#pragma once

// /dev/netdev -- being a network interface, from a process.
//
// docs/architecture/ldls.md calls this "the class bridge", and it is the one
// kernel interface LDLS needed that did not already exist. A driver hosted by LDLS produces packets
// in a process; the network stack consumes them through `struct netdev_ops` in
// the kernel. This is what joins the two.
//
// It is the exact analogue of what `display_ops` is for the GPU, and
// include/netdev.h's own opening comment already anticipated the shape:
//
//   "the stack should ask for the network interfaces and get whatever is
//    bound -- today an e1000, tomorrow a virtio-net or an rtl8139 -- exactly
//    as a compositor asks for the display and does not care which driver
//    answers."
//
// The interface is four calls wide because `netdev_ops` is, and it is
// deliberately not a superset of it. Nothing here knows what a driver is:
//
//   ioctl(NETUSERIOC_CREATE)  become an interface, with this MAC
//   read()                    a frame the stack wants sent
//   write()                   a frame that arrived on the wire
//   ioctl(NETUSERIOC_RELEASE) stop being one; exiting does this too
//
// **A process is the wire.** Whether there is real hardware on the other side
// of it is the process's business, which is what makes this usable by an
// LDLS-hosted Linux driver and equally by a test program with no hardware at
// all -- and the second one is how the first is debugged.

#include "types.h"

#define NETUSER_MAJOR 11

// One Ethernet frame, with room for the 1500-byte payload, the header and a
// VLAN tag. Frames larger than this are refused rather than truncated: a short
// frame handed to a protocol stack is a corrupt packet, which is worse than a
// dropped one.
#define NETUSER_MTU 1536

// Frames buffered in each direction. Small on purpose -- this is a queue for
// smoothing a scheduling gap, not for absorbing a burst, and a deep queue on a
// network path adds latency instead of throughput.
#define NETUSER_QLEN 16

struct netuser_create {
  uint8 mac[6];
  uint8 pad[2];
  // The interface's base name; the device model appends an index, so "ldls"
  // becomes "ldls0". Empty means "eth".
  char  name[16];
};

// Counters, for `schdbg net` and for answering "is anything moving".
struct netuser_stat {
  uint64 tx_frames, tx_bytes, tx_dropped;
  uint64 rx_frames, rx_bytes, rx_dropped;
  int    attached;              // a process holds it
  int    pad;
};

#define NETUSERIOC_CREATE   0x4e01
#define NETUSERIOC_RELEASE  0x4e02
#define NETUSERIOC_STAT     0x4e03