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>

1 files changed, 270 insertions, 4 deletions

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index f176890eeef0..5bbcccc353d0 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -47,6 +47,20 @@
          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 {
@@ -73,6 +87,26 @@ 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 */
@@ -115,6 +149,122 @@ static u32 get_crandom(struct crndstate *state)
         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.
@@ -167,8 +317,8 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
         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) {
@@ -385,10 +535,66 @@ static void get_corrupt(struct Qdisc *sch, const struct nlattr *attr)
         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,
@@ -396,11 +602,15 @@ 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;
 }
@@ -456,7 +666,11 @@ static int netem_change(struct Qdisc *sch, struct nlattr *opt)
         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;
 }
 
 /*
@@ -551,6 +765,7 @@ static int netem_init(struct Qdisc *sch, struct nlattr *opt)
 
         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) {
@@ -575,6 +790,54 @@ static void netem_destroy(struct Qdisc *sch)
         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);
@@ -605,6 +868,9 @@ static int netem_dump(struct Qdisc *sch, struct sk_buff *skb)
         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: