On Mon, Nov 02, 2015 at 11:24:51AM +0900, c wrote: > 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
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
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