Dropping Multicast Traffic
In the default configuration, the X3522 adapter will forward all traffic to the host even if no
steering filter matching the traffic is present. When no matching filter is present, traffic is steered
to queue 0. This behavior differs from the X2 series adapter which will drop traffic not matching
any filter.
In environments where a lot of unsolicited traffic is forwarded to the adapter, it can be
undesirable to pass this up to the host because it leads to increased CPU load to process and
drop the traffic. In particular, ultra low latency layer 1 switches do not support IGMP snooping
and forward all multicast traffic. This section presents a method to configure an X3522 adapter
to drop unwanted UDP traffic at the adapter.
Inserting a UDP IPv4 Multicast Mismatch Filter
To prevent any UDP IPv4 multicast traffic arriving through interface
<interface>
reaching the
kernel, insert a filter to drop it. As root, use the following command:
ethtool -N <interface> flow-type udp4 dst-ip 224.0.0.0 m 15.255.255.255
action -1
where
<interface>
is the name of an X3522 interface. For example:
$ sudo ethtool -N enp2s0f0np0 flow-type udp4 dst-ip 224.0.0.0 m
15.255.255.255 action -1
Added rule with ID 255
Note: If this would exceed the maximum number of filters, an error message is output, and the filter is not
inserted. For example:
rmgr: Cannot find appropriate slot to insert rule
Cannot insert classification rule
Once this filter has been inserted, any UDP IPv4 multicast traffic arriving at the interface that
does not match another steering filter will be dropped at the adapter and the
port_rxdp_di_dropped_pkts
counter shown by
ethtool -S <interface>
will be
incremented.
The filter can be deleted using its ID to reference it. For example:
$ sudo ethtool -N enp2s0f0np0 delete 255
Chapter 5: Tuning
UG1523 (v1.0) October 18, 2022
Alveo X3522 User Guide
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