Fix total_length by adding 15 bytes

doc/plan.org

@@ -489,7 +489,7 @@ DEBUG:main:v6 reassambled=<Ether  dst=00:00:0a:00:00:42 src=00:00:0a:00:00:01 ty
 
 debugging MIGHT come from nat64 table!
 
-***** TODO try3: re-rewrite: no packets on h3 again (2019-03-30)
+***** DONE try3: re-rewrite: no packets on h3 again (2019-03-30)
 p4@ubuntu:~$ ~/master-thesis/p4app/sniff-host.sh h1 static_nat64
 + cd /home/p4/master-thesis/pcap
 + host=h1
@@ -525,7 +525,73 @@ p4@ubuntu:~/master-thesis/pcap$
 INFO:main:unhandled reassambled=<Ether  dst=33:33:ff:00:00:42 src=00:00:0a:00:00:01 type=0x86dd |<IPv6  version=6 tc=0 fl=0 plen=32 nh=ICMPv6 hlim=255 src=fe80::200:aff:fe00:1 dst=ff02::1:ff00:42 |<ICMPv6ND_NS  type=Neighbor Solicitation code=0 cksum=0x37df res=0 tgt=2001:db8::42 |<ICMPv6NDOptSrcLLAddr  type=1 len=1 lladdr=00:00:0a:00:00:01 |>>>> from table TABLE_V6_NETWORKS
 
 -> checksums likely broken again due to checksum changes
+-> solved, test case for verification is
 
+#+BEGIN_SRC
+p4@ubuntu:~$ python ~/master-thesis/p4app/test.py -m v6_static_mapping --debug
+INFO:main:Trying to reach 10.0.0.1 (2001:db8:1::a00:1) from h1
+PING 2001:db8:1::a00:1(2001:db8:1::a00:1) 56 data bytes
+From 2001:db8::1 icmp_seq=1 Destination unreachable: Address unreachable
+
+--- 2001:db8:1::a00:1 ping statistics ---
+1 packets transmitted, 0 received, +1 errors, 100% packet loss, time 0ms
+
+p4@ubuntu:~$ python ~/master-thesis/p4app/test.py -m ping6_switch --debug
+INFO:main:Trying to reach 2001:db8::42 from h1
+PING 2001:db8::42(2001:db8::42) 56 data bytes
+64 bytes from 2001:db8::42: icmp_seq=1 ttl=64 time=6.30 ms
+
+--- 2001:db8::42 ping statistics ---
+1 packets transmitted, 1 received, 0% packet loss, time 0ms
+rtt min/avg/max/mdev = 6.304/6.304/6.304/0.000 ms
+
+
+#+END_SRC
+***** TODO try4: h3 receives packet, but length seems to be off
+      - Seeing frame check sequence error
+      - total length ipv4 = 69 (h3)
+      - ipv6 payload length = 64 (h1)
+      - comes from         hdr.ipv4.totalLen       = (bit<16>) hdr.ipv6.payload_length + 5;
+      - https://tools.ietf.org/html/rfc791:
+      Total Length is the length of the datagram, measured in octets,
+      including internet header and data.
+      - checksum = 0 -> offset incorrect???
+      - ipv4 checksum is 0
+      - nat64 frame length = 98 bytes
+      - theory: ethernet: 48+48+16 = 112 bit -> 12 bytes
+      - nat64: 76 bytes inside ethernet frame
+      - nat64: 69 bytes according to total_len
+      - nat64: -5 bytes = icmp4 = 64 bytes
+      - icmp6 == 64 bytes
+      - diff of 7 bytes :-)
+      - icmp should be:
+      - type+code+checksum = 4 bytes
+      - seq + identifier = 4 bytes
+      - data = variable, source is 56 bytes
+      - real world ping: total_length = 84, 48 bytes icmp data
+      - header length in both cases = 5
+      - identification 0 in nat64, 0x2cad in real
+      - flags 0 in nat64, 0x4000 (DF) in real
+      - ttl = 64 both
+      - proto = icmp both cases
+      - header checksum = 0 in nat64, set in real
+      - data is shorter in nat64, due to total_len error
+      - real world icmp contains time stamp data ???
+      - wireshark EXPECTS timestamp data in echo request! + 8 bytes
+        and then data
+      - almost fits diff 7 vs. 8
+      - 8 bytes in one block in wireshark
+      - after ipv4: 6 + 8 + 3*(16) + 2 = 64 -- wtf??
+      - icmp6: data == 56 bytes
+      - nat64 and realping4 frame == 98 bytes
+
+
+
+
+****** TODO Correct IPv4 header checksum
+****** TODO Correct ICMP header checksum
+****** TODO Fix length issue
+       - Seems like total_len is too short - but why?
 **** DONE Add table name support in debug messages
 **** DONE Why getting IPv6 packets in
 INFO:main:unhandled reassambled=<Ether  dst=33:33:ff:00:00:42 src=00:00:0a:00:00:01 type=0x86dd |<IPv6  version=6 tc=0 fl=0 plen=32 nh=ICMPv6 hlim=255 src=fe80::200:aff:fe00:1 dst=ff02::1:ff00:42 |<ICMPv6ND_NS  type=Neighbor Solicitation code=0 cksum=0x37df res=0 tgt=2001:db8::42 |<ICMPv6NDOptSrcLLAddr  type=1 len=1 lladdr=00:00:0a:00:00:01 |>>>> from table TABLE_V6_NETWORKS

p4src/static-mapping.p4

@@ -77,8 +77,8 @@ control MyIngress(inout headers hdr,
 
         /* 5 is ok as long as we don't use options / padding /
         anything after the destination address */
-        hdr.ipv4.ihl            = (bit<4>) 5;                            // internet header length - static for us
-        hdr.ipv4.totalLen       = (bit<16>) hdr.ipv6.payload_length + 5; // ok under above constraints
+        hdr.ipv4.ihl            = (bit<4>) 5;                            // internet header length: 4*5 = 20
+        hdr.ipv4.totalLen       = (bit<16>) hdr.ipv6.payload_length + 20; // ok under above constraints
 
         hdr.ipv4.identification = (bit<16>) 0;                           // no support for fragments
         hdr.ipv4.flags          = (bit<3>)  0;                           // DF bit and more fragments, unsupported ATM