[sflow + dropmon] added the ENABLE_SFLOW_DROPMON build flag. Added patches for sflow repo.

[vadymhlushko-mlnx]

DEPENDS ON: sonic-linux-kernel/pull/276, sonic-linux-kernel/pull/281, sonic-linux-kernel/pull/284

Why I did it

Added a capability of monitoring dropped packets for the sFlow daemon in order to improve network - monitoring, diagnostic, and troubleshooting. The drop monitor service allows the sFlow daemon to export another type of sample - dropped packets as Discard samples alongside Counter samples and Packet Flow samples.

How I did it

Added the SONiC build flag - ENABLE_SFLOW_DROPMON which will allow compile the hsflowd daemon with the dropmon kernel module.

How to verify it

1. Burn an image with the ENABLE_SFLOW_DROPMON=y flag to the switch.
2. 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

3. Configure the Host (PTF)

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

4. Launch the sflowtool on Host (PTF)

sflowtool -J -p 6343 > drop_packets_1k

5. 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)

6. 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

7. 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

Description for the changelog

Link to config_db schema for YANG module changes

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

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

• 201811
• 201911
• 202006
• 202012
• 202106
• 202111

Description for the changelog

Link to config_db schema for YANG module changes

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

[prsunny]

@padmanarayana, @jeff-yin, could someone review?

[vadymhlushko-mlnx]

/azpw run Azure.sonic-buildimage

[mssonicbld]

/AzurePipelines run Azure.sonic-buildimage

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[liat-grozovik]

@padmanarayana, @jeff-yin kindly reminder to review.

[vadymhlushko-mlnx]

/azpw run Azure.sonic-buildimage

[mssonicbld]

/AzurePipelines run Azure.sonic-buildimage

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[jeff-yin]

Latest comments (discussed in e-mail):

It’s not clear if the Discard samples are counted against the flow samples (whose rate is specified by “sample-rate” option in the CLI).
Also, the HLD may need an update.

@prsunny to schedule a call with @vadymhlushko-mlnx and @padmanarayana to clarify/discuss.

[vadymhlushko-mlnx]

Latest comments (discussed in e-mail):

It’s not clear if the Discard samples are counted against the flow samples (whose rate is specified by “sample-rate” option in the CLI).
Also, the HLD may need an update.

@prsunny to schedule a call with @vadymhlushko-mlnx and @padmanarayana to clarify/discuss.

The sample-rate option could only configure FLOWSAMPLE samples and has nothing to do with DISCARD samples.

For now, there is no CLI for DISCARD samples, the only way to configure something for them is to use the next instruction:

1. Disable a sFlow
   root@sonic:/home/admin# config sflow disable
2. Go to the sflow docker container
   root@sonic:/home/admin# docker exec -it sflow bash
3. Mannually edit the /etc/hsflowd.conf file
   For example, there is a line in /etc/hsflowd.conf

dropmon { group=1 start=on limit=1000 max=10000 hw=on sw=on }

The user could change the

limit [number] - a number that determines how many dropped packets per second could process the dropmon kernel module
max [number] - a number that determines the buffer in the kernel for dropped packets.
hw [on/off] - a flag that enables or disables the interception process of packets that were dropped by the switch ASIC
sw [on/off] - a flag that enables or disables the interception process of packets that were dropped by the Linux kernel stack

4. Exit the sflow docker and execute sflow enable command in order to apply the changes
   root@sonic:/home/admin# config sflow enable

[vadymhlushko-mlnx]

@padmanarayana, @jeff-yin, kind reminder to review

[padmanarayana]

Thanks for the clarifications!

[jeff-yin]

Approved -- please seek additional approval from a reviewer with write access to the repo. Thanks!

[vadymhlushko-mlnx]

@prsunny could you please merge?

[vadymhlushko-mlnx]

@prsunny could you please merge?

kind reminder