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# Random Detect
#
# This Qos module uses DSMARK and GRED to provide a policy
# similar to Cisco Weighted Random Detect.
#
# See Almesberger, Werner; Hadi Salim, Jamal; Kuznetsov, Alexey
# "Differentiated Services on Linux"
# http://www.almesberger.net/cv/papers/18270721.pdf
#
# **** License ****
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# General Public License for more details.
#
# This code was originally developed by Vyatta, Inc.
# Portions created by Vyatta are Copyright (C) 2008 Vyatta, Inc.
# All Rights Reserved.
# **** End License ****
package Vyatta::Qos::RandomDetect;
use strict;
use warnings;
require Vyatta::Config;
use Vyatta::Qos::Util qw/getRate getAutoRate getTime/;
# Create a new instance based on config information
sub new {
my ( $that, $config, $name ) = @_;
my $level = $config->setLevel();
my $rate = $config->returnValue("bandwidth");
die "$level bandwidth configuration missing" unless $rate;
my @precedence = getPrecedence( $level );
my $self = {};
my $class = ref($that) || $that;
bless $self, $class;
$self->{_rate} = $rate;
$self->{_precedence} = \@precedence;
return $self;
}
sub getPrecedence {
my ( $level ) = @_;
my $config = new Vyatta::Config;
my @precedence;
for ( my $i = 0 ; $i <= 7 ; $i++ ) {
my %pred;
$config->setLevel("$level precedence $i");
# Compute some sane defaults based on predence and max-threshold
$pred{qmax} = $config->returnValue('maximum-threshold');
$pred{qmax} = 18 unless $pred{qmax};
$pred{qmin} = $config->returnValue('minimum-threshold');
if ($pred{qmin}) {
die "min-threshold: $pred{qmin} > max-threshold: $pred{qmax}\n"
if ($pred{qmin} > $pred{qmax});
} else {
$pred{qmin} = ((9 + $i) * $pred{qmax})/ 18;
}
$pred{qlim} = $config->returnValue('queue-limit');
if ($pred{qlim}) {
die "queue-limit: $pred{qlim} < max-threshold: $pred{qmax}\n"
if ($pred{qlim} < $pred{qmax});
} else {
$pred{qlim} = 4 * $pred{qmax};
}
my $mp = $config->returnValue('mark-probablilty');
$pred{prob} = (defined $mp) ? (1 / $mp) : (1 / 10);
my $avgpkt = $config->returnValue('average-packet');
$pred{avpkt} = (defined $avgpkt) ? $avgpkt : 1024;
$precedence[$i] = \%pred;
}
return @precedence;
}
sub commands {
my ( $self, $dev ) = @_;
my $root = 1;
my $precedence = $self->{_precedence};
my $rate = getAutoRate( $self->{_rate}, $dev );
# 1. setup DSMARK to convert DSCP to tc_index
printf "qdisc add dev %s root handle %x:0 dsmark indices 8 set_tc_index\n",
$dev, $root;
# 2. use tcindex filter to convert tc_index to precedence
#
# Precedence Field: the three leftmost bits in the TOS octet of an IPv4
# header.
printf "filter add dev %s parent %x:0 protocol ip prio 1 ",
$dev, $root;
print "tcindex mask 0xe0 shift 5\n";
# 3. Define GRED with unmatched traffic going to index 0
printf "qdisc add dev %s parent %x:0 handle %x:0 gred ",
$dev, $root, $root+1;
print "setup DPs 8 default 0 grio\n";
# set VQ parameters
for ( my $i = 0 ; $i <= 7 ; $i++ ) {
my $pred = $precedence->[$i];
my $avg = $pred->{avpkt};
my $burst = ( 2 * $pred->{qmin} + $pred->{qmax} ) / 3;
printf "qdisc change dev %s handle %x:0 gred", $dev, $root+1, $i;
printf " limit %d min %d max %d avpkt %d",
$pred->{qlim} * $avg, $pred->{qmin} * $avg,
$pred->{qmax} * $avg, $avg;
printf " burst %d bandwidth %d probability %f DP %d prio %d\n",
$burst, $rate, $pred->{prob}, $i, 8-$i;
}
}
# Walk configuration tree and look for changed nodes
# The configuration system should do this but doesn't do it right
sub isChanged {
my ( $self, $name ) = @_;
my $config = new Vyatta::Config;
$config->setLevel("qos-policy random-detect $name");
return 'bandwidth' if ( $config->isChanged('bandwidth') );
my %precedenceNodes = $config->listNodeStatus('precedence');
while ( my ( $pred, $status ) = each %precedenceNodes ) {
return "precedence $pred" if ( $status ne 'static' );
foreach my $attr qw(average-packet min-threshold mark-probability
max-threshold queue-limit) {
return "precedence $pred $attr"
if ( $config->isChanged("precedence $pred $attr") );
}
}
return; # false
}
1;
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