Date: Sat, 19 Jun 2021 17:41:44 GMT From: Richard Scheffenegger <rscheff@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 74d7fc8753a7 - main - tcp: Add PRR cwnd reduction for non-SACK loss Message-ID: <202106191741.15JHfiMY061653@gitrepo.freebsd.org>
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The branch main has been updated by rscheff: URL: https://cgit.FreeBSD.org/src/commit/?id=74d7fc8753a76851db6db556ff0f09de1fbb26d5 commit 74d7fc8753a76851db6db556ff0f09de1fbb26d5 Author: Richard Scheffenegger <rscheff@FreeBSD.org> AuthorDate: 2021-06-19 17:06:48 +0000 Commit: Richard Scheffenegger <rscheff@FreeBSD.org> CommitDate: 2021-06-19 17:25:22 +0000 tcp: Add PRR cwnd reduction for non-SACK loss This completes PRR cwnd reduction in all circumstances for the base TCP stack (SACK loss recovery, ECN window reduction, non-SACK loss recovery), preventing the arriving ACKs to clock out new data at the old, too high rate. This reduces the chance to induce additional losses while recovering from loss (during congested network conditions). For non-SACK loss recovery, each ACK is assumed to have one MSS delivered. In order to prevent ACK-split attacks, only one window worth of ACKs is considered to actually have delivered new data. MFC after: 6 weeks Reviewed By: rrs, #transport Sponsored by: NetApp, Inc. Differential Revision: https://reviews.freebsd.org/D29441 --- sys/netinet/tcp_input.c | 56 ++++++++++++++++++++++++++++++++++++------------- 1 file changed, 41 insertions(+), 15 deletions(-) diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c index 1d685b43697f..a8fe6d9817d0 100644 --- a/sys/netinet/tcp_input.c +++ b/sys/netinet/tcp_input.c @@ -2612,8 +2612,7 @@ tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, cc_ack_received(tp, th, nsegs, CC_DUPACK); if (V_tcp_do_prr && - IN_FASTRECOVERY(tp->t_flags) && - (tp->t_flags & TF_SACK_PERMIT)) { + IN_FASTRECOVERY(tp->t_flags)) { tcp_do_prr_ack(tp, th, &to); } else if ((tp->t_flags & TF_SACK_PERMIT) && (to.to_flags & TOF_SACK) && @@ -2689,8 +2688,16 @@ enter_recovery: * snd_ssthresh is already updated by * cc_cong_signal. */ - tp->sackhint.prr_delivered = - tp->sackhint.sacked_bytes; + if ((tp->t_flags & TF_SACK_PERMIT) && + (to.to_flags & TOF_SACK)) { + tp->sackhint.prr_delivered = + tp->sackhint.sacked_bytes; + } else { + tp->sackhint.prr_delivered = + imin(tp->snd_max - tp->snd_una, + imin(INT_MAX / 65536, + tp->t_dupacks) * maxseg); + } tp->sackhint.recover_fs = max(1, tp->snd_nxt - tp->snd_una); } @@ -3968,11 +3975,23 @@ tcp_do_prr_ack(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) * (del_data) and an estimate of how many bytes are in the * network. */ - del_data = tp->sackhint.delivered_data; - if (V_tcp_do_newsack) - pipe = tcp_compute_pipe(tp); - else - pipe = (tp->snd_nxt - tp->snd_fack) + tp->sackhint.sack_bytes_rexmit; + if (((tp->t_flags & TF_SACK_PERMIT) && + (to->to_flags & TOF_SACK)) || + (IN_CONGRECOVERY(tp->t_flags) && + !IN_FASTRECOVERY(tp->t_flags))) { + del_data = tp->sackhint.delivered_data; + if (V_tcp_do_newsack) + pipe = tcp_compute_pipe(tp); + else + pipe = (tp->snd_nxt - tp->snd_fack) + + tp->sackhint.sack_bytes_rexmit; + } else { + if (tp->sackhint.prr_delivered < (tcprexmtthresh * maxseg + + tp->snd_recover - tp->snd_una)) + del_data = maxseg; + pipe = imax(0, tp->snd_max - tp->snd_una - + imin(INT_MAX / 65536, tp->t_dupacks) * maxseg); + } tp->sackhint.prr_delivered += del_data; /* * Proportional Rate Reduction @@ -3985,9 +4004,9 @@ tcp_do_prr_ack(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) tp->snd_ssthresh, tp->sackhint.recover_fs) - tp->sackhint.prr_out; } else { - if (V_tcp_do_prr_conservative) + if (V_tcp_do_prr_conservative || (del_data == 0)) limit = tp->sackhint.prr_delivered - - tp->sackhint.prr_out; + tp->sackhint.prr_out; else limit = imax(tp->sackhint.prr_delivered - tp->sackhint.prr_out, del_data) + @@ -4001,11 +4020,18 @@ tcp_do_prr_ack(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) * accordingly. */ if (IN_FASTRECOVERY(tp->t_flags)) { - tp->snd_cwnd = imax(maxseg, tp->snd_nxt - tp->snd_recover + - tp->sackhint.sack_bytes_rexmit + (snd_cnt * maxseg)); + if ((tp->t_flags & TF_SACK_PERMIT) && + (to->to_flags & TOF_SACK)) { + tp->snd_cwnd = tp->snd_nxt - tp->snd_recover + + tp->sackhint.sack_bytes_rexmit + + (snd_cnt * maxseg); + } else { + tp->snd_cwnd = (tp->snd_max - tp->snd_una) + + (snd_cnt * maxseg); + } } else if (IN_CONGRECOVERY(tp->t_flags)) - tp->snd_cwnd = imax(maxseg, pipe - del_data + - (snd_cnt * maxseg)); + tp->snd_cwnd = pipe - del_data + (snd_cnt * maxseg); + tp->snd_cwnd = imax(maxseg, tp->snd_cwnd); } /*
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