Not support local hosts file? about domain

[partim]

Quick update: I started the netdb crate and put together a preliminary implementation of get_host_by_name() and its async companion, tentatively named poll_host_by_name(). Needs testing and documenting and examples before it can go onto crates.io even in its really limited state, though.

[partim]

I tend to not want to support this in the domain crate since it is intended for DNS only.

What I would like to do instead is start a new crate that mimics NSS and not only considers /etc/hosts but also /etc/nsswitch.conf and perhaps even allows binding NSS .so libraries. An initial version could only provide name resolution with DNS and the hosts file, to make this functionality available quickly.

How does that sound?

[Matrix-Zhang]

i think it is not easy to program, because of we don't know the end-user's system environment, there must someone want to use hosts file directly, like me? As a programmer, we should use two crates's functions to resolve the host name? i suggest integrated into domain, just like c api, gethostbyname

[partim]

Sorry, I was unclear: The idea is to provide a single crate that performs the lookups such as that performed by `gethostbyname()` in a simple way and correctly for whatever platform you are on. Ie., you wouldn't be using `domain` at all anymore but only that new crate.

[tailhook]

Binding to .so in async program doesn't make sense. Either use gethostbyname() directly (in a thread) or make normal async resolver with things that's possible to do asynchronously.

[partim]

In pretty much all setups the nsswitch.conf entry for hosts is effectively files dns (safe for alternative resolvers which can be translated into appropriate domain configuration once it supports whatever additional functionality those resolvers provide). It would still be nice if packages could behave correctly in the fraction of cases that differ. For instance, if I removed the files entry from nsswitch.conf (because I have a complex hosts file which I want to disable temporarily), it would be nice it Things Just Worked.

For async use, the .so bindings could be forked into a thread pool.

[tailhook]

Well, here is the stock nsswitch.conf from nix:

hosts:     files  dns   myhostname mymachines

mdns and mdns_minimal are also common (as allows service discovery, e.g. to find printers as easy as on other OSs)
systemd is also going to gain popularity just because it's installed everywhere
I'm not sure about ldap

[partim]

Most of this should be supported by the new crate natively, perhaps even ldap if we have an underlying crate for it—a protocol as complex as LDAP would particularly benefit from using a Rust implementation.

[tailhook]

Yes. That would be great. But it's a hell of a lot of work :)

[partim]

I’m happy to at least get started. I am somewhat busy with life stuff the next weeks, though, but I’ll start a crate that pulls together the hosts file stuff (a parser for which actually is already present in domain) and the resolver, sometime soon. That will hopefully solve @Matrix-Zhang’s use case and then we can see where we go from there.

[Matrix-Zhang]

I see, thanks for your hard wrok

[zonyitoo]

@partim what's the status of netdb crate?

[partim]

I’ve been caught up in moving the last two weeks but things have calmed down now. Hoping to get the remaining stuff done perhaps this weekend already, otherwise early next week.

[partim]

Version 0.1.0 of netdb has just been uploaded to crates.io. It really only is a start just now, but it should allow closing this issue.