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update checksum code

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Nico Schottelius 2019-07-17 15:46:54 +02:00
commit 512fca1349
2 changed files with 47 additions and 15 deletions
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@ -4596,7 +4596,6 @@ Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: Windo
#+END_CENTER
Reason was a hidden window.
***
*** 2019-06-13: try using external card for packets
*** 2019-06-14: test adding table entry with ubuntu 16.04, kernel 4.15.0-51-generic
#+BEGIN_CENTER
@ -5301,6 +5300,8 @@ p4@ubuntu:~/master-thesis/bin$ mx h3 "echo V4-OK | socat - UDP:10.1.1.1:2342"
My code is +1 too high
*** 2019-07-17: continuing on wrap around issue
*** DONE 2019-07-16: understood scapy code
CLOSED: [2019-07-16 Tue 11:25]
meta.v6sum = (bit<16>) ((((tmp>>8) & 0xff)|tmp<<8) & 0xffff) ;
@ -5335,7 +5336,8 @@ Gives off-by-one in udp, sometimes!
10:08:52.626713 IP6 (hlim 64, next-header UDP (17) payload length: 14) 2001:db8:1::a00:1.51345 > 2001:db8::1.2342: [bad udp cks
*** TODO 2019-07-16: get values from P4: v6sum, v4sum and co.
*** DONE 2019-07-16: get values from P4: v6sum, v4sum and co.
CLOSED: [2019-07-16 Tue 13:15]
- v6sum = 0x9a6b
- v4sum = 0xeadd
@ -5348,7 +5350,12 @@ Gives off-by-one in udp, sometimes!
hdr.udp.checksum = 0x4a8a + 0x9a6b - 0xeadd;
Result: 0xfa18!
*** TODO 2019-07-16: debug v3.3: even positive wrap around fails!!
- hdr.udp.checksum = 0x91ef + 0x9a6b;
../p4src/actions_delta_checksum.p4(66): warning: 76890: value does not fit in 16 bits
hdr.udp.checksum = 0x91ef + 0x9a6b;
11:52:13.177826 IP6 (hlim 64, next-header UDP (17) payload length: 14)
2001:db8:1::a00:1.50705 > 2001:db8::1.2342: [bad udp cksum 0x2c5a -> 0xfc97!] UDP, length 6
** The NetPFGA saga
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