Buffering issues with nginx

[Dan34]

Yes, I tested that and it appears to be the case. However, I don't see where
nginx sets rcvbuf on the upstream socket as this one cannot be inherited.
Somehow even with SND/RCV buffers set to low values and buffering disabled I
get around 2.5BM stuck on nginx side. With my own simple proxy I get perfect
results: when socket buffers are low there is no data accumulated on the
proxy side.

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,275526,275744#msg-275744