DNS should be case insensitive

[provonet]

DNS resolving is now case sensitive which makes it impossible to ssh in to a server or container if there is a capital letter in the hostname.

example:

ping postgresql.node.consul
ping: unknown host postgresql.node.consul

but:

ping Postgresql.node.consul
PING Postgresql.node.consul (172.17.0.5) 56(84) bytes of data.
64 bytes from 172.17.0.5: icmp_seq=1 ttl=64 time=0.061 ms
64 bytes from 172.17.0.5: icmp_seq=2 ttl=64 time=0.078 ms

[provonet]

Forgot to add the used version, we are using version 0.2.1

[andrewwatson]

yikes, DNS is definitely not sensitive per the RFC. 👍

[armon]

So an interesting mis-match we have is that Consul IS case-sensitive for tags + services.
Meaning, if there happens to be a "foo" and "Foo" tag for the "postgresql" service, "foo.postgresql.service.consul" and "Foo.postgresql.service.consul" actually resolve differently.

I'm not sure how to handle case-insensitive DNS without creating an ambiguity in the lookup.

[armon]

Similarly the "postgresql" and "POSTGRESQL" service are allowed to be distinct

[carlosdp]

What is the use-case for having two tags/services of the same name with different casing?

[armon]

No good use case. On thinking about this further, Consul does not currently definite case sensitivity, so we wouldn't be breaking a backwards compatibility promise. Instead, we can define case-insensitive and both fix this bug and have more clearly defined semantics. This may not happen for 0.3 but maybe 0.4

[tiwilliam]

I had a look at this yesterday and got all interfaces case-insensitive, still need some refactoring but I'm working on this.

[armon]

@tiwilliam Awesome. I'd love to talk more about this while you are working on it. I think that largely we can do this all in the state store by just doing a ToLower on all the indexes and corresponding read values. I think most of the changes can actually be localized to the MDBTable

[tiwilliam]

Yeah, that's basically what I have, and then ToLower in DNSServer.dispatch etc. I did the ToLower on one level above the MDBTable when storing, but I can try to move it.