Author: rscheff Date: Wed Jun 24 16:17:58 2020 New Revision: 362586 URL: https://svnweb.freebsd.org/changeset/base/362586
Log: MFC r361347: With RFC3168 ECN, CWR SHOULD only be sent with new data Overly conservative data receivers may ignore the CWR flag on other packets, and keep ECE latched. This can result in continous reduction of the congestion window, and very poor performance when ECN is enabled. PR: 243590 Reviewed by: rgrimes (mentor), rrs Approved by: rgrimes (mentor, blanket) MFC after: 3 weeks Sponsored by: NetApp, Inc. Differential Revision: https://reviews.freebsd.org/D23364 Modified: stable/12/sys/netinet/tcp_input.c stable/12/sys/netinet/tcp_output.c stable/12/sys/netinet/tcp_stacks/rack.c Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/netinet/tcp_input.c ============================================================================== --- stable/12/sys/netinet/tcp_input.c Wed Jun 24 15:46:33 2020 (r362585) +++ stable/12/sys/netinet/tcp_input.c Wed Jun 24 16:17:58 2020 (r362586) @@ -417,9 +417,15 @@ cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, ui } break; case CC_ECN: - if (!IN_CONGRECOVERY(tp->t_flags)) { + if (!IN_CONGRECOVERY(tp->t_flags) || + /* + * Allow ECN reaction on ACK to CWR, if + * that data segment was also CE marked. + */ + SEQ_GEQ(th->th_ack, tp->snd_recover)) { + EXIT_CONGRECOVERY(tp->t_flags); TCPSTAT_INC(tcps_ecn_rcwnd); - tp->snd_recover = tp->snd_max; + tp->snd_recover = tp->snd_max + 1; if (tp->t_flags & TF_ECN_PERMIT) tp->t_flags |= TF_ECN_SND_CWR; } Modified: stable/12/sys/netinet/tcp_output.c ============================================================================== --- stable/12/sys/netinet/tcp_output.c Wed Jun 24 15:46:33 2020 (r362585) +++ stable/12/sys/netinet/tcp_output.c Wed Jun 24 16:17:58 2020 (r362586) @@ -1132,7 +1132,8 @@ send: * Ignore pure ack packets, retransmissions and window probes. */ if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && - !((tp->t_flags & TF_FORCEDATA) && len == 1)) { + !((tp->t_flags & TF_FORCEDATA) && len == 1 && + SEQ_LT(tp->snd_una, tp->snd_max))) { #ifdef INET6 if (isipv6) ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); @@ -1140,15 +1141,15 @@ send: #endif ip->ip_tos |= IPTOS_ECN_ECT0; TCPSTAT_INC(tcps_ecn_ect0); + /* + * Reply with proper ECN notifications. + * Only set CWR on new data segments. + */ + if (tp->t_flags & TF_ECN_SND_CWR) { + flags |= TH_CWR; + tp->t_flags &= ~TF_ECN_SND_CWR; + } } - - /* - * Reply with proper ECN notifications. - */ - if (tp->t_flags & TF_ECN_SND_CWR) { - flags |= TH_CWR; - tp->t_flags &= ~TF_ECN_SND_CWR; - } if (tp->t_flags & TF_ECN_SND_ECE) flags |= TH_ECE; } Modified: stable/12/sys/netinet/tcp_stacks/rack.c ============================================================================== --- stable/12/sys/netinet/tcp_stacks/rack.c Wed Jun 24 15:46:33 2020 (r362585) +++ stable/12/sys/netinet/tcp_stacks/rack.c Wed Jun 24 16:17:58 2020 (r362586) @@ -1415,9 +1415,15 @@ rack_cong_signal(struct tcpcb *tp, struct tcphdr *th, } break; case CC_ECN: - if (!IN_CONGRECOVERY(tp->t_flags)) { + if (!IN_CONGRECOVERY(tp->t_flags) || + /* + * Allow ECN reaction on ACK to CWR, if + * that data segment was also CE marked. + */ + SEQ_GEQ(th->th_ack, tp->snd_recover)) { + EXIT_CONGRECOVERY(tp->t_flags); TCPSTAT_INC(tcps_ecn_rcwnd); - tp->snd_recover = tp->snd_max; + tp->snd_recover = tp->snd_max + 1; if (tp->t_flags & TF_ECN_PERMIT) tp->t_flags |= TF_ECN_SND_CWR; } @@ -8283,13 +8289,14 @@ send: #endif ip->ip_tos |= IPTOS_ECN_ECT0; TCPSTAT_INC(tcps_ecn_ect0); - } - /* - * Reply with proper ECN notifications. - */ - if (tp->t_flags & TF_ECN_SND_CWR) { - flags |= TH_CWR; - tp->t_flags &= ~TF_ECN_SND_CWR; + /* + * Reply with proper ECN notifications. + * Only set CWR on new data segments. + */ + if (tp->t_flags & TF_ECN_SND_CWR) { + flags |= TH_CWR; + tp->t_flags &= ~TF_ECN_SND_CWR; + } } if (tp->t_flags & TF_ECN_SND_ECE) flags |= TH_ECE; _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
