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net: DNS client relies on CNAME order #34677

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iangudger opened this issue Oct 3, 2019 · 2 comments
Closed

net: DNS client relies on CNAME order #34677

iangudger opened this issue Oct 3, 2019 · 2 comments

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@iangudger
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@iangudger iangudger commented Oct 3, 2019

According to RFC 1034, section 3.6:

The order of RRs in a set is not significant, and need not be preserved by name servers, resolvers, or other parts of the DNS.

The current DNS client is relying on the RR order in order to determine the CNAME (source). I think this works because most DNS servers do serve CNAMES in a significant order.

/cc @mdempsky

@andybons andybons added this to the Unplanned milestone Oct 3, 2019
@mdempsky
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@mdempsky mdempsky commented Oct 3, 2019

That code is grabbing the A/AAAA RRset owner name as a way to short circuit having to walk any CNAME chain. The logic is explained on lines 631–644.

@iangudger
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@iangudger iangudger commented Oct 3, 2019

You're right.

@iangudger iangudger closed this Oct 3, 2019
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