Help understanding iproute2 and tc scripts Post: 302552735

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Special Forums IP Networking Help understanding iproute2 and tc scripts Post 302552735 by shodg001 on Monday 5th of September 2011 10:09:08 AM

09-05-2011

Registered User

Help understanding iproute2 and tc scripts

Hi all,

I am new to linux routing and would like to keep a possible running dialog about some scripts I have been studying and what the different parts of them mean. We are using Openwrt backfire along with openvpn and Swyx as VoIP. My goal is to eventually implement some QoS using dsmark, but I want to understand what I am doing before I put anything into production.

Here is the first part of the script I have a question about:

# tc qdisc add dev eth0 handle ffff: ingress
# tc filter add dev eth0 parent ffff: protocol ip prop 1 u32 \ match ip protocol 17 0xff police rate 240kbit \ burst 15kb continue flowid :1

I think I comprehend everything except 'burst 15kb continue flowid :1'. What does that mean, and what is the point of it?

According to the author: opalsoft(.) net/qos/VoIP(.) htm

Our first ingress filter, priority 1, catchs UDP packets (UDP is protocol number 17) policing them up to 240kbits. Then we can manage with this 15 conversations of 16kbps each. Check your VoIP implementation to know the bandwidth requeriment per session and adjust your command according.

Now our valuable packets are in the outgoing queue *(What is the outgoing queue? out going as in the LAN side or WAN side?)*as fast as we can. For this side I suggest a prio queue to kick them asap to the outgoing interface (again which one is outgoing?); then something like this can help:

Here is the second part that is confusing:

# tc qdisc add dev eth1 root handle 1: prio
# tc filter add dev eth1 parent 1:0 protocol ip prio 1 \ handle 1 tcindex classid 1:1

Is this filter for stuff coming from the WAN to the LAN, the other way or both?
I am a bit confused on what constitutes ingress and egress. If the WAN (eth1) gets packets thats ingress, but then if eth1 sends the packets to eth0 (LAN) thats then egress?

Sorry to be long winded, but I think I need to chat a bit to work out all the stuff I read. Thank you in advance!

-Shawn

shodg001

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LEARN ABOUT SUNOS

tc-matchall

Match-all classifier in tc(8)					       Linux					     Match-all classifier in tc(8)

NAME

       matchall - traffic control filter that matches every packet

SYNOPSIS

       tc filter ... matchall [ skip_sw | skip_hw  ] [ action ACTION_SPEC ] [ classid CLASSID ]

DESCRIPTION

       The matchall filter allows to classify every packet that flows on the port and run a action on it.

OPTIONS

       action ACTION_SPEC
	      Apply an action from the generic actions framework on matching packets.

       classid CLASSID
	      Push matching packets into the class identified by CLASSID.

       skip_sw
	      Do  not  process filter by software. If hardware has no offload support for this filter, or TC offload is not enabled for the inter-
	      face, operation will fail.

       skip_hw
	      Do not process filter by hardware.

EXAMPLES

       To create ingress mirroring from port eth1 to port eth2:

	      tc qdisc	add dev eth1 handle ffff: ingress
	      tc filter add dev eth1 parent ffff:	    
		      matchall skip_sw			    
		      action mirred egress mirror	    
		      dev eth2

       The first command creats an ingress qdisc with handle ffff: on device eth1 where the second command attaches a matchall filters on it  that
       mirrors the packets to device eth2.

       To create egress mirroring from port eth1 to port eth2:

	      tc qdisc add dev eth1 handle 1: root prio
	      tc filter add dev eth1 parent 1:		     
		      matchall skip_sw			     
		      action mirred egress mirror	     
		      dev eth2

       The  first  command  creats  an egress qdisc with handle 1: that replaces the root qdisc on device eth1 where the second command attaches a
       matchall filters on it that mirrors the packets to device eth2.

       To sample one of every 100 packets flowing into interface eth0 to psample group 12:

	      tc qdisc add dev eth0 handle ffff: ingress
	      tc filter add dev eth0 parent ffff: matchall 
		   action sample rate 100 group 12

SEE ALSO

       tc(8),

iproute2							    21 Oct 2015 				     Match-all classifier in tc(8)

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