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net: nonexistentdomain.golang.org returns a CNAME to golang.org #25370

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0intro opened this issue May 13, 2018 · 7 comments

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@0intro @bcmills @bradfitz @iangudger @gopherbot
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commented May 13, 2018

CL 111718 added TestLookupHostCancel.

This test sends a DNS request to nonexistentdomain.golang.org. However, this
DNS request succeeds and return a CNAME record to golang.org.

nonexistentdomain.golang.org. 86400 IN  CNAME   golang.org.
golang.org.             1800    IN      A       216.58.215.49

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@0intro 0intro referenced this issue May 13, 2018

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net: LookupHost("nonexistentdomain.golang.org"): returns [173.194.74.141 2607:f8b0:4001:c14::8d] #25361

@bradfitz bradfitz self-assigned this May 13, 2018

@bcmills bcmills added this to the Unreleased milestone May 23, 2018

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commented Oct 29, 2018

I've been seeing this from time to time in the TryBots, too:
https://storage.googleapis.com/go-build-log/2ef40d4f/windows-amd64-2016_5206ec72.log

@bradfitz bradfitz removed their assignment Oct 29, 2018

@bradfitz bradfitz added help wanted NeedsInvestigation labels Oct 29, 2018

@bradfitz bradfitz modified the milestones: Unreleased, Go1.12 Oct 29, 2018

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commented Oct 29, 2018

Ian, could you check the golang.org DNS definitions in google3?

/cc @iangudger @mdempsky @dmitshur
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commented Oct 29, 2018

It looks like we have a wildcard *.golang.org to golang.org CNAME.
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commented Oct 29, 2018

Does *.golang.org in our DNS config file also match two levels, like not.exist.golang.org?
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commented Oct 29, 2018

Yes, it seems to.
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commented Oct 29, 2018

Per discussion elsewhere, this seems to be because golang.org has an HSTS policy and Google's servers add a *.golang.org CNAME record related to that.

So I guess we could move that test to use a different domain... notexist.example.com seems to work?

@ianlancetaylor ianlancetaylor changed the title nonexistentdomain.golang.org returns a CNAME to golang.org net: nonexistentdomain.golang.org returns a CNAME to golang.org Nov 28, 2018

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commented Nov 28, 2018

Change https://golang.org/cl/151359 mentions this issue: net: use .invalid for an invalid domain name

@gopherbot gopherbot closed this in 3a60629 Nov 28, 2018

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