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