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Back to 16 bit arithmetic

This commit is contained in:
Nico Schottelius 2019-07-16 12:06:26 +02:00
parent 428faead17
commit ecab110d7c
3 changed files with 54 additions and 56 deletions
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19
doc/plan.org
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@ -5309,6 +5309,25 @@ This is used to correct endianness!
-> not needed in our case -> not needed in our case
*** TODO 2019-07-16: Wraptest in P4
#+BEGIN_CENTER
mx h3
arp -s 10.0.0.2 00:00:0a:00:00:02
echo V4-OK | socat - TCP:10.0.0.2:2342
#+END_CENTER
Result on the wire of the wraptest:
#+BEGIN_CENTER
10.0.0.3.60106 > 10.0.0.2.2342: Flags [S], cksum 0x0001 (incorrect ->
0xc7f9), seq 3677403557, win 28380, options [mss 9460
,sackOK,TS val 2328087128 ecr 0,nop,wscale 9], length 0
#+END_CENTER
0xffff + 2 = 1
-> as expected
Thus carryover is already implemented. Try to use 16 bit ints
** The NetPFGA saga ** The NetPFGA saga
Problems encountered: Problems encountered:
- The logfile for a compile run is 10k+ lines - The logfile for a compile run is 10k+ lines

89
p4src/actions_delta_checksum.p4
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@ -2,95 +2,74 @@
#define NICO_DELTA_CHECKSUM #define NICO_DELTA_CHECKSUM
action v4sum() { action v4sum() {
bit<32> tmp = 0; bit<16> tmp = 0;
bit<32> carryover = 0;
tmp = tmp + (bit<32>) hdr.ipv4.src_addr[15:0]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv4.src_addr[15:0]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv4.src_addr[31:16]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv4.src_addr[31:16]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv4.dst_addr[15:0]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv4.dst_addr[15:0]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv4.dst_addr[31:16]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv4.dst_addr[31:16]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv4.totalLen -20; // 16 bit tmp = tmp + (bit<16>) hdr.ipv4.totalLen -20; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv4.protocol; // 8 bit tmp = tmp + (bit<16>) hdr.ipv4.protocol; // 8 bit
/* filtering code copied from scapy */
tmp = (tmp >> 16) + (tmp & 0xffff);
tmp = (tmp >> 16) + (tmp & 0xffff);
tmp = ~tmp; tmp = ~tmp;
// meta.v4sum = (bit<16>) ((((tmp>>8) & 0xff)|tmp<<8) & 0xffff); meta.v4sum = tmp;
meta.v4sum = (bit<16>) tmp;
} }
action v6sum() { action v6sum() {
bit<32> tmp = 0; bit<16> tmp = 0;
bit<32> carryover = 0;
tmp = tmp + (bit<32>) hdr.ipv6.src_addr[15:0]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv6.src_addr[15:0]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv6.src_addr[31:16]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv6.src_addr[31:16]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv6.src_addr[47:32]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv6.src_addr[47:32]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv6.src_addr[63:48]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv6.src_addr[63:48]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv6.src_addr[79:64]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv6.src_addr[79:64]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv6.src_addr[95:80]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv6.src_addr[95:80]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv6.src_addr[111:96]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv6.src_addr[111:96]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv6.src_addr[127:112]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv6.src_addr[127:112]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv6.dst_addr[15:0]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv6.dst_addr[15:0]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv6.dst_addr[31:16]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv6.dst_addr[31:16]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv6.dst_addr[47:32]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv6.dst_addr[47:32]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv6.dst_addr[63:48]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv6.dst_addr[63:48]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv6.dst_addr[79:64]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv6.dst_addr[79:64]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv6.dst_addr[95:80]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv6.dst_addr[95:80]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv6.dst_addr[111:96]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv6.dst_addr[111:96]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv6.dst_addr[127:112]; // 16 bit tmp = tmp + (bit<16>) hdr.ipv6.dst_addr[127:112]; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv6.payload_length; // 16 bit tmp = tmp + (bit<16>) hdr.ipv6.payload_length; // 16 bit
tmp = tmp + (bit<32>) hdr.ipv6.next_header; // 8 bit tmp = tmp + (bit<16>) hdr.ipv6.next_header; // 8 bit
/* filtering code copied from scapy */
tmp = (tmp >> 16) + (tmp & 0xffff);
tmp = (tmp >> 16) + (tmp & 0xffff);
// tmp = tmp + (tmp >> 16);
tmp = ~tmp; tmp = ~tmp;
meta.v6sum = tmp;
meta.v6sum = (bit<16>) tmp;
} }
action delta_prepare() action delta_prepare()
{ {
v4sum(); v4sum();
v6sum(); v6sum();
if(meta.v6sum > meta.v4sum) {
meta.headerdiff = meta.v6sum - meta.v4sum;
} else {
meta.headerdiff = meta.v4sum - meta.v6sum;
}
} }
action delta_udp_from_v4_to_v6() action delta_udp_from_v4_to_v6()
{ {
v4sum(); delta_prepare();
v6sum();
/* here is also a possible overflow in both directions */
hdr.udp.checksum = hdr.udp.checksum + meta.v6sum - meta.v4sum; hdr.udp.checksum = hdr.udp.checksum + meta.v6sum - meta.v4sum;
} }
action delta_tcp_from_v4_to_v6() action delta_tcp_from_v4_to_v6()
{ {
v4sum(); delta_prepare();
v6sum();
/* here is also a possible overflow in both directions */
hdr.tcp.checksum = hdr.tcp.checksum + meta.v6sum - meta.v4sum; hdr.tcp.checksum = hdr.tcp.checksum + meta.v6sum - meta.v4sum;
} }
action delta_ipv4_from_v6_to_v4() action delta_ipv4_from_v6_to_v4()
{ {
delta_prepare(); delta_prepare();
/* TO BE DONE! */
/* we don't have ANY checksum, but tcp or udp: we can
base on that ones for calculating the diff for IPv4
*/
hdr.ipv4.checksum = 0; /* TO BE DONE! */
} }

2
p4src/headers.p4
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@ -100,7 +100,7 @@ header ipv4_t {
bit<13> fragOffset; bit<13> fragOffset;
bit<8> ttl; bit<8> ttl;
bit<8> protocol; bit<8> protocol;
bit<16> hdrChecksum; bit<16> checksum;
ipv4_addr_t src_addr; ipv4_addr_t src_addr;
ipv4_addr_t dst_addr; ipv4_addr_t dst_addr;
} }