Date: Thu, 14 May 2020 09:55:41 +0000 (UTC) From: Richard Scheffenegger <rscheff@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org Subject: svn commit: r361029 - stable/12/sys/netinet/cc Message-ID: <202005140955.04E9tf9Z089481@repo.freebsd.org>
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Author: rscheff Date: Thu May 14 09:55:41 2020 New Revision: 361029 URL: https://svnweb.freebsd.org/changeset/base/361029 Log: MFC r360491: Introduce a lower bound of 2 MSS to TCP Cubic. Running TCP Cubic together with ECN could end up reducing cwnd down to 1 byte, if the receiver continously sets the ECE flag, resulting in very poor transmission speeds. In line with RFC6582 App. B, a lower bound of 2 MSS is introduced, as well as a typecast to prevent any potential integer overflows during intermediate calculation steps of the adjusted cwnd. Reported by: Cheng Cui Reviewed by: tuexen (mentor) Approved by: tuexen (mentor) Sponsored by: NetApp, Inc. Differential Revision: https://reviews.freebsd.org/D23353 Modified: stable/12/sys/netinet/cc/cc_cubic.c Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/netinet/cc/cc_cubic.c ============================================================================== --- stable/12/sys/netinet/cc/cc_cubic.c Thu May 14 09:18:50 2020 (r361028) +++ stable/12/sys/netinet/cc/cc_cubic.c Thu May 14 09:55:41 2020 (r361029) @@ -332,8 +332,9 @@ cubic_post_recovery(struct cc_var *ccv) CCV(ccv, t_maxseg); else /* Update cwnd based on beta and adjusted max_cwnd. */ - CCV(ccv, snd_cwnd) = max(1, ((CUBIC_BETA * - cubic_data->max_cwnd) >> CUBIC_SHIFT)); + CCV(ccv, snd_cwnd) = max(((uint64_t)cubic_data->max_cwnd * + CUBIC_BETA) >> CUBIC_SHIFT, + 2 * CCV(ccv, t_maxseg)); } cubic_data->t_last_cong = ticks; @@ -399,6 +400,7 @@ static void cubic_ssthresh_update(struct cc_var *ccv) { struct cubic *cubic_data; + uint32_t ssthresh; cubic_data = ccv->cc_data; @@ -407,10 +409,11 @@ cubic_ssthresh_update(struct cc_var *ccv) * subsequent congestion events, set it to cwnd * beta. */ if (cubic_data->num_cong_events == 0) - CCV(ccv, snd_ssthresh) = CCV(ccv, snd_cwnd) >> 1; + ssthresh = CCV(ccv, snd_cwnd) >> 1; else - CCV(ccv, snd_ssthresh) = ((u_long)CCV(ccv, snd_cwnd) * + ssthresh = ((uint64_t)CCV(ccv, snd_cwnd) * CUBIC_BETA) >> CUBIC_SHIFT; + CCV(ccv, snd_ssthresh) = max(ssthresh, 2 * CCV(ccv, t_maxseg)); }
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