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
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Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=354774
@ -52,6 +52,7 @@ __FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/kernel.h>
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#include <sys/limits.h>
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#include <sys/malloc.h>
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#include <sys/module.h>
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#include <sys/socket.h>
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@ -140,7 +141,14 @@ cubic_ack_received(struct cc_var *ccv, uint16_t type)
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cubic_data->min_rtt_ticks == TCPTV_SRTTBASE)
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newreno_cc_algo.ack_received(ccv, type);
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else {
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ticks_since_cong = ticks - cubic_data->t_last_cong;
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if ((ticks_since_cong =
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ticks - cubic_data->t_last_cong) < 0) {
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/*
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* dragging t_last_cong along
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*/
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ticks_since_cong = INT_MAX;
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cubic_data->t_last_cong = ticks - INT_MAX;
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}
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/*
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* The mean RTT is used to best reflect the equations in
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@ -159,12 +167,14 @@ cubic_ack_received(struct cc_var *ccv, uint16_t type)
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ccv->flags &= ~CCF_ABC_SENTAWND;
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if (w_cubic_next < w_tf)
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if (w_cubic_next < w_tf) {
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/*
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* TCP-friendly region, follow tf
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* cwnd growth.
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*/
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CCV(ccv, snd_cwnd) = w_tf;
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if (CCV(ccv, snd_cwnd) < w_tf)
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CCV(ccv, snd_cwnd) = ulmin(w_tf, INT_MAX);
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}
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else if (CCV(ccv, snd_cwnd) < w_cubic_next) {
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/*
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@ -172,12 +182,14 @@ cubic_ack_received(struct cc_var *ccv, uint16_t type)
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* cwnd growth.
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*/
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if (V_tcp_do_rfc3465)
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CCV(ccv, snd_cwnd) = w_cubic_next;
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CCV(ccv, snd_cwnd) = ulmin(w_cubic_next,
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INT_MAX);
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else
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CCV(ccv, snd_cwnd) += ((w_cubic_next -
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CCV(ccv, snd_cwnd) += ulmax(1,
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((ulmin(w_cubic_next, INT_MAX) -
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CCV(ccv, snd_cwnd)) *
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CCV(ccv, t_maxseg)) /
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CCV(ccv, snd_cwnd);
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CCV(ccv, snd_cwnd));
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}
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/*
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@ -41,6 +41,8 @@
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#ifndef _NETINET_CC_CUBIC_H_
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#define _NETINET_CC_CUBIC_H_
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#include <sys/limits.h>
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/* Number of bits of precision for fixed point math calcs. */
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#define CUBIC_SHIFT 8
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@ -70,6 +72,12 @@
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/* Don't trust s_rtt until this many rtt samples have been taken. */
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#define CUBIC_MIN_RTT_SAMPLES 8
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/*
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* (2^21)^3 is long max. Dividing (2^63) by Cubic_C_factor
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* and taking cube-root yields 448845 as the effective useful limit
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*/
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#define CUBED_ROOT_MAX_ULONG 448845
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/* Userland only bits. */
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#ifndef _KERNEL
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@ -172,7 +180,12 @@ cubic_cwnd(int ticks_since_cong, unsigned long wmax, uint32_t smss, int64_t K)
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/* K is in fixed point form with CUBIC_SHIFT worth of precision. */
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/* t - K, with CUBIC_SHIFT worth of precision. */
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cwnd = ((int64_t)(ticks_since_cong << CUBIC_SHIFT) - (K * hz)) / hz;
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cwnd = (((int64_t)ticks_since_cong << CUBIC_SHIFT) - (K * hz)) / hz;
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if (cwnd > CUBED_ROOT_MAX_ULONG)
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return INT_MAX;
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if (cwnd < -CUBED_ROOT_MAX_ULONG)
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return 0;
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/* (t - K)^3, with CUBIC_SHIFT^3 worth of precision. */
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cwnd *= (cwnd * cwnd);
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@ -183,9 +196,13 @@ cubic_cwnd(int ticks_since_cong, unsigned long wmax, uint32_t smss, int64_t K)
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* CUBIC_SHIFT included in the value. 3 from the cubing of cwnd above,
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* and an extra from multiplying through by CUBIC_C_FACTOR.
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*/
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cwnd = ((cwnd * CUBIC_C_FACTOR * smss) >> CUBIC_SHIFT_4) + wmax;
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return ((unsigned long)cwnd);
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cwnd = ((cwnd * CUBIC_C_FACTOR) >> CUBIC_SHIFT_4) * smss + wmax;
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/*
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* for negative cwnd, limiting to zero as lower bound
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*/
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return (lmax(0,cwnd));
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}
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/*
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@ -223,8 +240,10 @@ tf_cwnd(int ticks_since_cong, int rtt_ticks, unsigned long wmax,
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{
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/* Equation 4 of I-D. */
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return (((wmax * CUBIC_BETA) + (((THREE_X_PT3 * ticks_since_cong *
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smss) << CUBIC_SHIFT) / TWO_SUB_PT3 / rtt_ticks)) >> CUBIC_SHIFT);
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return (((wmax * CUBIC_BETA) +
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(((THREE_X_PT3 * (unsigned long)ticks_since_cong *
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(unsigned long)smss) << CUBIC_SHIFT) / (TWO_SUB_PT3 * rtt_ticks)))
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>> CUBIC_SHIFT);
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}
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#endif /* _NETINET_CC_CUBIC_H_ */
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