Date: Sun, 7 Oct 2012 13:05:21 -0400 From: Justin Hibbits <chmeeedalf@gmail.com> To: Ian Lepore <freebsd@damnhippie.dyndns.org> Cc: Garrett Cooper <yanegomi@gmail.com>, Adrian Chadd <adrian@freebsd.org>, Luigi Rizzo <rizzo@iet.unipi.it>, current@freebsd.org Subject: Re: sysctl vs ifconfig vs other (was Re: sysctl-controlled key-value store ?) Message-ID: <20121007130521.76dc7e5e@narn.knownspace> In-Reply-To: <1349626600.1112.30.camel@revolution.hippie.lan> References: <20121006172834.GB63649@onelab2.iet.unipi.it> <CAFAOGNQEAJFD2YJyRFDCzW=XMJymznW3MMdmCabbCqTjobAU-g@mail.gmail.com> <20121007104330.GA75115@onelab2.iet.unipi.it> <CAJ-VmokXxuF78HTk1SbirEwS9EP1G2RX0=LLrzMP%2B16G4-cc4g@mail.gmail.com> <20121007150219.GA76853@onelab2.iet.unipi.it> <CAGH67wTBc-RWwyQQZvbW3tufEh5xLdAswPKt3X7jMz-UP0L1VQ@mail.gmail.com> <20121007155356.GA77558@onelab2.iet.unipi.it> <1349626600.1112.30.camel@revolution.hippie.lan>
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On Sun, 07 Oct 2012 10:16:40 -0600 Ian Lepore <freebsd@damnhippie.dyndns.org> wrote: > On Sun, 2012-10-07 at 17:53 +0200, Luigi Rizzo wrote: > > Access through sysctl is incredibly easy from both userspace and > > from a C application, because all the work is done in the kernel > > side, whereas other mechanisms (ioctl, i'd rather leave kvm apart > > as we really don't want that!) require the definition of a specific > > API (ioctl, structs) _and_ some amount of wrapping code in > > userspace. > > > > cheers > > luigi > > A potential problem with sysctl is its "one thing at a time" nature. > When you pack up a bunch of related data into a structure and hand it > off to an implementation, that implementation can pretty easily make > sure that all the data related to the config request is sane. If you > have to make a series of sysctl calls to achieve some complex config > task, what happens when you're 2/3 of the way through the series and a > call fails? Who backs out the partial config that got accomplished? > > If you go too far down this path you end up with something that looks > a lot like the unmitigated mess which is the SNMP control API. > > -- Ian I agree with Ian here. As messy as ioctl+structs are from a user standpoint, they're the easiest way to guarantee atomic configuration changes. - Justin
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