Re: [patch net-next v6 00/11] net: sched: allow qdiscs to share filter block instances

On 1/5/18 4:09 PM, Jiri Pirko wrote:

From: Jiri Pirko <redacted>

Currently the filters added to qdiscs are independent. So for example if you
have 2 netdevices and you create ingress qdisc on both and you want to add
identical filter rules both, you need to add them twice. This patchset
makes this easier and mainly saves resources allowing to share all filters
within a qdisc - I call it a "filter block". Also this helps to save
resources when we do offload to hw for example to expensive TCAM.

So back to the example. First, we create 2 qdiscs. Both will share
block number 22. "22" is just an identification. If we don't pass any
block number, a new one will be generated by kernel:

$ tc qdisc add dev ens7 ingress block 22
                                ^^^^^^^^
$ tc qdisc add dev ens8 ingress block 22
                                ^^^^^^^^

Now if we list the qdiscs, we will see the block index in the output:

$ tc qdisc
qdisc ingress ffff: dev ens7 parent ffff:fff1 block 22
qdisc ingress ffff: dev ens8 parent ffff:fff1 block 22


To make is more visual, the situation looks like this:

   ens7 ingress qdisc                 ens7 ingress qdisc
          |                                  |
          |                                  |
          +---------->  block 22  <----------+

Unlimited number of qdiscs may share the same block.

Now we can add filter using the block index:

$ tc filter add block 22 protocol ip pref 25 flower dst_ip 192.168.0.0/16 action drop


Note we cannot use the qdisc for filter manipulations for shared blocks:

$ tc filter add dev ens8 ingress protocol ip pref 1 flower dst_ip 192.168.100.2 action drop
Error: Cannot work with shared block, please use block index.


We will see the same output if we list filters for ingress qdisc of
ens7 and ens8, also for the block 22:

$ tc filter show block 22
filter block 22 protocol ip pref 25 flower chain 0
filter block 22 protocol ip pref 25 flower chain 0 handle 0x1
...

$ tc filter show dev ens7 ingress
filter block 22 protocol ip pref 25 flower chain 0
filter block 22 protocol ip pref 25 flower chain 0 handle 0x1
...

$ tc filter show dev ens8 ingress
filter block 22 protocol ip pref 25 flower chain 0
filter block 22 protocol ip pref 25 flower chain 0 handle 0x1
...

I like the API and output shown here, but I am not getting that with the
patches.

In this example, I am using 42 for the block id:

$ tc qdisc show dev eth2
qdisc mq 0: root
qdisc pfifo_fast 0: parent :2 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1
1 1 1
qdisc pfifo_fast 0: parent :1 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1
1 1 1
qdisc ingress ffff: parent ffff:fff1 block 42

It allows me to add a filter using the device:
$ tc filter add dev eth2 ingress protocol ip pref 1 flower dst_ip
192.168.101.2 action drop
$  echo $?
0

And it modifies the shared block:
$  tc filter show block 42
filter pref 1 flower chain 0
filter pref 1 flower chain 0 handle 0x1
  eth_type ipv4
  dst_ip 192.168.100.2
  not_in_hw
	action order 1: gact action drop
	 random type none pass val 0
	 index 2 ref 1 bind 1

filter pref 1 flower chain 0 handle 0x2
  eth_type ipv4
  dst_ip 192.168.101.2
  not_in_hw
	action order 1: gact action drop
	 random type none pass val 0
	 index 3 ref 1 bind 1

filter pref 25 flower chain 0
filter pref 25 flower chain 0 handle 0x1
  eth_type ipv4
  dst_ip 192.168.0.0/16
  not_in_hw
	action order 1: gact action drop
	 random type none pass val 0
	 index 1 ref 1 bind 1

Notice the header does not give the 'filter block N protocol' part. I
don't get that using the device either (tc filter show dev eth2 ingress).

Something else I noticed is that I do not get an error message if I pass
an invalid block id:

$ tc filter show block 22
$ echo $?
0
$  tc qdisc show | grep block
qdisc ingress ffff: dev eth2 parent ffff:fff1 block 42