Improve description around tcp_ecn, fix the RFC number and it's not a boolean anymore since long time, and add a description for tcp_ecn_fallback. See also kernel doc under Documentation/networking/ip-sysctl.txt on tcp_ecn and tcp_ecn_fallback. Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx> --- man7/tcp.7 | 35 ++++++++++++++++++++++++++++++----- 1 file changed, 30 insertions(+), 5 deletions(-) diff --git a/man7/tcp.7 b/man7/tcp.7 index 2f290a2..0409a66 100644 --- a/man7/tcp.7 +++ b/man7/tcp.7 @@ -396,12 +396,37 @@ option. .\" Since 2.4.0-test7 Enable RFC\ 2883 TCP Duplicate SACK support. .TP -.IR tcp_ecn " (Boolean; default: disabled; since Linux 2.4)" +.IR tcp_ecn " (Integer; default: 2; since Linux 2.4)" .\" Since 2.4.0-test7 -Enable RFC\ 2884 Explicit Congestion Notification. -When enabled, connectivity to some -destinations could be affected due to older, misbehaving -routers along the path causing connections to be dropped. +Enable RFC\ 3168 Explicit Congestion Notification. + +This file can have one of the following values: +.RS +.IP 0 +Disable ECN. +Neither initiate nor accept ECN. +.IP 1 +Enable ECN when requested by incoming connections and also +request ECN on outgoing connection attempts. +.IP 2 +Enable ECN when requested by incoming connections, +but do not request ECN on outgoing connections. +.RE +.IP +When enabled, connectivity to some destinations could be affected +due to older, misbehaving middle boxes along the path, causing +connections to be dropped. +However, to facilitate and encourage deployment with option 1, and +to work around such buggy equipment, +.B tcp_ecn_fallback +option has been introduced. +.TP +.IR tcp_ecn_fallback " (Boolean; default: enabled; since Linux 4.1)" +.\" commit 492135557dc090a1abb2cfbe1a412757e3ed68ab +Enable RFC\ 3168, Section 6.1.1.1. fallback. +When enabled, outgoing ECN-setup SYNs that time out within the +normal SYN retransmission timeout will be resent with CWR and +ECE cleared. .TP .IR tcp_fack " (Boolean; default: enabled; since Linux 2.2)" .\" Since 2.1.92 -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
