Removed the Nic::Driver implementation. All nic servers now inherit from
Nic::Session_component. Packet stream signals are dispatched to
the 'handle_packet_stream' function within a session component. Thus, nic
servers now have direct access to the packet stream channels, making handling
more flexible.
Adjusted nic_loobpack, dde_ipxe, wifi, usb, lan9118, Linux nic, and OpenVPN to
the new interface.
Fixes#1602
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
