diff --git a/src/gprs_codel.c b/src/gprs_codel.c
new file mode 100644
index 0000000..02440b4
--- /dev/null
+++ b/src/gprs_codel.c
@@ -0,0 +1,179 @@
+/* gprs_codel.cpp
+ *
+ * Copyright (C) 2015 by Sysmocom s.f.m.c. GmbH
+ * Author: Jacob Erlbeck <jerlbeck@sysmocom.de>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+ */
+
+#include "gprs_codel.h"
+#include "gprs_debug.h"
+
+#include <osmocom/core/utils.h>
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <math.h>
+
+static void control_law(struct gprs_codel *state, struct timeval *delta)
+{
+	/* 256 / sqrt(x), limited to 255 */
+	static uint8_t inv_sqrt_tab[] = {255,
+		255, 181, 147, 128, 114, 104, 96, 90, 85, 80, 77, 73, 71, 68,
+		66, 64, 62, 60, 58, 57, 55, 54, 53, 52, 51, 50, 49, 48, 47, 46,
+		45, 45, 44, 43, 43, 42, 42, 41, 40, 40, 39, 39, 39, 38, 38, 37,
+		37, 36, 36, 36, 35, 35, 35, 34, 34, 34, 33, 33, 33, 33, 32, 32,
+		32, 32, 31, 31, 31, 31, 30, 30, 30, 30, 29, 29, 29, 29, 29, 28,
+		28, 28, 28, 28, 28, 27, 27, 27, 27, 27, 27, 26, 26, 26, 26, 26,
+		26, 26, 25, 25, 25, 25, 25, 25, 25, 25, 24, 24, 24, 24, 24, 24,
+		24, 24, 24, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 22, 22, 22,
+		22, 22, 22, 22, 22, 22, 22, 22, 22, 21, 21, 21, 21, 21, 21, 21,
+		21, 21, 21, 21, 21, 21, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20,
+		20, 20, 20, 20, 20, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19,
+		19, 19, 19, 19, 19, 19, 19, 18, 18, 18, 18, 18, 18, 18, 18, 18,
+		18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 17, 17, 17, 17,
+		17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17,
+		17, 17, 17, 17
+	};
+	uint_fast32_t delta_usecs;
+	uint_fast32_t inv_sqrt;
+	div_t q;
+
+	if (state->count >= ARRAY_SIZE(inv_sqrt_tab))
+		inv_sqrt = 16;
+	else
+		inv_sqrt = inv_sqrt_tab[state->count];
+
+	/* delta = state->interval / sqrt(count) */
+	delta_usecs = state->interval.tv_sec * 1000000 + state->interval.tv_usec;
+	delta_usecs = delta_usecs * inv_sqrt / 256;
+
+	q = div(delta_usecs, 1000000);
+	delta->tv_sec = q.quot;
+	delta->tv_usec = q.rem;
+}
+
+void gprs_codel_init(struct gprs_codel *state)
+{
+	static const struct gprs_codel init_state = {0};
+
+	*state = init_state;
+	gprs_codel_set_interval(state, -1);
+	gprs_codel_set_maxpacket(state, -1);
+}
+
+void gprs_codel_set_interval(struct gprs_codel *state, int interval_ms)
+{
+	div_t q;
+
+	if (interval_ms <= 0)
+		interval_ms = GPRS_CODEL_DEFAULT_INTERVAL_MS;
+
+	q = div(interval_ms, 1000);
+	state->interval.tv_sec = q.quot;
+	state->interval.tv_usec = q.rem * 1000;
+
+	/* target ~ 5% of interval */
+	q = div(interval_ms * 13 / 256, 1000);
+	state->target.tv_sec = q.quot;
+	state->target.tv_usec = q.rem * 1000;
+}
+
+void gprs_codel_set_maxpacket(struct gprs_codel *state, int maxpacket)
+{
+
+	if (maxpacket < 0)
+		maxpacket = GPRS_CODEL_DEFAULT_MAXPACKET;
+
+	state->maxpacket = maxpacket;
+}
+
+/*
+ * This is an broken up variant of the algorithm being described in
+ * http://queue.acm.org/appendices/codel.html
+ */
+int gprs_codel_control(struct gprs_codel *state, const struct timeval *recv,
+	const struct timeval *now, int bytes)
+{
+	struct timeval sojourn_time;
+	struct timeval delta;
+
+	if (recv == NULL)
+		goto stop_dropping;
+
+	timersub(now, recv, &sojourn_time);
+
+	if (timercmp(&sojourn_time, &state->target, <))
+		goto stop_dropping;
+
+	if (bytes >= 0 && (unsigned)bytes <= state->maxpacket)
+		goto stop_dropping;
+
+	if (!timerisset(&state->first_above_time)) {
+		timeradd(now, &state->interval, &state->first_above_time);
+		goto not_ok_to_drop;
+	}
+
+	if (timercmp(now, &state->first_above_time, <))
+		goto not_ok_to_drop;
+
+	/* Ok to drop */
+
+	if (!state->dropping) {
+		int recently = 0;
+		int in_drop_cycle = 0;
+		if (timerisset(&state->drop_next)) {
+			timersub(now, &state->drop_next, &delta);
+			in_drop_cycle = timercmp(&delta, &state->interval, <);
+			recently = in_drop_cycle;
+		}
+		if (!recently) {
+			timersub(now, &state->first_above_time, &delta);
+			recently = !timercmp(&delta, &state->interval, <);
+		};
+		if (!recently)
+			return 0;
+
+		state->dropping = 1;
+
+		if (in_drop_cycle && state->count > 2)
+			state->count -= 2;
+		else
+			state->count = 1;
+
+		state->drop_next = *now;
+	} else {
+		if (timercmp(now, &state->drop_next, <))
+			return 0;
+
+		state->count += 1;
+	}
+
+	control_law(state, &delta);
+	timeradd(&state->drop_next, &delta, &state->drop_next);
+
+#if 1
+	LOGP(DRLCMAC, LOGL_INFO,
+		"CoDel decided to drop packet, window = %d.%03dms, count = %d\n",
+		(int)delta.tv_sec, (int)(delta.tv_usec / 1000), state->count);
+#endif
+	return 1;
+
+stop_dropping:
+	timerclear(&state->first_above_time);
+not_ok_to_drop:
+	state->dropping = 0;
+	return 0;
+}