Now that the back end allows passt/pasta to use different external
interfaces for IPv4 and IPv6, use that to do the right thing in the case
that the host has IPv4 and IPv6 connectivity via different interfaces.
If the user hasn't explicitly chosen an interface, separately search for
a suitable external interface for each protocol.

As a bonus, this substantially simplifies the external interface probe.  It
also eliminates a subtle confusing case where in some circumstances we
would pick the first interface in interface index order, and sometimes in
order of routes returned from netlink.  On some network configurations that
could cause tests to fail, because the logic in the tests was subtly
different (it always used route order).

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

By default, passt itself attaches to the first host interface with a
default route.  However, when determining the host interface name the tests
implicitly select the *last* host interface: they use a jq expression which
will list all interfaces with default routes, but the way output detection
works in the scripts, it will only pick up the last line.

If there are multiple interfaces with default routes on the host, and they
each have a different address, this can cause spurious test failures.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

Commit 41c02e10 ("tests: Use nmap-ncat instead of openbsd netcat for pasta
tests") updated the pasta tests to use the nmap version of ncat instead of
the openbsd version, for greater portability.

For some upcoming changes, however, we'll be wanting to use socat.
"socat" can do everything "ncat" can and more, so let's move all the
tests using host tools (either directly on the host or via mbuto
generated images) to using socat instead.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
[sbrivio: Fix a typo in port specification, 31337 instead of x31337]
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

David reports that dhclient-script(8) on Fedora needs a number of
binaries that are not included in PROGS of the current mbuto profile,
and we would also need to include hostnamectl(1) there, which will
fail without a systemd init.

Embed a minimal script for dhclient(8) in the profile itself, written
to /sbin/dhclient-script at boot, to just check what we need to check
out of DHCP and DHCPv6 functionality.

While at it, drop busybox and logger from PROGS, as we don't need them,
and add hostname(1). While DHCP option 12 isn't supported yet by the
DHCP implementation in passt, we should probably add it soon.

Note: owing to the simplicity of this script, we now need to bring up
the interface before starting dhclient: add this in test scripts where
it's not the case yet.

Reported-by: David Gibson <david@gibson.dropbear.id.au>
Suggested-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

note that we need to bring up the interface before starting dhclient

A number of tests and examples use dhclient in both IPv4 and IPv6 modes.
We use "dhclient -6" for IPv6, but usually just "dhclient" for IPv4.  Add
an explicit "-4" argument to make it more clear and explicit.

In addition, when dhclient is run from within pasta it usually won't be
"real" root, and so will not have access to write the default global pid
file.  This results in a mostly harmless but irritating error:
    Can't create /var/run/dhclient.pid: Permission denied
We can avoid that by using the --no-pid flag to dhclient.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

ip(8)'s ability to take abbreviated arguments (e.g. "li sh" instead of
"link show") is very handy when using it interactively, but it doesn't make
for very readable scripts and examples when shown that way.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

An inline comment prefixed by a space doesn't mean the space
is dropped, and sleep(1) will get a blank in its argument.

Move the comment on its own line.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

They'll start DAD as we bring up the interface, and the DHCPv6
client might be unreasonably delayed if we start it too early.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Not really quick, definitely dirty.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>