Configure package manager to use 127.0.0.1:8082 as proxy instead of
"magic" IP intercepted later. The listen on this port and whenever
new connection arrives, spawn qubes.UpdatesProxy service call (to
default target domain - subject to configuration in dom0) and connect
its stdin/out to the local TCP connection. This part use systemd.socket
unit in case of systemd, and ncat --exec otherwise.
On the other end - in target domain - simply pass stdin/out to updates
proxy (tinyproxy) running locally.
It's important to _not_ configure the same VM to both be updates proxy and
use it. In practice such configuration makes little sense - if VM can
access network (which is required to run updates proxy), package manager
can use it directly. Even if this network access is through some
VPN/Tor. If a single VM would be configured as both proxy provider and
proxy user, connection would loop back to itself. Because of this, proxy
connection redirection (to qrexec service) is disabled when the same VM
also run updates proxy.
FixesQubesOS/qubes-issues#1854
b49ae50ad5