Date: Thu, 19 Dec 2013 15:57:35 +0400 From: Gleb Smirnoff <glebius@FreeBSD.org> To: John Baldwin <jhb@freebsd.org> Cc: svn-src-head@freebsd.org, John-Mark Gurney <jmg@funkthat.com>, src-committers@freebsd.org, "Alexander V. Chernikov" <melifaro@freebsd.org>, svn-src-all@freebsd.org Subject: Re: svn commit: r259562 - head/usr.bin/netstat Message-ID: <20131219115735.GN29088@FreeBSD.org> In-Reply-To: <201312181640.52147.jhb@freebsd.org> References: <201312181825.rBIIPR25014515@svn.freebsd.org> <20131218184512.GM99167@funkthat.com> <52B2009E.1060905@FreeBSD.org> <201312181640.52147.jhb@freebsd.org>
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On Wed, Dec 18, 2013 at 04:40:52PM -0500, John Baldwin wrote: J> On Wednesday, December 18, 2013 3:07:58 pm Alexander V. Chernikov wrote: J> > On 18.12.2013 22:45, John-Mark Gurney wrote: J> > > Alexander V. Chernikov wrote this message on Wed, Dec 18, 2013 at 18:25 +0000: J> > >> Author: melifaro J> > >> Date: Wed Dec 18 18:25:27 2013 J> > >> New Revision: 259562 J> > >> URL: http://svnweb.freebsd.org/changeset/base/259562 J> > >> J> > >> Log: J> > >> Switch netstat -rn to use standard API for retrieving list of routes J> > >> instead of peeking inside in-kernel radix via kget. J> > >> This permits us to change kernel structures without breaking userland. J> > >> Additionally, this change provide more reliable and faster output. J> > >> J> > >> `Refs` and `Use` fields available in IPv4 by default (and via -W J> > >> for other families) were removed. `Refs` is radix-specific thing J> > >> which is not informative for users. `Use` field value is handy sometimes, J> > >> but a) current API does not support it and b) I'm not sure we will J> > >> support per-rte pcpu counters in near future. J> > >> J> > >> Old method of retrieving data is still supported (either by defining J> > >> NewTree=0 or running netstat with -A). However, Refs/Use fields are J> > >> hidden. J> > >> J> > >> Sponsored by: Yandex LLC J> > >> MFC after: 4 weeks J> > >> PR: kern/167204 J> > > J> > > How will this impact the use of netstat -rn -M vmcore -N kernel ? Will J> > > this change make it not usable, or will you still automatically use J> > Well. It will probably break in (maybe, near) future. J> J> Please don't gratuitiously break things that /usr/sbin/crashinfo runs. It's J> fine if kvm mode is fragile and requires the binary to be in sync with the J> kernel and is only used for crash dumps, but it is very useful to extract J> all sorts of info out of a crash dump. The problem is that these tools (netstat, and some others) prevent us from improving the kernel network stack. We can't make improvements that are mergeable to stable/x branch, since the tools would be broken. Moreover any improvement in head/, requires from developer additional work in netstat code, which I must admit isn't a pleasure to work with. And any improvement in head adds additional incompatibility between newer kernel and older world, which is of course allowed in CURRENT, but still we'd prefer to reduce number of such events. I agree that usage of tools on vmcores is useful. But we all should agree that it has very limited use. Only kernel hackers and developers are expected to do this. However, speaking of myself, I was never interested in routing table from a vmcore neither interface statistics, when fixing a bug in networking stack, and I've fixed quite a lot of them. Still, I believe, that some developers find this useful. My suggestion is that all this code is deleted from src/usr.bin/netstat, and moved to src/tools, and we relax assertion that src/tools must be compatible with any kernel within the branch. So, any person who wants this functionality, needs to keep his src/tools in sync with kernel and compile a tool when he desires to dump routing table from a vmcore. Finally, when we remove all the kvm(3) usage from a tool, then we can remove the sugid bit from it, which would be a another fine point. -- Totus tuus, Glebius.
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