Add RED AQM.

Enforce & require the Red packet queue to have packet_limit.

Author: squidarth

src/frontend/linkshell.cc

@@ -7,6 +7,7 @@
 #include "drop_head_packet_queue.hh"
 #include "codel_packet_queue.hh"
 #include "pie_packet_queue.hh"
+#include "red_packet_queue.hh"
 #include "link_queue.hh"
 #include "packetshell.cc"
 
@@ -44,6 +45,8 @@ unique_ptr<AbstractPacketQueue> get_packet_queue( const string & type, const str
         return unique_ptr<AbstractPacketQueue>( new CODELPacketQueue( args ) );
     } else if ( type == "pie" ) {
         return unique_ptr<AbstractPacketQueue>( new PIEPacketQueue( args ) );
+    } else if ( type == "red" ) {
+        return unique_ptr<AbstractPacketQueue>( new REDPacketQueue( args ) );
     } else {
         cerr << "Unknown queue type: " << type << endl;
     }
@@ -96,7 +99,7 @@ int main( int argc, char *argv[] )
             { "meter-downlink-delay",       no_argument, nullptr, 'y' },
             { "meter-all",                  no_argument, nullptr, 'z' },
             { "uplink-queue",         required_argument, nullptr, 'q' },
-            { "downlink-queue",       required_argument, nullptr, 'w' },
+            { "downlink-queue",         required_argument, nullptr, 'w' },
             { "uplink-queue-args",    required_argument, nullptr, 'a' },
             { "downlink-queue-args",  required_argument, nullptr, 'b' },
             { 0,                                      0, nullptr, 0 }

src/packet/Makefile.am

@@ -7,5 +7,6 @@ libpacket_a_SOURCES = packetshell.hh packetshell.cc queued_packet.hh \
                       abstract_packet_queue.hh dropping_packet_queue.hh dropping_packet_queue.cc infinite_packet_queue.hh \
                       drop_tail_packet_queue.hh drop_head_packet_queue.hh \
                       codel_packet_queue.cc codel_packet_queue.hh \
+		       red_packet_queue.cc red_packet_queue.hh \
                       pie_packet_queue.cc pie_packet_queue.hh \
                       bindworkaround.hh

src/packet/dropping_packet_queue.cc

@@ -99,11 +99,11 @@ string DroppingPacketQueue::to_string( void ) const
     return ret;
 }
 
-unsigned int DroppingPacketQueue::get_arg( const string & args, const string & name )
+string DroppingPacketQueue::parse_number_arg(const string & args, const string & name, bool isfloat)
 {
     auto offset = args.find( name );
     if ( offset == string::npos ) {
-        return 0; /* default value */
+        return ""; /* default value */
     } else {
         /* extract the value */
 
@@ -118,15 +118,46 @@ unsigned int DroppingPacketQueue::get_arg( const string & args, const string & n
         /* advance by length of "=" */
         offset++;
 
-        /* find the first non-digit character */
-        auto offset2 = args.substr( offset ).find_first_not_of( "0123456789" );
+        /* find the first non-valid character */
+        string validchars;
+        if (isfloat) {
+            validchars = "0123456789.";
+        } else {
+            validchars = "0123456789";
+        }
+        auto offset2 = args.substr( offset ).find_first_not_of( validchars );
 
         auto digit_string = args.substr( offset ).substr( 0, offset2 );
 
         if ( digit_string.empty() ) {
             throw runtime_error( "could not parse queue arguments: " + args );
         }
+        return digit_string;
+    }
+}
+
+unsigned int DroppingPacketQueue::get_arg( const string & args, const string & name)
+{
+    auto offset = args.find( name );
+    if ( offset == string::npos ) {
+        return 0; /* default value */
+    } else {
+        auto digit_string = parse_number_arg(args, name, false);
 
         return myatoi( digit_string );
     }
 }
+
+double DroppingPacketQueue::get_float_arg( const string & args, const string & name)
+{
+    auto offset = args.find( name );
+    if ( offset == string::npos ) {
+        return 0; /* default value */
+    } else {
+        auto digit_string = parse_number_arg(args, name, true);
+        return myatof( digit_string );
+    }
+
+}
+
+

src/packet/dropping_packet_queue.hh

@@ -41,10 +41,13 @@ public:
 
     std::string to_string( void ) const override;
 
-    static unsigned int get_arg( const std::string & args, const std::string & name );
-
+    static std::string parse_number_arg(const std::string & args, const std::string & name, bool isfloat);
     unsigned int size_bytes( void ) const override;
     unsigned int size_packets( void ) const override;
+
+    static unsigned int get_arg( const std::string & args, const std::string & name );
+
+    static double get_float_arg( const std::string & args, const std::string & name );
 };
 
 #endif /* DROPPING_PACKET_QUEUE_HH */ 

src/packet/red_packet_queue.cc

@@ -0,0 +1,65 @@
+#include "red_packet_queue.hh"
+#include <algorithm>
+#include "timestamp.hh"
+
+using namespace std;
+
+REDPacketQueue::REDPacketQueue( const string & args)
+  : DroppingPacketQueue(args),
+    wq_(get_float_arg(args, "wq")),
+    min_thresh_(get_float_arg(args, "minthresh")),
+    max_thresh_(get_float_arg(args, "maxthresh")),
+    time_at_zero_q_(0)
+{
+  if (packet_limit_ == 0) {
+    throw runtime_error( "RED queue must have packet limit." );
+  }
+
+  if ( wq_ == 0.0 || min_thresh_ == 0.0 || max_thresh_ == 0.0 ) {
+    throw runtime_error( "RED queue must have wq, minthresh, and maxthresh arguments." );
+  }
+
+}
+
+QueuedPacket REDPacketQueue::dequeue( void )
+{
+    auto packet = DroppingPacketQueue::dequeue();
+    if (size_packets() == 0) {
+      time_at_zero_q_ = timestamp();
+    }
+
+    return packet;
+}
+
+void REDPacketQueue::enqueue( QueuedPacket && p )
+{
+    int s = 4;
+    auto instantaneous_queue_size = size_packets();
+
+    /* If the queue is empty, decay the weighted average by
+     * the amount of time that the queue has been
+     * empty. */
+    if (size_packets() == 0) {
+        weighted_average_ = powf((1 - wq_), (timestamp() - time_at_zero_q_)/s) * weighted_average_;
+    } else {
+        weighted_average_ = (instantaneous_queue_size * wq_ ) + (1- wq_) * weighted_average_;
+    }
+
+    auto ratio = (weighted_average_)/packet_limit_;
+    std::default_random_engine generator (0);
+    std::uniform_real_distribution<double> distribution (min_thresh_, max_thresh_);
+    double threshold = distribution(generator);
+    if (ratio > max_thresh_) {
+      ratio = 1;
+    }
+    if (ratio < min_thresh_) {
+      ratio = 0;
+    }
+
+    if ( (threshold > ratio) && good_with( size_bytes() + p.contents.size(),
+                    size_packets() + 1 ) ) {
+        accept( std::move( p ) );
+    }
+
+    assert( good() );
+}

src/packet/red_packet_queue.hh

@@ -0,0 +1,46 @@
+/* -*-mode:c++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+
+#ifndef RED_PACKET_QUEUE_HH
+#define RED_PACKET_QUEUE_HH
+
+#include <string>
+#include "util.hh"
+#include <iostream>
+
+#include <fstream>
+#include <memory>
+#include <deque>
+#include <random>
+#include "dropping_packet_queue.hh"
+
+/*
+   Random Early Detection (RED) AQM Implementation.
+   See section 3 of https://tools.ietf.org/html/rfc2309#ref-Jacobson88
+   for a description of the queuing discipline.
+   j
+
+*/
+class REDPacketQueue : public DroppingPacketQueue
+{
+private:
+    //Configuration parameters
+    const static unsigned int PACKET_SIZE = 1504;
+    double wq_, min_thresh_, max_thresh_;
+    uint64_t time_at_zero_q_;
+
+    const std::string & type( void ) const override
+    {
+        static const std::string type_ { "red" };
+        return type_;
+    }
+
+    double weighted_average_ = 0;
+    unsigned int max_queue_depth_packets() const;
+
+public:
+    REDPacketQueue( const std::string & args );
+    QueuedPacket dequeue( void ) override;
+    void enqueue( QueuedPacket && p ) override;
+};
+
+#endif