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Date: Thu, 13 Jul 2023 12:33:19 +0300
From: Nikolay Aleksandrov <razor@...ckwall.org>
To: Ido Schimmel <idosch@...dia.com>, netdev@...r.kernel.org,
bridge@...ts.linux-foundation.org
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
edumazet@...gle.com, roopa@...dia.com, dsahern@...il.com, petrm@...dia.com,
taspelund@...dia.com
Subject: Re: [RFC PATCH net-next 3/4] bridge: Add backup nexthop ID support
On 13/07/2023 10:09, Ido Schimmel wrote:
> Add a new bridge port attribute that allows attaching a nexthop object
> ID to an skb that is redirected to a backup bridge port with VLAN
> tunneling enabled.
>
> Specifically, when redirecting a known unicast packet, read the backup
> nexthop ID from the bridge port that lost its carrier and set it in the
> bridge control block of the skb before forwarding it via the backup
> port. Note that reading the ID from the bridge port should not result in
> a cache miss as the ID is added next to the 'backup_port' field that was
> already accessed. After this change, the 'state' field still stays on
> the first cache line, together with other data path related fields such
> as 'flags and 'vlgrp':
>
> struct net_bridge_port {
> struct net_bridge * br; /* 0 8 */
> struct net_device * dev; /* 8 8 */
> netdevice_tracker dev_tracker; /* 16 0 */
> struct list_head list; /* 16 16 */
> long unsigned int flags; /* 32 8 */
> struct net_bridge_vlan_group * vlgrp; /* 40 8 */
> struct net_bridge_port * backup_port; /* 48 8 */
> u32 backup_nhid; /* 56 4 */
> u8 priority; /* 60 1 */
> u8 state; /* 61 1 */
> u16 port_no; /* 62 2 */
> /* --- cacheline 1 boundary (64 bytes) --- */
> [...]
> } __attribute__((__aligned__(8)));
>
> When forwarding an skb via a bridge port that has VLAN tunneling
> enabled, check if the backup nexthop ID stored in the bridge control
> block is valid (i.e., not zero). If so, instead of attaching the
> pre-allocated metadata (that only has the tunnel key set), allocate a
> new metadata, set both the tunnel key and the nexthop object ID and
> attach it to the skb.
>
> By default, do not dump the new attribute to user space as a value of
> zero is an invalid nexthop object ID.
>
> The above is useful for EVPN multihoming. When one of the links
> composing an Ethernet Segment (ES) fails, traffic needs to be redirected
> towards the host via one of the other ES peers. For example, if a host
> is multihomed to three different VTEPs, the backup port of each ES link
> needs to be set to the VXLAN device and the backup nexthop ID needs to
> point to an FDB nexthop group that includes the IP addresses of the
> other two VTEPs. The VXLAN driver will extract the ID from the metadata
> of the redirected skb, calculate its flow hash and forward it towards
> one of the other VTEPs. If the ID does not exist, or represents an
> invalid nexthop object, the VXLAN driver will drop the skb. This
> relieves the bridge driver from the need to validate the ID.
>
> Signed-off-by: Ido Schimmel <idosch@...dia.com>
> ---
> include/uapi/linux/if_link.h | 1 +
> net/bridge/br_forward.c | 1 +
> net/bridge/br_netlink.c | 12 ++++++++++++
> net/bridge/br_private.h | 3 +++
> net/bridge/br_vlan_tunnel.c | 15 +++++++++++++++
> net/core/rtnetlink.c | 2 +-
> 6 files changed, 33 insertions(+), 1 deletion(-)
>
One comment below, with that fixed you can add
Acked-by: Nikolay Aleksandrov <razor@...ckwall.org>
> diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
> index 0f6a0fe09bdb..ce3117df9cec 100644
> --- a/include/uapi/linux/if_link.h
> +++ b/include/uapi/linux/if_link.h
> @@ -570,6 +570,7 @@ enum {
> IFLA_BRPORT_MCAST_N_GROUPS,
> IFLA_BRPORT_MCAST_MAX_GROUPS,
> IFLA_BRPORT_NEIGH_VLAN_SUPPRESS,
> + IFLA_BRPORT_BACKUP_NHID,
> __IFLA_BRPORT_MAX
> };
> #define IFLA_BRPORT_MAX (__IFLA_BRPORT_MAX - 1)
> diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c
> index 6116eba1bd89..9d7bc8b96b53 100644
> --- a/net/bridge/br_forward.c
> +++ b/net/bridge/br_forward.c
> @@ -154,6 +154,7 @@ void br_forward(const struct net_bridge_port *to,
> backup_port = rcu_dereference(to->backup_port);
> if (unlikely(!backup_port))
> goto out;
> + BR_INPUT_SKB_CB(skb)->backup_nhid = READ_ONCE(to->backup_nhid);
> to = backup_port;
> }
>
> diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
> index 05c5863d2e20..10f0d33d8ccf 100644
> --- a/net/bridge/br_netlink.c
> +++ b/net/bridge/br_netlink.c
> @@ -211,6 +211,7 @@ static inline size_t br_port_info_size(void)
> + nla_total_size(sizeof(u8)) /* IFLA_BRPORT_MRP_IN_OPEN */
> + nla_total_size(sizeof(u32)) /* IFLA_BRPORT_MCAST_EHT_HOSTS_LIMIT */
> + nla_total_size(sizeof(u32)) /* IFLA_BRPORT_MCAST_EHT_HOSTS_CNT */
> + + nla_total_size(sizeof(u32)) /* IFLA_BRPORT_BACKUP_NHID */
> + 0;
> }
>
> @@ -319,6 +320,10 @@ static int br_port_fill_attrs(struct sk_buff *skb,
> backup_p->dev->ifindex);
> rcu_read_unlock();
>
> + if (p->backup_nhid &&
> + nla_put_u32(skb, IFLA_BRPORT_BACKUP_NHID, p->backup_nhid))
> + return -EMSGSIZE;
> +
READ_ONCE(), see the comment above backup_port :)
> return 0;
> }
>
> @@ -895,6 +900,7 @@ static const struct nla_policy br_port_policy[IFLA_BRPORT_MAX + 1] = {
> [IFLA_BRPORT_MCAST_N_GROUPS] = { .type = NLA_REJECT },
> [IFLA_BRPORT_MCAST_MAX_GROUPS] = { .type = NLA_U32 },
> [IFLA_BRPORT_NEIGH_VLAN_SUPPRESS] = NLA_POLICY_MAX(NLA_U8, 1),
> + [IFLA_BRPORT_BACKUP_NHID] = { .type = NLA_U32 },
> };
>
> /* Change the state of the port and notify spanning tree */
> @@ -1065,6 +1071,12 @@ static int br_setport(struct net_bridge_port *p, struct nlattr *tb[],
> return err;
> }
>
> + if (tb[IFLA_BRPORT_BACKUP_NHID]) {
> + u32 backup_nhid = nla_get_u32(tb[IFLA_BRPORT_BACKUP_NHID]);
> +
> + WRITE_ONCE(p->backup_nhid, backup_nhid);
> + }
> +
> return 0;
> }
>
> diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
> index a63b32c1638e..05a965ef76f1 100644
> --- a/net/bridge/br_private.h
> +++ b/net/bridge/br_private.h
> @@ -387,6 +387,7 @@ struct net_bridge_port {
> struct net_bridge_vlan_group __rcu *vlgrp;
> #endif
> struct net_bridge_port __rcu *backup_port;
> + u32 backup_nhid;
>
> /* STP */
> u8 priority;
> @@ -605,6 +606,8 @@ struct br_input_skb_cb {
> */
> unsigned long fwd_hwdoms;
> #endif
> +
> + u32 backup_nhid;
> };
>
> #define BR_INPUT_SKB_CB(__skb) ((struct br_input_skb_cb *)(__skb)->cb)
> diff --git a/net/bridge/br_vlan_tunnel.c b/net/bridge/br_vlan_tunnel.c
> index 6399a8a69d07..81833ca7a2c7 100644
> --- a/net/bridge/br_vlan_tunnel.c
> +++ b/net/bridge/br_vlan_tunnel.c
> @@ -201,6 +201,21 @@ int br_handle_egress_vlan_tunnel(struct sk_buff *skb,
> if (err)
> return err;
>
> + if (BR_INPUT_SKB_CB(skb)->backup_nhid) {
> + tunnel_dst = __ip_tun_set_dst(0, 0, 0, 0, 0, TUNNEL_KEY,
> + tunnel_id, 0);
> + if (!tunnel_dst)
> + return -ENOMEM;
> +
> + tunnel_dst->u.tun_info.mode |= IP_TUNNEL_INFO_TX |
> + IP_TUNNEL_INFO_BRIDGE;
> + tunnel_dst->u.tun_info.key.nhid =
> + BR_INPUT_SKB_CB(skb)->backup_nhid;
> + skb_dst_set(skb, &tunnel_dst->dst);
> +
> + return 0;
> + }
> +
> tunnel_dst = rcu_dereference(vlan->tinfo.tunnel_dst);
> if (tunnel_dst && dst_hold_safe(&tunnel_dst->dst))
> skb_dst_set(skb, &tunnel_dst->dst);
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index 3ad4e030846d..9e7e3377ec10 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -61,7 +61,7 @@
> #include "dev.h"
>
> #define RTNL_MAX_TYPE 50
> -#define RTNL_SLAVE_MAX_TYPE 43
> +#define RTNL_SLAVE_MAX_TYPE 44
>
> struct rtnl_link {
> rtnl_doit_func doit;
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