# net_upstream

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The net_upstream kernel module provides character devices that, when opened,
automatically create proxy network interfaces. Originally the network interface
designed to add a customizable proxy before physical, internet-facing interfaces
such as VDSL interfaces.

Being a proxy, each net_upstream interface must be configured with a master
interface in order to be useful.

- In the transmit data path, packets will be forwarded to the master interface
  (or dropped if no master is configured).
- In the receive data path, every packet received on the master is passed to
  to the net_upstream interface through the `rx_handler` mechansim.

Before transmitting packets to the master there is the ability to apply *tx actions*.
These actions can modify the `struct sk_buff` or the packet data. The action
could also drop the packet.

@note Currently there is only one *tx action* implemented (mapping `skb->priority` to
PCP bits in the vlan header).

Configuration of net_upstream is usually done through IOCTLs on the character device,
however generic network interface configuration is done on associated the net_upstream
interface.

Access to the character device should not be done directly. Instead, an access library
is provided that wraps `open()`, `close()` and `ioctl()`. net_upstream_api.h has all the
details.

To see how net_upstream is used within FRITZ!OS for Internet access,
see https://wiki.avm.de/display/NW/Konzept+Datenpfad+mit+net_upstream

## GU-Autodox
[GU-Autodox](https://code.avm.de/gu-autodox/)