NetBSD Problem Report #50333

From  Mon Oct 12 22:56:45 2015
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Date: Mon, 12 Oct 2015 22:56:44 +0000 (UTC)
Subject: Netboot fails when mounting root filesystem on IPv6 enabled network
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>Number:         50333
>Category:       misc
>Synopsis:       Netboot fails when mounting root filesystem on IPv6 enabled network
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    misc-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Oct 12 23:00:00 +0000 2015
>Originator:     Aaron B
>Release:        6.1.5
NetBSD xd-build 7.0 NetBSD 7.0 (XEN3_DOMU.201509250726Z) amd64

NetBSD xd-syndev 6.1.5 NetBSD 6.1.5 (XEN3_DOMU) amd64

NetBSD focus 6.1.5 NetBSD 6.1.5 (NETRAT1) #0: Wed Dec 24 19:14:16 EST 2014  root@focus:/usr/src/sys/arch/sparc64/compile/NETRAT1 sparc64

I originally found this on NetBSD 6.1. I've confirmed it still exists on 7.0 as well; also it happens on sparc, sparc64, and amd64. The remote file server is Solaris 10/sparc. The entire network is dual stack IPv4/IPv6.

Example contents of /etc/fstab:

endure:/netfs/xd-build  /       nfs     rw,intr,tcp,nfsv3       0       0

During the boot process, the system hangs forever at /etc/rc.d/root with the following output:

root on endure:/netfs/xd-build
root file system type: nfs
warning: no /dev/console
Mon Oct 12 18:38:49 EDT 2015
Not checking /: fs_passno = 0 in /etc/fstab
mount_nfs: rpcbind to nfs on server: RPC: Port mapper failure - RPC: Unable to send

CTL-C allows it to continue normally. I believe the kernel is finding the IPv6 address via DNS and attempting to use that, but IPv6 has not yet been configured at this point in the boot process.

Attempt to netboot NetBSD 6.1 or 7.0 on a dual stack IPv4/IPv6 network.
Commenting out the 'umount' and 'mount' lines in /etc/rc.d/root allows the system to boot normally, and in 7.0 at least / gets remounted in /etc/rc.d/mountall.

Adding the file server's IPv4 address in /etc/hosts allows the system to boot normally, but disables IPv6 communication with the file server after booting.

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