Now RED uses a Q0.32 number to store max_p (max probability), allow
RED/GRED/CHOKE to use/report full resolution at config/dump time.

Old tc binaries are non aware of new attributes, and still set/get Plog.

New tc binary set/get both Plog and max_p for backward compatibility,
they display "probability value" if they get max_p from new kernels.

# tc -d  qdisc show dev ...
...
qdisc red 10: parent 1:1 limit 360Kb min 30Kb max 90Kb ecn ewma 5
probability 0.09 Scell_log 15

Make sure we avoid potential divides by 0 in reciprocal_value(), if
(max_th - min_th) is big.
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Adaptative RED AQM for linux, based on paper from Sally FLoyd,
Ramakrishna Gummadi, and Scott Shenker, August 2001 :

http://icir.org/floyd/papers/adaptiveRed.pdf

Goal of Adaptative RED is to make max_p a dynamic value between 1% and
50% to reach the target average queue : (max_th - min_th) / 2

Every 500 ms:
 if (avg > target and max_p <= 0.5)
  increase max_p : max_p += alpha;
 else if (avg < target and max_p >= 0.01)
  decrease max_p : max_p *= beta;

target :[min_th + 0.4*(min_th - max_th),
          min_th + 0.6*(min_th - max_th)].
alpha : min(0.01, max_p / 4)
beta : 0.9
max_P is a Q0.32 fixed point number (unsigned, with 32 bits mantissa)

Changes against our RED implementation are :

max_p is no longer a negative power of two (1/(2^Plog)), but a Q0.32
fixed point number, to allow full range described in Adatative paper.

To deliver a random number, we now use a reciprocal divide (thats really
a multiply), but this operation is done once per marked/droped packet
when in RED_BETWEEN_TRESH window, so added cost (compared to previous
AND operation) is near zero.

dump operation gives current max_p value in a new TCA_RED_MAX_P
attribute.

Example on a 10Mbit link :

tc qdisc add dev $DEV parent 1:1 handle 10: est 1sec 8sec red \
   limit 400000 min 30000 max 90000 avpkt 1000 \
   burst 55 ecn adaptative bandwidth 10Mbit

# tc -s -d qdisc show dev eth3
...
qdisc red 10: parent 1:1 limit 400000b min 30000b max 90000b ecn
adaptative ewma 5 max_p=0.113335 Scell_log 15
 Sent 50414282 bytes 34504 pkt (dropped 35, overlimits 1392 requeues 0)
 rate 9749Kbit 831pps backlog 72056b 16p requeues 0
  marked 1357 early 35 pdrop 0 other 0
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Le mercredi 30 novembre 2011 à 14:36 -0800, Stephen Hemminger a écrit :

> (Almost) nobody uses RED because they can't figure it out.
> According to Wikipedia, VJ says that:
>  "there are not one, but two bugs in classic RED."

RED is useful for high throughput routers, I doubt many linux machines
act as such devices.

I was considering adding Adaptative RED (Sally Floyd, Ramakrishna
Gummadi, Scott Shender), August 2001

In this version, maxp is dynamic (from 1% to 50%), and user only have to
setup min_th (target average queue size)
(max_th and wq (burst in linux RED) are automatically setup)

By the way it seems we have a small bug in red_change()

if (skb_queue_empty(&sch->q))
	red_end_of_idle_period(&q->parms);

First, if queue is empty, we should call
red_start_of_idle_period(&q->parms);

Second, since we dont use anymore sch->q, but q->qdisc, the test is
meaningless.

Oh well...

[PATCH] sch_red: fix red_change()

Now RED is classful, we must check q->qdisc->q.qlen, and if queue is empty,
we start an idle period, not end it.
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

In commit 44b82883 (net_sched: pfifo_head_drop problem), we fixed
a problem with pfifo_head drops that incorrectly decreased
sch->bstats.bytes and sch->bstats.packets

Several qdiscs (CHOKe, SFQ, pfifo_head, ...) are able to drop a
previously enqueued packet, and bstats cannot be changed, so
bstats/rates are not accurate (over estimated)

This patch changes the qdisc_bstats updates to be done at dequeue() time
instead of enqueue() time. bstats counters no longer account for dropped
frames, and rates are more correct, since enqueue() bursts dont have
effect on dequeue() rate.
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Acked-by: NStephen Hemminger <shemminger@vyatta.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Cleanup net/sched code to current CodingStyle and practices.

Reduce inline abuse
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

HTB takes into account skb is segmented in stats updates.
Generalize this to all schedulers.

They should use qdisc_bstats_update() helper instead of manipulating
bstats.bytes and bstats.packets

Add bstats_update() helper too for classes that use
gnet_stats_basic_packed fields.

Note : Right now, TCQ_F_CAN_BYPASS shortcurt can be taken only if no
stab is setup on qdisc.
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Provide child qdisc backlog (byte count) information so that "tc -s
qdisc" can report it to user.

packet count is already correctly provided.

qdisc red 11: parent 1:11 limit 60Kb min 15Kb max 45Kb ecn
 Sent 3116427684 bytes 1415782 pkt (dropped 8, overlimits 7866 requeues 0)
 rate 242385Kbit 13630pps backlog 13560b 8p requeues 0
  marked 7865 early 1 pdrop 7 other 0
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch removes from net/ (but not any netfilter files)
all the unnecessary return; statements that precede the
last closing brace of void functions.

It does not remove the returns that are immediately
preceded by a label as gcc doesn't like that.

Done via:
$ grep -rP --include=*.[ch] -l "return;\n}" net/ | \
  xargs perl -i -e 'local $/ ; while (<>) { s/\n[ \t\n]+return;\n}/\n}/g; print; }'
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The class argument to the ->graft(), ->leaf(), ->dump(), ->dump_stats() all
originate from either ->get() or ->walk() and are always valid.

Remove unnecessary checks.
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Some schedulers don't support creating, changing or deleting classes.
Make the respective callbacks optionally and consistently return
-EOPNOTSUPP for unsupported operations, instead of currently either
-EOPNOTSUPP, -ENOSYS or no error.

In case of sch_prio and sch_multiq, the removed operations additionally
checked for an invalid class. This is not necessary since the class
argument can only orginate from ->get() or in case of ->change is 0
for creation of new classes, in which case ->change() incorrectly
returned -ENOENT.

As a side-effect, this patch fixes a possible (root-only) NULL pointer
function call in sch_ingress, which didn't implement a so far mandatory
->delete() operation.
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Some qdiscs don't support attaching filters. Handle this centrally in
cls_api and return a proper errno code (EOPNOTSUPP) instead of EINVAL.
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The use of xchg() hasn't been necessary since 2.2.something when proper
locking was added to packet schedulers.
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

After implementing qdisc->ops->peek() and changing sch_netem into
classless qdisc there are no more qdisc->ops->requeue() users. This
patch removes this method with its wrappers (qdisc_requeue()), and
also unused qdisc->requeue structure. There are a few minor fixes of
warnings (htb_enqueue()) and comments btw.

The idea to kill ->requeue() and a similar patch were first developed
by David S. Miller.
Signed-off-by: NJarek Poplawski <jarkao2@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add qdisc->ops->peek() implementation for work-conserving qdiscs.
With feedback from Patrick McHardy.
Signed-off-by: NJarek Poplawski <jarkao2@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Patrick McHardy <kaber@trash.net> noticed:
"The other problem that affects all qdiscs supporting actions is
TC_ACT_QUEUED/TC_ACT_STOLEN getting mapped to NET_XMIT_SUCCESS
even though the packet is not queued, corrupting upper qdiscs'
qlen counters."

and later explained:
"The reason why it translates it at all seems to be to not increase
the drops counter. Within a single qdisc this could be avoided by
other means easily, upper qdiscs would still increase the counter
when we return anything besides NET_XMIT_SUCCESS though.

This means we need a new NET_XMIT return value to indicate this to
the upper qdiscs. So I'd suggest to introduce NET_XMIT_STOLEN,
return that to upper qdiscs and translate it to NET_XMIT_SUCCESS
in dev_queue_xmit, similar to NET_XMIT_BYPASS."

David Miller <davem@davemloft.net> noticed:
"Maybe these NET_XMIT_* values being passed around should be a set of
bits. They could be composed of base meanings, combined with specific
attributes.

So you could say "NET_XMIT_DROP | __NET_XMIT_NO_DROP_COUNT"

The attributes get masked out by the top-level ->enqueue() caller,
such that the base meanings are the only thing that make their
way up into the stack. If it's only about communication within the
qdisc tree, let's simply code it that way."

This patch is trying to realize these ideas.
Signed-off-by: NJarek Poplawski <jarkao2@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NJussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NJussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NPatrick McHardy <kaber@trash.net>
Acked-by: NStephen Hemminger <shemminger@vyatta.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Make nlmsg_trim(), nlmsg_cancel(), genlmsg_cancel(), and
nla_nest_cancel() void functions.

Return -EMSGSIZE instead of -1 if the provided message buffer is not
big enough.
Signed-off-by: NThomas Graf <tgraf@suug.ch>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

nla_parse() returns more detailed errno codes, propagate them back on
error.
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Convert packet schedulers to use the netlink API. Unfortunately a gradual
conversion is not possible without breaking compilation in the middle or
adding lots of casts, so this patch converts them all in one step. The
patch has been mostly generated automatically with some minor edits to
at least allow seperate conversion of classifiers and actions.
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Qdisc_class_ops are const, and Qdisc_ops are mostly read.

Using "const" and "__read_mostly" qualifiers helps to reduce false
sharing.
Signed-off-by: NEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NYOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Convert the "simple" qdiscs to use qdisc_tree_decrease_qlen() where
necessary:

- all graft operations
- destruction of old child qdiscs in prio, red and tbf change operation
- purging of queue in sfq change operation
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Set parent classids in default qdiscs to allow walking up the tree
from outside the qdiscs. This is needed by the next patch.
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NJörn Engel <joern@wohnheim.fh-wedel.de>
Signed-off-by: NAdrian Bunk <bunk@stusta.de>

Convert sch_red to a classful qdisc. All qdiscs that maintain accurate
backlog counters are eligible as child qdiscs. When a queue limit larger
than zero is given, a bfifo qdisc is used for backwards compatibility.
Current versions of tc enforce a limit larger than zero, other users
can avoid creating the default qdisc by using zero.
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Acked-by: NJamal Hadi Salim <hadi@cyberus.ca>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Introduces a new flag TC_RED_HARDDROP which specifies that if ECN
marking is enabled packets should still be dropped once the
average queue length exceeds the maximum threshold.

This _may_ help to avoid global synchronisation during small
bursts of peers advertising but not caring about ECN. Use this
option very carefully, it does more harm than good if
(qth_max - qth_min) does not cover at least two average burst
cycles.

The difference to the current behaviour, in which we'd run into
the hard queue limit, is that due to the low pass filter of RED
short bursts are less likely to cause a global synchronisation.
Signed-off-by: NThomas Graf <tgraf@suug.ch>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

Removes the skb trimming code which is not needed since we never
touch the skb upon failure. Removes unnecessary includes,
initializers, and simplifies the code a bit. Removes Jamal's
obsolete email addresses upon his own request.
Signed-off-by: NThomas Graf <tgraf@suug.ch>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

We should not interrupt and restart an idle period while idling already.
Signed-off-by: NThomas Graf <tgraf@suug.ch>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

Signed-off-by: NThomas Graf <tgraf@suug.ch>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

Simplifies code a lot by separating the red algorithm and the
queueing logic. We now differentiate between probability marks
and forced marks but sum them together again to not break
backwards compatibility.
Signed-off-by: NThomas Graf <tgraf@suug.ch>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

This is part of the grand scheme to eliminate the qlen
member of skb_queue_head, and subsequently remove the
'list' member of sk_buff.

Most users of skb_queue_len() want to know if the queue is
empty or not, and that's trivially done with skb_queue_empty()
which doesn't use the skb_queue_head->qlen member and instead
uses the queue list emptyness as the test.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!