From 92e14077297fb28fdb39b18953268a4e61b5444e Mon Sep 17 00:00:00 2001
From: Nico Schottelius <nico@nico-notebook.schottelius.org>
Date: Mon, 1 Jul 2019 09:36:14 +0200
Subject: [PATCH] checksumming part finish

---
 bin/checksum_delta_diff_test.py | 90 +++++++++++++++++++++++++++++----
 doc/plan.org                    | 33 ++++++++++++
 2 files changed, 112 insertions(+), 11 deletions(-)

diff --git a/bin/checksum_delta_diff_test.py b/bin/checksum_delta_diff_test.py
index b885889..1e8d4e9 100644
--- a/bin/checksum_delta_diff_test.py
+++ b/bin/checksum_delta_diff_test.py
@@ -1,7 +1,77 @@
 #!/usr/bin/python3
 
 #from __future__ import unicode_literals
+import ipaddress
 from scapy.all import *
+import array
+import struct
+
+# stolen from scapy (little endian system)
+def checksum_scapy(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
+
+
+# 1. convert to array of "bytes"
+# 2. import into an array
+# 3. sum everything up
+
+
+def sum_for_udp(packet):
+    sums = ""
+    sums += struct.pack("H", packet[UDP].sport)
+    sums += struct.pack("H", packet[UDP].dport)
+    sums += struct.pack("H", packet[UDP].len)
+
+    return sums
+
+def sum_for_v6(packet):
+    # hdr.ipv6.src_addr,               /* 128 */
+    # hdr.ipv6.dst_addr,               /* 128 */
+    # meta.length_without_ip_header,   /* 32 */
+    # 24w0,                            /* 24 */
+    # 		hdr.ipv6.next_header,            /* 8 */
+    #                                  /* total: 324 */
+
+    # 		// UDP header
+    # hdr.udp.src_port,                /* 16 */
+    # hdr.udp.dst_port,                /* 16 */
+    # hdr.udp.payload_length           /* 16 */
+    #                                  /* all: 372 */
+
+    # order does not matter!
+    sums = ""
+
+    sums += ipaddress.IPv6Address(packet[IPv6].src.decode("utf-8")).packed
+    sums += ipaddress.IPv6Address(packet[IPv6].dst.decode("utf-8")).packed
+    sums += struct.pack("H", packet[IPv6].plen)
+    sums += struct.pack("B", packet[IPv6].nh)
+
+    print("{} - {} - {}".format(len(sums), sums, checksum_scapy(sums)))
+
+    return sums
+
+def sum_for_v4(packet):
+    # Get diffs -- for UDP
+    # udp_v4 =
+    #             hdr.ipv4.src_addr,
+    #             hdr.ipv4.dst_addr,
+    #             8w0,
+    #             hdr.ipv4.protocol,
+    #             meta.length_without_ip_header,
+    sums = ""
+
+    sums += ipaddress.IPv4Address(packet[IP].src.decode("utf-8")).packed
+    sums += ipaddress.IPv4Address(packet[IP].dst.decode("utf-8")).packed
+    sums += struct.pack("H", packet[IP].len - 20) # -20 for ip header
+    sums += struct.pack("H", packet[IP].proto) # udp / tcp
+
+    return sums
 
 if __name__ == '__main__':
     p = []
@@ -41,18 +111,16 @@ if __name__ == '__main__':
         chk_new = packet_rebuild[UDP].chksum
         print("chk1 = {} chk2={}".format(chk_old, chk_new))
 
-    # Get diffs -- for UDP
-    # udp_v4 =
-    # hdr.ipv4.src_addr,
-    #             hdr.ipv4.dst_addr,
-    #             8w0,
-    #             hdr.ipv4.protocol,
-    #     		    meta.length_without_ip_header,
+        sums = ""
 
-    #     			// UDP header
-    #             hdr.udp.src_port,
-    #             hdr.udp.dst_port,
-    #             hdr.udp.payload_length
+        if IP in packet:
+            sums += sum_for_v4(packet_rebuild)
+        if IPv6 in packet:
+            sums += sum_for_v6(packet_rebuild)
+#        if UDP in packet:
+#            sums += sum_for_udp(packet_rebuild)
+
+        print("Checksum-parts {} for {}".format(checksum_scapy(sums), packet_rebuild.__repr__()))
 
 
 # Checksums:
diff --git a/doc/plan.org b/doc/plan.org
index b1efe5c..fd24e5d 100644
--- a/doc/plan.org
+++ b/doc/plan.org
@@ -384,6 +384,12 @@
 | 2019-06-27 |                                                                            |       |
 |            | Target Hardware: code running                                              |       |
 |            |                                                                            |       |
+| 2019-07-01 |                                                                            |       |
+|            | Meeting Laurent                                                            |       |
+|            |                                                                            |       |
+|            | - Diff'ing in python                                                       |       |
+|            | - Phasing in netpfga code                                                  |       |
+|            |                                                                            |       |
 | 2019-07-11 |                                                                            |       |
 |            | Integrated org-documentation into latex / export working                   |       |
 |            | https://bastibe.de/2014-09-23-org-cite.html                                |       |
@@ -4893,6 +4899,33 @@ actual   (tlast, tkeep, tdata) = (0, ffffffff, 000000000000000080fe403b0a0000000
 *** 2019-06-24: find out how the expected/actual packet lines are generated
     - afair: indirectly by running gen_testdata.py -> replace script
       with port1
+*** 2019-07-01: verify checksumming
+#+BEGIN_CENTER
+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
+*** 2019-07-01: 128 bit ipv6 struct -> no conversion!
+    - https://docs.python.org/2.7/library/struct.html
+    - .packed of ipaddress works
+*** 2019-07-01: finish sum, use scapy checksum
+*** 2019-07-01: meeting Laurent
 ** References / Follow up
 *** RFC 791 IPv4 https://tools.ietf.org/html/rfc791
 *** RFC 792 ICMP https://tools.ietf.org/html/rfc792