tcp, udp, conf: Don't silently ignore listens on unsupported IP versions

Currently, it's possible to explicitly ask for forwarding from an IPv4
address, while disabling IPv4:
    $ pasta -t 192.0.2.1/12345 -6
or vice versa:
    $ pasta -t 2001:db8::1/12345 -4

Currently, the impossible to implement forwarding option will be silently
ignored.  That's potentially confusing since in a complex setup, it might
not be obvious why the requested forward isn't taking effect.

Specifically, it's ignored at a fairly low level: tcp_listen() and
udp_listen() ignore it and return 0.  Those run kind of late to give a
good error message.  Change the low-level functions to return
-EAFNOSUPPORT.  Most callers of {tcp,udp}_listen() ignore the return code,
so this is a no-op for them.  In the remaining caller,
conf_ports_range_except() check for the case explicitly, and provide a
meaningful error message.

Of itself, this bug is insignificant, but this is a roadblock to having
{tcp,udp}_listen() return socket fds, which in turn is a roadblock to my
flexible forwarding work.  So, might as well fix it.

Link: https://bugs.passt.top/show_bug.cgi?id=186
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

0 files changed, 0 insertions, 0 deletions