Get rid of negative wrap around

2019-07-16 13:05:13 +02:00 · 2019-07-16 13:05:13 +02:00 · bc90421426
commit bc90421426
parent e74a18c102
2 changed files with 30 additions and 5 deletions
--- a/doc/plan.org
+++ b/doc/plan.org
@ -5335,8 +5335,20 @@ 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: v6sum, v4sum
+*** TODO 2019-07-16: get values from P4: v6sum, v4sum and co.
    - v6sum = 0x9a6b
+    - v4sum = 0xeadd
+
+    - 0x4a8a + 0x9a6b = 0xe4f5 (same as python)
+    (code: hdr.udp.checksum = 0x4a8a + 0x9a6b)
+
+    - hdr.udp.checksum = 0x4a8a + 0x9a6b - 0xeadd;
+    ../p4src/actions_delta_checksum.p4(58): warning: -1512: negative
+    value with unsigned type
+    hdr.udp.checksum = 0x4a8a + 0x9a6b - 0xeadd;
+    Result: 0xfa18!
+
+

 ** The NetPFGA saga
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