netem: revised correlated loss generator
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>
This commit is contained in:
stephen hemminger
David S. Miller
parent
10f6dfcfde
commit
661b79725f
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@ -464,6 +464,7 @@ enum {
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TCA_NETEM_DELAY_DIST,
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TCA_NETEM_REORDER,
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TCA_NETEM_CORRUPT,
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TCA_NETEM_LOSS,
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__TCA_NETEM_MAX,
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};
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@ -494,6 +495,31 @@ struct tc_netem_corrupt {
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__u32 correlation;
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};
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enum {
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NETEM_LOSS_UNSPEC,
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NETEM_LOSS_GI, /* General Intuitive - 4 state model */
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NETEM_LOSS_GE, /* Gilbert Elliot models */
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__NETEM_LOSS_MAX
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};
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#define NETEM_LOSS_MAX (__NETEM_LOSS_MAX - 1)
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/* State transition probablities for 4 state model */
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struct tc_netem_gimodel {
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__u32 p13;
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__u32 p31;
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__u32 p32;
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__u32 p14;
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__u32 p23;
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};
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/* Gilbert-Elliot models */
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struct tc_netem_gemodel {
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__u32 p;
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__u32 r;
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__u32 h;
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__u32 k1;
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};
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#define NETEM_DIST_SCALE 8192
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#define NETEM_DIST_MAX 16384
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@ -47,6 +47,20 @@
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layering other disciplines. It does not need to do bandwidth
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control either since that can be handled by using token
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bucket or other rate control.
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Correlated Loss Generator models
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Added generation of correlated loss according to the
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"Gilbert-Elliot" model, a 4-state markov model.
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References:
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[1] NetemCLG Home http://netgroup.uniroma2.it/NetemCLG
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[2] S. Salsano, F. Ludovici, A. Ordine, "Definition of a general
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and intuitive loss model for packet networks and its implementation
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in the Netem module in the Linux kernel", available in [1]
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Authors: Stefano Salsano <stefano.salsano at uniroma2.it
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Fabio Ludovici <fabio.ludovici at yahoo.it>
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*/
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struct netem_sched_data {
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@ -73,6 +87,26 @@ struct netem_sched_data {
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u32 size;
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s16 table[0];
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} *delay_dist;
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enum {
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CLG_RANDOM,
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CLG_4_STATES,
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CLG_GILB_ELL,
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} loss_model;
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/* Correlated Loss Generation models */
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struct clgstate {
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/* state of the Markov chain */
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u8 state;
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/* 4-states and Gilbert-Elliot models */
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u32 a1; /* p13 for 4-states or p for GE */
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u32 a2; /* p31 for 4-states or r for GE */
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u32 a3; /* p32 for 4-states or h for GE */
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u32 a4; /* p14 for 4-states or 1-k for GE */
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u32 a5; /* p23 used only in 4-states */
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} clg;
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};
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/* Time stamp put into socket buffer control block */
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@ -115,6 +149,122 @@ static u32 get_crandom(struct crndstate *state)
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return answer;
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}
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/* loss_4state - 4-state model loss generator
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* Generates losses according to the 4-state Markov chain adopted in
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* the GI (General and Intuitive) loss model.
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*/
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static bool loss_4state(struct netem_sched_data *q)
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{
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struct clgstate *clg = &q->clg;
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u32 rnd = net_random();
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/*
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* Makes a comparision between rnd and the transition
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* probabilities outgoing from the current state, then decides the
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* next state and if the next packet has to be transmitted or lost.
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* The four states correspond to:
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* 1 => successfully transmitted packets within a gap period
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* 4 => isolated losses within a gap period
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* 3 => lost packets within a burst period
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* 2 => successfully transmitted packets within a burst period
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*/
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switch (clg->state) {
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case 1:
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if (rnd < clg->a4) {
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clg->state = 4;
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return true;
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} else if (clg->a4 < rnd && rnd < clg->a1) {
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clg->state = 3;
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return true;
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} else if (clg->a1 < rnd)
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clg->state = 1;
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break;
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case 2:
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if (rnd < clg->a5) {
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clg->state = 3;
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return true;
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} else
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clg->state = 2;
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break;
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case 3:
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if (rnd < clg->a3)
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clg->state = 2;
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else if (clg->a3 < rnd && rnd < clg->a2 + clg->a3) {
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clg->state = 1;
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return true;
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} else if (clg->a2 + clg->a3 < rnd) {
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clg->state = 3;
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return true;
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}
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break;
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case 4:
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clg->state = 1;
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break;
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}
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return false;
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}
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/* loss_gilb_ell - Gilbert-Elliot model loss generator
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* Generates losses according to the Gilbert-Elliot loss model or
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* its special cases (Gilbert or Simple Gilbert)
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*
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* Makes a comparision between random number and the transition
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* probabilities outgoing from the current state, then decides the
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* next state. A second random number is extracted and the comparision
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* with the loss probability of the current state decides if the next
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* packet will be transmitted or lost.
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*/
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static bool loss_gilb_ell(struct netem_sched_data *q)
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{
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struct clgstate *clg = &q->clg;
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switch (clg->state) {
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case 1:
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if (net_random() < clg->a1)
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clg->state = 2;
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if (net_random() < clg->a4)
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return true;
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case 2:
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if (net_random() < clg->a2)
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clg->state = 1;
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if (clg->a3 > net_random())
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return true;
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}
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return false;
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}
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static bool loss_event(struct netem_sched_data *q)
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{
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switch (q->loss_model) {
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case CLG_RANDOM:
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/* Random packet drop 0 => none, ~0 => all */
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return q->loss && q->loss >= get_crandom(&q->loss_cor);
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case CLG_4_STATES:
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/* 4state loss model algorithm (used also for GI model)
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* Extracts a value from the markov 4 state loss generator,
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* if it is 1 drops a packet and if needed writes the event in
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* the kernel logs
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*/
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return loss_4state(q);
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case CLG_GILB_ELL:
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/* Gilbert-Elliot loss model algorithm
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* Extracts a value from the Gilbert-Elliot loss generator,
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* if it is 1 drops a packet and if needed writes the event in
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* the kernel logs
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*/
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return loss_gilb_ell(q);
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}
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return false; /* not reached */
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}
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/* tabledist - return a pseudo-randomly distributed value with mean mu and
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* std deviation sigma. Uses table lookup to approximate the desired
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* distribution, and a uniformly-distributed pseudo-random source.
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@ -167,8 +317,8 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
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if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor))
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++count;
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/* Random packet drop 0 => none, ~0 => all */
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if (q->loss && q->loss >= get_crandom(&q->loss_cor))
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/* Drop packet? */
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if (loss_event(q))
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--count;
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if (count == 0) {
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@ -385,10 +535,66 @@ static void get_corrupt(struct Qdisc *sch, const struct nlattr *attr)
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init_crandom(&q->corrupt_cor, r->correlation);
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}
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static int get_loss_clg(struct Qdisc *sch, const struct nlattr *attr)
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{
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struct netem_sched_data *q = qdisc_priv(sch);
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const struct nlattr *la;
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int rem;
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nla_for_each_nested(la, attr, rem) {
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u16 type = nla_type(la);
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switch(type) {
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case NETEM_LOSS_GI: {
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const struct tc_netem_gimodel *gi = nla_data(la);
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if (nla_len(la) != sizeof(struct tc_netem_gimodel)) {
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pr_info("netem: incorrect gi model size\n");
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return -EINVAL;
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}
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q->loss_model = CLG_4_STATES;
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q->clg.state = 1;
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q->clg.a1 = gi->p13;
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q->clg.a2 = gi->p31;
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q->clg.a3 = gi->p32;
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q->clg.a4 = gi->p14;
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q->clg.a5 = gi->p23;
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break;
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}
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case NETEM_LOSS_GE: {
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const struct tc_netem_gemodel *ge = nla_data(la);
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if (nla_len(la) != sizeof(struct tc_netem_gemodel)) {
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pr_info("netem: incorrect gi model size\n");
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return -EINVAL;
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}
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q->loss_model = CLG_GILB_ELL;
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q->clg.state = 1;
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q->clg.a1 = ge->p;
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q->clg.a2 = ge->r;
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q->clg.a3 = ge->h;
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q->clg.a4 = ge->k1;
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break;
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}
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default:
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pr_info("netem: unknown loss type %u\n", type);
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return -EINVAL;
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}
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}
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return 0;
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}
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static const struct nla_policy netem_policy[TCA_NETEM_MAX + 1] = {
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[TCA_NETEM_CORR] = { .len = sizeof(struct tc_netem_corr) },
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[TCA_NETEM_REORDER] = { .len = sizeof(struct tc_netem_reorder) },
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[TCA_NETEM_CORRUPT] = { .len = sizeof(struct tc_netem_corrupt) },
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[TCA_NETEM_LOSS] = { .type = NLA_NESTED },
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};
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static int parse_attr(struct nlattr *tb[], int maxtype, struct nlattr *nla,
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@ -396,11 +602,15 @@ static int parse_attr(struct nlattr *tb[], int maxtype, struct nlattr *nla,
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{
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int nested_len = nla_len(nla) - NLA_ALIGN(len);
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if (nested_len < 0)
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if (nested_len < 0) {
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pr_info("netem: invalid attributes len %d\n", nested_len);
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return -EINVAL;
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}
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if (nested_len >= nla_attr_size(0))
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return nla_parse(tb, maxtype, nla_data(nla) + NLA_ALIGN(len),
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nested_len, policy);
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memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
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return 0;
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}
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@ -456,7 +666,11 @@ static int netem_change(struct Qdisc *sch, struct nlattr *opt)
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if (tb[TCA_NETEM_CORRUPT])
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get_corrupt(sch, tb[TCA_NETEM_CORRUPT]);
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return 0;
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q->loss_model = CLG_RANDOM;
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if (tb[TCA_NETEM_LOSS])
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ret = get_loss_clg(sch, tb[TCA_NETEM_LOSS]);
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return ret;
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}
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/*
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@ -551,6 +765,7 @@ static int netem_init(struct Qdisc *sch, struct nlattr *opt)
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qdisc_watchdog_init(&q->watchdog, sch);
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q->loss_model = CLG_RANDOM;
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q->qdisc = qdisc_create_dflt(sch->dev_queue, &tfifo_qdisc_ops,
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TC_H_MAKE(sch->handle, 1));
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if (!q->qdisc) {
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@ -575,6 +790,54 @@ static void netem_destroy(struct Qdisc *sch)
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dist_free(q->delay_dist);
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}
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static int dump_loss_model(const struct netem_sched_data *q,
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struct sk_buff *skb)
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{
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struct nlattr *nest;
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nest = nla_nest_start(skb, TCA_NETEM_LOSS);
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if (nest == NULL)
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goto nla_put_failure;
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switch (q->loss_model) {
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case CLG_RANDOM:
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/* legacy loss model */
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nla_nest_cancel(skb, nest);
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return 0; /* no data */
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case CLG_4_STATES: {
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struct tc_netem_gimodel gi = {
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.p13 = q->clg.a1,
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.p31 = q->clg.a2,
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.p32 = q->clg.a3,
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.p14 = q->clg.a4,
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.p23 = q->clg.a5,
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};
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NLA_PUT(skb, NETEM_LOSS_GI, sizeof(gi), &gi);
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break;
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}
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case CLG_GILB_ELL: {
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struct tc_netem_gemodel ge = {
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.p = q->clg.a1,
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.r = q->clg.a2,
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.h = q->clg.a3,
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.k1 = q->clg.a4,
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};
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NLA_PUT(skb, NETEM_LOSS_GE, sizeof(ge), &ge);
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break;
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}
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}
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nla_nest_end(skb, nest);
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return 0;
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nla_put_failure:
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nla_nest_cancel(skb, nest);
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return -1;
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}
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static int netem_dump(struct Qdisc *sch, struct sk_buff *skb)
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{
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const struct netem_sched_data *q = qdisc_priv(sch);
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@ -605,6 +868,9 @@ static int netem_dump(struct Qdisc *sch, struct sk_buff *skb)
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corrupt.correlation = q->corrupt_cor.rho;
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NLA_PUT(skb, TCA_NETEM_CORRUPT, sizeof(corrupt), &corrupt);
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if (dump_loss_model(q, skb) != 0)
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goto nla_put_failure;
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return nla_nest_end(skb, nla);
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nla_put_failure:
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