Date: Thu, 20 Feb 2025 01:25:20 +0100 From: Lars Tunkrans <drsnx60@gmail.com> To: Rick Macklem <rick.macklem@gmail.com> Cc: FreeBSD CURRENT <freebsd-current@freebsd.org>, Gleb Smirnoff <glebius@glebi.us> Subject: Re: RFC: mount_nfs failure due to dns not running yet Message-ID: <CAGB138yCGHfqCfcGewg4bWZhK0V3JmVVK-jpUwDXPrzSLuNT0A@mail.gmail.com> In-Reply-To: <CAM5tNy5wA9DyBP%2BJdq1O6J=VVtXm6Rmm5rtXjJqyJRKvJ8WY=A@mail.gmail.com>
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[-- Attachment #1 --] This situation has existed these past 40 years. You have to put your ipadress : hostname pairs into /etc/hosts if you dont have accsss to a working DNS. This is not a bug. Its the way name resolution works. Den ons 19 feb. 2025 23:40Rick Macklem <rick.macklem@gmail.com> skrev: > Hi, > > The subject line basically describes the problem glebius@ > ran into. When doing an NFS mount in /etc/fstab, it failed > since the DNS service was not yet working and, as such, > the DNS lookup of the server fqdn failed, causing the mount > to fail. Note that this behaviour has existed for decades. > > He feels this is a bug and that mount_nfs(8) should retry > getaddrinfo(3) calls until success, instead of failing the > mount when the first attempt fails. > The problem with just retrying getaddrinfo(3) is that it > could retry forever for simple failures like a typo in the > server fqdn. > I can see several ways this can be handled and would > like feedback from others w.r.t. these alternatives. > > 1) Simply document this case and encourage use of > host names in /etc/hosts for NFS servers along with > specifying use of file before dns in nsswitch.conf. > Doing this results in the mounts working whether or > not DNS is working. > > 2) Call it a bug and patch mount_nfs(8) to retry getaddrinfo(3) > until it succeeds. (I feel this would be a POLA violation, > given that the current behaviour has existed for decades > and for simple cases where the fqdn will never resolve > the behaviour would be to hang at the mount attempt > during boot unless "bg" is specified for the /etc/fstab entry.) > > 3) Add a new NFS mount option "retrydns=<N>", which would enable > retries of getaddrinfo(3). This would avoid any POLA violation and > would allow for a convenient way to document the behaviour in > "man mount_nfs". > > 4) ??? > > So, what do you think is the preferred change? > > rick > ps: I looked and the return value from getaddrinfo(3) does not > appear to be useful to discern the case of "DNS service not > running yet". (I think it replies EAI_FAIL for this case.) > > [-- Attachment #2 --] <p dir="ltr">This situation has existed these past 40 years. You have to put your ipadress : hostname pairs into /etc/hosts if you dont have accsss to a working DNS. This is not a bug. Its the way name resolution works.</p> <br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">Den ons 19 feb. 2025 23:40Rick Macklem <<a href="mailto:rick.macklem@gmail.com">rick.macklem@gmail.com</a>> skrev:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi,<br> <br> The subject line basically describes the problem glebius@<br> ran into. When doing an NFS mount in /etc/fstab, it failed<br> since the DNS service was not yet working and, as such,<br> the DNS lookup of the server fqdn failed, causing the mount<br> to fail. Note that this behaviour has existed for decades.<br> <br> He feels this is a bug and that mount_nfs(8) should retry<br> getaddrinfo(3) calls until success, instead of failing the<br> mount when the first attempt fails.<br> The problem with just retrying getaddrinfo(3) is that it<br> could retry forever for simple failures like a typo in the<br> server fqdn.<br> I can see several ways this can be handled and would<br> like feedback from others w.r.t. these alternatives.<br> <br> 1) Simply document this case and encourage use of<br> host names in /etc/hosts for NFS servers along with<br> specifying use of file before dns in nsswitch.conf.<br> Doing this results in the mounts working whether or<br> not DNS is working.<br> <br> 2) Call it a bug and patch mount_nfs(8) to retry getaddrinfo(3)<br> until it succeeds. (I feel this would be a POLA violation,<br> given that the current behaviour has existed for decades<br> and for simple cases where the fqdn will never resolve<br> the behaviour would be to hang at the mount attempt<br> during boot unless "bg" is specified for the /etc/fstab entry.)<br> <br> 3) Add a new NFS mount option "retrydns=<N>", which would enable<br> retries of getaddrinfo(3). This would avoid any POLA violation and<br> would allow for a convenient way to document the behaviour in<br> "man mount_nfs".<br> <br> 4) ???<br> <br> So, what do you think is the preferred change?<br> <br> rick<br> ps: I looked and the return value from getaddrinfo(3) does not<br> appear to be useful to discern the case of "DNS service not<br> running yet". (I think it replies EAI_FAIL for this case.)<br> <br> </blockquote></div>home | help
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