CVS commit: src/sys/netinet

["Kevin Bowling" <kbowling%netbsd.org@localhost>]

Module Name:    src
Committed By:   kbowling
Date:           Wed May 20 21:12:36 UTC 2026

Modified Files:
        src/sys/netinet: tcp_subr.c tcp_timer.h

Log Message:
tcp: set initial RTO to 1s per RFC 6298

Lower TCPTV_SRTTDFLT from 3s to 1s and adjust the t_rttvar seed in
tcp_tcpcb_template() so the pre-measurement TCP_REXMTVAL() equals
TCPTV_SRTTDFLT (was 2*TCPTV_SRTTDFLT).  Active opens and SYN|ACK
retransmits now start at 1s and back off 1, 2, 4, ... per RFC 6298
sections 2.1 and 5.5.  Post-first-sample RTO is unchanged.

Pin tcp_msl_remote_threshold to its previous numeric default (3*PR_SLOWHZ)
so the SRTTDFLT change does not move an unrelated TIME_WAIT-shortening
tunable.

This is conceptually https://reviews.freebsd.org/D18941 which we ran at a
large CDN, modified for NetBSD's stack.


To generate a diff of this commit:
cvs rdiff -u -r1.299 -r1.300 src/sys/netinet/tcp_subr.c
cvs rdiff -u -r1.30 -r1.31 src/sys/netinet/tcp_timer.h

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.