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dns/rfc2136: delete cache files if nsupdate failed #4057

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dns/rfc2136: delete cache files if nsupdate failed #4057

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dns/rfc2136: delete cache files if nsupdate failed
perryflynn Jun 24, 2024
b867292
dns/rfc2136: handle nsupdate cache files in wrapper script executed i…
perryflynn Jun 29, 2024
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16 changes: 14 additions & 2 deletions dns/rfc2136/src/etc/inc/plugins.inc.d/rfc2136.inc
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Original file line number Diff line number Diff line change
Expand Up @@ -200,14 +200,26 @@ function rfc2136_configure_do($verbose = false, $int = '', $updatehost = '', $fo
if ($need_update) {
@file_put_contents("/var/etc/nsupdatecmds{$i}", $upinst);
unset($upinst);

/* invoke nsupdate */
$cmd = "/usr/local/bin/nsupdate -k {$keyfile}";
if (isset($dnsupdate['usetcp'])) {
$cmd .= " -v";
}

$cmd .= " /var/etc/nsupdatecmds{$i}";
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Looking at the code, this stuff could really use a rewrite. The current code actually has a race condition if you ask me, the cache files(s) should only be written after an successful update, which currently isn't the case.

A short term solution could be to keep the mwexec_bg($cmd); and wrap the update action in a new shell script (src/bin/nsupdate.sh), although Ideally one should then also change the rfc2136_cache_file function to something easily predictable using the same key. If these cache files are not used anywhere else, it might be an option to calculate one key which is then used for all files (e.g. {$dnsupdate['interface']}_{$dnsupdate['host']}_{$dnsupdate['server']}{$ipver}).

The files being /var/etc/nsupdatecmds{$key}, /var/etc/nsupdatekey{$key}, /var/cache/rfc2136_{$key}_4.cache and /var/cache/rfc2136_{$key}_6.cache.

I'm not sure how to feed the complete action to /usr/sbin/daemon, but if we push it in a simple script, we only need to pass the new key and the value of usetcp, after which we could do something like:

/usr/local/bin/nsupdate -k ... || rm {both cache files}

I'm not using this myself (also don't have a test setup), but this is a direction that could work in my opinion.

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You're right, creating the cache files after the nsupdate was successful would be a better way. I try to implement that in the next week.

mwexec_bg($cmd);
unset($cmd);

//mwexec_bg($cmd);
$out = shell_exec($cmd." 2>&1; echo $?");
$status = ((int)trim(end(explode("\n", trim($out)))));

if ($status > 0) {
@unlink($cacheFile);
@unlink($cacheFile6);
log_error("Dynamic DNS: update failed, delete cache files");
}

unset($cmd, $status);
}
}

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