Author: rscheff Date: Fri Oct 9 09:37:43 2020 New Revision: 366565 URL: https://svnweb.freebsd.org/changeset/base/366565
Log: MFC r366150: TCP: send full initial window when timestamps are in use The fastpath in tcp_output tries to send out full segments, and avoid sending partial segments by comparing against the static t_maxseg variable. That value does not consider tcp options like timestamps, while the initial window calculation is using the correct dynamic tcp_maxseg() function. Due to this interaction, the last, full size segment is considered too short and not sent out immediately. Reported by: tuexen MFC after: 2 weeks Sponsored by: NetApp, Inc. Differential Revision: https://reviews.freebsd.org/D26478 Modified: stable/12/sys/netinet/tcp.h stable/12/sys/netinet/tcp_output.c stable/12/sys/netinet/tcp_subr.c Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/netinet/tcp.h ============================================================================== --- stable/12/sys/netinet/tcp.h Fri Oct 9 09:33:45 2020 (r366564) +++ stable/12/sys/netinet/tcp.h Fri Oct 9 09:37:43 2020 (r366565) @@ -80,6 +80,8 @@ struct tcphdr { u_short th_urp; /* urgent pointer */ }; +#define PADTCPOLEN(len) ((((len) / 4) + !!((len) % 4)) * 4) + #define TCPOPT_EOL 0 #define TCPOLEN_EOL 1 #define TCPOPT_PAD 0 /* padding after EOL */ Modified: stable/12/sys/netinet/tcp_output.c ============================================================================== --- stable/12/sys/netinet/tcp_output.c Fri Oct 9 09:33:45 2020 (r366564) +++ stable/12/sys/netinet/tcp_output.c Fri Oct 9 09:37:43 2020 (r366565) @@ -577,6 +577,20 @@ after_sack_rexmit: if (len >= tp->t_maxseg) goto send; /* + * As the TCP header options are now + * considered when setting up the initial + * window, we would not send the last segment + * if we skip considering the option length here. + * Note: this may not work when tcp headers change + * very dynamically in the future. + */ + if ((((tp->t_flags & TF_SIGNATURE) ? + PADTCPOLEN(TCPOLEN_SIGNATURE) : 0) + + ((tp->t_flags & TF_RCVD_TSTMP) ? + PADTCPOLEN(TCPOLEN_TIMESTAMP) : 0) + + len) >= tp->t_maxseg) + goto send; + /* * NOTE! on localhost connections an 'ack' from the remote * end may occur synchronously with the output and cause * us to flush a buffer queued with moretocome. XXX Modified: stable/12/sys/netinet/tcp_subr.c ============================================================================== --- stable/12/sys/netinet/tcp_subr.c Fri Oct 9 09:33:45 2020 (r366564) +++ stable/12/sys/netinet/tcp_subr.c Fri Oct 9 09:37:43 2020 (r366565) @@ -2941,7 +2941,6 @@ tcp_maxseg(const struct tcpcb *tp) * but this is harmless, since result of tcp_maxseg() is used * only in cwnd and ssthresh estimations. */ -#define PAD(len) ((((len) / 4) + !!((len) % 4)) * 4) if (TCPS_HAVEESTABLISHED(tp->t_state)) { if (tp->t_flags & TF_RCVD_TSTMP) optlen = TCPOLEN_TSTAMP_APPA; @@ -2949,26 +2948,26 @@ tcp_maxseg(const struct tcpcb *tp) optlen = 0; #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) if (tp->t_flags & TF_SIGNATURE) - optlen += PAD(TCPOLEN_SIGNATURE); + optlen += PADTCPOLEN(TCPOLEN_SIGNATURE); #endif if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks > 0) { optlen += TCPOLEN_SACKHDR; optlen += tp->rcv_numsacks * TCPOLEN_SACK; - optlen = PAD(optlen); + optlen = PADTCPOLEN(optlen); } } else { if (tp->t_flags & TF_REQ_TSTMP) optlen = TCPOLEN_TSTAMP_APPA; else - optlen = PAD(TCPOLEN_MAXSEG); + optlen = PADTCPOLEN(TCPOLEN_MAXSEG); if (tp->t_flags & TF_REQ_SCALE) - optlen += PAD(TCPOLEN_WINDOW); + optlen += PADTCPOLEN(TCPOLEN_WINDOW); #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) if (tp->t_flags & TF_SIGNATURE) - optlen += PAD(TCPOLEN_SIGNATURE); + optlen += PADTCPOLEN(TCPOLEN_SIGNATURE); #endif if (tp->t_flags & TF_SACK_PERMIT) - optlen += PAD(TCPOLEN_SACK_PERMITTED); + optlen += PADTCPOLEN(TCPOLEN_SACK_PERMITTED); } #undef PAD optlen = min(optlen, TCP_MAXOLEN); _______________________________________________ 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"
