Support DNS search domain list (resolve local hostname to FQDN)

[clue]

We should support the domain and search options listed in /etc/resolv.conf (and possibly Windows' equivalent). Additionally, we should check the system hostname if it includes a domain part if the domain is not explicitly set.

This is useful in corporate and home networks where a short local alias is often used, i.e. intranet actually resolves to intranet.example.com.

See also https://linux.die.net/man/5/resolv.conf, https://linux.die.net/man/2/gethostname, https://unix.stackexchange.com/questions/128091/no-domain-defined-in-etc-resolv-conf and #98.

I'm not currently working on this, but figured it makes sense to report here in order to track this feature request. In case anybody feels like picking this up, any input and PRs would be much appreciated :+1:

[JoelFeiner]

We just ran into this issue on a project we are doing.

[nnewton]

This is of somewhat increased importance in Kubernetes deployments as service names are expanded via resolve.conf, see here: https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/#namespaces-of-services

So, it is expected to be able to resolve a service in your namespace via just its name and sometimes referring to it via its fqdn (which includes your own namespace name) can be awkward (you may not know the namespace name ahead of time/it maybe difficult to pass as an argument to that level of your application, etc)

Not a huge problem, but it was definitely a surprise when it wasn't working with a reactPHP Microservice.

[SimonFrings]

@JoelFeiner @nnewton Like @clue said, this is already planned for the longer Roadmap, but nothing we're currently working on. If you have an idea on how to implement a feature like this we're always happy about PR's 👍