Drop counter

Owned by Tracy Yang (Unlicensed)
Mar 03, 2023
6 min read

Pica8 has added support for drop counter from PicOS version 2.7.2. This feature is useful in cases where we need to count the dropped packets. For this counter, we use rdbgc4 register to count the dropped packets.

    The command is:

ovs-vsctl set-rdbgc4 [TYPE]

TYPE value: rfldr; ripd4; ripd6; riphe6; vlandr

Default value: rfldr


Use the command below to display rdbgc4 setting.

 ovs-vsctl show-rdbgc4

 

The command below is used get drop statistics on a given port.

ovs-ofctl dump-drop br0 [PORT]

 

1. rdbgc4 drop counter values:

1)ovs-vsctl set-rdbgc4 rfldr

Setting the rdbgc4 value to rfldr will count the packets which are dropped by a drop action (actions=drop) flow in TCAM. Packets matching this flow are dropped and drop statistics are recorded in the drop counter.

Example:

ovs-vsctl add-br br0
ovs-vsctl add-port br0 te-1/1/9 vlan_mode=trunk tag=1  -- set Interface te-1/1/9 type=pica8
ovs-vsctl add-port br0 te-1/1/10 vlan_mode=trunk tag=1  -- set Interface te-1/1/10 type=pica8

Packets will match default drop flow without configuring flows.

admin@PicOS-OVS$ovs-ofctl dump-drop br0 9
PXST_DROP_STATS reply (OF1.4) (xid=0x2): 1 interfaces
  te-1/1/9(port 9):
      Statistics type in rdbgc4: rfldr
        Discarded  Packets.................10000
      Statistics type : ingress drop caused by congestion (bytes)
        Discarded  Octets..................0
      Statistics type : ingress drop caused by congestion (packets)
        Discarded  Packets.................0
      Statistics type : egress drop caused by congestion (bytes)
        Discarded  Octets..................0
      Statistics type : egress drop caused by congestion (packets)
        Discarded  Packets.................0
      Statistics type : ingress drop caused by flow-match (packets)
        Discarded  Packets.................10000

 

2) ovs-vsctl set-rdbgc4 vlandr

Count the packets whose tag doesn't match the ingress port’s VLAN ID.

Example:

ovs-vsctl add-port br0 te-1/1/9 vlan_mode=access tag=10  -- set Interface te-1/1/9 type=pica8
ovs-vsctl add-port br0 te-1/1/10 vlan_mode=trunk tag=1  -- set Interface te-1/1/10 type=pica8

add flow:

ovs-ofctl add-flow br0 in_port=9,actions=10

Send packets with vlan=199 to port 10 and check drop counter.

admin@PicOS-OVS$ovs-ofctl dump-drop br0 9
PXST_DROP_STATS reply (OF1.4) (xid=0x2): 1 interfaces
  te-1/1/9(port 9):
      Statistics type in rdbgc4: vlandr
        Discarded  Packets.................10000
      Statistics type : ingress drop caused by congestion (bytes)
        Discarded  Octets..................0
      Statistics type : ingress drop caused by congestion (packets)
        Discarded  Packets.................0
      Statistics type : egress drop caused by congestion (bytes)
        Discarded  Octets..................0
      Statistics type : egress drop caused by congestion (packets)
        Discarded  Packets.................0
      Statistics type : ingress drop caused by flow-match (packets)
        Discarded  Packets.................0

If modify flow actions=drop,after above steps,  ingress drop caused by flow-match will have  discarded packets statistics 10000.

3) ovs-vsctl set-rdbgc4 ripd4

Count the ipv4 packets which send to route table with VLAN CFI=set or TTL=0.

Example:

ovs-vsctl set-l2-mode true
ovs-vsctl set-l3-mode true
ovs-ofctl add-flow br0 table=251, dl_vlan=199,dl_dst=22:22:22:22:22:22,actions=normal
ovs-ofctl add-flow br0 table=252, ip,nw_dst=2.2.2.2,actions=set_field: 00:00:00:00:22:22-\>dl_dst,set_field:1999-\>vlan_vid,10

Send packets with dl_dst=22:22:22:22:22:22, dl_dst=22:11:11:11:11:11,dl_vlan=199,CFI=SET, nw_dst=2.2.2.2, nw_src=1.1.1.1 to port 10.

Check drop counter:

admin@PicOS-OVS$ovs-ofctl dump-drop br0 9
PXST_DROP_STATS reply (OF1.4) (xid=0x2): 1 interfaces
  te-1/1/9(port 9):
      Statistics type in rdbgc4: ripd4
        Discarded  Packets.................10000
      Statistics type : ingress drop caused by congestion (bytes)
        Discarded  Octets..................0
      Statistics type : ingress drop caused by congestion (packets)
        Discarded  Packets.................0
      Statistics type : egress drop caused by congestion (bytes)
        Discarded  Octets..................0
      Statistics type : egress drop caused by congestion (packets)
        Discarded  Packets.................0
      Statistics type : ingress drop caused by flow-match (packets)
        Discarded  Packets.................0

 

4) ovs-vsctl set-rdbgc4 ripd6

Count the ipv6 packets which send to route table with VLAN CFI=set or Hop=0.

Example:

ovs-vsctl set-l2-mode true
ovs-vsctl set-l3-mode true
ovs-ofctl add-flow br0 table=251,dl_vlan=199,dl_dst=22:22:22:22:22:22,actions=normal
ovs-ofctl add-flow br0 table=252,ipv6,ipv6_dst=2001::1,actions=set_field: 00:00:00:00:22:22-\>dl_dst,set_field:1999-\>vlan_vid,10

Send packets with dl_dst=22:22:22:22:22:22, dl_dst=22:11:11:11:11:11,dl_vlan=199,CFI=RESET, hop=0, ipv6_dst=2001::1,ipv6_src=2002::1 to port 10:

Check drop counter:

admin@PicOS-OVS$ovs-ofctl dump-drop br0 9
PXST_DROP_STATS reply (OF1.4) (xid=0x2): 1 interfaces
  te-1/1/9(port 9):
       Statistics type in rdbgc4: ripd6
        Discarded  Packets.................10000
      Statistics type : ingress drop caused by congestion (bytes)
        Discarded  Octets..................0
      Statistics type : ingress drop caused by congestion (packets)
        Discarded  Packets.................0
      Statistics type : egress drop caused by congestion (bytes)
        Discarded  Octets..................0
      Statistics type : egress drop caused by congestion (packets)
        Discarded  Packets.................0
      Statistics type : ingress drop caused by flow-match (packets)
        Discarded  Packets.................0

 

5) ovs-vsctl set-rdbgc4 riphe6

Count the ipv6 packets which send to route table with ipv6_dst=::

Example:

ovs-vsctl set-l2-mode true
ovs-vsctl set-l3-mode true
ovs-ofctl add-flow br0 table=251,dl_vlan=199,dl_dst=22:22:22:22:22:22,actions=normal
ovs-ofctl add-flow br0 table=252,ipv6,ipv6_dst=2001::1,actions=set_field:00:00:00:00:22:22-\>dl_dst,set_field:1999-\>vlan_vid,10

Send packets with dl_dst=22:22:22:22:22:22,dl_dst=22:11:11:11:11:11,dl_vlan=199, ipv6_dst=0::0,ipv6_src=2002::1

Check drop counter:

admin@PicOS-OVS$ovs-ofctl dump-drop br0 9
PXST_DROP_STATS reply (OF1.4) (xid=0x2): 1 interfaces
  te-1/1/9(port 9):
       Statistics type in rdbgc4: riphe6
        Discarded  Packets.................10000
      Statistics type : ingress drop caused by congestion (bytes)
        Discarded  Octets..................0
      Statistics type : ingress drop caused by congestion (packets)
        Discarded  Packets.................0
      Statistics type : egress drop caused by congestion (bytes)
        Discarded  Octets..................0
      Statistics type : egress drop caused by congestion (packets)
        Discarded  Packets.................0
      Statistics type : ingress drop caused by flow-match (packets)
        Discarded  Packets.................0

 

2.Congest drop counter:

Count packets which dropped because of congestion.

admin@PicOS-OVS$ovs-ofctl dump-drop br0 9
PXST_DROP_STATS reply (OF1.4) (xid=0x2): 1 interfaces
  te-1/1/9(port 9):
      Statistics type in rdbgc4: rfldr
        Discarded  Packets.................0
      Statistics type : ingress drop caused by congestion (bytes)
        Discarded  Octets..................0
      Statistics type : ingress drop caused by congestion (packets)
        Discarded  Packets.................0
      Statistics type : egress drop caused by congestion (bytes)
        Discarded  Octets..................22567715016
      Statistics type : egress drop caused by congestion (packets)
        Discarded  Packets.................331876187
      Statistics type : ingress drop caused by flow-match (packets)
        Discarded  Packets.................0

 

3.ingress drop counter:

the packets which dropped by the actions=drop flow in tcam.

Example：

ovs-ofctl add-flow br0 in_port=9,ip,dl_vlan=199,nw_dst=192.168.100.100,actions=drop

Send packets to match this flow and check drop counter:

admin@PicOS-OVS$ovs-ofctl dump-drop br0 9
PXST_DROP_STATS reply (OF1.4) (xid=0x2): 1 interfaces
  te-1/1/9(port 9):
    Statistics type in rdbgc4: vlandr
        Discarded  Packets.................0
      Statistics type : ingress drop caused by congestion (bytes)
        Discarded  Octets..................0
      Statistics type : ingress drop caused by congestion (packets)
        Discarded  Packets.................0
      Statistics type : egress drop caused by congestion (bytes)
        Discarded  Octets..................0
      Statistics type : egress drop caused by congestion (packets)
        Discarded  Packets.................0
      Statistics type : ingress drop caused by flow-match (packets)
        Discarded  Packets.................10000

1.Drop counter only works in ingress,but when congest statistics is in egress.

2.User can use following command to clear statistics：

ovs-appctl bridge/clear-counts br0

 

 

 

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