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TCP: Rack ends up sending all that is outstanding every timeout.

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In doing some testing for a different problem, I have found rack retransmitting
all outstanding data every time a timeout occurs. The outstanding is sent 1ms
apart between each packet, and then the timeout runs off again. This causes
extra retransmissions when we should be waiting for an ack after sending the
very first segment.

Reviewed by: tuexen
Sponsored by: Netflix Inc
Differential Revision: https://reviews.freebsd.org/D36494
This commit is contained in:
Randall Stewart 2022-09-09 08:59:21 -04:00
parent d3791ac46a
commit 81560c5582
2 changed files with 23 additions and 1 deletions
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21
sys/netinet/tcp_stacks/rack.c
View File

@ -6685,6 +6685,7 @@ rack_timeout_rxt(struct tcpcb *tp, struct tcp_rack *rack, uint32_t cts)
}
rack->r_ctl.rc_hpts_flags &= ~PACE_TMR_RXT;
rack->r_ctl.retran_during_recovery = 0;
rack->rc_ack_required = 1;
rack->r_ctl.dsack_byte_cnt = 0;
if (IN_FASTRECOVERY(tp->t_flags))
tp->t_flags |= TF_WASFRECOVERY;
@ -14068,6 +14069,11 @@ rack_do_segment_nounlock(struct mbuf *m, struct tcphdr *th, struct socket *so,
*/
rack = (struct tcp_rack *)tp->t_fb_ptr;
if (m->m_flags & M_ACKCMP) {
/*
* All compressed ack's are ack's by definition so
* remove any ack required flag and then do the processing.
*/
rack->rc_ack_required = 0;
return (rack_do_compressed_ack_processing(tp, so, m, nxt_pkt, tv));
}
if (m->m_flags & M_ACKCMP) {
@ -14238,6 +14244,9 @@ rack_do_segment_nounlock(struct mbuf *m, struct tcphdr *th, struct socket *so,
TCP_LOG_EVENTP(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_IN, 0,
tlen, &log, true, &ltv);
}
/* Remove ack required flag if set, we have one */
if (thflags & TH_ACK)
rack->rc_ack_required = 0;
if ((thflags & TH_SYN) && (thflags & TH_FIN) && V_drop_synfin) {
way_out = 4;
retval = 0;
@ -16798,6 +16807,18 @@ rack_output(struct tcpcb *tp)
}
#ifdef TCP_ACCOUNTING
sched_unpin();
#endif
return (0);
}
if ((rack->rc_ack_required == 1) &&
(rack->r_timer_override == 0)){
/* A timeout occurred and no ack has arrived */
if (tcp_in_hpts(rack->rc_inp) == 0) {
/* Timer is not running */
rack_start_hpts_timer(rack, tp, cts, 0, 0, 0);
}
#ifdef TCP_ACCOUNTING
sched_unpin();
#endif
return (0);
}

3
sys/netinet/tcp_stacks/tcp_rack.h
View File

@ -549,7 +549,7 @@ struct tcp_rack {
struct inpcb *rc_inp; /* The inpcb Lock(a) */
uint8_t rc_free_cnt; /* Number of free entries on the rc_free list
* Lock(a) */
uint8_t client_bufferlvl : 4, /* Expected range [0,5]: 0=unset, 1=low/empty */
uint8_t client_bufferlvl : 3, /* Expected range [0,5]: 0=unset, 1=low/empty */
rack_deferred_inited : 1,
/* ******************************************************************** */
/* Note for details of next two fields see rack_init_retransmit_rate() */
@ -557,6 +557,7 @@ struct tcp_rack {
full_size_rxt: 1,
shape_rxt_to_pacing_min : 1,
/* ******************************************************************** */
rc_ack_required: 1,
spare : 1;
uint8_t no_prr_addback : 1,
gp_ready : 1,