This patch supplements each existing connection type with an new
constructor that is meant to replace the original one. The new
one takes a reference to the component's environment as argument and
thereby does not rely on the presence of the globally accessible
'env()' interface.
The original constructors are marked as deprecated. Once we have
completely abolished the use of the global 'env()', we will remove them.
Fixes#1960
A Nic::Session client can install a signal handler that is used to
propagate changes of the link-state by calling 'link_state_sigh()'.
The actual link state is queried via 'link_state()'.
The nic-driver interface now provides a Driver_notification callback,
which is used to forward link-state changes from the driver to the
Nic::Session_component.
The following drivers now provide real link state: dde_ipxe, nic_bridge,
and usb_drv. Currently, OpenVPN, Linux nic_drv, and lan9118 do not
support link state and always report link up.
Fixes#1327
This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.
Issue #1082
