From 2cd60521deffe6ef0dc3e3bc5ef7f5037e93f1dc Mon Sep 17 00:00:00 2001
From: Steffen Vogel <post@steffenvogel.de>
Date: Sun, 19 Jul 2015 16:16:31 +0200
Subject: [PATCH] imported some code to handle netem delay distributions

---
 project/dist.c | 141 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 141 insertions(+)
 create mode 100644 project/dist.c

diff --git a/project/dist.c b/project/dist.c
new file mode 100644
index 0000000..0bf6e34
--- /dev/null
+++ b/project/dist.c
@@ -0,0 +1,141 @@
+/** Generate distribution tables for netem qdisc.
+ *
+ * Partially based on:
+ *  - http://git.kernel.org/cgit/linux/kernel/git/shemminger/iproute2.git/tree/netem/maketable.c
+ *  - https://github.com/thom311/libnl/blob/master/lib/route/qdisc/netem.c
+ *
+ * @author Steffen Vogel <post@steffenvogel.de>
+ * @copyright 2014-2015, Steffen Vogel 
+ * @license GPLv3
+ *********************************************************************************/
+
+/**
+ * Set the delay distribution. Latency/jitter must be set before applying.
+ * @arg qdisc Netem qdisc.
+ * @return 0 on success, error code on failure.
+ */
+int rtnl_netem_set_delay_distribution_data(struct rtnl_qdisc *qdisc, double *data, size_t len) {
+	struct rtnl_netem *netem;
+
+	if (!(netem = rtnl_tc_data(TC_CAST(qdisc))))
+		BUG();
+	
+	if (len > MAXDIST)
+		return -NLE_INVAL;
+
+	netem->qnm_dist.dist_data = (int16_t *) calloc(len, sizeof(int16_t));
+	
+	size_t i;		
+	for (i = 0; i < len; i++)
+		netem->qnm_dist.dist_data[n++] = data[i];
+	
+	netem->qnm_dist.dist_size = len;
+	netem->qnm_mask |= SCH_NETEM_ATTR_DIST;
+
+	return 0;	
+}
+
+/* Create a (normalized) distribution table from a set of observed
+ * values.  The table is fixed to run from (as it happens) -4 to +4,
+ * with granularity .00002.
+ */
+
+#define TABLESIZE	16384/4
+#define TABLEFACTOR	8192
+#ifndef MINSHORT
+#define MINSHORT	-32768
+#define MAXSHORT	32767
+#endif
+
+/* Since entries in the inverse are scaled by TABLEFACTOR, and can't be bigger
+ * than MAXSHORT, we don't bother looking at a larger domain than this:
+ */
+#define DISTTABLEDOMAIN ((MAXSHORT/TABLEFACTOR)+1)
+#define DISTTABLEGRANULARITY 50000
+#define DISTTABLESIZE (DISTTABLEDOMAIN*DISTTABLEGRANULARITY*2)
+
+static int * makedist(double *x, int limit, double mu, double sigma)
+{
+	int *table;
+	int i, index, first=DISTTABLESIZE, last=0;
+	double input;
+
+	table = calloc(DISTTABLESIZE, sizeof(int));
+	if (!table) {
+		perror("table alloc");
+		exit(3);
+	}
+
+	for (i=0; i < limit; ++i) {
+		/* Normalize value */
+		input = (x[i]-mu)/sigma;
+
+		index = (int)rint((input+DISTTABLEDOMAIN)*DISTTABLEGRANULARITY);
+		if (index < 0) index = 0;
+		if (index >= DISTTABLESIZE) index = DISTTABLESIZE-1;
+		++table[index];
+		if (index > last)
+			last = index +1;
+		if (index < first)
+			first = index;
+	}
+	return table;
+}
+
+/* replace an array by its cumulative distribution */
+static void cumulativedist(int *table, int limit, int *total)
+{
+	int accum=0;
+
+	while (--limit >= 0) {
+		accum += *table;
+		*table++ = accum;
+	}
+	*total = accum;
+}
+
+static short * inverttable(int *table, int inversesize, int tablesize, int cumulative)
+{
+	int i, inverseindex, inversevalue;
+	short *inverse;
+	double findex, fvalue;
+
+	inverse = (short *)malloc(inversesize*sizeof(short));
+	for (i=0; i < inversesize; ++i) {
+		inverse[i] = MINSHORT;
+	}
+	for (i=0; i < tablesize; ++i) {
+		findex = ((double)i/(double)DISTTABLEGRANULARITY) - DISTTABLEDOMAIN;
+		fvalue = (double)table[i]/(double)cumulative;
+		inverseindex = (int)rint(fvalue*inversesize);
+		inversevalue = (int)rint(findex*TABLEFACTOR);
+		if (inversevalue <= MINSHORT) inversevalue = MINSHORT+1;
+		if (inversevalue > MAXSHORT) inversevalue = MAXSHORT;
+		inverse[inverseindex] = inversevalue;
+	}
+	return inverse;
+
+}
+
+/* Run simple linear interpolation over the table to fill in missing entries */
+static void interpolatetable(short *table, int limit)
+{
+	int i, j, last, lasti = -1;
+
+	last = MINSHORT;
+	for (i=0; i < limit; ++i) {
+		if (table[i] == MINSHORT) {
+			for (j=i; j < limit; ++j)
+				if (table[j] != MINSHORT)
+					break;
+			if (j < limit) {
+				table[i] = last + (i-lasti)*(table[j]-last)/(j-lasti);
+			} else {
+				table[i] = last + (i-lasti)*(MAXSHORT-last)/(limit-lasti);
+			}
+		} else {
+			last = table[i];
+			lasti = i;
+		}
+	}
+}
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