Date: Mon, 7 Nov 2016 10:48:19 +0000 From: Doug Rabson <dfr@rabson.org> To: Rick Macklem <rmacklem@uoguelph.ca> Cc: "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org> Subject: Re: Mount protocol/showmount vs NFSv4 Message-ID: <CACA0VUiZ0v0js42oAkNBADfOyQV0S5BHCXwW2foV_UXG9o1Jkw@mail.gmail.com> In-Reply-To: <YTXPR01MB01893AD86D5F1280DC63CA4BDDA40@YTXPR01MB0189.CANPRD01.PROD.OUTLOOK.COM> References: <YTXPR01MB01893AD86D5F1280DC63CA4BDDA40@YTXPR01MB0189.CANPRD01.PROD.OUTLOOK.COM>
next in thread | previous in thread | raw e-mail | index | archive | help
It seems like a reasonably good idea to disable disable the mount protocol if its not needed. For NFSv4, mountd really doesn't do much other than read the exports files and push them into the kernel - does it even need to keep running after that for NFSv4? On the subject of showmount, we do have some information on connected clients which I suppose you could try to expose but its probably not worth the effort. On 6 November 2016 at 20:51, Rick Macklem <rmacklem@uoguelph.ca> wrote: > Hi, > > NFSv2 and NFSv3 use a protocol called Mount (implemented by mountd) to try > and > track mounts/unmounts and report exports to clients. Except for the one > RPC that > maps a directory path to a File Handle, none of this is needed by NFS. The > rest is > reported (and never guaranteed to be correct) by showmount(8). > > There are a couple of issues related to the Mount protocol. > 1 - It uses a dynamically assigned port# via rpcbind (which means hassles > for firewalls, etc). > 2 - umount(8) currently assumes that it is supported over UDP and fails if > it is > configured to work over TCP only. > 3 - A recent issue was reported where there is a delay for systems > configured for IP6 > only related to the handling of localhost. (I'll admit I didn't > understand quite why > there was this 2sec delay, but others familiar with networking > confirmed it was > correct behaviour.) > > NFSv4 doesn't use the Mount protocol at all and does everything via the > NFSv4 protocol > serviced at port #2049. > I have never done anything about this, since most were still using NFSv3, > but it seems > that maybe something should be done now? > - What do people think of having a new option on mountd(8) that would be > used for > NFSv4 only servers that disables servicing of Mount RPCs. > --> This would imply that "showmount" would no longer work for it. > --> Note that "showmount" returns nothing useful for NFSv4 > mounts, since mountd > doesn't know about NFSv4 mounts (and the NFSv4 server > doesn't know either, > because there is no concept of a "mount" in the NFSv4 > protocol). > --> It does imply that "showmount -e" will stop working and that > info might be > useful w.r.t. NFSv4 servers. > > Umount(8) for NFSv3 is a slightly different problem. It has (for 30years) > just talked to > UDP. If that doesn't work, there is a delay, but the umount still works > (and the info > from "showmount" is no longer correct, but it is never guaranteed to be > correct anyhow). > - Should umount(8) use TCP if the NFSv3 mount is using TCP? > --> This could cause it to break for a case where only UDP is supported > for the Mount > protocol on the server, but that would be a rare/broken case, I'd > guess. > > Anyhow, any/all comments on this would be appreciated, rick > > > _______________________________________________ > freebsd-fs@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-fs > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org" >
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CACA0VUiZ0v0js42oAkNBADfOyQV0S5BHCXwW2foV_UXG9o1Jkw>