Re: [nfs-utils PATCH] statd: make statd_canonical_name emit a warning if the presentation address maps to an empty hostname

[Scott Mayhew <smayhew@redhat.com>]

On Mon, 07 Dec 2015, Chuck Lever wrote:

> 
> > On Dec 7, 2015, at 11:42 AM, Scott Mayhew <smayhew@redhat.com> wrote:
> > 
> > Certain name resolution misconfigurations (for example, a hosts file
> > entry with an ip address but no hostnames) can cause get_nameinfo() to
> > return an empty string in buf, which will lead to this cryptic failure:
> > 
> > Dec  7 09:37:44 hostname rpc.statd[8024]: Failed to insert: creating
> > /var/lib/nfs/statd/sm/: Is a directory
> > Dec  7 09:37:44 hostname rpc.statd[8024]: STAT_FAIL to
> > hostname.example.com for SM_MON of 192.168.1.2
> > Dec  7 09:37:44 hostname kernel: lockd: cannot monitor 192.168.1.2
> > 
> > It's better in that case to just go ahead and use the presentation
> > address and log a more helpful warning:
> 
> Doesn???t this change wire behavior? Some peers do not appreciate
> receiving a presentation address, which is why statd/sm_notify
> avoid sending them.

I was just trying to keep it in line with the behavior you had added in
e22f5a9c (statd: statd fails to monitor if no reverse mapping of mon_name
exists).  As it stands now, if get_nameinfo() fails outright then the
presentation address is used and we're able to monitor the peer just
fine... but get_nameinfo() succeeds and returns an empty hostname then
we ultimately wind up failing to monitor the peer.
> 
> I think it would be better to _skip_ this address and print the
> warning? IMO.
> 
That's actually what I had at first and if you think that's better then
that's fine too.  The rest of the errors would still get logged then,
but at least the reason would be a little more apparent.

-Scott
> 
> > Dec  7 10:24:52 hostname rpc.statd[14224]: get_nameinfo returned empty
> > hostname for 10.10.183.219.  Fix your name resolution!
> > 
> > Signed-off-by: Scott Mayhew <smayhew@redhat.com>
> > ---
> > utils/statd/hostname.c | 6 ++++++
> > 1 file changed, 6 insertions(+)
> > 
> > diff --git a/utils/statd/hostname.c b/utils/statd/hostname.c
> > index c61087c..86d11ca 100644
> > --- a/utils/statd/hostname.c
> > +++ b/utils/statd/hostname.c
> > @@ -211,6 +211,12 @@ statd_canonical_name(const char *hostname)
> > 			/* OK to use presentation address,
> > 			 * if no reverse map exists */
> > 			return strdup(hostname);
> > +		else if (buf[0] == '\0') {
> > +			xlog_warn("get_nameinfo returned empty hostname for "
> > +					"%s. Fix your name resolution!",
> > +					hostname);
> > +			return strdup(hostname);
> > +		}
> > 		return strdup(buf);
> > 	}
> > 
> > -- 
> > 2.4.3
> > 
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> 
> --
> Chuck Lever
> 
> 
> 
>