These filters reside in the card's memory instead of its TCAM and can be
configured via a new "hashfilter" subcommand in cxgbetool. Hash and
normal TCAM filters can be used together. The hardware does an
exact-match of packet fields for hash filters, unlike the masked match
performed for TCAM filters. Any T5/T6 card with memory can support at
least half a million hash filters. The sample config file with the
driver configures 512K of these, it is possible to double this to 1
million+ in some cases.
The chip does an exact-match of fields of incoming datagrams with hash
filters and performs the action configured for the filter if it matches.
The fields to match are specified in a "filter mask" in the firmware
config file. The filter mask always includes the 5-tuple (sip, dip,
sport, dport, ipproto). It can, optionally, also include any subset of
the filter mode (see filterMode and filterMask in the firmware config
file).
For example:
filterMode = fragmentation, mpshittype, protocol, vlan, port, fcoe
filterMask = protocol, port, vlan
Exact values of the 5-tuple, the physical port, and VLAN tag would have
to be provided while setting up a hash filter with the chip
configuration above.
Hash filters support all actions supported by TCAM filters. A packet
that hits a hash filter can be dropped, let through (with optional
steering to a specific queue or RSS region), switched out of another
port (with optional L2 rewrite of DMAC, SMAC, VLAN tag), or get NAT'ed.
(Support for some of these will show up in the driver in a follow-up
commit very shortly).
Sponsored by: Chelsio Communications
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