From f1762d6fa8cbc1a8fae691e568e73e94d5dcbc93 Mon Sep 17 00:00:00 2001 From: Florin Coras Date: Sun, 24 Sep 2017 19:43:08 -0400 Subject: tcp: do not sample rtt for retransmitted segments Change-Id: I365c31607332a944ef498369881332b515894ed7 Signed-off-by: Florin Coras --- src/vnet/tcp/tcp_input.c | 52 +++++++++++++++++++++++++----------------------- 1 file changed, 27 insertions(+), 25 deletions(-) (limited to 'src/vnet/tcp/tcp_input.c') diff --git a/src/vnet/tcp/tcp_input.c b/src/vnet/tcp/tcp_input.c index bd57eca3..0a36d063 100644 --- a/src/vnet/tcp/tcp_input.c +++ b/src/vnet/tcp/tcp_input.c @@ -248,8 +248,8 @@ tcp_update_timestamp (tcp_connection_t * tc, u32 seq, u32 seq_end) * then the TSval from the segment is copied to TS.Recent; * otherwise, the TSval is ignored. */ - if (tcp_opts_tstamp (&tc->rcv_opts) && tc->tsval_recent - && seq_leq (seq, tc->rcv_las) && seq_leq (tc->rcv_las, seq_end)) + if (tcp_opts_tstamp (&tc->rcv_opts) && seq_leq (seq, tc->rcv_las) + && seq_leq (tc->rcv_las, seq_end)) { ASSERT (timestamp_leq (tc->tsval_recent, tc->rcv_opts.tsval)); tc->tsval_recent = tc->rcv_opts.tsval; @@ -418,51 +418,53 @@ tcp_update_rto (tcp_connection_t * tc) tc->rto = clib_max (tc->rto, TCP_RTO_MIN); } -/** Update RTT estimate and RTO timer +/** + * Update RTT estimate and RTO timer * * Measure RTT: We have two sources of RTT measurements: TSOPT and ACK * timing. Middle boxes are known to fiddle with TCP options so we * should give higher priority to ACK timing. * + * This should be called only if previously sent bytes have been acked. + * * return 1 if valid rtt 0 otherwise */ static int tcp_update_rtt (tcp_connection_t * tc, u32 ack) { u32 mrtt = 0; - u8 rtx_acked; - - /* Determine if only rtx bytes are acked. */ - rtx_acked = tcp_in_cong_recovery (tc) || !tc->bytes_acked; /* Karn's rule, part 1. Don't use retransmitted segments to estimate * RTT because they're ambiguous. */ - if (tc->rtt_ts && seq_geq (ack, tc->rtt_seq) && !rtx_acked) + if (tcp_in_cong_recovery (tc) || tc->sack_sb.sacked_bytes) + goto done; + + if (tc->rtt_ts && seq_geq (ack, tc->rtt_seq)) { mrtt = tcp_time_now () - tc->rtt_ts; } /* As per RFC7323 TSecr can be used for RTTM only if the segment advances * snd_una, i.e., the left side of the send window: - * seq_lt (tc->snd_una, ack). */ - else if (tcp_opts_tstamp (&tc->rcv_opts) && tc->rcv_opts.tsecr - && tc->bytes_acked) + * seq_lt (tc->snd_una, ack). This is a condition for calling update_rtt */ + else if (tcp_opts_tstamp (&tc->rcv_opts) && tc->rcv_opts.tsecr) { mrtt = tcp_time_now () - tc->rcv_opts.tsecr; } - /* Allow measuring of a new RTT */ - tc->rtt_ts = 0; - - /* If ACK moves left side of the wnd make sure boff is 0, even if mrtt is - * not valid */ - if (tc->bytes_acked) - tc->rto_boff = 0; - /* Ignore dubious measurements */ if (mrtt == 0 || mrtt > TCP_RTT_MAX) - return 0; + goto done; tcp_estimate_rtt (tc, mrtt); + +done: + + /* Allow measuring of a new RTT */ + tc->rtt_ts = 0; + + /* If we got here something must've been ACKed so make sure boff is 0, + * even if mrrt is not valid since we update the rto lower */ + tc->rto_boff = 0; tcp_update_rto (tc); return 0; @@ -932,10 +934,11 @@ static void tcp_cc_recovery_exit (tcp_connection_t * tc) { /* Deflate rto */ - tcp_update_rto (tc); tc->rto_boff = 0; + tcp_update_rto (tc); tc->snd_rxt_ts = 0; tcp_recovery_off (tc); + TCP_EVT_DBG (TCP_EVT_CC_EVT, tc, 3); } void @@ -946,6 +949,7 @@ tcp_cc_fastrecovery_exit (tcp_connection_t * tc) tc->rcv_dupacks = 0; tcp_fastrecovery_off (tc); tcp_fastrecovery_1_smss_off (tc); + TCP_EVT_DBG (TCP_EVT_CC_EVT, tc, 3); } static void @@ -958,13 +962,14 @@ tcp_cc_congestion_undo (tcp_connection_t * tc) if (tcp_in_recovery (tc)) tcp_cc_recovery_exit (tc); ASSERT (tc->rto_boff == 0); + TCP_EVT_DBG (TCP_EVT_CC_EVT, tc, 5); /* TODO extend for fastrecovery */ } static u8 tcp_cc_is_spurious_retransmit (tcp_connection_t * tc) { - return (tcp_in_recovery (tc) + return (tcp_in_recovery (tc) && tc->rto_boff == 1 && tc->snd_rxt_ts && tcp_opts_tstamp (&tc->rcv_opts) && timestamp_lt (tc->rcv_opts.tsecr, tc->snd_rxt_ts)); @@ -988,7 +993,6 @@ tcp_cc_recover (tcp_connection_t * tc) ASSERT (tc->rto_boff == 0); ASSERT (!tcp_in_cong_recovery (tc)); ASSERT (tcp_scoreboard_is_sane_post_recovery (tc)); - TCP_EVT_DBG (TCP_EVT_CC_EVT, tc, 3); return 0; } @@ -2115,7 +2119,6 @@ tcp46_syn_sent_inline (vlib_main_t * vm, vlib_node_runtime_t * node, new_tc0->flags |= TCP_CONN_SNDACK; /* Update rtt with the syn-ack sample */ - new_tc0->bytes_acked = 1; tcp_update_rtt (new_tc0, vnet_buffer (b0)->tcp.ack_number); TCP_EVT_DBG (TCP_EVT_SYNACK_RCVD, new_tc0); } @@ -2352,7 +2355,6 @@ tcp46_rcv_process_inline (vlib_main_t * vm, vlib_node_runtime_t * node, } /* Update rtt and rto */ - tc0->bytes_acked = 1; tcp_update_rtt (tc0, vnet_buffer (b0)->tcp.ack_number); /* Switch state to ESTABLISHED */ -- cgit 1.2.3-korg