/*
   * Xenbus code for netif backend
   *
   * Copyright (C) 2005 Rusty Russell <rusty@rustcorp.com.au>
   * Copyright (C) 2005 XenSource Ltd
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, see <http://www.gnu.org/licenses/>.
  */
  
  #include "common.h"
  
  struct backend_info {
  	struct xenbus_device *dev;
  	struct xenvif *vif;
  
  	/* This is the state that will be reflected in xenstore when any
  	 * active hotplug script completes.
  	 */
  	enum xenbus_state state;
  
  	enum xenbus_state frontend_state;
  	struct xenbus_watch hotplug_status_watch;
  	u8 have_hotplug_status_watch:1;
  };
  
  static int connect_rings(struct backend_info *);
  static void connect(struct backend_info *);
  static void backend_create_xenvif(struct backend_info *be);
  static void unregister_hotplug_status_watch(struct backend_info *be);
  static void set_backend_state(struct backend_info *be,
  			      enum xenbus_state state);
  
  static int netback_remove(struct xenbus_device *dev)
  {
  	struct backend_info *be = dev_get_drvdata(&dev->dev);
  
  	set_backend_state(be, XenbusStateClosed);
  
  	unregister_hotplug_status_watch(be);
  	if (be->vif) {
  		kobject_uevent(&dev->dev.kobj, KOBJ_OFFLINE);
  		xenbus_rm(XBT_NIL, dev->nodename, "hotplug-status");
  		xenvif_free(be->vif);
  		be->vif = NULL;
  	}
  	kfree(be);
  	dev_set_drvdata(&dev->dev, NULL);
  	return 0;
  }
  
  
  /**
   * Entry point to this code when a new device is created.  Allocate the basic
   * structures and switch to InitWait.
   */
  static int netback_probe(struct xenbus_device *dev,
  			 const struct xenbus_device_id *id)
  {
  	const char *message;
  	struct xenbus_transaction xbt;
  	int err;
  	int sg;
  	struct backend_info *be = kzalloc(sizeof(struct backend_info),
  					  GFP_KERNEL);
  	if (!be) {
  		xenbus_dev_fatal(dev, -ENOMEM,
  				 "allocating backend structure");
  		return -ENOMEM;
  	}
  
  	be->dev = dev;
  	dev_set_drvdata(&dev->dev, be);
  
  	sg = 1;
  
  	do {
  		err = xenbus_transaction_start(&xbt);
  		if (err) {
  			xenbus_dev_fatal(dev, err, "starting transaction");
  			goto fail;
  		}
  
  		err = xenbus_printf(xbt, dev->nodename, "feature-sg", "%d", sg);
  		if (err) {
  			message = "writing feature-sg";
  			goto abort_transaction;
  		}
  
  		err = xenbus_printf(xbt, dev->nodename, "feature-gso-tcpv4",
  				    "%d", sg);
  		if (err) {
  			message = "writing feature-gso-tcpv4";
  			goto abort_transaction;
  		}
  
  		err = xenbus_printf(xbt, dev->nodename, "feature-gso-tcpv6",
  				    "%d", sg);
  		if (err) {
  			message = "writing feature-gso-tcpv6";
  			goto abort_transaction;
  		}
  
  		/* We support partial checksum setup for IPv6 packets */
  		err = xenbus_printf(xbt, dev->nodename,
  				    "feature-ipv6-csum-offload",
  				    "%d", 1);
  		if (err) {
  			message = "writing feature-ipv6-csum-offload";
  			goto abort_transaction;
  		}
  
  		/* We support rx-copy path. */
  		err = xenbus_printf(xbt, dev->nodename,
  				    "feature-rx-copy", "%d", 1);
  		if (err) {
  			message = "writing feature-rx-copy";
  			goto abort_transaction;
  		}
  
  		/*
  		 * We don't support rx-flip path (except old guests who don't
  		 * grok this feature flag).
  		 */
  		err = xenbus_printf(xbt, dev->nodename,
  				    "feature-rx-flip", "%d", 0);
  		if (err) {
  			message = "writing feature-rx-flip";
  			goto abort_transaction;
  		}
  
  		err = xenbus_transaction_end(xbt, 0);
  	} while (err == -EAGAIN);
  
  	if (err) {
  		xenbus_dev_fatal(dev, err, "completing transaction");
  		goto fail;
  	}
  
  	/*
  	 * Split event channels support, this is optional so it is not
  	 * put inside the above loop.
  	 */
  	err = xenbus_printf(XBT_NIL, dev->nodename,
  			    "feature-split-event-channels",
  			    "%u", separate_tx_rx_irq);
  	if (err)
  		pr_debug("Error writing feature-split-event-channels
  ");
  
  	err = xenbus_switch_state(dev, XenbusStateInitWait);
  	if (err)
  		goto fail;
  
  	be->state = XenbusStateInitWait;
  
  	/* This kicks hotplug scripts, so do it immediately. */
  	backend_create_xenvif(be);
  
  	return 0;
  
  abort_transaction:
  	xenbus_transaction_end(xbt, 1);
  	xenbus_dev_fatal(dev, err, "%s", message);
  fail:
  	pr_debug("failed
  ");
  	netback_remove(dev);
  	return err;
  }
  
  
  /*
   * Handle the creation of the hotplug script environment.  We add the script
   * and vif variables to the environment, for the benefit of the vif-* hotplug
   * scripts.
   */
  static int netback_uevent(struct xenbus_device *xdev,
  			  struct kobj_uevent_env *env)
  {
  	struct backend_info *be = dev_get_drvdata(&xdev->dev);
  	char *val;
  
  	val = xenbus_read(XBT_NIL, xdev->nodename, "script", NULL);
  	if (IS_ERR(val)) {
  		int err = PTR_ERR(val);
  		xenbus_dev_fatal(xdev, err, "reading script");
  		return err;
  	} else {
  		if (add_uevent_var(env, "script=%s", val)) {
  			kfree(val);
  			return -ENOMEM;
  		}
  		kfree(val);
  	}
  
  	if (!be || !be->vif)
  		return 0;
  
  	return add_uevent_var(env, "vif=%s", be->vif->dev->name);
  }
  
  
  static void backend_create_xenvif(struct backend_info *be)
  {
  	int err;
  	long handle;
  	struct xenbus_device *dev = be->dev;
  
  	if (be->vif != NULL)
  		return;
  
  	err = xenbus_scanf(XBT_NIL, dev->nodename, "handle", "%li", &handle);
  	if (err != 1) {
  		xenbus_dev_fatal(dev, err, "reading handle");
  		return;
  	}
  
  	be->vif = xenvif_alloc(&dev->dev, dev->otherend_id, handle);
  	if (IS_ERR(be->vif)) {
  		err = PTR_ERR(be->vif);
  		be->vif = NULL;
  		xenbus_dev_fatal(dev, err, "creating interface");
  		return;
  	}
  
  	kobject_uevent(&dev->dev.kobj, KOBJ_ONLINE);
  }
  
  static void backend_disconnect(struct backend_info *be)
  {
  	if (be->vif)
  		xenvif_disconnect(be->vif);
  }
  
  static void backend_connect(struct backend_info *be)
  {
  	if (be->vif)
  		connect(be);
  }
  
  static inline void backend_switch_state(struct backend_info *be,
  					enum xenbus_state state)
  {
  	struct xenbus_device *dev = be->dev;
  
  	pr_debug("%s -> %s
  ", dev->nodename, xenbus_strstate(state));
  	be->state = state;
  
  	/* If we are waiting for a hotplug script then defer the
  	 * actual xenbus state change.
  	 */
  	if (!be->have_hotplug_status_watch)
  		xenbus_switch_state(dev, state);
  }
  
  /* Handle backend state transitions:
   *
   * The backend state starts in InitWait and the following transitions are
   * allowed.
   *
   * InitWait -> Connected
   *
   *    ^    \         |
   *    |     \        |
   *    |      \       |
   *    |       \      |
   *    |        \     |
   *    |         \    |
   *    |          V   V
   *
   *  Closed  <-> Closing
   *
   * The state argument specifies the eventual state of the backend and the
   * function transitions to that state via the shortest path.
   */
  static void set_backend_state(struct backend_info *be,
  			      enum xenbus_state state)
  {
  	while (be->state != state) {
  		switch (be->state) {
  		case XenbusStateClosed:
  			switch (state) {
  			case XenbusStateInitWait:
  			case XenbusStateConnected:
  				pr_info("%s: prepare for reconnect
  ",
  					be->dev->nodename);
  				backend_switch_state(be, XenbusStateInitWait);
  				break;
  			case XenbusStateClosing:
  				backend_switch_state(be, XenbusStateClosing);
  				break;
  			default:
  				BUG();
  			}
  			break;
  		case XenbusStateInitWait:
  			switch (state) {
  			case XenbusStateConnected:
  				backend_connect(be);
  				backend_switch_state(be, XenbusStateConnected);
  				break;
  			case XenbusStateClosing:
  			case XenbusStateClosed:
  				backend_switch_state(be, XenbusStateClosing);
  				break;
  			default:
  				BUG();
  			}
  			break;
  		case XenbusStateConnected:
  			switch (state) {
  			case XenbusStateInitWait:
  			case XenbusStateClosing:
  			case XenbusStateClosed:
  				backend_disconnect(be);
  				backend_switch_state(be, XenbusStateClosing);
  				break;
  			default:
  				BUG();
  			}
  			break;
  		case XenbusStateClosing:
  			switch (state) {
  			case XenbusStateInitWait:
  			case XenbusStateConnected:
  			case XenbusStateClosed:
  				backend_switch_state(be, XenbusStateClosed);
  				break;
  			default:
  				BUG();
  			}
  			break;
  		default:
  			BUG();
  		}
  	}
  }
  
  /**
   * Callback received when the frontend's state changes.
   */
  static void frontend_changed(struct xenbus_device *dev,
  			     enum xenbus_state frontend_state)
  {
  	struct backend_info *be = dev_get_drvdata(&dev->dev);
  
  	pr_debug("%s -> %s
  ", dev->otherend, xenbus_strstate(frontend_state));
  
  	be->frontend_state = frontend_state;
  
  	switch (frontend_state) {
  	case XenbusStateInitialising:
  		set_backend_state(be, XenbusStateInitWait);
  		break;
  
  	case XenbusStateInitialised:
  		break;
  
  	case XenbusStateConnected:
  		set_backend_state(be, XenbusStateConnected);
  		break;
  
  	case XenbusStateClosing:
  		set_backend_state(be, XenbusStateClosing);
  		break;
  
  	case XenbusStateClosed:
  		set_backend_state(be, XenbusStateClosed);
  		if (xenbus_dev_is_online(dev))
  			break;
  		/* fall through if not online */
  	case XenbusStateUnknown:
  		set_backend_state(be, XenbusStateClosed);
  		device_unregister(&dev->dev);
  		break;
  
  	default:
  		xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
  				 frontend_state);
  		break;
  	}
  }
  
  
  static void xen_net_read_rate(struct xenbus_device *dev,
  			      unsigned long *bytes, unsigned long *usec)
  {
  	char *s, *e;
  	unsigned long b, u;
  	char *ratestr;
  
  	/* Default to unlimited bandwidth. */
  	*bytes = ~0UL;
  	*usec = 0;
  
  	ratestr = xenbus_read(XBT_NIL, dev->nodename, "rate", NULL);
  	if (IS_ERR(ratestr))
  		return;
  
  	s = ratestr;
  	b = simple_strtoul(s, &e, 10);
  	if ((s == e) || (*e != ','))
  		goto fail;
  
  	s = e + 1;
  	u = simple_strtoul(s, &e, 10);
  	if ((s == e) || (*e != '\0'))
  		goto fail;
  
  	*bytes = b;
  	*usec = u;
  
  	kfree(ratestr);
  	return;
  
   fail:
  	pr_warn("Failed to parse network rate limit. Traffic unlimited.
  ");
  	kfree(ratestr);
  }
  
  static int xen_net_read_mac(struct xenbus_device *dev, u8 mac[])
  {
  	char *s, *e, *macstr;
  	int i;
  
  	macstr = s = xenbus_read(XBT_NIL, dev->nodename, "mac", NULL);
  	if (IS_ERR(macstr))
  		return PTR_ERR(macstr);
  
  	for (i = 0; i < ETH_ALEN; i++) {
  		mac[i] = simple_strtoul(s, &e, 16);
  		if ((s == e) || (*e != ((i == ETH_ALEN-1) ? '\0' : ':'))) {
  			kfree(macstr);
  			return -ENOENT;
  		}
  		s = e+1;
  	}
  
  	kfree(macstr);
  	return 0;
  }
  
  static void unregister_hotplug_status_watch(struct backend_info *be)
  {
  	if (be->have_hotplug_status_watch) {
  		unregister_xenbus_watch(&be->hotplug_status_watch);
  		kfree(be->hotplug_status_watch.node);
  	}
  	be->have_hotplug_status_watch = 0;
  }
  
  static void hotplug_status_changed(struct xenbus_watch *watch,
  				   const char **vec,
  				   unsigned int vec_size)
  {
  	struct backend_info *be = container_of(watch,
  					       struct backend_info,
  					       hotplug_status_watch);
  	char *str;
  	unsigned int len;
  
  	str = xenbus_read(XBT_NIL, be->dev->nodename, "hotplug-status", &len);
  	if (IS_ERR(str))
  		return;
  	if (len == sizeof("connected")-1 && !memcmp(str, "connected", len)) {
  		/* Complete any pending state change */
  		xenbus_switch_state(be->dev, be->state);
  
  		/* Not interested in this watch anymore. */
  		unregister_hotplug_status_watch(be);
  	}
  	kfree(str);
  }
  
  static void connect(struct backend_info *be)
  {
  	int err;
  	struct xenbus_device *dev = be->dev;
  
  	err = connect_rings(be);
  	if (err)
  		return;
  
  	err = xen_net_read_mac(dev, be->vif->fe_dev_addr);
  	if (err) {
  		xenbus_dev_fatal(dev, err, "parsing %s/mac", dev->nodename);
  		return;
  	}
  
  	xen_net_read_rate(dev, &be->vif->credit_bytes,
  			  &be->vif->credit_usec);
  	be->vif->remaining_credit = be->vif->credit_bytes;
  
  	unregister_hotplug_status_watch(be);
  	err = xenbus_watch_pathfmt(dev, &be->hotplug_status_watch,
  				   hotplug_status_changed,
  				   "%s/%s", dev->nodename, "hotplug-status");
  	if (!err)
  		be->have_hotplug_status_watch = 1;
  
  	netif_wake_queue(be->vif->dev);
  }
  
  
  static int connect_rings(struct backend_info *be)
  {
  	struct xenvif *vif = be->vif;
  	struct xenbus_device *dev = be->dev;
  	unsigned long tx_ring_ref, rx_ring_ref;
  	unsigned int tx_evtchn, rx_evtchn, rx_copy;
  	int err;
  	int val;
  
  	err = xenbus_gather(XBT_NIL, dev->otherend,
  			    "tx-ring-ref", "%lu", &tx_ring_ref,
  			    "rx-ring-ref", "%lu", &rx_ring_ref, NULL);
  	if (err) {
  		xenbus_dev_fatal(dev, err,
  				 "reading %s/ring-ref",
  				 dev->otherend);
  		return err;
  	}
  
  	/* Try split event channels first, then single event channel. */
  	err = xenbus_gather(XBT_NIL, dev->otherend,
  			    "event-channel-tx", "%u", &tx_evtchn,
  			    "event-channel-rx", "%u", &rx_evtchn, NULL);
  	if (err < 0) {
  		err = xenbus_scanf(XBT_NIL, dev->otherend,
  				   "event-channel", "%u", &tx_evtchn);
  		if (err < 0) {
  			xenbus_dev_fatal(dev, err,
  					 "reading %s/event-channel(-tx/rx)",
  					 dev->otherend);
  			return err;
  		}
  		rx_evtchn = tx_evtchn;
  	}
  
  	err = xenbus_scanf(XBT_NIL, dev->otherend, "request-rx-copy", "%u",
  			   &rx_copy);
  	if (err == -ENOENT) {
  		err = 0;
  		rx_copy = 0;
  	}
  	if (err < 0) {
  		xenbus_dev_fatal(dev, err, "reading %s/request-rx-copy",
  				 dev->otherend);
  		return err;
  	}
  	if (!rx_copy)
  		return -EOPNOTSUPP;
  
  	if (vif->dev->tx_queue_len != 0) {
  		if (xenbus_scanf(XBT_NIL, dev->otherend,
  				 "feature-rx-notify", "%d", &val) < 0)
  			val = 0;
  		if (val)
  			vif->can_queue = 1;
  		else
  			/* Must be non-zero for pfifo_fast to work. */
  			vif->dev->tx_queue_len = 1;
  	}
  
  	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-sg",
  			 "%d", &val) < 0)
  		val = 0;
  	vif->can_sg = !!val;
  
  	vif->gso_mask = 0;
  	vif->gso_prefix_mask = 0;
  
  	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv4",
  			 "%d", &val) < 0)
  		val = 0;
  	if (val)
  		vif->gso_mask |= GSO_BIT(TCPV4);
  
  	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv4-prefix",
  			 "%d", &val) < 0)
  		val = 0;
  	if (val)
  		vif->gso_prefix_mask |= GSO_BIT(TCPV4);
  
  	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv6",
  			 "%d", &val) < 0)
  		val = 0;
  	if (val)
  		vif->gso_mask |= GSO_BIT(TCPV6);
  
  	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv6-prefix",
  			 "%d", &val) < 0)
  		val = 0;
  	if (val)
  		vif->gso_prefix_mask |= GSO_BIT(TCPV6);
  
  	if (vif->gso_mask & vif->gso_prefix_mask) {
  		xenbus_dev_fatal(dev, err,
  				 "%s: gso and gso prefix flags are not "
  				 "mutually exclusive",
  				 dev->otherend);
  		return -EOPNOTSUPP;
  	}
  
  	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-no-csum-offload",
  			 "%d", &val) < 0)
  		val = 0;
  	vif->ip_csum = !val;
  
  	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-ipv6-csum-offload",
  			 "%d", &val) < 0)
  		val = 0;
  	vif->ipv6_csum = !!val;
  
  	/* Map the shared frame, irq etc. */
  	err = xenvif_connect(vif, tx_ring_ref, rx_ring_ref,
  			     tx_evtchn, rx_evtchn);
  	if (err) {
  		xenbus_dev_fatal(dev, err,
  				 "mapping shared-frames %lu/%lu port tx %u rx %u",
  				 tx_ring_ref, rx_ring_ref,
  				 tx_evtchn, rx_evtchn);
  		return err;
  	}
  	return 0;
  }
  
  
  /* ** Driver Registration ** */
  
  
  static const struct xenbus_device_id netback_ids[] = {
  	{ "vif" },
  	{ "" }
  };
  
  
  static DEFINE_XENBUS_DRIVER(netback, ,
  	.probe = netback_probe,
  	.remove = netback_remove,
  	.uevent = netback_uevent,
  	.otherend_changed = frontend_changed,
  );
  
  int xenvif_xenbus_init(void)
  {
  	return xenbus_register_backend(&netback_driver);
  }
  
  void xenvif_xenbus_fini(void)
  {
  	return xenbus_unregister_driver(&netback_driver);
  }