git: 18b83b626a4f - main - tcp: reduce the size of t_rttupdated in tcpcb

The branch main has been updated by rscheff:

URL: https://cgit.FreeBSD.org/src/commit/?id=18b83b626a4f596f1686140b99473125be9e33bf

commit 18b83b626a4f596f1686140b99473125be9e33bf
Author:     Richard Scheffenegger <rscheff@FreeBSD.org>
AuthorDate: 2023-01-26 17:07:11 +0000
Commit:     Richard Scheffenegger <rscheff@FreeBSD.org>
CommitDate: 2023-01-26 17:08:00 +0000

    tcp: reduce the size of t_rttupdated in tcpcb
    
    During tcp session start, various mechanisms need to
    track a few initial RTTs before becoming active.
    Prevent overflows of the corresponding tracking counter
    and reduce the size of tcpcb simultaneously.
    
    Reviewed By:            #transport, tuexen, guest-ccui
    Sponsored by:           NetApp, Inc.
    Differential Revision:  https://reviews.freebsd.org/D21117
---
 sys/netinet/tcp_input.c       | 3 ++-
 sys/netinet/tcp_stacks/bbr.c  | 3 ++-
 sys/netinet/tcp_stacks/rack.c | 3 ++-
 sys/netinet/tcp_usrreq.c      | 2 +-
 sys/netinet/tcp_var.h         | 2 +-
 5 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index 606f6649d73d..72faf53299e4 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -3537,7 +3537,8 @@ tcp_xmit_timer(struct tcpcb *tp, int rtt)
 	INP_WLOCK_ASSERT(tptoinpcb(tp));
 
 	TCPSTAT_INC(tcps_rttupdated);
-	tp->t_rttupdated++;
+	if (tp->t_rttupdated < UCHAR_MAX)
+		tp->t_rttupdated++;
 #ifdef STATS
 	stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RTT,
 	    imax(0, rtt * 1000 / hz));
diff --git a/sys/netinet/tcp_stacks/bbr.c b/sys/netinet/tcp_stacks/bbr.c
index 1080d53116b4..d54d213c82dd 100644
--- a/sys/netinet/tcp_stacks/bbr.c
+++ b/sys/netinet/tcp_stacks/bbr.c
@@ -6366,7 +6366,8 @@ tcp_bbr_xmit_timer_commit(struct tcp_bbr *bbr, struct tcpcb *tp, uint32_t cts)
 		tp->t_rttvar = rtt_ticks << (TCP_RTTVAR_SHIFT - 1);
 	}
 	KMOD_TCPSTAT_INC(tcps_rttupdated);
-	tp->t_rttupdated++;
+	if (tp->t_rttupdated < UCHAR_MAX)
+		tp->t_rttupdated++;
 #ifdef STATS
 	stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RTT, imax(0, rtt_ticks));
 #endif
diff --git a/sys/netinet/tcp_stacks/rack.c b/sys/netinet/tcp_stacks/rack.c
index 25a4f8dd3197..17c671705cab 100644
--- a/sys/netinet/tcp_stacks/rack.c
+++ b/sys/netinet/tcp_stacks/rack.c
@@ -7646,7 +7646,8 @@ tcp_rack_xmit_timer_commit(struct tcp_rack *rack, struct tcpcb *tp)
 	}
 	rack->rc_srtt_measure_made = 1;
 	KMOD_TCPSTAT_INC(tcps_rttupdated);
-	tp->t_rttupdated++;
+	if (tp->t_rttupdated < UCHAR_MAX)
+		tp->t_rttupdated++;
 #ifdef STATS
 	if (rack_stats_gets_ms_rtt == 0) {
 		/* Send in the microsecond rtt used for rxt timeout purposes */
diff --git a/sys/netinet/tcp_usrreq.c b/sys/netinet/tcp_usrreq.c
index 61c077ea66c6..47e635ba1faa 100644
--- a/sys/netinet/tcp_usrreq.c
+++ b/sys/netinet/tcp_usrreq.c
@@ -3068,7 +3068,7 @@ db_print_tcpcb(struct tcpcb *tp, const char *name, int indent)
 	    tp->t_rttvar, tp->t_rxtshift, tp->t_rttmin);
 
 	db_print_indent(indent);
-	db_printf("t_rttupdated: %lu   max_sndwnd: %u   t_softerror: %d\n",
+	db_printf("t_rttupdated: %u   max_sndwnd: %u   t_softerror: %d\n",
 	    tp->t_rttupdated, tp->max_sndwnd, tp->t_softerror);
 
 	db_print_indent(indent);
diff --git a/sys/netinet/tcp_var.h b/sys/netinet/tcp_var.h
index 9fca3e016d4a..5afd492189e3 100644
--- a/sys/netinet/tcp_var.h
+++ b/sys/netinet/tcp_var.h
@@ -230,7 +230,6 @@ struct tcpcb {
 	uint32_t snd_ssthresh_prev;	/* ssthresh prior to retransmit */
 	tcp_seq	snd_recover_prev;	/* snd_recover prior to retransmit */
 	int	t_sndzerowin;		/* zero-window updates sent */
-	u_long	t_rttupdated;		/* number of times rtt sampled */
 	int	snd_numholes;		/* number of holes seen by sender */
 	u_int	t_badrxtwin;		/* window for retransmit recovery */
 	TAILQ_HEAD(sackhole_head, sackhole) snd_holes;
@@ -276,6 +275,7 @@ struct tcpcb {
 	uint32_t t_dsack_bytes;		/* dsack bytes received */
 	uint32_t t_dsack_tlp_bytes;	/* dsack bytes received for TLPs sent */
 	uint32_t t_dsack_pack;		/* dsack packets we have eceived */
+	uint8_t t_rttupdated;		/* number of times rtt sampled */
 	/* TCP Fast Open */
 	uint8_t t_tfo_client_cookie_len; /* TFO client cookie length */
 	uint32_t t_end_info_status;	/* Status flag of end info */