internal [202305][sflow]: Remove the ENABLE_SFLOW_DROPMON flag

[vadymhlushko-mlnx]

Why I did it

To simplify usability and increase adoption of the sFlow + dropmon feature without rebuilding an image.

Work item tracking

• Microsoft ADO (number only):

How I did it

Remove the ENABLE_SFLOW_DROPMON compilation flag, and remove unnecessary patches.

How to verify it

1. Configure the sFlow on the switch

root@sonic:/home/admin# config feature state sflow enabled
root@sonic:/home/admin# config sflow enable
root@sonic:/home/admin# config sflow collector add collector0 30.1.1.2 --port 6343
root@sonic:/home/admin# config sflow polling-interval 20
root@sonic:/home/admin# config sflow interface disable all
root@sonic:/home/admin# config sflow interface enable Ethernet4
root@sonic:/home/admin# config sflow interface sample-rate Ethernet4 256

2. Configure the Host (PTF)

root@a8f0f3e20879:/# ifconfig eth1 30.1.1.2/24
root@a8f0f3e20879:/# ifconfig eth2 40.1.1.2/24

3. Launch the sflowtool on Host (PTF)

sflowtool -J -p 6343 > drop_packets_1k

4. Send the dropped packets from Host (PTF) to the switch via scapy

root@a8f0f3e20879:/# scapy
Welcome to Scapy (2.2.0-dev)
>>> pkt_nok = Ether(src="00:00:00:00:00", dst="SWITCH_MAC_address")/IP(src="0.0.0.0", dst="40.1.1.5")/TCP()
>>> sendp(pkt_nok, iface="eth2", count=1000)

5. Check the L3 counters on the switch

root@sonic:/home/admin# show interfaces counters rif
         IFACE    RX_OK      RX_BPS    RX_PPS    RX_ERR    TX_OK    TX_BPS    TX_PPS    TX_ERR
--------------  -------  ----------  --------  --------  -------  --------  --------  --------
     Ethernet2       24  459.32 B/s    0.82/s         1        0  0.00 B/s    0.00/s         0
     Ethernet4        0    0.00 B/s    0.00/s     1,000        0  0.00 B/s    0.00/s         0

6. Check the samples that were captured by the sflowtool on the Host (PTF)

root@a8f0f3e20879:/# cat drop_packets_1k
...
  {
   "sampleType_tag":"0:5",
   "sampleType":"DISCARD",
   "sampleSequenceNo":"309",
   "sourceId":"0:127",
   "dropEvents":"32",
   "inputPort":"127",
   "outputPort":"0",
   "discardCode":"285",
   "discardReason":"unknown_l3",
   "elements":[{
     "discarded_flowBlock_tag":"0:1038",
     "discarded_extendedType":"function",
     "discarded_symbol":"ip_rcv_finish_core.constprop.0+0x1c4/0x"
    },
    {
     "discarded_flowBlock_tag":"0:1",
     "discarded_flowSampleType":"HEADER",
     "discarded_headerProtocol":"1",
     "discarded_sampledPacketSize":"54",
     "discarded_strippedBytes":"4",
     "discarded_headerLen":"54",
     "discarded_headerBytes":"98-03-9B-94-D4-80-00-00-00-00-00-00-08-00-45-00-00-28-00-01-00-00-40-06-51-CA-00-00-00-00-28-01-01-05-00-14-00-50-00-00-00-00-00-00-00-00-50-02-20-00-66-79-00-00",
     "discarded_dstMAC":"98039b94d480",
     "discarded_srcMAC":"000000000000",
     "discarded_IPSize":"36",
     "discarded_ip.tot_len":"40",
     "discarded_srcIP":"0.0.0.0",
     "discarded_dstIP":"40.1.1.5",
     "discarded_IPProtocol":"6",
     "discarded_IPTOS":"0",
     "discarded_IPTTL":"64",
     "discarded_IPID":"256",
     "discarded_TCPSrcPort":"20",
     "discarded_TCPDstPort":"80",
     "discarded_TCPFlags":"2"
    }
   ]
  }

Which release branch to backport (provide reason below if selected)

• 201811
• 201911
• 202006
• 202012
• 202106
• 202111
• 202205
• 202211
• 202305

Tested branch (Please provide the tested image version)

Description for the changelog

Link to config_db schema for YANG module changes

A picture of a cute animal (not mandatory but encouraged)