2
IFB is intended to replace IMQ.
3
Advantage over current IMQ; cleaner in particular in in SMP;
4
with a _lot_ less code.
9
As far as i know the reasons listed below is why people use IMQ.
10
It would be nice to know of anything else that i missed.
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1) qdiscs/policies that are per device as opposed to system wide.
13
IFB allows for sharing.
15
2) Allows for queueing incoming traffic for shaping instead of
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dropping. I am not aware of any study that shows policing is
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worse than shaping in achieving the end goal of rate control.
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I would be interested if anyone is experimenting.
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3) Very interesting use: if you are serving p2p you may wanna give
21
preference to your own localy originated traffic (when responses come back)
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vs someone using your system to do bittorent. So QoSing based on state
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comes in as the solution. What people did to achive this was stick
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the IMQ somewhere prelocal hook.
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I think this is a pretty neat feature to have in Linux in general.
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(i.e not just for IMQ).
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But i wont go back to putting netfilter hooks in the device to satisfy
28
this. I also dont think its worth it hacking ifb some more to be
29
aware of say L3 info and play ip rule tricks to achieve this.
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--> Instead the plan is to have a contrack related action. This action will
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selectively either query/create contrack state on incoming packets.
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Packets could then be redirected to ifb based on what happens -> eg
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on incoming packets; if we find they are of known state we could send to
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a different queue than one which didnt have existing state. This
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all however is dependent on whatever rules the admin enters.
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At the moment this 3rd function does not exist yet. I have decided that
38
instead of sitting on the patch for another year, to release it and then
39
if theres pressure i will add this feature.
41
An example, to provide functionality that most people use IMQ for below:
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$TC qdisc add dev ifb0 root handle 1: prio
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$TC qdisc add dev ifb0 parent 1:1 handle 10: sfq
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$TC qdisc add dev ifb0 parent 1:2 handle 20: tbf rate 20kbit buffer 1600 limit 3000
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$TC qdisc add dev ifb0 parent 1:3 handle 30: sfq
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$TC filter add dev ifb0 protocol ip pref 1 parent 1: handle 1 fw classid 1:1
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$TC filter add dev ifb0 protocol ip pref 2 parent 1: handle 2 fw classid 1:2
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$TC qdisc add dev eth0 ingress
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# redirect all IP packets arriving in eth0 to ifb0
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# use mark 1 --> puts them onto class 1:1
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$TC filter add dev eth0 parent ffff: protocol ip prio 10 u32 \
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match u32 0 0 flowid 1:1 \
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action ipt -j MARK --set-mark 1 \
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action mirred egress redirect dev ifb0
69
from another machine ping so that you have packets going into the box:
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[root@jzny action-tests]# ping 10.22
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PING 10.22 (10.0.0.22): 56 data bytes
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64 bytes from 10.0.0.22: icmp_seq=0 ttl=64 time=2.8 ms
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64 bytes from 10.0.0.22: icmp_seq=1 ttl=64 time=0.6 ms
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64 bytes from 10.0.0.22: icmp_seq=2 ttl=64 time=0.6 ms
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--- 10.22 ping statistics ---
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3 packets transmitted, 3 packets received, 0% packet loss
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round-trip min/avg/max = 0.6/1.3/2.8 ms
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[root@jzny action-tests]#
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Now look at some stats:
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[root@jmandrake]:~# $TC -s filter show parent ffff: dev eth0
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filter protocol ip pref 10 u32
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filter protocol ip pref 10 u32 fh 800: ht divisor 1
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filter protocol ip pref 10 u32 fh 800::800 order 2048 key ht 800 bkt 0 flowid 1:1
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match 00000000/00000000 at 0
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action order 1: tablename: mangle hook: NF_IP_PRE_ROUTING
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index 1 ref 1 bind 1 installed 4195sec used 27sec
93
Sent 252 bytes 3 pkts (dropped 0, overlimits 0)
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action order 2: mirred (Egress Redirect to device ifb0) stolen
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index 1 ref 1 bind 1 installed 165 sec used 27 sec
97
Sent 252 bytes 3 pkts (dropped 0, overlimits 0)
99
[root@jmandrake]:~# $TC -s qdisc
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qdisc sfq 30: dev ifb0 limit 128p quantum 1514b
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Sent 0 bytes 0 pkts (dropped 0, overlimits 0)
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qdisc tbf 20: dev ifb0 rate 20Kbit burst 1575b lat 2147.5s
103
Sent 210 bytes 3 pkts (dropped 0, overlimits 0)
104
qdisc sfq 10: dev ifb0 limit 128p quantum 1514b
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Sent 294 bytes 3 pkts (dropped 0, overlimits 0)
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qdisc prio 1: dev ifb0 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
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Sent 504 bytes 6 pkts (dropped 0, overlimits 0)
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qdisc ingress ffff: dev eth0 ----------------
109
Sent 308 bytes 5 pkts (dropped 0, overlimits 0)
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[root@jmandrake]:~# ifconfig ifb0
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ifb0 Link encap:Ethernet HWaddr 00:00:00:00:00:00
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inet6 addr: fe80::200:ff:fe00:0/64 Scope:Link
114
UP BROADCAST RUNNING NOARP MTU:1500 Metric:1
115
RX packets:6 errors:0 dropped:3 overruns:0 frame:0
116
TX packets:3 errors:0 dropped:0 overruns:0 carrier:0
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collisions:0 txqueuelen:32
118
RX bytes:504 (504.0 b) TX bytes:252 (252.0 b)
121
You send it any packet not originating from the actions it will drop them.
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[In this case the three dropped packets were ipv6 ndisc].
added
removed
doc/actions/ifb-README
