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Improve the ECN negotiation when the TCP SYN-cache is used by making

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sure that
* ECN is disabled if the client sends an non-ECN-setup SYN segment.
* ECN is disabled is the ECN-setup SYN-ACK segment is retransmitted more
  than net.inet.tcp.ecn.maxretries times.

Reviewed by:		rscheff
MFC after:		1 week
Sponsored by:		Netflix, Inc.
Differential Revision:	https://reviews.freebsd.org/D26008
This commit is contained in:
Michael Tuexen 2020-08-08 19:39:38 +00:00
parent d7c8186d67
commit 1bea15e601
1 changed files with 10 additions and 0 deletions
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10
sys/netinet/tcp_syncache.c
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@ -510,6 +510,9 @@ syncache_timer(void *xsch)
sch->sch_nextc = sc->sc_rxttime;
continue;
}
if (sc->sc_rxmits > V_tcp_ecn_maxretries) {
sc->sc_flags &= ~SCF_ECN;
}
if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) {
if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
log(LOG_DEBUG, "%s; %s: Retransmits exhausted, "
@ -1505,6 +1508,13 @@ syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
sc->sc_tsreflect = to->to_tsval;
else
sc->sc_flags &= ~SCF_TIMESTAMP;
/*
* Disable ECN if needed.
*/
if ((sc->sc_flags & SCF_ECN) &&
((th->th_flags & (TH_ECE|TH_CWR)) != (TH_ECE|TH_CWR))) {
sc->sc_flags &= ~SCF_ECN;
}
#ifdef MAC
/*
* Since we have already unconditionally allocated label