Re: [PATCH gwproxy v1 0/3] Initial work for DNS lookup implementation

[Ammar Faizi <ammarfaizi2@gnuweeb.org>]

On Fri, Aug 01, 2025 at 08:49:22AM +0700, reyuki wrote:
> I think I get the general idea of using pollable socket:
> - mark the UDP socket as non block
> - let the caller have reference to the socket, so they can poll it
> 
> But have difficulties in the technical implementation:
> 
> When the caller is notified, they must call what?

The same thing as other sockets. If you get EPOLLIN, that means there
is data to recv, so call recv/recvfrom.

> It is a UDP socket, it's said to be stateless, does connect can possibly
> return EINPROGRESS? It seems to be a common case in non-blocking

Most likely not. That will only set the dst addr. Apart from that, a
connect() call is optional if you use a UDP socket as a client.

sendto(2) and recvfrom(2) can be used if you ever want to use one
SOCK_DGRAM with multiple dst addresses.

> TCP socket. And if EAGAIN is received from recv, do we retry from send?

No, -EAGAIN from recv simply means the socket is non-blocking and there
is no data to be read at the moment.

> I find it unclear how the library and the program interact when using the
> non-blocking behavior, but I think I will give it a thought (maybe add an
> internal state to address these concerns).

The socks5 lib can do that. Why the DNS lib not?

> I can't view the linked message from the given link, is it a private community?

Oh, I didn't know if it was private. It seems the admins recently made
it private. I remember the days when it was public. But I have quoted
the needed sentences, I suppose that's enough.

-- 
Ammar Faizi