/* Part of SWI-Prolog Author: Jan Wielemaker E-mail: J.Wielemaker@vu.nl WWW: http://www.swi-prolog.org Copyright (c) 2018, VU University Amsterdam CWI, Amsterdam All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ :- module(poor_udp, [ udp_drop/1, % +Rate udp_late/2, % +Rate, +Decay udp_duplicate/2, % +Rate, +Decay udp_delay/2, % +Rate, +Decay udp_profile/1 % +ListOrName ]). :- use_module(library(random)). :- use_module(library(debug)). :- use_module(library(apply)). :- use_module(library(socket), []). :- use_module(library(udp_broadcast), []). % :- debug(udp(qos)). /** Emulate a unreliable UDP network This library hooks into library(udp_broadcast) to emulate poor reception of UDP messages. It can emulate package loss, late (out-of-order) arrival, duplicated packages and delayed (slow) arrival. The initial network quality is perfect. @tbd Possibly we should also implement package loss for sending a UDP message, so we can easily emulate a poor node in an otherwise well functioning network. */ :- dynamic drop_rate/1, late_rate/2, dupl_rate/2, delay_rate/2, delayed/5. drop_rate(0). late_rate(0, 0). dupl_rate(0, 0). delay_rate(0, 0). %! udp_drop(+Rate) % % Rate is the probability that a package is dropped. `0` means a % perfect network, `1` a completely broken network. udp_drop(Rate) :- retractall(drop_rate(_)), asserta(drop_rate(Rate)). %! udp_late(+Rate, +Decay) % % Rate is the probability that the package will arrive late, i.e., out % of order. Decay is the probability it will arrive after the next. udp_late(Rate, Decay) :- retractall(late_rate(_, _)), asserta(late_rate(Rate, Decay)). %! udp_duplicate(+Rate, +Decay) % % Rate is the probability the package is duplicated. This accepts the % package immediately as is and stores a copy in the queue that is % also used by late/2. udp_duplicate(Rate, Decay) :- retractall(dupl_rate(_, _)), asserta(dupl_rate(Rate, Decay)). %! udp_delay(+Rate, +Decay) % % Rate is the probability to delay the message. This introduces random % sleeps of 10ms. After each sleep there is a probability of Decay to % wake up. Thus, with a Decay of 0.5 we wait 10ms with probability % 0.5, 20ms with probability 0.25, 30ms with probability 0.125, etc. udp_delay(Rate, Decay) :- retractall(delay_rate(_, _)), asserta(delay_rate(Rate, Decay)). %! udp_profile(+Spec) is det. % % Set all network connection quality parameters. Spec is either a list % of calls to drop/1, late/2, duplicate/2 and/or delay/2 or a profile % name. See profile/2 for details. udp_profile(Actions) :- is_list(Actions), !, maplist(apply, Actions). udp_profile(Name) :- profile(Name, Actions), maplist(apply, Actions). apply(drop(Rate)) :- udp_drop(Rate). apply(late(Rate, Decay)) :- udp_late(Rate, Decay). apply(duplicate(Rate, Decay)) :- udp_duplicate(Rate, Decay). apply(delay(Rate, Decay)) :- udp_delay(Rate, Decay). %! profile(+Name, -Settings) % % Define network quality profiles. :- multifile profile/2. profile(perfect, [ drop(0), late(0,0), duplicate(0,0), delay(0,0) ]). profile(poor, [ drop(0.02), late(0.02, 0.5), duplicate(0.02, 0.5), delay(0.02, 0.5) ]). profile(disconnected, [ drop(1) ]). :- abolish(udp_broadcast:udp_receive/4). udp_broadcast:udp_receive(Socket, Data, From, Options) :- udp_receive(Socket, Data, From, Options), ( dupl_rate(Rate, Decay), maybe(Rate) -> assertz(delayed(Socket, Data, From, Decay, duplicate)) ; true ), delay. udp_receive(Socket, Data, From, _Options) :- clause(delayed(Socket, Data1, From1, Rate, Why), true, Ref), maybe(Rate), !, Data = Data1, From = From1, erase(Ref), udp_debug('Re-inserting package (~w) ~p', [Why], Data, From). udp_receive(Socket, Data, From, Options) :- socket:udp_receive(Socket, Data0, From0, Options), ( drop_rate(Drop), maybe(Drop) -> udp_debug('Dropped package ~p', [], Data0, From0), udp_receive(Socket, Data, From, Options) ; late_rate(Rate, Decay), maybe(Rate) -> assertz(delayed(Socket, Data0, From0, Decay, reorder)), udp_debug('Taking package out of order ~p', [], Data0, From0), udp_receive(Socket, Data, From, Options) ; Data = Data0, From = From0 ). udp_debug(Message, Args, Data, _From) :- udp_broadcast:udp_term_string(_Scope, Term, Data), append(Args, [Term], AllArgs), debug(udp(qos), Message, AllArgs). delay :- delay_rate(Rate, Decay), maybe(Rate), !, get_time(Now), repeat, sleep(0.010), maybe(Decay), !, get_time(End), Delay is round((End-Now)*1000), debug(udp(qos), 'Delayed with ~Dms', [Delay]). delay.