Now that the socket forward code is extracted we can
extend it to not just support bidirectional sockets
but also input/output fd-pairs. This will be needed
for e.g. the varlinkctl protocol upgrade support where
one side of the connection is a fd-pair (stdin/stdout).
This is done by creating two half-duplex forwarders
that operate independantly. This also allows to simplify
some state tracking, e.g. because each fd serves only one
direction we don't need to dynamically create the event mask
with EPOLLIN etc, its enough to set it once. It also handles
non-pollable FDs transparently.
Thanks to Lennart for his excellent suggestions here.
This commit extracts the socket forwarding code from the existing
socket-proxyd into a new shared helper that will be used by the
varlinkctl protocol upgrade support code and is used as is in
the socket-proxyd.c.
It tries to keep the changes as small as possible, its mostly
renaming like:
* connection_create_pipes -> socket_forward_create_pipes
* connection_shovel -> socket_forward_shovel
* connection_enable_event_sources -> socket_forward_enable_event_sources
* traffic_cb -> socket_forward_traffic_cb
and a new socket_forward_new() that creates/starts the forwarding.
All log_error_errno() got downgraded to log_debug_errno().
Michael Vogt