On Fri, Mar 19, 2021 at 01:18, Vladimir Oltean <olteanv@xxxxxxxxx> wrote:
> From: Vladimir Oltean <vladimir.oltean@xxxxxxx>
>
> On reception of an skb, the bridge checks if it was marked as 'already
> forwarded in hardware' (checks if skb->offload_fwd_mark == 1), and if it
> is, it puts a mark of its own on that skb, with the switchdev mark of
> the ingress port. Then during forwarding, it enforces that the egress
> port must have a different switchdev mark than the ingress one (this is
> done in nbp_switchdev_allowed_egress).
>
> Non-switchdev drivers don't report any physical switch id (neither
> through devlink nor .ndo_get_port_parent_id), therefore the bridge
> assigns them a switchdev mark of 0, and packets coming from them will
> always have skb->offload_fwd_mark = 0. So there aren't any restrictions.
>
> Problems appear due to the fact that DSA would like to perform software
> fallback for bonding and team interfaces that the physical switch cannot
> offload.
>
> +-- br0 -+
> / / | \
> / / | \
> / / | \
> / / | \
> / / | \
> / | | bond0
> / | | / \
> swp0 swp1 swp2 swp3 swp4
>
> There, it is desirable that the presence of swp3 and swp4 under a
> non-offloaded LAG does not preclude us from doing hardware bridging
> beteen swp0, swp1 and swp2. The bandwidth of the CPU is often times high
> enough that software bridging between {swp0,swp1,swp2} and bond0 is not
> impractical.
>
> But this creates an impossible paradox given the current way in which
> port switchdev marks are assigned. When the driver receives a packet
> from swp0 (say, due to flooding), it must set skb->offload_fwd_mark to
> something.
>
> - If we set it to 0, then the bridge will forward it towards swp1, swp2
> and bond0. But the switch has already forwarded it towards swp1 and
> swp2 (not to bond0, remember, that isn't offloaded, so as far as the
> switch is concerned, ports swp3 and swp4 are not looking up the FDB,
> and the entire bond0 is a destination that is strictly behind the
> CPU). But we don't want duplicated traffic towards swp1 and swp2, so
> it's not ok to set skb->offload_fwd_mark = 0.
>
> - If we set it to 1, then the bridge will not forward the skb towards
> the ports with the same switchdev mark, i.e. not to swp1, swp2 and
> bond0. Towards swp1 and swp2 that's ok, but towards bond0? It should
> have forwarded the skb there.
>
> So the real issue is that bond0 will be assigned the same switchdev mark
> as {swp0,swp1,swp2}, because the function that assigns switchdev marks
> to bridge ports, nbp_switchdev_mark_set, recurses through bond0's lower
> interfaces until it finds something that implements devlink.
>
> A solution is to give the bridge explicit hints as to what switchdev
> mark it should use for each port.
>
> Currently, the bridging offload is very 'silent': a driver registers a
> netdevice notifier, which is put on the netns's notifier chain, and
> which sniffs around for NETDEV_CHANGEUPPER events where the upper is a
> bridge, and the lower is an interface it knows about (one registered by
> this driver, normally). Then, from within that notifier, it does a bunch
> of stuff behind the bridge's back, without the bridge necessarily
> knowing that there's somebody offloading that port. It looks like this:
>
> ip link set swp0 master br0
> |
> v
> bridge calls netdev_master_upper_dev_link
> |
> v
> call_netdevice_notifiers
> |
> v
> dsa_slave_netdevice_event
> |
> v
> oh, hey! it's for me!
> |
> v
> .port_bridge_join
>
> What we do to solve the conundrum is to be less silent, and emit a
> notification back. Something like this:
>
> ip link set swp0 master br0
> |
> v
> bridge calls netdev_master_upper_dev_link
> |
> v bridge: Aye! I'll use this
> call_netdevice_notifiers ^ ppid as the
> | | switchdev mark for
> v | this port, and zero
> dsa_slave_netdevice_event | if I got nothing.
> | |
> v |
> oh, hey! it's for me! |
> | |
> v |
> .port_bridge_join |
> | |
> +------------------------+
> switchdev_bridge_port_offload(swp0)
>
> Then stacked interfaces (like bond0 on top of swp3/swp4) would be
> treated differently in DSA, depending on whether we can or cannot
> offload them.
>
> The offload case:
>
> ip link set bond0 master br0
> |
> v
> bridge calls netdev_master_upper_dev_link
> |
> v bridge: Aye! I'll use this
> call_netdevice_notifiers ^ ppid as the
> | | switchdev mark for
> v | bond0.
> dsa_slave_netdevice_event | Coincidentally (or not),
> | | bond0 and swp0, swp1, swp2
> v | all have the same switchdev
> hmm, it's not quite for me, | mark now, since the ASIC
> but my driver has already | is able to forward towards
> called .port_lag_join | all these ports in hw.
> for it, because I have |
> a port with dp->lag_dev == bond0. |
> | |
> v |
> .port_bridge_join |
> for swp3 and swp4 |
> | |
> +------------------------+
> switchdev_bridge_port_offload(bond0)
>
> And the non-offload case:
>
> ip link set bond0 master br0
> |
> v
> bridge calls netdev_master_upper_dev_link
> |
> v bridge waiting:
> call_netdevice_notifiers ^ huh, switchdev_bridge_port_offload
> | | wasn't called, okay, I'll use a
> v | switchdev mark of zero for this one.
> dsa_slave_netdevice_event : Then packets received on swp0 will
> | : not be forwarded towards swp1, but
> v : they will towards bond0.
> it's not for me, but
> bond0 is an upper of swp3
> and swp4, but their dp->lag_dev
> is NULL because they couldn't
> offload it.
>
> Basically we can draw the conclusion that the lowers of a bridge port
> can come and go, so depending on the configuration of lowers for a
> bridge port, it can dynamically toggle between offloaded and unoffloaded.
> Therefore, we need an equivalent switchdev_bridge_port_unoffload too.
>
> This patch changes the way any switchdev driver interacts with the
> bridge. From now on, everybody needs to call switchdev_bridge_port_offload,
> otherwise the bridge will treat the port as non-offloaded and allow
> software flooding to other ports from the same ASIC.
>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>
> ---
> .../ethernet/freescale/dpaa2/dpaa2-switch.c | 4 +-
> .../marvell/prestera/prestera_switchdev.c | 7 ++
> .../mellanox/mlxsw/spectrum_switchdev.c | 4 +-
> drivers/net/ethernet/mscc/ocelot_net.c | 4 +-
> drivers/net/ethernet/rocker/rocker_ofdpa.c | 8 +-
> drivers/net/ethernet/ti/am65-cpsw-nuss.c | 7 +-
> drivers/net/ethernet/ti/cpsw_new.c | 6 +-
Why is not net/dsa included in this change?
> include/linux/if_bridge.h | 16 ++++
> net/bridge/br_if.c | 11 +--
> net/bridge/br_private.h | 8 +-
> net/bridge/br_switchdev.c | 94 ++++++++++++++++---
> 11 files changed, 138 insertions(+), 31 deletions(-)
>
> diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-switch.c b/drivers/net/ethernet/freescale/dpaa2/dpaa2-switch.c
> index 2fd05dd18d46..f20556178e33 100644
> --- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-switch.c
> +++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-switch.c
> @@ -1518,7 +1518,7 @@ static int dpaa2_switch_port_bridge_join(struct net_device *netdev,
> if (err)
> goto err_egress_flood;
>
> - return 0;
> + return switchdev_bridge_port_offload(netdev, NULL);
>
> err_egress_flood:
> dpaa2_switch_port_set_fdb(port_priv, NULL);
> @@ -1552,6 +1552,8 @@ static int dpaa2_switch_port_bridge_leave(struct net_device *netdev)
> struct ethsw_core *ethsw = port_priv->ethsw_data;
> int err;
>
> + switchdev_bridge_port_unoffload(netdev);
> +
> /* First of all, fast age any learn FDB addresses on this switch port */
> dpaa2_switch_port_fast_age(port_priv);
>
> diff --git a/drivers/net/ethernet/marvell/prestera/prestera_switchdev.c b/drivers/net/ethernet/marvell/prestera/prestera_switchdev.c
> index 49e052273f30..0b0d5db7b85b 100644
> --- a/drivers/net/ethernet/marvell/prestera/prestera_switchdev.c
> +++ b/drivers/net/ethernet/marvell/prestera/prestera_switchdev.c
> @@ -443,6 +443,10 @@ static int prestera_port_bridge_join(struct prestera_port *port,
> goto err_brport_create;
> }
>
> + err = switchdev_bridge_port_offload(port->dev, NULL);
> + if (err)
> + goto err_brport_offload;
> +
> if (bridge->vlan_enabled)
> return 0;
>
> @@ -453,6 +457,7 @@ static int prestera_port_bridge_join(struct prestera_port *port,
> return 0;
>
> err_port_join:
> +err_brport_offload:
> prestera_bridge_port_put(br_port);
> err_brport_create:
> prestera_bridge_put(bridge);
> @@ -520,6 +525,8 @@ static void prestera_port_bridge_leave(struct prestera_port *port,
> if (!br_port)
> return;
>
> + switchdev_bridge_port_unoffload(port->dev);
> +
> bridge = br_port->bridge;
>
> if (bridge->vlan_enabled)
> diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_switchdev.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_switchdev.c
> index 23b7e8d6386b..7fa0b3653819 100644
> --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_switchdev.c
> +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_switchdev.c
> @@ -2326,7 +2326,7 @@ int mlxsw_sp_port_bridge_join(struct mlxsw_sp_port *mlxsw_sp_port,
> if (err)
> goto err_port_join;
>
> - return 0;
> + return switchdev_bridge_port_offload(brport_dev, extack);
>
> err_port_join:
> mlxsw_sp_bridge_port_put(mlxsw_sp->bridge, bridge_port);
> @@ -2348,6 +2348,8 @@ void mlxsw_sp_port_bridge_leave(struct mlxsw_sp_port *mlxsw_sp_port,
> if (!bridge_port)
> return;
>
> + switchdev_bridge_port_unoffload(brport_dev);
> +
> bridge_device->ops->port_leave(bridge_device, bridge_port,
> mlxsw_sp_port);
> mlxsw_sp_bridge_port_put(mlxsw_sp->bridge, bridge_port);
> diff --git a/drivers/net/ethernet/mscc/ocelot_net.c b/drivers/net/ethernet/mscc/ocelot_net.c
> index d38ffc7cf5f0..b917d9dd8a6a 100644
> --- a/drivers/net/ethernet/mscc/ocelot_net.c
> +++ b/drivers/net/ethernet/mscc/ocelot_net.c
> @@ -1213,7 +1213,7 @@ static int ocelot_netdevice_bridge_join(struct net_device *dev,
> if (err)
> goto err_switchdev_sync;
>
> - return 0;
> + return switchdev_bridge_port_offload(brport_dev, extack);
>
> err_switchdev_sync:
> ocelot_port_bridge_leave(ocelot, port, bridge);
> @@ -1234,6 +1234,8 @@ static int ocelot_netdevice_bridge_leave(struct net_device *dev,
> if (err)
> return err;
>
> + switchdev_bridge_port_unoffload(brport_dev);
> +
> ocelot_port_bridge_leave(ocelot, port, bridge);
>
> return 0;
> diff --git a/drivers/net/ethernet/rocker/rocker_ofdpa.c b/drivers/net/ethernet/rocker/rocker_ofdpa.c
> index 967a634ee9ac..9b6d7cac112b 100644
> --- a/drivers/net/ethernet/rocker/rocker_ofdpa.c
> +++ b/drivers/net/ethernet/rocker/rocker_ofdpa.c
> @@ -2592,13 +2592,19 @@ static int ofdpa_port_bridge_join(struct ofdpa_port *ofdpa_port,
>
> ofdpa_port->bridge_dev = bridge;
>
> - return ofdpa_port_vlan_add(ofdpa_port, OFDPA_UNTAGGED_VID, 0);
> + err = ofdpa_port_vlan_add(ofdpa_port, OFDPA_UNTAGGED_VID, 0);
> + if (err)
> + return err;
> +
> + return switchdev_bridge_port_offload(ofdpa_port->dev, NULL);
> }
>
> static int ofdpa_port_bridge_leave(struct ofdpa_port *ofdpa_port)
> {
> int err;
>
> + switchdev_bridge_port_unoffload(ofdpa_port->dev);
> +
> err = ofdpa_port_vlan_del(ofdpa_port, OFDPA_UNTAGGED_VID, 0);
> if (err)
> return err;
> diff --git a/drivers/net/ethernet/ti/am65-cpsw-nuss.c b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> index 638d7b03be4b..fe2e38971acc 100644
> --- a/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> +++ b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> @@ -7,6 +7,7 @@
>
> #include <linux/clk.h>
> #include <linux/etherdevice.h>
> +#include <linux/if_bridge.h>
> #include <linux/if_vlan.h>
> #include <linux/interrupt.h>
> #include <linux/kernel.h>
> @@ -2082,6 +2083,7 @@ static int am65_cpsw_netdevice_port_link(struct net_device *ndev, struct net_dev
> {
> struct am65_cpsw_common *common = am65_ndev_to_common(ndev);
> struct am65_cpsw_ndev_priv *priv = am65_ndev_to_priv(ndev);
> + int err;
>
> if (!common->br_members) {
> common->hw_bridge_dev = br_ndev;
> @@ -2097,7 +2099,8 @@ static int am65_cpsw_netdevice_port_link(struct net_device *ndev, struct net_dev
>
> am65_cpsw_port_offload_fwd_mark_update(common);
>
> - return NOTIFY_DONE;
> + err = switchdev_bridge_port_offload(ndev, NULL);
> + return notifier_to_errno(err);
> }
>
> static void am65_cpsw_netdevice_port_unlink(struct net_device *ndev)
> @@ -2105,6 +2108,8 @@ static void am65_cpsw_netdevice_port_unlink(struct net_device *ndev)
> struct am65_cpsw_common *common = am65_ndev_to_common(ndev);
> struct am65_cpsw_ndev_priv *priv = am65_ndev_to_priv(ndev);
>
> + switchdev_bridge_port_unoffload(ndev);
> +
> common->br_members &= ~BIT(priv->port->port_id);
>
> am65_cpsw_port_offload_fwd_mark_update(common);
> diff --git a/drivers/net/ethernet/ti/cpsw_new.c b/drivers/net/ethernet/ti/cpsw_new.c
> index 58a64313ac00..6347532fb39d 100644
> --- a/drivers/net/ethernet/ti/cpsw_new.c
> +++ b/drivers/net/ethernet/ti/cpsw_new.c
> @@ -1508,6 +1508,7 @@ static int cpsw_netdevice_port_link(struct net_device *ndev,
> {
> struct cpsw_priv *priv = netdev_priv(ndev);
> struct cpsw_common *cpsw = priv->cpsw;
> + int err;
>
> if (!cpsw->br_members) {
> cpsw->hw_bridge_dev = br_ndev;
> @@ -1523,7 +1524,8 @@ static int cpsw_netdevice_port_link(struct net_device *ndev,
>
> cpsw_port_offload_fwd_mark_update(cpsw);
>
> - return NOTIFY_DONE;
> + err = switchdev_bridge_port_offload(ndev, NULL);
> + return notifier_to_errno(err);
> }
>
> static void cpsw_netdevice_port_unlink(struct net_device *ndev)
> @@ -1531,6 +1533,8 @@ static void cpsw_netdevice_port_unlink(struct net_device *ndev)
> struct cpsw_priv *priv = netdev_priv(ndev);
> struct cpsw_common *cpsw = priv->cpsw;
>
> + switchdev_bridge_port_unoffload(ndev);
> +
> cpsw->br_members &= ~BIT(priv->emac_port);
>
> cpsw_port_offload_fwd_mark_update(cpsw);
> diff --git a/include/linux/if_bridge.h b/include/linux/if_bridge.h
> index ea176c508c0d..4fbee6d5fc16 100644
> --- a/include/linux/if_bridge.h
> +++ b/include/linux/if_bridge.h
> @@ -196,4 +196,20 @@ static inline int br_fdb_replay(struct net_device *br_dev,
> }
> #endif
>
> +#if IS_ENABLED(CONFIG_BRIDGE) && IS_ENABLED(CONFIG_NET_SWITCHDEV)
> +int switchdev_bridge_port_offload(struct net_device *dev,
> + struct netlink_ext_ack *extack);
> +int switchdev_bridge_port_unoffload(struct net_device *dev);
> +#else
> +int switchdev_bridge_port_offload(struct net_device *dev,
> + struct netlink_ext_ack *extack)
> +{
> + return 0;
> +}
> +
> +int switchdev_bridge_port_unoffload(struct net_device *dev)
> +{
> +}
> +#endif
> +
> #endif
> diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
> index f7d2f472ae24..930a09f27e0d 100644
> --- a/net/bridge/br_if.c
> +++ b/net/bridge/br_if.c
> @@ -643,10 +643,6 @@ int br_add_if(struct net_bridge *br, struct net_device *dev,
> if (err)
> goto err5;
>
> - err = nbp_switchdev_mark_set(p);
> - if (err)
> - goto err6;
> -
> dev_disable_lro(dev);
>
> list_add_rcu(&p->list, &br->port_list);
> @@ -671,13 +667,13 @@ int br_add_if(struct net_bridge *br, struct net_device *dev,
> */
> err = dev_pre_changeaddr_notify(br->dev, dev->dev_addr, extack);
> if (err)
> - goto err7;
> + goto err6;
> }
>
> err = nbp_vlan_init(p, extack);
> if (err) {
> netdev_err(dev, "failed to initialize vlan filtering on this port\n");
> - goto err7;
> + goto err6;
> }
>
> spin_lock_bh(&br->lock);
> @@ -700,11 +696,10 @@ int br_add_if(struct net_bridge *br, struct net_device *dev,
>
> return 0;
>
> -err7:
> +err6:
> list_del_rcu(&p->list);
> br_fdb_delete_by_port(br, p, 0, 1);
> nbp_update_port_count(br);
> -err6:
> netdev_upper_dev_unlink(dev, br->dev);
> err5:
> dev->priv_flags &= ~IFF_BRIDGE_PORT;
> diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
> index d7d167e10b70..1982b5887d0f 100644
> --- a/net/bridge/br_private.h
> +++ b/net/bridge/br_private.h
> @@ -326,8 +326,10 @@ struct net_bridge_port {
> #ifdef CONFIG_NET_POLL_CONTROLLER
> struct netpoll *np;
> #endif
> + int offload_count;
Should this be conditional on CONFIG_NET_SWITCHDEV?
> #ifdef CONFIG_NET_SWITCHDEV
> int offload_fwd_mark;
> + struct netdev_phys_item_id ppid;
> #endif
> u16 group_fwd_mask;
> u16 backup_redirected_cnt;
> @@ -1572,7 +1574,6 @@ static inline void br_sysfs_delbr(struct net_device *dev) { return; }
>
> /* br_switchdev.c */
> #ifdef CONFIG_NET_SWITCHDEV
> -int nbp_switchdev_mark_set(struct net_bridge_port *p);
> void nbp_switchdev_frame_mark(const struct net_bridge_port *p,
> struct sk_buff *skb);
> bool nbp_switchdev_allowed_egress(const struct net_bridge_port *p,
> @@ -1592,11 +1593,6 @@ static inline void br_switchdev_frame_unmark(struct sk_buff *skb)
> skb->offload_fwd_mark = 0;
> }
> #else
> -static inline int nbp_switchdev_mark_set(struct net_bridge_port *p)
> -{
> - return 0;
> -}
> -
> static inline void nbp_switchdev_frame_mark(const struct net_bridge_port *p,
> struct sk_buff *skb)
> {
> diff --git a/net/bridge/br_switchdev.c b/net/bridge/br_switchdev.c
> index b89503832fcc..4cf7902f056c 100644
> --- a/net/bridge/br_switchdev.c
> +++ b/net/bridge/br_switchdev.c
> @@ -8,37 +8,109 @@
>
> #include "br_private.h"
>
> -static int br_switchdev_mark_get(struct net_bridge *br, struct net_device *dev)
> +static int br_switchdev_mark_get(struct net_bridge *br,
> + struct net_bridge_port *new_nbp)
> {
> struct net_bridge_port *p;
>
> /* dev is yet to be added to the port list. */
> list_for_each_entry(p, &br->port_list, list) {
> - if (netdev_port_same_parent_id(dev, p->dev))
> + if (!p->offload_count)
> + continue;
> +
> + if (netdev_phys_item_id_same(&p->ppid, &new_nbp->ppid))
> return p->offload_fwd_mark;
> }
>
> return ++br->offload_fwd_mark;
> }
>
> -int nbp_switchdev_mark_set(struct net_bridge_port *p)
> +static int nbp_switchdev_mark_set(struct net_bridge_port *p,
> + struct netdev_phys_item_id ppid,
> + struct netlink_ext_ack *extack)
> +{
> + if (p->offload_count) {
> + /* Prevent unsupported configurations such as a bridge port
> + * which is a bonding interface, and the member ports are from
> + * different hardware switches.
> + */
> + if (!netdev_phys_item_id_same(&p->ppid, &ppid)) {
> + NL_SET_ERR_MSG_MOD(extack,
> + "Same bridge port cannot be offloaded by two physical switches");
> + return -EBUSY;
> + }
> + /* Be tolerant with drivers that call SWITCHDEV_BRPORT_OFFLOADED
> + * more than once for the same bridge port, such as when the
> + * bridge port is an offloaded bonding/team interface.
> + */
> + p->offload_count++;
> + return 0;
> + }
> +
> + p->ppid = ppid;
> + p->offload_count = 1;
> + p->offload_fwd_mark = br_switchdev_mark_get(p->br, p);
> +
> + return 0;
> +}
> +
> +static void nbp_switchdev_mark_clear(struct net_bridge_port *p,
> + struct netdev_phys_item_id ppid)
> +{
> + if (WARN_ON(!netdev_phys_item_id_same(&p->ppid, &ppid)))
> + return;
> + if (WARN_ON(!p->offload_count))
> + return;
> +
> + p->offload_count--;
> + if (p->offload_count)
> + return;
> +
> + p->offload_fwd_mark = 0;
> +}
> +
> +/* Let the bridge know that this port is offloaded, so that it can use
> + * the port parent id obtained by recursion to determine the bridge
> + * port's switchdev mark.
> + */
> +int switchdev_bridge_port_offload(struct net_device *dev,
> + struct netlink_ext_ack *extack)
> {
> - struct netdev_phys_item_id ppid = { };
> + struct netdev_phys_item_id ppid;
> + struct net_bridge_port *p;
> int err;
>
> - ASSERT_RTNL();
> + p = br_port_get_rtnl(dev);
> + if (!p)
> + return -ENODEV;
>
> - err = dev_get_port_parent_id(p->dev, &ppid, true);
> - if (err) {
> - if (err == -EOPNOTSUPP)
> - return 0;
> + err = dev_get_port_parent_id(dev, &ppid, true);
> + if (err)
> + return err;
> +
> + return nbp_switchdev_mark_set(p, ppid, extack);
> +}
> +EXPORT_SYMBOL_GPL(switchdev_bridge_port_offload);
> +
> +int switchdev_bridge_port_unoffload(struct net_device *dev)
> +{
> + struct netdev_phys_item_id ppid;
> + struct net_bridge_port *p;
> + int err;
> +
Should we ASSERT_RTNL here as well?
> + p = br_port_get_rtnl(dev);
> + if (!p)
> + return -ENODEV;
> +
> + err = dev_get_port_parent_id(dev, &ppid, true);
> + if (err)
> return err;
> - }
>
> - p->offload_fwd_mark = br_switchdev_mark_get(p->br, p->dev);
> + nbp_switchdev_mark_clear(p, ppid);
>
> return 0;
> }
> +EXPORT_SYMBOL_GPL(switchdev_bridge_port_unoffload);
>
> void nbp_switchdev_frame_mark(const struct net_bridge_port *p,
> struct sk_buff *skb)
> --
> 2.25.1
