svn commit: r354774 - head/sys/netinet/cc
Michael Tuexen
tuexen at FreeBSD.org
Sat Nov 16 12:00:24 UTC 2019
Author: tuexen
Date: Sat Nov 16 12:00:22 2019
New Revision: 354774
URL: https://svnweb.freebsd.org/changeset/base/354774
Log:
Add boundary and overflow checks to the formulas used in the TCP CUBIC
congestion control module.
Submitted by: Richard Scheffenegger
Reviewed by: rgrimes@
Differential Revision: https://reviews.freebsd.org/D19118
Modified:
head/sys/netinet/cc/cc_cubic.c
head/sys/netinet/cc/cc_cubic.h
Modified: head/sys/netinet/cc/cc_cubic.c
==============================================================================
--- head/sys/netinet/cc/cc_cubic.c Sat Nov 16 11:57:12 2019 (r354773)
+++ head/sys/netinet/cc/cc_cubic.c Sat Nov 16 12:00:22 2019 (r354774)
@@ -52,6 +52,7 @@ __FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/kernel.h>
+#include <sys/limits.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/socket.h>
@@ -140,7 +141,14 @@ cubic_ack_received(struct cc_var *ccv, uint16_t type)
cubic_data->min_rtt_ticks == TCPTV_SRTTBASE)
newreno_cc_algo.ack_received(ccv, type);
else {
- ticks_since_cong = ticks - cubic_data->t_last_cong;
+ if ((ticks_since_cong =
+ ticks - cubic_data->t_last_cong) < 0) {
+ /*
+ * dragging t_last_cong along
+ */
+ ticks_since_cong = INT_MAX;
+ cubic_data->t_last_cong = ticks - INT_MAX;
+ }
/*
* The mean RTT is used to best reflect the equations in
@@ -159,12 +167,14 @@ cubic_ack_received(struct cc_var *ccv, uint16_t type)
ccv->flags &= ~CCF_ABC_SENTAWND;
- if (w_cubic_next < w_tf)
+ if (w_cubic_next < w_tf) {
/*
* TCP-friendly region, follow tf
* cwnd growth.
*/
- CCV(ccv, snd_cwnd) = w_tf;
+ if (CCV(ccv, snd_cwnd) < w_tf)
+ CCV(ccv, snd_cwnd) = ulmin(w_tf, INT_MAX);
+ }
else if (CCV(ccv, snd_cwnd) < w_cubic_next) {
/*
@@ -172,12 +182,14 @@ cubic_ack_received(struct cc_var *ccv, uint16_t type)
* cwnd growth.
*/
if (V_tcp_do_rfc3465)
- CCV(ccv, snd_cwnd) = w_cubic_next;
+ CCV(ccv, snd_cwnd) = ulmin(w_cubic_next,
+ INT_MAX);
else
- CCV(ccv, snd_cwnd) += ((w_cubic_next -
+ CCV(ccv, snd_cwnd) += ulmax(1,
+ ((ulmin(w_cubic_next, INT_MAX) -
CCV(ccv, snd_cwnd)) *
CCV(ccv, t_maxseg)) /
- CCV(ccv, snd_cwnd);
+ CCV(ccv, snd_cwnd));
}
/*
Modified: head/sys/netinet/cc/cc_cubic.h
==============================================================================
--- head/sys/netinet/cc/cc_cubic.h Sat Nov 16 11:57:12 2019 (r354773)
+++ head/sys/netinet/cc/cc_cubic.h Sat Nov 16 12:00:22 2019 (r354774)
@@ -41,6 +41,8 @@
#ifndef _NETINET_CC_CUBIC_H_
#define _NETINET_CC_CUBIC_H_
+#include <sys/limits.h>
+
/* Number of bits of precision for fixed point math calcs. */
#define CUBIC_SHIFT 8
@@ -70,6 +72,12 @@
/* Don't trust s_rtt until this many rtt samples have been taken. */
#define CUBIC_MIN_RTT_SAMPLES 8
+/*
+ * (2^21)^3 is long max. Dividing (2^63) by Cubic_C_factor
+ * and taking cube-root yields 448845 as the effective useful limit
+ */
+#define CUBED_ROOT_MAX_ULONG 448845
+
/* Userland only bits. */
#ifndef _KERNEL
@@ -172,8 +180,13 @@ cubic_cwnd(int ticks_since_cong, unsigned long wmax, u
/* K is in fixed point form with CUBIC_SHIFT worth of precision. */
/* t - K, with CUBIC_SHIFT worth of precision. */
- cwnd = ((int64_t)(ticks_since_cong << CUBIC_SHIFT) - (K * hz)) / hz;
+ cwnd = (((int64_t)ticks_since_cong << CUBIC_SHIFT) - (K * hz)) / hz;
+ if (cwnd > CUBED_ROOT_MAX_ULONG)
+ return INT_MAX;
+ if (cwnd < -CUBED_ROOT_MAX_ULONG)
+ return 0;
+
/* (t - K)^3, with CUBIC_SHIFT^3 worth of precision. */
cwnd *= (cwnd * cwnd);
@@ -183,9 +196,13 @@ cubic_cwnd(int ticks_since_cong, unsigned long wmax, u
* CUBIC_SHIFT included in the value. 3 from the cubing of cwnd above,
* and an extra from multiplying through by CUBIC_C_FACTOR.
*/
- cwnd = ((cwnd * CUBIC_C_FACTOR * smss) >> CUBIC_SHIFT_4) + wmax;
- return ((unsigned long)cwnd);
+ cwnd = ((cwnd * CUBIC_C_FACTOR) >> CUBIC_SHIFT_4) * smss + wmax;
+
+ /*
+ * for negative cwnd, limiting to zero as lower bound
+ */
+ return (lmax(0,cwnd));
}
/*
@@ -223,8 +240,10 @@ tf_cwnd(int ticks_since_cong, int rtt_ticks, unsigned
{
/* Equation 4 of I-D. */
- return (((wmax * CUBIC_BETA) + (((THREE_X_PT3 * ticks_since_cong *
- smss) << CUBIC_SHIFT) / TWO_SUB_PT3 / rtt_ticks)) >> CUBIC_SHIFT);
+ return (((wmax * CUBIC_BETA) +
+ (((THREE_X_PT3 * (unsigned long)ticks_since_cong *
+ (unsigned long)smss) << CUBIC_SHIFT) / (TWO_SUB_PT3 * rtt_ticks)))
+ >> CUBIC_SHIFT);
}
#endif /* _NETINET_CC_CUBIC_H_ */
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