ip6 DNS wildcards considered harmful

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I discovered something yesterday that might be of consequence:
If you have ip6 connectivity the domain name resolver will prefer an ip6 wildcard domain over a ip4 A or CNAME record. This breaks things like ssh. You’d expect the resolver to choose the response that is most specific, the same way ip4 wildcards work, and not to blindly prefer ip6 wildcards.

Consider the case of Mary, who’s been around and has lots of domains:


and she’s also wildcarding all the other *.mary.com to her vanity host me.mary.com… you get the idea, it’s fairly typical. Those hosts only have ip4 connectivity. Now she adds a new address ip6.mary.com and puts a wildcard ip6 record *.mary.com, expecting that people accessing foo.mary.com on ip6 get the wildcard address – and they do! But she gets alot more than the doctor ordered, her ip6 clients will also get the ip6 wildcard address for all her other domains! hail.mary.com, naked.mary.com and see.mary.com will all land on ip6.mary.com instead of the ip4 A records. What happened here?
Effectively, Mary’s ip6 wildcard broke all ip6 to ip4 connectivity for Mary’s existing subdomains!

Yep, you can fix it on your machine, but this is a client problem and you can’t fix everybody else’s resolvers, so what you have to do is avoid ip6 wildcard domains ENTIRELY. Thanks a bunch.

On a completly different node:

“debug This option is recognized by pam_ldap but is presently ignored.”

I mean wow. What did they do, write the whole module flawlessly on the first try? I wish.

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