iservice: use saved iface index to restore metric

iservice: use saved iface index to restore metric

When adding block rules, the interface metric of the VPN adapter is
temporarily modified so that an old version of Windows 10 would pick
it up first when looking up stuff via DNS. These metrics are reverted to
the old value when the block is removed.

When reverting them, instead of using the stored interface index where
the original values were read from, we were using the interface index
passed to the service with the wfp block message. That index could
theoretically be different from the one stored, which would result in
the metric being set to the wrong interface.

Reported-by: stephan@srlabs.de
Change-Id: Ia74a931c703d594bdf8ccada9b783b94608de278
Signed-off-by: Heiko Hund <heiko@ist.eigentlich.net>
Acked-by: Lev Stipakov <lstipakov@gmail.com>
Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1363
Message-Id: <20251112215106.14182-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg34400.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>