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Get rid of negative wrap around

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Nico Schottelius 2019-07-16 13:05:13 +02:00
commit bc90421426
2 changed files with 30 additions and 5 deletions
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21
p4src/actions_delta_checksum.p4
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@ -53,16 +53,29 @@ action delta_prepare()
action delta_udp_from_v4_to_v6()
{
delta_prepare();
// hdr.udp.checksum = meta.v6sum;
// hdr.udp.checksum = meta.v4sum;
hdr.udp.checksum = hdr.udp.checksum + meta.v6sum;
hdr.udp.checksum = hdr.udp.checksum - meta.v4sum;
/* prevent negative wrap around that loses 1 */
if(meta.v4sum > hdr.udp.checksum) {
bit<16> tmp = 0xffff - meta.v4sum;
hdr.udp.checksum = hdr.udp.checksum + tmp;
} else {
hdr.udp.checksum = hdr.udp.checksum - meta.v4sum;
}
}
action delta_tcp_from_v4_to_v6()
{
delta_prepare();
hdr.tcp.checksum = hdr.tcp.checksum + meta.v6sum - meta.v4sum;
hdr.tcp.checksum = hdr.tcp.checksum + meta.v6sum;
/* prevent negative wrap around that loses 1 */
if(meta.v4sum > hdr.tcp.checksum) {
bit<16> tmp = 0xffff - meta.v4sum;
hdr.tcp.checksum = hdr.tcp.checksum + tmp;
} else {
hdr.tcp.checksum = hdr.tcp.checksum - meta.v4sum;
}
}
action delta_ipv4_from_v6_to_v4()