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Date:   Mon, 17 Apr 2023 10:05:12 +0800
From:   Wang Yugui <wangyugui@e16-tech.com>
To:     "NeilBrown" <neilb@suse.de>
Subject: Re: [PATCH nfs-utils] mountd: don't advertise krb5 for v4root when not configured.
Cc:     Steve Dickson <steved@redhat.com>, Petr Vorel <pvorel@suse.cz>,
        linux-nfs <linux-nfs@vger.kernel.org>,
        Dave Jones <davej@codemonkey.org.uk>, bfields@redhat.com
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Hi,

> 
> If /etc/krb5.keytab does not exist, then krb5 cannot work, so
> advertising it as an option for v4root is pointless.
> Since linux commit 676e4ebd5f2c ("NFSD: SECINFO doesn't handle
> unsupported pseudoflavors correctly") this can result in an unhelpful
> warning if the krb5 code is not built, or built as a module which is not
> installed.
> 
> [  161.668635] NFS: SECINFO: security flavor 390003 is not supported
> [  161.668655] NFS: SECINFO: security flavor 390004 is not supported
> [  161.668670] NFS: SECINFO: security flavor 390005 is not supported
> 
> So avoid advertising krb5 security options when krb5.keytab cannot be
> found.
> 
> Link: https://lore.kernel.org/linux-nfs/20170104190327.v3wbpcbqtfa5jy7d@codemonkey.org.uk/
> Signed-off-by: NeilBrown <neilb@suse.de>
> ---
>  support/export/v4root.c         |  2 ++
>  support/include/pseudoflavors.h |  1 +
>  support/nfs/exports.c           | 14 +++++++-------
>  3 files changed, 10 insertions(+), 7 deletions(-)
> 
> diff --git a/support/export/v4root.c b/support/export/v4root.c
> index fbb0ad5f5b81..3e049582d7c1 100644
> --- a/support/export/v4root.c
> +++ b/support/export/v4root.c
> @@ -66,6 +66,8 @@ set_pseudofs_security(struct exportent *pseudo)
>  
>  		if (!flav->fnum)
>  			continue;
> +		if (flav->need_krb5 && !access("/etc/krb5.keytab", F_OK))
> +			continue;

Could we replace "/etc/krb5.keytab" with krb5_kt_default_name()?

Best Regards
Wang Yugui (wangyugui@e16-tech.com)
2023/04/17