Jarek Poplawski a écrit :

On 31-08-2009 22:58, Mark Smith wrote:

quoted

On Mon, 31 Aug 2009 21:54:49 +0200
Eric Dumazet [off-list ref] wrote:

quoted

Christoph Lameter a écrit :

quoted

This is with 2.6.31-rc7. If I send icmp then its correctly registered as a
packet by the qdisc layer:

<snip>

quoted

loopback device do bypass qdisc layer for example...

On occassion, I'd have found it useful if it didn't. It'd be convenient
to test out your qdisc config, or test out applications performance
behaviour over a simulated WAN via netem, without having to a
network and two hosts, and all the related miscellaneous setup work.

Probably Eric and you mean something special, but generally a loopback
and some other virtuals bypass qdisc layer only with default qdisc.

Yes, I was referring to Christoph use, since on its machine, only
output from "tc -s -d qdisc" is about eth0


Mark, you can certainly do something like

# tc qdisc del dev lo root
# tc qdisc add dev lo root netem delay 100ms 10ms

# ping 127.0.0.1
PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.
2009/08/01 08:59:22.799 64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=204 ms
2009/08/01 08:59:23.804 64 bytes from 127.0.0.1: icmp_seq=2 ttl=64 time=208 ms
2009/08/01 08:59:24.801 64 bytes from 127.0.0.1: icmp_seq=3 ttl=64 time=204 ms
2009/08/01 08:59:25.808 64 bytes from 127.0.0.1: icmp_seq=4 ttl=64 time=209 ms

# tc -s -d qdisc show dev lo
qdisc netem 8001: root limit 1000 delay 100.0ms  10.0ms
 Sent 1764 bytes 18 pkt (dropped 0, overlimits 0 requeues 0)
 rate 0bit 0pps backlog 0b 0p requeues 0