On devices that support TC U32 offloads, these flags enable a filter to be
added only to HW or only to SW. skip_sw and skip_hw are mutually exclusive
flags. By default without any flags, the filter is added to both HW and SW,
but no error checks are done in case of failure to add to HW.
With skip-sw, failure to add to HW is treated as an error.
Here is a sample script that adds 2 filters, one with skip_sw and the other
with skip_hw flag.
# add ingress qdisc
tc qdisc add dev p4p1 ingress
# enable hw tc offload.
ethtool -K p4p1 hw-tc-offload on
# add u32 filter with skip-sw flag.
tc filter add dev p4p1 parent ffff: protocol ip prio 99 \
handle 800:0:1 u32 ht 800: flowid 800:1 \
skip-sw \
match ip src 192.168.1.0/24 \
action drop
# add u32 filter with skip-hw flag.
tc filter add dev p4p1 parent ffff: protocol ip prio 99 \
handle 800:0:2 u32 ht 800: flowid 800:2 \
skip-hw \
match ip src 192.168.2.0/24 \
action drop
Signed-off-by: Sridhar Samudrala <sridhar.samudrala@intel.com>
Kernel code and interface.
--------------------------
* Compile time switches
There is only one, but very important, compile time switch.
It is not settable by "make config", but should be selected
manually and after a bit of thinking in <include/net/pkt_sched.h>
PSCHED_CLOCK_SOURCE can take three values:
PSCHED_GETTIMEOFDAY
PSCHED_JIFFIES
PSCHED_CPU
PSCHED_GETTIMEOFDAY
Default setting is the most conservative PSCHED_GETTIMEOFDAY.
It is very slow both because of weird slowness of do_gettimeofday()
and because it forces code to use unnatural "timeval" format,
where microseconds and seconds fields are separate.
Besides that, it will misbehave, when delays exceed 2 seconds
(f.e. very slow links or classes bounded to small slice of bandwidth)
To resume: as only you will get it working, select correct clock
source and forget about PSCHED_GETTIMEOFDAY forever.
PSCHED_JIFFIES
Clock is derived from jiffies. On architectures with HZ=100
granularity of this clock is not enough to make reasonable
bindings to real time. However, taking into account Linux
architecture problems, which force us to use artificial
integrated clock in any case, this switch is not so bad
for schduling even on high speed networks, though policing
is not reliable.
PSCHED_CPU
It is available only for alpha and pentiums with correct
CPU timestamp. It is the fastest way, use it when it is available,
but remember: not all pentiums have this facility, and
a lot of them have clock, broken by APM etc. etc.
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