old, chk_new))
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# Get diffs -- for UDP
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# udp_v4 =
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# hdr.ipv4.src_addr,
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# hdr.ipv4.dst_addr,
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# 8w0,
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# hdr.ipv4.protocol,
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# meta.length_without_ip_header,
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sums = ""
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# // UDP header
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# hdr.udp.src_port,
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# hdr.udp.dst_port,
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# hdr.udp.payload_length
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if IP in packet:
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sums += sum_for_v4(packet_rebuild)
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if IPv6 in packet:
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sums += sum_for_v6(packet_rebuild)
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# if UDP in packet:
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# sums += sum_for_udp(packet_rebuild)
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print("Checksum-parts {} for {}".format(checksum_scapy(sums), packet_rebuild.__repr__()))
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# Checksums:
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33
doc/plan.org
33
doc/plan.org
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@ -384,6 +384,12 @@
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| 2019-06-27 | | |
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| | Target Hardware: code running | |
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| | | |
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| 2019-07-01 | | |
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| | Meeting Laurent | |
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| | | |
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| | - Diff'ing in python | |
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| | - Phasing in netpfga code | |
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| | | |
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| 2019-07-11 | | |
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| | Integrated org-documentation into latex / export working | |
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| | https://bastibe.de/2014-09-23-org-cite.html | |
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@ -4893,6 +4899,33 @@ actual (tlast, tkeep, tdata) = (0, ffffffff, 000000000000000080fe403b0a0000000
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*** 2019-06-24: find out how the expected/actual packet lines are generated
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- afair: indirectly by running gen_testdata.py -> replace script
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with port1
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*** 2019-07-01: verify checksumming
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#+BEGIN_CENTER
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if struct.pack("H",1) == b"\x00\x01": # big endian
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def checksum(pkt):
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if len(pkt) % 2 == 1:
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pkt += b"\0"
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s = sum(array.array("H", pkt))
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s = (s >> 16) + (s & 0xffff)
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s += s >> 16
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s = ~s
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return s & 0xffff
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else:
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def checksum(pkt):
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if len(pkt) % 2 == 1:
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pkt += b"\0"
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s = sum(array.array("H", pkt))
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s = (s >> 16) + (s & 0xffff)
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s += s >> 16
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s = ~s
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return (((s>>8)&0xff)|s<<8) & 0xffff
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#+END_CENTER
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*** 2019-07-01: 128 bit ipv6 struct -> no conversion!
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- https://docs.python.org/2.7/library/struct.html
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- .packed of ipaddress works
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*** 2019-07-01: finish sum, use scapy checksum
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*** 2019-07-01: meeting Laurent
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** References / Follow up
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*** RFC 791 IPv4 https://tools.ietf.org/html/rfc791
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*** RFC 792 ICMP https://tools.ietf.org/html/rfc792
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