#803731 tcp(7): tcp_ecn details out of date

Package:
manpages
Source:
manpages
Submitter:
c
Date:
2023-12-23 11:39:05 UTC
Severity:
normal
Tags:
#803731#5
Date:
2015-11-02 02:24:51 UTC
From:
To:
Dear Maintainer,

man tcp:

tcp_ecn section refers to deprecates version and talks to a boolean value defaulting to disabled.
This is not the case as kernel defaults to '2'; ip-sysctl.txt text should prevale.

tcp_ecn - INTEGER
        Control use of Explicit Congestion Notification (ECN) by TCP.
        ECN is used only when both ends of the TCP connection indicate
        support for it.  This feature is useful in avoiding losses due
        to congestion by allowing supporting routers to signal
        congestion before having to drop packets.
        Possible values are:
                0 Disable ECN.  Neither initiate nor accept ECN.
                1 Enable ECN when requested by incoming connections and
                  also request ECN on outgoing connection attempts.
                2 Enable ECN when requested by incoming connections
                  but do not request ECN on outgoing connections.
        Default: 2
#803731#14
Date:
2022-01-27 20:00:15 UTC
From:
To:
The current manpage instead reads

| tcp_ecn (Integer; default: see below; since Linux 2.4)
|        Enable RFC 3168 Explicit Congestion Notification.
|
|        This file can have one of the following values:
|
|        0      Disable ECN.  Neither initiate nor accept ECN.  This was
|        the default up to and including Linux 2.6.30.
|
|        1      Enable ECN when requested by incoming connections and
|        also request ECN on outgoing connection attempts.
|
|        2      Enable ECN when requested by incoming connections, but do
|        not request ECN on outgoing connections.  This value is
|        supported, and is the default, since Linux 2.6.31.
|
|        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, the tcp_ecn_fallback option has been
|        introduced.

I.e. the defaults are stated correctly. As such I think this bug could
just be closed.

This seems to have been fixed in man-pages-4.03 (first present in Debian
with 4.04-0.1) whose Changes lists

| tcp.7
|     Daniel Borkmann  [Michael Kerrisk]
|         Improve paragraphs on tcp_ecn and add tcp_ecn_fallback bullet
|             Improve description of 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.

Cheers,
Flo
#803731#19
Date:
2023-12-23 11:30:37 UTC
From:
To:
Hello Tobias,
Am Thu, Jan 27, 2022 at 09:00:15PM +0100 schrieb Florian Ernst:

This analysis sounds sensible, should this bug be closed?

Greetings

         Helge