Rate limiting not happening for ARP

[mfriyas]

Issue Description:-

               ARP rate limiting to CPU in dell platforms was set as 600 in copp.config.json .

Am sending arp request from ixia to sonic with more than 600 pps secs. Sonic device not dropping the packets when it reaches the rate-limit as 600. it processes all the packets to the cpu and gave arp reply to ixia .This happens when am increases the ixia stream to 1000pps,2000pps,5000pps,7000pps,10000pps. For all this scenarios rate-limiting not works as expected.

JSON output from swss container:-

{
"COPP_TABLE:trap.group.arp": {
"trap_ids": "arp_req,arp_resp,neigh_discovery",
"trap_action":"copy",
"trap_priority":"4",
"queue": "4",
"meter_type":"packets",
"mode":"sr_tcm",
"cir":"600",
"cbs":"600",
"red_action":"drop"
},
"OP": "SET"
},

Device outputs:-

1500 pps

root@sonic-z9264f-04:/home/admin# bcmcmd "show c" | grep "cpu"
PERQ_PKT(4).cpu0 : 57,060,468 +1,725 1,493/s
PERQ_BYTE(4).cpu0 : 3,880,111,824 +117,300 101,526/s
root@sonic-z9264f-04:/home/admin#

2500 pps

root@sonic-z9264f-04:/home/admin# bcmcmd "show c" | grep "cpu"
PERQ_PKT(4).cpu0 : 57,121,736 +61,268 2,500/s
PERQ_BYTE(4).cpu0 : 3,884,278,048 +4,166,224 170,004/s

5000 pps

root@sonic-z9264f-04:/home/admin# bcmcmd "show c" | grep "cpu"
PERQ_PKT(4).cpu0 : 57,243,989 +5,794 5,026/s
PERQ_BYTE(4).cpu0 : 3,892,591,252 +393,992 341,760/s

7000 pps

root@sonic-z9264f-04:/home/admin# bcmcmd "show c" | grep "cpu"
PERQ_PKT(4).cpu0 : 57,425,961 +17,120 7,003/s
PERQ_BYTE(4).cpu0 : 3,904,965,348 +1,164,160 476,190/s
root@sonic-z9264f-04:/home/admin#

10000 pps

root@sonic-z9264f-04:/home/admin# bcmcmd "show c" | grep "cpu"
PERQ_PKT(4).cpu0 : 57,666,198 +240,237 10,203/s
PERQ_BYTE(4).cpu0 : 3,921,301,464 +16,336,116 693,784/s

[bryantkwu]

I think this is a problem with broadcom SAI.
When I enter bcmsh, and add some actions to the FP rule of ARP, for example:
“fp action add 0x7 YpDrop” and “fp action add 0x7 GpCopyToCpu”, and then reinstall.
After that the function will be normal.