Tue, Apr 10, 2018 at 08:59:48PM CEST, sridhar.samudr...@intel.com wrote:
>This provides a generic interface for paravirtual drivers to listen
>for netdev register/unregister/link change events from pci ethernet
>devices with the same MAC and takeover their datapath. The notifier and
>event handling code is based on the existing netvsc implementation.
>
>It exposes 2 sets of interfaces to the paravirtual drivers.
>1. existing netvsc driver that uses 2 netdev model. In this model, no
>master netdev is created. The paravirtual driver registers each bypass
>instance along with a set of ops to manage the slave events.
>     bypass_master_register()
>     bypass_master_unregister()
>2. new virtio_net based solution that uses 3 netdev model. In this model,
>the bypass module provides interfaces to create/destroy additional master
>netdev and all the slave events are managed internally.
>      bypass_master_create()
>      bypass_master_destroy()
>
>Signed-off-by: Sridhar Samudrala <sridhar.samudr...@intel.com>
>---
> include/linux/netdevice.h |  14 +
> include/net/bypass.h      |  96 ++++++
> net/Kconfig               |  18 +
> net/core/Makefile         |   1 +
> net/core/bypass.c         | 844 ++++++++++++++++++++++++++++++++++++++++++++++
> 5 files changed, 973 insertions(+)
> create mode 100644 include/net/bypass.h
> create mode 100644 net/core/bypass.c
>
>diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>index cf44503ea81a..587293728f70 100644
>--- a/include/linux/netdevice.h
>+++ b/include/linux/netdevice.h
>@@ -1430,6 +1430,8 @@ enum netdev_priv_flags {
>       IFF_PHONY_HEADROOM              = 1<<24,
>       IFF_MACSEC                      = 1<<25,
>       IFF_NO_RX_HANDLER               = 1<<26,
>+      IFF_BYPASS                      = 1 << 27,
>+      IFF_BYPASS_SLAVE                = 1 << 28,

I wonder, why you don't follow the existing coding style... Also, please
add these to into the comment above.


> };
> 
> #define IFF_802_1Q_VLAN                       IFF_802_1Q_VLAN
>@@ -1458,6 +1460,8 @@ enum netdev_priv_flags {
> #define IFF_RXFH_CONFIGURED           IFF_RXFH_CONFIGURED
> #define IFF_MACSEC                    IFF_MACSEC
> #define IFF_NO_RX_HANDLER             IFF_NO_RX_HANDLER
>+#define IFF_BYPASS                    IFF_BYPASS
>+#define IFF_BYPASS_SLAVE              IFF_BYPASS_SLAVE
> 
> /**
>  *    struct net_device - The DEVICE structure.
>@@ -4308,6 +4312,16 @@ static inline bool netif_is_rxfh_configured(const 
>struct net_device *dev)
>       return dev->priv_flags & IFF_RXFH_CONFIGURED;
> }
> 
>+static inline bool netif_is_bypass_master(const struct net_device *dev)
>+{
>+      return dev->priv_flags & IFF_BYPASS;
>+}
>+
>+static inline bool netif_is_bypass_slave(const struct net_device *dev)
>+{
>+      return dev->priv_flags & IFF_BYPASS_SLAVE;
>+}
>+
> /* This device needs to keep skb dst for qdisc enqueue or ndo_start_xmit() */
> static inline void netif_keep_dst(struct net_device *dev)
> {
>diff --git a/include/net/bypass.h b/include/net/bypass.h
>new file mode 100644
>index 000000000000..86b02cb894cf
>--- /dev/null
>+++ b/include/net/bypass.h
>@@ -0,0 +1,96 @@
>+// SPDX-License-Identifier: GPL-2.0
>+/* Copyright (c) 2018, Intel Corporation. */
>+
>+#ifndef _NET_BYPASS_H
>+#define _NET_BYPASS_H
>+
>+#include <linux/netdevice.h>
>+
>+struct bypass_ops {
>+      int (*slave_pre_register)(struct net_device *slave_netdev,
>+                                struct net_device *bypass_netdev);
>+      int (*slave_join)(struct net_device *slave_netdev,
>+                        struct net_device *bypass_netdev);
>+      int (*slave_pre_unregister)(struct net_device *slave_netdev,
>+                                  struct net_device *bypass_netdev);
>+      int (*slave_release)(struct net_device *slave_netdev,
>+                           struct net_device *bypass_netdev);
>+      int (*slave_link_change)(struct net_device *slave_netdev,
>+                               struct net_device *bypass_netdev);
>+      rx_handler_result_t (*handle_frame)(struct sk_buff **pskb);
>+};
>+
>+struct bypass_master {
>+      struct list_head list;
>+      struct net_device __rcu *bypass_netdev;
>+      struct bypass_ops __rcu *ops;
>+};
>+
>+/* bypass state */
>+struct bypass_info {
>+      /* passthru netdev with same MAC */
>+      struct net_device __rcu *active_netdev;

You still use "active"/"backup" names which is highly misleading as
it has completely different meaning that in bond for example.
I noted that in my previous review already. Please change it.


>+
>+      /* virtio_net netdev */
>+      struct net_device __rcu *backup_netdev;
>+
>+      /* active netdev stats */
>+      struct rtnl_link_stats64 active_stats;
>+
>+      /* backup netdev stats */
>+      struct rtnl_link_stats64 backup_stats;
>+
>+      /* aggregated stats */
>+      struct rtnl_link_stats64 bypass_stats;
>+
>+      /* spinlock while updating stats */
>+      spinlock_t stats_lock;
>+};
>+
>+#if IS_ENABLED(CONFIG_NET_BYPASS)
>+
>+int bypass_master_create(struct net_device *backup_netdev,
>+                       struct bypass_master **pbypass_master);
>+void bypass_master_destroy(struct bypass_master *bypass_master);
>+
>+int bypass_master_register(struct net_device *dev, struct bypass_ops *ops,
>+                         struct bypass_master **pbypass_master);
>+void bypass_master_unregister(struct bypass_master *bypass_master);
>+
>+int bypass_slave_unregister(struct net_device *slave_netdev);
>+
>+#else
>+
>+static inline
>+int bypass_master_create(struct net_device *backup_netdev,
>+                       struct bypass_master **pbypass_master);
>+{
>+      return 0;
>+}
>+
>+static inline
>+void bypass_master_destroy(struct bypass_master *bypass_master)
>+{
>+}
>+
>+static inline
>+int bypass_master_register(struct net_device *dev, struct bypass_ops *ops,
>+                         struct pbypass_master **pbypass_master);
>+{
>+      return 0;
>+}
>+
>+static inline
>+void bypass_master_unregister(struct bypass_master *bypass_master)
>+{
>+}
>+
>+static inline
>+int bypass_slave_unregister(struct net_device *slave_netdev)
>+{
>+      return 0;
>+}
>+
>+#endif
>+
>+#endif /* _NET_BYPASS_H */
>diff --git a/net/Kconfig b/net/Kconfig
>index 0428f12c25c2..994445f4a96a 100644
>--- a/net/Kconfig
>+++ b/net/Kconfig
>@@ -423,6 +423,24 @@ config MAY_USE_DEVLINK
>         on MAY_USE_DEVLINK to ensure they do not cause link errors when
>         devlink is a loadable module and the driver using it is built-in.
> 
>+config NET_BYPASS
>+      tristate "Bypass interface"
>+      ---help---
>+        This provides a generic interface for paravirtual drivers to listen
>+        for netdev register/unregister/link change events from pci ethernet
>+        devices with the same MAC and takeover their datapath. This also
>+        enables live migration of a VM with direct attached VF by failing
>+        over to the paravirtual datapath when the VF is unplugged.
>+
>+config MAY_USE_BYPASS
>+      tristate
>+      default m if NET_BYPASS=m
>+      default y if NET_BYPASS=y || NET_BYPASS=n
>+      help
>+        Drivers using the bypass infrastructure should have a dependency
>+        on MAY_USE_BYPASS to ensure they do not cause link errors when
>+        bypass is a loadable module and the driver using it is built-in.
>+
> endif   # if NET
> 
> # Used by archs to tell that they support BPF JIT compiler plus which flavour.
>diff --git a/net/core/Makefile b/net/core/Makefile
>index 6dbbba8c57ae..a9727ed1c8fc 100644
>--- a/net/core/Makefile
>+++ b/net/core/Makefile
>@@ -30,3 +30,4 @@ obj-$(CONFIG_DST_CACHE) += dst_cache.o
> obj-$(CONFIG_HWBM) += hwbm.o
> obj-$(CONFIG_NET_DEVLINK) += devlink.o
> obj-$(CONFIG_GRO_CELLS) += gro_cells.o
>+obj-$(CONFIG_NET_BYPASS) += bypass.o
>diff --git a/net/core/bypass.c b/net/core/bypass.c
>new file mode 100644
>index 000000000000..b5b9cb554c3f
>--- /dev/null
>+++ b/net/core/bypass.c
>@@ -0,0 +1,844 @@
>+// SPDX-License-Identifier: GPL-2.0
>+/* Copyright (c) 2018, Intel Corporation. */
>+
>+/* A common module to handle registrations and notifications for paravirtual
>+ * drivers to enable accelerated datapath and support VF live migration.
>+ *
>+ * The notifier and event handling code is based on netvsc driver.
>+ */
>+
>+#include <linux/netdevice.h>
>+#include <linux/etherdevice.h>
>+#include <linux/ethtool.h>
>+#include <linux/module.h>
>+#include <linux/slab.h>
>+#include <linux/netdevice.h>
>+#include <linux/netpoll.h>
>+#include <linux/rtnetlink.h>
>+#include <linux/if_vlan.h>
>+#include <linux/pci.h>
>+#include <net/sch_generic.h>
>+#include <uapi/linux/if_arp.h>
>+#include <net/bypass.h>
>+
>+static LIST_HEAD(bypass_master_list);
>+static DEFINE_SPINLOCK(bypass_lock);
>+
>+static int bypass_slave_pre_register(struct net_device *slave_netdev,
>+                                   struct net_device *bypass_netdev,
>+                                   struct bypass_ops *bypass_ops)
>+{
>+      struct bypass_info *bi;
>+      bool backup;
>+
>+      if (bypass_ops) {
>+              if (!bypass_ops->slave_pre_register)
>+                      return -EINVAL;
>+
>+              return bypass_ops->slave_pre_register(slave_netdev,
>+                                                    bypass_netdev);
>+      }
>+
>+      bi = netdev_priv(bypass_netdev);
>+      backup = (slave_netdev->dev.parent == bypass_netdev->dev.parent);
>+      if (backup ? rtnl_dereference(bi->backup_netdev) :
>+                      rtnl_dereference(bi->active_netdev)) {
>+              netdev_err(bypass_netdev, "%s attempting to register as slave 
>dev when %s already present\n",
>+                         slave_netdev->name, backup ? "backup" : "active");
>+              return -EEXIST;
>+      }
>+
>+      /* Avoid non pci devices as active netdev */
>+      if (!backup && (!slave_netdev->dev.parent ||
>+                      !dev_is_pci(slave_netdev->dev.parent)))
>+              return -EINVAL;
>+
>+      return 0;
>+}
>+
>+static int bypass_slave_join(struct net_device *slave_netdev,
>+                           struct net_device *bypass_netdev,
>+                           struct bypass_ops *bypass_ops)
>+{
>+      struct bypass_info *bi;
>+      bool backup;
>+
>+      if (bypass_ops) {
>+              if (!bypass_ops->slave_join)
>+                      return -EINVAL;
>+
>+              return bypass_ops->slave_join(slave_netdev, bypass_netdev);
>+      }
>+
>+      bi = netdev_priv(bypass_netdev);
>+      backup = (slave_netdev->dev.parent == bypass_netdev->dev.parent);
>+
>+      dev_hold(slave_netdev);
>+
>+      if (backup) {
>+              rcu_assign_pointer(bi->backup_netdev, slave_netdev);
>+              dev_get_stats(bi->backup_netdev, &bi->backup_stats);
>+      } else {
>+              rcu_assign_pointer(bi->active_netdev, slave_netdev);
>+              dev_get_stats(bi->active_netdev, &bi->active_stats);
>+              bypass_netdev->min_mtu = slave_netdev->min_mtu;
>+              bypass_netdev->max_mtu = slave_netdev->max_mtu;
>+      }
>+
>+      netdev_info(bypass_netdev, "bypass slave:%s joined\n",
>+                  slave_netdev->name);
>+
>+      return 0;
>+}
>+
>+/* Called when slave dev is injecting data into network stack.
>+ * Change the associated network device from lower dev to virtio.
>+ * note: already called with rcu_read_lock
>+ */
>+static rx_handler_result_t bypass_handle_frame(struct sk_buff **pskb)
>+{
>+      struct sk_buff *skb = *pskb;
>+      struct net_device *ndev = rcu_dereference(skb->dev->rx_handler_data);
>+
>+      skb->dev = ndev;
>+
>+      return RX_HANDLER_ANOTHER;
>+}
>+
>+static struct net_device *bypass_master_get_bymac(u8 *mac,
>+                                                struct bypass_ops **ops)
>+{
>+      struct bypass_master *bypass_master;
>+      struct net_device *bypass_netdev;
>+
>+      spin_lock(&bypass_lock);
>+      list_for_each_entry(bypass_master, &bypass_master_list, list) {

As I wrote the last time, you don't need this list, spinlock.
You can do just something like:
        for_each_net(net) {
                for_each_netdev(net, dev) {
                        if (netif_is_bypass_master(dev)) {




>+              bypass_netdev = rcu_dereference(bypass_master->bypass_netdev);
>+              if (ether_addr_equal(bypass_netdev->perm_addr, mac)) {
>+                      *ops = rcu_dereference(bypass_master->ops);

I don't see how rcu_dereference is ok here.
1) I don't see rcu_read_lock taken
2) Looks like bypass_master->ops has the same value across the whole
   existence.


>+                      spin_unlock(&bypass_lock);
>+                      return bypass_netdev;
>+              }
>+      }
>+      spin_unlock(&bypass_lock);
>+      return NULL;
>+}
>+
>+static int bypass_slave_register(struct net_device *slave_netdev)
>+{
>+      struct net_device *bypass_netdev;
>+      struct bypass_ops *bypass_ops;
>+      int ret, orig_mtu;
>+
>+      ASSERT_RTNL();
>+
>+      bypass_netdev = bypass_master_get_bymac(slave_netdev->perm_addr,
>+                                              &bypass_ops);

For master, could you use word "master" in the variables so it is clear?
Also, "dev" is fine instead of "netdev".
Something like "bpmaster_dev"


>+      if (!bypass_netdev)
>+              goto done;
>+
>+      ret = bypass_slave_pre_register(slave_netdev, bypass_netdev,
>+                                      bypass_ops);
>+      if (ret != 0)

        Just "if (ret)" will do. You have this on more places.


>+              goto done;
>+
>+      ret = netdev_rx_handler_register(slave_netdev,
>+                                       bypass_ops ? bypass_ops->handle_frame :
>+                                       bypass_handle_frame, bypass_netdev);
>+      if (ret != 0) {
>+              netdev_err(slave_netdev, "can not register bypass rx handler 
>(err = %d)\n",
>+                         ret);
>+              goto done;
>+      }
>+
>+      ret = netdev_upper_dev_link(slave_netdev, bypass_netdev, NULL);
>+      if (ret != 0) {
>+              netdev_err(slave_netdev, "can not set master device %s (err = 
>%d)\n",
>+                         bypass_netdev->name, ret);
>+              goto upper_link_failed;
>+      }
>+
>+      slave_netdev->priv_flags |= IFF_BYPASS_SLAVE;
>+
>+      if (netif_running(bypass_netdev)) {
>+              ret = dev_open(slave_netdev);
>+              if (ret && (ret != -EBUSY)) {
>+                      netdev_err(bypass_netdev, "Opening slave %s failed 
>ret:%d\n",
>+                                 slave_netdev->name, ret);
>+                      goto err_interface_up;
>+              }
>+      }
>+
>+      /* Align MTU of slave with master */
>+      orig_mtu = slave_netdev->mtu;
>+      ret = dev_set_mtu(slave_netdev, bypass_netdev->mtu);
>+      if (ret != 0) {
>+              netdev_err(bypass_netdev, "unable to change mtu of %s to %u 
>register failed\n",
>+                         slave_netdev->name, bypass_netdev->mtu);
>+              goto err_set_mtu;
>+      }
>+
>+      ret = bypass_slave_join(slave_netdev, bypass_netdev, bypass_ops);
>+      if (ret != 0)
>+              goto err_join;
>+
>+      call_netdevice_notifiers(NETDEV_JOIN, slave_netdev);
>+
>+      netdev_info(bypass_netdev, "bypass slave:%s registered\n",
>+                  slave_netdev->name);
>+
>+      goto done;
>+
>+err_join:
>+      dev_set_mtu(slave_netdev, orig_mtu);
>+err_set_mtu:
>+      dev_close(slave_netdev);
>+err_interface_up:
>+      netdev_upper_dev_unlink(slave_netdev, bypass_netdev);
>+      slave_netdev->priv_flags &= ~IFF_BYPASS_SLAVE;
>+upper_link_failed:
>+      netdev_rx_handler_unregister(slave_netdev);
>+done:
>+      return NOTIFY_DONE;
>+}
>+
>+static int bypass_slave_pre_unregister(struct net_device *slave_netdev,
>+                                     struct net_device *bypass_netdev,
>+                                     struct bypass_ops *bypass_ops)
>+{
>+      struct net_device *backup_netdev, *active_netdev;
>+      struct bypass_info *bi;
>+
>+      if (bypass_ops) {
>+              if (!bypass_ops->slave_pre_unregister)
>+                      return -EINVAL;
>+
>+              return bypass_ops->slave_pre_unregister(slave_netdev,
>+                                                      bypass_netdev);
>+      }
>+
>+      bi = netdev_priv(bypass_netdev);
>+      active_netdev = rtnl_dereference(bi->active_netdev);
>+      backup_netdev = rtnl_dereference(bi->backup_netdev);
>+
>+      if (slave_netdev != active_netdev && slave_netdev != backup_netdev)
>+              return -EINVAL;
>+
>+      return 0;
>+}
>+
>+static int bypass_slave_release(struct net_device *slave_netdev,
>+                              struct net_device *bypass_netdev,
>+                              struct bypass_ops *bypass_ops)
>+{
>+      struct net_device *backup_netdev, *active_netdev;
>+      struct bypass_info *bi;
>+
>+      if (bypass_ops) {
>+              if (!bypass_ops->slave_release)
>+                      return -EINVAL;

I think it would be good to make the API to the driver more strict and
have a separate set of ops for "active" and "backup" netdevices.
That should stop people thinking about extending this to more slaves in
the future.



>+
>+              return bypass_ops->slave_release(slave_netdev, bypass_netdev);
>+      }
>+
>+      bi = netdev_priv(bypass_netdev);
>+      active_netdev = rtnl_dereference(bi->active_netdev);
>+      backup_netdev = rtnl_dereference(bi->backup_netdev);
>+
>+      if (slave_netdev == backup_netdev) {
>+              RCU_INIT_POINTER(bi->backup_netdev, NULL);
>+      } else {
>+              RCU_INIT_POINTER(bi->active_netdev, NULL);
>+              if (backup_netdev) {
>+                      bypass_netdev->min_mtu = backup_netdev->min_mtu;
>+                      bypass_netdev->max_mtu = backup_netdev->max_mtu;
>+              }
>+      }
>+
>+      dev_put(slave_netdev);
>+
>+      netdev_info(bypass_netdev, "bypass slave:%s released\n",
>+                  slave_netdev->name);
>+
>+      return 0;
>+}
>+
>+int bypass_slave_unregister(struct net_device *slave_netdev)
>+{
>+      struct net_device *bypass_netdev;
>+      struct bypass_ops *bypass_ops;
>+      int ret;
>+
>+      if (!netif_is_bypass_slave(slave_netdev))
>+              goto done;
>+
>+      ASSERT_RTNL();
>+
>+      bypass_netdev = bypass_master_get_bymac(slave_netdev->perm_addr,
>+                                              &bypass_ops);
>+      if (!bypass_netdev)
>+              goto done;
>+
>+      ret = bypass_slave_pre_unregister(slave_netdev, bypass_netdev,
>+                                        bypass_ops);
>+      if (ret != 0)
>+              goto done;
>+
>+      netdev_rx_handler_unregister(slave_netdev);
>+      netdev_upper_dev_unlink(slave_netdev, bypass_netdev);
>+      slave_netdev->priv_flags &= ~IFF_BYPASS_SLAVE;
>+
>+      bypass_slave_release(slave_netdev, bypass_netdev, bypass_ops);
>+
>+      netdev_info(bypass_netdev, "bypass slave:%s unregistered\n",
>+                  slave_netdev->name);
>+
>+done:
>+      return NOTIFY_DONE;
>+}
>+EXPORT_SYMBOL_GPL(bypass_slave_unregister);
>+
>+static bool bypass_xmit_ready(struct net_device *dev)
>+{
>+      return netif_running(dev) && netif_carrier_ok(dev);
>+}
>+
>+static int bypass_slave_link_change(struct net_device *slave_netdev)
>+{
>+      struct net_device *bypass_netdev, *active_netdev, *backup_netdev;
>+      struct bypass_ops *bypass_ops;
>+      struct bypass_info *bi;
>+
>+      if (!netif_is_bypass_slave(slave_netdev))
>+              goto done;
>+
>+      ASSERT_RTNL();
>+
>+      bypass_netdev = bypass_master_get_bymac(slave_netdev->perm_addr,
>+                                              &bypass_ops);
>+      if (!bypass_netdev)
>+              goto done;
>+
>+      if (bypass_ops) {
>+              if (!bypass_ops->slave_link_change)
>+                      goto done;
>+
>+              return bypass_ops->slave_link_change(slave_netdev,
>+                                                   bypass_netdev);
>+      }
>+
>+      if (!netif_running(bypass_netdev))
>+              return 0;
>+
>+      bi = netdev_priv(bypass_netdev);
>+
>+      active_netdev = rtnl_dereference(bi->active_netdev);
>+      backup_netdev = rtnl_dereference(bi->backup_netdev);
>+
>+      if (slave_netdev != active_netdev && slave_netdev != backup_netdev)
>+              goto done;

You don't need this check. "if (!netif_is_bypass_slave(slave_netdev))"
above is enough.


>+
>+      if ((active_netdev && bypass_xmit_ready(active_netdev)) ||
>+          (backup_netdev && bypass_xmit_ready(backup_netdev))) {
>+              netif_carrier_on(bypass_netdev);
>+              netif_tx_wake_all_queues(bypass_netdev);
>+      } else {
>+              netif_carrier_off(bypass_netdev);
>+              netif_tx_stop_all_queues(bypass_netdev);
>+      }
>+
>+done:
>+      return NOTIFY_DONE;
>+}
>+
>+static bool bypass_validate_event_dev(struct net_device *dev)
>+{
>+      /* Skip parent events */
>+      if (netif_is_bypass_master(dev))
>+              return false;
>+
>+      /* Avoid non-Ethernet type devices */
>+      if (dev->type != ARPHRD_ETHER)
>+              return false;
>+
>+      /* Avoid Vlan dev with same MAC registering as VF */
>+      if (is_vlan_dev(dev))
>+              return false;
>+
>+      /* Avoid Bonding master dev with same MAC registering as slave dev */
>+      if ((dev->priv_flags & IFF_BONDING) && (dev->flags & IFF_MASTER))

Yeah, this is certainly incorrect. One thing is, you should be using the
helpers netif_is_bond_master().
But what about the rest? macsec, macvlan, team, bridge, ovs and others?

You need to do it not by blacklisting, but with whitelisting. You need
to whitelist VF devices. My port flavours patchset might help with this.


>+              return false;
>+
>+      return true;
>+}
>+
>+static int
>+bypass_event(struct notifier_block *this, unsigned long event, void *ptr)
>+{
>+      struct net_device *event_dev = netdev_notifier_info_to_dev(ptr);
>+
>+      if (!bypass_validate_event_dev(event_dev))
>+              return NOTIFY_DONE;
>+
>+      switch (event) {
>+      case NETDEV_REGISTER:
>+              return bypass_slave_register(event_dev);
>+      case NETDEV_UNREGISTER:
>+              return bypass_slave_unregister(event_dev);
>+      case NETDEV_UP:
>+      case NETDEV_DOWN:
>+      case NETDEV_CHANGE:
>+              return bypass_slave_link_change(event_dev);
>+      default:
>+              return NOTIFY_DONE;
>+      }
>+}
>+
>+static struct notifier_block bypass_notifier = {
>+      .notifier_call = bypass_event,
>+};
>+
>+int bypass_open(struct net_device *dev)
>+{
>+      struct bypass_info *bi = netdev_priv(dev);
>+      struct net_device *active_netdev, *backup_netdev;
>+      int err;
>+
>+      netif_carrier_off(dev);
>+      netif_tx_wake_all_queues(dev);
>+
>+      active_netdev = rtnl_dereference(bi->active_netdev);
>+      if (active_netdev) {
>+              err = dev_open(active_netdev);
>+              if (err)
>+                      goto err_active_open;
>+      }
>+
>+      backup_netdev = rtnl_dereference(bi->backup_netdev);
>+      if (backup_netdev) {
>+              err = dev_open(backup_netdev);
>+              if (err)
>+                      goto err_backup_open;
>+      }
>+
>+      return 0;
>+
>+err_backup_open:
>+      dev_close(active_netdev);
>+err_active_open:
>+      netif_tx_disable(dev);
>+      return err;
>+}
>+EXPORT_SYMBOL_GPL(bypass_open);
>+
>+int bypass_close(struct net_device *dev)
>+{
>+      struct bypass_info *vi = netdev_priv(dev);

This should be probably "bi"


>+      struct net_device *slave_netdev;
>+
>+      netif_tx_disable(dev);
>+
>+      slave_netdev = rtnl_dereference(vi->active_netdev);
>+      if (slave_netdev)
>+              dev_close(slave_netdev);
>+
>+      slave_netdev = rtnl_dereference(vi->backup_netdev);
>+      if (slave_netdev)
>+              dev_close(slave_netdev);
>+
>+      return 0;
>+}
>+EXPORT_SYMBOL_GPL(bypass_close);
>+
>+static netdev_tx_t bypass_drop_xmit(struct sk_buff *skb, struct net_device 
>*dev)
>+{
>+      atomic_long_inc(&dev->tx_dropped);
>+      dev_kfree_skb_any(skb);
>+      return NETDEV_TX_OK;
>+}
>+
>+netdev_tx_t bypass_start_xmit(struct sk_buff *skb, struct net_device *dev)
>+{
>+      struct bypass_info *bi = netdev_priv(dev);

If you rename the other variable to "bpmaster_dev", it would be nice to
rename this to bpinfo or something more descriptive. "bi" is too short
to know what that is right away.


>+      struct net_device *xmit_dev;

Don't mix "dev" and "netdev" in one .c file. Just use "dev" for all.



>+
>+      /* Try xmit via active netdev followed by backup netdev */
>+      xmit_dev = rcu_dereference_bh(bi->active_netdev);
>+      if (!xmit_dev || !bypass_xmit_ready(xmit_dev)) {
>+              xmit_dev = rcu_dereference_bh(bi->backup_netdev);
>+              if (!xmit_dev || !bypass_xmit_ready(xmit_dev))
>+                      return bypass_drop_xmit(skb, dev);
>+      }
>+
>+      skb->dev = xmit_dev;
>+      skb->queue_mapping = qdisc_skb_cb(skb)->slave_dev_queue_mapping;
>+
>+      return dev_queue_xmit(skb);
>+}
>+EXPORT_SYMBOL_GPL(bypass_start_xmit);
>+
>+u16 bypass_select_queue(struct net_device *dev, struct sk_buff *skb,
>+                      void *accel_priv, select_queue_fallback_t fallback)
>+{
>+      /* This helper function exists to help dev_pick_tx get the correct
>+       * destination queue.  Using a helper function skips a call to
>+       * skb_tx_hash and will put the skbs in the queue we expect on their
>+       * way down to the bonding driver.
>+       */
>+      u16 txq = skb_rx_queue_recorded(skb) ? skb_get_rx_queue(skb) : 0;
>+
>+      /* Save the original txq to restore before passing to the driver */
>+      qdisc_skb_cb(skb)->slave_dev_queue_mapping = skb->queue_mapping;
>+
>+      if (unlikely(txq >= dev->real_num_tx_queues)) {
>+              do {
>+                      txq -= dev->real_num_tx_queues;
>+              } while (txq >= dev->real_num_tx_queues);
>+      }
>+
>+      return txq;
>+}
>+EXPORT_SYMBOL_GPL(bypass_select_queue);
>+
>+/* fold stats, assuming all rtnl_link_stats64 fields are u64, but
>+ * that some drivers can provide 32bit values only.
>+ */
>+static void bypass_fold_stats(struct rtnl_link_stats64 *_res,
>+                            const struct rtnl_link_stats64 *_new,
>+                            const struct rtnl_link_stats64 *_old)
>+{
>+      const u64 *new = (const u64 *)_new;
>+      const u64 *old = (const u64 *)_old;
>+      u64 *res = (u64 *)_res;
>+      int i;
>+
>+      for (i = 0; i < sizeof(*_res) / sizeof(u64); i++) {
>+              u64 nv = new[i];
>+              u64 ov = old[i];
>+              s64 delta = nv - ov;
>+
>+              /* detects if this particular field is 32bit only */
>+              if (((nv | ov) >> 32) == 0)
>+                      delta = (s64)(s32)((u32)nv - (u32)ov);
>+
>+              /* filter anomalies, some drivers reset their stats
>+               * at down/up events.
>+               */
>+              if (delta > 0)
>+                      res[i] += delta;
>+      }
>+}
>+
>+void bypass_get_stats(struct net_device *dev, struct rtnl_link_stats64 *stats)
>+{
>+      struct bypass_info *bi = netdev_priv(dev);

You can WARN_ON and return in case the dev is not bypass master, just
to catch buggy drivers. Same with other helpers.


>+      const struct rtnl_link_stats64 *new;
>+      struct rtnl_link_stats64 temp;
>+      struct net_device *slave_netdev;
>+
>+      spin_lock(&bi->stats_lock);
>+      memcpy(stats, &bi->bypass_stats, sizeof(*stats));
>+
>+      rcu_read_lock();
>+
>+      slave_netdev = rcu_dereference(bi->active_netdev);
>+      if (slave_netdev) {
>+              new = dev_get_stats(slave_netdev, &temp);
>+              bypass_fold_stats(stats, new, &bi->active_stats);
>+              memcpy(&bi->active_stats, new, sizeof(*new));
>+      }
>+
>+      slave_netdev = rcu_dereference(bi->backup_netdev);
>+      if (slave_netdev) {
>+              new = dev_get_stats(slave_netdev, &temp);
>+              bypass_fold_stats(stats, new, &bi->backup_stats);
>+              memcpy(&bi->backup_stats, new, sizeof(*new));
>+      }
>+
>+      rcu_read_unlock();
>+
>+      memcpy(&bi->bypass_stats, stats, sizeof(*stats));
>+      spin_unlock(&bi->stats_lock);
>+}
>+EXPORT_SYMBOL_GPL(bypass_get_stats);
>+
>+int bypass_change_mtu(struct net_device *dev, int new_mtu)
>+{
>+      struct bypass_info *bi = netdev_priv(dev);
>+      struct net_device *active_netdev, *backup_netdev;
>+      int ret = 0;

Pointless initialization.


>+
>+      active_netdev = rcu_dereference(bi->active_netdev);
>+      if (active_netdev) {
>+              ret = dev_set_mtu(active_netdev, new_mtu);
>+              if (ret)
>+                      return ret;
>+      }
>+
>+      backup_netdev = rcu_dereference(bi->backup_netdev);
>+      if (backup_netdev) {
>+              ret = dev_set_mtu(backup_netdev, new_mtu);
>+              if (ret) {
>+                      dev_set_mtu(active_netdev, dev->mtu);
>+                      return ret;
>+              }
>+      }
>+
>+      dev->mtu = new_mtu;
>+      return 0;
>+}
>+EXPORT_SYMBOL_GPL(bypass_change_mtu);
>+
>+void bypass_set_rx_mode(struct net_device *dev)
>+{
>+      struct bypass_info *bi = netdev_priv(dev);
>+      struct net_device *slave_netdev;
>+
>+      rcu_read_lock();
>+
>+      slave_netdev = rcu_dereference(bi->active_netdev);
>+      if (slave_netdev) {
>+              dev_uc_sync_multiple(slave_netdev, dev);
>+              dev_mc_sync_multiple(slave_netdev, dev);
>+      }
>+
>+      slave_netdev = rcu_dereference(bi->backup_netdev);
>+      if (slave_netdev) {
>+              dev_uc_sync_multiple(slave_netdev, dev);
>+              dev_mc_sync_multiple(slave_netdev, dev);
>+      }
>+
>+      rcu_read_unlock();
>+}
>+EXPORT_SYMBOL_GPL(bypass_set_rx_mode);
>+
>+static const struct net_device_ops bypass_netdev_ops = {
>+      .ndo_open               = bypass_open,
>+      .ndo_stop               = bypass_close,
>+      .ndo_start_xmit         = bypass_start_xmit,
>+      .ndo_select_queue       = bypass_select_queue,
>+      .ndo_get_stats64        = bypass_get_stats,
>+      .ndo_change_mtu         = bypass_change_mtu,
>+      .ndo_set_rx_mode        = bypass_set_rx_mode,
>+      .ndo_validate_addr      = eth_validate_addr,
>+      .ndo_features_check     = passthru_features_check,
>+};
>+
>+#define BYPASS_DRV_NAME "bypass"
>+#define BYPASS_DRV_VERSION "0.1"
>+
>+static void bypass_ethtool_get_drvinfo(struct net_device *dev,
>+                                     struct ethtool_drvinfo *drvinfo)
>+{
>+      strlcpy(drvinfo->driver, BYPASS_DRV_NAME, sizeof(drvinfo->driver));
>+      strlcpy(drvinfo->version, BYPASS_DRV_VERSION, sizeof(drvinfo->version));
>+}
>+
>+int bypass_ethtool_get_link_ksettings(struct net_device *dev,
>+                                    struct ethtool_link_ksettings *cmd)
>+{
>+      struct bypass_info *bi = netdev_priv(dev);
>+      struct net_device *slave_netdev;
>+
>+      slave_netdev = rtnl_dereference(bi->active_netdev);
>+      if (!slave_netdev || !bypass_xmit_ready(slave_netdev)) {
>+              slave_netdev = rtnl_dereference(bi->backup_netdev);
>+              if (!slave_netdev || !bypass_xmit_ready(slave_netdev)) {
>+                      cmd->base.duplex = DUPLEX_UNKNOWN;
>+                      cmd->base.port = PORT_OTHER;
>+                      cmd->base.speed = SPEED_UNKNOWN;
>+
>+                      return 0;
>+              }
>+      }
>+
>+      return __ethtool_get_link_ksettings(slave_netdev, cmd);
>+}
>+EXPORT_SYMBOL_GPL(bypass_ethtool_get_link_ksettings);
>+
>+static const struct ethtool_ops bypass_ethtool_ops = {
>+      .get_drvinfo            = bypass_ethtool_get_drvinfo,
>+      .get_link               = ethtool_op_get_link,
>+      .get_link_ksettings     = bypass_ethtool_get_link_ksettings,
>+};
>+
>+static void bypass_register_existing_slave(struct net_device *bypass_netdev)
>+{
>+      struct net *net = dev_net(bypass_netdev);
>+      struct net_device *dev;
>+
>+      rtnl_lock();
>+      for_each_netdev(net, dev) {
>+              if (dev == bypass_netdev)
>+                      continue;
>+              if (!bypass_validate_event_dev(dev))
>+                      continue;
>+              if (ether_addr_equal(bypass_netdev->perm_addr, dev->perm_addr))
>+                      bypass_slave_register(dev);
>+      }
>+      rtnl_unlock();
>+}
>+
>+int bypass_master_register(struct net_device *dev, struct bypass_ops *ops,
>+                         struct bypass_master **pbypass_master)
>+{
>+      struct bypass_master *bypass_master;
>+
>+      bypass_master = kzalloc(sizeof(*bypass_master), GFP_KERNEL);
>+      if (!bypass_master)
>+              return -ENOMEM;
>+
>+      rcu_assign_pointer(bypass_master->ops, ops);
>+      dev_hold(dev);
>+      dev->priv_flags |= IFF_BYPASS;
>+      rcu_assign_pointer(bypass_master->bypass_netdev, dev);
>+
>+      spin_lock(&bypass_lock);
>+      list_add_tail(&bypass_master->list, &bypass_master_list);
>+      spin_unlock(&bypass_lock);
>+
>+      bypass_register_existing_slave(dev);
>+
>+      *pbypass_master = bypass_master;
>+      return 0;
>+}
>+EXPORT_SYMBOL_GPL(bypass_master_register);
>+
>+void bypass_master_unregister(struct bypass_master *bypass_master)
>+{
>+      struct net_device *bypass_netdev;
>+
>+      bypass_netdev = rcu_dereference(bypass_master->bypass_netdev);
>+
>+      bypass_netdev->priv_flags &= ~IFF_BYPASS;
>+      dev_put(bypass_netdev);
>+
>+      spin_lock(&bypass_lock);
>+      list_del(&bypass_master->list);
>+      spin_unlock(&bypass_lock);
>+
>+      kfree(bypass_master);
>+}
>+EXPORT_SYMBOL_GPL(bypass_master_unregister);
>+
>+int bypass_master_create(struct net_device *backup_netdev,
>+                       struct bypass_master **pbypass_master)
>+{
>+      struct device *dev = backup_netdev->dev.parent;
>+      struct net_device *bypass_netdev;
>+      int err;
>+
>+      /* Alloc at least 2 queues, for now we are going with 16 assuming
>+       * that most devices being bonded won't have too many queues.
>+       */
>+      bypass_netdev = alloc_etherdev_mq(sizeof(struct bypass_info), 16);
>+      if (!bypass_netdev) {
>+              dev_err(dev, "Unable to allocate bypass_netdev!\n");
>+              return -ENOMEM;
>+      }
>+
>+      dev_net_set(bypass_netdev, dev_net(backup_netdev));
>+      SET_NETDEV_DEV(bypass_netdev, dev);
>+
>+      bypass_netdev->netdev_ops = &bypass_netdev_ops;
>+      bypass_netdev->ethtool_ops = &bypass_ethtool_ops;
>+
>+      /* Initialize the device options */
>+      bypass_netdev->priv_flags |= IFF_UNICAST_FLT | IFF_NO_QUEUE;
>+      bypass_netdev->priv_flags &= ~(IFF_XMIT_DST_RELEASE |
>+                                     IFF_TX_SKB_SHARING);
>+
>+      /* don't acquire bypass netdev's netif_tx_lock when transmitting */
>+      bypass_netdev->features |= NETIF_F_LLTX;
>+
>+      /* Don't allow bypass devices to change network namespaces. */
>+      bypass_netdev->features |= NETIF_F_NETNS_LOCAL;
>+
>+      bypass_netdev->hw_features = NETIF_F_HW_CSUM | NETIF_F_SG |
>+                                   NETIF_F_FRAGLIST | NETIF_F_ALL_TSO |
>+                                   NETIF_F_HIGHDMA | NETIF_F_LRO;
>+
>+      bypass_netdev->hw_features |= NETIF_F_GSO_ENCAP_ALL;
>+      bypass_netdev->features |= bypass_netdev->hw_features;
>+
>+      memcpy(bypass_netdev->dev_addr, backup_netdev->dev_addr,
>+             bypass_netdev->addr_len);
>+
>+      bypass_netdev->min_mtu = backup_netdev->min_mtu;
>+      bypass_netdev->max_mtu = backup_netdev->max_mtu;
>+
>+      err = register_netdev(bypass_netdev);
>+      if (err < 0) {
>+              dev_err(dev, "Unable to register bypass_netdev!\n");
>+              goto err_register_netdev;
>+      }
>+
>+      netif_carrier_off(bypass_netdev);
>+
>+      err = bypass_master_register(bypass_netdev, NULL, pbypass_master);
>+      if (err < 0)

just "if (err)" would do.


>+              goto err_bypass;
>+
>+      return 0;
>+
>+err_bypass:
>+      unregister_netdev(bypass_netdev);
>+err_register_netdev:
>+      free_netdev(bypass_netdev);
>+
>+      return err;
>+}
>+EXPORT_SYMBOL_GPL(bypass_master_create);
>+
>+void bypass_master_destroy(struct bypass_master *bypass_master)
>+{
>+      struct net_device *bypass_netdev;
>+      struct net_device *slave_netdev;
>+      struct bypass_info *bi;
>+
>+      if (!bypass_master)
>+              return;
>+
>+      bypass_netdev = rcu_dereference(bypass_master->bypass_netdev);
>+      bi = netdev_priv(bypass_netdev);
>+
>+      netif_device_detach(bypass_netdev);
>+
>+      rtnl_lock();
>+
>+      slave_netdev = rtnl_dereference(bi->active_netdev);
>+      if (slave_netdev)
>+              bypass_slave_unregister(slave_netdev);
>+
>+      slave_netdev = rtnl_dereference(bi->backup_netdev);
>+      if (slave_netdev)
>+              bypass_slave_unregister(slave_netdev);
>+
>+      bypass_master_unregister(bypass_master);
>+
>+      unregister_netdevice(bypass_netdev);
>+
>+      rtnl_unlock();
>+
>+      free_netdev(bypass_netdev);
>+}
>+EXPORT_SYMBOL_GPL(bypass_master_destroy);
>+
>+static __init int
>+bypass_init(void)
>+{
>+      register_netdevice_notifier(&bypass_notifier);
>+
>+      return 0;
>+}
>+module_init(bypass_init);
>+
>+static __exit
>+void bypass_exit(void)
>+{
>+      unregister_netdevice_notifier(&bypass_notifier);
>+}
>+module_exit(bypass_exit);
>+
>+MODULE_DESCRIPTION("Bypass infrastructure/interface for Paravirtual drivers");
>+MODULE_LICENSE("GPL v2");
>-- 
>2.14.3
>
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