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Fix a small bug in bbr when running under a VM. Basically what

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happens is we are more delayed in the pacer calling in so
we remove the stack from the pacer and recalculate how
much time is left after all data has been acknowledged. However
the comparision was backwards so we end up with a negative
value in the last_pacing_delay time which causes us to
add in a huge value to the next pacing time thus stalling
the connection.

Reported by:	vm2.finance@gmail.com
This commit is contained in:
Randall Stewart 2019-10-24 05:54:30 +00:00
parent 6087140822
commit 9992c365b6
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=354013
1 changed files with 9 additions and 3 deletions
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12
sys/netinet/tcp_stacks/bbr.c
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@ -11814,12 +11814,13 @@ bbr_do_segment_nounlock(struct mbuf *m, struct tcphdr *th, struct socket *so,
uint32_t del;
del = lcts - bbr->rc_pacer_started;
if (del > bbr->r_ctl.rc_last_delay_val) {
if (bbr->r_ctl.rc_last_delay_val > del) {
BBR_STAT_INC(bbr_force_timer_start);
bbr->r_ctl.rc_last_delay_val -= del;
bbr->rc_pacer_started = lcts;
} else {
/* We are late */
bbr->r_ctl.rc_last_delay_val = 0;
BBR_STAT_INC(bbr_force_output);
(void)tp->t_fb->tfb_tcp_output(tp);
}
@ -12278,8 +12279,9 @@ bbr_output_wtime(struct tcpcb *tp, const struct timeval *tv)
* We are early setup to adjust
* our slot time.
*/
uint64_t merged_val;
bbr->r_ctl.rc_agg_early += (bbr->r_ctl.rc_last_delay_val - delay_calc);
bbr->r_ctl.rc_last_delay_val = 0;
bbr->r_agg_early_set = 1;
if (bbr->r_ctl.rc_hptsi_agg_delay) {
if (bbr->r_ctl.rc_hptsi_agg_delay >= bbr->r_ctl.rc_agg_early) {
@ -12292,9 +12294,13 @@ bbr_output_wtime(struct tcpcb *tp, const struct timeval *tv)
bbr->r_ctl.rc_hptsi_agg_delay = 0;
}
}
merged_val = bbr->rc_pacer_started;
merged_val <<= 32;
merged_val |= bbr->r_ctl.rc_last_delay_val;
bbr_log_pacing_delay_calc(bbr, inp->inp_hpts_calls,
bbr->r_ctl.rc_agg_early, cts, 3, 0,
bbr->r_ctl.rc_agg_early, cts, delay_calc, merged_val,
bbr->r_agg_early_set, 3);
bbr->r_ctl.rc_last_delay_val = 0;
BBR_STAT_INC(bbr_early);
delay_calc = 0;
}