Bug 1479251

Summary:	NFS over UDP does not work
Product:	[Fedora] Fedora	Reporter:	Wolfgang Denk <wd>
Component:	kernel	Assignee:	Kernel Maintainer List <kernel-maint>
Status:	CLOSED NOTABUG	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	high	Docs Contact:
Priority:	unspecified
Version:	27	CC:	gansalmon, ichavero, idealuri, itamar, jonathan, kernel-maint, labbott, madhu.chinakonda, mchehab, wd
Target Milestone:	---
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Hardware:	x86_64
OS:	Linux
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Last Closed:	2018-03-12 18:05:58 UTC	Type:	Bug
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
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Description Wolfgang Denk 2017-08-08 08:06:38 UTC

Description of problem:

After upgrading from F24 to F26 a number of diskless clients (embedded systems) stopped working.  They load the kernel image and DTB over NFS, and/or mount the rootfs over NFS.  In both cases, NFS over UDP is used. For Linux mounting the rootfs thisis not really mandatory, but for the bootloader (U-Boot) fetching the kernel image it is, since U-Boot implements only UDP.

With F25 and F26, this stopped working.  Apparently the Linux kernel in these releases does not support NFS over UDP any more.

Version-Release number of selected component (if applicable):

kernel-4.11.12-200.fc25.x86_64
kernel-4.11.11-300.fc26.x86_64

How reproducible:

Always

Steps to Reproduce:
1. Easy test: try mounting a Filesystem over NFS using UDP protocol:

mount -o udp server:/dir /dir

Actual results:

# mount -o udp sisyphus:/opt/tmp /mnt/tmp
mount.nfs: requested NFS version or transport protocol is not supported

Expected results:

Mount should succeed.

Additional info:

This restriction is blocking a pretty large number of devices from booting.
Falling back F24 on the file server is not really an option as it is no longer maintained.

Comment 1 Catalin 2017-09-19 04:02:03 UTC

Hi,

I noticed the same behaviour when I upgraded from fc24 to fc26. NFS server hosted on fc26 does not seem to accept UDP connections. Not sure if this is a bug or this is how things are supposed to be. 

Thanks,
Catalin

Comment 2 Laura Abbott 2018-02-28 03:46:17 UTC

We apologize for the inconvenience.  There is a large number of bugs to go through and several of them have gone stale. The kernel moves very fast so bugs may get fixed as part of a kernel update. Due to this, we are doing a mass bug update across all of the Fedora 26 kernel bugs.
 
Fedora 26 has now been rebased to 4.15.4-200.fc26.  Please test this kernel update (or newer) and let us know if you issue has been resolved or if it is still present with the newer kernel.
 
If you have moved on to Fedora 27, and are still experiencing this issue, please change the version to Fedora 27.
 
If you experience different issues, please open a new bug report for those.

Comment 3 Wolfgang Denk 2018-03-12 12:37:34 UTC

Problem still present in Fedora 27:

[root@pollux ~]# mount -o udp sisyphus:/opt/tmp /mnt/tmp
mount.nfs: requested NFS version or transport protocol is not supported
[root@pollux ~]# uname -a
Linux pollux.denx.de 4.14.13-300.fc27.x86_64 #1 SMP Thu Jan 11 04:00:01 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

-> ssh sisyphus uname -a
Linux sisyphus.denx.de 4.15.6-300.fc27.x86_64 #1 SMP Mon Feb 26 18:43:03 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

Comment 4 Laura Abbott 2018-03-12 18:05:58 UTC

This was an intentional change with NFSv4, see https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6da1a034362f86e157e251e65394f0b6570e3e3a