Establish TCP connection to upstream when client connection made to listener

[Francis Daly]

On Fri, Mar 20, 2020 at 09:57:40AM -0400, Phillip Odam wrote:

Hi there,

> I'm looking for when a client establishes a TCP connection to an IP and
> port, that NGINX is listening on, that NGINX, without waiting on data being
> transmitted from the client to NGINX, would establish a TCP connection to
> the upstream.

What happened when you tried it?

A quick test here of "nc -l 9005", plus nginx.conf with

==
stream {
  server {
    listen 9001;
    proxy_pass 127.0.0.3:9005;
  }
}
==

and "tcpdump -nn -i any -X -s 0 port 9005 or port 9001", seems to show
that "nc localhost 9001" leads to a tcp handshake involving port 9001
(from the client to nginx) and a tcp handshake involving port 9005
(from nginx to the upstream).

> Trouble with this though, NGINX then can't fully support reverse proxying
> protocols where the server provides a response upon TCP connection eg. SSH2,
> MySQL. You're instead dependent on the client handling the lack of initial
> server response and that after the client sends its first lot of data it'll
> then receive the server's initial response.

Do you have a specific test case that shows this problem?

==
stream {
  server {
    listen 9001;
    proxy_pass 127.0.0.3:22;
  }
}
==

and "ssh -v -p 9001 localhost" would seem to indicate that it Just Works.

Perhaps my testing is wrong?

	f
-- 
Francis Daly        francis at daoine.org