Refactoring for configurable DNS upstreams & some other refinements

[Mygod]

I am not going to pretend I know what I am doing with these code.

[Mygod]

@madeye @zonyitoo Please review it more carefully I really do not know what I am doing.

[madeye]

Can we also have this? madeye@055b4f6

[Mygod]

With these changes, Android client should behave reasonably with any reasonable ACL file.

[madeye]

49966d9 seems breaking everything...

[Mygod]

@madeye Are you seeing 'async fn' resumed after completion? Or something else?

[Mygod]

Try 13bcc5d.

[Mygod]

@madeye @zonyitoo Done for today. Want to review these first?

[madeye]

13bcc5d works, but then 9712a97 breaks ACL again.

To reproduce the issue, please use bypass China route.

[madeye]

d1a3ac6 should fix the issue.

[madeye]

LGTM

[zonyitoo]

I am getting more and more confused about what these code are working for. LoL.

Nevermind. Since @madeye has approved, then please @Mygod merge master and fix conflicts.

[Mygod]

@zonyitoo In that case feel free to comment on where the code doesn't make sense and I can try to explain... Also maybe just merge this instead of rebasing it? There are too many commits now and I don't want to squash everything.

[zonyitoo]

I saw in ACL, resolving DomainName to IPs and then check whether IPs are in configured lists, have been removed. Why?

[zonyitoo]

Ah, my fault. I found that just now.