dns and software, was Re: Reliable Cloud host ?

Fri Mar 2 02:12:20 UTC 2012

On Mar 1, 2012, at 17:10, William Herrin <bill at herrin.us> wrote:
> If took you 50 lines of code to do
> 'socket=connect("www.google.com",80,TCP);' and you still managed to
> produce a version which, due to the timeout on dead addresses, is
> worthless for any kind of interactive program like a web browser. And
> because that code isn't found in a system library, every single
> application programmer has to write it all over again.
>
> I'm a fan of Rube Goldberg machines but that was ridiculous.

I'm thinking for this to work it would have to be 2 separate calls:

Call 1 being to the resolver (using lwres, system resolver, or
whatever you want to use) and returning an array of struct addrinfo-
same as gai does currently. If applications need TTL/SRV/$NEWRR
awareness it would be implemented here.

Call 2 would be a "happy eyeballs" connect syscall (mconnect? In the
spirit of sendmmsg) which accepts an array of struct addrinfo and
returns an fd. In the case of O_NONBLOCK it would return a dummy fd
(as non-blocking connects do currently) then once one of the
connections finishes handshake the kernel connects it to the FD and
signals writable to trigger select/poll/epoll. This allows developers
to keep using the same loops (and most of the APIs) they're already
comfortable with, keeps DNS out of the kernel, but hopefully provides
a better and easier to use connect() experience, for SOCK_STREAM at
least.

It's not as neat as a single connect() accepting a name, but seems to
be a happy medium and provides a standardized/predictable connect()
experience without breaking existing APIs.

~Matt