svn commit: r354013 - head/sys/netinet/tcp_stacks

[Randall Stewart]

Author: rrs
Date: Thu Oct 24 05:54:30 2019
New Revision: 354013
URL: https://svnweb.freebsd.org/changeset/base/354013

Log:
  Fix a small bug in bbr when running under a VM. Basically what
  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 at gmail.com

Modified:
  head/sys/netinet/tcp_stacks/bbr.c

Modified: head/sys/netinet/tcp_stacks/bbr.c
==============================================================================
--- head/sys/netinet/tcp_stacks/bbr.c	Thu Oct 24 04:12:38 2019	(r354012)
+++ head/sys/netinet/tcp_stacks/bbr.c	Thu Oct 24 05:54:30 2019	(r354013)
@@ -11814,12 +11814,13 @@ bbr_do_segment_nounlock(struct mbuf *m, struct tcphdr 
 						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 timeva
 			 * 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 timeva
 					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;
 		}