| |
| Advantage over current IMQ; cleaner in particular in in SMP; |
| with a _lot_ less code. |
| Old Dummy device functionality is preserved while new one only |
| kicks in if you use actions. |
| |
| IMQ USES |
| -------- |
| As far as i know the reasons listed below is why people use IMQ. |
| It would be nice to know of anything else that i missed. |
| |
| 1) qdiscs/policies that are per device as opposed to system wide. |
| IMQ allows for sharing. |
| |
| 2) Allows for queueing incoming traffic for shaping instead of |
| dropping. I am not aware of any study that shows policing is |
| worse than shaping in achieving the end goal of rate control. |
| I would be interested if anyone is experimenting. |
| |
| 3) Very interesting use: if you are serving p2p you may wanna give |
| preference to your own localy originated traffic (when responses come back) |
| vs someone using your system to do bittorent. So QoSing based on state |
| comes in as the solution. What people did to achive this was stick |
| the IMQ somewhere prelocal hook. |
| I think this is a pretty neat feature to have in Linux in general. |
| (i.e not just for IMQ). |
| But i wont go back to putting netfilter hooks in the device to satisfy |
| this. I also dont think its worth it hacking ifb some more to be |
| aware of say L3 info and play ip rule tricks to achieve this. |
| --> Instead the plan is to have a contrack related action. This action will |
| selectively either query/create contrack state on incoming packets. |
| Packets could then be redirected to ifb based on what happens -> eg |
| on incoming packets; if we find they are of known state we could send to |
| a different queue than one which didnt have existing state. This |
| all however is dependent on whatever rules the admin enters. |
| |
| At the moment this function does not exist yet. I have decided instead |
| of sitting on the patch to release it and then if theres pressure i will |
| add this feature. |
| |
| What you can do with ifb currently with actions |
| -------------------------------------------------- |
| |
| Lets say you are policing packets from alias 192.168.200.200/32 |
| you dont want those to exceed 100kbps going out. |
| |
| tc filter add dev eth0 parent 1: protocol ip prio 10 u32 \ |
| match ip src 192.168.200.200/32 flowid 1:2 \ |
| action police rate 100kbit burst 90k drop |
| |
| If you run tcpdump on eth0 you will see all packets going out |
| with src 192.168.200.200/32 dropped or not |
| Extend the rule a little to see only the ones that made it out: |
| |
| tc filter add dev eth0 parent 1: protocol ip prio 10 u32 \ |
| match ip src 192.168.200.200/32 flowid 1:2 \ |
| action police rate 10kbit burst 90k drop \ |
| action mirred egress mirror dev ifb0 |
| |
| Now fire tcpdump on ifb0 to see only those packets .. |
| tcpdump -n -i ifb0 -x -e -t |
| |
| Essentially a good debugging/logging interface. |
| |
| If you replace mirror with redirect, those packets will be |
| blackholed and will never make it out. This redirect behavior |
| changes with new patch (but not the mirror). |
| |
| What you can do with the patch to provide functionality |
| that most people use IMQ for below: |
| |
| -------- |
| export TC="/sbin/tc" |
| |
| $TC qdisc add dev ifb0 root handle 1: prio |
| $TC qdisc add dev ifb0 parent 1:1 handle 10: sfq |
| $TC qdisc add dev ifb0 parent 1:2 handle 20: tbf rate 20kbit buffer 1600 limit 3000 |
| $TC qdisc add dev ifb0 parent 1:3 handle 30: sfq |
| $TC filter add dev ifb0 protocol ip pref 1 parent 1: handle 1 fw classid 1:1 |
| $TC filter add dev ifb0 protocol ip pref 2 parent 1: handle 2 fw classid 1:2 |
| |
| ifconfig ifb0 up |
| |
| $TC qdisc add dev eth0 ingress |
| |
| # redirect all IP packets arriving in eth0 to ifb0 |
| # use mark 1 --> puts them onto class 1:1 |
| $TC filter add dev eth0 parent ffff: protocol ip prio 10 u32 \ |
| match u32 0 0 flowid 1:1 \ |
| action ipt -j MARK --set-mark 1 \ |
| action mirred egress redirect dev ifb0 |
| |
| -------- |
| |
| |
| Run A Little test: |
| |
| from another machine ping so that you have packets going into the box: |
| ----- |
| [root@jzny action-tests]# ping 10.22 |
| PING 10.22 (10.0.0.22): 56 data bytes |
| 64 bytes from 10.0.0.22: icmp_seq=0 ttl=64 time=2.8 ms |
| 64 bytes from 10.0.0.22: icmp_seq=1 ttl=64 time=0.6 ms |
| 64 bytes from 10.0.0.22: icmp_seq=2 ttl=64 time=0.6 ms |
| |
| --- 10.22 ping statistics --- |
| 3 packets transmitted, 3 packets received, 0% packet loss |
| round-trip min/avg/max = 0.6/1.3/2.8 ms |
| [root@jzny action-tests]# |
| ----- |
| Now look at some stats: |
| |
| --- |
| [root@jmandrake]:~# $TC -s filter show parent ffff: dev eth0 |
| filter protocol ip pref 10 u32 |
| filter protocol ip pref 10 u32 fh 800: ht divisor 1 |
| filter protocol ip pref 10 u32 fh 800::800 order 2048 key ht 800 bkt 0 flowid 1:1 |
| match 00000000/00000000 at 0 |
| action order 1: tablename: mangle hook: NF_IP_PRE_ROUTING |
| target MARK set 0x1 |
| index 1 ref 1 bind 1 installed 4195sec used 27sec |
| Sent 252 bytes 3 pkts (dropped 0, overlimits 0) |
| |
| action order 2: mirred (Egress Redirect to device ifb0) stolen |
| index 1 ref 1 bind 1 installed 165 sec used 27 sec |
| Sent 252 bytes 3 pkts (dropped 0, overlimits 0) |
| |
| [root@jmandrake]:~# $TC -s qdisc |
| qdisc sfq 30: dev ifb0 limit 128p quantum 1514b |
| Sent 0 bytes 0 pkts (dropped 0, overlimits 0) |
| qdisc tbf 20: dev ifb0 rate 20Kbit burst 1575b lat 2147.5s |
| Sent 210 bytes 3 pkts (dropped 0, overlimits 0) |
| qdisc sfq 10: dev ifb0 limit 128p quantum 1514b |
| Sent 294 bytes 3 pkts (dropped 0, overlimits 0) |
| qdisc prio 1: dev ifb0 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1 |
| Sent 504 bytes 6 pkts (dropped 0, overlimits 0) |
| qdisc ingress ffff: dev eth0 ---------------- |
| Sent 308 bytes 5 pkts (dropped 0, overlimits 0) |
| |
| [root@jmandrake]:~# ifconfig ifb0 |
| ifb0 Link encap:Ethernet HWaddr 00:00:00:00:00:00 |
| inet6 addr: fe80::200:ff:fe00:0/64 Scope:Link |
| UP BROADCAST RUNNING NOARP MTU:1500 Metric:1 |
| RX packets:6 errors:0 dropped:3 overruns:0 frame:0 |
| TX packets:3 errors:0 dropped:0 overruns:0 carrier:0 |
| collisions:0 txqueuelen:32 |
| RX bytes:504 (504.0 b) TX bytes:252 (252.0 b) |
| ----- |
| |
| Dummy continues to behave like it always did. |
| You send it any packet not originating from the actions it will drop them. |
| [In this case the three dropped packets were ipv6 ndisc]. |
| |
| cheers, |
| jamal |