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    Subject[PATCH v2 net-next 01/10] net: bridge: mst: Multiple Spanning Tree (MST) mode
    Date
    Allow the user to switch from the current per-VLAN STP mode to an MST
    mode.

    Up to this point, per-VLAN STP states where always isolated from each
    other. This is in contrast to the MSTP standard (802.1Q-2018, Clause
    13.5), where VLANs are grouped into MST instances (MSTIs), and the
    state is managed on a per-MSTI level, rather that at the per-VLAN
    level.

    Perhaps due to the prevalence of the standard, many switching ASICs
    are built after the same model. Therefore, add a corresponding MST
    mode to the bridge, which we can later add offloading support for in a
    straight-forward way.

    For now, all VLANs are fixed to MSTI 0, also called the Common
    Spanning Tree (CST). That is, all VLANs will follow the port-global
    state.

    Upcoming changes will make this actually useful by allowing VLANs to
    be mapped to arbitrary MSTIs and allow individual MSTI states to be
    changed.

    Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
    ---
    include/uapi/linux/if_link.h | 1 +
    net/bridge/Makefile | 2 +-
    net/bridge/br_input.c | 17 +++++++-
    net/bridge/br_mst.c | 83 ++++++++++++++++++++++++++++++++++++
    net/bridge/br_netlink.c | 14 +++++-
    net/bridge/br_private.h | 26 +++++++++++
    net/bridge/br_stp.c | 3 ++
    net/bridge/br_vlan.c | 20 ++++++++-
    net/bridge/br_vlan_options.c | 5 +++
    9 files changed, 166 insertions(+), 5 deletions(-)
    create mode 100644 net/bridge/br_mst.c

    diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
    index e315e53125f4..7e0a653aafa3 100644
    --- a/include/uapi/linux/if_link.h
    +++ b/include/uapi/linux/if_link.h
    @@ -482,6 +482,7 @@ enum {
    IFLA_BR_VLAN_STATS_PER_PORT,
    IFLA_BR_MULTI_BOOLOPT,
    IFLA_BR_MCAST_QUERIER_STATE,
    + IFLA_BR_MST_ENABLED,
    __IFLA_BR_MAX,
    };

    diff --git a/net/bridge/Makefile b/net/bridge/Makefile
    index 7fb9a021873b..24bd1c0a9a5a 100644
    --- a/net/bridge/Makefile
    +++ b/net/bridge/Makefile
    @@ -20,7 +20,7 @@ obj-$(CONFIG_BRIDGE_NETFILTER) += br_netfilter.o

    bridge-$(CONFIG_BRIDGE_IGMP_SNOOPING) += br_multicast.o br_mdb.o br_multicast_eht.o

    -bridge-$(CONFIG_BRIDGE_VLAN_FILTERING) += br_vlan.o br_vlan_tunnel.o br_vlan_options.o
    +bridge-$(CONFIG_BRIDGE_VLAN_FILTERING) += br_vlan.o br_vlan_tunnel.o br_vlan_options.o br_mst.o

    bridge-$(CONFIG_NET_SWITCHDEV) += br_switchdev.o

    diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
    index e0c13fcc50ed..196417859c4a 100644
    --- a/net/bridge/br_input.c
    +++ b/net/bridge/br_input.c
    @@ -78,13 +78,22 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
    u16 vid = 0;
    u8 state;

    - if (!p || p->state == BR_STATE_DISABLED)
    + if (!p)
    goto drop;

    br = p->br;
    +
    + if (br_mst_is_enabled(br)) {
    + state = BR_STATE_FORWARDING;
    + } else {
    + if (p->state == BR_STATE_DISABLED)
    + goto drop;
    +
    + state = p->state;
    + }
    +
    brmctx = &p->br->multicast_ctx;
    pmctx = &p->multicast_ctx;
    - state = p->state;
    if (!br_allowed_ingress(p->br, nbp_vlan_group_rcu(p), skb, &vid,
    &state, &vlan))
    goto out;
    @@ -370,9 +379,13 @@ static rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
    return RX_HANDLER_PASS;

    forward:
    + if (br_mst_is_enabled(p->br))
    + goto defer_stp_filtering;
    +
    switch (p->state) {
    case BR_STATE_FORWARDING:
    case BR_STATE_LEARNING:
    +defer_stp_filtering:
    if (ether_addr_equal(p->br->dev->dev_addr, dest))
    skb->pkt_type = PACKET_HOST;

    diff --git a/net/bridge/br_mst.c b/net/bridge/br_mst.c
    new file mode 100644
    index 000000000000..ad6e91670fa8
    --- /dev/null
    +++ b/net/bridge/br_mst.c
    @@ -0,0 +1,83 @@
    +// SPDX-License-Identifier: GPL-2.0-or-later
    +/*
    + * Bridge Multiple Spanning Tree Support
    + *
    + * Authors:
    + * Tobias Waldekranz <tobias@waldekranz.com>
    + */
    +
    +#include <linux/kernel.h>
    +
    +#include "br_private.h"
    +
    +DEFINE_STATIC_KEY_FALSE(br_mst_used);
    +
    +void br_mst_vlan_set_state(struct net_bridge_port *p, struct net_bridge_vlan *v,
    + u8 state)
    +{
    + struct net_bridge_vlan_group *vg = nbp_vlan_group(p);
    +
    + if (v->state == state)
    + return;
    +
    + br_vlan_set_state(v, state);
    +
    + if (v->vid == vg->pvid)
    + br_vlan_set_pvid_state(vg, state);
    +}
    +
    +void br_mst_set_state(struct net_bridge_port *p, u16 msti, u8 state)
    +{
    + struct net_bridge_vlan_group *vg;
    + struct net_bridge_vlan *v;
    +
    + vg = nbp_vlan_group(p);
    + if (!vg)
    + return;
    +
    + list_for_each_entry(v, &vg->vlan_list, vlist) {
    + if (v->brvlan->msti != msti)
    + continue;
    +
    + br_mst_vlan_set_state(p, v, state);
    + }
    +}
    +
    +void br_mst_vlan_init_state(struct net_bridge_vlan *v)
    +{
    + /* VLANs always start out in MSTI 0 (CST) */
    + v->msti = 0;
    +
    + if (br_vlan_is_master(v))
    + v->state = BR_STATE_FORWARDING;
    + else
    + v->state = v->port->state;
    +}
    +
    +int br_mst_set_enabled(struct net_bridge *br, unsigned long val)
    +{
    + struct net_bridge_vlan_group *vg;
    + struct net_bridge_port *p;
    +
    + /* Mode may only be changed when there are no port VLANs. */
    + list_for_each_entry(p, &br->port_list, list) {
    + vg = nbp_vlan_group(p);
    +
    + if (vg->num_vlans)
    + return -EBUSY;
    + }
    +
    + if (val > 1)
    + return -EINVAL;
    +
    + if (!!val == br_opt_get(br, BROPT_MST_ENABLED))
    + return 0;
    +
    + if (val)
    + static_branch_enable(&br_mst_used);
    + else
    + static_branch_disable(&br_mst_used);
    +
    + br_opt_toggle(br, BROPT_MST_ENABLED, !!val);
    + return 0;
    +}
    diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
    index 7d4432ca9a20..a17a0fe25a58 100644
    --- a/net/bridge/br_netlink.c
    +++ b/net/bridge/br_netlink.c
    @@ -1163,6 +1163,7 @@ static const struct nla_policy br_policy[IFLA_BR_MAX + 1] = {
    [IFLA_BR_MCAST_IGMP_VERSION] = { .type = NLA_U8 },
    [IFLA_BR_MCAST_MLD_VERSION] = { .type = NLA_U8 },
    [IFLA_BR_VLAN_STATS_PER_PORT] = { .type = NLA_U8 },
    + [IFLA_BR_MST_ENABLED] = { .type = NLA_U8 },
    [IFLA_BR_MULTI_BOOLOPT] =
    NLA_POLICY_EXACT_LEN(sizeof(struct br_boolopt_multi)),
    };
    @@ -1255,6 +1256,14 @@ static int br_changelink(struct net_device *brdev, struct nlattr *tb[],
    if (err)
    return err;
    }
    +
    + if (data[IFLA_BR_MST_ENABLED]) {
    + __u8 mst = nla_get_u8(data[IFLA_BR_MST_ENABLED]);
    +
    + err = br_mst_set_enabled(br, mst);
    + if (err)
    + return err;
    + }
    #endif

    if (data[IFLA_BR_GROUP_FWD_MASK]) {
    @@ -1475,6 +1484,7 @@ static size_t br_get_size(const struct net_device *brdev)
    nla_total_size(sizeof(u16)) + /* IFLA_BR_VLAN_DEFAULT_PVID */
    nla_total_size(sizeof(u8)) + /* IFLA_BR_VLAN_STATS_ENABLED */
    nla_total_size(sizeof(u8)) + /* IFLA_BR_VLAN_STATS_PER_PORT */
    + nla_total_size(sizeof(u8)) + /* IFLA_BR_MST_ENABLED */
    #endif
    nla_total_size(sizeof(u16)) + /* IFLA_BR_GROUP_FWD_MASK */
    nla_total_size(sizeof(struct ifla_bridge_id)) + /* IFLA_BR_ROOT_ID */
    @@ -1572,7 +1582,9 @@ static int br_fill_info(struct sk_buff *skb, const struct net_device *brdev)
    nla_put_u8(skb, IFLA_BR_VLAN_STATS_ENABLED,
    br_opt_get(br, BROPT_VLAN_STATS_ENABLED)) ||
    nla_put_u8(skb, IFLA_BR_VLAN_STATS_PER_PORT,
    - br_opt_get(br, BROPT_VLAN_STATS_PER_PORT)))
    + br_opt_get(br, BROPT_VLAN_STATS_PER_PORT)) ||
    + nla_put_u8(skb, IFLA_BR_MST_ENABLED,
    + br_opt_get(br, BROPT_MST_ENABLED)))
    return -EMSGSIZE;
    #endif
    #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
    diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
    index 48bc61ebc211..af50ad036b06 100644
    --- a/net/bridge/br_private.h
    +++ b/net/bridge/br_private.h
    @@ -178,6 +178,7 @@ enum {
    * @br_mcast_ctx: if MASTER flag set, this is the global vlan multicast context
    * @port_mcast_ctx: if MASTER flag unset, this is the per-port/vlan multicast
    * context
    + * @msti: if MASTER flag set, this holds the VLANs MST instance
    * @vlist: sorted list of VLAN entries
    * @rcu: used for entry destruction
    *
    @@ -210,6 +211,8 @@ struct net_bridge_vlan {
    struct net_bridge_mcast_port port_mcast_ctx;
    };

    + u16 msti;
    +
    struct list_head vlist;

    struct rcu_head rcu;
    @@ -445,6 +448,7 @@ enum net_bridge_opts {
    BROPT_NO_LL_LEARN,
    BROPT_VLAN_BRIDGE_BINDING,
    BROPT_MCAST_VLAN_SNOOPING_ENABLED,
    + BROPT_MST_ENABLED,
    };

    struct net_bridge {
    @@ -1765,6 +1769,28 @@ static inline bool br_vlan_state_allowed(u8 state, bool learn_allow)
    }
    #endif

    +/* br_mst.c */
    +#ifdef CONFIG_BRIDGE_VLAN_FILTERING
    +DECLARE_STATIC_KEY_FALSE(br_mst_used);
    +static inline bool br_mst_is_enabled(struct net_bridge *br)
    +{
    + return static_branch_unlikely(&br_mst_used) &&
    + br_opt_get(br, BROPT_MST_ENABLED);
    +}
    +
    +void br_mst_set_state(struct net_bridge_port *p, u16 msti, u8 state);
    +void br_mst_vlan_init_state(struct net_bridge_vlan *v);
    +int br_mst_set_enabled(struct net_bridge *br, unsigned long val);
    +#else
    +static inline bool br_mst_is_enabled(struct net_bridge *br)
    +{
    + return false;
    +}
    +
    +static inline void br_mst_set_state(struct net_bridge_port *p,
    + u16 msti, u8 state) {}
    +#endif
    +
    struct nf_br_ops {
    int (*br_dev_xmit_hook)(struct sk_buff *skb);
    };
    diff --git a/net/bridge/br_stp.c b/net/bridge/br_stp.c
    index 1d80f34a139c..82a97a021a57 100644
    --- a/net/bridge/br_stp.c
    +++ b/net/bridge/br_stp.c
    @@ -43,6 +43,9 @@ void br_set_state(struct net_bridge_port *p, unsigned int state)
    return;

    p->state = state;
    + if (br_opt_get(p->br, BROPT_MST_ENABLED))
    + br_mst_set_state(p, 0, state);
    +
    err = switchdev_port_attr_set(p->dev, &attr, NULL);
    if (err && err != -EOPNOTSUPP)
    br_warn(p->br, "error setting offload STP state on port %u(%s)\n",
    diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
    index 7557e90b60e1..0f5e75ccac79 100644
    --- a/net/bridge/br_vlan.c
    +++ b/net/bridge/br_vlan.c
    @@ -226,6 +226,24 @@ static void nbp_vlan_rcu_free(struct rcu_head *rcu)
    kfree(v);
    }

    +static void br_vlan_init_state(struct net_bridge_vlan *v)
    +{
    + struct net_bridge *br;
    +
    + if (br_vlan_is_master(v))
    + br = v->br;
    + else
    + br = v->port->br;
    +
    + if (br_opt_get(br, BROPT_MST_ENABLED)) {
    + br_mst_vlan_init_state(v);
    + return;
    + }
    +
    + v->state = BR_STATE_FORWARDING;
    + v->msti = 0;
    +}
    +
    /* This is the shared VLAN add function which works for both ports and bridge
    * devices. There are four possible calls to this function in terms of the
    * vlan entry type:
    @@ -322,7 +340,7 @@ static int __vlan_add(struct net_bridge_vlan *v, u16 flags,
    }

    /* set the state before publishing */
    - v->state = BR_STATE_FORWARDING;
    + br_vlan_init_state(v);

    err = rhashtable_lookup_insert_fast(&vg->vlan_hash, &v->vnode,
    br_vlan_rht_params);
    diff --git a/net/bridge/br_vlan_options.c b/net/bridge/br_vlan_options.c
    index a6382973b3e7..09112b56e79c 100644
    --- a/net/bridge/br_vlan_options.c
    +++ b/net/bridge/br_vlan_options.c
    @@ -99,6 +99,11 @@ static int br_vlan_modify_state(struct net_bridge_vlan_group *vg,
    return -EBUSY;
    }

    + if (br_opt_get(br, BROPT_MST_ENABLED)) {
    + NL_SET_ERR_MSG_MOD(extack, "Can't modify vlan state directly when MST is enabled");
    + return -EBUSY;
    + }
    +
    if (v->state == state)
    return 0;

    --
    2.25.1
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