netdev - Re: RED tc qdisc not dropping?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 03 Oct 2012 23:12:46 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ken Savage <kens1835@...w.ca>
Cc:	netdev@...r.kernel.org
Subject: Re: RED tc qdisc not dropping?

On Wed, 2012-10-03 at 14:14 -0600, Ken Savage wrote:
> Hi there,
> 
> I'm running openSUSE 12.2, using the machine as a router/WANsim device.
> 
> Previously, I was running an older CentOS installation with a 2.6 kernel,
> and my tc-red commands ran just fine, and imposed some bandwidth constraint
> to the packets upon egress.  In 3.4.6, this doesn't seem to be the case
> any longer.
> 
> Without any restrictions, there would be 25-30Mbps of traffic flowing out
> the interface -- this is to give you a sense of the data rate.
> 
> 
> Now, this said, I did notice that the latest RED code has the 'harddrop'
> option that I didn't have under CentOS with kernel 2.6.  So in my attempt
> to see ANYTHING happening with 3.4.6, I entered:
> 
> tc qdisc add dev eth0 root red limit 40000 min 3000 max 9000 avpkt 1000 burst 5 harddrop probability 1
> 
> 
> Issuing 'tc -s -d qdisc show dev eth0', I obtain:
> 
> qdisc red 8006: root refcnt 2 limit 40000b min 3000b max 9000b harddrop ewma 2 probability 0.73242 Scell_log 12
>  Sent 254028472 bytes 207494 pkt (dropped 0, overlimits 0 requeues 0)
>  backlog 0b 0p requeues 0
>   marked 0 early 0 pdrop 0 other 0
> 
> 
> All those zeroes seem a little amiss to me  ;)
> 

Not sure I understand...

Why RED should drop a packet if there is no backlog ?

if you NIC has Gigabit speed, RED will allow Gigabit speed as well.



--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html