plugin/azure return FQDN as MNAME in SOA record #4286
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@@ Coverage Diff @@
## master #4286 +/- ##
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- Coverage 56.10% 56.08% -0.03%
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Files 224 224
Lines 9917 9921 +4
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Hits 5564 5564
- Misses 3892 3895 +3
- Partials 461 462 +1
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plugin/azure/azure.go
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| @@ -346,7 +346,14 @@ func (h *Azure) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) | |||
| return dns.RcodeServerFailure, nil | |||
| } | |||
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| w.WriteMsg(m) | |||
| err := w.WriteMsg(m) | |||
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we don't really care if this fails, there's nothing what we can do about, logging it will allows for easy DoS-ing of whatever these logs end up in. Please remove.
original change lgtm
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Thanks, and good point - will do. Just to check - should we log as Debug? I only ask because the logs that were written gave the impression that a response was returned to the client, when it wasn't.
I'm happy either way and will adjust the PR once you can confirm.
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hmm, true point. We can save the err and return it from the plugin, then it will be logged by errors plugin, but that would be a system wide change.
Apart from we can't pack a message because of an issue like this, failing a write to a client is not important. We could check for dns: type errors and only log those...
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I think what you propose makes sense - just return any error directly without logging. I just tried that and, as you say, it causes the errors plugin to pick it up and I see a reasonable log entry:
[ERROR] plugin/errors: 2 shop-job-adapter.sxdb-blake-dev-neu.azdevint.dh. AAAA: dns: domain must be fully qualified
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[ Quoting <notifications@github.com> in "Re: [coredns/coredns] plugin/azure ..." ]
@mancaus commented on this pull request.
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In plugin/azure/azure.go:
> @@ -346,7 +346,14 @@ func (h *Azure) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
return dns.RcodeServerFailure, nil
}
- w.WriteMsg(m)
+ err := w.WriteMsg(m)
I think what you propose makes sense - just return any error directly without
logging. I just tried that and, as you say, it causes the errors plugin to pick
it up and I see a reasonable log entry:
[ERROR] plugin/errors: 2 shop-job-adapter.sxdb-blake-dev-neu.azdevint.dh. AAAA: dns: domain must be fully qualified
yep. But this is an exception as this is a coding error in coredns, generally we don't
care about the WriteMsg error, this with rogue clients this becomes usefully wasteful.
An no matter what: this needs to be done in a different PR/issue anyway (and I'm not a
proponent of it for the reasons explained here)
/Miek
…--
Miek Gieben
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Signed-off-by: Blake Ryan <blake.ryan@dunnhumby.com>
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Thanks @miekg - this latest change to the PR reverts the error checking, so the change is back to the one-line fix for the issue itself. |
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/lgtm
/merge
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1. Why is this pull request needed and what does it do?
See #4285 - adds error handling for failure to send DNS response and ensures SOA host is an FQDN, as Azure private zones return a DNS name here currently.
2. Which issues (if any) are related?
#4285
3. Which documentation changes (if any) need to be made?
None
4. Does this introduce a backward incompatible change or deprecation?
No