Fixes byte backlog accounting for the first of two chained netem instances.
Bytes backlog reported now corresponds to the number of queued packets.
When two netem instances are chained, for instance to apply rate and queue
limitation followed by packet delay, the number of backlogged bytes reported
by the first netem instance is wrong. It reports the sum of bytes in the queues
of the first and second netem. The first netem reports the correct number of
backlogged packets but not bytes. This is shown in the example below.
Consider a chain of two netem schedulers created using the following commands:
$ tc -s qdisc replace dev veth2 root handle 1:0 netem rate 10000kbit limit 100
$ tc -s qdisc add dev veth2 parent 1:0 handle 2: netem delay 50ms
Start an iperf session to send packets out on the specified interface and
monitor the backlog using tc:
$ tc -s qdisc show dev veth2
Output using unpatched netem:
qdisc netem 1: root refcnt 2 limit 100 rate 10000Kbit
Sent 98422639 bytes 65434 pkt (dropped 123, overlimits 0 requeues 0)
backlog 172694b 73p requeues 0
qdisc netem 2: parent 1: limit 1000 delay 50.0ms
Sent 98422639 bytes 65434 pkt (dropped 0, overlimits 0 requeues 0)
backlog 63588b 42p requeues 0
The interface used to produce this output has an MTU of 1500. The output for
backlogged bytes behind netem 1 is 172694b. This value is not correct. Consider
the total number of sent bytes and packets. By dividing the number of sent
bytes by the number of sent packets, we get an average packet size of ~=1504.
If we divide the number of backlogged bytes by packets, we get ~=2365. This is
due to the first netem incorrectly counting the 63588b which are in netem 2's
queue as being in its own queue. To verify this is the case, we subtract them
from the reported value and divide by the number of packets as follows:
172694 - 63588 = 109106 bytes actualled backlogged in netem 1
109106 / 73 packets ~= 1494 bytes (which matches our MTU)
The root cause is that the byte accounting is not done at the
same time with packet accounting. The solution is to update the backlog value
every time the packet queue is updated.
Signed-off-by: Joseph D Beshay <joseph.beshay@utdallas.edu>
Acked-by: Hagen Paul Pfeifer <hagen@jauu.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Yaogong replaces TCP out of order receive queue by an RB tree.
As netem already does a private skb->{next/prev/tstamp} union
with a 'struct rb_node', lets do this in a cleaner way.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Yaogong Wang <wygivan@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This adds helpers to manipulate qstats logic and replaces locations
that touch the counters directly. This simplifies future patches
to push qstats onto per cpu counters.
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
It is available since v3.15-rc5.
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Replace two magic numbers which intialize clgstate::state.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Replace some magic numbers which describe states of GE model
loss generator with enumerate.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
In netem_change(), we have already get "struct netem_sched_data *q".
Replace params of get_correlation() and other similar functions with
"struct netem_sched_data *q".
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
get_dist_table() and get_loss_clg() may be failed. These
two functions should be called after setting the members
of qdisc_priv(sch), or it will break the old settings while
either of them is failed.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Jakub Zawadzki noticed that some divisions by reciprocal_divide()
were not correct [1][2], which he could also show with BPF code
after divisions are transformed into reciprocal_value() for runtime
invariance which can be passed to reciprocal_divide() later on;
reverse in BPF dump ended up with a different, off-by-one K in
some situations.
This has been fixed by Eric Dumazet in commit aee636c480
("bpf: do not use reciprocal divide"). This follow-up patch
improves reciprocal_value() and reciprocal_divide() to work in
all cases by using Granlund and Montgomery method, so that also
future use is safe and without any non-obvious side-effects.
Known problems with the old implementation were that division by 1
always returned 0 and some off-by-ones when the dividend and divisor
where very large. This seemed to not be problematic with its
current users, as far as we can tell. Eric Dumazet checked for
the slab usage, we cannot surely say so in the case of flex_array.
Still, in order to fix that, we propose an extension from the
original implementation from commit 6a2d7a955d resp. [3][4],
by using the algorithm proposed in "Division by Invariant Integers
Using Multiplication" [5], Torbjörn Granlund and Peter L.
Montgomery, that is, pseudocode for q = n/d where q, n, d is in
u32 universe:
1) Initialization:
int l = ceil(log_2 d)
uword m' = floor((1<<32)*((1<<l)-d)/d)+1
int sh_1 = min(l,1)
int sh_2 = max(l-1,0)
2) For q = n/d, all uword:
uword t = (n*m')>>32
q = (t+((n-t)>>sh_1))>>sh_2
The assembler implementation from Agner Fog [6] also helped a lot
while implementing. We have tested the implementation on x86_64,
ppc64, i686, s390x; on x86_64/haswell we're still half the latency
compared to normal divide.
Joint work with Daniel Borkmann.
[1] http://www.wireshark.org/~darkjames/reciprocal-buggy.c
[2] http://www.wireshark.org/~darkjames/set-and-dump-filter-k-bug.c
[3] https://gmplib.org/~tege/division-paper.pdf
[4] http://homepage.cs.uiowa.edu/~jones/bcd/divide.html
[5] http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1.2556
[6] http://www.agner.org/optimize/asmlib.zip
Reported-by: Jakub Zawadzki <darkjames-ws@darkjames.pl>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Austin S Hemmelgarn <ahferroin7@gmail.com>
Cc: linux-kernel@vger.kernel.org
Cc: Jesse Gross <jesse@nicira.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Andy Gospodarek <andy@greyhouse.net>
Cc: Veaceslav Falico <vfalico@redhat.com>
Cc: Jay Vosburgh <fubar@us.ibm.com>
Cc: Jakub Zawadzki <darkjames-ws@darkjames.pl>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Replace some magic numbers which describe states of 4-state model
loss generator with enumerate.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch removes the net_random and net_srandom macros and replaces
them with direct calls to the prandom ones. As new commits only seem to
use prandom_u32 there is no use to keep them around.
This change makes it easier to grep for users of prandom_u32.
Signed-off-by: Aruna-Hewapathirane <aruna.hewapathirane@gmail.com>
Suggested-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Add a new attribute to support 64bit rates so that
tc can use them to break the 32bit limit.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
With TSO/GSO/GRO packets, skb->len doesn't represent
a precise amount of bytes on wire.
This patch replace skb->len with qdisc_pkt_len(skb)
which is more precise.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Spaces required around that '>' (ctx:VxV) and
before the open parenthesis '('.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Patch from developers of the alternative loss models, downloaded from:
http://netgroup.uniroma2.it/twiki/bin/view.cgi/Main/NetemCLG
"in case 2, of the switch we change the direction of the inequality to
net_random()>clg->a3, because clg->a3 is h in the GE model and when h
is 0 all packets will be lost."
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Patch from developers of the alternative loss models, downloaded from:
http://netgroup.uniroma2.it/twiki/bin/view.cgi/Main/NetemCLG
"In the case 1 of the switch statement in the if conditions we
need to add clg->a4 to clg->a1, according to the model."
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
There is a missing break statement in the Gilbert Elliot loss model
generator which makes state machine behave incorrectly.
Reported-by: Martin Burri <martin.burri@ch.abb.com
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
The transition from markov state "3 => lost packets within a burst
period" to "1 => successfully transmitted packets within a gap period"
has no *additional* loss event. The loss already happen for transition
from 1 -> 3, this additional loss will make things go wild.
E.g. transition probabilities:
p13: 10%
p31: 100%
Expected:
Ploss = p13 / (p13 + p31)
Ploss = ~9.09%
... but it isn't. Even worse: we get a double loss - each time.
So simple don't return true to indicate loss, rather break and return
false.
Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Stefano Salsano <stefano.salsano@uniroma2.it>
Cc: Fabio Ludovici <fabio.ludovici@yahoo.it>
Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Netem can leak memory because packets get stored in red-black
tree and it is not cleared on reset.
Reported by: Сергеев Сергей <adron@yapic.net>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
When packet is dropped from rb-tree netem the backlog statistic should
also be updated.
Reported-by: Сергеев Сергей <adron@yapic.net>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Commit 547669d483 ("tcp: xps: fix reordering issues") added
unexpected reorders in case netem is used in a MQ setup for high
performance test bed.
ETH=eth0
tc qd del dev $ETH root 2>/dev/null
tc qd add dev $ETH root handle 1: mq
for i in `seq 1 32`
do
tc qd add dev $ETH parent 1:$i netem delay 100ms
done
As all tcp packets are orphaned by netem, TCP stack believes it can
set skb->ooo_okay on all packets.
In order to allow producers to send more packets, we want to
keep sk_wmem_alloc from reaching sk_sndbuf limit.
We can do that by accounting one byte per skb in netem queues,
so that TCP stack is not fooled too much.
Tested:
With above MQ/netem setup, scaling number of concurrent flows gives
linear results and no reorders/retransmits
lpq83:~# for n in 1 10 20 30 40 50 60 70 80 90 100
do echo -n "n:$n " ; ./super_netperf $n -H 10.7.7.84; done
n:1 198.46
n:10 2002.69
n:20 4000.98
n:30 6006.35
n:40 8020.93
n:50 10032.3
n:60 12081.9
n:70 13971.3
n:80 16009.7
n:90 17117.3
n:100 17425.5
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
commit aec0a40a6f ("netem: use rb tree to implement the time queue")
added a regression if a child qdisc is attached to netem, as we perform
a NULL dereference.
Fix this by adding a temporary variable to cache
netem_skb_cb(skb)->time_to_send.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Following typical setup to implement a ~100 ms RTT and big
amount of reorders has very poor performance because netem
implements the time queue using a linked list.
-----------------------------------------------------------
ETH=eth0
IFB=ifb0
modprobe ifb
ip link set dev $IFB up
tc qdisc add dev $ETH ingress 2>/dev/null
tc filter add dev $ETH parent ffff: \
protocol ip u32 match u32 0 0 flowid 1:1 action mirred egress \
redirect dev $IFB
ethtool -K $ETH gro off tso off gso off
tc qdisc add dev $IFB root netem delay 50ms 10ms limit 100000
tc qd add dev $ETH root netem delay 50ms limit 100000
---------------------------------------------------------
Switch netem time queue to a rb tree, so this kind of setup can work at
high speed.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
The delay calculation with the rate extension introduces in v3.3 does
not properly work, if other packets are still queued for transmission.
For the delay calculation to work, both delay types (latency and delay
introduces by rate limitation) have to be handled differently. The
latency delay for a packet can overlap with the delay of other packets.
The delay introduced by the rate however is separate, and can only
start, once all other rate-introduced delays finished.
Latency delay is from same distribution for each packet, rate delay
depends on the packet size.
.: latency delay
-: rate delay
x: additional delay we have to wait since another packet is currently
transmitted
.....---- Packet 1
.....xx------ Packet 2
.....------ Packet 3
^^^^^
latency stacks
^^
rate delay doesn't stack
^^
latency stacks
-----> time
When a packet is enqueued, we first consider the latency delay. If other
packets are already queued, we can reduce the latency delay until the
last packet in the queue is send, however the latency delay cannot be
<0, since this would mean that the rate is overcommitted. The new
reference point is the time at which the last packet will be send. To
find the time, when the packet should be send, the rate introduces delay
has to be added on top of that.
Signed-off-by: Johannes Naab <jn@stusta.de>
Acked-by: Hagen Paul Pfeifer <hagen@jauu.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
netem does an early orphaning of skbs. Doing so breaks TCP Small Queue
or any mechanism relying on socket sk_wmem_alloc feedback.
Ideally, we should perform this orphaning after the rate module and
before the delay module, to mimic what happens on a real link :
skb orphaning is indeed normally done at TX completion, before the
transit on the link.
+-------+ +--------+ +---------------+ +-----------------+
+ Qdisc +---> Device +--> TX completion +--> links / hops +->
+ + + xmit + + skb orphaning + + propagation +
+-------+ +--------+ +---------------+ +-----------------+
< rate limiting > < delay, drops, reorders >
If netem is used without delay feature (drops, reorders, rate
limiting), then we should avoid early skb orphaning, to keep pressure
on sockets as long as packets are still in qdisc queue.
Ideally, netem should be refactored to implement delay module
as the last stage. Current algorithm merges the two phases
(rate limiting + delay) so its not correct.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Hagen Paul Pfeifer <hagen@jauu.net>
Cc: Mark Gordon <msg@google.com>
Cc: Andreas Terzis <aterzis@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Fix two netem bugs :
1) When a frame was dropped by tfifo_enqueue(), drop counter
was incremented twice.
2) When reordering is triggered, we enqueue a packet without
checking queue limit. This can OOM pretty fast when this
is repeated enough, since skbs are orphaned, no socket limit
can help in this situation.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Mark Gordon <msg@google.com>
Cc: Andreas Terzis <aterzis@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Hagen Paul Pfeifer <hagen@jauu.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Conflicts:
drivers/net/ethernet/intel/e1000e/param.c
drivers/net/wireless/iwlwifi/iwl-agn-rx.c
drivers/net/wireless/iwlwifi/iwl-trans-pcie-rx.c
drivers/net/wireless/iwlwifi/iwl-trans.h
Resolved the iwlwifi conflict with mainline using 3-way diff posted
by John Linville and Stephen Rothwell. In 'net' we added a bug
fix to make iwlwifi report a more accurate skb->truesize but this
conflicted with RX path changes that happened meanwhile in net-next.
In e1000e a conflict arose in the validation code for settings of
adapter->itr. 'net-next' had more sophisticated logic so that
logic was used.
Signed-off-by: David S. Miller <davem@davemloft.net>
skb_checksum_help(skb) can return an error, we must free skb in this
case. qdisc_drop(skb, sch) can also be feeded with a NULL skb (if
skb_unshare() failed), so lets use this generic helper.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Add ECN (Explicit Congestion Notification) marking capability to netem
tc qdisc add dev eth0 root netem drop 0.5 ecn
Instead of dropping packets, try to ECN mark them.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Hagen Paul Pfeifer <hagen@jauu.net>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Hagen Paul Pfeifer <hagen@jauu.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
These macros contain a hidden goto, and are thus extremely error
prone and make code hard to audit.
Signed-off-by: David S. Miller <davem@davemloft.net>
commit 50612537e9 (netem: fix classful handling) added two errors in
netem_dequeue()
1) After checking skb at the head of tfifo queue for time constraints,
it dequeues tail skb, thus adding unwanted reordering.
2) qdisc stats are updated twice per packet
(one when packet dequeued from tfifo, once when delivered)
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Just like skb->cb[], so that qdisc_skb_cb can be encapsulated inside
of other data structures.
This is intended to be used by IPoIB so that it can remember
addressing information stored at hard_header_ops->create() time that
it can fetch when the packet gets to the transmit routine.
Signed-off-by: David S. Miller <davem@davemloft.net>
With netem reordering, a gap of N is supposed to reorder every Nth packet with
given reorder probability. However, the code currently skips N packets and
reorders every (N+1)th packet.
Signed-off-by: Vijay Subramanian <subramanian.vijay@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Not now, but it looks you are correct. q->qdisc is NULL until another
additional qdisc is attached (beside tfifo). See 50612537e9.
The following patch should work.
From: Hagen Paul Pfeifer <hagen@jauu.net>
netem: catch NULL pointer by updating the real qdisc statistic
Reported-by: Vijay Subramanian <subramanian.vijay@gmail.com>
Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Commit 10f6dfcfde (Revert "sch_netem: Remove classful functionality")
reintroduced classful functionality to netem, but broke basic netem
behavior :
netem uses an t(ime)fifo queue, and store timestamps in skb->cb[]
If qdisc is changed, time constraints are not respected and other qdisc
can destroy skb->cb[] and block netem at dequeue time.
Fix this by always using internal tfifo, and optionally attach a child
qdisc to netem (or a tree of qdiscs)
Example of use :
DEV=eth3
tc qdisc del dev $DEV root
tc qdisc add dev $DEV root handle 30: est 1sec 8sec netem delay 20ms 10ms
tc qdisc add dev $DEV handle 40:0 parent 30:0 tbf \
burst 20480 limit 20480 mtu 1514 rate 32000bps
qdisc netem 30: root refcnt 18 limit 1000 delay 20.0ms 10.0ms
Sent 190792 bytes 413 pkt (dropped 0, overlimits 0 requeues 0)
rate 18416bit 3pps backlog 0b 0p requeues 0
qdisc tbf 40: parent 30: rate 256000bit burst 20Kb/8 mpu 0b lat 0us
Sent 190792 bytes 413 pkt (dropped 6, overlimits 10 requeues 0)
backlog 0b 5p requeues 0
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
commit 6373a9a286 (netem: use vmalloc for distribution table) added a
regression, since vfree() is called while holding a spinlock and BH
being disabled.
Fix this by doing the pointers swap in critical section, and freeing
after spinlock release.
Also add __GFP_NOWARN to the kmalloc() try, since we fallback to
vmalloc().
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The new netem loss model is configured with nested netlink messages.
This code is being overly strict about sizes, and is easily confused
by padding (or possible future expansion). Also message
for gemodel is incorrect.
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This extension can be used to simulate special link layer
characteristics. Simulate because packet data is not modified, only the
calculation base is changed to delay a packet based on the original
packet size and artificial cell information.
packet_overhead can be used to simulate a link layer header compression
scheme (e.g. set packet_overhead to -20) or with a positive
packet_overhead value an additional MAC header can be simulated. It is
also possible to "replace" the 14 byte Ethernet header with something
else.
cell_size and cell_overhead can be used to simulate link layer schemes,
based on cells, like some TDMA schemes. Another application area are MAC
schemes using a link layer fragmentation with a (small) header each.
Cell size is the maximum amount of data bytes within one cell. Cell
overhead is an additional variable to change the per-cell-overhead
(e.g. 5 byte header per fragment).
Example (5 kbit/s, 20 byte per packet overhead, cell-size 100 byte, per
cell overhead 5 byte):
tc qdisc add dev eth0 root netem rate 5kbit 20 100 5
Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
ERROR: "__udivdi3" [net/sched/sch_netem.ko] undefined!
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Hagen Paul Pfeifer <hagen@jauu.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Currently netem is not in the ability to emulate channel bandwidth. Only static
delay (and optional random jitter) can be configured.
To emulate the channel rate the token bucket filter (sch_tbf) can be used. But
TBF has some major emulation flaws. The buffer (token bucket depth/rate) cannot
be 0. Also the idea behind TBF is that the credit (token in buckets) fills if
no packet is transmitted. So that there is always a "positive" credit for new
packets. In real life this behavior contradicts the law of nature where
nothing can travel faster as speed of light. E.g.: on an emulated 1000 byte/s
link a small IPv4/TCP SYN packet with ~50 byte require ~0.05 seconds - not 0
seconds.
Netem is an excellent place to implement a rate limiting feature: static
delay is already implemented, tfifo already has time information and the
user can skip TBF configuration completely.
This patch implement rate feature which can be configured via tc. e.g:
tc qdisc add dev eth0 root netem rate 10kbit
To emulate a link of 5000byte/s and add an additional static delay of 10ms:
tc qdisc add dev eth0 root netem delay 10ms rate 5KBps
Note: similar to TBF the rate extension is bounded to the kernel timing
system. Depending on the architecture timer granularity, higher rates (e.g.
10mbit/s and higher) tend to transmission bursts. Also note: further queues
living in network adaptors; see ethtool(8).
Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@drr.davemloft.net>
Remove linux/mm.h inclusion from netdevice.h -- it's unused (I've checked manually).
To prevent mm.h inclusion via other channels also extract "enum dma_data_direction"
definition into separate header. This tiny piece is what gluing netdevice.h with mm.h
via "netdevice.h => dmaengine.h => dma-mapping.h => scatterlist.h => mm.h".
Removal of mm.h from scatterlist.h was tried and was found not feasible
on most archs, so the link was cutoff earlier.
Hope people are OK with tiny include file.
Note, that mm_types.h is still dragged in, but it is a separate story.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Get rid of debug message that are not useful, and enable
the log messages in case of error.
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This is a patch originated with Stefano Salsano and Fabio Ludovici.
It provides several alternative loss models for use with netem.
This patch adds two state machine based loss models.
See: http://netgroup.uniroma2.it/twiki/bin/view.cgi/Main/NetemCLG
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Many users have wanted the old functionality that was lost
to be able to use pfifo as inner qdisc for netem. The reason that
netem could not be classful with the older API was because of the
limitations of the old dequeue/requeue interface; now that qdisc API has
a peek function, there is no longer a problem with using any
inner qdisc's.
This reverts commit 0220146411.
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Rather than magic constant in code, expose the maximum size of
packet distribution table in API. In iproute2, q_netem defines
MAX_DIST as 16K already.
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The netem probability table can be large (up to 64K bytes)
which may be too large to allocate in one contiguous chunk.
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Use nla_put_nested to update netlink attribute value.
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
