Date: Sun, 27 Dec 2015 22:15:46 -0500 From: Patrick Kelsey <pkelsey@freebsd.org> To: Andrey Chernov <ache@freebsd.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-10@freebsd.org Subject: Re: svn commit: r292823 - in stable/10/sys: conf netinet Message-ID: <CAD44qMU2QEo2s2y_na5zw6U4mQWu=UWjw_vRjjFs3Q95o0iXNg@mail.gmail.com> In-Reply-To: <5680A574.9050002@freebsd.org> References: <201512280243.tBS2hD7X008202@repo.freebsd.org> <5680A574.9050002@freebsd.org>
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On Sun, Dec 27, 2015 at 9:59 PM, Andrey Chernov <ache@freebsd.org> wrote: > On 28.12.2015 5:43, Patrick Kelsey wrote: > > Author: pkelsey > > Date: Mon Dec 28 02:43:12 2015 > > New Revision: 292823 > > URL: https://svnweb.freebsd.org/changeset/base/292823 > > > > Log: > > MFC r292706: > > > > Implementation of server-side TCP Fast Open (TFO) [RFC7413]. > > > > TFO is disabled by default in the kernel build. See the top comment > > in sys/netinet/tcp_fastopen.c for implementation particulars. > > Why it is disabled by default? Do we need some rc.conf knobs to not deal > directly with it, like tcp_extensions? OMG, why it is kernel config and > not boot-time sysctl? > This is explained in the top comment in sys/netinet/tcp_fastopen.c, but I will repeat it here and elaborate a little. It is disabled by default in the kernel build as a conservative measure until it is exercised more widely, given the modifications it introduces to the TCP state machine code, syncache code, etc. When you do enable it in the kernel build (and after some point in the future when it is enabled by default), there is still a sysctl that governs its availability in the system that must be enabled before it can be used. -Patrick
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