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Change order of complement & filtering

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Nico Schottelius 2019-07-15 16:20:51 +02:00
commit 26c27cefa8
3 changed files with 25 additions and 13 deletions
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24
p4src/actions_delta_checksum.p4
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@ -13,13 +13,12 @@ action v4sum() {
tmp = tmp + (bit<32>) hdr.ipv4.totalLen -20; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv4.protocol; // 8 bit
carryover = tmp >> 16; /* maximum is 6*(2**16) >> 16 == 6 */
tmp = (tmp & 0xffff) + carryover; /* Now tmp contains at maximum 65541 */
carryover = tmp >> 16; /* Now carryover contains at maximum 1 */
tmp = tmp + carryover; /* No overrun possible anymore */
/* filtering code copied from scapy */
meta.v4sum = (bit<16>) ((((tmp>>8) & 0xff)|tmp<<8) & 0xffff) ;
tmp = (tmp >> 16) + (tmp & 0xffff);
tmp = tmp + (tmp >> 16);
tmp = ~tmp;
meta.v4sum = (bit<16>) ((((tmp>>8) & 0xff)|tmp<<8) & 0xffff);
}
action v6sum() {
@ -47,15 +46,14 @@ action v6sum() {
tmp = tmp + (bit<32>) hdr.ipv6.payload_length; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv6.next_header; // 8 bit
carryover = tmp >> 16; /* maximum is 18*(2**16) >> 16 == 18 */
tmp = (tmp & 0xffff) + carryover; /* Now tmp contains at maximum 65554*/
carryover = tmp >> 16; /* Now carryover contains at maximum 1 */
tmp = tmp + carryover; /* No overrun possible anymore */
/* filtering code copied from scapy */
tmp = (tmp >> 16) + (tmp & 0xffff);
tmp = tmp + (tmp >> 16);
tmp = ~tmp;
meta.v6sum = (bit<16>) ((((tmp>>8) & 0xff)|tmp<<8) & 0xffff) ;
}
action delta_prepare()
{
v4sum();
@ -70,13 +68,13 @@ action delta_prepare()
action delta_udp_from_v4_to_v6()
{
delta_prepare();
hdr.udp.checksum = hdr.udp.checksum + ~meta.headerdiff;
hdr.udp.checksum = hdr.udp.checksum + meta.headerdiff;
}
action delta_tcp_from_v4_to_v6()
{
delta_prepare();
hdr.tcp.checksum = hdr.tcp.checksum + ~meta.headerdiff;
hdr.tcp.checksum = hdr.tcp.checksum + meta.headerdiff;
}
action delta_ipv4_from_v6_to_v4()