dns: provide generic dns_query() function

[benpicco]

Contribution description

Since we can have multiple DNS backends now, provide a common dns_query() wrapper function that allows to write backend agnostic applications.

Testing procedure

Issues/PRs references

[miri64]

sock_dtls is a bit fiddly when it comes to this (should be fixed long-term!), but does this work? If yes it makes the code a bit more easy to read. If does not work, IS_USED is preferred in any case over defined to check the usage of a module.

[benpicco]

Including dodtls.h unconditionally fails:

sys/include/net/sock/dtls.h:1001:10: fatal error: sock_dtls_types.h: No such file or directory
 1001 | #include "sock_dtls_types.h"

If does not work, IS_USED is preferred in any case over defined to check the usage of a module.

But why? I see no advantage of using IS_USED outside C code, in fact it makes the code less idiomatic.

benpicco deleted a comment from miri64 18 minutes ago

Huh I think I did delete a comment of mine 😅

[miri64]

But why? I see no advantage of using IS_USED outside C code, in fact it makes the code less idiomatic.

AFAIK, defined merely checks if the macro is defined, IS_USED also checks if the macro is either 0 or 1.

[benpicco]

Yes but under which conditions would be have MODULE_GCOAP_DNS defined to 0?

[miri64]

Yes but under which conditions would be have MODULE_GCOAP_DNS defined to 0?

Maybe testing, where you want to have that module in, but you don't want the behavior it implies in other modules, so you set CFLAGS += -DMODULE_GCOAP_DNS=0... but granted this very pretty constructed and might lead to other conflicts... so idk.

[miri64]

Yes but under which conditions would be have MODULE_GCOAP_DNS defined to 0?

Maybe testing, where you want to have that module in, but you don't want the behavior it implies in other modules, so you set CFLAGS += -DMODULE_GCOAP_DNS=0... but granted this very pretty constructed and might lead to other conflicts... so idk.

But to wrap up this discussion: using C-conditionals is not possible, because sock/dtls.h (which is included by gcoap_dtls and sock_dodtls headers) requires a sock_dtls_types.h to be present, which is only provided if a sock_dtls implementation is present. As such, C-conditionals can't be used at the moment (will try if I can do a quick fix). This only leaves #18378 (review).

[miri64]

(will try if I can do a quick fix)

See #18380. @benpicco can you try, if with that C-conditionals work?

[benpicco]

Yup that works

[miri64]

Yup that works

Than I would be very happy about an ACK in #18380 ;-)

[benpicco]

It's a two line change, can't I just include it here?

[miri64]

As long as authorship is preserved.. But even for 2 line change: I won't review my own code.

[benpicco]

But even for 2 line change: I won't review my own code.

Are you being serious? 😄
And anyway, if I cherry pick the commit, isn't that pretty much me giving it an ACK?

[miri64]

But even for 2 line change: I won't review my own code.

Are you being serious? 😄
And anyway, if I cherry pick the commit, isn't that pretty much me giving it an ACK?

Yes and yes. If I f*** up my own code and the reviewer did not test properly, the responsibility does not only lie with me. If I f*** my own code and ACK my own code with only the testing I did, the responsibility is completely with me. So, knowing myself, I'd rather avoid the risk of that 😉.

[benpicco]

Now this PR only contains commits by yours truly, you are free to review it 😉

[miri64]

ACK